For PFM (porcelain-fused-to-metal) crowns, what is the recommended occlusal clearance?

The recommended occlusal clearance for porcelain-fused-to-metal (PFM) crowns is vital for ensuring structural integrity and longevity of the restoration. The correct choice specifies a functional clearance of 1.5 to 2 mm and a non-functional clearance of 1 to 1.5 mm.

This range is important for several reasons. The functional occlusal clearance, which is the space allowed when the opposing teeth come together during chewing or biting, needs to be sufficient to accommodate the thickness of the porcelain layer while ensuring that the metal substructure is not exposed. A clearance of 1.5 to 2 mm provides adequate space to prevent fracture of the porcelain and allows for proper contour of the crown, leading to optimal aesthetics and function.

Furthermore, the non-functional occlusal clearance pertains to areas of the crown that do not experience significant stress during occlusion. A clearance of 1 to 1.5 mm in these areas allows for a stable occlusion and adequate support for the restorative material without compromising the overall strength of the crown.

Choosing this range helps to balance the needs for both aesthetics and durability, ensuring that the PFM crowns can withstand the forces of mastication while maintaining an appealing appearance.