Preparation designs for porcelain veneers have varied dramatically over the years. We began utilizing them as a conservative alternative to full coverage and strove to do a minimal prep. Then the pendulum swung back the other way and we were doing much more reductive veneer designs. Now we are moving back to thinner and smaller pieces of porcelain, replacing just corners, and even no prep restorations.
- To Create an undetectable interface at the margin. One way to create a smooth interface at the margin is to place a cervical margin on the tooth that the porcelain can be placed against.
- Correction of alignment issues. When teeth are out of alignment and we want to create the appearance they have been straightened int he final restorations. Labially positioned surfaces will be prepped back, while lingually positioned surfaces can simply be added to.
- Increase effectiveness of enamel bonding. Roughening or breaking the surface of enamel can contribute to increased bond strengths to enamel.
- Make room for .5 mm or more of porcelain. If teeth are the proper shape and size and in the right position, and we want to cover the enamel to alter color or correct hypoplasia we need to “make room” for the porcelain.
- Convenience. The prep, even minimal in nature gives us a reference when fabricating and seating the restoration.
- Invisible Margin. When altering color with the veneer we prepare the tooth to place the interface between the porcelain and natural tooth in a position that is not visible.
There are clinical situation where “no prep” is completely appropriate, and others where a veneer may look more like a 3/4 crown. When I plan for veneers I look at the existing tooth condition and the proposed outcome and these dictate what the prep needs to look like.