Occlusal caries detection by using thermal imaging

To explore the applicability of thermal changes associated with dehydration for the detection and quantification of early tooth decay on occlusal surfaces using infrared imaging.

A total of 72 sites on 25 human teeth with various degrees of natural demineralisation have been used. Continuous evaporation of water inside the pores by pressurised air-drying is used to produce a thermodynamic response on the tooth surface. The temporal profile of the temperature will depend on the amount of water at each position and this is studied in relation to the degree of porosity and the lesion severity. The area enclosed by the time-temperature curve, DeltaQ, was then used for quantification of the lesion.

Maps of DeltaQ were obtained and histological examinations were performed for all teeth. A detection sensitivity of 77% and specificity of 87% for areas that are either sound or have a histological E1 lesion, 87% and 72% for areas that have either an E2 or EDJ lesion, and 58% and 83% for areas that have a lesion reaching the dentin was found using this method.

Thermal imaging shows the ability to discriminate, in vitro, between (a) either areas that are sound or with a lesion on the outer half of the enamel and (b) areas with a lesion extending to the middle of the enamel or deeper. However, variations of the temperature in an open mouth and humidity due to respiration can potentially challenge the ability of using this technique in vivo and this requires further investigation.