Effects of occlusal loading and thermocycling on the marginal gaps of light-polymerized and autopolymerized resin provisional crowns

Statement of problem. Resin crowns appear to be increasingly at risk for in creases in marginal gap size as a result of thermocycling and occlusal load ing. Purpose. This in vitro study compared the effects of occlusal loading and t hermocycling on the margins of provisional crowns made from a conventional autopolymerized provisional acrylic resin (Tet) to those made from a light- polymerized resin (Unifast LC). Methods and material. Crowns made from the 2 materials were thermocycled an d loaded on custom dies to simulate 6 to 8 weeks of oral function. Gap size s were measured before and after thermocycling and occlusal loading. Results. Provisional crowns made from light-polymerized resin exhibited sma ller changes in marginal gap size than did those made from conventional aut opolymerized resin. Conclusions. The improved characteristics of the light-polymerized material may prove useful for provisional crowns that must remain for long periods in the oral environment.