How to improve root canal filling in teeth subjected to radiation therapy for cancer.

The aim of this study was to evaluate the influence of radiation therapy on root canal sealer push-out bond strength (BS) to dentin and the sealer/dentin interface after different final irrigation solutions (NaOCl, EDTA, and chitosan). Sixty-four maxillary canines were distributed into two groups (n=30): non-irradiated and irradiated with 60 Gy. Canals were prepared with Reciproc-R50 and subdivided (n=10) for final irrigation (NaOCl, EDTA, chitosan) and filled. Three dentin slices were obtained from each root third. The first slice of each third was selected for BS evaluation, and the failure mode was determined by stereomicroscopy. SEM analysis of the sealer-dentin interface was performed in the remaining slices. Two-way ANOVA and Tukey's tests (α=0.05) were used. Lower BS (P<0.0001) was obtained after irradiation (2.07±0.79 MPa), regardless of the final irrigation solution used. The NaOCl group (P<0.001) had the lowest BS in the irradiated (1.68±0.72) and non-irradiated (2.39±0.89) groups, whereas the EDTA (irradiated: 2.14±0.77 and non-irradiated: 3.92±1.54) and chitosan (irradiated: 2.37±0.73 and non-irradiated: 3.51±1.47) groups demonstrated a higher BS (P<0.05). The highest values were observed in the coronal third (3.17±1.38) when compared to the middle (2.74±1.36) and apical ones (2.09±0.97)(P<0.0001). There were more cohesive failures and more gaps in irradiated specimens, regardless of the final solution. The present study showed that radiation was associated with a decrease in BS, regardless of the final solution used, whereas chitosan increased BS in teeth subjected to radiation therapy.

Influence of aging on bond strength of artificial teeth to denture base acrylic resins

Aim: The aim of this study was to evaluate the bond strength of artificial teeth to different types of denture base resins when submitted to thermomechanical cycling (TMC). Methods: Sixty artificial mandibular first molars (Trilux, Vipi) were randomly divided into 3 groups according to denture base acrylic resins (Vipi Wave, Vipi Cril, and Vipi Cril Plus, Vipi). The teeth were fixed onto self-polymerizing acrylic resin bars (0.5 cm2 cross-section x 2 cm height), and the set was included in a metal flask using dental stone/silicone. After the dental stone was set, the bar was removed, and the denture base resin was packed and processed according to the group studied (Vipi Wave: 180 W/20 minutes + 540W/5 minutes; Vipi Cril and Vipi Cril Plus: Water bath at 74ºC for 9h). After polymerization, the samples were divided into 2 groups (n=10), according to the TMC treatment received (simulation of 5 years of mastication or not). The samples were submitted to tensile bond strength test (1 mm/min), and the data (MPa) were statistically analyzed (2-way ANOVA, Bonferroni, α=0.05). The fracture interfaces were evaluated using a stereomicroscope (50x). Results: The bond strength results showed no statistically significant difference (p>0.05) between the resins studied. TMC was significant (p<0.05), demonstrating lower values for the bond strength of artificial teeth to Vipi Cril Plus. The predominant fracture type was cohesive in resin. Conclusions: It was concluded that there is no difference in bond strength between artificial teeth and the resins used for denture base. However, TMC decreases the bond strength values of artificial teeth and crosslink thermo-polymerizable acrylic resin