We all know the feeling of a patient returning for a periodic checkup only to discover recurring decay beneath a once perfect restoration that we proudly placed not long ago. Often we don’t know what we’ll find under another dentist’s crown, and we’re worried it might look like nougat. We constantly manage the effects of CARS – resin and sealant associated caries – hoping that our dentinal bond will improve with the next restoration. However, the composite resin’s exceptional bond strength is offset by its lack of a chemistry-based defense against future acid attack. Studies of marginal leakage and personal experience show that cariogenic acids sneak under composite bonds and undermine what appeared to be a perfect restoration. For this reason, I have spent most of my career skeptical of composite resin.
In its place, I used and advocated glass ionomer, a calcium-fluoro-strontium glass with acid-neutralizing properties that make it much more effective in fighting recurrent caries.
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Recently, I documented my treatment of an extremely high caries risk patient with drug-induced xerostomia.1 The patient’s treatment involved a full mouth restoration with large buildups of glass ionomer core, supporting partial and full coverage CeraSmart and CeraSmart 270 restorations. The technique I used with this patient is one I developed over years of trial and error trying to bond my CEREC restorations to my favorite material, glass ionomer.
Composite resin and glass ionomer can coexist
During this trial and error, I discovered that the chemistry of composite resins and glass ionomer can co-exist preventively against cavities. The combination of immediate dentin sealing (IDS), glass ionomer and CeraSmart (hybrid force-absorbing ceramic) provides a complete, predictable, caries-resistant, one-visit restoration that can be adapted to a variety of clinical scenarios .
I can understand why many dentists are still skeptical of glass ionomer due to the failure of early versions of ASPA in the 1970s. It was not as esthetic as composite, despite providing a true chemical bond to dentin and enamel and having the same coefficient of thermal expansion as dentin. Glass ionomer was a material that could not compete with the myriad of layering and tinting techniques that composite offered to dental artists in my class. Even I would scratch my head and wonder why anyone would use an opaque material that dissolves.
Glass Ionomer Chemistry Improvements
Fortunately, significant improvements have been made in glass ionomer chemistry over the past three decades. Many dentists, however, do not keep it in their arsenal because they are still unaware of these developments. Over the past 10 years, improvements in glass ionomer have made it one of the simplest and most effective methods of fighting cavities in and around our restorations.
Glass ionomer, when applied to the tooth, fuses into a bioactive glass with a remarkable ability to sacrifice itself at the perfect moment. For a cavity to form completely, the tooth must reach a pH of 5.5 (the critical pH of hydroxyapatite), but the glass ionomer chemically dissolves at a pH just above 5.5, releasing ions that neutralize the acid attack before it can irreparably damage the tooth. The presence of glass ionomer assures me that my restoration can withstand a lack of brushing and flossing without catastrophic failure. Sometimes I see failures, but rarely do I seek recurring decay as deeply as before. Glass ionomer makes damage repairable, as the restoration is often easily repaired with bonding or glass ionomer.
Of course, glass ionomer isn’t perfect. At first, the main problem I had with this material was its inability to bond effectively with my favorite CEREC block, the hybrid ceramic resin that is CeraSmart. While I could get temporary bonds and was happy to see less recurring cavities, I had to find a better way to keep my onlays and crowns.
A mixed technique
Fortunately, developments in glass ionomer chemistry have coincided with significant improvements in bonding techniques. Recently, I was introduced to the IDS technique, the effectiveness of which made me rethink my skepticism towards composites. The IDS was the missing link for a restoration design that required structural durability as well as chemistry-based defense. With it, I realized I could get the best of all three materials, combining the anti-caries properties of glass ionomer, the superior bonding abilities of IDS, and the strength of a ceramic resin hybrid.
The result is what I consider to be an amalgamation of the co-curing technique, the sandwich technique and modern composite bonding. The advantages of combining these techniques are multiple. CEREC technology enables the creation of an indirect restoration directly in the practice in approximately 10 minutes; CeraSmart does not need to be baked and polishes the chair in minutes. My patients can watch the CEREC machine fabricate their computer-designed tooth, and I’m confident that the glass ionomer protects the tooth under my restoration and will slow future cariogenic attacks.
I have always been a “cariologist” at heart. I used to say, “If I can’t fix a tooth with glass ionomer, I’ll fix it with resin-modified glass ionomer.” And if I can’t fix it with resin-modified glass ionomer, I’ll lay hands on you and pray. I haven’t said that in quite a while with my newfound appreciation for what my composite-loving colleagues have been raving about for some time. I never thought I would use CEREC and never thought I would write about my use of composite bonding. But the combination of these technologies with glass ionomer has produced undeniably successful results in some patients at extreme risk of caries. I found peace of mind in my patient’s cavity-resistant, CEREC-restored mouth.
Editor’s note: This article originally appeared in the February 2022 edition of Dental economy.
Reference
- Novy BB, Kennedy EN, Donahoe J, Fournier S. Minimizing aerosols with nonsurgical approaches to caries management. J Mich Dent Assoc. 2020;102(7):48-56.
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