A quality assessment of the casting process on magnetic keepers: Basic science research

Abstract

Purpose: The objective of this study was to qualitatively investigate the effect of the burn-out (mold) temperature, investment material, and casting alloy on the surface integrity of the Magfit EX keeper. Materials and Methods: Forty-two Magfit EX keepers were waxed-up, invested in five investment materials (Beauty-Cast, Cristobalite, CM-10, Cera-Fina, Castorit-super), and subjected to burn-out temperatures ranging from 450 to 700°C at intervals of 50°C. The keeper samples were then cast into copings with three alloys (Castwell, Protor 3, Optimum) under standard conditions. The keeper surfaces were then examined under a microscope, and the compositions were assessed by an X-ray micro-analyzer in a scanning electron microscope (SEM). A new keeper served as control. Results: At a burn-out temperature of 550°C, the keeper surface started to disintegrate. X-ray micro-analysis showed an increase in oxygen content with increasing temperature. At 700°C, the keeper surface disintegrated, and the composition differed markedly from that of the new keeper. The keeper surfaces were intact with all investments except those with Beauty-Cast. The keeper surfaces were found to be damaged when the casting alloy was Optimum. Conclusions: Beauty-Cast investment with a burn-out temperature of 700°C is unsuitable for casting the Magfit EX keeper-coping unit. Also, high fusing alloys are not recommended for casting Magfit EX keepers. © 2007 by The American College of Prosthodontists.