Effect of application technique and mode of curing on nano-leakage of universal adhesive system

Abstract

This study was carried out to Investigate the effect of application technique (total etch &self etch) and curing mode (regular & soft start) on nanoleakage of universal adhesive system in coronal and root dentine. A total number of 80 freshly extracted lower molars were used. The teeth were divided into two groups (40 teeth each) according to the application technique of the adhesive (either total or self-etch mode). Each group was subdivided into two subgroups (20 teeth each) according to the mode of curing that was used either regular or soft start mode. Each subgroup was further divided into two divisions (10 teeth each) according to the surface to which the adhesive will be applied either coronal or root dentin. The roots of all teeth were cut off at the cemento-enamel junction. The occlusal enamel of the coronal portion was removed to the depth of the central fossa to expose dentine. For the root portion, the cervical 1/3 of the buccal surface was flattened by wet grinding on a bench grinder machine. The adhesive was applied according to manufacturer instructions. Resin composite was incrementally packed and light cured either in the regular continuous mode for 20 s or cured in the ramp soft-start mode. The specimens were sectioned into beams of 1 mm thick. The beams were immersed in ammonical silver nitrate for 24 h, rinsed with distilled water, and immersed in a photo-developing solution for 8 h. Nanoleakage patterns were detected using an environmental scanning electron microscope (ESEM), and the amount of silver nitrate penetration (Wt%) was analyzed using the EDAX. The results revealed that, regardless the mode of curing in coronal or root dentine, self-etch application technique showed statistically significantly higher nanoleakage mean values compared to total-etch in all the groups. In all the groups regular curing mode showed statistically significantly higher nanoleakage mean values than soft start mode, except in coronal dentine with the self-etch application technique there was no statistically significant difference between nanoleakage mean values of the two curing modes. Regardless the curing mode with self-etch application technique, there was no statistically significant difference between nanoleakage mean value of coronal and root dentin, while for total etch technique with regular curing mode, root dentin showed statistically significantly higher nanoleakage % mean value than coronal dentin. It could be concluded that, Nanoleakage varied with technique of application of the universal adhesive system being greater with the self-etch technique. Total etch technique using soft start curing mode in coronal and root dentine presented the lowest nanoleakage between the groups.