Difference in light transmittance and depth of cure of flowable composite depending on tooth thickness: an in vitro experimental study

Objectives: This study aimed to quantify light attenuation through varying tooth thicknesses and its impact on the depth of cure of composite resin.Methods: Twenty extracted premolars were used to create enamel-dentin discs that were sanded progressively in 0.5 mm increments from 2.5 mm to 0.5 mm. Light irradiance was measured with and without tooth specimens to evaluate light transmittance. Resin was cured beneath different thicknesses, and the depth of cure was assessed using the Vickers hardness test.Results: The results demonstrated that light transmittance significantly decreased as tooth thickness increased (p < 0.01), leading to reduced resin polymerization. In the 2.0-mm and 2.5-mm tooth thickness groups, the depth of cure was significantly lower than in the control group without tooth specimens (p < 0.05).Conclusions: Ultimately, for tooth structures exceeding 2 mm, self-cure or dual-cure resin polymerization is thought to be more efficient than light polymerization.