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Influence of enamel wetness on composite restorations using various dentine bonding agents: part II-effects on shear
Shu-Fen Chuang1, Li-Tung Chang, Chih-Han Chang
1Institute of Oral Medicine, National Cheng Kung University, Tainan, Taiwan, ROC. sfchuang@mail.ncku.edu.tw
Objectives:
To investigate the bond strength and fracture characteristics of various dentine bonding agents (DBAs) on wet or dry enamel.
Methods:
Forty molar halves with enamel flattened were divided into 5 groups. Groups 1-4, teeth were acid-etched and treated separately with either an ethanol-based adhesive (Single Bond) or an acetone-based adhesive (Prime & Bond NT) on dry or wet enamel. Group 5 was treated with a self-etching adhesive (Clearfil SE Bond). The treated enamel surfaces were bonded with Z 250 composite with metal rings. The composite-ring assemblies were subjected to shear bond test until failure. Failure patterns on the debonded surfaces were inspected under a scanning electron microscope. The bonded enamel thickness was measured on sectioned specimens to investigate their statistical evidence. Results of open margin and enamel microcrack ratios from Part I of this study were compared with these fracture characteristics. Data was analyzed statistically.
Results:
There was no difference in the bond strength between paired groups using the same DBA on wet or dry enamel. The teeth restored with self-etching adhesive exhibited lower bond strength and higher adhesive-enamel failure rate than the other groups. No correlation between enamel thickness, microcrack, bond strength, and failure patterns was revealed.
Conclusion:
The self-etching adhesive had a lower enamel bond strength than the other bonding systems. The difference in the failure patterns of groups with ethanol- and acetone-based DBAs on wet or dry enamel was indistinct. The frequently observed enamel microcrack cannot be directly correlated with the bond strength of bonding systems.
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