The most common oral and maxillofacial surgical procedure in adolescents is excision of impacted third molars. Adolescent patients should be evaluated for third molars starting around age 16 years unless symptomatic at an earlier age. The dental examination should include panorex imaging to assess development, pathologic condition, and possibility of eruption versus impaction. Various classification systems are available to identify the position and difficulty of the proposed surgical procedure. Retained impacted teeth increase the patient’s risk of various morbidities including recurrent infection, damage to adjacent teeth, cysts and other lesions, and unexplained pain.
Key points
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Third molars are the most frequently encountered impacted teeth followed by maxillary canines and mandibular premolars
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CBCT imaging is commonly used to identify location and proximity to surrounding teeth, inferior alveolar nerve, and the maxillary sinus.
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Retention of impacted teeth increase long-term morbidities: periodontal disease, pericornitis, odontogenic cysts and tumors, root resorption of adjacent teeth, and unexplained pain.
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Postoperative morbidity is more frequent in patients beyond age 25 years.
Introduction/incidence/cause
Identification and proper management of impacted teeth should be a useful tool in the dentist’s armamentarium. Using evidence-based data to support recommended treatments and knowing proper classification systems can assist the dentist coordinate proper patient care. This article provides the pediatric dentist useful information to know when to obtain imaging, when to refer to an oral surgeon, and when to avoid treatment. Indications for impacted teeth treatment, contraindications, expected postoperative course, and potential complications are also reviewed.
A tooth is considered impacted when it fails to erupt within the expected time period and can no longer be reasonably expected to do so. Third molars are most commonly impacted and are extensively discussed; however, maxillary canines and mandibular premolars are the next most frequent impacted teeth. Of particular importance to pediatric dentists, true impaction of primary teeth is uncommon. Unerupted primary teeth likely are secondary to absent successor permanent teeth typically due to syndromes, rather than local processes, such as inadequate arch length. There are many syndromes associated with multiple impacted teeth, including but not limited to cleidocranial dysplasia, Down syndrome, and Gardner syndrome. The most common impacted supernumerary tooth is the mesiodens, followed by the supernumerary maxillary incisor, fourth molar, and mandibular premolar. Multiple impacted primary teeth should therefore alert the pediatric dentist to systemic consideration.
This article focuses on classification schemes to aid in communication, the role of imaging in treatment options, the timing of treatment, and indications and contraindications for extractions. With increased understanding, pediatric dentists can better anticipate difficult cases and ensure that patients are being treated within the proper time frame, using scrutinized literature to support these decisions rather than arbitrary personal experience. We also focus on pearls and pitfalls of the technique of third molar extractions, potential complications, and expected postoperative course.
Classifications
When describing impacted third molars, classification schemes can aid the pediatric dentist in communication. A commonly referred scheme is the Pell and Gregory classification, which is used to describe the position of impacted lower third molars. As depicted in Fig. 1 , classes A, B, and C relate the height of the impacted third molar’s occlusal plane to the mandibular second molar. In class A the impacted third molar’s occlusal plane is even with the second molar’s occlusal plane. In class B the impacted third molar’s occlusal plane is below the second molar’s occlusal plane but above the cement-enamel junction (CEJ) of the second molar. In class C the impacted third molar’s occlusal plane is below the CEJ of the second molar. Classes 1, 2, and 3 indicate the anterior-posterior relationship of the impacted third molar to the anterior ramus. Class 1 indicates there is sufficient space between the ascending ramus and second molar for eventual eruption. A class 2 impacted third molar’s distal crown is covered by bone of the ascending ramus, whereas a class 3 impacted third molar’s entire crown is totally embedded within the ramus. As the classification advances from 1 to 3 and from A to C, the extraction can be anticipated to be more difficult.
A more commonly used classification system, and potentially more practical, classifies the third molars based on the nature of the overlying tissue and directionality; this can be used to refer to maxillary and mandibular third molars. Soft tissue impacted teeth have a height of contour that is occlusal to the surrounding alveolus, but still remain covered by soft tissue. Partial bony impacted teeth have eruption impeded by soft tissue but have a height of contour below the surrounding alveolus. Similarly, complete bony impacted teeth are those that are completely embedded within bone. Last, Winter classification is used to describe the directionality of impacted third molars in relation to the vertical axis of the adjacent second molars: mesial angular, distal angular, horizontal, vertical, etc.
Imaging
Clinical examination and adjunct imaging can provide diagnosis of an impacted tooth. Routinely, a panorex is initially provided to evaluate the position and stage of development of the impacted teeth. Sometimes, an in-office dental cone beam computed tomography (CBCT) is completed to provide a 3-dimensional analysis of impacted tooth position as it relates to vital structures. In the case of impacted mandibular third molars, the CBCT will allow for evaluation of these teeth in relation to the inferior alveolar nerve, as well as thickness of adjacent lingual cortex. Panorex findings suggesting close approximation of mandibular third molars include darkening, narrowing, and deflection of the third molar root and diversion of the inferior alveolar canal. Of these findings, however, darkening of the third molar root caries the highest relative risk of inferior alveolar nerve damage. The information provided by a CBCT can often dictate treatment, including extraction versus coronectomy. Studies have shown that a preoperative CBCT influenced the treatment plan for 12% of cases. Other findings in CBCTs can change treatment plans other than coronectomy versus extraction of mandibular third molars. Severe external resorption observed in CBCTs was the main decisive factor for removing the second instead of third molar when considering maxillary third molar preoperative evaluation.
CBCT imaging also has a role in evaluating other impacted teeth, to aid in surgical access. Knowing whether an impacted maxillary canine is buccal or lingual to root apices of adjacent erupted teeth allows the surgeon to determine whether to access the impacted tooth from the palate or buccal vestibule. Also, the CBCT can determine feasibility of eruption once impacted canine is exposed. Studies have shown a correlation of panorex findings and CBCT-confirmed labial or palatal tooth positioned. For instance, if the panorex shows a horizontally positioned maxillary canine, the CBCT will indicate that the tooth is on the palate. It is suggested to obtain a CBCT to confirm.
Timing of treatment
Appropriate treatment of impacted teeth can be guided by dentists, with particular emphasis placed on timing of treatment. Ideal timing allows for easier surgery, which in turn allows for improved patient outcomes and recovery. In 2007, the American Association of Oral and Maxillofacial Surgeons created a task force to review literature with regard to impacted third molar removal, releasing the “White Paper on Third Molar Data.” The data released in this paper guides official treatment recommendations and provides proper indications for third molar removal. Of particular importance to pediatric dentists are conclusions from “The Effects of Age on Various Parameters Relating to Third Molars.” Multiple studies found that postoperative morbidity following third molar removal is higher in patients older than 25 years (pain, swelling, food impaction, purulent discharge). Postoperative periodontal defects, namely increased pocket depths, occur twice as often (51%) in patients older than age 26 compared to patients younger than 25. Caries in erupted third molars increases in prevalence with increasing age. After age 25, it is apparent that all potential surgical risks associated with third molar surgery have an increased incidence. A study of 4004 patients showed a 1.5 times likelihood of a complication if the patient had third molars removed at age greater than 25 years with generalized increasing risks with age through 65 years. The document identified a germectomy as the removal of an impacted tooth that has one-third or less of root formation and a discernible periodontal ligament. Although dental development varies patient to patient, studies with patients aged 9 to 17 years reported significant decreases in alveolar osteitis, nerve involvement, second molar damage, and infection.
Non–third molar impacted teeth
Pediatric dentist providers also must be prepared for the management and timing considerations for non–third molar impactions. Surgical uprighting of a mesioangular impacted mandibular second molar is often required to aid in eruption. This procedure will usually require removal of the adjacent impacted third molar. It is not necessary to remove buccal bone or place a bracket. The procedure is best performed after two-thirds of root development is completed. At this stage, the risk of root fracture is minimal. Although the procedure has been performed when root development is complete, the incidence of subsequent pulpal necrosis or calcification is increased. ,
Another non–third molar impacted tooth consideration is the surgical exposure and often bonding of impacted maxillary canines. Given the eruption sequence, these teeth often require additional procedures to facilitate eruption. For non–third molar impacts, the most desirable treatment outcome is eruption of the tooth into its normal, functional position in the dental arch. The most common example of this is the impacted maxillary canine. Eruption is often facilitated by a combined surgical and orthodontic approach, exposure and bond. This procedure includes surgical access to the impacted canine, including bone removal, but not to the level of the CEJ. Once accessed, an orthodontic bracket and chain are bonded to the impacted tooth. Orthodontic forces are then applied to facilitate eruption. Exposure should be carried out conservatively so that only enough bone and soft tissue are removed to place an orthodontic bracket. Damaging effects to the periodontium have been shown to be more frequent with exposure of the CEJ.
Indications
Impacted teeth that are not able to function represent potential adverse outcomes. Given the above-mentioned White Paper conclusions, impacted third molars should be removed prophylactically to avoid pathologic problems that result from impacted teeth, including periodontitis, pericoronitis, odontogenic cysts and tumors, root resorption of adjacent teeth, jaw fracture, and unexplained pain. One critical indication for extraction is to prevent pathologic condition. Curran and colleagues studied 2646 lesions involving impacted third molars and concluded that 33% of those lesions showed significant pathology. The most common pathologic condition was dentigerous cyst (28.4%), followed by odontogenic keratocyst (3%), odontoma (0.7%), and ameloblastoma (0.5%).
Contraindications
One of the most controversial issues regarding impacted mandibular third molars is their role in postorthodontic therapy anterior crowding. Although this is a common thought process among practitioners, the data do not support this claim. Anterior incisor crowding is associated with deficient arch length, not the presence of impacted teeth. However, it can be assumed that patients who recently finished orthodontic therapy can still stand to benefit from third molar removal given the anticipated age of such patient and prevention of the aforementioned potential adverse outcomes of impacted teeth. Prophylactic extractions of asymptomatic impacted third molars in individuals older than 35 years, in particular those with other associated risk factors (close approximation to the inferior alveolar nerve, anticipated difficult extractions given Pell and Gregory classification), are contraindicated.
Armamentarium
The appropriate armamentarium is a necessity if the practitioner plans to surgically treat impacted teeth. Fig. 2 shows the basic tray setup for surgical extraction of impacted teeth. Appropriate application of each of these standard instruments is beyond the scope of this article; however, specialized instruments in Fig. 3 can be further discussed. From left to right, the instruments are a spade elevator, a 46R elevator, a crane elevator, and a 69W chisel. The spade elevator is of particular use in areas with tight interproximal purchase points. While maintaining palatal pressure, the spade can be wedged mesial to maxillary third molars to aid in elevation. The advantage of a 46R elevator is the offset shank that allows the provider to achieve an appropriate angle to elevation. A crane elevator is of particular use when a purchase point is created in a tooth; it can also be applied to the pulp chamber following sectioning mandibular third molars to facilitate delivery. Last, the 69W chisel can function to remove buccal bone overlying a maxillary third molar if the aforementioned bone is too dense for a periosteal to remove enough bone for evaluation and purchase of impacted maxillary third molars.
