Assessing the need for computed tomography for lower-third-molar extraction: a survey among 322 dentists

Orthopantomograms (OPT) are used to assess the anatomical relationship between the inferior alveolar nerves (IAN) and the roots of third molars and the related risk of postextraction iatrogenic neurological lesions. When the risk is high, computed tomography (CT) or conebeam CT may be warranted. We investigated how dentists judged the need for CT from OPT to ascertain whether they comply with criteria of justification, appropriateness and optimisation in prescribing examinations involving radiation.

A total of 2,713 letters were sent to Italian dentists (Veneto region), inviting them to access an Internet Web site showing 20 OPTs and answer a questionnaire on the need for CT or periapical X-ray. The gold standards were CT images corresponding to the OPTs. The respondents' answers were rated for appropriateness and their tendency to over- or underprescribe CT.

The questionnaire was completed by 11.9% of the dentists contacted. The response rate was compatible with a Web survey. Their answers generally came close to the gold standard, achieving a mean appropriateness rating of 0.636 (range 0-1). An overlap between the mandibular canal and the third-molar root was the anatomical relationship most often noted. Recommendations for CT were proportional to the number of radiographic signs indicating a risk of inferior alveolar nerve injury. Periapical X-ray was considered useful by 54.9% of dentists not recommending CT. The main reason stated for not recommending CT was that it was unnecessary for the purposes of the extraction.

Our survey revealed a cautious approach among the professionals interviewed, who tended to overprescribe CT.