Effects of thermocycling on the margins of transitional acrylic resin crowns

Transitional resin crowns were subjected to thermocycling and examined for marginal integrity since disturbance of the marginal seal is detrimental. Two groups of 10 crowns, one with a chamfer and the second with a shoulder finish line, were subjected to two series of 2500 thermocycles. In the first series, the crowns received cold thermocycling and in the second, hot thermocycling. Impressions were made of the facial margins before thermocycling, after cold thermocycling, and after hot thermocycling. The impressions were analyzed for loss of marginal integrity and changes in axial contour. Cold thermocycling resulted in only limited deterioration, but the changes after hot thermocycling were more pronounced. Tooth preparation designs did not influence the effects of thermocycling.