I believe it would be a nearly perfect world if the only type of margin I ever cut was supragingival. No retraction issues, no worries about tissue management and margins that any patient can clean with a toothbrush in addition to always bonding to enamel at the margin. Unfortunately I don’t get to always do supragingival margins, but more and more these days I can. In the early years of my practice when my esthetic restoration was a porcelain fused to metal crown with metal margins we placed the margins as far subgingival as possible without violating the biology. Why, to hide the ugly metal ring of the restoration. Today, all ceramic restorations have become esthetic enough that we no longer have to hide our work.
A large majority of the anterior restorations I complete incorporate changes to tooth position, alignment or contour. I aim to balance the required tooth reduction to accomplish the clinical goals with being conservative. Often the changes we are making between the existing tooth position and the proposed tooth position are additive and act to reduce the amount of reduction required. Tooth reduction is challenging enough to get accurate without the added guessing of what will be needed to accomplish the tooth form from a wax-up. Transferring the information from the diagnostic wax-up to the teeth in the form of a mock-up allows me to use my usual technique, cut depth cuts and create the required reduction from the final tooth position, conserving tooth structure.
If you take yourself all the way back to learning preparation design you will remember the term convenience form. Today as we discuss conservative or minimally invasive dentistry what role does convenience form still play, if any? To answer this I went back and looked up the definition of convenience form. You can find many variations, but all of the definitions agree in principle.
Convenience form is defined as that form of cavity preparation that allows adequate observation, accessibility and ease of operation in preparing and restoring the cavity.