Methods. A total of 306 patients who had received a total of 864 resin-modified glass ionomer restorations, which had been in their mouths for a minimum of three years, were included in this evaluation. The authors assessed the clinical observations recorded in patients’ records and used bitewing radiographs to assess Class II restorations.

Results. The authors found an overall restoration success rate of 93.0 percent, with Class I restorations having a 92.6 percent success rate, Class II restorations having a 93.3 percent success rate, Class III restorations having a 100 percent success rate, and Class V restorations having a 98.0 percent success rate.

Conclusions. The resin-modified glass ionomer cement functioned well as a Class I, Class II, Class III and Class V restorative material in primary teeth.

Clinical Implications. Resin-modified glass ionomer restorative cement is a durable and reliable material to use for Class I, Class II, Class III and Class V restorations in primary teeth. Therefore, dentists have a proven alternative to silver amalgam and resin-based composite for primary tooth restoration.

Restoration of primary teeth continues to be an important facet of restorative dentistry. Traditionally, posterior primary teeth with occlusal and proximal surface caries have been restored with silver amalgam.² The introduction of stainless steel crowns offered a more effective restoration for posterior primary teeth with large carious lesions.^3,4 The advent of resin-based composite made available a material that bonded well to tooth structure, which created well-adapted margins, reinforced residual tooth structure and offered pleasing esthetics.^5–10 A major problem with resin-based composite in primary teeth is the potential of the cavity preparation’s being contaminated before the restoration is placed. Although we know that resin-based composite can be a successful restorative material for Class I and Class II restorations in primary teeth, isolation of the tooth often is a problem, and completion of such restorations can be very time consuming. These are serious practical disadvantages when treating children.

Glass ionomer cements, developed by McLean and Wilson,¹¹ also have been used to restore posterior primary teeth. Glass ionomer systems offer the advantages of a coefficient of thermal expansion similar to that of natural tooth structure, a physicochemical bond to enamel and dentin, and the release of fluoride for uptake by associated enamel and dentin.^12–16 The composition of the early glass ionomer cements did not provide compressive strength, wear resistance and color stability sufficient for a posterior restorative material in primary teeth. The physical properties of more contemporary glass ionomer cements, however, have improved, in part, by increased filler particle loading percentage, incorporation of a light-curable resin within the cement or both.¹⁷

Very few retrospective or well-controlled clinical trials have documented the success of these contemporary glass ionomer cements when used to restore primary teeth with Class I, Class II, Class III or Class V restorations. Glass ionomer cements—including the resin-modified glass ionomer cements—have demonstrated success as restorative materials, secondary caries inhibition at restoration margins and the ability to enhance remineralization on adjacent proximal caries.^18–35

The purpose of this article is to report the success of a contemporary resin-modified glass ionomer cement as a restorative material in primary teeth. This retrospective study provides data from restorations placed by one practitioner in a single-office private practice.

	SUBJECTS, METHODS AND MATERIALS

TOP ABSTRACT SUBJECTS, METHODS AND MATERIALS RESULTS DISCUSSION SUMMARY REFERENCES

 
We reviewed all active patient records from a private pediatric dental practice in Doylestown, Pa., a community that does not have a fluoridated water supply. A majority of the practice’s patients are from middle- to upper–middle-class families. For inclusion in this retrospective study, patients had to have had at least one resin-modified restoration in their mouths for a minimum of three years and clinical examination documentation of at least three years’ duration since placement of the restorations. In the case of a Class II restoration, a bitewing radiograph taken at least three years after treatment was done had to be available. All of the restorations had been placed by the pediatric dentist and owner of the private practice (T.P.C.). He used Vitremer Core Buildup/Restorative (3M ESPE)—a resin-modified glass ionomer cement—in the shade "pedo" for all restorations. Typical restorations are shown in Figure 1, Figure 2 and Figure 3. He used the following technique to place the resin-modified glass ionomer restorations.

View larger version (81K): [in this window] [in a new window]   Figure 1. A. Bitewing radiographs of 12-year-old child. The radiopaque resin-modified glass ionomer restorations of primary first molars are 6 years old, and the primary second molar restorations are 4 years old.

View larger version (102K): [in this window] [in a new window]   Figure 2. Occlusal resin-modified glass ionomer restoration in an exfoliated primary second molar seven years after placement.

View larger version (76K): [in this window] [in a new window]   Figure 3. Wear through to the dentin constitutes failure of these 7-year-old Vitremer Core Buildup/Restorative (3M ESPE) restorations.

The dentist prepared the teeth in a manner similar to that for analogous silver amalgam restorations; however, traditional extension of margins into cleansable areas was not part of the design. Internal line angles were rounded, and the mechanical interlocking retention form augmented the retention form derived from the adhesive bond.

The dentist placed a matrix strip, as required, as well as a retraction cord if needed for a Class V restoration. He spatulated powder and liquid components so that all of the liquid was blended completely into the powder, thus ensuring that the glass ionomer acid/base neutralization reaction would begin. He followed the manufacturer’s powder/liquid recommendations (one scoop of powder to one drop of liquid) for restorations placed in 1992, 1993 and part of 1994. After that time, he blended the cement using the highest powder/liquid ratio that could be achieved with assurance that all of the powder was wetted sufficiently by the acid solution and that the mixture was syringable.

Before the dentist injected the cement, he painted the cavity preparation and the peripheral enamel surfaces with primer and exposed the tooth to a curing light beam for 10 seconds. He used Accudose (Centrix Inc.) syringe tips to inject the blended cement into the cavity preparation. He bulk-filled it from the base of the cavity floor up to and beyond the cavosurface margins. Once the preparation was overfilled, he compressed the material with a latex-gloved finger or suitable hand instrument; to prevent sticking, the gloved finger or hand instrument was wiped with isopropyl alcohol or primer.

The dentist applied a concentrated visible light beam close to the tooth surface for 40 seconds. Then, using a large round diamond bur on a slow-speed handpiece, he trimmed the excess cement. Finally, he applied resin sealant to primary tooth restorations from 1992 to 1994, but he abandoned that practice in the mid-1990s.

	RESULTS

TOP ABSTRACT SUBJECTS, METHODS AND MATERIALS RESULTS DISCUSSION SUMMARY REFERENCES

 
In a review of the approximately 3,900 active patient records, we found 306 patients who met the entrance criteria for this study; 173 of the patients were boys, and 133 were girls. At the time of restoration placement, the children were from 1 to 10 years of age (mean 5 years, 2 months ± 1 year, 5 months, standard deviation). There was no significant difference in age between boys and girls (P < .001). These 306 children had a total of 393 Class I restorations, 406 Class II restorations, 15 Class III restorations and 50 Class V restorations. Table 1 identifies the restoration classification and mean (± SD) length of time the restorations were present in the subjects’ mouths. Table 2 shows the distribution of each restoration classification category. We could not compare the resin-modified glass ionomer cement restorations with any amalgam restorations or posterior resin-based composite restorations because the dentist used only resin-modified glass ionomer cement.

The overall success rate of the posterior Class I and Class II restorations was 93.0 percent (743 of 799); 92.6 percent (364 of 393) of the Class I restorations and 93.3 percent (379 of 406) of the Class II restorations succeeded.

	DISCUSSION

TOP ABSTRACT SUBJECTS, METHODS AND MATERIALS RESULTS DISCUSSION SUMMARY REFERENCES

 
Our findings demonstrate the effectiveness of this resin-modified glass ionomer cement for restorations in primary teeth. Previous reports also have noted the effectiveness of resin-modified glass ionomer cement as a restorative material in primary teeth.^{18–21,34,35}

The resin-modified cement used as the restorative material for all of the restorations we evaluated appears to have demonstrated a better success level than did the glass ionomer cement restorations used in the study reported by Mjör.³⁷ This could be attributed to several factors. Preparations and restorations were placed by multiple dentists in Mjör’s retrospective study, with no standardization among dentists. In our study, all of the restorations were placed by one dentist, who used a standard and consistent technique. It also should be noted that the data reported by Mjör involved restorations that had been placed before 1993. This would mean, as reported previously,³⁴ that most of the glass ionomer cement restorations Mjör evaluated were traditional chemically hardened cements, not a resin-modified glass ionomer cement such as that used in this study.

The age of children, extent of caries and assessment of potential oral hygiene maintenance are all important factors for dentists to consider when choosing an appropriate restorative material.

The resin-modified glass ionomer cement restorations in our study performed significantly better than did the glass ionomer restorations used in the study reported by Qvist and colleagues.³⁸ Again, we believe this is owing to the fact that, in their retrospective study, multiple dentists placed restorations that were evaluated in a nonstandardized manner, and the restorations were a conventional chemically hardened glass ionomer cement. Conventional glass ionomer cements exhibit less compressive strength, more wear and less fracture resistance than do contemporary resin-modified glass ionomer cements.^39,40 We consider such differences in physical properties of the respective glass ionomer systems so critical that perhaps there is no value in comparing our findings with those of Mjör³⁷ or Qvist and colleagues.³⁸

We noted other factors such as the caries risk level of the study population and standardization of dentists in placing and evaluating restorations. Although we believe that multiple dentists placing restorations—while not knowing at the time they will be analyzed in a retrospective study—can lend to variation in restorative technique, inclusion criteria and evaluation methodology, these retrospective studies may reflect the variety of restorative techniques typically used by dentists. Although more standardized, placement and evaluation by one dentist could create some bias. The dentist who placed all of the restorations in this study has been exposed to clinical trials and evaluation techniques (specifically, the U.S. Public Health Service methodology³⁶ since its introduction). He has been standardized in evaluation and calibrated previously to other standardized evaluators. For this reason, we believe the data presented from this study offer accurate, evidence-based results.

This study also had better restoration success rates than those reported by Donly and colleagues³⁴ in a study in which the same resin-modified glass ionomer cement was used. The dentist who placed all the restorations in our study started mixing the glass ionomer cement at the highest powder/liquid ratio possible but with assurance that all filler particles were wetted by the liquid acid solution.^41–45 This has been shown, in vitro, to reduce solubility of the glass ionomer cement.⁴⁶ Such a highly filled mixture could account for fewer failures in our study compared with the number in Donly and colleagues’³⁴ study, in which the initial experimental mixing recommendations were followed. Most failed Class I and Class II restorations in our study were caused by material wear. We did not have a way to accurately determine which of these restorations had a lower powder/liquid ratio. In addition, we did not correlate our findings with tooth-grinding habits in any patient.

Caries risk assessment is another factor that could play a role in restoration success. Twenty-three percent of the patients evaluated by Donly and colleagues³⁴ at three years had restoration failures as the result of secondary caries. Only 0.1 percent (1 of 864) of restorations in this study failed as the result of secondary caries; therefore, the patients we treated may have been at lower risk of developing secondary caries. The majority of patients in the practice in our study are from middle- to upper–middle-class families. The surgeon general’s report on Oral Health in America¹ noted that children who are at high risk of developing caries are from lower-income families, particularly lower-income, minority families. Regardless, both of these studies reported good success rates of resin-modified glass ionomer cement restorations in primary teeth.

Risk assessment also is critical in treatment planning, and age of children, extent of caries and assessment of potential oral hygiene maintenance are all important factors for dentists to consider when choosing an appropriate restorative material. Stainless steel crowns may be more appropriate to use when restoring teeth with proximal carious lesions in young children who are at high risk of developing caries. It should be noted that the dentist providing all of the care in this study followed basic standards of pediatric restorative dentistry; he used stainless steel crowns for teeth with proximal carious lesions in which the cavity preparation extended beyond the line angles of the tooth. Therefore, the resin-modified restorations placed in this study were conservative; extensive caries in primary molars and canines still necessitates stainless steel crown restoration.^47,48

	SUMMARY

TOP ABSTRACT SUBJECTS, METHODS AND MATERIALS RESULTS DISCUSSION SUMMARY REFERENCES

 
The findings in this retrospective study indicate that resin-modified glass ionomer cement is an effective restorative material for Class I, Class II, Class III and Class V restorations in primary teeth.

View larger version (119K): [in this window] [in a new window]   Dr. Croll is in private practice in pediatric dentistry, Doylestown, Pa. He also is an adjunct clinical professor, Department of Pediatric Dentistry, Dental School, University of Texas Health Sciences Center at San Antonio; a clinical professor, Department of Pediatric Dentistry, University of Pennsylvania, School of Dental Medicine, Philadelphia; a clinical professor, Craniofacial Growth and Development (Pediatric Dentistry), University of Texas Health Science Center at Houston Dental Branch; and an adjunct associate professor, Department of Pediatric Dentistry, University of Iowa, College of Dentistry, Iowa City. Address reprint requests to Dr. Croll at Georgetown Commons, Suite 2, 708 Shady Retreat Road, Doylestown, Pa. 18901.

View larger version (131K): [in this window] [in a new window]   Dr. Bar-Zion is a postdoctoral student in pediatric dentistry, Department of Pediatric Dentistry, Dental School, University of Texas Health Science Center at San Antonio.

View larger version (118K): [in this window] [in a new window]   Dr. Segura is an associate professor and the director, Predoctoral Program, Department of Pediatric Dentistry, Dental School, University of Texas Health Science Center at San Antonio.

View larger version (126K): [in this window] [in a new window]   Dr. Donly is a professor and the director, Postdoctoral Program, Department of Pediatric Dentistry, Dental School, University of Texas Health Science Center at San Antonio.