MICROBIOLOGICAL VALIDATION OF ASSESSMENTS OF CARIES ACTIVITY DURING CAVITY PREPARATION

The operative management of primary and secondary caries assumes that all discoloured tissue at the enamel-dentine junction (EDJ) represents active disease and this is removed to arrest the carious process. Thi s study aims to establish clinical criteria to differentiate between a ctive and arrested caries at the EDJ using microbiological assessment of dentine samples to verify its clinical status. Radiographs were ava ilable for posterior teeth. Cavities (n = 205) were prepared under rub ber dam. After gaining access, areas of the EDJ were chosen and assess ments made of consistency (soft, medium, hard), colour (dark brown, mi d-brown, pale) and moisture content (wet, dry). Dentine was removed by using a No. 3 round burr and placed in 1 ml of bacteriological cultur e broth. This sampling procedure was repeated at the same site once du ring cavity preparation and again when the cavity was judged as fully prepared. Samples were vortexed, diluted and cultured to give viable c ounts of the total anaerobic microflora, mutans streptococci and lacto bacilli; viable counts were expressed as log10 (CFU per sample +1). Re sults showed no significant differences between the microflora of prim ary and secondary caries. The number of bacteria recovered diminished significantly as cavities were completed. Initial samples from soft an d wet lesions harboured significantly more bacteria, lactobacilli and mutans streptococci than samples from medium, hard or dry lesions. Les ions visible on radiographs harboured more bacteria, including lactoba cilli and mutans streptococci, while dentine colour was not discrimina tory. In conclusion, the relevant clinical criteria for the diagnosis of infected dentine at the EDJ were visibility on radiographs, soft le sions and wet lesions.