by Robert G. Ritter, DMD
One of the most researched and applied areas of dentistry during the past 30 years has been the introduction of adhesives. Beginning with the earliest first- generation products, the goal of adhesive dentistry has been to preserve as much natural tooth structure as possible, reinforce the existing tooth structure, and make the tooth look like no dentistry has been performed. As time and developments move forward, dental manufacturers continue to make the process of adhesively bonding materials to tooth structure easier. However, easier is sometimes not better.
This is where factors such as ease of placement, delivery systems, multiple components, and the composition of materials are important. A long-term bond is the ultimate goal, and as the pursuit of that goal continues, the rules of adhesive dentistry are changing in the marketplace. What was once a small chemistry-set approach to materials has now become a unit dose of all-in-one products which can theoretically do everything we want them to do. At least, that’s what dental manufacturers want us to believe. Adhesive dentistry allows us to place composite resins and all-ceramic units, such as veneers, onlays, and crowns, anywhere in the mouth. A quick review of adhesive systems is a good idea. It will then lead us to where we are today and what the future holds in this very exciting area of restorative dentistry.
To simplify this process, let’s skip to the fourth generation of dentin adhesives - total etch. Most would consider products such as ALL-BOND 2 (BISCO), OptiBond FL (Kerr), and Adper™ Scotchbond™ Multi-purpose (3M™ ESPE™) as the gold standard in this category. They have the longest track record as far as research goes and they perform extremely well clinically. In fact, OptiBond, an 18-year-old product, just received the “Product of the Year” award from Reality magazine. What does this say about the use of a fourth-generation product? It would be hard to discourage use of these classes of products. If there is a downside, it would be the multiple steps required to place these materials, and they could be technique-sensitive in the hands of inexperienced adhesive clinicians, which could lead to the most distressing of problems, post-operative sensitivity. Another problem with these systems was their inability to bond to dual-curing composite core materials and luting agents. This was eventually changed with the addition of a dual-cure additive.
The introduction of fifth-generation adhesives roughly nine years ago was a simplification of the process by combining the primers and adhesives into a single dose and making them available in unit dosing to provide fresh chemistry on each procedure. Products in this category are Excite (Ivoclar Vivadent), Prime & Bond® NT™ (DENTSPLY), Adper™ Singlebond™ (3M™ ESPE™), and OptiBond® Solo Plus™ (Kerr). Fewer steps are an improvement; however, careful placement and evaporation of the carrier solvents is critical when using this class of materials.
The sixth-generation class of adhesives was a real forward jump in thinking. The arrival of what we now call “self-etching primers” was a dramatic leap forward in technology. These systems are typically two-bottle systems. Some products in this class are CLEARFIL SE BOND (Kuraray), Simplicity (Apex), and Adper™ Prompt™ L-Pop™ (3M™ ESPE™). These categories of adhesives require no rinsing, so the amount of moisture on the tooth is not critical. The downside to these products is they generally do not work as well on uncut enamel, which makes them more problematic when it comes to microleakage, especially in critical cosmetic areas such as anterior composite restorations. This is dependent on the pH of the product, which varies greatly from manufacturer to manufacturer. We now have long-term research on these products which show great retention rates, little microleakage, and literally no postoperative sensitivity
The latest category - the seventh generation - is the all-in-one adhesives that combine the etch, prime, and bond in a solution. Some innovative delivery systems have made these products easier to use. Again, these adhesives are no-rinse products, meaning no water is used to remove materials.
Some of the products in this category are iBond (Heraeus), Xeno® IV (DENTSPLY), G-BOND™ (GC), OptiBond® All-in-One (Kerr), Complete™ (Cosmedent®), and AdheSE One (Ivoclar Vivadent). New research comparing the bond strength of the sixth- and seventh-generation adhesives show similar results. The biggest benefit of these categories is little, if any, postoperative sensitivity reported.
The most popular self-etching material, CLEARFIL SE BOND (Kuraray), has been on the market for 10 years. Self-etching has caught on, and a large group of dentists use these products as their primary adhesive. At the same time, there is a major swing going back to the fourth generation of adhesives because long-term success has been proven.
So, what does a clinician choose with so many choices available? The answer is not quite as obvious. The first question to answer is do you use a rubber dam? It is in everyone’s best interest to use this 100-year-old technology; however, if you are not using it, a good choice to avoid postop sensitivity is a self-etching primer. It is more forgiving, especially in the posterior area of the mouth. If you are doing a lot of direct composites in the anterior, you might want to first pre-etch with phosphoric acid, rinse it off, and then cut your preparation before using the self-etching primer or just apply the primer 15 seconds longer to the enamel before applying it to the dentin. If you are currently using fourth-generation materials with success, don’t change. In fact, if something is working for you, do not change your system for the very reason that you have mastered it.
Dental manufacturers continue to develop new adhesives and delivery systems to streamline the adhesive process. The next paradigm shift will be the introduction of self-adhesive composites where the adhesives are already in the composite restorative materials. We probably are a few years away from such technologies due to the extremely difficult chemistry involved. For now, we have self-adhesive resin cements. They work well - in fact, there have been few reported failures due to debonding or postoperative sensitivity. What we need now are long-term studies similar to those we have with adhesives ... studies that prove their lack of microleakage and their effectiveness.Today, we have more than 100 dental-adhesive systems available - from total-etch and self-etching primers to all-in-one products. I believe technique is more important than the product selected. Use of a rubber dam and following the manufacturers’ instructions are critical for success. Proper application, removal of solvent carriers, and an adequate amount of light-curing all play a vital role in using adhesives for restorative procedures. Without the use of adhesives, we could not produce some of the more esthetic, conservative restorations that patients want. The future of adhesives is bright, with many exciting possibilities on the horizon that will make the practice of dentistry more enjoyable and predictable for years to come.
Robert G. Ritter, DMD, has a full-time practice focusing on adhesive esthetic dentistry in Jupiter, Fla. He received his dental degree from The Medical University of South Carolina College of Dental Medicine in 1994. Dr. Ritter is an editorial board member of REALITY. He is the president of the Florida Academy of Cosmetic Dentistry. He also is a member of the Academy of Cosmetic Dentistry. Contact Dr. Ritter by e-mail at [email protected].