Effect of different enamel treatments on bond strength using resin dental adhesives

Objective: The aim of this investigation was to evaluate the effect different cleaning techniques used on enamel surfaces have on the bond strength of a composite resin to the dental enamel. Method and Materials: Eighty-eight bovine enamel fragments were mounted in acrylic resin bases. The enamel surfaces were sanded using 200-, 400-, and 600-grit sandpapers, thus creating a smear layer. These surfaces were then randomly divided in 2 groups: 1 of them received salivary contact for 10 minutes, and the other received it for 60 minutes. Then all surfaces were cleaned with a pumice and water paste applied with a rubber cup, followed by the application of biological detergent, sodium bicarbonate jet, or air/water spray. After cleansing, the enamel surfaces received the application of the Scotchbond Multi-Purpose adhesive system and Z100 composite resin, following the manufacturer's instructions, using an appropriate matrix. After storage at 37°C for 8 days, traction tests were carried out using an Instron machine operating at 0.5 mm/minute. Some fractured specimens (randomly chosen) were analyzed under scanning electron microscopy. Results: The statistical analysis using descriptive and inferential methods did not show significant differences between the different periods of time of salivary contact. The technique of pumice and water paste cleaning followed by the application of biological detergent was significantly more efficient than the others. Scanning electron micrographs of the fragments after traction tests confirmed these results. Conclusion: The technique of pumice and water paste cleaning followed by the application of biological detergent was the treatment that allowed the best results in terms of resin bonding to bovine enamel covered with acquired pellicle, and the sodium bicarbonate jet technique presented the lowest bond strength values and seemed to disturb the acid conditioning of enamel surfaces. Palabras clave: dental bonding, dental cavity preparation, dental enamel bonding