5 misconceptions about glass ionomers

Feb. 17, 2011
Although glass ionomers have been readily available as a restorative material for many years, some misconceptions still exist. This article answers some lingering questions about when, why, and how to easily and efficiently use glass ionomers in everyday practice.

Information provided by 3M ESPE

Although glass ionomers (GIs) have been readily available as a restorative material for many years, some misconceptions about the product still exist. The following information should answer some lingering questions about when, why, and how to easily and efficiently use GIs in your everyday practice.

Misconception No. 1: If you’ve seen one glass ionomer, you’ve seen them all.

The facts: Fluoride-releasing materials have been available as a restorative material for more than 40 years, and many dental professionals are under the impression that little has changed in their formulation. In actuality, there are now three different formulations available: traditional or conventional self-cured GIs, resin-modified GIs (RMGIs), and compomers.

With a traditional GI, you will observe a self-cured, acid-base setting reaction, chemical bonding to both enamel and dentin, the release of fluoride, biocompatibility, and acceptable esthetics. The main reason that GIs are advantageous over other restorative materials is their potential to have a cariostatic effect due to the release of fluoride (spurred by an acid-base reaction) and their antibacterial qualities.

RMGIs are characterized by the addition of polymerizable resin groups to the traditional formulation, which allows the material to be light cured while still maintaining acid reactivity.

Compomers are essentially a combination of the properties present in both a GI and composite. Like RMGIs, compomers are resin-based, but unlike a true GI, they do not contain water and do not achieve an acid-base reaction until water is drawn into the oral cavity. Levels of fluoride diffused from compomers are significantly lower than those produced by GIs and RMGIs, but mechanical properties tend to be stronger.

Misconception No. 2: Glass ionomers are not esthetic and have no place in everyday dentistry.

The facts: Traditional GIs are considered to have low erosion resistance. However, more recent formulations of GIs offer improvements in both esthetics and wear. For example, after polymerization, the resins in RMGIs provide strength and protect the acid-base reaction from becoming contaminated by dehydration or water absorption. RMGIs also improve upon the traditional GI formulation by offering better shade selection and increased polishability, especially in the case of Ketac™ Nano Light-Curing Glass Ionomer Restorative by 3M ESPE, an RMGI that offers nanotechnology. An exclusive science used by 3M ESPE, nanotechnology allows for higher esthetic and greater wear properties than other materials.

Further, advancements in delivery systems have made it possible to use a GI without having to spend time hand-mixing or triturating. For example, Ketac Nano was recently made available in the Quick Mix Capsule. It contains exact doses of the two pastes, which are mixed directly in the applicator tip. A benefit of this kind of delivery system is minimizing voids during placing.

Misconception No. 3: If it doesn’t self-cure, it’s not a GI.

The facts: Most traditional GIs are indeed self-curing, but this is not true of RMGIs, nor is it a necessary characteristic for a restorative to be considered a GI. In fact, as noted above, it is the photopolymerization of RMGIs that gives the material the ability to withstand water uptake and retain strength. To obtain their highest mechanical properties, all RMGIs must be light cured.

Misconception No. 4: Applying a primer before using a GI prevents fluoride release and uptake.

The facts: When using all types of GIs and RMGIs, a “primer” solution containing polyacrylic acid must be applied to the cavity surface to remove or modify the smear layer and increase wettability. The primer solution is not as acidic as phosphoric acid.

The application of a primer does not affect either the GI’s ability to release fluoride or the tooth’s ability to absorb it. In some cases, the primer can actually serve to enhance the release of fluoride ions from the restorative material.

Misconception No. 5: GI restoratives are only useful in pediatric or geriatric cases.

The facts: The properties of traditional GIs lent themselves mainly for use as a cement or liner/base. However, the improved range of characteristics present in more modern GI restoratives makes them a viable option for everyday dentistry. GIs and RMGIs can be successfully used for restoring primary teeth, small Class I restorations, and Class III or V restorations. The list of clinical indications for GIs and RMGIs has been significantly widened to include:

  • Core buildups
  • Tunnel restorations
  • Sandwich restoration — open and closed technique
  • Retrograde filling material
  • Pit-and-fissure sealants
  • Root caries or cervical restorations
  • Temporary or A.R.T. restorations
  • Endodontic sealer

Because of the high diffusion of fluoride imparted by both traditional GIs and RMGIs, pediatric and geriatric patients do continue to benefit greatly from these materials. However, with the widening list of indications and improvements in both strength and esthetics, GI restoratives should become an important part of every dental practice.