Influence of enamel wetness on composite restorations using various dentine bonding agents: part II-effects on shear bond strength.
OBJECTIVE
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.


CONCLUSIONS
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.
Chuang
Shu-Fen
SF
Institute of Oral Medicine, National Cheng Kung University, Tainan, Taiwan, ROC. sfchuang@mail.ncku.edu.tw
Chang
Li-Tung
LT
Chang
Chih-Han
CH
Yaman
Peter
P
Liu
Jia-Kuang
JK
D000180:Acrylic Resins / Q000737:chemistry*; D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D003743:Dental Enamel / Q000737:chemistry*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D011140:Polyurethanes / Q000737:chemistry*; D033081:Shear Strength
D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D011140:Polyurethanes