Is traditional cement still an option for the cementation of full-coverage restorations? At first glance, it may appear that the adhesive age of dentistry has engulfed us all in the belief that some form of resin cement is used when placing any and all full-coverage restorations. Though there are some full-coverage restorations that require adhesive bonding with resin cement (e.g. Leucite-reinforced glass ceramic, such as Empress and Authentic), there are many other full-coverage restorations that “may” be bonded, but do not require it. These materials include aluminous cored restorations (Procera), zirconia restorations and metal ceramic restorations.
Why don’t we just bond everything? The answer is easy ... bonding takes time and a strict adherence to clinical protocol.
When I go to bond a restoration it generally means that I need to provide anesthetic. I have to isolate the tooth with a rubber dam or cord and clean the preparation with air abrasion.
Depending on the adhesive system being used, I have to be able to maintain isolation during the etching/adhesive application, and I have to make sure to clean up any excess resin after bonding. Depending on the health of the tissue and location in the mouth, this may be easier said than done.
The benefits of conventional cementation are that it is easy, much more efficient and clean up is a breeze. My cementation material of choice is a RMGI (RelyX Luting Plus).
So the real question is, when can we cement our full-coverage restorations and when do we need to bond? My answer is quite easy: if I have adequate resistance/retention form and I am using a restoration that has the inherent strength in the material itself (aluminous cored restorations e.g. Procera, zirconia restorations and metal ceramic restorations), I will conventionally cement the restoration. If I am lacking in resistance/retention form, then I will bond.
The one material that makes things a little more confusing is lithium disilicate (e.max). It has been shown in lab bench studies that bonding monolithic e.max will create a stronger restoration.
However, the clinical studies show that the success rates of bonded vs. cemented e.max is the same (this assumes that adequate tooth preparation is performed).(1) If you have an under-prepared tooth, you should bond the restoration. The recommended prep thickness from Ivoclar can be seen in Figures 1 and 2 above.
Conventional cementation clinical trials. Edelhoff D, et. al. Dtsch Zahnartztl Z 2000.
Gregg Kinzer, D.D.S., M.S., Spear Faculty and Contributing Author