Tensile Strength of Compomers Immersed in Ethanol

Objectives: Immersion in ethanol accelerates leaching of residual monomer from resin composites compared to water (Ferracane et al., Dent Mater 6: 282-287,1990). This study examined the diametral tensile strength of compomers immersed in ethanol. Methods: Three different commercially available compomers: [Reactmer (RE, Shofu), Dyract AP (AP, DENTSPLY-Sankin), and Xeno CF (XE, DENTSPLY-Sankin)] were tested. Disc specimens (6mm in diameter and 3 mm thick) of each compomer were prepared for diametral compression testing. The materials were cured according to the manufacturers’ instructions. After specimens were prepared, each compomer was immersed in either deionized water (Control) or ethanol (99.5%) (Et) at 37°C for 3 days. The diametral tensile strengths of each specimen were measured using a universal testing machine (Instron 4302). The apparent elastic moduli of the specimens were then calculated from the cross head movement-load chart when the strength was measured. Results: The diametral tensile strengths [MPa, Mean±sd, n=4-5] were as follows (Control vs. Et): 39.3±2.6 vs. 43.6±2.7 for RE, 47.9±2.5 vs. 52.5±5.1 for AP, and 55.7±3.1 vs. 60.6±3.0 for XE. Results of the apparent elastic moduli [GPa, Mean±sd, n=4-5] were 9.9±0.2 vs. 11.5±0.6 for RE, 10.1±0.1 vs. 8.9±0.6 for AP, and 10.2±0.2 vs. 10.6±0.3 for XE. A significant increase in diametral tensile strength values was found in materials RE and XE immersed in ethanol (p<0.05); however, there were no statistical differences in strength between Control and Et for AP (p>0.05). Except for AP, the specimens immersed in ethanol had significantly greater apparent elastic modulus values compared with deionized water (p<0.05). Conclusion: The residual monomer and other leachable constituents in the compomers tested could be extracted during ethanol immersion; however, no reduction in strength was observed under the present conditions.