Effect of surface topography on the bond strength of a composite to three different types of ceramic.

STATEMENT OF PROBLEM

Mechanical retention based on the surface topography is critical for the success of chairside repair of chipped or fractured ceramic prostheses with a composite.

PURPOSE

The purpose of this study was to investigate whether the tensile bond strength of a composite to 3 dental ceramics was affected by surface roughening procedures on the ceramics.

MATERIAL AND METHODS

Three ceramics, Eris (ERV), Empress 1 (E1C), and an experimental ceramic (EXC), were used to fabricate 12 rectangular blocks (5 x 5 x 10 mm). After polishing with a series of SiC papers (120 through 1200 grit size), 4 surfaces were created on each ceramic as follows: 1) as-polished (P); 2) airborne-particle abraded with 50 microm Al(2)O(3) (A); 3) etching with 5% hydrofluoric acid gel (E); and 4) a combination of airborne particle abrasion and etching (A/E). An adhesive (Heliobond) was applied on the roughened ceramic surface and a composite (Tetric Ceram) was built-up incrementally. Twelve groups of different ceramic/surface treatment combinations were prepared. Twenty ceramic/composite specimens per group (0.9 x 0.9 x 20 mm) were obtained from each block with a slow speed diamond saw. Each specimen was subjected to a tensile force at a crosshead speed of 0.5 mm/min using a universal testing machine until failure. The mode of failure was determined by scanning electron microscopy. ANOVA and Duncan's multiple range test (alpha=.05) were used to analyze the bond strength values.

RESULTS

Specimens of all as-polished groups and EXC(A) group separated during sectioning. The mean bond strength values (SDs) in MPa for the remaining groups were as follows: ERV(A): 2.6 (0.8); E1C(A): 2.8 (1.1); ERV(E): 3.1 (1.3); ERV(A/E): 9.3 (1.3); E1C(E): 10.5 (1.5); E1C(A/E):13.5 (3.3); EXC(E): 19.2 (4.7); and EXC(A/E): 23.1 (5.4). ANOVA showed statistically significant differences in the bond strength for both ceramics (P<.0001) and surface treatments (P<.0001). Duncan's analysis yielded following statistical subsets of the bond strength values: EXC > E1C > ERV by ceramic; A/E > E > A by surface treatment. The mode of failure was a combination of adhesive and cohesive failures.

CONCLUSION

The tensile bond strength of a composite to ceramic was significantly different depending on the surface topography of ceramic. Among the surfaces investigated, combined surface roughness was the most effective surface topography in terms of the bond strength increase.