Most patients attending hospital with impacted teeth are referred because of pain and infection, associated with partially erupted teeth (Fig. 5.2); however, many impacted or displaced teeth are unerupted and asymptomatic and therefore an incidental finding following radiographic examination. Occasionally, unerupted wisdom teeth, in the absence of any obvious infection, can give rise to discomfort (often described by patients as ‘pressure’ at the back of the mouth). It is important to exclude other possible causes such as temporomandibular joint pain and pulpitis/periapical abscess from another tooth.

Fig. 5.2 Pericoronitis affecting a partially erupted wisdom tooth. Note the soft-tissue erythema.

Intraoral anatomical factors that may influence surgical access include size of the tongue and degree of mandibular opening. The position of the impacted wisdom tooth should be noted (unerupted, partially erupted or erupted but non-functional), together with any signs of infection (e.g. caries, pericoronitis). Probing the distal aspect of the second molar will confirm whether the buried tooth is in communication with the mouth.

Pericoronitis

Pericoronitis may be defined as an infection involving the soft tissues surrounding the crown of a partially erupted tooth. It is usually caused by streptococci and anaerobic bacteria, and may be classified clinically as acute (the features of acute inflammation developing over hours to days, possibly with systemic involvement) or chronic (some redness and/or discharge of pus with few acute symptoms, lasting over weeks or months). It may be associated with poor oral hygiene, stress and upper respiratory tract infection.

Signs and symptoms of pericoronitis include swelling, soreness, erythema of the overlying soft-tissue operculum, trismus, facial swelling, raised temperature, regional lymphadenopathy and general malaise. The disorder may be precipitated by trauma from an over-erupted upper wisdom tooth or entrapment of food debris and bacterial infection of the operculum.

Pericoronitis may be treated by removal of the upper wisdom tooth (if this is traumatizing the operculum overlying the lower wisdom tooth), irrigation under the operculum with chlorhexidine, the careful application of a medicament such as trichloroacetic acid beneath the operculum, hot salt-water mouthwashes and analgesics (e.g. ibuprofen). If there is systemic involvement, then antibiotics are indicated (e.g. amoxicillin or metronidazole). Severe infections may require admission to hospital as they can spread through the fascial planes and compromise the airway (see Ch. 7).

Clinical examination assesses the wisdom tooth and excludes other causes of symptoms:

• degree of eruption of the wisdom tooth, and any associated infection

• caries or restorations in the third molar and distal aspect of the adjacent tooth

• periodontal status

• any other disease, including temporomandibular joint problems.

Radiological assessment

The radiographic examination of choice is a panoramic radiograph such as an OPT (Fig. 5.3), although periapical or oblique lateral views of the mandible may be taken as an alternative. When referring a case for treatment all recent relevant radiographs should be included to avoid further exposure to ionizing radiation.

Fig. 5.3 A mesioangular impacted lower third molar on the right and distoangular impaction on the left. (Note the unerupted third molars in the maxilla.)

Management of pericoronitis

• Local irrigation, hot salt-water mouthwash/chlorhexidine mouthwash

• Antibiotics if signs of spreading infection

• Analgesics (e.g. ibuprofen)

• Extract upper 8 if traumatizing lower operculum

• Remove lower 8 when infection settled

The following radiological assessment of the lower third molar should be made:

• orientation (Fig. 5.4a), with particular reference to the distinction between vertical and distoangular

• depth of the third molar below the occlusal plane (Fig. 5.4b)—the deeper the tooth the more difficult the surgery

• crown size

• follicular width

• root morphology (Fig. 5.5)—number, length, shape; fused or separate, apex curved or bulbous; loss of periodontal width—ankylosis?

• relationship to the inferior dental nerve canal (see Fig. 5.1)

• condition of crown of third molar and adjacent tooth—e.g. caries (Figs. 5.5, 5.6)

• the ratio of the distance between the distal aspect of the lower second molar and ascending ramus compared with the mesiodistal diameter of the third molar (Fig. 5.4c) (a ratio greater than 1:1 is associated with easier access)

• depth of bone between the tooth and the lower border of the mandible.

Fig. 5.4 (a) Orientation of third molar: (i) towards second molar; (ii) away from second molar. (b) Increased depth of crown of right third molar (i) from occlusal plane compared to left third molar (ii). (c) Distance between anterior ramus and distal aspect of second molar compared with width of third molar crown: increased surgical access for right third molar (i) but reduced access for left third molar (ii).

Fig. 5.5 Marked curvature of the roots of the lower third molars. Note gross caries affecting the lower left third molar.

Fig. 5.6 A vertically positioned abscessed lower right third molar.

Clinical assessment

• Complaint: pain; exclude other causes such as temporomandibular disorder, pulpitis/abscess of other teeth

• Previous medical history: for example, drug therapy

• Dental history: difficult extractions, postoperative infection or bleeding, etc.

• Extraoral features: lymphadenopathy, trismus, swelling

• Intraoral features: pericoronitis/trauma from upper 8, eruption status of lower 8, caries in 8 or 7 or pocketing

• Tests: panoramic radiograph, systemic temperature if other signs of infection

Diagnosis

From the clinical and radiographic examination, a decision on whether to remove the impacted third molar needs to be made (discussed below). If there is pain/discomfort, the cause (e.g. caries) should be identified and treated. Trauma to the operculum of the lower third molar may be eliminated by either extracting or grinding down the cusps of the maxillary third molar. Pericoronitis may require irrigation with chlorhexidine, antibiotics (if systemic involvement) and analgesics. The decision whether to prophylactically remove non-diseased third molars is discussed below in greater detail, although in general their removal is not indicated because they are usually symptomless.

Patient preference should be taken into account when deciding on the form of anaesthesia: local anaesthesia, intravenous sedation, general anaesthesia.

Reasons for removal

The US National Institutes for Health (NIH) consensus on indications for removing wisdom teeth (published in 1980) (see also SIGN 2000 and NICE 2000) listed the following points as definite indications for removal:

• any symptomatic wisdom tooth, especially where there has been one or more episodes of infection such as pericoronitis, cellulitis, abscess formation or untreatable pulpal/periapical pathology (Fig. 5.6)

• where there are caries in the third molar and the tooth is unlikely to be usefully restored or caries in the adjacent second molar tooth which cannot satisfactorily be treated without the removal of the third molar (Figs. 5.5, 5.7)

• periodontal disease due to the position of the third molar and its association with the second molar tooth (Fig. 5.8)

• dentigerous cyst formation or other related oral pathology, such as ameloblastoma or keratocyst (Fig. 5.9)

• external resorption of the third molar, or of the second molar where this would appear to be caused by the third molar.

Fig. 5.7 Mesioangular impacted lower left third molar with distal caries on adjacent molar. Note horizontal impacted right third molar.

Fig. 5.8 Severe periodontal bone loss between an impacted third molar and carious second molar.

Fig. 5.9 Dentigerous cyst surrounding impacted third molar.

Other indications for removal include:

• orthodontic abnormalities—for example, tooth must be removed to create space in the maxillary or mandibular arch. There is, however, little evidence that the removal of third molars in the lower arch will prevent, limit or cure imbrication of the lower anterior teeth

• removal of the third molar prior to orthognathic surgery

• fracture of the mandible in the third molar region. If the tooth is not helping to splint the fracture, then it should be removed.

Contraindications to removal

Removal is not advisable:

• for patients whose unerupted or impacted third molars would be expected to erupt successfully and have a functional role in the dentition

• for those with no history or evidence of pertinent local or systemic pathology

• where the medical history makes the removal of third molars a greater risk to the overall health of the patient than the benefits would justify

• where there is an increased risk of significant complications, e.g. a high risk of permanent inferior alveolar nerve damage or fracture of the mandible (Fig. 5.10).

Fig. 5.10 A severely resorbed mandible. The horizontal third molar and impacted second molar occupying the full depth of the mandible show an increased risk of jaw fracture. (Note retained roots in the maxilla.)

There is no strong indication to extract asymptomatic contralateral or unerupted maxillary teeth simultaneously if they are disease-free.

Informed consent for the removal of wisdom teeth

Prior to any surgical procedure the patient should be made aware of the benefits and risks of treatment as well as the possible sequelae of other options (including no treatment).

Thus patients should be warned to expect pain, swelling, bruising, difficulty in opening the mouth and possible damage to the lingual or inferior dental nerve (‘numbness in the tongue or lip’). Effects on ‘quality of life’ issues that may occur (interference with eating, socializing) and time off work, if applicable, should also be mentioned.

Factors influencing the decision to refer to a specialist include:

• operation likely to take longer than 30–40 minutes

• patient refuses local anaesthesia and requests a general anaesthetic

• patients who are very anxious

• procedure considered too complex for local anaesthesia

• presence of a relevant medical condition—e.g. previous radiotherapy to the jaws, haemorrhagic disease.

Type of impaction

Lower third molars may be impacted mesioangularly (Fig. 5.3, right), vertically (Fig. 5.6), distoangularly (Fig. 5.3, left), horizontally (Fig. 5.10) or ectopically placed.

One simple method of determining the type of impaction involves comparing the distance between the roots of the third and second molar (a) with the distance between the roots of the second and first molars (b) (Fig. 5.11). If (a) is greater than (b) it is a mesioangular impaction; where (a) is less than (b) it is a distoangular impaction; where (a) is equal to (b) it is a vertical impaction. If the first molar is missing, the impaction can be determined by comparing a line drawn down the long axis of both the second and third molars: if parallel, it is vertical; if lower 8 leans towards lower 7 it is mesioangular; if the lower 8 long axis diverges from that of the 7, then it is a distoangular impaction.