INTRODUCTION
Much has changed in restorative dental materials since the introduction of the 2 main types of aesthetic direct restorative materials: glass ionomers (GIs) and adhesive-based resin composites. Current composites offer excellent aesthetics, wear resistance, and strength; are significantly improved from earlier iterations; and can now be used for most direct restorations. GIs are now also available with improved physical and optical properties, truly complementing restorative dentistry with unique characteristics.

In discussing both product categories, the question often arises as to whether there is a real need for GI restoratives. Truth be told, and given the right clinical situation, usage of GI cements (GICs) can include the following everyday clinical issues:

• Class I nonocclusion-bearing restorations
• Sealants
• As bases under composites, often referred to as “the closed-sandwich technique”
• Liners
• Restorations in the primary dentition
• Management of rampant caries for high-caries risk patients
• Restorations for the management of root caries
• Challenging clinical situations due to isolation issues
• Reparative dentistry in the geriatric patient community
• Temporary restorations
• Core buildups for crowns
• Sealing access holes in implant screw-retained restorations.

The intent of this article is to present everyday clinical situations and how GIC can augment clinical outcomes.

Beneficial Characteristics and Clinical Solutions
GICs traditionally contain 2 basic components: polyacrylic acid and fluoroaluminosilicate glass particles. The polyacrylic acid is in aqueous solution, providing for good wettability; and these cements are hydrophilic, which is the reason why preparations should be mildly moist when GICs are applied. They are also moisture tolerant, one of their clinical benefits when compared with composites. This is especially useful when isolation and maintaining a dry field can be challenging (such as in young children, patients with limited openings, or in limited access situations like distal canted upper second molars).¹

Unlike direct resin composites that require the use of an adhesive system for micromechanical retention, which harden through light polymerization, GICs chemically adhere to tooth structure and set via an acid-based reaction (resin-modified GIs [RMGIs] are light polymerized). Therefore, GICs have decreased shrinkage, and the formed bond increases in strength after the initial setting phase.^2,3 After setting, the 3-dimensional network of GI cements incorporates the glass, much as fillers are incorporated into composite resins.

Fluoride release occurs on an ongoing basis from GICs and is one of benefits in helping to inhibit caries throughout time in the restoration.⁴ Does the fluoride run out? No. The beauty of GIs is that the fluoride replenishes and the GI acts like a long-term fluoride depot. In addition, the superior fluoride release from GIs inhibits demineralization and it has also been shown to have a positive effect on adjacent areas.^5,6 Everyday clinical situations where this is of benefit includes all patients at risk for new and recurring caries. This makes them especially useful for both children and the elderly (root caries) and patients of all ages with rampant caries.

CASE REPORTS
The 2 cases selections presented in this article relate to everyday clinical situations and optimizing long-term outcomes.

Case 1: Sandwich Restoration in a Maxillary First Molar
This case (Figures 1 to 8) involved a 43-year-old female patient who presented with an old amalgam on tooth No. 14 with poor margins and recurrent caries. The distal-occlusal lingual fissure was stained and recorded a reading of 1.3 using the CamX Spectra Caries Detection Aid (Air Techniques), which employs fluorescence technology. The 1.3 measurement supports the decision not to open the fissure since this indicates that there was no deeper demineralization beyond the outer enamel. After the failing amalgam and marginal recurrent caries were removed, the decision was made to restore the tooth using a closed-sandwich technique. The advantage of this approach is that a restorative material (GI) is placed that mimics dentin, is less technique sensitive than traditional bonding, has less shrinkage, and has fluoride release and less microleakage. The final outer component of the restoration is a low-shrinkage, low-stress composite that is then placed over the lost enamel component of the preparation.

CASE 1 Figure 1. The preparation was cleansed with a 2% chlorhexidine for 30 seconds followed by rinsing. With many glass ionomers (GIs), instructions are to condition for 10 to 20 seconds or etch with phosphoric acid for 5 seconds. (With GIs from VOCO, these steps are optional.) Figure 2. Placement of the GI (IonoStar Plus [VOCO]) into a mildly moist preparation. Figure 3. Condensing the GI after approximately 20 seconds. Figure 4. Removal of excess GI and final preparation. The goal is to leave approximately 2.0 mm for final composite placement. Figure 5. Beveling the enamel to enhance long-term bond strengths. Figure 6. The final preparation, after beveling with the GI as the dentin replacement. Figure 7. After total-etching, Futurabond U (VOCO) was placed over the entire preparation, air-dried, and light-cured. Figure 8. The final restoration with the all-ceramic outer layer (Admira Fusion [VOCO]).

The author, as a long-term user of GICs in this protocol, demonstrates in this case the use of IonoStar Plus (VOCO) as a bulk-fill, self-curing, high-fluoride-releasing GI. A unique characteristic of this GI is that alternating the trituration time allows the user to either place a more viscous material (10 seconds) or a firmer material (15 seconds) into the preparation. Iono­Star Plus has a unique glass component that contains calcium fluoride, aluminum oxide, silica dioxide, aluminum phosphate, and aluminum fluoride in addition to sodium aluminum fluoride. The capsule is designed for easy activation (by pressing down on the end prior to trituration) and to allow the tip to reach smaller preparations and difficult-to-access areas. One final unique component to the system is that, like with all VOCO GIs, conditioning is optional.

After cleansing the preparation for 60 seconds with a 2% chlorhexidine (Cavity Cleanser [BISCO Dental Products]), the preparation was rinsed, suctioned, and left mildly moist. The bulk-fill GI (IonoStar Plus) was triturated for 15 seconds (firmer placement) and inserted into the preparation. Within approximately 20 seconds, the viscosity of the material began to change, allowing a window of time to condense the nonsticky GI into place. (This GI has a total working time of 60 seconds and an additional 2 minutes of final setting time.) Once the setting had completed, excess GI material was removed via traditional diamond preparation and beveling of the enamel. Following total-etching, rinsing, and blot drying, a universal bonding adhesive (Futurabond U [VOCO]) was applied for 20 seconds, air-dried (5 seconds), then light-cured for 20 seconds before placing and curing an all-ceramic ORMOCER (VOCO) nanohybrid direct restorative material (Admira Fusion [VOCO]) as the outer layer of the restoration.

Case 2: Preventive Occlusal Restoration in a Mandibular First Molar
This case (Figures 9 to 13) involved a 17-year-old female. This new patient previously had 5 occlusal restorations placed along with one Class II restoration, and she reported having poor oral hygiene habits. Following her complete initial examination, it was determined that preventive restorations would be placed on the occlusal surfaces of 3 of her teeth. Spectra readings of 1.9 at the occlusal and 2.1 in the buccal pit were obtained for tooth No. 30, representing early D1 and E2 caries. A thorough review of her current oral hygiene situation was done, along with specific recommendations for proper home care.

At the next appointment, her oral hygiene had improved dramatically with simple adjustments to her daily habits, including the introduction and use of Oral-B’s power toothbrush.

CASE 2 Figure 9. Preoperative view. Figures 10 and 11. Assessment of occlusal and buccal surfaces of tooth No. 30 using the CamX Spectra Caries Detection Aid (Air Techniques). Figure 12. Placement of a regular setting GI (IonoStar Molar [VOCO]). Figure 13. A thin layer of Easy Glaze (VOCO) is placed after final adjustment.

Minimally invasive preparations of the occlusal surface and buccal pit in tooth No. 30 were achieved without local anesthetic using an Er:YAG laser (Lite Touch [AMD LASERS]) (2.6 W, 200 mJ, 13 Hz, water setting at 5). The occlusal preparation was just under 2.0 mm at its deepest point, which confirmed the CamX Spectra reading. In this case, Iono­Star Molar (VOCO) was used. IonoStar Molar is another GI (introduced before the release of IonoStar Plus) that has a longer working time and setting time. The additional working time is beneficial if multiple restorations are restored simultaneously. A thin layer of Easy Glaze (VOCO) was placed after final adjustment and immediately light-cured. The buccal pit was restored (Admira Fusion; shade A1) using a total-etch/universal bond technique.

CLOSING COMMENTS
GIs offer distinct clinical benefits, including fluoride release and recharging of fluoride, the potential for dentin remineralization within preparations, moisture tolerance, and chemical self-adhesion. The characteristics of GICs lend to their selection in everyday clinical situations in which caries control, isolation, and maintaining a dry field are challenging, along with the many indications for usage maximizing their fluoride release and additional unique properties.

References

1. Berg JH, Croll TP. Glass ionomer restorative cement systems: an update. Pediatr Dent. 2015;37:116-124.
2. Sidhu SK, Nicholson JW. A review of glass-ionomer cements for clinical dentistry. J Funct Biomater. 2016;7(3).
3. Arrondo JL, Collado MI, Soler I, et al. Setting reaction of polyacid modified composite resins or compomers. Open Dent J. 2009;3:197-201.
4. Billington RW, Williams JA, Pearson GJ. Ion processes in glass ionomer cements. J Dent. 2006;34:544-555.
5. Qvist V, Poulsen A, Teglers PT, et al. Fluorides leaching from restorative materials and the effect on adjacent teeth. Int Dent J. 2010;60:156-160.
6. Tantbirojn D, Rusin RP, Bui HT, et al. Inhibition of dentin demineralization adjacent to a glass-ionomer/composite sandwich restoration. Quintessence Int. 2009;40:287-294.

Dr. Graham, a graduate of Emory University Dental School (Atlanta, Ga), is a member of the ADA, American Association of Cosmetic Dentistry, AGD, Chicago Dental Society, and Illinois Dental Association. He maintains a private practice, University Dental Professionals, in Chicago. He is the former dental director of the University of Chicago’s Department of Dentistry. The founder of Catapult Education, he is an internationally recognized lecturer involved in continuing education focusing on incorporating current clinical advancements through “conservative dentistry.” He emphasizes dental health diagnosis, treatment plans for medically com­promised patients, conservative treatment, cosmetic dentistry, and customized approaches to periodontal care, implants, and laser dentistry. He has been published in many leading international dental journals. He can be reached at (773) 684-5702 or via email at lgrahamdds@aol.com.

Disclosure Dr. Graham reports no disclosures.

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