MICROTENSILE BOND STRENGTH AND NANOLEACKAGE OF DENTIN SURFACES PRETREATED WITH DIFFERENT ETCHING MATERIALS

This in-vitro study aimed to evaluate microtensile bond strength and nanoleackage of dentin surfaces pretreated with different etching materials. Twenty four extracted human intact second molar were selected and debrided to remove remnants of periodontal ligaments. Occlusal surfaces were flattened to expose a flat area of dentin under copious water coolant. One dentin bonding system (Te-Econom Bond) and one dental resin composite restoration (Tetric N-Ceram) were used for the study. The teeth were divided into four groups (6 each) according to the type of etchant material used as follows: group A – citric acid 6%, group B – citric acid 10%, group C – citric acid 20%, and group D- phosphoric acid 37%. The etchants were applied for 15 seconds to the dentin surface. After which teeth were washed, dried, then bonding agent was applied followed by the resin composite restoration. Then a longitudinal sectioning of restored teeth was made to obtain composite-dentin beams of (0.9 x 0.9 mm) in area. Each beam was composed of composite and dentin with adhesive at the interface. The microtensile bond strength (μTBS) was measured and the nanoleakage was observed using SEM. Data was then recorded, tabulated and statistically analyzed. There was no statistical significant difference between the results of the μTBS of groups A, B and D while group C has the lowest microtensile bond strength (19.20± 4.59). For all groups, nanoleackage was more demonstrated at group C and D, while group B show mild nanoleackage and no nanoleackage was observed for group A. It was concluded that low concentrations of citric acid was effective as etchant material compared to phosphoric acid on dentin surface in terms of microtensile bond strength and nanoleakage