Impacted Teeth

Ness, Gregory M.; Blakey, George H.; Hechler, Ben L.

doi:10.1007/978-3-030-91920-7_5

Gregory M. Ness⁵,
George H. Blakey⁶ &
Ben L. Hechler⁷

4736 Accesses
4 Citations

Abstract

Evaluation and management of impacted teeth are among the most frequent services offered by oral and maxillofacial surgeons. Although the third molar is the most commonly impacted tooth, any other tooth may be impacted if space for its eruption is compromised. For third molars, the most common removal indications are periodontitis, pericoronitis, and caries. Patient age, general health, and unusual local risk factors must be considered and may contraindicate surgery. Non-third molar teeth may be exposed and orthodontically brought into occlusion or removed if necessary. Observing well-established principles for surgical technique and perioperative care minimizes complications.

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Management of Impacted Teeth

Dental Extractions

Unerupted and Impacted Teeth: A Guide for Assessment and Treatment

Keywords

FormalPara Learning Aims

Discriminate between unerupted and impacted teeth.
Understand the natural history of impacted teeth and the most likely consequences of their retention in various clinical circumstances.
Describe basic principles of impacted third molar management for a variety of clinical presentations.
Recognize and manage common and infrequent perioperative complications of impacted tooth removal.

FormalPara Introduction

Evaluation and management of impacted teeth are among the most frequent services offered by oral and maxillofacial surgeons. Although the mandibular third molar is the most commonly impacted tooth, any other tooth may be impacted. Extensive training, skill, and experience are necessary to treat these conditions with minimal trauma: when the surgeon is untrained and/or inexperienced, the incidence of complications rises significantly [1,2,3]. Determining the need for removal of asymptomatic teeth may also be problematic. Contemporary medical and dental practice demands evidence-based decision-making and the surgeon is increasingly called upon to justify surgical procedures, including the removal of impacted teeth, by scientific data. In many situations this decision is clear-cut based on available scientific data; in others the decision remains based on clinical experience and professional judgment. This chapter reviews and discusses the etiology of impacted teeth, indications and contraindications for their exposure or removal, impaction classification and determination of the degree of difficulty of surgery, parameters of perioperative patient care, and the likely complications and their management following third molar surgery.

FormalPara Importance

Impacted teeth are among the most common dental findings in adolescents and young adults, and oral and maxillofacial surgeons must be exhaustively familiar with their diagnosis and management.
Because impacted teeth are common, evidence-based treatment planning is an important responsibility with significant impact on healthcare costs.
Minimizing risks from either removal or retention of impacted teeth and effectively managing complications when they occur are major roles for the oral and maxillofacial surgeon in contemporary practice.

FormalPara Impacted Versus Unerupted Teeth

Not all unerupted teeth are impacted. A tooth is considered impacted when it has failed to fully erupt into the oral cavity within its expected developmental time period and can no longer reasonably be expected to do so. Consequently, diagnosing an impaction demands a clear understanding of the usual chronology of eruption, as well as the factors that influence eruption potential.

Not all unerupted teeth are impacted.
Impaction is diagnosed when a tooth is unlikely to erupt.
Eruption potential, and therefore the diagnosis of impaction, may require clinical judgment.

1 Incidence and Etiology

The incidence of impacted permanent teeth has been addressed in several studies with comparable findings. Generally speaking, the order of impaction frequency is the reverse of eruption order. Maxillary and mandibular third molars are the most likely teeth to become impacted, followed by maxillary canines, mandibular premolars, maxillary premolars, and second molars. Impaction of first molars or incisors is uncommon in both arches [4,5,6,7]. True impaction of deciduous teeth, as opposed to ankylosis and subsequent submersion, or defects in permanent successor tooth eruption, is exceedingly rare [8, 9].

1.1 Impactions Other than Third Molars

A number of large-scale epidemiological studies have examined the incidence of dental impactions. Grover and Lorton examined 5000 army recruits and found a high frequency of impacted teeth (◘ Fig. 5.1) [4]. Although maxillary and mandibular third molars were the teeth most commonly impacted, 212 other impacted teeth were found. Among these teeth maxillary canines were the most common, although impactions of every permanent tooth were identified except mandibular incisors and first molars. Thilander and Myrberg examined more than 6000 Swedish schoolchildren and found a 5.4% prevalence of non-third molar impacted teeth [5]. In an evaluation of 3874 full-mouth radiographs, Dachi and Howell found the incidence of impacted canines in the maxilla to be 0.92% and of other non-third molar teeth to be 0.38% [6]. And in a study of middle-aged and older Swedish women, Grondahl found approximately 25 non-third molar impacted teeth in 1418 women evaluated [7]. Again, the canine tooth was the most frequent non-third molar impaction identified, followed by premolars and second molars. The incidence of impaction was lower in this study of older patients, presumably because symptomatic teeth and those with pathologic findings were removed earlier in life (◘ Fig. 5.2).

Permanent teeth may become impacted because of systemic or local factors. Impaction of teeth in the hereditary syndrome of cleidocranial dysplasia (◘ Fig. 5.3) is more properly termed primary retention [10]. Endocrine deficiencies (hypothyroidism and hypopituitarism), febrile diseases, Down syndrome, and irradiation are other systemic factors that may influence impaction of permanent teeth [11, 12]. Multiple teeth are often involved in these conditions.

More commonly, local factors are the cause of permanent tooth impaction. These factors include prolonged deciduous tooth retention, malposed tooth germs, arch-length deficiency, supernumerary teeth, odontogenic tumors, abnormal eruption path, and cleft lip and palate [10, 13, 14].

Because maxillary canines are impacted relatively often, they have been studied extensively in an effort to identify the causes of impaction. Usually they are displaced to either the palatal or labial side of the alveolus, and Jacoby distinguishes between these positions in his conclusions on impaction’s etiology [13]. Labially unerupted canines tend to show a degree of arch-length deficiency, whereas palatally impacted canines do not. He stated that a canine might appear in a palatal position if extra space is available in the maxillary bone owing to either excessive growth, agenesis or peg shape of the lateral incisor, or stimulated eruption of a lateral incisor or first premolar [13]. In his review of impacted maxillary canines, Bishara echoes this theory, stating that the presence of the lateral incisor root with normal length at the normal time is important to guide the canine in a proper eruptive direction [11]. There is also a documented association between various sella turcica measurements and interclinoidal calcification (called “sella bridging”) and palatally impacted maxillary canines, although an exact mechanism has not been elucidated, and there are many other radiographic findings more proximate in the dental arch that are more strongly associated with canine impactions [15].

Impacted second molars have also been studied to determine the cause of these impactions. Although maxillary second permanent molars are infrequently impacted, in a study of these cases Ranta found that the third molar was generally positioned occlusally and palatally in relation to the second molar, acting as an obstruction (◘ Fig. 5.4) [16]. In a similar study, Levy and Regan identified the most probable cause of impaction of developing maxillary second molars as malposition of the tooth germs of the third molars [12]. A typical finding in their series of cases was deformation of the mesial surfaces of the crowns and roots of the third molars. Raghoebar and colleagues stated that impaction of first molars is often diagnosed as ectopic eruption, whereas impaction of second molars is usually associated with arch-length deficiency [10]. Other studies have found association of impaction with inadequate space as high as 90% [17]. However, a more recent study by Bondemark and Tsiopa [18] examined impacted second molars including those which were erupted but not completely, having stopped short of the occlusal plane. Among impacted teeth in this population, 75% had no clinically or radiographically apparent physical barrier to eruption, indicating that inadequate space is only one potential etiology of this condition. None of the teeth with disturbed eruption this study were associated with pathologic conditions such as cysts, tumors, ankylosis, or jaw hypoplasia/dysplasia associated with syndromes, all of which may cause dental impactions. Indeed, many of these cases likely represent either ectopic position of the follicle or an intrinsic aberrancy in and failure of the eruption mechanism [19].

1.2 Impacted Third Molars

The age range when the third molars, the final teeth to erupt, may appear is broader than other teeth. While eruption of lower third molars is often complete at the average age of 20 years, it can occur as late as age 24 years. A tooth that appears impacted at age 18 years may have as much as a 30–50% chance of erupting fully by age 25 years, according to several longitudinal studies [20,21,22]. It is fairly well established that the position of retained third molars does not change substantially after age 25 years [14], although there is some evidence of continued movement as late as the fourth decade [20]. Many patients are evaluated for third molar removal in their mid to late teens, and the surgeon must therefore attempt to discern the probable outcome of the eruption process based on more than tooth position alone.

A number of longitudinal studies have clearly defined the development and eruption pattern of the third molar [24,25,26,27]. The mandibular third molar tooth germ is usually visible radiographically by age 9 years, and cusp mineralization is completed approximately 2 years later. At age 11 years, the tooth is located within the anterior border of the ramus with its occlusal surface facing almost directly anteriorly. The level of the tooth germ is approximately at the occlusal plane of the erupted dentition. Crown formation is usually complete by age 14 years, and the roots are approximately 50% formed by age 16 years. During this time the body of the mandible grows in length at the expense of resorption of the anterior border of the ramus. As this process occurs the position of the third molar relative to the adjacent teeth changes, with the third molar assuming a position at approximately the root level of the adjacent second molar. The angulation of the crown becomes more horizontal also. Usually the roots are completely formed with an open apex by age 18 years.

The change in orientation of the occlusal surface from a straight anterior orientation to a straight vertical inclination occurs primarily during root formation. During this time the tooth rotates from horizontal to mesioangular to vertical. Therefore, the normal development and eruption pattern, assuming the tooth has sufficient room to erupt, brings the tooth into its final position by age 20 years. By age 24 years, 95% of all third molars that will erupt have completed their eruption.

Most third molars do not complete this eruption sequence and, instead, become impacted teeth. Approximately half do not assume the vertical position and remain as mesioangular impactions. There are several possible explanations for this. The Belfast Study Group suggested that there may be differential root growth between the mesial and distal roots, which causes the tooth to either remain mesially inclined or rotate to a vertical position depending on the amount of root development [27, 28]. In their studies they found that underdevelopment of the mesial root results in a mesioangular impaction. Overdevelopment of the same root results in over-rotation of the third molar into a distoangular impaction. Overdevelopment of the distal root, commonly with a mesial curve, is responsible for severe mesioangular or horizontal impaction. They go on to note that whereas the expected normal rotation is from horizontal to mesioangular to vertical, failure of rotation from the mesioangular to the vertical position is also common. To a lesser extent, they documented worsening of the angulation from mesioangular to horizontal impaction and over-rotation from mesioangular to distoangular. These over-rotations from mesioangular to horizontal and from mesioangular to distoangular occur during the terminal portion of root development.

A second major reason for the failure of the third molar to rotate into a vertical position and erupt involves the relation of the bony arch length to the sum of the mesiodistal widths of the teeth in the arch. Several studies have demonstrated that when bony length is inadequate, a higher proportion of impacted teeth is seen [26, 29, 30]. In general, patients with impacted teeth almost invariably have larger-sized teeth than do those without impactions [30]. Even when the tooth-bone relationship is favorable, a lower third molar that is abnormally positioned laterally almost always fails to erupt [26], perhaps influenced in part by the dense bone present in the external oblique ridge.

A final factor that seems to be associated with an increased incidence of third molar impaction is retarded maturation. When dental development of the tooth lags behind the skeletal growth and maturation of the jaws, there is an increased incidence of impaction. This is most likely a result of a decreased influence of the tooth on the growth pattern and resorption of the mandible. This phenomenon results in the rather counterintuitive observation that by age 20 years, an impacted third molar with partially developed roots is less likely to erupt than a similarly positioned tooth with fully developed roots.

2 Clinical Evaluation

Diagnosis of impacted permanent teeth is straightforward, involving clinical inspection that discloses the absence of the tooth in its normal position combined with the radiographic assessment showing the position of the unerupted tooth. When multiple or uncommonly impacted teeth are found to be impacted, the surgeon should evaluate for an underlying systemic cause.

Radiographic assessment of the impacted teeth is important in the preparation for surgical or orthodontic treatment. The optimal age for evaluating an ectopically positioned canine has been suggested to be 10–13 years, depending on individual development [31]. Most techniques for localization of an impacted tooth have been studied primarily with maxillary canines, but these can be generalized to other sites in the oral cavity. Ericson and Kurol have studied the radiographic appearance of ectopically erupting maxillary canines and have found that a palpable canine generally erupts in a relatively normal position, and that axial or panoramic films were less useful than conventional periapical radiographs [32]. A study comparing plain film radiography with computed tomography (CT) showed CT to be superior in showing tooth and root shape, crown-root relationship, and tooth inclination [33]. The growing availability of in-office cone beam CT (CBCT) imaging makes this an increasingly important diagnostic adjunct, particularly in difficult cases. It should be noted, however, that studies have consistently shown that evaluation of third molar and inferior alveolar canal proximity by CBCT does not regularly translate into decreased rates of long-term paresthesia as compared to panoramic imaging alone [34,35,36,37]. It is therefore unnecessary to routinely request CBCT imaging prior to extraction of third molars, where the surgical approach is always from the facial aspect of the mandible. Use of three-dimensional imaging is, however, quite beneficial in cases of other tooth impactions where an approach from the palatal or lingual aspect may be found to be more conservative.

Standard radiographic techniques to establish three-dimensional tooth location include the tube shift method, buccal object rule, and periapical occlusal method [38]. All of these methods make use of what is commonly known as the SLOB principle, for Same-Lingual, Opposite-Buccal. The tube shift method uses two periapical radiographs, shifting the tube horizontally between exposures. If the unerupted tooth moves in the same direction as the tube was shifted, it is localized on the lingual or palatal side. A facial or buccally located tooth moves in the opposite direction to the tube shift. The buccal object rule uses two radiographs taken with different vertical angulations of the x-ray beam, with the same results. The periapical occlusal method uses the periapical radiograph taken with a standard technique and an occlusal radiograph to give two different views of the impacted tooth (◘ Fig. 5.5).

Numerous studies have evaluated the influence of various factors on the eruption potential of a lower third molar. Two radiographically determined factors consistently emerge as most prognostic: angulation of the third molar and space available for its emergence [39,40,41,42,43]. By age 18–20 years, lower third molars that are horizontal or strongly mesioangular have much less eruption potential than do those that are oriented more vertically. Distoangular teeth are intermediate in their likelihood to erupt fully. However, the strongest hope of future eruption lies with those third molars that can be seen radiographically to have space at least as wide as their crown between the distal of the second molar and the ascending mandibular ramus. At age 20 years, unerupted lower third molars that are nearly vertical and have adequate horizontal space are more likely to erupt than to remain impacted. However, if the crown-to-space ratio is greater than 1, or if the tooth orientation diverges substantially from vertical, the tooth is unlikely to ever erupt fully.

Key Points

Any tooth may be impacted.
Third molars are the most common impacted teeth, followed by maxillary canines.
The major influence on third molar impaction is space for eruption.
Maxillary canine impaction may be influenced by available space or lateral incisor root development.

3 Treatment of an Impacted Tooth

An impacted tooth can cause the patient mild to serious problems if it remains in the unerupted state. Not every impacted tooth causes a problem of clinical significance, but each does have that potential. A body of information has been collected based on extensive clinical experience and clinical studies from which indications for removal of impacted teeth have been developed. For some indications, there is lack of evidence-based data gained from long-term prospective longitudinal studies.

For many—if not most—non-third molar impactions, the most desirable treatment outcome is eruption of the tooth into its normal, functional position in the dental arch. This is generally accomplished through a combination of orthodontic and surgical treatment, with close consultation between specialists determining the timing and sequencing of treatment steps. For teeth whose eruption potential is poor, where space cannot be created to accommodate them, or which have associated pathological lesions, and for nearly all third molars, treatment will include removal of the impacted tooth. There is extensive discussion of the strength of evidence supporting removal of impacted third molars, and the contemporary oral and maxillofacial surgeon must be closely familiar with the current literature on this topic. Along these lines, it should be noted that longitudinal data has now been collected for over two decades in what has been termed the Third Molar Clinical Trials, which collectively help to guide third molar management [44, 45]. It is sobering that despite this large-scale effort, the most recent Cochrane Database systematic review on removal of asymptomatic third molars includes only two articles and was unable to draw definitive conclusions [46].

3.1 Indications for Removal of Impacted Third Molars

Most clinicians agree that if a patient presents with one or more of the pathologic problems or symptoms described below, the involved third molar should be removed. It is much less clear what should be done prophylactically with third molars that are impacted but have not yet caused these problems. Most of the symptomatic pathologic problems that result from third molars occur as a result of a partially erupted tooth. There is a lower incidence of problems associated with a complete bony impaction.

3.1.1 Periodontitis

Perhaps the most important and complete new knowledge regarding the retained third molar is its influence on initiation and progression of periodontal disease. The potential for partially erupted third molars to contribute to early advanced periodontitis has been recognized for many years, and was the primary reason for removal of approximately 5% of impacted third molars in studies from the 1980s [23, 47,48,49,50]. More recent evidence demonstrates that even young patients in otherwise good general periodontal health have a significant increase in periodontal pocketing, attachment loss, pathogenic bacterial activity, and inflammatory markers at the distal of the second molar and around the third molar [51,52,53]. Periodontal probing depths distal to the second molar of 5 mm or more are twice as likely in the presence of a visible third molar [54]. Young patients with visible third molars are significantly more likely to have moderate to severe periodontal disease [55]. Furthermore, retained visible third molars are associated with progressively deepening periodontal pockets over time [56], particularly in the common presence of pathogenic periodontal microflora [57] (“red” complex bacteria) as described originally by Socransky [58, 59]. This is observed even when the third molar continues to erupt to the level of the mandibular occlusal plane [56]. Periodontal pocketing worsens not only in the third molar area, but in adjacent teeth as well [60]. Finally, dental prophylaxis is less effective at lowering periodontal pathogen counts in patients with visible third molars present [61].

This evidence points strongly to the impacted third molar’s important role in the onset, severity, and progression of periodontitis in otherwise young and healthy patients. Removal of these impacted teeth before the age of 25 years usually results in improved periodontal attachment at the distal of the second molar [62,63,64] and reduces the incidence of periodontal pockets of 4 mm or more in other teeth as well [65]. Current knowledge of the biology of periodontal pathology, applied to the third molar, makes obsolete the concept that third molar “pseudopocketing” is a benign phenomenon [66].

3.1.2 Pericoronitis

When a third molar, usually the mandibular third molar, partially erupts through the oral mucosa, the potential for the establishment of a mild to moderate inflammatory response similar to gingivitis and periodontitis exists. The bacteria that are most commonly associated with pericoronitis are Peptostreptococcus, Fusobacterium, and Porphyromonas [67,68,69]. Traditional teaching has revolved around initial treatment aimed at debridement of the periodontal pocket by irrigation or by mechanical means, disinfection of the pocket with an irrigation solution such as hydrogen peroxide or chlorhexidine, and surgical management by extraction of the opposing maxillary third molar. Unfortunately, many dental schools and texts continue to propagate a misleading mentality first presented in an article published in the Journal of the American Dental Association in 1937: that extraction of a tooth in the setting of surrounding pericoronitis or operculitis is more detrimental than no surgical treatment. This mindset is flawed, and a partially impacted third molar resulting in surrounding hard or soft tissue infection should be removed as soon as possible [70].

Prevention of recurrent pericoronitis is usually achieved by removal of the involved mandibular third molar. Approximately 25–30% of impacted mandibular third molars are extracted because of pericoronitis or recurrent pericoronitis [23, 47,48,49,50]. Pericoronitis is the most common reason for removal of impacted third molars after age 20 years. With increasing age, the incidence of pericoronitis as an indication for removal of impacted teeth also increases.

Dental Caries: Dental caries can occur in the mandibular third molar or in the adjacent second molar, most commonly at the cervical line. Owing to the patient’s inability to effectively clean this area and because the third molar is inaccessible to the restorative dentist, caries in the second and third molars are responsible for extraction of impacted third molars in approximately 15% of patients [23, 47,48,49,50]. Occlusal caries in the partially erupted third molar are common but not as likely as periodontal pathology [66]. As with pericoronitis, the presence of caries and eventual pulpal necrosis are responsible for an increasing percentage of extractions with age.

3.1.3 Orthodontic Considerations

The presence of the impacted third molar, especially in the mandible, may be responsible for several orthodontic problems. These problems fall into three general areas, which are outlined below.

Crowding of Mandibular Incisors: Perhaps one of the most controversial issues regarding mandibular third molars in the past was the issue of their influence on anterior crowding of mandibular incisor teeth, especially after orthodontic therapy. More recent literature includes longitudinal reviews of orthodontically treated patients in larger numbers [71, 72], and the preponderance of evidence now suggests that impacted third molars are not a significant cause of post-orthodontic anterior crowding. In fact, anterior incisor crowding is associated with deficient arch length, not the presence of impacted teeth. Nevertheless, the clinician should expect to see patients who indicate they were referred for third molar extraction given dental crowding. It is the oral and maxillofacial surgeon’s responsibility to inform patients that extraction will not improve this condition.

Obstruction of Orthodontic Treatment: In some situations the orthodontist attempts to move the molar teeth distally, but the presence of an impacted third molar may inhibit or even prevent this procedure. Therefore, if the orthodontist is attempting to move the buccal segments posteriorly, removal of the impacted third molar may facilitate treatment and allow predictable outcomes.

Interference with Orthognathic Surgery: When maxillary or mandibular osteotomies are planned, presurgical removal of the impacted teeth may facilitate the orthognathic procedure. Delaying removal of third molars until mandibular osteotomy, especially in mandibular advancement surgery, substantially reduces the thickness and quality of lingual bone at the proximal aspect of the distal segment, where fixation screws are usually applied. That being said, there is good evidence to suggest that outcomes and morbidity are identical when sagittal split osteotomies are performed with or without the presence of an impacted third molar [73,74,75]. It appears, therefore, that either approach is reasonable. If third molars are to be removed in advance, sufficient time must be allowed for the extraction site to fill with mature bone. On the other hand, following maxillary down-fracture a deeply impacted upper third molar is often easily approached from above through the maxillary sinus and may be safely removed in this manner without compromising the soft tissue vascular pedicle of the maxilla. Although these circumstances involve a small percentage of all impacted third molars, the surgeon must plan well in advance (6–12 months) for patients undergoing these procedures.

3.1.4 Prevention of Odontogenic Cysts and Tumors

In the impacted third molar that is left intact in the jaw, the follicular sac that was responsible for the formation of the crown may undergo cystic degeneration and form a dentigerous cyst. The follicular sac may also develop an odontogenic tumor or, in quite rare cases, a malignancy. These possibilities have frequently been cited as a reason for removal of asymptomatic teeth; although rare, when pathology occurs, it may pose a serious health threat [76]. The general incidence of neoplastic change around impacted molars has been estimated to be about 3% [77, 78]. In retrospective surveys of large numbers of patients, between 1% and 2% of all third molars that are extracted are removed because of the presence of odontogenic cysts and tumors [23, 47,48,49,50]. These pathologic entities are usually seen in patients under age 40 years, suggesting that the risk of neoplastic change around impacted third molars may decrease with age.

3.1.5 Root Resorption of Adjacent Teeth

Third molars in the process of eruption may cause root resorption of adjacent teeth. The general view is that misaligned erupting teeth may resorb the roots of adjacent teeth, just as succedaneous teeth resorb the roots of primary teeth during their normal eruption sequence. The actual occurrence of significant root resorption of adjacent teeth is not clear, although it may be as high as 7% [79]. If root resorption is noted on adjacent teeth, the surgeon should consider removing the third molar as soon as it is convenient. In most cases the adjacent tooth repairs itself with the deposition of a layer of cementum over the resorbed area and the formation of secondary dentin. However, if resorption is severe both teeth may require removal.

3.1.6 Teeth Under Dental Prostheses

Before construction of a removable or fixed prosthesis, the dentist should make sure that there are no impacted teeth in the edentulous area that is being restored. If such teeth are present, the general recommendation is that they be removed before the final placement of the prosthesis. Teeth that are completely covered with bone, that show no pathologic changes, and that are in patients more than 40 years old are unlikely to develop problems on their own. However, if a removable tissue-borne prosthesis is to be constructed on a ridge where an impacted tooth is covered by only soft tissue or 1 or 2 mm of bone, it is highly likely that in time the overlying bone will be resorbed, the mucosa will perforate, and the area will become painful and often inflamed. If this occurs, the impacted tooth will likely then need to be removed and the dental prosthesis either altered or refabricated.

The risks and benefits of removing the impacted tooth must be given careful individual consideration. In older patients with tooth- or implant-borne fixed prostheses, asymptomatic deeply impacted teeth can be safely left in place. However, if a removable prosthesis is to be made and the bone overlying the impacted tooth is thin, the tooth should probably be removed before the final prosthesis is constructed. In these older patients with high-risk extractions, coronectomy can be considered, as described later in the chapter.

3.1.7 Prevention of Jaw Fracture

Patients who engage in contact sports, such as football, rugby, or martial arts, should consider having their impacted third molars removed to prevent jaw fracture during competition. An impacted third molar presents an area of lowered resistance to fracture in the mandible and is therefore a common site for fracture [80,81,82]. Additionally, the presence of an impacted third molar in the line of fracture may cause increased complications in the treatment of the fracture.

3.1.8 Management of Unexplained Pain

Occasionally patients complain of jaw pain in the area of an impacted third molar that has neither clinical nor radiographic signs of pathology, and other sources of pain are ruled out. In these situations removal of the impacted third molar frequently results in resolution of this pain. At this time there is no plausible explanation as to why this relief of pain occurs. Approximately 1–2% of mandibular third molars that are extracted are removed for this reason [ 23, 47,48,49,50]. The patient must be informed that removal of the third molar may not relieve the pain completely.

3.2 Contradictions to Treatment of Impacted Teeth

The decision to remove a given impacted tooth must be based on a careful evaluation of the potential benefits versus risks. In situations in which pathology exists, the decision to remove the tooth is uncomplicated because it is necessary to treat the disease process. Likewise, there are situations in which removal of impacted teeth is contraindicated because the surgical complications and sequelae outweigh the potential benefits. The general contraindications for removal of impacted teeth can be grouped into three primary areas: advanced patient age, poor health, and surgical damage to adjacent structures [83].

3.2.1 Extremes of Age

Healing generally occurs more rapidly and more completely in younger patients; however, surgical removal of unerupted third molars in the very young is contraindicated. Historically, some clinicians reported that removal of the tooth bud of the developing third molar at age 8 or 9 years can be accomplished with minimal surgical morbidity [84]. However, the contemporary consensus is that this is not a prudent approach. The original view was based on the belief that accurate growth predictions could be made and, therefore, that an accurate determination could be established regarding whether a given tooth would be impacted. If such a determination were the case, then the tooth bud could be removed relatively atraumatically in the very young patient. The evidence at this time, however, is contradictory to that opinion, and the general consensus is that removal of the tooth bud at this stage may, in fact, be unnecessary because the involved third molar may erupt into proper position. If a young patient is already undergoing an oral surgical procedure under anesthesia, however, consideration may be made to prophylactic extraction of third molars.

At the other end of the age spectrum, with increasing age, healing response decreases [85], which may result in a greater bony defect postoperatively than was present because of the impacted tooth. Additionally, the surgical procedure grows more and more difficult as the patient ages owing to more densely calcified bone, which is less flexible and more likely to fracture. It is therefore not surprising that older individuals have been shown to be seven times more likely to experience complications after third molar removal [86]. These age-related bony changes also alter the relative surrounding soft tissue anatomy: as posterior mandibular bone resorbs in edentulous patients, the lingual nerve becomes relatively “higher” and more closely approximates the bony crest, increasing the proximity of the lingual nerve to retained third molar surgical site in these patients [87, 88]. Lastly, with aging a patient’s response to surgical insult is less tolerant and the recuperation period grows longer. There is overwhelming clinical evidence to support the fact that the number of days missed from work and other normal activity following third molar extraction is much higher in the patient over age 40 years compared with patients under age 18 years.

As a general rule, if a patient has a fully impacted third molar that is completely covered with bone, has no obvious potential source of communication with the oral cavity, and has no signs of pathology such as an enlarged follicular sac, and if the patient is over age 25–30, the tooth probably should not be removed. Long-term follow-up by the patient’s dentist should be performed periodically, with radiography performed every several years to ensure that no adverse sequelae are occurring. If signs of pathology develop, the tooth should be removed. If the overlying bone is very thin and a removable denture is to be placed over that tooth, the tooth should probably be removed before the final prosthesis is constructed.

3.2.2 Compromised Medical Status

Patients who have impacted teeth may have some compromise in their health status, especially if they are elderly. As age increases, so does the incidence of moderate to severe cardiovascular disease, pulmonary disease, and other health problems. Thus, the combination of advanced age and compromised health status may contraindicate the removal of impacted teeth that have no pathologic processes.

Other factors may compromise the health status of younger people, such as congenital coagulopathies, asthma, and epilepsy. In this group of patients, it may be necessary to remove impacted teeth before the incipient pathologic process becomes fulminant. Thus, not only in the older compromised patient but also the younger compromised patient, the surgeon occasionally needs to remove asymptomatic as well as symptomatic third molars. The compromised medical status remains a relative contraindication and may require the surgeon to work closely with the patient’s physician to manage the patient’s medical problems. The clinician should realize that from a cardiopulmonary perspective, procedures performed under local anesthesia are essentially always safer in the medically compromised patient than those performed under general anesthesia or moderate-to-deep sedation.

3.2.3 Surgical Damage to Adjacent Structures

Occasionally an impacted tooth is positioned such that its removal may seriously compromise adjacent nerves, teeth, and other vital structures (e.g., sinus), making it prudent to leave the impacted tooth in situ. The potential complications must be weighed against the potential benefits of surgical removal of the tooth. In this clinical setting, many clinicians advocate removing only the crown of the impacted tooth and intentionally leaving the roots in place (i.e., performing a coronectomy), and scientific literature offers substantial support for this approach, particularly for mandibular third molars [89,90,91]. The risks of pathology due to the impacted tooth may be reduced with less exposure to the complications associated with root proximity to vital structures.

In older patients, the surgical extraction of impacted third molars can result in significant bony defects that may not heal adequately and, in fact, may result in the eventual loss of adjacent teeth rather than the improvement or preservation of periodontal health. This may also be viewed as a contraindication to removal of the impacted tooth.

Key Points

A variety of common pathologies affect impacted third molars.
Treatment generally includes removal of the impacted teeth.
Removal of asymptomatic impacted third molars remains a matter of clinical judgment and experience.
General health, patient age, and unusual local risk factors must be considered and may contraindicate surgery.

4 Surgery and Perioperative Care for Impactions Other than Third Molars

4.1 Exposure Versus Exposure and Bonding

Surgical exposure is a procedure intended to permit natural eruption of impacted teeth. Typically, the crowns of the teeth are surgically exposed with removal of tissues in the direction most appropriate for crown movement. The wound is then packed until it is totally epithelialized. Öhman and Öhman studied 542 impacted teeth in 389 patients treated using this technique [92]. The teeth were allowed to erupt for up to 24 months or until the greatest diameter of the crown reached the level of the mucosal surface. Of 542 teeth, only 16 were failures (failure to erupt after 24 months or with other complications). This study found that the teeth tended to show a change of inclination of the longitudinal access by rotation along the root. Age did not appear to be a factor in success, although most patients were under age 19 years. Kokich has espoused the practice of early uncovery of impacted maxillary canines, allowing them to autonomously erupt into the oral cavity until a bracket is applied [93]. Laskin and Peskin agree that if exposure of teeth is to result in successful spontaneous eruption, it should be done as soon as it is determined that the tooth is not going to erupt spontaneously [94].

More commonly, the technique of surgical exposure is combined with attachment of an orthodontic appliance to the tooth, allowing active guidance of the impacted tooth into an ideal position. Important factors in this technique are prior orthodontic treatment to provide both anchorage and adequate space within the dental arch for the impacted tooth. Many methods have been suggested for making attachment to the impacted tooth, including polycarbonate crowns, attachments such as rare earth magnets, or pins inserted into the structure of the tooth. These techniques are used rarely. The most common method of orthodontic attachment to an impacted tooth is the placement of a bonded orthodontic bracket [95]. This can usually be done with conservative exposure of the tooth, removing only enough soft tissue and bone to place the bonded bracket and avoiding exposure of the cementoenamel junction [11]. This exposure, especially when combined with the use of a wire ligature around the neck of the tooth, has been shown to increase the risk of root resorption, ankylosis, periodontal inflammation, and other complications and is contraindicated.

Studies have compared simple exposure and packing to maintain a gingival path for eruption with exposure and bonding of a bracket. In a study of impacted premolars, Thilander and Thilander showed that surgical exposure alone resulted in eruption, provided that space was present in the arch [96]. However, mesially tipped premolars had a poor prognosis and required orthodontic guidance. Iramaneerat and colleagues found that there was no difference in total orthodontic treatment time for the two techniques [97]. Pearson and colleagues found that bracketing was more costly and more likely to require reoperation [98]. Nonetheless, placing a bracket is the more popular technique, perhaps owing to orthodontist preference and patient comfort.

Flap design for exposure of maxillary canines has also been compared in many studies, although it appears that no design offers universal benefits over another in prospective studies and systematic reviews. For palatally impacted canines, both marginal and paramarginal flap designs result in identical periodontal health postoperatively [99]. For labially impacted canines, although the apically positioned flap may offer benefits to simple excisional uncovery in areas of insufficient attached gingiva, it has also been shown to result in a longer-than-normal clinical crown and tendency to reintrude after orthodontic forces are relieved [93, 100]. In many cases, bringing the tooth into the arch without excision or repositioning of facial soft tissue seems ideal.

When treating molar teeth, it is important to remove third molars that are often obstructing the second molars’ normal eruption (◘ Fig. 5.6). Ranta stated that it is typical for impacted second molars to erupt normally when the offending third molar is removed [16]. Vig also recommends routine removal of the third molar when a second molar is impacted [101]. Although removal of the second molar to allow eruption of the third molar into the second molar position may occasionally have a satisfactory outcome in the maxilla, this is not likely to happen in the mandible [102]. Malformed, severely tipped, or deeply impacted second molars may need to be extracted.

4.2 Surgical Technique

4.2.1 Exposure and Bonding

The most common type of non-third molar impaction is the palatally positioned maxillary canine. Typical surgical exposure involves reflection of a full-thickness palatal flap, conservative exposure of the tooth, and bonding of a bracket to its palatal surface (◘ Fig. 5.7a–c). If the tooth is near the free edge of the flap, soft tissue may be removed to leave the crown exposed; the wound is then packed gently during the initial healing period. If the tooth is deeply impacted, it may be more appropriate to replace the soft tissue flap, bringing a wire attached to the bonded bracket through the soft tissues near the crest of the ridge. Alternatively, if making attachment to the canine is deemed unnecessary or not possible, the flap may be returned to its original position. A full-thickness soft tissue window is then created over the canine crown which is then packed open and allowed to epithelialize, leaving the crown visible in the mouth for spontaneous eruption or attachment at a later date. The technique of replacing the flap has been examined for its periodontal consequences. The clinical outcomes show minimal effects of the closed eruption technique on the periodontium [103].

Management of the labially positioned impacted canine follows similar principles to the palatal impaction, with the added concern of maintaining keratinized, attached mucosa adjacent to the cervical line of the tooth when eruption is complete, as discussed previously. Adequate space in the arch must be established by preliminary orthodontic treatment prior to canine exposure. A full-thickness mucoperiosteal flap is elevated with mesial and distal releasing incisions extending along the sides of the canine crown. It is often useful to make these incisions more closely parallel than in other circumstances, because widely divergent releasing incisions make repositioning the flap apically more difficult if that becomes the treatment plan. Making the releasing incisions parallel—as opposed to divergent with the flap base broader than its apex—will not compromise flap viability, contrary to popular teaching. The crown of the tooth is uncovered, avoiding dissection beyond the cervical line of the tooth. A bonded bracket is attached and the flap is repositioned and secured to cover the CEJ of the tooth. The bonded bracket helps to support the attached gingiva in this apical relationship (◘ Fig. 5.8). When the tooth is too far superiorly to allow an apically repositioned flap, the wire or chain secured to the bracket is brought out from under the flap at the crest of the ridge and the flap is returned to its original position. As the tooth is orthodontically moved into position, an adequate band of keratinized gingiva either migrates with the tooth or remains in place at the alveolar crest and the tooth is guided to erupt through it. As noted previously, techniques that involve removal of the attached gingiva, leaving alveolar mucosa surrounding the cervical area of the tooth, are to be avoided in cases of limited keratinized tissue.

These basic principles of exposure of canines can be generalized to many other impacted teeth. Exposure and orthodontic attachment of maxillary and mandibular premolars can be treated much like maxillary canines. Often mandibular premolars are located relatively centrally in the alveolar process. This may also be true of mandibular molars. When this is the case, exposure from the coronal aspect of the tooth may be indicated. A bonded bracket may be placed on the occlusal surface of the tooth and orthodontic forces applied in a relatively vertical direction until the tooth is exposed sufficiently to place the orthodontic bracket in a more traditional position.

Impacted second molars with angulation, root morphology, and available space deemed adequate may be orthodontically uprighted with or without surgical exposure and bracketing. A conventional button with gold chain may be bonded to the tooth, although a molar bracket with buccal tube has been reported to offer shorter treatment times with excellent outcomes [104]. Alternatively, uprighting can be performed using miniscrew anchorage [105]. If at all feasible, surgically and/or orthodontically assisted eruption is typically more successful than extraction of the impacted second molar with either autotransplantation of a third molar or hopes of mesial eruption of the adjacent third molar [19].

4.2.2 Surgical Uprighting

Uprighting of teeth has been applied most commonly to impacted second molars. Impacted lower second molars with incomplete apical closure may be exposed and surgically uprighted according to a method nicely described by Pogrel [106]. The optimal time for uprighting a molar tooth is when two-thirds of the root has formed; molars with fully formed roots have a poor prognosis [10]. The tooth must not be buccally or lingually tipped because intact cortical plates are necessary adjacent to the tooth for stability. The technique begins with removal of the third molar (◘ Fig. 5.9a–c). This generally creates the necessary space for posterior tipping of the second molar. If no third molar is present, it will likely be necessary to remove bone posterior to the second molar. When doing so, it is important to avoid damage to the cementoenamel junction of the second molar. The tooth should not be tipped more than 90° and is splinted into place. An extremely important part of this surgical procedure is ensuring that there are no occlusal forces on the repositioned second molar. Terry and Hegtvedt describe a similar but self-stabilizing technique [107]. Postoperative root changes including resorption, pulpal canal obliteration, or asymptomatic radiolucencies may develop postoperatively and may not require treatment if they remain asymptomatic [108].

4.2.3 Transplantation

Transplantation of teeth has been advocated as an alternative to other methods of treatment of impacted teeth. Although contemporary dental implant therapy has largely overtaken this technique, transplantation remains useful for those patients who are not candidates for implant dentistry. It may be appropriate for the adult patient who cannot undergo conventional orthodontic movement of a canine or premolar. The advocated technique is a careful wide exposure of the impacted tooth. The tooth is then moved into its position within the dental arch and stabilized with a segmental orthodontic appliance. Endodontic treatment begins with calcium hydroxide paste 6–8 weeks after the surgical procedure. Conventional root canal filling is performed at 1 year following surgery. Sagne and Thilander studied 47 patients with 56 canines that were surgically transplanted [109]. This study showed a successful outcome in 54 of 56 transplanted canines. Their concluding recommendation is to perform conventional orthodontic treatment for impacted canines in children and young individuals. However, when extraction would otherwise be performed, they recommend transalveolar transplantation as a sound alternative (◘ Fig. 5.10a–d) [109].

4.2.4 Removal

Surgical removal of impacted permanent teeth may be performed when other methods of treatment are unavailable. Basic surgical principles of radiographic assessment and careful surgical technique must be followed. Conservation of bone through conservative exposure and removal with sectioning of the tooth should be considered, and care must be taken to avoid injury to the roots of adjacent teeth. Impacted teeth should be approached from the surface of the maxilla with which they are most closely associated. As noted earlier in the chapter, three-dimensional imaging is particularly helpful in achieving this goal. Labially impacted teeth are frequently removed with an elevator technique, but palatal impactions generally require removal of the crown followed by sectioning of the root. Longitudinal sectioning of the root of the palatal canine often is useful and may conserve bone. When a large palatal flap has been reflected, maintaining a palatal splint to support the soft tissues for several days prevents hematoma formation and may improve patient comfort.

Mandibular premolars are generally approached from the labial surface of the mandible. Care must be taken to preserve the integrity of the mental nerve when the impacted tooth is nearby. When the impacted lower premolar is lingually positioned, it is sometimes useful to identify the tooth through a lingual exposure; a labial flap then may be raised and a small hole placed in the labial surface of the bone to allow the premolar to be pushed through to the lingual. Removal of impacted molars is similar to removal of impacted third molars.

Key Points

Non-third molar impacted teeth may be retained or removed.
Orthodontic care is often needed to create space and/or manipulate the impacted tooth into position.
When retention is not feasible, non-third molar impactions may be monitored or removed.

5 Surgery and Perioperative Care for Impacted Third Molars

5.1 Determining Surgical Difficulty

Preoperative evaluation of the third molar, both clinically and radiographically, is a critical step in the surgical procedure for removal of impacted teeth. The surgeon pays particular attention to the variety of factors known to make the impaction surgery more or less difficult. A variety of classification systems have been developed to aid in the determination of difficulty. The three most widely used are angulation of the impacted tooth, the relationship of the impacted tooth to the anterior border of the ramus and the second molar, and the depth of the impaction and the type of tissue overlying the impacted tooth. Two standard classification systems used to describe these findings are the Pell and Gregory Classification and the Winter Classification [110, 111].

It is generally acknowledged that the mesioangular impaction, which accounts for approximately 45% of all impacted mandibular third molars, is the least difficult to remove. The vertical impaction (40% of all impactions) and the horizontal impaction (10%) are intermediate in difficulty, whereas the distoangular impaction (5%) is the most difficult.

The relationship of the impacted tooth to the anterior border of the ramus is a reflection of the amount of room available for the tooth eruption as well as the planned extraction. If the length of the alveolar process anterior to the anterior border of the ramus is sufficient to allow tooth eruption, the tooth is generally less difficult to remove. Conversely, teeth that are essentially buried in the ramus of the mandible are more difficult to remove.

The depth of the impaction under the hard and soft tissues is likewise an important consideration in determining the degree of difficulty. The most commonly used scheme for determining difficulty involves consideration of the soft tissues and partial or complete bony impaction, although the Pell and Gregory classification evaluates vertical position relative to the occlusal plane and CEJ of the adjacent second molar. This system is widely employed in part because it may be the most useful indicator of the time required for surgery and, perhaps even more importantly, because it is the system required to classify and code impaction procedures to all commercial insurance carriers. Surprisingly, factors such as the angulation of impaction, the relationship of the tooth to the anterior border of the ramus, and the root morphology may have little influence on the time that surgery requires [112].

Other factors have been implicated in making the extraction process more difficult. Roots can be either conical and fused roots or separate and divergent, with the latter being more difficult to manage. A large follicular sac around the crown of the tooth provides more room for access to the tooth, making it less difficult to extract than one with essentially no space around the crown of the tooth.

Another important determinant of difficulty of extraction is the age of the patient. When impacted teeth are removed before age 20 years, the surgery is almost always less difficult to perform. The roots are usually incompletely formed and thus less bone removal is required for tooth extraction. There is usually a broader pericoronal space formed by the follicle of the tooth, which provides additional access for tooth extraction without bone removal. Because the roots of the impacted teeth are incompletely formed, they are usually separated from the inferior alveolar nerve.

In contradistinction, removal of impacted teeth in patients of older age groups is almost always more difficult. The roots are usually completely formed and are thus longer, which requires more bone removal, and closer to the inferior alveolar canal, which increases the risk of postsurgical anesthesia and paresthesia. The follicular sac almost always degenerates with age, which makes the pericoronal space thinner; as a result, more bone must be removed for access to the crown of the tooth. Finally, there is increasing density and decreasing elasticity in the bone, necessitating greater bone removal to deliver the tooth from its socket. All of these factors (Pell and Gregory Classification, Winter Classification, root characteristics, patient age) as well as patient BMI have been combined to form an index which has shown high accuracy in predicting procedure difficulty [113]. Use of such objective predictors may be beneficial, given that it has been shown that even senior surgeons are inaccurate preoperatively in estimating the difficulty of what become challenging impacted extractions [114].

A corollary of surgical difficulty is difficulty of recovery from the surgery. As a general rule, a more challenging and time-consuming surgical procedure results in a more troublesome and prolonged postoperative recovery. It is more difficult to perform surgery in the older individual, and it is harder for these patients to recover from the surgical procedure.

5.2 Technique for Removal

The technique for removal of impacted third molars must be learned on a theoretic basis and then performed repeatedly to gain adequate experience. There is more variety in presentation of impacted third molars than in any other condition requiring a dental surgical procedure. Therefore, extensive experience is required to master their removal. A variety of textbooks are available that describe in detail the techniques for removal of the different types of impactions [115, 116].

Tips

Clinical factors increasing difficulty of impacted third molar removal:

Unusually young or old patient
Awkward access to surgical site
Quantity of bone to be removed
Angulation of tooth
Proximity to second molar

In general, the surgeon’s approach must gain adequate access to the underlying bone and tooth through a properly designed and reflected soft tissue flap. Bone must be removed in an atraumatic, aseptic, and non-heat-producing technique, with as little bone removed and damaged as possible. The tooth is then divided into sections and delivered with elevators, using judicious amounts of force to prevent complications. Finally, the wound must be thoroughly debrided mechanically and by irrigation to provide the best possible healing environment in the postoperative period.

The initial step in removing impacted teeth is to reflect a mucoperiosteal flap, which is adequate in size to permit access. The most commonly used flap is the envelope flap, which extends from just posterior to the position of the impacted tooth anteriorly to approximately the level of the first molar (◘ Fig. 5.11a, b). If the surgeon requires greater access to remove a deeply impacted tooth, the envelope flap may not be sufficient. In that case, a release incision is done on the anterior aspect of the incision, creating a three-cornered flap (◘ Fig. 5.11c, d). Although the envelope incision has classically been associated with fewer complications, more recent split-mouth or crossover studies have disagreed on which design results in less pain, edema, trismus, and wound dehiscence [117,118,119] or have concluded that there is no difference between flap designs [120]. Of note, the buccal artery is sometimes encountered when creating a releasing incision, and this may be bothersome during the early portion of the surgery.

The posterior extension of the incision must extend to the lateral aspect of the anterior border of the mandibular ramus. The incision should not continue posteriorly in a straight line because the mandibular ramus diverges laterally. If the incision were to be extended straight, the blade might damage the lingual nerve. Miloro used high-resolution magnetic resonance imaging to demonstrate that the lingual nerve may be intimately associated with the lingual cortical plate in the third molar region in 25% of cases and be above the lingual crest in 10% [121]. As noted earlier in the chapter, this is even more of a concern in otherwise edentulous patients [87, 88]. The mucoperiosteal flap is reflected laterally to the external oblique ridge with a periosteal elevator and held in this position with a retractor such as an Austin or Minnesota.

The most commonly used incision used for the maxillary third molar is also an envelope incision (◘ Fig. 5.12a, b). It extends posteriorly from the distobuccal line angle of the second molar and anteriorly to the first molar. A releasing incision is rarely necessary for the maxillary third molar (◘ Fig. 5.12c, d), although it may be useful when the occlusal surface of the third molar is at or superior to the midportion of the second molar root.

The second major step is bone removal from around the impacted tooth. Most surgeons use a high-speed, high-torque air- or nitrogen-driven handpiece, although a few surgeons still choose to use a chisel, and others now use a piezoelectric handpiece. It is essential that the handpiece exhaust the air pressure away from the surgical site to prevent tissue emphysema or air embolism, and that the handpiece can be sterilized completely, usually in a steam autoclave. High-speed high-torque electric drills have gained wide acceptance and, like the nitrogen-driven instruments, greatly reduce the time required for bone removal and tooth sectioning.

The bone on the occlusal, buccal, and (cautiously) on the distal aspects of the impacted tooth is removed down to the cervical line. The amount of bone that must be removed varies with the depth of the impaction. It is advisable not to remove any bone on the lingual aspect because of the likelihood of damage to the lingual nerve (◘ Fig. 5.13a, b). This is also the reason for cautious distal bone removal, as the lingual cortex of the mandible (and the course of the lingual nerve) curves laterally just posterior to the third molar, making for an easy iatrogenic misadventure of the bur entering the perimeter of the pterygomandibular space. A variety of burs can be used to remove bone, but the most commonly used are the no. 8 round bur and the 703 fissure bur.

For maxillary teeth, bone removal is done primarily on the lateral aspect of the tooth down to the cervical line to expose the entire clinical crown. Frequently, the bone on the buccal aspect is thin enough that it can be removed with a periosteal elevator or a chisel using manual digital pressure.

Once the tooth has been sufficiently exposed, it is sectioned into appropriate pieces so that it can be delivered from the socket. The direction in which the impacted tooth is divided is dependent on the angulation of the impaction. Tooth sectioning is performed either with a bur, chisel, or Piezoelectric handpiece, but the bur is most commonly used because it is efficient and provides a more predictable plane of sectioning. The tooth is usually divided three-quarters of the way through to the lingual aspect and then split the remainder of the way with a straight elevator or a similar instrument. This prevents injury to the lingual cortical plate and reduces the possibility of damage to the lingual nerve.

The mesioangular impaction is usually the least difficult to remove. This is in part because of the favorable angulation of the tooth relative to the mandibular ramus and adjacent second molar but also because the long axis of the tooth parallels the long axis of the bur angle one is able to achieve intraorally with a non-contra angle handpiece. After sufficient bone has been removed, the distal half of the crown is sectioned off from the buccal groove to just below the cervical line on the distal aspect of the tooth. This portion of the tooth is delivered, and the remainder of the tooth is removed with a small straight elevator placed at a purchase point on the mesial aspect of the cervical line (◘ Fig. 5.14a–c). An alternative is to prepare a purchase point in the tooth with the drill and use a crane pick, Cogswell B, or a Cryer elevator in the purchase point to deliver the tooth.

The horizontal impaction usually requires the removal of more bone than does the mesioangular impaction. The crown of the tooth is usually sectioned from the roots and delivered with a Cryer elevator. The roots are then displaced into the socket that was previously occupied by the crown and are delivered into the mouth. Occasionally, they may need to be sectioned into separate portions and delivered independently (◘ Fig. 5.15a–d).

The vertical impaction is one of the more difficult ones to remove, especially if it is deeply impacted. The procedure for bone removal and sectioning is similar to that for the mesioangular impaction in that occlusal, buccal, and judicious distal bone is removed first. The distal half of the crown is sectioned and removed, and the tooth is elevated by applying a small straight elevator at the mesial aspect of the cervical line (◘ Fig. 5.16a–c). The option of preparing a purchase point in the tooth is also frequently used, as for the mesioangular impaction.

The most difficult tooth to remove is one with a distoangular impaction. After the removal of bone, the crown is usually sectioned from the roots just above the cervical line and delivered with a Cryer elevator. A purchase point is then prepared in the tooth, and the roots are delivered together or sectioned and delivered independently with a Cryer elevator (◘ Fig. 5.17a–c). Extraction of this impaction is more difficult because more distal bone must be removed and the tooth tends to be elevated posteriorly into the ramus portion of the mandible.

Impacted maxillary third molars are rarely sectioned because the overlying bone is thin and relatively elastic. In patients with thicker bone, the extraction is usually accomplished by removing additional bone rather than by sectioning the tooth. The tooth should never be sectioned with a chisel because it may be displaced into the maxillary sinus or infratemporal fossa when struck with the chisel (◘ Fig. 5.18a,b).

Once the impacted tooth is delivered from the alveolar process, the surgeon must pay strict attention to debriding the wound of all particular bone chips and other debris. The best method to accomplish this is to mechanically debride the socket and the area under the flap with a periapical curette. A bone file should be used to smooth any rough sharp edges of the bone. A mosquito hemostat is usually used carefully to remove any remnant of the dental follicle, with care taken to not overzealously grasp tissue lingually where the residual lingual plate is often paper thin and adjacent to the lingual nerve. Finally, the socket and wound should be thoroughly irrigated with saline or sterile water (30–50 mL is optimal) [95]. Within certain limitations, the more irrigation that is used, the less likely the patient is to have a dry socket, delayed healing, or other complications.

Traditionally, the incision is closed primarily. Prospective studies comparing traditional suturing to minimal or no suture techniques have shown equivalent or improved pain, edema, trismus, bleeding, and periodontal pocketing when using less sutures [123, 124]. Improved outcomes may be secondary to successful drainage of surgical site fluid with minimal suturing, as techniques with traditional suturing but drain placement have also shown improved outcomes [125].

Key Points

Impacted third molars are removed by following a sequence of basic steps based on fundamental surgical principles.
Because third molars’ morphology, position, and environment are highly variable, each step must be adapted to the presenting clinical circumstance.
For this reason, mastery of impacted third molar removal requires thorough understanding and extensive experience.

5.3 Technique for Coronectomy

Coronectomy describes the procedure of removing the crown of an impacted tooth which does not have evidence of pulpal or periapical pathology while leaving behind the tooth roots. Although this procedure has historically been underused, likely for reasons of unfamiliarity, it is well documented that coronectomy can decrease the risk of inferior alveolar nerve injury in high-risk cases. Postoperative paresthesia is not impossible, but it is exceedingly rare [126, 127].

The procedure typically involves bone removal followed by sectioning of the crown from the roots at the cementoenamel junction, removing all enamel from the socket, with additional root and bone smoothing as needed for the residual roots to be >3 mm below the crestal bone. Care should be taken to avoid root mobilization, and if the roots are found to be mobile the coronectomy should be aborted and a completion extraction should be performed. The clinician may elect to remove additional exposed pulpal tissue and/or place antibiotic powder prior to closure [128, 129]. An immediate postoperative panoramic should be taken to ensure that no enamel is retained and, if found, repeat coronectomy should be completed [130].

If coronectomy is performed correctly, the residual tooth roots usually remain vital with uninflamed pulps. Thus, these vital roots can be expected to migrate or “erupt” 1–4 mm over the first year [128, 131], and thus even if root retrieval is eventually required the vast majority of roots will no longer approximate the canal [132]. If the clinician wishes to minimize residual root migration or has a concern for periodontal defects distal to the second mandibular molar, guided bone regeneration over the residual roots may be helpful [133, 134]; however, from a practical perspective this may be unnecessary [135].

The most common early complications associated with coronectomy include postoperative pain, swelling, and infection. Complication rates are comparable to third molar extraction. The most common late complications include continued migration of the root through the crestal bone or continued pain, although almost all complications appear to occur within 12 months [126, 132, 133]. Only continued root migration is documented after 12 months with any relevant frequency, and this risk may be affected by age, female sex, and angulation of impaction [126, 136].

Coronectomy should be considered in cases of impacted third molars with radiographic evidence suggestive of close proximity to the inferior alveolar canal [137], particularly in older patients where the risk of paresthesia is higher and risk of spontaneous improvement lower, or in patients where paresthesia would be highly psychologically or functionally distressing. Although many providers are hesitant to perform this procedure given a lack of exposure in residency or thereafter, oral and maxillofacial surgeons—who possess extensive training in extraction of impacted teeth—are well-equipped to perform this relatively straightforward procedure in the appropriate indications.

Key Points

Coronectomy is considered in cases with high risk of inferior alveolar nerve injury from third molar removal.
Radiographic indicators of nerve proximity and injury potential have been established for both panoramic and cone beam imaging.
Risks and complications of coronectomy are comparable to third molar removal and generally easily managed.

5.4 Use of Perioperative Systemic Antibiotics

One of the primary goals of the surgeon in performing any surgical procedure is to prevent postoperative infection as a result of surgery. To achieve this goal, prophylactic antibiotics are necessary in some surgical procedures. Most of these procedures fall into the clean-contaminated or contaminated categories of surgery. The incidence of postoperative infections in a clean surgery is related more to operator technique than to the use of prophylactic antibiotics.

Surgery for the removal of impacted third molars clearly fits into the category of clean-contaminated surgery; however, the exact incidence of postoperative infection is unknown. In the usual sense of the word, infection probably is a rare occurrence following third molar surgery. This means that it is unusual to see pain, swelling, and a production of purulence that requires incision and drainage or antibiotic therapy. The incidence of such infections is very low for most surgeons. In general, a competent, experienced surgeon would expect to have an infection rate in the range of 1–5% for all third molar procedures [138]. It is difficult, and probably impossible, to reduce infection rates below 5% with the use of prophylactic antibiotics. Therefore, it is unnecessary to use prophylactic antibiotics in third molar surgery to prevent postoperative infection in the normal healthy patient. Indeed, randomized trials spanning the past 40 years have almost unanimously shown no significant benefit in perioperative antibiotics with regard to postoperative infection [138,139,140,142].

A more subtle type of wound healing problem that occurs after the surgical removal of the impacted mandibular third molar is the so-called alveolar osteitis or dry socket. This disturbance in wound healing is most likely caused by the combination of saliva and anaerobic bacteria. The use of prophylactic antibiotics in third molar surgery does, in fact, reduce the incidence of dry socket. Other techniques that reduce bacterial contamination of the socket, such as copious irrigation, preoperative rinses with chlorhexidine, and placement of antibiotics in the extraction socket, are also effective [142,143,144,145,146,147,148,150]. Once again, the issue of risks versus benefits becomes important. Although systemic antibiotics are effective in the reduction of postoperative dry socket, they are no more effective than are local measures. The increase of antibiotic-related complications, such as allergy, resistant bacteria, gastrointestinal side effects, and secondary infections, is not outweighed by the benefits. Therefore, the routine administration of perioperative systemic antibiotic does not seem to be valid.

5.5 Use of Perioperative Steroids

Just as the oral and maxillofacial surgeon desires to minimize the incidence of infection following third molar surgery, he or she also has a major interest in reducing the perioperative morbidity. The use of corticosteroids to help minimize swelling, trismus, and pain has gained wide acceptance in the oral and maxillofacial surgery community. The method of usage, however, is extremely variable, and the most effective therapeutic regimen has yet to be clearly delineated.

There is little doubt that an initial intravenous dose of steroid at the time of surgery has a major clinical impact on swelling and trismus in the early postoperative period. However, if the initial intravenous dose is not followed up with additional doses of steroids, this early advantage disappears by the second or third postoperative day. Maximum control of swelling requires that additional steroids be given for 1 or 2 days following surgery. The two most widely used steroids are dexamethasone and methylprednisolone. Both of these are almost pure glucocorticoids, with little mineralocorticoid effect. Additionally, these two appear to have the least depressing effect on leukocyte chemotaxis. Common dosages of dexamethasone are 4–12 mg IV at the time of surgery. Additional oral dosages of 4–8 mg bid on the day of surgery and for 2 days afterward result in the maximum relief of swelling, trismus, and pain. Methylprednisolone is most commonly given 125 mg IV at the time of surgery followed by significantly lower doses, usually 40 mg PO tid or qid, later on the day of surgery and for 2 days after surgery.

High-dose short-term steroid use is associated with minimal side effects. It is contraindicated in the patient with gastric ulcer disease, active infection, and certain types of psychosis. The administration of perioperative steroids may increase the incidence of alveolar osteitis after third molar surgery, but the data are lacking as to the precise degree of increase [150,151,152,153,155].

6 Expected Postoperative Course

Preoperative consultation permits the surgeon to present not just risks and benefits, but essential information the patient needs to be prepared for the likely postoperative course.

Surgical removal of impacted third molars is associated with a moderate incidence of complications, around 10% [156, 157]. These complications range from the expected and predictable outcomes, such as swelling, pain, stiffness, and mild bleeding, to more severe and permanent complications, such as inferior alveolar nerve anesthesia and fracture of the mandible. The overall incidence of complication and the severity of these complications are associated most directly with the depth of impaction, that is, whether it is a complete bony impaction, and to the age of the patient [157,158,160]. Because of factors already discussed, removal of impacted teeth in the older patient is associated with a higher incidence of postoperative complications, especially alveolar osteitis, infections, mandible fracture, and inferior alveolar nerve anesthesia. The removal of complete bony impactions is likewise associated with increased postoperative pain and morbidity and an increase in the incidence of inferior alveolar nerve anesthesia.

Another determinant of the incidence of complications of third molar surgery is the relative experience and training of the surgeon. The less experienced surgeon will have a significantly higher incidence of complications than the trained experienced surgeon [1, 2]. After the surgical removal of an impacted third molar, certain normal physiologic responses occur. These include such things as mild bleeding, swelling, stiffness, and pain. All of these are interpreted by the patient as being unpleasant and should therefore be minimized as much as possible.

With experience, most oral and maxillofacial surgeons develop a clear understanding of third molar surgery’s impact on their patients’ lives. However, despite its extreme importance, this topic has received little significant study. Several authorities have published data on the short-term impact of third molar removal on quality of life [161, 162]. As expected, third molar removal often has a profoundly negative impact for the first 4–7 days after surgery, but longer follow-up reveals improved quality of life, mostly resulting from the elimination of chronic pain and inflammation (usually pericoronitis). Large population studies of post-third molar removal health-related quality of life have provided detailed information on the consequences of impaction surgery and have shed light on predictors of delayed recovery [162,163,164,166]. The performing surgeon must be familiar with this rapidly expanding knowledge if he or she is to provide proper preoperative counseling.

6.1 Bleeding

Bleeding can be minimized by using a good surgical technique and by avoiding the tearing of flaps or excessive trauma to the overlying soft tissue. When a vessel is cut, the bleeding should be stopped to prevent secondary hemorrhage following surgery. The most effective way to achieve hemostasis following surgery is to apply a moist gauze pack directly over the site of the surgery with adequate pressure. This is usually done by having the patient bite down on a moist gauze pad. In some patients, immediate postoperative hemostasis is difficult. In such situations a variety of techniques can be employed to help secure local hemostasis, including oversuturing and the application of topical thrombin on a small piece of absorbable gelatin sponge into the extraction socket. The socket can also be packed with oxidized cellulose. Unlike the gelatin sponge, oxidized cellulose can be packed into the socket under pressure. In some situations microfibrillar collagen can be used to promote platelet plug formation. Patients who have known acquired or congenital coagulopathies require extensive preparation and preoperative planning (e.g., determination of the international normalized ratio, factor replacement, hematology consultation) before third molars are removed surgically.

6.2 Swelling

Postsurgical edema or swelling is an expected sequela of third molar surgery. As discussed earlier, the parenteral administration of corticosteroids is frequently employed to help minimize the swelling that occurs. The application of ice packs to the face may make the patient feel more comfortable but has no effect on the magnitude of edema [167]. The swelling usually reaches its peak by the end of the second postoperative day and is usually resolved by the fifth to seventh day.

6.3 Stiffness

Trismus is a normal and expected outcome following third molar surgery. Patients who are administered steroids for the control of edema also tend to have less trismus. Like edema, jaw stiffness usually reaches its peak on the second day and resolves by the end of the first week.

6.4 Pain

Another postsurgical morbidity expected after third molar surgery is pain. The postsurgical pain begins when the effects of the local anesthesia subside and reaches its maximum intensity during the first 12 h postoperatively [168]. A large variety of analgesics are available for management of postsurgical pain. The most common ones are combinations of acetylsalicylic acid or acetaminophen with codeine and its congeners, and the nonsteroidal anti-inflammatory analgesics. Women and red-haired individuals may be more sensitive to postoperative pain and anxiety [169, 170]; thus, they may require more perioperative analgesics. Analgesics should be given before the effect of the local anesthesia subsides, and ideally before any noxious stimulus. In this manner, the pain is usually easier to control, requires less drug, and may require a less potent analgesic. The administration of nonsteroidal anti-inflammatories before surgery may be beneficial in aiding in the control of postoperative pain.

The use of opioids, particularly those prescribed by dental providers, has become a primary concern in dentistry and medicine over the past decade. It is the provider’s responsibility to offer patients opioid-sparing analgesic regimens including multimodal techniques. Recently, extended release liposomal bupivacaine (Exparel) has been FDA approved for use in third molar surgery. Research currently undergoing across the country—including the authors’ institution—has shown improved pain scores, decreased opioid use, and subjectively improved quality of life with the use of this medication.

The most important determinant of the amount of postoperative pain that occurs is the length of the operation. Neither swelling nor trismus correlates with the length of time of the surgery. There is, however, a strong correlation between postoperative pain and trismus, indicating that pain may be one of the principal reasons for the limitation of opening after the removal of impacted third molars [171].

Key Points

Pain, swelling and stiffness, and early minor bleeding are expected following third molar removal.
Morbidity is minimized by careful surgical technique and appropriate perioperative pharmacologic management.
Perioperative or postoperative systemic antibiotic use lacks high-level supporting evidence for use in routine third molar removal.
Perioperative intravenous steroid use may provide several benefits with minimal risk and is well-supported by surgical and anesthesia literature.
Postoperative pain management should be multimodal and opioid-sparing.

7 Complications Following Third Molar Surgery

7.1 Infection

An uncommon postsurgical complication related to the removal of impacted third molars is infection. The incidence of infection following the removal of third molars is very low, ranging from 1.7% to 2.7% [172]. Infection after removal of mandibular third molars is almost always a minor complication. About 50% of infections are localized subperiosteal abscess-type infections, which occur 2–4 weeks after a previously uneventful postoperative course. These are usually attributed to debris that is left under the mucoperiosteal flap and are easily treated by surgical debridement and drainage. Of the remaining 50%, few postoperative infections are significant enough to warrant surgery, antibiotics, and hospitalization. Infections occur in the first postoperative week after third molar surgery approximately 0.5–1% of the time. This is an acceptable infection rate and would not be decreased with the administration of prophylactic antibiotics.

7.2 Tooth Fracture

One of the most frequent problems encountered in removing third molars is the fracture of a portion of the root, which may be difficult to retrieve. In these situations the root fragment may be displaced into the submandibular space, the inferior alveolar canal, or the maxillary sinus. Uninfected roots left within the alveolar bone have been shown to remain in place without postoperative complications [173]. The pulpal tissues undergo fibrosis, and the root becomes totally incorporated within the alveolar bone. Aggressive and destructive attempts to remove portions of roots that are in precarious positions seem to be unwarranted and may cause more damage than benefit. Radiographic follow-up may be all that is required.

7.3 Alveolar Osteitis

The incidence of alveolar osteitis or dry socket following the removal of impacted mandibular third molars varies between 3% and 25%. Most of the variation is most likely a result of the definition of the syndrome. When dry socket is defined in terms of pain that requires the patient to return to the surgeon’s office, the incidence is probably in the range of 20–25% [2, 173,174,175,176,177,178,179,181]. Indeed, in his review of the various definitions of alveolar osteitis, Blum indicates that the better controlled studies tend to report a risk of 25–30% following removal of impacted mandibular third molars [182].

The pathogenesis of alveolar osteitis has not been clearly defined, but the condition is most likely the result of lysis of a fully formed blood clot before the clot is replaced with granulation tissue. This fibrinolysis occurs during the third and fourth days and results in symptoms of pain and malodor after the third day or so following extraction. The source of the fibrinolytic agents may be tissue, saliva, or bacteria [174]. The role of bacteria in this process can be confirmed empirically based on the fact that systemic and topical antibiotic prophylaxis reduces the incidence of dry socket by approximately 50–75%. The periodontal ligament may also play a role in the development of alveolar osteitis.

Of the factors associated with dry socket, smoking and hormonal factors appear to be two of the most influential [175, 176]. Not only are women more likely to experience dry socket than men, but their use of oral contraceptives has consistently been shown to further increase that risk [183, 184]. Hormonal influence is further confirmed by the observation that the menstrual cycle itself has a relationship to incidence of dry socket [185]. Dry socket occurrence can be reduced by several techniques, most of which are aimed at reducing the bacterial contamination of the surgical site. Presurgical irrigation with antimicrobial agents such as chlorhexidine reduces the incidence of dry socket by up to 50% [2]. Copious irrigation of the surgical site with large volumes of saline is also effective in reducing dry socket [122]. Furthermore, continuation of irrigation by the patient at home using a Monoject syringe and tap water is effective [186]. Topical placement of small amounts of antibiotics such as tetracycline or lincomycin may also decrease the incidence of alveolar osteitis [176,177,178,180].

The goal of treatment of dry socket is to relieve the patient’s pain during the delayed healing process. This is usually accomplished by irrigation of the involved socket, gentle mechanical debridement, and placement of an obtundent dressing, which usually contains eugenol. The dressing may need to be changed on a daily basis for several days and then less frequently after that. The pain syndrome usually resolves within 3–5 days, although it may take as long as 10–14 days in some patients. There is some evidence that topical antibiotics such as metronidazole may hasten resolution of the dry socket [181]. The clinician should realize that up to half of patients with dry socket will require four or more postoperative visits in the process of managing their condition [182].

In summary, alveolar osteitis is a disturbance in healing that occurs after the formation of a mature blood clot but before the blood clot is replaced with granulation tissue. The primary etiology appears to be one of excess fibrinolysis, with bacteria playing an important but yet ill-defined role. Antimicrobial agents delivered by perioperative mouthrinses, topically placed in the socket, or administered systemically all help to reduce the incidence of dry socket. Mechanical debridement and copious saline irrigation of the surgical wound also are effective in reducing the incidence of dry socket. A rational approach may be to provide preoperative chlorhexidine rinses for approximately 1 week before surgery, irrigate the wound thoroughly with normal saline at the conclusion of surgery, place a small square of gelatin sponge saturated with tetracycline in the socket, and continue chlorhexidine rinses with or without patient socket irrigation for 1 additional week. This combination approach should substantially reduce the incidence of dry socket.

7.4 Nerve Disturbances

Surgical removal of mandibular third molars places both the lingual and inferior alveolar branches of the third division of the trigeminal nerve at risk for injury. The lingual nerve is most often injured during soft tissue flap reflection, whereas the inferior alveolar nerve is injured when the roots of the teeth are manipulated and elevated from the socket. The generally accepted incidence of injury to the inferior alveolar and lingual nerves following third molar surgery is about 3% [156,157,158,159,161, 186,187,189]. Only a small proportion of these anesthesia and paresthesia problems remain permanent. However, there is a significant incidence of some minor alterations of sensation after injury caused by third molar surgery. As many as 45% of nerve compression injuries, which are typical in third molar surgery, result in a permanent neurosensory abnormality [190].

Inferior alveolar nerve injury is most likely to occur in specific situations. The first and most commonly reported predisposing factor is complete bony impaction of mandibular third molars. The angulation classifications most commonly involved are usually mesioangular and vertical impaction. In some cases, nerve proximity to the root is indicated by an apparent narrowing of the inferior alveolar canal as it crosses the root or severe root dilaceration adjacent to the canal. Other well-documented radiographic signs are diversion of the path of the canal by the tooth, darkening of the apical end of the root indicating that it is included within the canal, and interruption of the radiopaque white line of the canal [191]. In surgically verified inferior alveolar nerve injuries, the presence of more than one of these signs was highly sensitive but not highly specific for the risk of injury, whereas the absence of all of these signs had a strong negative predictive value [191]. More recently, Su and colleagues have reviewed Rood’s classic seven panoramic signs associated with inferior alveolar nerve injuries and shown that the presence of any one of a subset of them—diversion of the canal, interruption of the white line of the canal, and darkening of the root—increases the risk of at least temporary paresthesia from the baseline 3–4% to 8–22% [192]. Thus, when these are noted on a preoperative evaluation of the radiograph, the surgeon should take extraordinary precautions to avoid injury to the nerve, such as additional bone removal or sectioning of the tooth into extra pieces, and the patient should be counseled in advance regarding his or her increased risk of nerve injury.

When an injury to the lingual or inferior alveolar nerve is diagnosed in the postoperative period, the surgeon should begin long-term planning for its management including consideration of referral to a neurologist and/or microneurosurgeon. These issues are dealt with elsewhere in this textbook.

7.5 Rare Complications

The complications already discussed are the more common occurrences, accounting for the great majority of complications in surgery to remove impacted third molars. Several additional complications occur only rarely and are mentioned briefly.

Maxillary third molars that are deeply impacted may have only thin layers of bone posteriorly separating them from the infratemporal fossa, or anteriorly separating them from the maxillary sinus. Small amounts of pressure in an errant direction can result in displacement of the maxillary third molar into these adjacent spaces. When a maxillary third molar is displaced posteriorly into the infratemporal fossa, the surgeon should try to manipulate the tooth back into the socket with finger pressure placed high in the buccal vestibule near the pterygoid plates. If this is unsuccessful, the surgeon can attempt to recover the tooth by placing the suction tip into the socket and aiming it posteriorly. If both of these maneuvers are unsuccessful in recovering the tooth, the most effective technique is to allow the tooth to undergo fibrosis and to return 2–4 weeks later to remove it. If the tooth is asymptomatic and is not causing any restriction in jaw movement, infection, or pain, the surgeon should consider leaving the tooth in place. If the decision is made to remove the tooth, three-dimensional localization of the tooth should be done before surgery is initiated.

If the tooth is displaced into the maxillary sinus, retrieval is usually done by a Caldwell-Luc procedure at the same appointment. The surgeon should localize the tooth with at least a one-dimensional radiographic view and preferably a three-dimensional study before performing the retrieval surgery [193].

Fracture of the mandible during the removal of impacted mandibular third molars is a rare occurrence. The typical situation is a deeply impacted third molar, most commonly in an older individual with dense bone. The surgeon places excessive pressure on the tooth with an elevator in an attempt to deliver the tooth or tooth section into the mouth; the fracture occurs, and the remaining portion of the tooth is easily retrieved. The surgeon should then perform an immediate reduction and fixation of the fracture. If the surgeon has the experience and the armamentarium available, rigid internal fixation with miniplates is an excellent choice in this unfortunate situation. Wire fixation and application of intermaxillary fixation is an acceptable alternative. Late mandible fractures usually occur 4–6 weeks following extraction in patients over age 40 years.

Rarely, patients can develop severe, life-threatening cerviofacial and even mediastinal infections following routine removal of impacted teeth in otherwise healthy patients [194,195,196]. Any patient presenting within 48 h after routine impacted tooth extraction with severe pain, swelling, trismus, dysphagia, dyspnea, or systemic signs and symptoms should be thoroughly evaluated. Although polymicrobial infections are the rule in odontogenic infections, group A streptococcus should also be considered in these cases, particularly if the patient’s condition becomes consistent with a necrotizing soft tissue infection.

Key Points

A variety of both common and rare complications may result from impacted third molar removal.
Alveolar osteitis remains the most common postoperative complication.
Prompt treatment of complications minimizes morbidity, so patients must know how to contact their surgeon if their postoperative course may be deviating from the expected.

8 Periodontal Healing After Third Molar Surgery

Among the important reasons for removing impacted third molars is preserving periodontal health or, in some situations, treating a periodontitis that already exists [197]. A relative contraindication to the removal of impacted third molars is a situation in which there is good periodontal health and a complete bony impaction in an older patient. Removal is contraindicated because the healing response in older patients would likely result in a large persistent postsurgical defect.

After third molar surgery, the bone height distal to the second molar usually remains at the preoperative level [57, 198, 199], although some studies have indicated a net gain in bone level after surgery [200]. If the bone level on the distal aspect of the mandibular second molar is compromised by the presence of the third molar, it usually remains at that level following the healing of the bone. There is universal agreement that bone healing is better if surgery is done before the third molar resorbs the bone on the distal aspect of the second molar and while the patient is young [58, 59, 201]. The greatest bony defect occurs in situations in which the third molar has resorbed extensive amounts of bone from the second molar in an older patient, which compromises bony repair and bone healing.

The other periodontal parameter of importance is attachment level or, less accurately, sulcus or pocket depth. As with bone levels, if the preoperative pocket depth is great, the postoperative pocket depth is likely to be similar. In most studies the attachment level has been found to be at essentially the same level as it is preoperatively [198, 202, 203]. In older patients with complete bony impactions, pocket depth and attachment levels may be significantly lower than preoperative levels. However, in patients younger than age 19 years, removal of complete bony impactions results in no compromise in attachment level or pocket depth. Initial healing after third molar surgery usually results in a reduction in pocket depth in young patients [57]. The long-term healing in this group continues for up to 4 years after surgery, with continuing reduction in probable pocket depths [200]. However, long-term follow-up of older patients clearly demonstrates that this long-term healing does not occur [58, 200].

Usually, the surgeon makes an attempt to mechanically debride the distal aspect of the second molar root area with a curette to encourage improved bone regeneration following third molar extraction. In recent years, attention has turned to placing graft material in the third molar socket after its removal. Many studies have shown that routine use of adjunctive techniques to regenerate bone in the lower third molar socket, including use of graft materials, is not warranted [204,205,206]. Dodson has studied this question exhaustively and has identified a population of patients in whom bone grafting the third molar socket appears to have a predictable benefit [207,208,209]. These are patients who are older than 25 years of age, have pre-existing periodontal defects at the second molar such as probing depths greater than 4 mm or attachment levels greater than 3 mm, and horizontal or mesioangular third molar impaction. Some studies suggest that patients with two of these risk factors may also have increased risk for persistent periodontal defects on the distal of the second molar [210, 211], although evidence supporting bone grafting or other interventions remains inconclusive. Another more recent consideration has been the application of platelet-rich fibrin (PRF) in third molar sockets to improve inflammatory complications as well as periodontal pocketing. Results to date appear to be mixed; however, the average patient in these studies is <25–30 years old, and an older population—similar to that in Dodson’s studies—may need to be evaluated to appreciate any consistent clinical benefits [212, 213].

In summary, periodontal healing following third molar surgery is clearly best when the impacted tooth is removed before it becomes exposed in the mouth, before it resorbs bone on the distal aspect of the second molar, and when the patient is as young as possible [57,58,59,60,61, 198,199,200,201,202,203]. If the third molar is partially impacted and is partially exposed in the mouth, it should be removed as soon as possible. The reason for this is that there is already a deep and potentially destructive periodontal lesion that is difficult for the patient to maintain hygienically. Even if the patient is asymptomatic, the impacted tooth should be removed as soon as possible to allow the best periodontal healing after surgery as possible. In these situations the periodontal healing is compromised because of the fact that there was already a destructive lesion caused by the presence of the partially impacted third molar.

The completely impacted third molar in a patient older than age 35 years should be left undisturbed unless some pathology develops. Removal of asymptomatic completely impacted third molars in these older patients results in pocket depths that are significant and the potential loss of alveolar bone on the posterior aspect of the second molar.

Key Points

Improved periodontal health is an important outcome of impacted third molar removal.
Distal second molar periodontal attachment outcomes are better in patients under age 25.
Alveolar bone grafting may be beneficial in select older patients with pre-existing periodontal defects distal to the mandibular second molar.

Conclusion

The issue of whether to remove impacted third molars has generated much controversy over the past three decades. The reason for this controversy has been the lack of long-term prospective studies that have followed up large groups of patients with impacted teeth to determine the eventual outcome of leaving impactions in situ. Recently there has been intense interest in establishing clear scientifically valid evidence regarding the role of third molar removal in patient health care, especially with respect to predicting the likelihood of eruption or the risk of future pathology in asymptomatic patients. Ongoing studies are already greatly improving our knowledge in these areas, and significant advances will continue to appear in the scientific literature.

Clearly, impacted third molars associated with or contributing to adjacent pathology require removal as early as is reasonably possible. The major controversy regarding proper care centers around asymptomatic unerupted third molars. It is clear that although incompletely erupted mandibular third molars will continue to erupt beyond age 18 or 20 years, in the vast majority of these situations, there will be a soft tissue or bone tissue flap over the distal aspect of the erupted third molar, which has the potential to cause recurrent pericoronitis. In fact, the tooth that is most likely to be involved in pericoronitis is the erupted vertically positioned third molar with a soft tissue flap (operculum) over the distal aspect of the tooth. Although attempts at very early prediction of impaction and removal of tooth buds at age 8 or 9 years have now been largely abandoned, it is likely that by age 16 or 18 years the dentist and surgeon can reasonably predict whether there will be adequate room for the tooth to erupt with sufficient clearance of the anterior ramus to prevent soft tissue overgrowth (as in patients with large arch length and relatively small teeth).

Soft tissue and bone tissue healing will occur at a maximum level if the surgery to remove impacted third molars is done as early possible. By age 16 years, if the diagnosis of inadequate room for functional eruption can be made, then the asymptomatic third molar should be removed. Even though the tooth may be completely covered with soft and hard tissue, removing the third molar at that age will eliminate the future pathologic potential and maximize the periodontal health of the second molar; these are important goals of the oral and maxillofacial surgeon.

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Authors and Affiliations

Oral and Maxillofacial Surgery and Dental Anesthesiology, The Ohio State University College of Dentistry, Columbus, OH, USA
Gregory M. Ness
Oral and Maxillofacial Surgery, The University of North Carolina, Chapel Hill, NC, USA
George H. Blakey
University of Tennessee Medical Center, Knoxville, TN, USA
Ben L. Hechler

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Gregory M. Ness
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George H. Blakey
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Ben L. Hechler
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Correspondence to Gregory M. Ness .

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College of Dentistry, University of Illinois, Chicago, IL, USA
Michael Miloro
Department of Oral & Maxillofacial Surgery, Louisiana State University Health Science, Shreveport, LA, USA
G. E. Ghali
Oral and Maxillofacial Surgery, The Ohio State University, Columbus, OH, USA
Peter E. Larsen
Department of Oral and Maxillofacial Surgery, University of Alabama at Birmingham School of Dentistry and Medicine, Birmingham, AL, USA
Peter Waite

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Ness, G.M., Blakey, G.H., Hechler, B.L. (2022). Impacted Teeth. In: Miloro, M., Ghali, G.E., Larsen, P.E., Waite, P. (eds) Peterson’s Principles of Oral and Maxillofacial Surgery. Springer, Cham. https://doi.org/10.1007/978-3-030-91920-7_5

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DOI: https://doi.org/10.1007/978-3-030-91920-7_5
Published: 09 August 2022
Publisher Name: Springer, Cham
Print ISBN: 978-3-030-91919-1
Online ISBN: 978-3-030-91920-7
eBook Packages: MedicineMedicine (R0)

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Impacted Teeth

Abstract

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Management of Impacted Teeth

Dental Extractions

Unerupted and Impacted Teeth: A Guide for Assessment and Treatment

Keywords

1 Incidence and Etiology

1.1 Impactions Other than Third Molars

1.2 Impacted Third Molars

2 Clinical Evaluation

Key Points

3 Treatment of an Impacted Tooth

3.1 Indications for Removal of Impacted Third Molars

3.1.1 Periodontitis

3.1.2 Pericoronitis

3.1.3 Orthodontic Considerations

3.1.4 Prevention of Odontogenic Cysts and Tumors

3.1.5 Root Resorption of Adjacent Teeth

3.1.6 Teeth Under Dental Prostheses

3.1.7 Prevention of Jaw Fracture

3.1.8 Management of Unexplained Pain

3.2 Contradictions to Treatment of Impacted Teeth

3.2.1 Extremes of Age

3.2.2 Compromised Medical Status

3.2.3 Surgical Damage to Adjacent Structures

Key Points

4 Surgery and Perioperative Care for Impactions Other than Third Molars

4.1 Exposure Versus Exposure and Bonding

4.2 Surgical Technique

4.2.1 Exposure and Bonding

4.2.2 Surgical Uprighting

4.2.3 Transplantation

4.2.4 Removal

Key Points

5 Surgery and Perioperative Care for Impacted Third Molars

5.1 Determining Surgical Difficulty

5.2 Technique for Removal

Tips

Key Points

5.3 Technique for Coronectomy

Key Points

5.4 Use of Perioperative Systemic Antibiotics

5.5 Use of Perioperative Steroids

6 Expected Postoperative Course

6.1 Bleeding

6.2 Swelling

6.3 Stiffness

6.4 Pain

Key Points

7 Complications Following Third Molar Surgery

7.1 Infection

7.2 Tooth Fracture

7.3 Alveolar Osteitis

7.4 Nerve Disturbances

7.5 Rare Complications

Key Points

8 Periodontal Healing After Third Molar Surgery

Key Points

Conclusion

References

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