Internal Fit of Ceramic Systems Crowns

Objective: To evaluate the internal fit of metal-ceramic (MC), glass-infiltrated alumina (IA), and yttria-tetragonal zirconia polycristals crowns (Y-TZP). Material and Methods: An artificial first maxillary molar was prepared to receive a full crown and then sixty composite-resin tooth replicas of it were acquired. An impression of each tooth replica was made resulting in 60 stone dies, and then were randomly assigned to three groups (n=20) according to core material. The replica technique was used to simulate the cement thickness and to measure the internal fit of the crowns. The crowns were filled with a light body polyvinysiloxane addition silicone and placed onto a corresponding tooth replica and applied vertically 50N load for 10mim. Following, the crowns were removed, and then the silicone film was stabilized by a heavy body silicone. Three slices in a bucco-palatal direction were acquired and measured under a toolmaker's microscope (Mitutoyo) with a magnification of x50 in 9 different areas (3 occlusal, 3 buccal, and 3 palatal). Statistical analysis were performed by One-way ANOVA and the Tukey test (p<0.05). Results: The internal fit (mean ±SD; µm) in the groups were as following: MC 89.76±38.32; IA 158.27±73.85; and Y-TZP 132.54±61.02. The results showed that there was statistically difference of internal fit between groups. The metal-ceramic group presented internal fit statistically significance lower than all-ceramic groups. No difference was found between all-ceramic groups. However when the results were analyzed separately (axial and occlusal surfaces) significant difference was observed between groups in oclusal surface but there was no significant difference among groups in axial measurement. Conclusion: MC showed the lowest internal fit. When the results were observed separately in occlusal measurement the MC was statistically lower than others. However there was no difference between groups in axial surface.