Effect of autoclave sterilisation and heat activated sodium hypochlorite irrigation on the performance of nickel-titanium rotary files against cyclic fatigue

The present study aims to assess the impact of heat-activated sodium hypochlorite (NaOCl) and/or autoclave sterilisation on the cyclic fatigue resistance (CFR) of heat-treated nickel-titanium rotary files used in root canal treatment. The CFR of One Curve (OC) files was evaluated under the following conditions: as received (Group 1; control), immersion in NaOCl at 23 ± 1ºC (Group 2), immersion in NaOCl at 60 ± 1ºC (Group 3), autoclave sterilisation at 135 1ºC (Group 4), combined treatment of autoclave sterilisation and immersion in NaOCl at 23 ± 1ºC (Group 5), and combined treatment of autoclave sterilisation and immersion in NaOCl at 60 ± 1ºC (Group 6). A simulated root canal in a zirconia block was utilised to test the performance of the files. All the types of treatments resulted in significant reductions in fracture resistance of the OC files. Immersion of the files in NaOCl at 23ºC revealed the smallest reduction, while combined treatment of autoclaving and immersion in NaOCl at 60ºC caused the greatest reduction. Autoclave sterilisation or exposure of OC files to 2.5% NaOCl adversely affect the cyclic fatigue life and increasing solution temperature or combined treatment caused additionally significant reduction in CFR

The effect of micro-electric current and other activation techniques on dissolution abilities of sodium hypochlorite in bovine tissues

BACKGROUND: The aim of the study was to evaluate the effects of micro-electric current on sodium hypochlorite’s (NaOCl’s) tissue-dissolution abilities, compared with other activation methods, including sonic, ultrasonic, pipetting, and temperature. METHODS: Bovine muscle tissues (n = 154) with standard sizes and weights were prepared and divided into two temperature groups: room temperature and 45 °C. Each temperature group was divided into seven sub-groups by activation methods: D = distilled water (−control); NaOCl = 5.25 % passive NaOCl (+ control); P = 5.25 % NaOCl with pipetting; SA = 5.25 % NaOCl with sonic activation; UA = 5.25 % NaOCl with ultrasonic activation; E-NaOCl = 5.25 % NaOCl with micro-electric current; and E-NaOCl + P = 5.25 % NaOCl with micro-electric current and pipetting. Specimens were weighed before and after treatment. Average, standard deviation, minimum, maximum, and median were calculated for each group. Resulting data were analyzed statistically using multi-way ANOVA and Tukey HSD tests. The level of the alpha-type error was set at < 0.05. RESULTS: At room temperature, the E-NaOCl + P group dissolved the highest amount of tissue (p < 0.05), and the UA, SA, and P groups dissolved significantly higher amounts of tissue than did the positive control or E-NaOCl groups (p < 0.05). At 45 °C, there was no significant difference between the SA and E-NaOCl groups (p > 0.05), and the E-NaOCl + P group dissolved a higher amount of tissue than any other group (p < 0.05). CONCLUSIONS: Using NaOCl with micro-electric current can improve the tissue-dissolving ability of the solution. In addition, this method can be combined with additional techniques, such as heating and/or pipetting, to achieve a synergistic effect of NaOCl on tissue dissolution