Recent formulations of resin-based composites have incorporated different combinations of materials. However, the mechanical and bonding behavior of these materials with intraradicular posts are unclear. This study aimed to evaluate the effect of light-cure and dual-cure resin composite posts on the fracture resistance of endodontically-treated teeth. Materials and Methods: Ninety extracted human upper canines were selected and randomly divided into nine groups (n=10): (G1) endodontically treated teeth without endodontic posts; (G2) glass-fiber post cemented with glass-ionomer cement; (G3) endodontic post by dual-cure composite resin (Rebilda DC); (G4) endodontic post by dual-cure composite resin (Cosmecore); (G5) endodontic post by dual-cure composite resin (Bis-Core); (G6) endodontic post by light-cure composite resin; (G7) glass-fiber post customized with flowable composite resin; (G8) glass-fiber post cemented with light-cure composite resin; (G9) glass-fiber post cemented with self-adhesive resin cement. After the post insertion, all specimens were subjected to mechanical (250,000 cycles) and thermocycling (6000 cycles, 5 °C/55 °C) and immediate loading at 45 degrees in a universal testing machine until fracture. The data were analyzed by one-way ANOVA and multiple comparisons using the Fisher LSD Method (p < 0 05). Results: The mean failure loads (±SD) for the groups ranged from 100.7 ± 22.6 N to 221.9 ± 48.9 N. The G1 group (without endodontic posts) had a higher fracture strength than all experimental groups (p < 0.001). Conclusions: Within the limitations, the light- and dual-cure post technique did not present lower fracture resistance values as compared to the conventional glass-fiber post.

Resin-based composites (RBCs) have transformed restorative dentistry and its procedures. However, the characteristics of RBCs have been modified over the years to enhance the physical and chemical properties of the materials. This context raises the need for studies that evaluate whether the properties of the RBCs that are commercially available are clinically adequate with different curing modes. This study aimed to evaluate the mechanical behavior of commercial RBCs after undergoing different curing modes. Twenty-three RBCs of different classes were evaluated. For curing the specimens, a microwave (BMS45, Brastemp) (for 3 min at 450 W) and three LED units were used: an Emitter A Fit (Schuster (second generation)) (light-curing for 15 s with an irradiance of 1250 mW/cm2), VALO (Ultradent (third generation)) (light-curing for 15 s with an irradiance of 1100 mW/cm2), and Emitter Now Duo (Schuster (second generation)) (light-curing for 15 s with an irradiance of 1100 mW/cm2). A total of 670 RBC specimens of 8 mm in diameter and 1 mm in depth were obtained. Afterward, a biaxial flexure strength test was performed until the failure of the specimens, using a universal testing machine set at a speed of 0.5 mm/min. The same specimens were subjected to infrared spectroscopy for evaluating the degree of conversion. Tukey’s test was used for multiple comparisons at a significance level of 5%. The light-curing mode did not affect the flexure strength of the RBCs (p > 0.05), but the type and shade of RBCs did so (p < 0.05). In conclusion, the type of RBC directly interferes with the mechanical behavior of the material. However, the curing modes within the same RBC did not change the mechanical properties.

This study evaluated the effect of laser irradiation protocols using Thera Lase Surgery (TL), at 2.5 W (2.5) or 2.7 W (2.7), and Gemini (GE), at 1.2 W (1.2) or 1.5 W (1.5) of potency, on the root-end resection surface, in relation to external root temperature, roughness, and surface morphologic changes after the treatments, in the areas near to the root canal (RC) or external root surface (ER). Fifty teeth were endodontically treated and the root-end were resected 3 mm away from the root apex. The specimens were randomized into 5 groups (n = 10), according to the laser irradiation protocol: Control (CO-DW) without irradiation; (TL-2.5) Thera Lase Surgery, 2.5 W; (TL-2.7) Thera Lase Surgery, 2.7 W; (GE-1.2) Gemini, 1.2 W; and (GE-1.5) Gemini, 1.5 W. The external root temperature change was obtained through the difference between the highest value observed during the irradiation and the value at the beginning of the treatment. The surface roughness (µm) was analyzed by confocal laser microscopy and the apical surface morphology was evaluated by scanning electron microscopy, in RC or ER. The temperature change was similar between the irradiation protocols (p > 0.05). CO-DW and GE-1.5 provided the lowest surface roughness (p < 0.05), regardless of the analyzed area. TL-2.7 and GE-1.7 showed more uniform on apical resected morphology and a higher incidence of dentinal tubules occlusion, but only near the root canal (p < 0.05). Root-end resected surface submitted to TL-2.7 and GE1.7 irradiation protocols are more homogeneous and shown higher incidence of closed dentinal tubules near to root canal, despite providing a surface roughness.