Oral Health Group
Feature

ORAL SURGERY: The Sick Wisdom Tooth

July 1, 2001
by Stephen Ho DDS, Daisy Chemaly DMD; Bohdan Kryshtalskyj, Bsc., DD


Symptoms related to unerupted mandibular third molars are the most common problems encountered in the oral health services. An unerupted tooth refers both to teeth that are impacted and to teeth that are in the process of erupting.1 The tooth becomes impacted because eruption is prevented by adjacent teeth, dense bone, or excessive soft tissue.1 According to Venta, mandibular third molar teeth often remained completely unerupted or partially erupted (84%) rather than being erupted (16%) which indicates that there is a substantial risk of the development of disease and pathoses.2

The United State National Institute for Dental Research sponsored a Consensus Development Conference in 1979 that had a mandate to “reach agreement on when and under what circumstances third molar extraction is advised.”3 The conference produced a number of well-defined pathologic indications for extractions: infection, cysts, tumours, non-restorable carious lesions, and destruction of adjacent teeth and bone. A consensus was not reached on the directions for removal of asymptomatic third molars without evidence of pathologic change. The controversy still remains to this day.

A study asked general practitioners and oral surgeons to judge the need for removal of 36 asymptomatic impacted wisdom teeth.3 The radiographic records were duplicated so that the reliability of the judgements could be assessed. Each dentist was asked to estimate the strength of the indication for extraction and, if the teeth were not extracted, the probability of development of pathology in general. The results were that “intraexaminer reliability was high, this study confirms that the judgement to extract asymptomatic impacted third molars is not made solely on the basis of cognitive factors.”4 This study generated a conclusion that echoed other previous studies that both oral surgeons and dentists do not have the basic knowledge needed to make the correct decision when faced with a task involving a range of choices. Rather than using the appropriate statistical approach, they guess.3

The goal of this paper is to review the host of pathological conditions that can develop from the retention of asymptomatic impacted wisdom teeth.

PERICORONITIS

Pericoronitis is an infection of the soft tissue around the crown of a partially impacted tooth and is caused by the normal oral flora, which is a complex, variable mixture of obligate and facultative anaerobes mainly of Peptostreptococcus, spirochetes, Fusobacterium and Bacteroides.5,6 Kay found that pericoronitis was greatest in the age range 16-30 years with a maximum incidence among patients aged 21 to 35 years. Pericoronitis thus seems to be an event that usually occurs during the third decade of life.3,6 Knutsson et al found that pericoronitis was the most frequent pathologic entity among third molars in all positions, in particular among third molars in distoangular and mesioangular positions.7 Pericoronitis can arise if the patient experiences a mild, transient decrease in host defenses, secondary to minor trauma from a maxillary third molar, or entrapment of food under the operculum.5,6,7 Pericoronitis can present as a very mild infection or as a severe infection requiring hospitalization. In its mildest form, it is a localized tissue swelling and soreness. This form is treated by irrigation with hydrogen peroxide and curettage by the dentist, followed by home irrigations by the patient. Hydrogen peroxide removes bacteria with its foaming action and reduces the amount of anaerobic bacteria by releasing oxygen into the usually anaerobic environment.5,6 For patients who have mild facial swelling, mild trismus secondary to inflammation extending into the muscles of mastication, and a low-grade fever, the dentist should consider the administration of antibiotics along with irrigation and extraction of the tooth in question.5 Penicillin is still the drug of choice because it is narrow spectrum, inexpensive, non-toxic and exclusively bactericidal against all common major pathogens of odontogenic infections.8,9 Erythromycin and clindamycin have been prescribed to patients who are allergic to penicillin. Erythromycin is not effective against Fusobacterium. It could be recommended against mild or moderate infections in people with penicillin allergies but may not be suitable in more severe infections. In addition, erythromycin is not recommended in cases in which penicillin fails.9 Clindamycin is a powerful antibiotic against strict anaerobes, including B-lactamase production. Clindamycin is recommended for the treatment of severe infections, or in cases in which penicillin therapy has failed.8,9 Pericoronitis can lead to serious fascial space infection. The patient who presents with severe trismus (maximum opening < 20mm), fever, malaise and facial swelling, he should be referred to an oral and maxillofacial surgeon for proper management or a possible admission to a hospital.3 Indresano et al stated that deep space infection was principally due to impacted mandibular third molars in which the preoperative diagnosis is pericoronitis in 67.7% of the cases. Accordingly, these teeth should be removed if there is a history of recurrent infection or clinical evidence indicating eruption difficulty.1,2

SPACE INFECTION

Odontogenic infections are relatively common and are usually mild and easily treated with antibiotics and local surgical intervention. However, some odontogenic infections are very serious and require aggressive management. Even after the advent of antibiotics and improved dental health, some odontogenic infections are still causing death. Berge found that the estimated incidence rate for serious infections related to third molars was 0.016 cases per year per 1000 patients at risk.10 These infections erode into fascial spaces directly, which causes a fascial space infection. These spaces are lined with fascia that can be eroded or distended by purulent exudate.2 Apart from local spread by direct extension, lymphatic and hematogenous dissemination may occur. Hang et al found alpha-hemolytic streptococci and bacteroides to be the most predominantly isolated organisms in orofacial abscesses.10 Apical abscesses of the third molars can discharge into the submandibular space, and from there extend into the parapharyngeal space. From the latter, infection may spread inferiorly via the fascial planes into the mediastinum through the prevertebral space.11 It has also been reported that in several patients, a pericarditis developed which is a result of direct spread from the mediastinum or the pleural space. Many complications could arise from these infections such as: 1) the possibility of upper airway obstruction due to the displacement of the posterior pharyngeal wall into the oral pharynx, 2) the rupture of the parapharyngeal space abscess, with aspiration of pus into the lungs and possible asphyxiation, 3) and a severe infection in the thorax if the infection has spread to the mediastinum. Fascial space infections require extensive and aggressive treatment. The management of these infections should include: 1) medical support of the patient (i.e. airway maintenance…), 2) administration of proper antibiotics in appropriate dosages, 3) surgical removal of the source of the infection, 4) surgical drainage of the infection and 5) constant reassessment of the resolution of the infection.2,3

MYOFASCIAL PAIN

Occasionally, patients may present complaining of pain localized in the region of impacted third molars or they may report radiation of pain from the retromolar region of the mandible for no obvious organic reasons. In these patients, it is important to perform a proper work-up to identify any other source of the myofascial pain. Careful history taking, thorough examination and arrangement of appropriate special tests are essential to exclude an organic pathology. This, sometimes, may require referral to appropriate specialists within the dental profession or others, such as neurologists or psychiatrists.12 Subsequently, if conditions such as myofascial pain dysfunction syndrome and temporomandibular joint disorder are excluded and if the patient has an unerupted inferior third molar, removal of the tooth sometimes results in resolution of the pain.2 However, it should be emphasized to the patient that this might not resolve the myofascial pain.3

ANGLE FRACTURE

The mandible is the most common of the facial bones to fracture.13 Mandibular fractures are frequently located in the angle region. The increased frequency of mandibular angle fracture relative to other locations has been attributed to the presence of mandibular third molars.13,14 A proposed explanation for this relationship that mandibular third molars weaken the mandible by decreasing the cross-sectional area of bone.13,14 Reitzik et al reported that monkey mandibles containing unerupted third molars fracture at approximately 60% of the force required to fracture the mandible containing erupted third molars.14,15 In addition, Tevepaugh and Dodson demonstrated that patients with fractured mandibles and third molars are 3.8 times more likely to have an angle fracture than patients without third molars. The study conducted by Ma’aita et al has shown that the tooth position or angle increases the risk of angle fracture in patients with third molars. Patients with a level C, level 3 impacted third molar, according to the Pell and Gregory classification, may have an increased risk for an angle fracture compared with a patient with a level A, level 1 third molar. In addition to these results, Ma’aita et al showed that the peak incidence of angle fracture is found in patients between the ages of 20 and 29 years, and that the incidence is increased by vertical and distoangular types of impaction. If the jaw fractures through the area of an impacted third molar, the tooth is removed before fracture reduction and intermaxillary fixation is applied.16

ROOT RESORPTION

The possibility of damage to teeth adjacent to impacted third molars is often cited as a reason for their removal. There are two theories that exist for the pathogenesis of root resorption. The first is that the impacted tooth is exerting a mechanical force on the proximal root in its eruption path.17 The other cites the possible role of the reduced enamel epithelium and dental follicle in the secretion of cytokines leading to osteoclast recruitment and root surface resorption.18 Studies have failed to exactly quantify the incidence of root resorption but all seem to indicate that it is rare.19 Damage has been found to positively correlate with the age of the patient and the angulation of the third molar tooth.20 Others have found evidence of root resorption to exist on teeth that radiographically seem to be unaffected.21 It is generally accepted that only extensive resorption can with certainty be identified by the radiograph.22,23

CYSTS AND TUMORS

The development of cysts and tumors around impacted third molars is unquestionably a valid reason for the removal of the tooth. The incidence pathological development has been and continues to be extensively studied in the literature. While numbers have varied depending on the author, the recently reported 2.31% incidence of cysts and 0.79% incidence of tumors by Guven et al. are in line with those found in the past.24 Histologic studies have further revealed that as much as 34% of “radiographically normal” follicles from impacted, asymptomatic wisdom teeth can show squamous metaplasia suggestive of cystic change equivalent to that found in dentigerous cysts.25 The threat of neoplastic change to ameloblastoma or odontogenic carcinoma of an odontogenic cyst has been well documented.27 Despite this infrequent occurrence, the ones that do transform comprise a surprisingly high percentage of total neoplastic pathology. It is reported that approximately 50% of central mucoepidermoid carcinoma are associated with a cyst or an impacted tooth.28 This is just a part of the total 22-25% of odontogenic carcinomas of all varieties that arise from dentigerous cysts.27,28 Clinicians need to share these numbers with their patients.

When the decision to “wait and see” is adopted, the patient’s cooperation is vitally important to a regular follow-up routine. Some authors have commented on the rate at which some lesions have arisen from asymptomatic follicles, prompting them to suggesting a radiographic cut off period of 12-18 months.29 In the face of questionable patient compliance, the threshold for removal of asymptomatic impacted wisdom teeth needs to be lowered.

CONCLUSION

In the face of overt infection or pathology associated with the third molar tooth, all practioners can reach a consensus for the need of their removal. It is the asymptomatic impacted tooth that challenges our skills of clinical judgement and demands that we have a commanding knowledge of possible associated pathology. We must think of the normal post-operative sequellae and risks of surgery and how they are framed by the patient’s age and systemic health. The physical relationship of the tooth to other anatomical structures should also enter our decision-making analysis. Dentists and Oral Surgeons agree that decisions to extract teeth should not be made lightly, but inherent in this statement is another with equal impact and importance: the retention of teeth asymptomatic teeth needs to approached with similar caution.

Although the overall incidence of pathological development is low, we know that when it does occur, the impact is often significant. The development of this pathology often occurs later in life, when the removal of these teeth carries with it prolonged recovery and an increased incidence of risks such as infection and paresthesia. Furthermore, the literature suggests that lesions can develop over a short period of time and that radiographs need to be current. When the decision to retain a tooth is made, the dentist and patient need to reach an understanding that regular radiographic monitoring with adequate views of the teeth is imperative. Since most dental offices lack the ability for taking panoramic radiographs, to obtain an adequate radiographic survery requires both patient compliance and operator skill.

Our response to the very common question “should I have my wisdom teeth removed, they don’t bother me?” needs to be re-evaluated. We must communicate with our patients the risks and commitment associated with their retention.

Stephen Ho DDS, is an Oral and Maxillofacial Surgery Resident, University of Toronto. Daisy Chemaly DMD, is a Dental Intern, Toronto General Hospital. Bohdan Kryshtalskyj, Bsc., DDS, MRCD(C), is an Oral and Maxillofacial Surgeon in Toronto and Simon Weinberg, DDS, FRCD(C), FICD, is Oral Health’s editorial board member, Oral Surgery.

Oral Health welcomes this original article.

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