Reliability of colour and hardness clinical examinations in detecting dentine caries severity: a systematic review and meta-analysis

Dental caries is the most common human infectious disease and is caused by microorganisms producing acids, resulting in changes in dental tissue hardness and colour. However, the accuracy and reliability of dentine colour and hardness as indicators for carious lesion severity has never been assessed in a systematic review. By applying strict criteria, only seven papers (five randomized control trials and two diagnostic studies) were considered for full text qualitative and quantitative assessment. Only three studies produced high quality evidence and only four articles were considered for meta-analysis, as these provided log(10) colony forming units (CFU) data from caries biopsies following colour and hardness clinical examinations. When comparing the amount of CFU isolated from carious biopsies from different colour and hardness categories, hardness clinical examination was found to be a statistically more discriminate test than colour clinical examination. Therefore, hardness clinical examination is more specific and reliable than colour to detect dentine carious lesion severity. Further large carefully designed clinical studies are needed to consolidate the findings of this systematic review.