The marginal fit of a restoration is an important factor for its long-term success. During the fabrication, restorative materials are exposed to stresses. As a consequence, a marginal gap occurs between tooth and the restoration.

Objectives: The purpose of this study was to evaluate the marginal distortion during the firing of porcelain with three different marginal designs.  

Material and Methods: Three marginal designs (shoulder, champher, knife edge) were evaluated in this study. A total of 21 porcelain fused to metal crowns were fabricated. They were divided into 3 groups of 7 crowns each. Metal copings were cast with precious metal. Thickness of the metal was 0.3mm. Dimensional changes were measured around the crown in 9 points in horizontal and vertical plane before and after the porcelain firing cycle with a profile projector (SPS 200 U, SOMET). Results were analyzed with “One-way ANOVA" and "student t test". Results: The results are displayed in the following table.

 

Groups	Shoulder	Champher	Knife edge
Horizontal Def. (µ)	63.7	36.7	113.3
Vertical Def. (µ)	15.75	24.1667	24.0556

 

At the horizontal plane, marginal discrepancy of champher was significantly smaller than shoulder (p<0.05) and knife-edge (p<0.05). Significant differences (p<0.05) were found between shoulder and champher, and knife-edge at the vertical plane. Conclusion: Within the limits of this study, among the marginal designs evaluated, shoulder showed an excellent dimensional stability compare to the champher and knife-edge.