Objectives:
This study used three lasers (red, green and blue) with a spectrophotometer to compare the light propagation [Absorption (A), Transmittance (T), Attenuation (K) and Scattering Anisotropy Coefficient (g)] in dental tissues and nano filled resin based composite using three incremental build-up techniques: one shade (Body), two shades (Enamel and Dentin), and three shades (Enamel, Transparent and Dentin).
Methods:
Twenty un-erupted recently extracted human 3rd molars (shade: B1) were used to obtain 40 tooth slabs (1.5 mm thickness x 4 mm length). The samples were randomized and equally distributed into four experimental groups: Positive Control (Dental Tissues – enamel, dentino- enamel-junction and dentin), Technique 1 (T1 = 1 shade, B1B), Technique 2 (T2 = 2 shades, A2Dentin/B1Enamel), and Technique 3 (T3 = 3 shades, A2Dentin/Transparent/B1Enamel). One calibrated operator performed all procedures and tests. Cavity preparation was standardized using a #58 carbide bur. Using the spectrophotometer, each specimen was irradiated by the three LASERs. A Voltmeter recorded the light output signal and from this raw data the following optical constants were calculated: absorption (A), transmittance (T), attenuation coefficient (K) and Scattering Anisotropy Coefficient (g). The data were analyzed using One-way ANOVA, followed by the post-hoc Tukey's test. All tests utilized a significance level of 0.05.
Results:
Regarding absorption and transmittance, dental tissues were significantly different compared to the three build-up techniques for all lasers. Regarding the attenuation coefficient, dental tissues were not significantly different for T2 and T3 for the blue and red lasers, however they were significantly different for the green laser. There was no significant difference among the three lasers for T2 and T3.
Conclusion:
Within the limitations of this study, none of the build-up techniques used was able to reproduce the dental tissues optical properties and Technique 2 (2 shades) and Technique 3 (3 shades) resulted in a similar pattern of light propagation.