Biaxial Flexure Strength of Composites Treated with Liquid Polishers

Objective: To determine if a polymerizing sealing resin used in lieu of a polishing procedure affects the tensile strength of a composite, as measured by the biaxial flexure test.

Methods: Composite discs of 13 mm diameter and 2 mm thickness were made from a universal composite (AElite All-Purpose Body, Bisco Inc. Schaumburg IL) using a split mould, mylar isolation and light curing with a Halogen light. Five different surface treatments were used: G1 No polishing, just cured against a mylar strip, G2 Sanded using 600 grit paper, G3 Durafinish, (Parkell Inc) G4 Lasting Touch (Dentsply-Caulk), G5 Biscover LV (Bisco Inc). Specimen were stored 24hrs at 35deg C prior to the Biaxial Flexure test (cross head speed 10 mm/min). There were 6 specimens per group. The polished side of the specimen was supported by the 3 support bearings, being the side under tensile load.

Results: The mean Biaxial flexure strength (and S.D.) was for G1 108.7(27.5), G2 122.9(19.2), G3 130.6(26.4), G5 123.7(18.5) and G6 63.3(15.3), all in MPa.

Statistical analysis , using the Tukey-Kramer HSD comparison, show no significant differences between Groups 1 through 4, and Group 5 significantly different from all other groups at p=0.05.

Conclusions: For group 5 the tensile strength was reduced by the application of the liquid polish. For all the other groups, the biaxial flexure strength did not change significantly with any of the finishing methods, suggesting that some but not all liquid polishers can be considered for clinical application, without detriment to the tensile strength of the composite

The donation of materials provided by Bisco Inc and Dentsply-Caulk is hereby acknowledged.