Which margin design is least likely to be supported during restoration preparation?

The feather edge margin design is the least likely to be supported during restoration preparation due to its minimal thickness and lack of defined structure. This type of margin typically tapers to a very sharp point, which can create an unsupported area of restoration. The thin edge provides insufficient surface area for bonding and can lead to challenges in marginal integrity, making it less effective for holding restorations securely in place. As a result, restorations with a feather edge margin may be more prone to failure or debonding over time compared to other margin designs.

In contrast, the other types of margins presented offer more structural support. A chamfer margin has a rounded edge that facilitates a clear demarcation for restorative material while providing adequate support. The shoulder margin is thicker and provides a flat area that enhances the strength of the restoration. A beveled shoulder further improves retention by increasing the surface contact area for bonding. These features make them more effective for maintaining the integrity and longevity of dental restorations.