Effect of PVM/MA Copolymer on Bond Durability of Adhesive Resins

Objective: This study investigated the effects of PVM/MA copolymer and aging with thermocycling on the shear-bond strengths of an etch-and-rinse adhesive (Adper Single Bond Plus-ASB) and two different self-etch adhesive systems (Clearfil SE Bond-CSE and Fluorobond II-FLB) to dentin.

Methods: The occlusal surfaces of sixty extracted molar teeth were abraded just below the cusps to expose flat occlusal areas of dentin. Each tooth was then sectioned into four pieces from the occlusal surfaces along the long axes of the tooth. For each test group, 20 dentin sections were chosen randomly. Adhesive systems were applied to the occlusal surfaces. The test groups (G) were: (G1) Pure CSE Bond; (G1C) Copolymer (50 mg/ml PVM/MA) containing CSE; (G2) FLB without copolymer; (G2C) FLB with copolymer; (G3) ASB without copolymer; (G3C) ASB with copolymer. Following bonding applications, resin composite (Clearfil Majesty Posterior) was applied to dentin surfaces (2.1 mm in diameter and 3 mm in height) and light cured. Half of the specimens from each group were tested immediately after preparation (IM) and the other half was tested after exposure to 10,000 thermal cycles (TC; 5-60 °C). Bond strengths were measured at a crosshead speed of 0.5 mm/minute. Data were analyzed with ANOVA and Tukey's HSD.

Results:

	Bond Strength (Mpa)±SD
Groups	IM	TC
G1-CSE	19.2±2.3e	15.1±5.2d
G1C-CSE	22.0±1.7f	11.6±3.1c
G2-FLB	10.9±2.2c	5.6±2.7a
G2C-FLB	10.3±1.0c	6.2±1.8ab
G3-ASB	8.5±1.2bc	6.4±1.6ab
G3C-ASB	10.7±1.1c	9.6±2.1c

 

 

 

 

 

*Means with same letter are not significantly different

The self-etch adhesive CSE with PVM/MA copolymer showed the highest bond strength to dentinal surfaces without thermocycling. CSE without copolymer provided the strongest bond in the post-thermocycling group. Copolymer incorporation had varying effects on bond strengths; it improved performance of CSE in the immediate and of ASB in the aged (TC) group, but had no influence in the other groups. Thermocycling significantly decreased bond strengths in all test groups except for ASB.

Conclusion: PVM/MA copolymer incorporation has varying effects on the bonding capacity and durability of different adhesive systems.