Reaction rate of NaOCl in contact with bovine dentine: effect of activation, exposure time, concentration and pH

Aim To determine the influence of activation method (ultrasound or laser), concentration, pH and exposure time on the reaction rate (RR) of NaOCl when in contact with dentinal walls. Methodology The walls from standardized root canals in bovine incisors were exposed to a standardized volume of sodium hypochlorite (NaOCl) with different concentrations (2% and 10%), pH (5 and 12) and exposure times (1 and 4 min). Two irrigation protocols were tested: passive ultrasonic irrigation or laser activated irrigation with no activation as the control. The activation interval lasted 1 min followed by a rest interval of 3 min with no activation. The RR was determined by measuring the iodine concentration using an iodine/thiosulfate titration method. Results Exposure time, concentration and activation method influenced the reaction rate of NaOCl whereas pH did not. Conclusions Activation is a strong modulator of the reaction rate of NaOCl. During the rest interval of 3 min, the consumption of available chlorine increased significantly. This effect seems to be more pronounced after irrigant activation by laser. pH did not affect the reaction rate of 2% NaOCl.