The Issue: Self-Adhesives vs. Glass Ionomers

The Issue: Self-Adhesives vs. Glass Ionomers

Procedure: Proper Case Selection and Understanding Product Attributes

The Conclusion: Self-Adhesives Alone Should Not Be Compared to Glass Ionomers

In using a product that is labeled as a self-adhesive the manufacturer generally is conveying that it contains acidic monomers that provide enhanced adhesion to tooth or restorative material compared to traditional composites based on BIS-GMA or urethane dimethacrylate alone. The following comparisons are therefore often incorrectly made.

Glass ionomers vs. Self- adhesive Cements – Wrong.

Bonding agents and Traditional composites vs. Self Adhesives – Wrong.

Self- adhesives vs. traditional composites without bonding agents– Correct.

Having initiated the self-adhesive resin group nearly 15 years ago, I have seen all of these incorrect comparisons made over the years, and still prominently done so. The goal of self-adhesives, not to be confused with self-etching, was to provide a more adhesive, filled, composite-like material for practitioners. Some have identified them as composites that contain bonding agents. I am O.K. with this. Self-adhesive chemistry has been applied in sealants, cements, flowable composites, and core materials to name a few applications. The goal was to provide a material that would provide some adhesion, but were never intended, at least on my part, to replace bonding agents. Self-adhesives are not low enough in pH to provide self-etching to the extent needed to be called self-etching like self-etching bonding agents. 

Many highly respected clinicians continue to this day to make this mistake by comparing glass ionomers vs. self adhesive resin cements with respect to achieving maximum tooth adhesion and let’s say crown retention. In this case, the correct comparison if someone is trying to achieve maximum bonding to dentin is to use a bonding agent and a self-adhesive material together and compare that to a glass ionomer.

I can guess why some would want to minimize the self-adhesives, if they desire to promote bonding agents, which may have taken some the market away from them, or glass ionomers, as self-adhesives have also achieved many loyal followers. It is not a coincidence that so many companies offer a self adhesive cement, many of these same companies also sell bonding agents, and even a few of them recommend using their bonding agent with their self adhesive cement. Glass ionomer companies?, not so many, remember sensitivity? That is why self-adhesives hold a valuable place in dentistry. Every practitioner in cementing a crown should recognize when the situation that calls for maximum retention, for example a badly broken down tooth with little remaining walls to bond to. This is a case where crowns coming off or a de-bonding failure is not un-expected. This situation while not being the best outcome is lending support to the implant alternative. Choosing not to use the best material or materials is a mistake. 

Are those of you reading along, actually debating whether dentin bonding agents are the material of choice or at least an equal to glass ionomers in dentin bonding? There is no claim that I am aware that states self-adhesives outperform bonding agents with respect to retention. Why then leap to eliminating bonding agents in comparing self-adhesives alone vs. glass ionomers? I would suggest that this is not a good choice as a clinician to make. If in doubt, always use a bonding agent! In promoting self-adhesives I have never tried to talk anyone out of using their bonding agent. To the contrary, from my testing the best bonding pair is a bonding agent with a self adhesive, this also follows the well-known chemistry adage, that “like likes like”, meaning a bonding agent is more similar, in hydrophilic behavior, to a self adhesive than a traditional composite. This was the whole concept in using monomers that are more hydrophilic compared to BIS-GMA or urethane dimethacrylate in creating the self-adhesives.

Each group of materials has there own drawbacks. Bonding agents when left at the margin are a primary source of leakage. Glass ionomers, being made up of some percentage of water are more soluble than composites, and to be fair, self-adhesives by themselves do not provide the maximum tooth retention. So, where does this leave us? Not all cases require the use of bonding agents, and not every case would be compromised by using a material does not provide the maximum retention, such as glass ionomers. The self-adhesives offer a convenient solution by providing fewer steps, less equipment, and rarely sensitivity when the case is not complicated or compromised. Self-adhesives perform very well when compared to glass ionomers, provided they are not asked to perform more than they were designed or intended to do. So lets not continue to compare apples to oranges (glass ionomers to self adhesive cements or other applications), they are different, unless you are going to bring in the use of bonding agents.