Bond strength of different adhesive systems to dental hard tissues

Objectives: The aim of this study was to compare the shear bond strengths of different adhesive systems to enamel and to dentin of different depths. The adhesive systems used were: Single Bond one-bottle total-etch; AQ Bond one-step self-etching, Clearfil SE Bond, two-step self-etching; Tyrian SPE/One-step Plus two-step self-etching. Methods:Eighty extracted non-carious human mandibular molars were mounted in self-curing resin and the occlusal surfaces were ground with a mechanical grinder to obtain flat occlusal enamel surfaces. After applying the adhesive systems, a plastic tube was attached to the enamel surfaces. The tube was filled with a universal hybrid composite resin which was then polymerized. The specimens were stored in water at 370C for 24 hours. Shear bond testing was carried out using an Instron Universal testing machine with a crosshead speed of 1mm/min. The occlusal enamel of the 80 teeth was removed to determine the bond strengths of the adhesives to superficial dentin. To obtain deep dentin, the same teeth were ground deep towards the pulp, with the remaining dentin thickness approximately 0.7mm. The adhesives and restorative material were then applied to the prepared dentin surfaces following the methodology described above. Results: For occlusal enamel surfaces, the bond strength of Single Bond was significantly higher than the other adhesives. Single Bond, Clearfil SE Bond and Tyrian SPE/One-step Plus performed equally when bonded to superficial dentin; the lowest bond strength was obtained with AQ Bond. On deep dentin, the highest bond strengths were attained with Clearfil SE Bond. Conclusion: For each adhesive system, shear bond strength to enamel was statistically higher than it was to either superficial or deep dentin. There were no significant differences between shear bond strengths to superficial versus deep dentin, regardless of adhesive.