Effects of diagnostic threshold and overlapped approximal surfaces on reported caries status.

The aims of this study were to examine the influence upon reported caries status of: 1) employing different diagnostic thresholds and 2) using differing conventions for treating approximal surfaces which appeared overlapped on posterior bitewing radiographs. Caries prevalence data from a group of 211 Scottish schoolchildren aged 5-15 yr studied during a trial of elective temporary tooth separation in general dental practice in Scotland were used. In this "moderate" caries group, values for dmft/DMFT rose significantly (P less than 0.001) when the D1 diagnostic threshold (all grades of lesion accepted) was applied in comparison with the D3 threshold (only caries into dentine recognised); dmft increasing from 3.9 to 5.4 and DMFT increasing from 1.7 to 4.7. This demonstrated that an over-optimistic impression of overall caries levels may be given when only the D3 threshold is used uncritically. In this study the status of approximal surfaces which were overlapped on bitewing radiographs was assessed by direct clinical examination using the temporary elective tooth separation technique. The investigation showed that, for this juvenile population, most (81.8% mesial, 93.1% distal) overlapped approximal surfaces were sound. Significantly more mesial than distal surfaces were found to be overlapped.