Journal of Dental Medicine

Background and Aims: Fracture and color change are among the most common causes of clinical failure of resin composite restorations. Therefore, this study aimed to examine the fracture toughness and color changes of 3 Nano-hybrid resin composites in dry and wet conditions.
Materials and Methods: Three resin composites were studied. A total of 36 rectangular specimens were prepared for each material, randomly divided into 2 groups, and stored at 37°C dry or soaked in distilled water. In each group, the specimens were subdivided into three groups (n=6) and stored for 1, 7, and 60 days. After each time interval, the specimens were tested for the fracture toughness and loaded at a cross-head speed of 0.5mm/min using a universal testing machine. The baseline and final color measurement was recorded for each specimen using a spectrophotometer. The collected data was analyzed using ANOVA and Kruskal-Wallis tests.
Results: After 60 days, the mean value of fracture toughness was lower in the wet condition compared to that of dry condition. However, it was not significantly different except for aura Bulkfil (P=0.001). Color change was significantly different for Tetric Evoceram and aura with a greater value in the wet condition compared to that of dry (P=0.004). The greatest color stability was found for aura and the least for Tetric Evoceram.
Conclusion: In this study, most of the materials stored in a dry condition showed a greater fracture toughness and color change.

Background and Aims: The white color of teeth is one of the most essential factors in smile esthetics. Therefore, various whitening agents such as bleaching mouthwashes have been produced in response to the people’s high demand for having whiter teeth. The present study evaluated the efficacy of three whitening mouthwash products on tooth enamel whiteness.
Materials and Methods: In the present in vitro study, 32 bovine incisors were assigned to four groups in terms of the mouthwash used (n=8): control (C); Xenon Smart White (ZSW), containing pyrophosphate and triphosphate; Signal White Now (SWN), containing Blue Covarine; and Pasta Del Capitano whitening mouthrinse (PCW), containing Plasdone. Colorimetry was carried out using a spectrophotometer at the baseline and 2, 4, 8, and 12 weeks after treatment with mouthwashes. Data were analyzed using CIELab parameters with ANOVA, RM two-way ANOVA, and post hoc Tukey tests (α=0.05).
Results: The results showed that the whiteness created by the SWN mouthwash was clinically visible (ΔE>3.3). However, the functions of all the mouthwashes were statistically similar with no significant differences from the control group (P>0.05).
Conclusion: Although, Blue Covarine-containing mouthwash was somewhat effective in whitening of tooth enamel, none of the mouthwashes had significant efficacy compared to distilled water.