الفهرس 
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Abstract
Aim: This in vitro study was carried out to assess the marginal accuracy of VITA SUPRINITY crowns which were prepared with conservative feather edge margin design (intervention) compared to deep chamfer margin design (control).
Materials and Methods: twenty crowns were constructed which were divided into two equal groups, group (I): Ten crowns (n=10) fabricated with deep chamfer marginal design (control), group (II): Ten crowns (n=10) fabricated with feather edge marginal design.
Two stainless steel dies were constructed, one die was prepared with deep chamfer marginal design (0.7mm) and the other with feather edge marginal design (0.25mm). Then each die was duplicated into ten epoxy resin dies (for each group). After that, each die was scanned then crowns were milled. Crowns were then seated on their epoxy resin dies and then marginal gap was measured by scanning electron microscope (SEM). Crowns were then cemented by adhesive resin cement. All samples were subjected to thermo-mechanical aging. After that, marginal gap was then measured by the same way. Data was recorded, tabulated and statistically analyzed.
Results: With regard to the effect of margin design, It was found that deep chamfer margin design recorded statistically non-significant higher marginal gap mean value (27.20 ± 3.52 μm) than feather edge design (26.21 ± 1.49 μm). Irrespective of the margin of preparation design, Marginal gap before cementation recorded lower mean value (11.89±2.13 μm) than after cementation under thermo-mechanical aging (41.97 ± 3.68 μm) and this was statistically significant as indicated by paired t-test (p=<0.0001< 0.05).
Conclusion: Monolithic zirconia reinforced lithium silicate (VITA SUPRINITY) ceramic crowns fabricated with feather edge margin design yielded comparable marginal accuracy as that obtained with deep chamfer margin design. Feather edge margin design could be a promising conservative alternative to deep chamfer margin design with regard to marginal accuracy. Cementation affects the marginal accuracy negatively with both tested margin designs.