Oral Health Group
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The Evolution of Glass Ionomer Restorative Materials

December 2, 2016
by Daniel H. Ward, DDS


Glass ionomers have enjoyed many firsts in dentistry. They were the first materials designed to resist recurrent decay. They were the first bioactive materials, which release fluoride in an acidic environment and recharge or replace lost fluoride ions when they are re-introduced back into the oral environment. They were the first easy to use bulk-fill material. There have been many improvements to the original formulas, which now have improved handling, strength, wear rates and esthetics. In addition, there are many new applications for glass ionomers, which are approaching their 50th year of existence.

History Of Glass Ionomers
Dr. Alan Wilson and Dr. Brian Kent at the British Laboratory of the Government Chemist, who were experimenting with mixing silicate glass with poly-acrylic acid, first synthesized Glass ionomers in 1965. They established that the setting mechanism was an acid/base reaction. In 1975 the first commercially available glass ionomer was produced. Dr. John McLean was the first to develop clinical techniques and to demonstrate the material’s resistance to caries. Over the years, improvements were made to the original formulations, to speed up the set and to allow immediate shaping. A small loyal group of dentists successfully used the materials but their growth was overshadowed by the development of improved dentin bonding agents and composite resins.

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In the past 10 years, there has been a resurgence of interest in glass ionomer materials. Many companies have added glass ionomers to their restorative lines. With declined use of metal direct restorative materials, dentists have been looking for the ability to use tooth colored materials in all procedures. Composite resins have their limitations and alternative materials were needed to complete the transition. Glass ionomers are the perfect complement to other esthetic restorative materials and allow dentists who wish to eliminate direct metallic restorations from their practices, to successfully do so.

Advantages Of Glass Ionomers
Glass ionomer direct restorative materials are simpler to place in bulk and have reduced operator caused post-operative sensitivity than composite restorations. 1,2 The set material has a coefficient of thermal expansion which is similar to tooth structure. 3 Glass ionomers are antibacterial. 4 They are not as sensitive to variations in the moisture in the restorative area during placement as composite resins, and have a long-term stable bond to dentin which generally does not diminish over time. 5 Resin bonding to dentin has been shown to gradually diminish in time due to MMPs, hydrolyzation, polymerization shrinkage and other factors. 6,7,8 The biggest advantage of glass ionomers is their ability to release fluoride during an acidic attack and to uptake fluoride ions when present in the oral environment. 9

Class V Glass Ionomer Restoration Placement
Glass ionomer restorative materials were initially indicated to restore Class V dentin lesions. Decay around areas of gingival recession can be problematic for older people who suffer from xerostomia as a result of all the medications they are taking. It has been reported that medications are the most common cause of decreased salivary function and that 80% of the most commonly prescribed drugs cause xerostomia. 10

An older patient presented with a Class V lesion around the cervical of a left maxillary first premolar. The canine had been extracted due to decay, an implant placed and was covered until osseous integration was complete. It was decided that a glass ionomer restoration would be ideal for this high caries risk patient with cervical decay, who will be having an implant restoration placed. Implants often have open gingival areas due to papilla loss, which accumulate food and plaque more easily, making them more susceptible to recurrent decay.

The patient was anesthetized and retraction cord (Dux Dental Gingibraid 1E) was placed to retract and protect the gingival tissue during preparation (Fig. 1). A 330 bur in a high-speed handpiece with copious water spray was used to initially shape and outline the preparation. A #2 round bur was used in a slow speed handpiece to finish the excavation and insure that all the decay was removed. The completed restoration was thoroughly washed and evaluated (Fig. 2).

Fig. 1
ward-figure-1-placing-cord

Fig. 2
ward-figure-2-completed-preparation

The restoration was treated with polyacrylic acid (GC Cavity Conditioner) for 10 seconds and thoroughly washed and lightly blown with air to leave a moist but not wet surface (Fig. 3). Treating with this conditioner enhances the bond strength between the restoration and the tooth. A pre-encapsulated glass ionomer (GC Fuji IX GP Extra) was selected. It was first tapped on the counter several times to loosen the powder. Then it was placed into the dispenser and squeezed once, to ensure that plunger was in all the way, and activated. The capsule was triturated for 10 seconds. Pre-encapsulated glass ionomers give predictable results, are easier to use and give consistent set times.

Fig. 3
ward-figure-3-treatment-of-dentin-with-polyacrylic-acid

The mixed glass ionomer was placed in an applicator and dispensed into the restoration (GC Capsule Applier III). A composite placement instrument was used to push the material outward to make sure the margins were sealed. The area was isolated, kept dry and allowed to harden for two and a half minutes (Figs. 4, 5). A very fine diamond bur with copious water spray was used to shape the hardened glass ionomer while a worn and scratched up composite placement instrument was used to hold the gingiva out of the way (Premier 201.3VF) (Fig. 6). The cord was removed and the restoration and tooth were blended together.

Fig. 4
ward-figure-4-mixing-pre-encapsulated-glass-ionomer

Fig. 5
ward-figure-5-bulk-placement-of-glass-ionomer

Fig. 6
ward-figure-6-holding-tissue-back-and-shaping-with-fine-diamond-bur

The shaped restoration was washed and thoroughly dried and a surface sealant was placed over the entire un-etched restoration with a brush (GC G Coat Plus) (Fig. 7). Etchant should not be placed over the set material prior to adding a surface sealant. The area was light cured for 20 seconds (Fig. 8). The completed restoration was evaluated and shown to the patient (Fig. 9).

Fig. 7
ward-figure-7-placing-resin-coating-over-dried-restoration

Fig. 8
ward-figure-8-light-curing-resin-sealant

Fig. 9
ward-figure-9-completed-class-v-glass-ionomer-restoration

Class Ii Glass Ionomer Restoration
A patient was being seen in our office for the replacement of a leaking, faulty amalgam restoration. The patient was anesthetized and the old restoration was removed. The decay was excavated and was visibly near the pulp. The decay undermined several cusps (Fig. 10). Post-operative sensitivity and polymerization shrinkage stress were of concern so glass ionomer was chosen to be the restorative material. There was concern for a pulpitis and perhaps later a fractured cusp. The tooth likely will need to be crowned at a later date.

Fig. 10
ward-figure-10-expansive-preparation

Sectional matrices were placed on the mesial and distal (Triodent V-3 sectional matrix system) (Fig. 11). The desired contact areas were burnished against the adjacent teeth. The tooth was treated with a glass ionomer dentin conditioner (GC Fuji IX GP Extra) for 10 seconds and thoroughly washed. Air was lightly blown on the dentin to remove pooled water but the dentin was left moist. An encapsulated glass ionomer was mixed and dispensed into the tooth (EQUIA-GC America). A gloved thumb was pushed against the material for two and a half minutes to ensure no voids. The matrices and retainers were removed. A very-fine football shaped diamond (Premier 285.5VF diamond) with copious water spray was used to shape the occlusal surface and a very-fine diamond tipped bur was used to shape the interproximal areas. The occlusion was adjusted and contacts checked with floss. Metal bands were placed back down into the interproximal areas. The restoration was thoroughly washed and dried; a surface sealant placed and light cured (GC EQUIA Coat Plus) (Fig. 12). Several hundred similar restorations have been placed in my office over the past 10 years and have been successful.

Fig. 11
ward-figure-11-restoration-placed-using-sectional-matrices

Fig. 12
ward-figure-12-finished-glass-ionomer-restoration

New Improved High Strength Glass Ionomer Posterior Restorative Materials
Recently new improved high viscosity glass ionomer materials have been introduced that are designed to be used in the posterior area (GC EQUIA Forte) (Fig. 13). Strength has been increased and wear rates reduced. The largest reason for composite resin failure is recurrent decay. Even though glass ionomers are not as strong as composite resins, their overall longevity may be superior to composite restorations in many instances. High caries rate individuals will have poor success with composite restorations. Glass ionomer restorations may last longer than composite restorations with young people consuming large amounts of sugar, drug abusers, xerostomia patients, older persons with recession, and patients with poor oral hygiene. The benefits of glass ionomers often outweigh their disadvantages.

Fig. 13
ward-figure-13-equia-forte

Multiple Class Ii Glass Ionomer Restorations
A patient who has been coming to the office for 30 years reported for her periodic exam and prophylaxis. Digital bitewing radiographs were taken and unusually high areas of new interproximal decay were noted (Dexis-Platinum) (Fig. 14). No operative treatment had been performed in over eight years even though she had been examined on a regular basis. There had been a significant change in her medications.

Initial excavations were started on the first molar and second premolar to determine the extent of the decay (Fig. 15). The first premolar and canine were prepared and the first molar restored with a high-strength glass ionomer restorative material (GC-EQUIA Forte) (Fig. 16). It was felt that a 50-year-old patient, who had no restorations for years, and then needed 16 restorations, required a bioactive material that releases fluoride. Sectional matrices were used (Triodent V-3 sectional matrix system) and all the posterior teeth were restored using the high-strength glass ionomer. The canine was restored using composite resin. The restorations were shaped and sealed (Fig. 17). The remaining areas in the mouth were restored in a similar manner at subsequent appointments.

Fig. 14
ward-figure-14-pre-operative-radiograph

Fig. 15
ward-figure-15-first-molar-and-second-premolar-excavated

Fig. 16
ward-figure-16-first-molar-restored-with-glass-ionomer

Fig. 17
ward-figure-17-completed-glass-ionomer-restorations

Summary
Glass ionomer direct restorative materials along with composite resin materials enable dentists to restore teeth without metal. The glass ionomer’s ability to resist recurrent decay, the largest cause of direct composite failure, is very important. When looking at the complete picture, strength of a material is not always the best gauge of its longevity. With its ease of use, excellent retention, reduced post-operative sensitivity, and anti-cariogenic properties, glass ionomers usage should continue to increase. Glass ionomers should be a part of every dentist’s restorative armamentarium. OH

Oral Health welcomes this original article.

References
1. Opdam NJ, Feilzer AJ, Roeters JJ, Smale I. Class I occlusal composite resin restorations:in vivo post-operative sensitivity, wall adaptation, and microleakage. Am J Dent. 1998;11(5):229-234.
2. Akpata ES, Sadiq W. Post-operative sensitivity in glass-ionomer versus adhesive resin-line posterior composites. Am J Dent. 2001;14:34-38.
3. Browning WD. The benefits of glass ionomer self-adhesive materials in restorative dentistry. Compend Contin Educ Dent. 2006;27::308-314.
4. Menon T, Kumar CP, Dinesh K. Antibacterial activity of glass-ionomer restorative cements and polyacid modified composite resin against cariogenic bacteria. Indian J Med Microbiol. 2006;24:150-151.
5. Albers HA. Tooth-Colored Restoratives: Principles and Techniques 9th ed. Hamilton, Ont:BC Decker Inc. 2002:43-55.
6. Pashley DH, Tay FR, Yiu C, Hashimoto M, Breschi L, Carvalho RM, Ito S. Collagen degradation by host-derived enzymes during aging. J Dent Res. 2004;83:216–221.
7. Hashimoto M, Ohno H, Sano H, et al. Micromorphological changes in resin-dentin bonds after 1 year of water storage. J Biomed Mater Res. 2002;63(3):306-311.
8. Giachetti L, Russo DS, Bambi C, Nieri M, Bertini F. Influence of operator skill on microleakege of total-etch and self-etch bonding systems. J Dent. 2008;36(1):49–53.
9. Dejan Lj Markovic, Bojan B Petrovic, and Tamara O Peric. Fluoride content and recharge ability of five glass ionomer dental materials. BMC Oral Health. 2008;8-21.
10. Gupta A, Epstein JB, Sroussi H. Hyposalivation in Elderly Patients. J Can Dent Assoc 2006; 72(9):841–6.


About the Author
Dr. Ward is in private practice in Columbus, Ohio. He is a Diplomate of the American Board of Aesthetic Dentistry, a Fellow of the American Society for Dental Aesthetics and a Fellow in the International College of Dentists. He serves as a reviewer for the Journal of Prosthetic Dentistry and the Journal of Esthetic and Restorative Dentistry. He has lectured internationally and authored pioneering articles in the field of proportional smile design. Email: dward@columbus.rr.com.


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