What design should the gingival margin have on the proximal and lingual sides of a metal ceramic crown?

The gingival margin of a metal ceramic crown should typically have a chamfer design on the proximal and lingual sides. A chamfer margin offers a smooth transition that facilitates the proper coping of the crown and enhances the overall aesthetics and function of the restoration.

The chamfer design creates a gentle rounded internal line angle, which allows for adequate support of the metal framework while also accommodating the required thickness of porcelain for esthetic purposes. This design reduces the risk of porcelain chipping and improves the strength of the crown. Additionally, the chamfer margin provides an easier path for finishing and polishing, which can enhance the marginal fit and seal, ultimately leading to better clinical outcomes.

In contrast, a shoulder margin is typically used in specific aesthetic areas where a more pronounced and defined margin is desired, while a beveled shoulder provides additional alignment but is not the most suitable for the proximal and lingual sides where a more subtle design is required. A feather edge, on the other hand, is less desirable in a metal ceramic crown as it might compromise the strength and durability of the restoration over time.