Self Adhesive Cements and Self Adhesive Composites - How to Avoid Failures

The self adhesive cements and self adhesive composites have been around for a long time (not just a year or two as some claim - if you are engaged by this advertising you need to do your homework). For example, those who follow the development of glass ionomers, claim they are the first self adhesive composites, more than 30 years ago. My focus however is not on the resin modified glass ionomers, that today still use triturators, but on the less soluble, single syringe, resin based materials that are also self adhesive. These materials were developed using acidic bonding agents that contain methacrylate phosphate esters or methacrylate carboxylate esters with non-reactive fillers. O.K., no more chemistry. These products have been available for more than 10 years.










Veneer cementation using AURA Veneer cement. Case provided by Dr. Rodger Lawton, Olympia, WA.

The self adhesive cements and self adhesive composites were developed initially to improve bonding to dental materials, not to replace bonding agents or to skip beneficial steps, such as acid etching of enamel. These self adhesive materials have improved bond strength to conventional composites as well as to other substrates. It is when some companies started promoting the "self etching" qualities of these products and indicated that these proven steps could be eliminated, that failures started to occur.

The ability of self adhesive materials does not extend to their ability to sufficiently etch enamel, or provide greater retention to dentin, compared to the use of phosphoric acid etching and use of bonding agents to dentin. The acidity of the self adhesive materials is not low enough to achieve this result, and thankfully so. For those further interested in this subject, I suggest you read some pulp biology on bonding agents, or ask what happens when large quantities of a very low pH material is bulk filled into a tooth. So how do we avoid failures when using these self adhesive materials and still take advantage of their improved bond strength?

To break down this problem I would like to categorize failure into two groups: short-term and long-term. Short term failures occur primarily to deficient bonding. In this case the substrate was not adequately prepared and/or the correct materials were not applied to obtain sufficient bonding. When bonding to enamel, the best approach is to acid etch with phosphoric acid. When bonding to dentin we have two choices, total etch followed by dentin bonding agents, or use of self etching dentin bonding agents. In placing veneers some difficulty may exist in determining whether we are still in enamel or if we have prepared into dentin. The most cautious approach here is to use assume that you have some dentin present, unless you know otherwise. The self adhesive cements now offer improved bonding to the bonding agent.














Multiple crown cementation using AURA VLC, and in this case, careful application of a self etching bonding agent. Case provided by Dr. M.M.

The second type of failure, long term failure, primarily results from leakage, not bond failure. The strength of the bond has already proven itself. Leakage in this case results from fluid passage between the exposed margin and the restorative materials present. The main source of this leakage is from bonding agents, not the composite or resin cement. Bonding agents are primarily solvent filled, porous materials, compared to the self adhesive composites. See our site on Leakage and how to reduce this problem, if you would like more information on this claim.(www.denalicorporation.com/). The accurate placement of dentin bonding agents on dentin, in other words not on, or over the margin if possible, is important. For more information also take a look at my post on "Ever seen a stained composite restoration?"

Today, complex cases (see the ameliogenesis on our web site) can be restored in ways not possible 10 years ago, using these self adhesive materials and modern LED curing lights. Highly aesthetic results are now possible using color stable, light-cured, self adhesive cements to full crowns and veneers.