Double-layer build-up technique: laser evaluation of light propagation in dental substrates and dental composites

Purpose: To evaluate and compare light propagation in dental tissues and dental composite restorations using a double-layer build-up technique. Materials and methods: Natural teeth slabs and dental restoration buildups with A2D and B1E-colored nanofilled, supra-nanofilled, and microhybrid composites were randomized and equally distributed into four experimental groups (n = 10). Using a spectrophotometer, the samples were irradiated by three wavelengths of lasers: red, green, and blue. A voltmeter recorded the light output signal, and the following optical constants were calculated: absorption (A), transmittance (T), and attenuation (K). The data were analyzed using one-way analysis of variance (ANOVA), followed by post hoc Tukey's test (α = 0.05). Results: Absorption results varied according to the laser color and different composites tested. Regardless of the laser wavelength, the supra-nanofilled composite showed greater light transmittance and lower light attenuation compared with the dental tissues, which was the opposite of the nanofilled composite. The microhybrid composite showed no difference in light transmittance or light attenuation compared with the dental tissues. Conclusion: Within the limitations of this observational in vitro study, the microhybrid dental composite group had the most similar light propagation pattern compared with natural teeth when using the double-layer build-up technique.