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Effect of different bonding agents on shear bond strengths of composite-bonded porcelain to enamel.

STATEMENT OF PROBLEM
The use of bonding agents in the luting procedure for porcelain laminate restorations to enamel is not clear.


PURPOSE
This study evaluated the shear bond strength differences between an enamel-luting composite and a heat-pressed ceramic with 6 different bonding systems.


MATERIAL AND METHODS
Seventy standardized heat-pressed IPS Empress ceramic discs (4-mm diameter, 3-mm height) were prepared. A vertical planar enamel-bonding surface was prepared on the buccal or lingual enamel of 70 freshly extracted sound human molars and premolars. The teeth were oriented to maintain a parallel relationship between the bonding plane and the shear loading axis of a universal testing machine. Tooth specimens were divided into 7 groups (n=10) comprising equal numbers of molars and premolars. The enamel surfaces of specimens in groups 1 through 6 were prepared with 1 of 6 bonding agents (Scotchbond Multi Purpose Plus, Heliobond, PQ1, SE Bond, Prime&Bond NT, and Prompt L-Pop). Finally, the specimens were luted to the ceramic discs with the composite cement (Opal Luting Composite). Ceramic discs in the seventh group (Control) were luted to the etched enamel with the composite cement without using bonding material. Enamel-ceramic specimens were kept in distilled water at room temperature for 30 days after cementation. All specimens were shear loaded axially in a universal testing machine with a crosshead speed of 0.05 mm/min until fracture. Shear bond strength was measured and recorded for each group in MPa. To determine the statistical significance of the differences between the mean shear bond strength values, a 1-way analysis of variance was used (alpha=.05). Post-hoc multiple comparisons were made with Duncan's multiple range analysis. Fractured surfaces of each specimen were also inspected with a stereomicroscope to evaluate failure modes.


RESULTS
A 1-way analysis of variance revealed significant differences between the test groups (P=.00). Bond strength values (MPa) from the highest to the lowest were as follows: Prompt L-Pop, 25.46 +/- 5.6; Prime&Bond NT, 18.99 +/- 4.93; Heliobond, 17.28 +/- 4.0; SE Bond, 16.21 +/- 2.6; PQ1, 15.60 +/- 2.8; Scotchbond MPP, 14.82 +/- 2.4; and Control, 10.55 +/- 1.6. Duncan's multiple range post hoc analysis exhibited significant differences between the control group and the adhesive bonding agent groups (P<.05). There were also significant differences between the bonding agent groups (P<.05). Prompt L-Pop showed the highest bond strength values.


CONCLUSION
Within the limitations of this study, bonding agents appear to have a strengthening effect on the shear bond strengths of the enamel/composite/porcelain interface of the materials tested. Bonding agents used in this study showed similar bond strength values except for Prompt L-Pop, which demonstrated the highest bond strength values.