Understanding Today's Materials

Joyce Bassett, DDS (JB): When I am ready to buy a new bonding agent, I will look to the newer-generation product lines because they have more advanced chemistry. Different ingredients are being added to make outcomes more predictable. Many of today's universal bonding agents include the 10-methacryloyloxydecyl dihydrogen phosphate (MDP) molecule, which improves the chemical bond. Some contain matrix metalloproteinase (MMP) inhibitors. Because scientists continue to learn about the bonding process and the factors that can degrade the hybrid layer and make bonding agents less effective over time, the newer bonding agents have ingredients and chemistries to counter those factors. For me, it is important to look closely at the ingredients and consider what makes a bond more durable and predictable. In addition, it is important to read the instructions and understand the predictability of a bonding agent and the time limitations. For example, it may be necessary to scrub for 10 or 20 seconds. I keep a timer in my operatory and refer to it frequently. Dentists need to know the indications of these materials, including which ones need to be light cured and which ones will self cure. Newer universal bonding agents also exhibit less film thickness, so they can be air-dried and light cured-then they are finished.

ID: Are bioactive materials merely en vogue, or will they become the standard in future iterations of restorative materials?

JB: Bioactive is a great buzzword. The problem is that it is not very well-defined. One definition entails the release of ions into the tooth structure, whereas others involve remineralization of the tooth structure. I do believe that we need to consider that some bioactive materials may not be as beneficial long-term in clinical practice. We need to be careful about how and where we are using these materials because some of them are failing. If the case involves a large preparation design, perhaps a bioactive material should be used only as a liner. How high-risk is the patient? If decay is everywhere, then a bioactive material is a very good option. In order to avoid compromising the clinical outcome, it is necessary to fully understand the indications of bioactive materials.

ID: Amalgam separators are going to be mandatory in all US practices by 2020. Does amalgam still have a place in the armamentarium?

JB: That regulation is important to protect the environment because we sometimes need to remove amalgam from patients' mouths; however, most dentists do not even use amalgam now. Amalgam still has a place in practices where there are significant financial and time constraints because it is cheap and quick. We know it will work short-term, but it can be problematic long-term because the mercury inside the amalgam expands and contracts over time, which can often cause cusp tips to break. Ideally, bonding composites is a better solution for direct restorations.

ID: In your experience as a lecturer and an educator, what is the one key aspect that most practitioners fail to consider with direct restorative procedures that might account for failures?

JB: There is not one predominant thing that goes wrong with direct composite resins in the mouth-there are many. If a dentist is working on an isolated tooth, he or she needs to ensure that no saliva is getting in there and that the area is kept clean. Dentists need to look at how large a direct restoration is; should it have an indirect restoration placed on it? I am not afraid to tell a patient that I thought I could get away with a direct composite restoration but realized that he or she really needs something more definitive on top of that foundation, such as a crown or an onlay. It is important for a patient to understand that. Dentists also need to ensure that they are using the correct material for the indication. For example, for a bulk-fill restoration in the posterior region, a composite must be selected with appropriately sized filler particles. Dentists need to stay at 4-mm increments, and when they polymerize the material, they need to use the right curing light and put the light tip in the right place. They also need to look at the occlusion and the bite because issues with these can ruin a restoration as well. Finally, if they are doing mesial-occlusal-distal (MOD) composites, they need to know how to use matrix bands in order to achieve good contacts.

Joyce Bassett, DDS
Fellow
American Academy of Cosmetic Dentistry

Clinical Instructor
Kois Center
Seattle, Washington