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Impaction occurs where there is prevention of complete eruption into a normal functional position of one tooth by another, due to lack of space (in the dental arch) obstruction by another tooth or development in an abnormal position.

M3 emergence normally occurs between 18-24 years but eruption is not uncommon outside these limits. However one or more M3 fail to develop in approximately 1:4 adults.

Impaction is an abnormality of development which predisposes to pathological changes such as pericoronitis, caries, resorption and periodontal problems. Cysts and tumours may also arise and can proceed to an advanced stage before the presentation of symptoms.

The guideline serves as a general guide to the management of impacted wisdom teeth. A risk assessment must be made for each specific clinical situation.

Presurgical assessment includes:

• History

• Clinical examination

• Diagnostic imaging - A dental panoramic tomographic (DPT) radiograph is generally sufficient for the management of M3. If this provides inadequate information or there is doubt alternative supplementary films may include intraoral periapical or oblique lateral views of the relevant areas plus in exceptional cases CT scanning to determine width greater precision relationship with the inferior alveolar canal.

Procedures for the management of M3

(not listed in order of preference)

• Surgical removal/excision of tooth/teeth:

• Operculectomy/surgical periodontics:

• Observation

• Surgical exposure: in selected cases in liaison with experienced orthodontic opinion

  • Surgical reimplantation/transplantation: in selected cases with co-operation of experienced orthodontic opinion.

In all cases, adequate instructions for post-treatment care and follow-up should be provided.

Anaesthesia

Surgical management may be carried out utilising:

1. Local analgesia (LA)

2. LA supplemented by intravenous sedation/analgesia/relative analgesia

3. General anaesthesia with airway protection achieved by endotracheal intubation or by laryngeal mask. This may be supplemented by local analgesia with vasoconstrictor to reduce haemorrhage and post-operative pain.

M3 procedures are generally suitable for day care management and it is recognised that treatment under local analgesia and sedation is associated with reduced complication rates.

Perioperative medication

Drugs prescribed will vary according to local and/or individual policies and also for specific patients. However as a guide those in common use include:

1. Conventional sedative/antiemetic premedication

2. Topical local anaesthetic cream at site of planned intravenous injection

3. Non steroidal anti-inflammatory drugs (NSAIDs) for analgesia and to reduce oedema and Trismus

4. Steroids (e.g., dexamethasone) to reduce oedema and Trismus

5. Antibiotics to reduce incidence of local osteitis /infection which may cause prolonged pain and swelling

Indications for removal

There has been disagreement about the appropriateness of removal of M3 unassociated with local pathology but there is no controversy about the value of removal when they are associated with pathological changes. One or more indications may be applicable in each case.

1. Overt or previous history of infection including pericoronitis. This indication will generally exclude transient/self-limiting 'inflammation' that may be associated with normal eruption of any tooth.

2. Unrestorable caries

3. Non-treatable pulpal and/or periapical pathology

4. Cellulitis, abscess and osteomyelitis

5. Periodontal disease: Impacted M3 associated with periodontally involved adjacent (usually second molar) teeth should be removed early as the disease may be irreversible by 30 years. This is particularly important in smokers where periodontal disease may progress rapidly.

6. Orthodontic abnormalities.

In some patients there may be an indication for removal of unerupted upper M3 before the commencement of maxillary retraction which would result in their impaction. However there is little rationale based on present evidence for excision of lower M3 solely to minimise present or future crowding of lower anterior teeth.

7. Prophylactic removal in presence of specific medical and surgical conditions. These include endocardial/valvular scarring/abnormality predisposing to bacterial endocarditis, organ transplants, alloplastic implants, chemotherapy/radiotherapy

8. Facilitation of restorative treatment including provision of prosthesis. Erupted M3 that can be maintained in a state of health may be retained as potential abutment teeth or for the maintenance of vertical dimension.

9. Internal/external resorption of tooth or adjacent teeth.

10. Pain directly related to M3: It is important to avoid an erroneous diagnosis of M3 related pain which may in reality be associated with the temporomandibular joint and masticatory musculature.

11. Tooth in line of bony fracture or impeding trauma management. On occasions, it is recommended that a M3 be left in situ at the time of initial fracture treatment. However, in most cases, removal is required at a later time.

12. Fracture of tooth

13. Disease of follicle including cyst/tumour

14. Tooth/teeth impeding orthognathic surgery or reconstructive jaw surgery

15. Tooth involved in/ within field of tumour resection

16. Satisfactory tooth for use as donor for transplantation

2.1 An impacted tooth which is totally covered by bone and which does not meet the above indications for surgery should not be removed; however it is generally recognised that it should be monitored periodically by clinical and radiographic examination (usually dental panoramic tomograph) because of the potential for change in position and/or development of pathology. The relative risk of retaining/delaying removal of impacted M3 should be considered in all cases. However surgical intervention in the absence of pathology is not usually indicated.

2.2 Consideration may be given to removal of an unerupted M3 by the third decade when a high probability of disease or pathology exists and when the risks associated with early removal are less than the anticipated risks of later removal (ie: increased morbidity). It is however emphasised that currently there is little evidence (based on randomised controlled trials) which differentiates those likely to become associated with disease from those unlikely to do so.

Two situations in which a high probability of consequential local disease is present are:

2.2.1 When a vertical or distoangular impacted tooth is at or close to the occlusal plane but the occlusal surface has been half or more covered for an extended period by soft tissue, pericoronitis is more likely

2.2.2 When a partly-erupted impacted M3 in mesio-angular or horizontal impaction has a contact point at or close to the amelocemental junction of the second molar the risk of caries of the latter is increased especially in the absence of a high standard of oral hygiene.

2.3 In a patient who has borderline indications for M3 excision and whose occupation will necessitate long periods away from civilisation (e.g. astronauts, nuclear submariners and explorers) consideration may be given to earlier rather than later removal. Results are awaited of prospective study undertaken by the UK Tri-Services, USA and Canadian Services Dental Corps and of a Swedish study of school children followed to age 26.

2.4 Opposing and contralateral teeth: If there are indications for removal of one M3 it is in the patient's best interests to determine whether the other three are present and if so whether their excision is required on the grounds of the clinical indications listed under items 1.4.1-16 above. It is suggested that removal of other teeth should only be carried out when treatment under general anaesthetic is planned or selected by the patient and where there is no evidence of increased risk of post-operative complications such as sensory nerve impairment. It is important to recognise that medico-legal cases have arisen in relation to complications arising from removal of such opposing and/or contralateral teeth.

Although, in a recent assessment of published reviews, two papers concluded that it may be appropriate to remove impacted M3 prophylactically, the methodological quality of these was deemed to be less satisfactory than others which found there to be lack of evidence to support this line of management. However, in the absence of good evidence to support prophylactic removal it seems reasonable at this time to avoid removal of 'pathology-free' impacted M3.