Crown cementation is an essential part of ensuring successful outcomes. In this article, adapted from Dr. Ruiz’s book, Supra-Gingival Minimally Invasive Dentistry: A Healthier Approach to Esthetic Restorations, we go through the what the cementation of full crowns looks like in different scenarios.
Preparation for a full-coverage all-ceramic crown
Crown preparations that are supragingival minimally invasive are encouraged. As tooth preparations are performed to create space for the restorative material, remove caries and old failing restorations, and to facilitate laboratory fabrication the choice of material will dictate the amount of tooth to be removed. Conversely, the amount of remaining tooth structure and gingival margin location will dictate the choice of material. On top of this, in cases where an old crown is being replaced, the goal will be to limit further tooth reduction.
One material does not fit all situations, so the table below shows tooth conditions and the best choice of material based on the conditions.
Choice of material and tooth condition
| Tooth condition | Material |
| Crown option based on condition of existing preparation | Best restorative material option and cement |
| Subgingival margins | Zirconia layered or monolithic (RMGI) |
| Supragingival margins with medium esthetic | Layered zirconia (RMGI) or lithium disilicate (resin) |
| Supragingival margin and highly esthetic | Lithium disilicate (resin) |
| Second molar/esthetics do not matter | Full zirconia or gold (RMGI) |
The tooth prep technique is similar to the familiar PFM crown preparation but different material requires different amounts of space and reduction. Occlusal reduction will be completed first, then axial reduction with a chamfer diamond in three planes, as teeth have three different planes.
Cementation of full crowns: two scenarios
The choice of cementation material for full crowns is very important and is driven by the location of the margin and the condition of the tooth.
Subgingival margin cementation
The ideal cement for a crown with existing subgingival margins is RMGI. The rationale for this preference is that RMGI, such as Meron Plus AC (VOCO) [1] or RelyX Luting Cement (3M), is the most forgiving of all restorative cements where there is moisture or contamination [2].
Subgingival margins make it very difficult to have 100% predictable isolation (Figure 1), and ensuring that there is no contamination from saliva, blood, or crevicular fluid is a must with bonded resin cement. Sandblasting the intaglio surface of the zirconia crowns with Siljet, followed by a coat of ceramic primer, and then cementing the crown onto a nicely clean and dry tooth (not desiccated) with RMGI cement will provide simple, sensitivity-free, excellent results.
Figure 1: Subgingival margins are difficult to isolate.
Cementing crowns with resin cement
Without a doubt, a crown will have superior retention if it is bonded with resin cement [3]. However, bonded resin cement needs perfect isolation, which is extremely difficult to achieve with subgingival margins. Even if the isolation requirement can be met, the question should be asked whether resin cementation is, in fact, necessary for super-strong ceramics such as zirconia. In general terms, zirconia does not need resin cement and, over the long term, bonding all zirconia crowns will end up being a nightmare for the future, as removing this restoration is extremely difficult. When bonded cementation is actually necessary because of a lack of retention (and isolation is achievable), resin cements are excellent.
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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
- Ehlers V, Kampf G, Stender E, Willershausen B, Ernst CP. Effect of thermocycling with or without 1 year of water storage on retentive strengths of luting cements for zirconia crowns. J Prosthet Dent, 2015; 113(6): 609-615.
- Shimazu K, Karibe H, Ogata K. Effect of artificial saliva contamination on adhesion of dental restorative materials. Dent Mater J, 2014; 33(4): 545-550.
- Piwowarczyk A, Lauer HC, Sorenson JA. In vitro shear bond strength of cementing agents to fixed prosthodontic restorative materials. J Prosthet Dent, 2004; 92(3): 265-273.