Technique Sensitivity of Two Universal Adhesives with Different Chemical Formulations: An In Vitro Study

Abstract

The purpose of this study was to evaluate the immediate micro-tensile bond strength of resin composite to dentin when using two universal adhesives in both etch and rinse and self-etch modes after being subjected to different dentin moisture conditions (dry, wet, and moist) and to evaluate the adhesive interface using scanning electron microscope. In this study, 264 specimens were used: 240 for micro-tensile bond strength testing (prepared from 36 teeth) and 24 for scanning electron microscopic evaluation (prepared from 24 teeth). Specimens were prepared from 60 recently extracted free from caries third molars and randomly divided into two groups on the basis of adhesive used (Single Bond Universal or Prime & Bond Universal). Then each group was divided into two sub-groups according to etching mode (etch and rinse or self-etch), Each sub-group was further divided into 3 sub-divisions according to dentin surface moisture state (dry surface, wet surface, or visible moist surface). The teeth were embedded in acrylic blocks 2 mm below the cemento-enamel boundary for the micro-tensile bond test. The occlusal enamel was horizontally sectioned 1 mm below the dentin-enamel junction (DEJ) to expose dentin. The exposed dentin surfaces were then polished for 60 seconds on wet 600-grit SiC paper to produce a standard smear layer. The micro-tensile bond strength to dentin was then determined using a universal testing machine (Instron, MA, USA) at 0.5 mm/minute crosshead speed until failure. The fracture load and bonding area of the specimen were recorded, and the micro-tensile bond strength in MPa had been determined by (Bluehill Lite software, Instron, MA, USA) To evaluate the bonded interface formed by universal adhesives, scanning electron microscopic imaging was used.