Methods of determining the relationship of the mandibular canal and third molars: a survey of Australian oral and maxillofacial surgeons

BACKGROUND: Surgical extraction of third molars is one of the most common oral and maxillofacial surgical procedures performed and may have a number of associated complications. One of these complications is inferior alveolar nerve (IAN) dysaesthesia or impairment of sensory perception (including paraesthesia and/or anaesthesia). Previous studies assume that most clinicians use various combinations of nine radiologic criteria on panoramic radiographs as indicators of the relationship and, therefore, predictors of the risk of postoperative dysaesthesia. Our study assessed both the current radiologic modalities and assessment criteria used by Australian oral and maxillofacial surgeons when determining the proximity of mandibular canal to third molars. METHODS: A survey of all surgeon members of the Australian and New Zealand Association of Oral and Maxillofacial Surgeons (ANZOMS) practising in Australia was undertaken. RESULTS: Of the 105 questionnaires sent to surgeons, 72 responses (68 per cent) were returned. All surgeons reported using the panoramic radiograph but only 25 per cent considered it sufficiently accurate in determining the relationship between the mandibular canal (MC) and the third molar root, while 61 per cent of surgeons use CT for this purpose but the average frequency of use was very low (five per cent). This study also revealed that the nine radiologic criteria on a panoramic radiograph are used to varying extents by Australian surgeons. Nearly all surgeons use 'change in MC direction' and 'MC narrowing' to determine and close relationship. Thirty-one per cent used superimposition of the MC and the root of the third molar alone and 24 per cent used appearance of contact of the root with the MC alone in the absence of any other radiologic criteria to indicate close or intimate relationship. CONCLUSION: Further research is required to determine the accuracy and observer agreement or reliability of using the nine panoramic characteristics, to determine this relationship and whether the presurgical determination of proximity and position (buccal or lingual) of the canal utilizing CT has any usefulness in determining the surgical protocol or affect on postoperative morbidity.