I recently wrote a post about the new ceramics that have exploded onto the market. I felt overwhelmed by the options and was confused about what I should incorporate into my practice. If I was confused about porcelains, I had no idea what was waiting for me when I began to investigate resin cements.
If you’re doing a full coverage, all ceramic crown, then you can certainly use traditional cements (zinc phosphate and zinc polycarboxylate) without committing any major crime that would make your former prosthodontic professor wag an angry finger at you.
But if you do that, you’re missing out on an opportunity to take advantage of adhesive dentistry. Many porcelains have a glassy matrix that can be etched. If it can be etched, it can be bonded.
Let’s look again at my classification of porcelains:
Alumina and zirconia do not have any glass in them, so etching is challenging or impossible. There are some products on the market that claim they can bond to zirconia, but the jury is still out.
Let’s look at my chart of adhesive cements and sort it all out.
Total-Etch: You prepare the tooth surface with phosphoric acid, then apply prime and bond. The pros are it offers the best bond, especially to enamel. The cons are that it can carry the highest rate of post-operative sensitivity.
Examples include: Variolink II, RelyX Veneer, Duo-Link
Self-Etch Primer: You prepare the tooth with a solution that has etch and prime in it. Lower bond strengths but also less post-operative sensitivity.
Examples include: Multilink Automix, Panavia F 2.0
Self-Adhesive: You prepare the tooth with nothing. Etch, prime and bond are all in the cement itself. Lowest bond strengths but theoretically the best at reducing post-operative sensitivity.
Resin-Modified Glass Ionomer: You prepare the tooth with nothing, Etch, prime and bond are all in the cement itself. The chemistry is different from self-adhesive cements and you usually have the bonus of fluoride release from the cement.
Examples include: FujiCEM, RelyX Luting Plus
So when do you use which cement?
If you’re placing a full coverage, all ceramic crown, you can use all of the above. There may be a benefit to RMGI since it is the most tolerant of moisture and can handle subgingival preparations the best.
If you’re placing a porcelain inlay/onlay, I recommend a self-etch primer. It offers the best bond for the least incidence of post-operative sensitivity.
If you’re placing a porcelain veneer, I recommend a total-etch bond. Veneers benefit by having the strongest bond. Also the incidence of post-operative sensitivity is low because veneer preps should rarely extend too far past the dentin-enamel junction.
The other significant factor to consider is whether the cement you are using is self-cure, light-cure, or dual-cure. More opaque porcelain like zirconia or any porcelain thicker than 2 millimeters should not be cemented with light-cured products since the curing light can’t penetrate to the cement as effectively.