EFFECTS OF SODIUM HYPOCHLORIDE ON CYCLIC FATIGUE RESISTANCE OF BIORACE ROTARY INSTRUMENT WITH DIFFERENT TIP SIZES

Abstract

Aim:The aim of the present study was to determine the effect of sodium hypochloride solution on the cyclic fatigue resistance of BioRace (BR) NiTi instrument with different tip size.Methods:Eighty BioRace instrument with two different size (BR4-35.04 and BR5-40.04) were used. These instruments were randomly divided into four group, each containing 20 files. The cyclicfatigue resistance were than tested in the following conditions; group 1, BR 4 with no immersion; group 2, BR 4 with dynamic immersion in 5.25% NaOCl at 37°C ± 1°C for 5 minute; group 3, BR 5 with no immersion; group 4, BR 5 with dynamic immersion in 5.25% NaOCl at 37°C ± 1°C for 5 minute. Then the instruments were used in stainless steel artificial root canal with a curvature of 60° and 5 mm radius. Number of cycle to failure (NCF) were measured for each group. The time to failure (TTF) in seconds werealso recorded. Data were subjected to the statistical analysis.Results: Nonimmersion groups were statistically superior to immersion groups (group1>group 2 and group 3>group4) both regarding TTF and NCF. However, no significant difference was found between instruments with different tip size regardless of the immersion procedure.Conclusion:The cyclic fatigue resistance of BR instrument was affected by NaOCl immersion but not with tip size.