EFFECT OF SODIUM HYPOCHLORITE IMMERSION AND AUTOCLAVE STERILIZATION ON FRACTURE RESISTANCE OF PROTAPER GOLD NITI ROTARY INSTRUMENTS

Background: Instrument fracture is a common problem faced during root canal preparation. The present study aimed to analyse the effect of sodium hypochlorite (NaOCl) immersion and autoclave sterilization on fracture resistance of ProTaper Gold NiTi rotary instruments in artificial canals. Methods: An observational study was performed using forty new ProTaper Gold rotary NiTi instru­ments. The files were divided into four groups (N=10) with Control (no immersion/ sterilization), one cycle each of NaOCl immersion and sterilization, five cycles each of NaOCl immersion and sterilization, and ten cycles each of NaOCl immersion and sterilization. The instruments were im­mersed in NaOCl for five minutes in all test groups, and were subjected to cyclic fatigue testing in artificial canals with 25 mm length, 60° curvature, and radius of curvature 4 mm. The number of cycles to fracture (NCF) was calculated for each instrument. The obtained data were subjected to statistical analysis (p-value < 0.05). The Kolmogorov Smirnov test was performed to examine the normality distribution of the NCF values. One-way ANOVA test was used to compare the mean NCF values for the different groups. Results: Sodium hypochlorite immersion and autoclave sterilization exhibited no significant dif­ference in NCF values between the control and test groups (p-value > 0.05). All the experimental groups demonstrated comparable NCF values and significant difference was not found between the groups (p-value > 0.05). Conclusions: Repeated cycles of sodium hypochlorite immersion and autoclave sterilization do not seem to influence ProTaper Gold instruments’ fracture resistance.