In a previous article I discussed the difference between reduction and room when it comes your preparations. In this article I'll go into more depth when it comes to reduction guides and provisional matrices.
When it comes to fabricating reduction guides or matrices for provisionals, it's best to work off of a stone duplicate of the diagnostic wax-up. This eliminates the risk of damaging the wax-up. It also allows me to use a thermoplastic material such as Copyplast rather than being limited to PVS materials.
When it comes to reduction guides I find PVS materials to be drastically more accurate and beneficial. These materials come in two classes: Addition Reaction and Condensation Reaction. While Condensation Reaction materials are often used in labs and typically less expensive, I personally find them greasy and messy to use. For this reason I prefer Addition Reaction materials such as Zhermack's Platinum 85. Not only is it very accurate it's also stiff, which means the guides being fabricated do not have to be overly thick to maintain sufficient rigidity and accuracy.
Typically I like to fabricate two reduction guides. The first I cut horizontally across the facial leaving the lingual intact to allow me to check both incisal and facial reduction. The second I like to cut horizontally again but this time through both the facial and lingual, which allows me to check my lingual reduction and interproximal reduction, and double-check my facial reduction.
For years I used PVS materials, and while they worked well, I now prefer a Copyplast matrix for my provisionals for three reasons. First, it's clear and I can place it over the preparations and use it as one more reduction guide. Second, I find a Coplyplast matrix gives me much better surface detail. And finally, since it's clear it allows the use of light cure materials.
John R. Carson, DDS, PC, Spear Visiting Faculty. [ www.johnrcarsondds.com ]