The successful placement of porcelain veneers requires careful consideration of multiple factors, with cement selection being a crucial component. This article explores the key considerations in cement selection, pre-treatment protocols, and clinical techniques for achieving predictable results with porcelain veneers.
Combined with the fact that anterior porcelain veneers should be thin and light activation is predictable, light-cured cement ideal for porcelain veneers.
The most important characteristic of the cement is the proper translucency and the cement’s to enhance the blending of a thin, translucent restoration. Opacious cement would be contraindication. The market is full of veneer cement systems that offer different colors and levels of translucency.
Key determinants of final restoration
The most important determinants of the final shade and opacity of the finished restorations are the tooth (preparation) color and the type, and thickness of the ceramic veneer [1]. The veneer cement will influence the final color [2] to a lesser extent, unless opacious cements are used, but we already know that if supragingival margins are desired, opacious cement is contraindicated.
Some techniques suggest using the cement to dramatically alter the color and value of the final restoration, or to mask the color under the restoration. This technique can be very complicated and can lead to some esthetic failures. Especially problematic are cases where there are variations of shade between the prepared teeth (Figure 1), and the different veneer and cement thickness, all which will make the perfect selection of different cements difficult and unpredictable.
Figure 1: Difference in color on prepared teeth is very difficult and unpredictable to manage using different colored cements.
Pre-treatment color management
It is preferable to alter the color of the teeth prior to preparation by bleaching, internal bleaching or other means, and to allow a knowledgeable technician to undertake the necessary masking on the porcelain, as this will greatly simplify the results.
Occasionally, a very difficult area such as a deep stain can be blocked out with a fully opaque flowable composite, (such as Accolade OP Mask), which can be placed on the tooth before the impression is taken. The technician should always receive a photograph of the teeth next to a shade tab or tabs, if there is difference in shade between the teeth or parts of the tooth.
Try-in procedure
Trying-in the veneers before choosing a final cement is very important, as this will allow the clinician to have a preview of the approximate final shade. Most try-in pastes are not accurate. The clinician can perform the try-in procedure using a try-in paste with a good true-to-color characteristic, or with water.
An accurate approach is to use Accolade PV Cementation System (Danville), which has a very accurate try-in “composite”. This try-in composite has no light-cure initiators and the shades are adjusted to accurately duplicate the shade and translucency of the light-cured composite. By using composite and not a substitute such as glycerine-based pastes, a source of veneer bonding problems is eliminated. The try-in composite need not be fully removed and the residual polymerized by “diffusion polymerization” when the composite is light-cured [3]. It is important to remember that if Accolade PV try-in paste is being used, the intaglio surface of the veneer must have been prepared with porcelain etch and silane.
Cement selection and shades
Dr. Ruiz’s preferred choice is to assess the final shade with water as the medium to visually connect the veneer and the tooth. This will give the clinician a close idea as to how the final restoration will look with a fully clear cement, or without the influence of the cement, and from that point it is easier to select a cement option to either maintain the current value and brightness, or slightly increase or decrease them. Trying to change the shade with a cement is extremely complicated , as the possibilities are endless (Figure 2). For this reason, it is best to allow the experienced laboratory technician to have most of the control of the final shade and translucency, based on the existing tooth color. Small, final adjustments are done with the cement at the chairside, guided by the try-in procedure.
Figure 2: Try-in case with cement.
Dr. Ruiz uses a simple and highly predictable approach of three translucent veneer cements with slightly different values or brightness (degree of witness or blackness), which will be selected as the try-in.
A light shade of cement, which is usually used for shade A1 or similar, will virtually maintain the same shade and level of translucency, with an insignificant increase in value achieved with the combined color of the tooth and the veneer. An extra-light cement used for shades B1 or 1M1 (the shades Dr. Ruiz most often uses for porcelain veneers) will very lightly enhance the value and brightness of the final restoration with an insignificant decrease in translucency. A less frequently used yellow or universal shade used for shades A2 or darker will maintain the warm effect of darker shades without opacifying them. Dr. Ruiz also uses the Accodate PV shades light, extra-light, and yellow, because of their high degree of translucency.
Experience shows that a fully translucent or clear shade is undesirable because if there is an opening on the veneers, as often is the case, the clear cement will show grey and will adversely affect the esthetic results (Figure 3).
Figure 3: Observe, on the mesial margin of onlay cementation with clear cement, an apparent “gap”. In reality, the margin is closed, but the clear cement appears to be missing.
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Disclaimer: Los Angeles Institute of Clinical Dentistry & Ruiz Dental Seminars Inc. uses reasonable care in selecting and providing content that is both useful and accurate. Ruiz Dental Seminars is not responsible for any damages or other liabilities (including attorney’s fees) resulting or claimed to result in whole or in part, from actual or alleged problems arising out of the use of this presentation. The techniques, procedures and theories on this presentation are intended to be suggestions only. Any dental professional viewing this presentation must make his or her own decisions about specific treatment for patients.
Sources
- Barizon KT, Bergeron C, Vargas MA, Qian F, Cobb DS, Gratton DG, Geraldeli S. Ceramic materials for porcelain veneers: part II. Effect of material, shade, and thickness on translucency. J Prosthet Dent, 2014; 111(4): 864-870.
- Chang J, Da Silva JD, Sakai M, Kristiansen J, Ishikawa-Nagai S. The optical effect of composite luting cement on all ceramic crowns. J Dent, 2009; 37(12): 947-943.
- Dorsman GJ, Bertolotti RL. Shade accurate composite modified for long preview during veneer try-in. International Association for Dental Research, General Session & Exhibition, June 28-July 1, 2006, Brisbane, Australia. Abstract No. 1140.