Effect of burn-out temperature on magnetic keepers in cast noble metal alloy posts

Statement of problem Early loss of magnetic keepers in cast gold posts is seen in clinical practice. Purpose The purpose of this vitro study was to investigate the effect of burn-out temperature on the retention of magnetic keepers in cast gold alloy and on the thickness of the oxide layer at the keeper-alloy interface. Material and methods One hundred and five keepers (Magfit EX) were cast with gold alloy (Protor 3) at 3 different burn-out temperatures: 500°C, 600°C, or 700°C (n=35). To test for retention of keepers, 60 specimens (n=20) were tested to failure in tension mode in a universal testing machine (UTM); 45 specimens (n=15) were sectioned, and the interface was evaluated under a scanning electron microscope (SEM). Tensile force data were analyzed with 1-way ANOVA, and SEM data were analyzed with 1-way repeated measures ANOVA. Bonferroni multiple comparisons were performed for post hoc analysis (α=.05). Results Retention of the keepers was significantly higher at lower burn-out temperatures ( P