In general when preparing teeth for veneers, my goal is to be as conservative as possible and leave everything in enamel. This would mean leaving the interproximal intact and not preparing through the contact. Unfortunately, depending on the clinical situation this may not always be possible or recommended.
This article will address the clinical situations that are encountered in practice that I feel necessitate breaking the interproximal contact.
Existing interproximal restorations
In a majority of clinical situations, if a Class III restoration is present, I will prepare through the contact in order to get beyond the composite and place the margin on sound tooth structure. (Figures 1a, b and c)
In these situations, I will also typically replace the existing composite during tooth preparation so I know it is sound. The risk of placing the margin on the existing interproximal restoration is micro-leakage, which may lead to discoloration/caries.1
It must be noted that there are times in which I will leave my veneer preparation on composite with the idea of being more “conservative” with the preparation. Generally, the existing interproximal restorations in these situations extend much farther onto the palate – so much so that if you wanted to get beyond the restoration, you would end up preparing the tooth for a partial crown. In these circumstances, it is critical to replace the existing composite and place the veneer margin through the contact on the palatal surface so that it is accessible if/when future leakage occurs.
Diastemas/triangular-shaped teeth/open gingival embrasures
It is imperative to prepare teeth with diastemas or black triangles through the interproximal embrasure and place the margin at the interproximal-palatal line angle. (Figures 2a, b and c)
This allows the technician the ability to close the diastema while maintaining a smooth emergence off of the preparation. In addition, the tooth preparation in these situations needs to be dropped subgingival for the same reason of creating a natural subgingival emergence profile that is easily cleansable.
Significant color change is desired
The more dramatic the color difference between the natural tooth and the desired veneer restoration, the more apt I am to prepare through the interproximal. (Figures 3a, b and c)
The main goal here is esthetics Moving the margin more palatally removes the risk of seeing the junction or show-through from the tooth.
It is interesting to note that when you combine the above clinical scenarios with the many other reasons why veneers would typically be placed, you will find that it is not uncommon for the preparation to break the interproximal contact.
1. Peumans M, De Munck J, Lambrechts P, Vanherle G, Van Meerbeek B. A prospective ten-year clinical trial of porcelain veneers. Journal of Adhesive Dentistry. 2004;6(1):65-76.
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Gregg Kinzer, D.D.S., M.S., Spear Faculty and Contributing Author