Criteria for caries removal at the enamel-dentine junction: a clinical and microbiological study.

In the UK cavity preparation at the enamel-dentine junction (EDJ) is considered complete when all soft and/or stained tissue is removed. The aim of the present work was to link the clinical criteria of dentine consistency and dentine colour with the microbiological status of the tissue. Cavities were prepared in 564 teeth. Under rubber dam, access to the EDJ was gained and the sample sites selected (n = 847). Their consistency was noted as hard or soft and wet or dry when probed. The colour of the site was noted as stain-free or stained. Dentine was sampled using a round bur. After microbiological processing the total anaerobic count and counts of mutans streptococci and lactobacilli were expressed as log10 [CFU per sample]. Soft sites harboured significantly more bacteria than hard sites (P < 0.001). Soft and wet sites harboured significantly more bacteria than soft and dry sites (P < 0.001). Stained and hard sites harboured more bacteria than stain-free and hard sites (P < 0.05) but this difference was not considered to be clinically relevant. The relatively simple clinical criteria used here correlated significantly with the microbial findings. All soft dentine must be removed at the EDJ to ensure minimal infection of the underlying hard dentine. However, it may not be necessary to continue preparation until the EDJ is also stain-free.