Sir, we wish to highlight a recent case of an intimate relationship between the roots of a lower second molar and the inferior dental canal (IDC) seen incidentally on a cone beam CT (CBCT) scan acquired to assess the relation of the lower third molar to the IDC prior to its surgical removal (Fig. 1). There are two lessons to be learnt: firstly the importance of reviewing the entire CBCT volume, not just the area of interest, for any incidental findings that might have a clinical relevance. The basic principles in the most recent guidelines of radiation protection clearly state that CBCT images must undergo a thorough clinical evaluation (radiological report) of the entire image dataset.1 They also state that all those involved with CBCT must have received adequate training. This ensures that relevant important information is gleaned. In this case, the area of interest was the third molar; however, the lower second molar exhibited a significant intimate relation to the IDC not only in distance, but so that the apical foramen opened directly onto the canal itself with loss of canal cortication clearly seen on CBCT.

Figure 1
figure 1

Intimate relationship seen between the roots of a lower second molar and the inferior dental canal

Full size image

Secondly, this potential intimate relationship would be an important consideration when an intervention is required such as endodontic treatment or surgical removal. Chong et al. described 55% of mandibular second molar apices having a distance to the IDC of ≤3 mm.2 In this case, as the foramen opened directly onto the canal, this would pose a significant risk to nerve injury from overzealous instrumentation and hypochlorite use. We encourage practitioners to consider the position of the IDC prior to root treating a lower second molar, and in some cases the use of CBCT prior to endodontic therapy may be justified.