Comparison of Light Propagation in Dental Tissues and Resin Composites

Objectives: The purpose of this study was to compare the light propagation (absorption, transmittance and attenuation) in dental tissues and nanofilled resin based composite (RBC) using three LASERs (red, green and blue) with a spectrophotometer along with three incremental RBC build-up techniques: Technique 1 (T1)= one shade (B1 Body), Technique 2 (T2)= two shades (A2Dentin/B1Enamel), Technique 3 (T3)= three shades (A2Dentin/Transparent/B1Enamel).
Methods: Forty tooth slabs (1.5mm thickness x 4 mm length) from un-erupted recently extracted human third molars (shade: B1) were obtained, and they were then randomized and equally distributed into four experiment groups (n=10 per group): Control Group (Dental tissues – enamel, dentino-enamel-junction and dentin), Technique 1, Technique 2, and Technique 3. One calibrated operator performed all procedures and tests. Cavity preparation was standardized using a #58 carbide bur. Using the spectrophotometer, each specimen was irradiated at 0° degree from occlusal to cervical by the three LASERs wavelengths. A Voltmeter recorded the light output signal and from this raw data the following optical constants were calculated: absorption (A), transmittance (T) and attenuation coefficient (K). The data were analyzed using the one-way ANOVA, followed by the post-hoc Tukey’s test (alpha=0.05)
Results: There was a significant difference in absorption and transmittance between dental tissues and the three build-up techniques for all LASERs. Regarding attenuation, dental tissues were not significantly different from T2 and T3 for the blue and red LASERs, but except for the green LASER. Moreover, for absorption, transmittance, and attenuation with all LASERs, T1 was significantly different from T2 and T3, while no significant difference was found between T2 and T3.
Conclusions: Within the limitations of this study, none of the build-up techniques used were able to reproduce the dental tissues optical properties and T2 (two shades) and T3 (three shades) resulted in a similar patter of light propagation.