VARIABILITY IN MICROLEAKAGE OBSERVED IN A TOTAL-ETCH WET BONDING TECHNIQUE UNDER DIFFERENT HANDLING CONDITIONS

Using a stereoscopic clearing protocol and scanning electron microscop y, we investigated the extent and nature of microleakage in a total-et ch, current-generation dentin adhesive by a wet-bonding technique unde r different handling conditions. The hypotheses were that inadequate l ight curing of the primer or incomplete drying of the primer solvent m ight adversely affect the sealing ability of an acetone-containing adh esive system. The study consisted of three experimental groups: (I) a control group with an adequate light source and with the primer solven t completely dried; (II) an ''inadequate-light'' group; and (III) an ' 'incomplete evaporation of primer solvent'' group. The extent of micro leakage after silver staining and clearing of the specimens was scored based on a modified five-point scale. Nonparametric statistical analy sis (Kruskal-Wallis ANOVA) followed by a multiple comparison test (Dun n test) indicated significant differences among the three groups (p < 0.05). SEM examination of the restorative interface revealed that micr oleakage appeared to be initiated from the bonding resin-hybrid layer interface in all three groups, representing the weak link in the adhes ive system. In addition, microleakage was characterized by 5 zones, ea ch delineating a stage in a continuous array of progressively deleteri ous microleakage patterns variously distributed among the three groups . It was suggested that, while the bonding resin-hybrid layer interfac e represented the intrinsic weakness in an already much improved denti n adhesive, extrinsic factors such as the adequacy of the curing light and, more importantly, complete removal of the primer solvents can an d should be avoided to preserve the structural integrity of the margin al seal.