Evaluation of the Effect of Coronal Flaring on SWEEPS Laser-Activated Irrigation in Root Canals with Different Curvatures: A Confocal Laser Scanning Microscopy Study

Background and Objectives: The aim of this study was to evaluate the penetration of laser-activated irrigation solutions into dentinal tubules in root canals with different degrees of curvature and different coronal flaring. Materials and Methods: Seventy-six maxillary first molar teeth previously extracted for various reasons were included in the present study. The specimens were divided into two main groups according to distal root canal curvature, determined using the Schneider method: straight (<10°) and curved (20–40°). These groups were further classified into two subgroups according to whether a coronal flaring procedure was performed (n = 19). Following root canal preparation of all specimens, final irrigation was performed using a laser activation method and an irrigation solution prepared with the fluorescent dye Rhodamine B. Horizontal apical, middle, and coronal sections of 1 ± 0.1 mm thickness were obtained from the specimens at 2 mm, 5 mm, and 8 mm from the apical foramen, respectively. The effect of the irrigation solution on dentinal tubule penetration in the root canals was evaluated in the obtained sections using confocal laser scanning microscopy. Following evaluation, the mean and maximum penetration distances into the dentinal tubules were measured. The obtained data were statistically analyzed using Generalized Estimating Equations and Bonferroni correction for multiple comparisons, with the significance level set at p < 0.05. Results: The analysis revealed that only the region factor had a statistically significant effect on mean penetration values (p < 0.001), whereas canal curvature (p = 0.010), coronal flaring (p = 0.002), and region (p < 0.001) had statistically significant effects on maximum penetration values. However, none of the two-way or three-way interactions were significant (p > 0.05). Conclusions: Coronal flaring did not affect mean dentinal tubule penetration but increased maximum penetration depth. Maximum penetration was higher in straight canals than in curved canals, while both mean and maximum penetration were significantly affected by the root canal region.