In the opinion of many experts, glass ionomer restorative materials are among the greatest advances in dentistry since their debut around 50 years ago. These water-based materials are composed of a fluoro-alumino-silicate glass powder, and other elements such as calcium. When mixed with polyacrylic or polycarboxylate acid, the glass powder melts into a tooth-colored material capable of bonding to enamel and dentin.1Stone R. The glass menagerie. Mentor. 2017;8(2):35-39.
The Gift That Keeps on Giving
Exposed to saliva, glass ionomer materials leach fluoride ions into the surrounding structure, playing a major role in the protection and remineralization of dentition. Further, the fluoride in glass ionomers can be continually recharged via dentifrice or fluoride varnishes.
Due to the fluoride interchange and the cariostatic nature of glass ionomers, some experts regard glass ionomers as bioactive materials, although this is up for debate. According to newer definitions, in order for a material to be considered “bioactive,” it must precipitate apatite, which glass ionomers do not.2Stone R. The glass menagerie. Mentor. 2017;8(2):35-39.
Nonetheless, glass ionomers form a strong bond directly to tooth structure without needing adhesives to form a hybrid layer. They also feature the same coefficient of thermal expansion as natural dentition, help prevent microfractures that could lead to marginal leakage, don’t suffer from polymerization shrinkage, and are moisture tolerant. In fact, it is best to place them on moist tooth structure. 3Stone R. The glass menagerie. Mentor. 2017;8(2):35-39.
Even though glass ionomers are hydrophilic and, in fact, susceptible to dehydration, they are also water-soluble. In addition, they don’t wear well in the oral environment and have long cure times.4Stone R. The glass menagerie. Mentor. 2017;8(2):35-39.
To resolve some of these issues, resin was added to the glass ionomer mix. Resin-modified glass ionomers (RMGIs) became popular in the late 1980s and early 1990s. Among the added benefits offered by RMGIs are decreased water solubility, enhanced strength, decreased cure time, stronger bond formation, and better esthetics.
Glass ionomers and RMGIs excel as filling materials, luting cements, cavity liners and sealants. They are also commonly used for caries control in kids and older adults.5Stone R. The glass menagerie. Mentor. 2017;8(2):35-39.
Physical properties seem to be perpetually improving in many materials, including glass ionomers and RMGIs. Nanotechnology, for example, has contributed nano-sized filler particles to glass ionomers aimed at boosting strength, esthetics, fracture resistance, and other characteristics. Glass ionomers have also been modified to allow bulk filling and enhanced fluoride release. 6Stone R. The glass menagerie. Mentor. 2017;8(2):35-39.
Although glass ionomer-type materials are moisture tolerant — unlike resin materials — moisture control is still beneficial when placing these materials. Too much intraoral fluid and water may even result in contamination and dissolution.7Berg JH, Xu Z. Restorative dentistry in the primary dentition. Decisions in Dentistry. 2016;2(09):28–32.8 Lohbauer U. Dental glass ionomer cements as permanent filling materials? Properties, limitations and future trends. Materials. 2010;3:76–96.9 Ward DH. 20 Tops for Using Glass Ionomers. How to Use Dentistry’s Other Direct Tooth-Colored Material to Solve Restorative Problems. Available at: http://aacd.com/proxy/files/Students%20and%20Faculty/20%20tips%20Glass%20Ionomers.pdf. Accessed November 26, 2018.10 Sidhu S. Glass-ionomer cement restorative materials: a sticky subject? Aust Dent J. 2011;56:23–30.
But while RMGIs need protection from fluid contamination only during placement and light curing. Glass ionomers need protection throughout the setting phase.11 Ward DH. 20 Tops for Using Glass Ionomers. How to Use Dentistry’s Other Direct Tooth-Colored Material to Solve Restorative Problems. Available at: http://aacd.com/proxy/files/Students%20and%20Faculty/20%20tips%20Glass%20Ionomers.pdf. Accessed November 26, 2018.12 Sidhu S. Glass-ionomer cement restorative materials: a sticky subject? Aust Dent J. 2011;56:23–30.
While dental dams will suffice for this process, comprehensive systems such as the Isovac, Isodry and Isolite 3 provide isolation, evacuation and retraction for an unimpeded procedure. In addition, the Isolite 3 offers illumination that can be controlled with the press of a button so that it doesn’t interfere with light-sensitive materials. The flexible mouthpiece with integrated bite block enhances patient safety and comfort while fostering clinical accuracy and efficiency.
There is no question that continually evolving composite resins can outpace glass ionomers and RMGIs in many respects, and that bioactive formulations form an exciting category in dental materials. But most experts agree that glass ionomers and RMGIs will likely continue to remain vital players in the market for the foreseeable future.