The Self Adhesive Veneer Cement Group
Denali introduced, in 2008, the first self adhesive veneer cement. Just like the self adhesive resin cements, others are now jumping in too. Before too much confusion ensues, I would like to break down the intent of this product category and adjunct product selection, notably bonding agents.
Veneers today come in many different materials, thicknesses, and with a variety of different placement protocols. Up until 2008, and Aura Veneer Cement, all required the use of bonding agents. Not being afraid to jump into a new, more efficient way to practice dentistry, we introduced Aura Veneer Cement, that does not require bonding agents. Read on. Recall the different placement protocols part. The trend in veneers is a conservative, minimal prep design with very little or no enamel preparation. The key element here is that we are still in enamel. Today the best bonding to enamel still starts with acid etching with phosphoric acid. The so-called SE bonding agents are intended for dentin, not enamel, just read the directions carefully when it comes to un-cut or minimally cut enamel. To my knowledge only one bonding agent claims to be effective on un-cut enamel (call for the name, don't worry its not mine). Truly robust bonding agents also exist, call for this recommendation.
Back to veneers. So for placement on enamel, Aura Veneer recommends acid etching enamel and does not suggest the use of dentin bonding agents on enamel. Bonding agents are not only not necessary, but are counter-productive (this will be my next blog). Bond strength to etched enamel has been shown to be more than sufficient, but again the proof is in the pudding, see our documented cases. (Just ask yourself, have you ever had to take off an old veneer that was bonded to enamel? Staining at the margins, right?, this is why it had to come off. Well bonded though right, but what did it look like underneath?
Below, on the left, are veneers bonded many years ago. The teeth show inter-proximal staining, which required removal of the veneers. Shown next, are the same teeth after the veneers have been removed. Inter-proximal decay is evident. This illustrates the point of leaking veneers that were bonded many years ago, using a bonding agent.
Next in placement protocol comes significant enamel reduction, with a mixed surface of enamel and dentin. Here some bonding agent may be beneficial, the choice is yours. The self etching bonding agents are preferred by some using Aura Veneer Cement so they don't have to use phosphoric acid. Acid etching however is another alternative. When it comes to sclerotic dentin, or all dentin, then use of a dentin bonding agent is recommended.
Maybe we've come full circle. We are now fully in dentin, and have the choice of what cement and bonding agents to use. At this point you may ask why not just use a traditional self adhesive resin cement or a glass ionomer. The reasons why not, are at least two. The self adhesive resin cements are all dual cure and notoriously suffer from yellowing. Glass ionomers, even the resin modified variety, must contain water and therefore are more soluble than resin cements. Remember we are after a long-term aesthetic result. Yellowing and staining a few years down the road is not acceptable today.The second reason is that veneers are more prone to coming off as opposed to a crown (less retention, particularly lateral forces), recall those of you old enough - what used to happen to veneers in the early 1980's? So for these reasons when it comes to dentin only, go ahead and use a dentin bonding agent. I have fought this battle before with the self adhesive resin cements, I know many of you are in love with your bonding agents and with shear bond strength testing. But please, if possible, keep the bonding agent away from the margins! As promised I will show you why next time.
Meanwhile check out some of our clinical cases using Aura Veneer and Aura VLC, many thanks to our talented clinicians for supplying them!
Thanks again. Chime in! I look forward to your comments.
Posted by Dr. Jan Stannard at 2:00 PM