Effect of light sources on the bond strength of resin material to thin-walled roots.

The aim of this study was to evaluate the bond strength to the dentin of an adhesive material used for root reinforcement light activated with different sources. Roots were divided into 4 groups (n=15) according to the light source used to activate the resin reinforcement: GI, non-weakened roots (control); GII, halogen light (H) 600 mW/cm²; GIII, LED 800 mW/cm² and GIV, LED 1500 mW/cm². The reinforcement was done with adhesive, composite resin and fiberglass posts. After 24 h, the specimens were sectioned and the first slice of each post region was used in the push out test in a universal testing machine with a crosshead speed of 0.5 mm/min. Failure modes of the debonded specimens were examined. Data (MPa) were analyzed by ANOVA and Holm-Sidak test (α=0.05). The second slice from each region was analyzed by scanning electron microscopy (SEM). LED-1500 (4.69 ± 1.74) provided bond strength similar to the control group (5.05 ± 2.63) and statistically different from H-600 (1.96 ± 0.94) and LED-800 (2.75 ± 1.90), which were similar to each other (p<0.05). Cervical (4.16 ± 2.32) and middle (4.43 ± 2.32) regions showed higher bond strength than the apical (2.25 ± 1.50) (p<0.05). There was a prevalence of adhesive failures in H-600 and LED-800 and cohesive failures in LED-1500. SEM showed the formation of long, numerous and fine tags. It was concluded that LED-1500 provided higher bond strength of resin reinforcement to the dentin.

Ex vivo comparison of the accuracy of Root ZX II in detecting apical constriction using different meter's reading.

The purpose of this study was to compare the accuracy of Root ZX II to locate the apical constriction with the display meter set at "0.5" and "1'"reading. Seventy single-rooted teeth were soaked in an alginate model and randomly distributed in 2 groups (n = 35). Measurements were taken following canal irrigation with 1% NaOCl. The length was established using a #20 K-file attached to the holder when the display indicator reached the marks "0.5" (group I) or "1" (group II), after the meter read "Apex." Then, the file was fixed in position and the teeth removed from the alginate. The apical portion of the root was shaved until the tip of the file could be seen, the distance to the apical constriction verified by means of a stereomicroscope and the measurements compared. Statistical analysis was performed by using Student t test with the null hypothesis set as 5%. The mean positions of the file tip relative to the apical constriction were -0.23 +/- 0.39 mm and -0.42 +/- 0.45 for groups I and II, respectively, with no statistical difference (P > .05). The accuracy was 90.5% and 83.78% for the Root ZX II "0.5" and "1" readings, respectively. It was concluded that the meter reading "1" of Root ZX II reduced the risk of working length overestimation.

In vivo comparison of the biocompatibility of two root canal sealers implanted into the subcutaneous connective tissue of rats.

OBJECTIVE: To evaluate the subcutaneous biocompatibility of 2 root canal sealers. STUDY DESIGN: The subcutaneous implant technique recommended by the Fédération Dentaire International (FDI) was used to test Endométhasone and EndoREZ root canal sealers. These materials were placed in Teflon tubes, 1 mm in diameter and 10 mm in length, and implanted into 2 pockets created in the back of 40 Calomys callosus rodents, 20 for each material. Tissue biopsies were collected and histologically examined 15, 30, 60, and 90 days after the implantation procedure. The overall level of the inflammatory tissue response was graded as none, slight, moderate, or severe on the sealer-connective tissue interface at the opening ends of the tubes. The connective tissue response along the lateral wall outside of each tube served as a negative control. RESULTS: The tissue reaction to the Endométhasone diminished with time. The EndoREZ sealer was highly toxic during all experimental periods. CONCLUSION: Endométhasone root canal sealer presented biocompatibility within the analyzed periods, whereas EndoREZ showed no biocompatible behavior and caused late hypersensitive reaction.