CIRCONIA CROWN CEMENTATION
The advancements in aesthetic multilayered high strength zirconia materials allows them to be used in both the posterior and anterior dentition. When adhesive retention is required, moisture isolation is critical to the success of resin-based adhesive cements. However, adhesion to the tooth can be difficult when trying to use traditional resin luting cements due to all the cleaning steps, bonding technique issues and maintaining proper isolation. Traditional crown preparations that have good axial wall height and 6˚-8˚ taper work well with conventional luting cements. Zirconia crowns are no different when the tooth is prepared properly they can be cemented with resin modified glass ionomer cements (RMGIC). RMGIC's have some advantages over resin cementation in that they like moisture, work well on subgingival margins, are not as technique sensitive and they can offer chemical adhesion to zirconia when a ceramic primer is used. RMGIC chemistry is one of only a few moisture tolerant types of cements that can be used to adhere high-strength ceramic crowns to tooth structure, Doxa's Ceramir Cement is another product. Glass ionomer chemistry interacts uniquely with the tooth whereby it hypermineralizes the dentin it contacts, which actually make the area more impervious to acid attacks. Should micro leakage start to happen the tooth actually is more durable from having RMGIC in contact. RMGIC adhesion to tooth structure is very complex and provides true chemical adhesion via an ionic bond with hydroxyapatite which is shown to be durable and long lasting. RMGIC utilization is an easy technique to implement and very forgiving in the presence of moisture. When moisture isolation, preparation margin position and /or heavily affected, deep, dentin is present, an even better choice than resin adhesion and luting cements are RMGICs.
The cementation process is relatively easy. First, the laboratory should deliver the restoration to your office with the intaglio sandblasted with 30 micron aluminum oxide at 35psi. The zirconia restoration should have the intaglio coated with a ceramic primer prior to try-in for improved adhesion. Implementing a ceramic primer on the zirconia restoration allows for the chemical adhesion of RMGI to the ceramic, compared to only mechanical retention when a ceramic primer is not used. One of the best types of ceramic primer to implement has been shown to be one that utilizes MDP (10 Methacryloyloxydecyl Dihydrogen Phosphate) in its chemistry. The restoration can be cleaned with ethanol in an ultrasonic water bath or a steam cleaner after try-in but does not require additional utilization of the ceramic primer. Companies such as GC America Inc. with its Ceramic Primer II utilizes this chemistry to create excellent long-term bonds to resin, zirconia and other ceramics. The resin chemistry within RMGIs, along with an MDP-based ceramic primer allows for a true chemical bond between zirconia, RMGI and tooth structure even in a slightly moist environment.
Many glass ionomer and RMGI materials typically are dispensed in a capsulated form to keep the powder and liquid separate and the material stable. The capsule is activated and triturated to achieve a homogeneous mix of material. This capsulated form is an excellent delivery method; however, some dentists no longer have a need for or even own a triturator. GC America recognizes this issue and their solution is FujiCEM™ 2, a RMGIC that offers high elastic crosslinking monomers which impart increased strength, high fluoride release, low film thickness, and excellent marginal integrity. The innovative and unique delivery system for the GC FujiCEM2 is a paste-to-paste system that has incorporated a new improved cartridge and mixing tip design. The Slide and Lock System is revolutionary for speed, efficiency and ease of use all with no mess.
In this case the decay was removed and a diode laser (AMD Picasso Plus Laser) was used to remove tissue along the preparation margins and to control bleeding such that a glass ionomer buildup material could be utilized (Equia Forte, GC America). The Ceramic Primer II was used on the inside of the crown prior to try-in and the restoration was cleaned with ethanol afterwards. The FujiCEM2 was then utilized to cement the crown in place.
GC FujiCEM 2 provides a fast and convenient application instantly without the need for superfluous ancillary devices to mix traditional capsulated materials. The Slide and Lock system allows for accurate placement and fast efficient delivery with instant cleanup by removing the mixing tip. The RMGI physical properties of GC FujiCEM2 make it ideal in areas where sclerotic deep dentin may provide challenging long term adhesion as well as subgingival margins or difficult isolation. Clean up is a snap as the material can be removed quickly from the tooth and restoration before final set. When moisture control, subgingival margins, and isolation concerns arise this is another great option.