Effects of Instrument Lubricants on Hardness of a Resin Composite

Objectives: The aim of the study was to evaluate the effects of different instrument lubricants on surface microhardness of a microhybrid resin composite after immersion of acidic beverages.
Methods: 180 disc-shaped specimens of a resin composite(Filtek Z250) were prepared in plastic molds(8mmx2mm) according to lubricants tested(6 groups, N=30). G1.Control(no lubricant was used) G2.Ethanol G3.Etch&rinse Adhesive(Adper Single Bond 2) G4.Self&etch Adhesive(Cleafil SE Bond)(use of adhesive bottle only) G5.Universal Adhesive(G-Premio Bond) G6.Bisco Modeling Resin. Within lubricant groups, the plugger was dipped into lubricant, resin composite was sculpted and covered with a Mylar strip. A glass slide was placed above and the resin composite was polymerized with a LED curing unit for 20 s. The specimens were kept in distilled water for 24 hours at room temperature. The Vickers hardness number(VHN) was assessed using a microhardness tester. Three indentations were made on the specimen surface under a 200 g load with a 15 s dwell time. Following the baseline measurements, finishing and polishing procedure was accomplished and microhardness was measured. Then, each group was divided into three subgroups according to the acidic beverages tested(n=10): A. Distilled water B.Orange juice C.Cola drink and microhardness was measured after the immersion period. The data were statistically analyzed(p<0.05).
Results: There was a statistically significant difference between the control and lubricant groups and modeling resin group has the lowest microhardness values(p<0.05). Although, finishing and polishing procedure improved the microhardness values in all groups, significant difference was found between the control and lubricant groups, except the ethanol(p<0.05). Acidic beverages affected microhardness in all groups , except the universal adhesive used as a lubricant(p<0.05).
Conclusions: Within the limitations of this study, instrument lubricants showed adverse effects on the surface microhardness of resin composites and may not be recommended.