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Compressive fracture resistance of porcelain laminates bonded to enamel or dentin with four adhesive systems.

PURPOSE
To measure the compressive strength of porcelain laminates of 0.5 or 1.0 mm thickness when bonded to enamel or dentin using these resin cements: All-Bond 2 + Choice, Panavia 21, Scotchbond + Opal, and Super-Bond C&B.


MATERIALS AND METHODS
The buccal and lingual aspects of human molars were sectioned to prepare specimens at least 3 x 3 x 3 mm in size. Thirty horizontally flat enamel surfaces were prepared with a diamond disc for each group using a milling machine. Ten enamel specimens were randomly selected to test the fracture strength of 0.5-mm thick porcelain laminates without resin cement, and the data were recorded for a control group. The enamel specimens of each group were divided into two subgroups of 15 specimens to bond with either 0.5- or 1.0-mm thick porcelain laminates. Four resin cements were used for bonding of individual groups. All bonded specimens were stored in 37 degrees C for 24 hours before fracture testing. The horizontally flat dentin surfaces were prepared on the fractured bonded specimens using a diamond disc for each group. Ten 0.5 mm porcelain laminates were randomly selected to test the fracture strength on dentin (control group). The bonded laminates to dentin were prepared using the same procedure as for enamel. The fracture strengths were statistically analyzed at alpha= 0.05.


RESULTS
Statistically significant differences in mean fracture strengths between groups were revealed. No significant difference in fracture strengths of control specimens between enamel and dentin was found. Super-Bond C&B provided a higher fracture resistance of porcelain than the other resin cements. Increasing the thickness of porcelain laminate increased the fracture strength. The 0.5-mm thick porcelain bonded to enamel had higher fracture strength than that of 1.0-mm thick porcelain bonded to dentin when using Super-Bond C&B and Scotchbond + Opal cements.


CONCLUSIONS
Bonding techniques and curing systems of resin cements influenced the fracture resistance of porcelain laminates. Dry bonding with auto-polymerization of Super-Bond C&B resin provided the highest fracture resistance of porcelain. Porcelain bonded to enamel with this resin had a much higher fracture strength than when bonded to dentin.