ABSTRACT
INTRODUCTION: This study aimed to investigate the effect of the immersion of standardized dentin bars in 5% sodium hypochlorite (NaOCl) solutions at 60°C and 80°C on their viscoelastic properties using dynamic mechanical analysis. METHODS: Eighteen intact teeth were used to produce 99 dentin bars of standard dimensions (12 × 1 × 2 mm) and randomly allocated to 6 groups (n = 15 each) for immersion in (1) saline at 26°C, (2) saline at 60°C, (3) saline at 80°C, (4) NaOCl at 26°C, (5) NaOCl at 60°C, and (6) NaOCl at 80°C. The bars were individually tested using dynamic mechanical analysis at baseline and after every 10 minutes of immersion in the test medium, up to 40 minutes. The effects of media, temperature, duration of exposure, and aspect ratio of bars on the storage modulus and tan delta were investigated using generalized estimating equations. RESULTS: There was a significant interaction between the test medium and the duration of immersion (P < .05). The storage modulus of specimens immersed in NaOCl at 60°C or 80°C decreased significantly (P < .0001) over time of exposure, but the changes in other groups were minimal and insignificant. The tan delta of specimens immersed in saline 80°C (P < .05), NaOCl at 60°C (P < .05), or 80°C (P < .0001) increased significantly over the time of exposure, but the change in NaOCl at 26°C was minimal. Other groups displayed negligible changes. CONCLUSIONS: NaOCl at 60°C or 80°C significantly reduced the elastic behavior but increased the hysteresis of dentin under cyclic loading.
