Objective: Marginal fit is valuated as one of the most important criteria for the clinical quality and success of all-ceramic crowns. The aim of this in vitro study was to investigate the marginal fit of Lava™ Zirconia crown-copings on chamfer and shoulder preparations. Methods: Two acrylic model teeth were selected to simulate the clinical preparations: one molar was prepared with a chamfer finish line (C) and one premolar was prepared with a rounded shoulder finish line (RS). Each resin model was duplicated 10 times using silicon-based impression material and poured in type IV dental stone for the fabrication of working dies. A total of 20 copings were divided into two groups (n=10 for each finish line). Ten measuring locations were chosen randomly along the margin on the dies and the gap width was measured under a light microscope with a magnification of 100X. Measurements were made without cementation. The mean marginal gap widths and standard deviations were calculated and a one-way ANOVA was conducted for different types of preparations in order to detect differences (α=.05). Results: The mean marginal gap was 21±6μm for the C group and 11±6μm for RS group. The 1-way ANOVA showed a significant difference  between  the two groups (P<.05). Conclusions: Within the limitations of this study, the marginal discrepancies were all within the clinical acceptable standard set  at 120μm. The shoulder preparations showed the smallest gap dimension.

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