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Through the looking glass (ionomer)

March 1, 2020
Dr. Erinne Kennedy says many of the early glass ionomers were not reinforced with resin as they are today, which has changed the game for this restorative material. She debunks four myths.

My first three to five years out of dental school have felt like a constant fire hydrant of information. While dental education is improving and constantly changing, it’s nearly impossible to keep up with the flood of research and innovation in the field. My biggest challenge is allowing my mindset to shift. I often feel as if I can hear the voices of various professors inside my head while I am planning, executing, and evaluating the care I provide. Sometimes these voices are spot on, but other times I have to allow these voices to change because evidence-based dentistry, the profession itself, and my skills are constantly evolving. What this means is that the things your professor learned 50 years ago and taught you five years ago might not apply to your clinical practice today. For many, this is unsettling. For me, it feels like a new challenge. 

One of the mindset shifts that I have encountered in the last three years is the use of glass ionomer (GI) as a direct restorative material. In dental school, I had professors who shared a few ideas on the subject with me that have since become myths. Products change, procedures evolve, and new science is added to the literature daily. Because of this, we have to bust the myths that we once thought were true. 

Myth no. 1: ‘Glass ionomer isn’t strong enough.’ 

One of the myths that I learned in dental school was that GI was not a strong material. Perhaps some of my professors had only experienced its earliest forms. Many of the early GIs were not reinforced with resin as they are today, which has changed the game for this restorative material. The strength of dental materials can be described by measures such as proportional limit, elastic limit, yield strength, and as ultimate tensile, shear, compressive, and flexural strength.

One of the GI materials that I use frequently in my practice is Equia Forte (GC America). I use this material for sealants and class I, II, and V restorations because GI has a compressive strength of 219 MPa and a flexural strength of 46. Well-known and researched restorative materials, such as amalgam restorations, have been shown to have an average compressive strength of approximately 185 MPa, demonstrating that Equia Forte has a greater compressive strength than the average amalgam restorations. Similarly, one study demonstrated a mean flexural strength of amalgam to be about 28 MPa.1 As you can see, Equia Forte is a great example of a GI that has similar strength properties to the long-standing dental material, amalgam.

Myth no. 2: ‘Glass ionomer doesn’t release enough fluoride to make a clinical difference.’ 

Many practitioners question whether or not the release of fluoride ions from GIs has a clinically significant impact for their patients. Cagetti et al. reported that the fluoride release from GI sealants on second primary molars demonstrated a statistically significant reduction in the incidence of caries on the distal surface of second primary molars.2 For high-risk children and adults in my practice, I place GI sealants when grooves are deep and particularly susceptible to caries not only to prevent occlusal caries but, in some cases, prevent interproximal caries as well. In fact, in adults with multiple ICDAS (International Caries Detection and Assessment System) 1 and 2 lesions, I place occlusal sealants in addition to the application of silver diamine fluoride to help prevent and remineralize the interproximal lesions. I use a minimally invasive technique using an air/water abrasion unit to remove any demineralized tooth structure prior to sealant placement. In the future, I see payers reimbursing for sealants on patients of all ages, as well as for replacement of lost sealants. Sealants reduce occlusal caries risk and incidence, an evidence-based procedure that will surely create value in a dental care delivery system that incentivizes value-based care. 

Myth no. 3: ‘Glass ionomer isn’t esthetic.’ 

During the early years of GI and GI cements, the products used were opaque and often white. Riley et al. conducted a study of patients receiving care for defective restorations and highlighted that patient satisfaction most frequently comes from the personal interaction with the dentist, level of comfort, and posttreatment sensitivity.3 Research shows that GI cements have immediate reduced postoperative sensitivity compared to adhesive bonding systems associated with composite restorations. Companies have created entire lines of resin-modified glass ionomer (RMGI) that have many of the same shade selections as a composite system.4 

Myth no. 4: ‘Glass ionomer is hard to handle.’ 

As I mentioned, the first few years out of dental school have been a real whirlwind. You are acquiring new skills and techniques, all while learning to do the same things you already do more efficiently. If you are new to using GI, here are a few tips to help you achieve consistent results: 

• Use a sectional matrix system with a wedge to ensure your contact is adequate. 

• Burnish with a smooth, straight instrument to achieve a broad contact. 

• As you place the restorative material in the deepest part of your restoration first (i.e., the proximal box), you will watch the material chase the water to the surface, which will be removed with contouring. 

• When contouring, impregnate a microbrush with the coating agent and liberally coat the occlusal surface of the restoration. Contour with a coated composite instrument.

• Instead of plugging, press the material and smooth into the margins of the prep. Plugging the material can pull the material up and away from the deepest part of the preparation.

• Let the material mature. It will harden after three to five minutes and be ready to contour. 

• For interproximal contouring, use a posterior scaler. 

• After adjusting and polishing with copious water, briefly (less than three seconds) etch the restoration and seal with either a coating agent or PermaSeal (Ultradent) for a wear-resistant surface. 

I hope you find these resources and tips useful in your practice. And most importantly, I hope that you continue to allow your mindset to shift as the evidence in dentistry shifts.  


1. Jayanthi N, Vinod V. Comparative evaluation of compressive strength and flexural strength of conventional core materials with nanohybrid composite resin core material an in vitro study. J Indian Prosthodont Soc. 2013;13(3):281-289. doi:10.1007/s13191-012-0236-4

2. Cagetti MG, Carta G, Cocco F, et al. Effect of fluoridated sealants on adjacent tooth surfaces: A 30-mo randomized clinical trial. J Dent Res. 2014;93(suppl 7):59S-65S. doi:10.1177/0022034514535808 

3. Riley JL 3rd, Gordan VV, Rindal DB, et al. Components of patient satisfaction with a dental restorative visit: Results from the Dental Practice-Based Research Network. J Am Dent Assoc. 2012;143(9):1002-1010. doi:10.14219/jada.archive.2012.0329

4. Akpata ES, Sadiq W. Post-operative sensitivity in glass-ionomer versus adhesive resin-lined posterior composites. Am J Dent. 2001;14(1):34-38.

Erinne Kennedy, DMD, MPH, MMSc, graduated from Nova Southeastern College of Dental Medicine in 2015. She received her medical master of science in dental education from the Harvard School of Dental Medicine and is a board-certified dental public health specialist who practices clinical dentistry at the Alliance Dental Center, LLC, in Quincy, Massachusetts. Contact her at [email protected].

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