Dentine scattering, absorption, transmittance and light reflectivity in human incisors, canines and molars

To evaluate, using Kubelka-Munk reflectance theory, the scattering (S), absorption (K), transmittance (T) and light reflectivity (RI) of incisors, canines and molars human dentine.

Eighty-one human teeth (incisors, canines and molars) were used in this study. All teeth crowns were sectioned using a water-cooled diamond saw at low speed. The obtained dentine samples were polished to a final thickness of 2mm. The relative spectral radiance was measured against black and white backgrounds, using a spectroradiometer in a viewing cabinet with D65 illuminant. Kubelka-Munk equations were used to calculate the scattering and absorption coefficients, transmittance and light reflectivity. Kruskal-Wallis rank sum test was performed to compare the mean values of Kubelka-Munk coefficients of human incisors, canines and molars dentine samples followed by Kruskal-Wallis multiple comparison tests for pairwise comparisons.

The spectral behavior of S, T and RI exhibited similar trends for all three types of dentine samples. However, highly significant differences (p<0.001) were found between their magnitudes in the three types of dentine samples (p<0.001). Only the magnitudes of the K coefficients were found to be similar (p=0.235) between incisors, canines and molars. Canine's dentine samples showed highest S and RI values, while human molars dentine samples exhibited highest K and T values.

Within the limitations of this study, the optical properties of human dentine are strongly influenced by the type of tooth. The results of the present study can be used as reference in the development of aesthetic dental restorative materials.

The significant differences identified in the optical behavior of the dentine from the three types of teeth have to be taken into consideration by the dentist and the dental technician when pursuing biomimetics with any restorative material in esthetic dentistry.