Effect of food-simulating liquids on the shear punch strength of composite and polyacid-modified composite restoratives

This study evaluated the effects of food-simulating liquids on the shear punch strength of two composites (Tetric Ceram [TC], Vivadent; Esthet X [EX], Dentsply), a conventional (Compoglass [CG], Vivadent) and a posterior polyacid-modified (Dyract Posterior [DP], Dentsply) composite. Thirty-two specimens (10-mm in diameter and 1.6-mm thick) of each material were made, randomly divided into four groups of eight and conditioned for one week as follows-Group 1 (control): air at 37degreesC; Group 2: distilled water at 37degreesC; Group 3: 75% ethanol-water solution at 37degreesC and Group 4: heptane at 37degreesC. After conditioning, the specimens were restrained within the test apparatus and subjected to shear punch strength testing using a 3.2 mm diameter punch at a crosshead speed of 0.5 mm/minute. The shear punch strength of the specimens was computed and the data was subjected to ANOVA/Scheffe's tests at significance level 0.05. The effect of food-simulating liquids on shear strength was found to be material dependent. All materials with the exception of EX were significantly weakened by ethanol solution. For DP, a significant increase in strength was observed after conditioning in water. EX was significantly stronger than TC and DY after conditioning in air, water and ethanol solution. The shear punch strength of EX and CG was significantly higher than DY after conditioning in heptane.