Evaluation of Calcium Hydroxide Removal Efficiency of Different Concentrations and Forms of Sodium Hypochlorite

INTRODUCTION: Calcium hydroxide could not be fully removed from the root canal regardless of the method or irrigation used. Calcium hydroxide residues remaining in the dentin tubules prevent the penetration of the sealer into the dentin, thereby reducing the bond strength and increasing microleakage. The aim of the present study was to compare different forms of sodium hypochlorite for the removal of calcium hydroxide from root canals.
METHODS: Sixty single-rooted mandibular premolars with single canals were prepared using ProTaper Next file up to size X3. Each root canal was filled with calcium hydroxide using #30 Lentulo (Dentsply, Mailifer, Switzerland) to the working length. Then, cotton pellets were placed over canal orifices and teeth were stored in 100% humidity at a temperature of 37 ̊C for 7 days. Afterwards, the teeth were divided into 4 groups according to the irrigation protocol to be used for the removal of calcium hydroxide (n=10): Group 1,2.5% NaOCI; Group 2,5.25% NaOCI; Group 3,NaOCI gel; Group 4,control. Samples were split longitudinally, photos of halves were taken at 10× magnification and were analyzed using the Corel DRAW Graphics Suite X4 v14.0 (Corel Corporation. CA, USA) software to calculate the percentage of surfaces with residual calcium hydroxide. Chi-square test was used for making comparisons among the groups at a significance level of p<0.05.
RESULTS: There were significant differences between the 2.5% NaOCI solution, 5.25% NaOCI solution, NaOCI gel groups and the control group (p<0.001).
DISCUSSION AND CONCLUSION: Gel form of NaOCI is an appropriate and effective method for removing Ca(OH)2 from the root canals.