Human Enamel Emittance for Thermal Imaging

Objectives: Thermal Imaging is a non-ionising, non-invasive, non-contact imaging technique which is gaining momentum as a diagnostic aid in Rheumatology Medicine and Dental Caries detection.
Emittance is a ratio of radiation from an object, compared to radiation from a Blackbody, at a specified temperature. Emittance of an object is desirable to enable accurate temperature-measurement for assessment with thermographs.
Aim:- To present a practical method to establish emittance of human enamel for in-vitro and in-vivo thermography.
Methods: An ethically-sourced human third-molar was sliced bucco-lingually into 1mm slices (Accutom-5) and refrigerated in vials with distilled water. Slices were viewed with a FLIR SC305 Thermal Camera (x4 lens, reflected-apparent-temperature 27.2^oC, humidity 50%) on a hotplate (30^oC) until thermal equilibrium was reached in a novel, purpose-built, thermally-stable environment (22^oC±0.1^oC) with macro- and micro-control via thermal sensors. 3M Black Super 33+ Tape was used as an emittance reference point (0.96). Two slices were viewed twice, with three consecutive viewings on each occasion. ThermaCAM Researcher Professional 2.10 Software enabled calculation of enamel emittance against the reference point. Mean-value and Standard Deviation (SD) of emittance and an Intra-class Correlation Coefficient was calculated.
Results: Slice 1:- Mean-value of enamel emittance: first viewing 0.97 (SD 0.013), second viewing 0.975 (SD 0.014), with a combined mean 0.973 (SD 0.013).
Slice 2:- Mean-value of enamel emittance: first viewing 0.962 (SD 0.010), second viewing 0.953 (SD 0.011), with a combined mean 0.957 (SD 0.011).
Overall mean-value of enamel emittance 0.965 (SD 0.014).
Intra-class Correlation Coefficient between the first and second viewing for two slices was 0.631, showing good agreement.
Conclusions: A simple, practical and reliable method of calculating emittance, giving a value of 0.965 for human enamel at 30^oC in an ambient temperature of 22^oC. This can be applied for in-vitro and in-vivo dental thermography.