Why is all ceramic restoration considered less conservative than PFM?

All ceramic restorations are often viewed as less conservative than porcelain-fused-to-metal (PFM) restorations primarily because the shoulder margin configuration of all ceramic systems necessitates more substantial reduction of tooth structure. This is due to the requirements for adequate strength and aesthetics in all ceramic materials.

A shoulder margin provides a definitive edge for the ceramic, which is often thicker compared to the metal substructure in PFM restorations. To achieve the necessary thickness for the ceramic to withstand occlusal forces and prevent fractures, more tooth structure must be removed. This creates a less conservative approach since there is a greater loss of natural tooth material required to accommodate the restoration.

Other aspects of all ceramic restorations, such as their aesthetic appeal not relying on metal for opacity, also impact their design but do not directly relate to the conservativeness of tooth structure preservation in the way that margin configurations do. Thus, the design of the shoulder margin in all ceramic restorations clearly illustrates why they require a more invasive approach compared to PFM options.