Glass Ionomer as Fissure Sealant—a Critical Review

146 Journal of Public Health Dentistry

Glass Ionomer as Fissure Sealant-a Critical Review

Richard J. Simonsen, DDS, MS

Abstract This paper presents a review of the literature on glass ionomer cements used

as fissure sealants. An objective assessment of the presently available scientific literature on the use of glass ionomer materials as pit and fissure sealants is not encouraging in terms of retention, but appears somewhat more positive for caries prevention. At the time of this writing, the published literature indicates that retention for resin-based sealants is better than for glass ionomer sealants, but differences in caries prevention remain equivocal. Future research should con- centrate on assessing the effects of fluoride-releasing, resin-modified, glass ionomer materials. [J Public Health Dent 1996;56(3): 146-91

Key Words: glass ionomer, pit and fissure sealants, retention rate, caries control.

This paper reviews the literature on use of glass ionomer cements as fissure sealants. First, the historical papers on fissure sealing will be discussed, followed by the development of glass ionomer materials, and a review of studies on glass ionomer sealant retention. Next, the studies comparing resin-based and glass ionomer sealants will be assessed, followed by a review of one study looking at the caries rate with a reapplied glass ionomer material. Finally, studies comparing caries rates with glass ionomer versus resin-based sealants will be reviewed. Incomplete reports, some poorly designed studies, and differing or poorly described criteria for critical areas such as retention (i.e., some authors regard “retention“ as complete plus partial retention, rather than separate categories) diminished the number of studies that could be analyzed, and made comparisons among most studies impossible.

Historical Reports The first reference in the literature

to sealing of teeth is from 1895, when Wilson reported in Dental Digest a technique for sealing fissures with oxyphosphate cement (1 1. Although unsuccessful at long-term caries prevention, Wilson noted, with admirable preventive vision, ” ... if decay has

been prevented for only a few months or years, and the same treatment is then repeated ... more of the tooth structure has been preserved.” In an earlier publication in the Dental Cos- mos of 1884, Perry reported that he treated patients under 10 years of age by filling the fissures and grooves with oxyphosphate cement and covering it with Sandarac varnish (2). This paper was more about restorative procedures, however, than one about a preventive sealant technique.

Methods such as fissure eradication or treatment with alternative chemi- cals were attempted in the intervening years from the turn of the century until Buonocore‘s historic 1955 paper re- porting the acid-etch technique (3). The earlier methods were not success- ful beyond short-term prevention of caries. Buonocore’s paper referred to ”the possibility of successfully sealing of pits and fissures for purposes of caries prevention.” This work, combined with the development of a vari- ety of resin-based sealants, revolution- ized preventive as well as restorative dentistry. The first sealant was marketed in 1970. The longest running clinical study published in the literature is of a resin-based sealant report- ing results after 15 years (4). In this study, the percents of sound (noncari- ous, nonrestored) surfaces after a sin-

gle application of Concise White Sealant (3M Dental) at baseline in 1976 were 94 percent at 5 years, 84 percent at 10 years, and 74 percent at 15 years. The percent of sound surfaces in the unsealed control group was 17 percent after 15 years. Complete retention (all pits or fissures covered with sealant) was 28 percent, and partial retention (any previously sealed portion of a pit or fissure uncovered) was 35 percent after 15 years.

Glass Ionomer Materials The use of glass ionomer materials

in dentistry has expanded tremen- dously since the first report by Wilson and Kent (5) in 1971. In the past 20 years clinicians have accepted glass ionomer cements as a routine part of their operative dentistry armamentar- ium. During the same time period at- tempts were made to use glass ionomer materials, both restorative cements and more diluted materials, as sealants. A review of the literature on these studies follows.

Glass Ionomer Materials as Sealants-Retention

The first paper on fissure sealing with an adhesive glass ionomer cement was by McLean and Wilson (6) in 1974. They reported a high success rate using selected fissures-the im- portant word here being selected. Their recommendation, which has to a large degree been disregarded in sub- sequent studies, was: “glass ionomer cements are only suitable as fissure sealants where the pit or fissure orifice exceeds 100 nun.” Using this criterion, McLean and Wilson (6) found 84 percent of glass ionomer sealants remained completely intact after one year, and 78 percent remained completely intact after two years. In this study teeth were etched with 50 percent citric acid for 30 seconds and the glass ionomer material (ASPA II, De-

Send correspondence to Dr. Simonsen, Professional Services Manager, 3M Company, Dental Products Division, Building 260-2B-13, St. Paul, MN 55144-1000. Internet: [email protected]. Send reprint requests to Dr. Taco Pilot, WHO Collaborating Centre for Oral Health Services Research, University of Groningen, c/o Woerdakkers 5, 9461 EB Gieten, the Netherlands. Presented orally at the symposium on ’‘Minimal Intervention Techniques for Caries” at the 73rd General Session of the International Association for Dental Research in Singapore, June 29,1995.

Vol. 56, No. 3, Special Issue 1996 147

Trey) was applied, first in a thin mix for penetration, and then in a thick mix for strength. They observed no clinical caries in the sealed surfaces, although it appears that the caries analysis was carried out as a minor part of a study designed specifically to report on retention.

Seppa and Forss (7) looked at the effect of glass ionomer sealant (Fuji Ionomer Type m, GC Dental) on fissures exposed to artificial cariesmedia after sealant removal. Extracted teeth weredivided into three groups: Group l-control group, Group 2-untreated fissures, and Group 3-fissures widened with a narrow dia- mond stone. Groups 2 and 3 were sealed with Fuji III. After one week the sealants were removed "as completely as possible with a sharp probe, so that no residual material was left in the fissure macroscopically." (It should be noted that this step probably could not be accomplished with a resin-based sealant without use of some mechani- cal or rotary instrumentation.) All three groups of teeth were then sub- jected to artificial caries attack. The teeth were sectioned and mean depths of fissure lesions measured. Differ- ences between the control and sealed fissures were statistically significant (P<.Ol), but those between untreated and widened sealed fissures were not. The results suggest that the fissures sealed with a glass ionomer sealant are more resistant to demineralization than unsealed fissures, even after the sealant appears to be lost. While lesion formation was not completely inhib- ited, glass ionomer sealant did appear to increase the resistance of fissure enamel to demineralization.

McKenna and Grundy (8) studied retention of glass ionomer cement applied by Australian school dental therapists working in "normal train- ing conditions." They reported 93 percent complete retention after6 months and 82.5 percent complete retention after 12 months. The authors stated that these rates were comparable with those obtained with BisGMA resin sealants in other studies. Only first permanent molars were sealed in this study. While no definition is provided for complete retention, these retention results are among the highest seen in the literature for glass ionomer sealants.

Glass Ionomer Materials vs Resin- based Sealants-Retention

Five studies have compared the retention rates of glass ionomer and resin sealants in the same study. Boksman et al. (9) reported in 1987 on the comparison between Concise White Light Cured Sealant (3M Den- tal) and Fuji 111 glass ionomer sealant. At the six-month recall 94 percent of the resin sealants placed were available for evaluation, and 93 percent of the glass ionomer sealants. Sealant was reported as totally present at 92.2 percent for the Concise sealants and 1.7 percent for the Fuji 111 sealants. Ninety-four percent of the glass ionomer sealant was totally absent at six months and as a result the pro- posed protocol was discontinued at the six-month point.

Widmer and Jayasekera (10) compared the retention of glass ionomer cement and resin sealants in newly erupted permanent first molars, which were cleaned with hydrogen peroxide prior to sealing. Retention rates in occlusal fissures for resin sealants were 91 percent at one year and 85 percent at two years. For glass ionomer cement the retention rate at one year was 83 percent and at two years 67 percent.

Ovrebo and Raadal (11) investi- gated the microleakage in fissures sealed with glass ionomer cement and diluted resin composite in permanent premolar teeth scheduled for ortho- dontic extraction. A split-mouth technique wasused on lopairsof teethand Fuji 111 glass ionomer and Concise resin composite (3M Dental) were the study materials. Fissures were air pol- ished prior to sealing. After 14 days, all the diluted resin sealants were intact, while three of the glass ionomer sealants were totally missing, one was partially missing, and six were intact. Extensive leakage determined by dye penetration was seen in all glass ionomer specimens at the interface between cement and enamel. No leakage was reported in the resin specimens. The authors concluded that Fuji 111 is poorly retained in the fissures and that the material permits leakage even when it is fully retained.

Mejhre and Mjor (12) reported on a clinical comparison of glass ionomer (Fuji In) and two resin-based fissure sealants, namely, Concise White Sealant and the conventional autopo- lymerizing Bis-GMA sealant Delton

(formerly Johnson &Johnson, now LD Caulk). As judged clinically, 61 percent of the glass ionomer sealants were lost within 6 to 12 months and 84 percent after 30 to 36 months. Although total loss was recorded clinically for the majority of the glass ionomer sealants, some retained sealant was seen in tooth replicas of 93 percent of the glass ionomer samples. Resin sealants showed a complete retention rate of 90 percent after 4.5 to 5 years. The authors noted that canes was recorded in 5 percent of surfaces with resin sealants and in none of the glass ionomer sealed surfaces. This study is sometimes cited as an example of glass ionomer sealants performing better in terms of canes reduction than resin sealants. However, the aim of this study was to compare retention rates, and caries incidence was not analyzed statistically, presumably because the number of lesions was too small. Only eight surfaces in total were diagnosed as carious. Six of these surfaces were on teeth sealed with Delton and two on teeth sealed with Concise. In six of the eight lesions,caries was diagnosed after 6 to 12 months while the final two lesions were diagnosed 2.5 and 4 years after sealing. In view of the long latent period between caries initiation and the possibility of clinical diagnosis, it would appear that at least some of the lesions (those diagnosed at 6-12 months) were present prior to sealing. Because of this possibility and the small number of lesions, the authors summarized that "any conclusions about a possible long-term caries-preventive effect cannot be drawn from the present results."

Mills and Ball (13) reported in 1993 on a clinical trial undertaken to compare the retention of a silver cermet- ionomer cement, Ketac Silver (ESPE), with the resin sealant Delton on first and second permanent molars. Ketac Silver is designed to be a restorative material, not a sealant. Teeth were etched in an identical manner for both proceduresalthough it was not so specified, presumably this was in a manner consistent with resin-etching techniques, i.e., for 60 seconds with phosphoric acid. A relatively high attrition rate occurred in this study, the study population declining to under 50 percent at 24 months. The authors concluded that the cermet cement was better retained than Delton in younger children. The authors reported 93 per-

Journal of Public Health Dentistry

cent retention for Ketac Silver at six months versus 74 percent for Delton. At two years the figures were 83 percent and 58 percent for Ketac Silver and Delton, respectively. No definition was given of exactly what was meant by ”present” in the study and the retention rates that the authors obtained for the conventional resin sealant are considerably lower than those reported in many other studies. Also, teeth sealed with the glass ionomer restorative material were etched, a procedure contrary to recom- mended procedures, but one that could improve retention.

A similar study by Sipahier and Ulusu (14) using permanent first molars found that Ketac Silver was lost faster than resin-composite sealant, but found no difference in canes incidence between the two groups. Ketac Silver exhibited 23 percent complete retention at one year, compared to the 83 percent at two years found by Mills and Ball (13). One-year complete retention for Delton was 41 percent, which is far lower than usual for this material. Despite this finding, they concluded that ”Ketac-Silver cannot be considered an alternative to Bis- GMA resin fissure sealant.”

Glass Ionomex Materials-Caries Rate

One study reported on the caries- preventive effects of glass ionomer sealant without comparison with a resin sealant (15). In this study the retention rate-70 percent a t three years-was maintained by reapplying sealant every six months. Not surpris- ingly, the authors reported relatively high retention and caries reduction rates. Significant problems exist for assessing the validity of the data presented in this study, however. There is no indication that the original sample of children selected (n=92) is a random sample, nor that those few subjects available for follow-up examinations (n=32) were representative of the original sample. The control group was “301 teeth selected from school records.” The published report does not indicate if this control group was matched to the test group or random- ized in any way. These limitations, combined with the high attrition rate of patients, raise serious doubts about the validity of the data. Authors reported canes incidence at one, two, and three years, but did not indicate if

the change in caries was an incre- mental increase or canes incidence. If the latter, it is impossible to assess the results without baseline data. Al- though Figure l in their paper appears to indicate that caries prevalence at baseline was zero for both groups, no mention of this was made in the text, and this apparent prevalence might simply be an artistic rendition. “Reten- tion” was reported as the sum of complete and partial retention; thus, any remaining material in a pit or fissure apparently would allow the sealant for that tooth to be regarded as “retained.” Therefore, no comparison with other studies is possible. For example, the quoted overall retention rate at six months was 83.1 percent; however, complete retention was ac- tually 44.6 percent. The authors reported retention rates ranging from 83 percent at six months to 70 percent at three years, again noting that reappli- cation of the sealant took place every six months.

Glass Ionomer Materials vs Resin- based Sealants-Caries Rates

Those studies that looked at caries rates in patients sealed with glass ionomer sealant compared to those with resin sealant are probably the most relevant to the topic of this paper and are reviewed here. Williams and Winter reported three studies (16-18) from 1976-81, one with an additional coauthor (17), on the results of clinical trials using glass ionomer materials and resin sealants. In their first study published in 1976, Williams and Win- ter (16) reported that a glass ionomer material, ASPA II, and an experimen- tal resin sealant were as effective as a commercially available resin sealant, Nuva-Seal (LD Caulk), in preventing the initiation of pit and fissure caries. In their second study (171, the authors compared a new version of the ASPA material, ASPA IV, with Nuva-Seal (an unfilled dimethacrylate resin), and with a Concise and Concise Enamel Bond (3M Dental) system (a filled dimethacrylate resin). The authors found that Concise was significantly better in reducing caries than Nuva- Seal or ASPA IV (P=.OOl), and that ASPA IV and Nuva-Seal were not significantly different from each other in their cariostatic properties. Concise, of course, is a restorative material and it was used in this study in conjunction with Concise Enamel Bond, which by

itself could function as an unfilled resin fissure sealant. ASPA IValso was marketed as a restorative material and was applied in this study in the same manner as the original ASPA used by McLean and Wilson (6), where a thin slurry was applied first and a thicker mix applied on top of the thin mix.

In 1981 Williams and Winter (18) published four-year data on their study (18). Once again, the filled resin was significantly better than the glass ionomer material at reducing occlusal caries. After four years, 87.9 percent of the Concise resin was retained and only 7.7 percent of the 549 surfaces originally sealed with Concise were found to be carious. Of the 549 surfaces treated with Nuva-Seal, 35.9 percent retained resin, and 20.8 percent be- came carious. No untreated teeth were available for comparison of caries incidence in this study. In comparing ASPA IV with Nuva-Seal, the authors found that despite a high initial loss of ASPA IV, at the end of four years the overall retention rates of the two materials were similar at 35.4 percent and 34.4 percent, respectively. At four years, caries incidence in surfaces sealed with ASPA IV was 13.1 percent, and for those sealed with Nuva-Seal was 19.1 percent, a statistically significant difference (P<.Ol).

Forss, Saarni, and Seppa (19) compared glass ionomer and resin-based fissure sealants in a two-year clinical trial published in 1994. They found much better retention with resin- based sealants, but similar caries rates. At two years, 26 percent of the glass ionomer sealant (Fuji III) and 82 percent of the resin-based sealant (Delton) were totally present (P<.OOl). Over the two years both groups showed 4.6 percent of the sealed surfaces becoming carious. The authors interpreted their results to mean that the retention of glass ionomer sealants, while mark- edly inferior to the resin-based sealants, might still be adequate for similar levels of caries protection. They also noted an overall low caries activity for all participants in this study.

Arrow and Riordan (20) presented a paper in 1994 comparing caries-preventive effects and retention of resin and glass ionomer sealants. A glass ionomer restorative material, Ketac- Fil (ESPE), was tested against a chemi- cally cured, resin-based sealant @el- ton) using a split design over 3.6 years.

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In the 412 pairs of teeth examined and compared, 378 showed neither tooth to be carious. In 28 pairs the test tooth (GIC) was sound and the control tooth carious; in three pairs, both teeth were carious; in the final three pairs, the test tooth ( G I 0 was carious and the control tooth sound. This well-designed study conducted in the Australian Dental Service showed that glass ionomer material, in this case a restorative material, was not retained as well as resin sealant, but that its caries preventive effects were greater than those of resin sealants.

In 1995, Songpaisan and coworkers (21) published results of a study comparing the effects of glass ionomer cement (Fuji III) with a resin-based pit and fissure sealant (Delton) in a field trial in Thailand. Children with at least three sound permanent molars from two age groups, 7-8 and 12-13 years of age, were chosen from very low to medium socioeconomic-level families. In the younger age group the two-year mean DFS occlusal increment for the control group was 0.66 surfaces. The test groups had Fuji 111 glass ionomer sealant applied in two ways, either by dentists or by teachers trained for three days in application techniques. The younger age group with teacher- applied sealant had a two-year mean DFS occlusal increment of 0.17 surfaces per child, for a 74 percent reduction in caries. The children with sealants applied by the dentists had a two-year mean DFS occlusal increment of 0.32 corresponding to a 52 percent caries reduction. In the 12-13- year-old group the mean occlusal sur- face DF increment was 0.70 surfaces for the control group. For the group sealed with conventional resin-based sealant the occlusal two-year mean DFS increment was 0.05 or a 93 percent reduction in canes. In the GIC dentists group the DFS increment was 0.48, a 31 percent reduction, and in the teacher group 0.56, a 20 percent reduction. Retention of Delton sealant was high, 92 percent after six months, while retention of the GIC sealant was low, 2 percent to 8 percent at six

months. For practical reasons the younger group was not treated with resin-based sealants. In this study, therefore, the resin-based sealant showed much better retention and, concomitantly, much better caries reduction.

Conclusions and Recommendations Based on this review of studies of

glass ionomers as fissure sealants, two major conclusions are possible: (1) Resin sealants exhibit better retention than glass ionomer sealants. Some glass ionomer restorative materials, however, have shown better retention than glass ionomer sealants, but poorer retention than resin composite material. (2) Caries prevention benefit from the use of glass ionomer sealants vis-5-vis resin sealant is equivocal. Of the six studies that specifically compare glass ionomer and resin sealants or restorative materials in the same study, three found resin superior at preventing caries (17,18,21), two found no difference (16,19), and one found glass ionomer materials superior (20).

This review of the literature on glass ionomers also leads to two recommendations: (1) more controlled clinical trials are needed comparing caries re- ductions resulting from the use of resin-modified glass ionomer materials, resin sealants, and glass ionomer materials; and (2) materials research should be directed at development of new, user-friendly sealant materials that takeadvantage of new technology developed over the past few years in resin-modified glass ionomer materials and in dentin bonding systems.

References 1. Wilson IP. Preventive dentistry. Dent Di-

gest 1895;1:70-2. 2. Perry SG. Proceedings of dental societies.

American Dental Association 23rd an- nual session. Dent Cosmos 1884;26:96.

3. Buonocore MG. A simple method of in- creasing the adhesion of acrylic filling materials to enamel surfaces. J Dent Res

4. Simonsen RJ. Retention and effectiveness ofdentalsealantafter15year.s. JAmDent A s s 1991;122:3442.

1955345349-53.

5. Wilson AD, Kent BE. A new translucent cement for dentistry. The glass ionomer cement. Br Dent J 1972;132:133-5.

6. McLean JW, Wilson AD. Fissure sealing a n d filling with an adhesive glassionomer cement. Br Dent J 1974;136269- 76.

7. Seppa L, Forss H. Resistance of occlusal fissures to demineralization after loss of glass ionomer sealant in vitro. Pediatr Dent 1991;13:3942.

8. McKenna EF, Grundy GE. Glassionomer cement fissure sealants applied by o p r a - tive dental auxiliaries-retention rate after one year. Aust Dent J 198732:20@-3.

9. Boksman L, Gratton DR, McCutcheon E, Plotzke OB. Clinical evaluation of a glass ionomer cement a s a fissure sealant. Qumtessence Int 1987;18:707-9.

10. Widmer RP, Jayasekera TR. Fissure sealing with a glass ionomer cement: 2-year results [Abstract]. J Dent Res 1989;68:539.

11. Ovrebo RC, Raadal M. Microleakage in fissures sealed with resin or glass ionomer cement. Scand J Dent Res 1990;98:669.

12. Mejire I, Mj6r IA. Glass ionomer and resin-based fissure sealants: a clinical study. %and J Dent Res 1990;98:345-50.

13. Mills RW, Ball IA. A clinical trial to evalu- ate the retention of a silver cermet- ionomer cement used asa fissuresealant. Oper Dent 1993;18:148-54.

14. Sipahier M, Ulusu T. Glass-ionomer-silver-cermet cements applied as fissure sealants. 11. Clinical evaluation. Quintes sence Int 1995;26:43-8.

15. Komatsu H, Yoshimura M, Ohshima K, et al. Enamel fluoride uptake from glass ionomer cement designed for use as a fissure sealant. J Am Dent Assoc 1994; 125543-9.

16. Williams B, Winter GB. Fissure sealants: a 2-year clinical trial. Br Rent J 1976;141:

17. Williams B, Price R, Winter GB. Fissure sealants: a 2-year clinical trial. Br Dent J 1978;145:359-64.

18. Williams B, Winter GB. Fissure sealants: further results at 4 years. Br Dent J 1981;150:183-7.

19. Forss H, Saarni U-M, Seppa L. Compari- son of glass-ionomer and resin-based fissure sealants: a 2-year clinical trial. Com- munity Dent Oral Epidemiol 1994;22:21- 4.

20. Arrow P, Riordan PJ. A comparison of caries preventive effects and retention of resin and GIC sealants [Abstract]. J Dent Res 1994;73:745.

21. Songpaisan Y, Bratthall D, Phanhunvanit P, Somridhivej Y. Effects of glass ionomer cement, resin-based pit and fissure sealant and HF applications on occlusal caries in a developing country field trial. Community Dent Oral Epidemiol 1995; 23:259.

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Glass Ionomer as Fissure Sealant—a Critical Review