Effect of water temperature during polymerization on strength of autopolymerizing resin

Statement of problem. Breakage is a potential problem of provisional resin restorations. A method that effectively increases the strength of the resin is desirable. Purpose. This stud! examined the effects of the curing environment, air or water, and water temperature during polymerization on the mechanical proper ties of autopolymerizing resin. Material and methods. After mixing the autopolymerizing methyl methacrylate resin for 10 seconds, it was placed in a stainless steel mold (2 x 2 x 25 mm). One minute and 50 seconds after the start of mixing, the mold containi ng the resin was placed under the following conditions: in air at 23 degree s C; or in water at 10 degrees C, 23 degrees C, 30 degrees C, 40 degrees C, 60 degrees C, and 80 degrees C. Sis minutes after mixing began, the resin specimen nas removed from the mold and the transverse test (3-point flexura l test) was performed. Results. Alteration of conditions during polymerization revealed a signific ant effect on both the transverse strength and modulus of the resin (P<.000 1). Both increased with an increase in water temperature. Water conditions of 60 degrees C to 80 degrees C produced more than 2 times greater transver se strength and modulus of the resin compared with polymerization in 23 deg rees C air (P<.0001). Conclusion, Polymerization of the resin in hot water greatly increased its mechanical properties. The method of placing resin restorations in hot wate r during polymerization may be useful for improving mechanical requirements and obtaining long-lasting performance.