ORIGINAL RESEARCH |
https://doi.org/10.5005/jp-journals-10005-2695 |
Comparative Evaluation of Effect of Silver Diamine Fluoride and Glass Ionomer Cement on Microhardness of Artificial Caries Lesion in Primary Teeth: An In Vitro Study
1–4Department of Pediatric and Preventive Dentistry, Yenepoya Dental College and Hospitals, Yenepoya (Deemed to be University), Mangaluru, Karnataka, India
Corresponding Author: Sahanai Sunny, Department of Pediatric and Preventive Dentistry, Yenepoya Dental College and Hospitals, Yenepoya (Deemed to be University), Mangaluru, Karnataka, India, Phone: +91 9442737577, e-mail: sahanaisunny93@gmail.com
ABSTRACT
Aim: To evaluate the remineralizing potential of glass ionomer cement (GIC) and silver diamine fluoride (SDF) on artificially induced enamel caries lesions in primary teeth.
Materials and methods: The initial baseline surface microhardness (SMH) of 40 primary teeth was tested using Vickers hardness tester, followed by the creation of artificial caries lesions by immersion in the demineralizing solution. Microhardness assessments of demineralized samples were done, and samples were randomly divided into two groups of 20 specimens: in group I, GIC was applied on demineralized enamel, and in group II, SDF was applied on demineralized enamel. Samples were subjected to pH cycling. For group I, GIC from the enamel samples was carefully removed using a surgical blade, and changes in the SMH from both groups were analyzed using Vickers microhardness test.
Result: Surface microhardness (SMH) value after pH cycling of GIC (45 ± 10.23) and SDF (47.76 ± 6.69) is statistically highly significant (<0.001) compared to the baseline SMH of both test groups. Comparison of SMH between the two groups showed statistically nonsignificant results.
Conclusion: The remineralization potential of SDF is comparable to GIC. So, SDF can be used as a remineralizing agent for incipient enamel caries.
Clinical significance: Owing to the remineralizing ability of GIC underneath the restorations, it can be used as a therapeutic sealant for incipient enamel caries lesions, where SDF staining is not always acceptable. A 38% SDF also can be used as a remineralizing agent for incipient enamel caries lesions in situations like noncompliant patients, inaccessibility to dental care, or conditions in which esthetics is not of concern.
How to cite this article: Sunny S, Sargod SS, Bhat SS, et al. Comparative Evaluation of Effect of Silver Diamine Fluoride and Glass Ionomer Cement on Microhardness of Artificial Caries Lesion in Primary Teeth: An In Vitro Study. Int J Clin Pediatr Dent 2023;16(6):858–863.
Source of support: Nil
Conflict of interest: None
Keywords: Glass ionomer cement, Incipient enamel lesions, Microhardness, Remineralization, Silver diamine fluoride
INTRODUCTION
Dental caries is the most common disease affecting many children of any age-group. The first stage of the disease, known as an incipient caries lesion, affects the tooth’s enamel surface. These caries lesions can be treated noninvasively by applying remineralizing substances to the enamel surface, such as fluoride (F) varnish, silver diamine fluoride (SDF), casein phosphopeptide-amorphous calcium phosphate, glass ionomer cement (GIC), and other substances comprising bioglass, hydroxyapatite, and calcium phosphate, among others.1 The balance between pathogenic factors that favor demineralization (cariogenic bacteria, fermentable carbohydrates, salivary dysfunction) vs those that tilt it in favor of remineralization (antibacterial agents, sufficient saliva, remineralizing ions) determines whether a lesion advances or reverses.2 So, the goal of oral hygiene and anticaries procedures should be to enhance the remineralizing phase of the remineralizing and demineralizing cycle in the oral cavity. However, the potential of F to remineralize dental caries is still considered the benchmark against which other remineralization strategies must compete, whether used alone or in conjunction with F treatments.3
Silver diamine fluoride (SDF) is a silver compound-based remineralizing agent introduced in Japan in 1969 by Mizuho Nishino, which helps in establishing a healthy balance between pathological and protective factors. The ability of SDF to inhibit caries and remineralize the developing caries lesion has been demonstrated in numerous investigations. Annual treatment of SDF prevented active initial caries and reduced the incidence of new caries more than a 3-month application of NaF varnish in a randomized clinical investigation.4
However, SDF, when applied over the carious enamel, causes discoloration due to silver precipitation.5 As most of the smooth surface carious lesions in children occur in the anterior tooth region, it may not be accepted for esthetic restoration. GIC can also be regarded as a remineralizing agent since it chemically bonds to the tooth, releases F slowly over time, and serves as a reservoir for F, aiding in subsurface remineralization.
It has been found that F released from GIC is incorporated in adjacent teeth and saliva. Ionic F, ionic AlF6, and fluorophosphate molecules are the primary forms of F produced by GIC. Additionally, when the pH in the oral cavity is low, the exposed surface of GIC can release F ions forming fluorapatite. Glass ionomer restorations maintain their high F levels in the saliva for at least a year.6,7
Various studies have shown the remineralization effect of SDF and GIC on the dentin of permanent teeth. However, only a few have studied the remineralizing potency of SDF and GIC on incipient caries lesions of primary teeth. The present study used a microhardness test to compare the remineralizing potentials of SDF and GIC on artificial enamel caries of primary teeth.
MATERIALS AND METHODS
The study proposal was reviewed and cleared by the Yenepoya Ethics Committee and the study was carried out in the Department of Pedodontics and Preventive Dentistry.
Tooth Preparation
A total of 40 human noncarious primary teeth indicated for extraction or exfoliated naturally were used for the study. These primary teeth were mounted in acrylic using an ”L” shaped mold, and the surface of the teeth was polished using sandpaper and polishing pumice (Figs 1 and 2).
Fig. 1: Tooth specimen mounted in acrylic resin
Fig. 2: Armamentarium for application of SDF and GIC
Test Procedure
The initial baseline surface hardness of the enamel was tested using Vickers hardness test. The enamel surface was subjected to the formation of artificial caries by immersing in the demineralizing solution (0.2% polyacrylic acid, 85% lactic acid, hydroxyapatite, and 6 M sodium hydroxide) at pH 4.8 for 7 days at 37°C. The specimens with induced demineralization lesions were washed with deionized water, and the surface hardness of the specimen was again assessed using Vickers microhardness tester (Fig. 3). Samples were randomly divided into two groups of 20 specimens each.
Fig. 3: Vickers microhardness tester
In group I, GIC was applied to demineralized enamel, and in group II, SDF was applied to demineralized enamel. The enamel blocks were immersed in the demineralizing and remineralizing solutions in eight cycles for 7 days to mimic the oral cavity. For group I, GIC from the enamel samples was carefully removed using a surgical blade, and the microhardness of the enamel of both groups was tested using Vickers microhardness test.
The enamel sample was tested using a diamond indenter in the shape of a right pyramid with a square base and an angle of 136° between opposite faces. A weight of 10 kgf was applied for 10 to 15 seconds. Each sample’s average of the two diagonals of the indentation left on the material’s surface after the load is calculated using a microscope (Fig. 4).8
Fig. 4: Indentation seen on enamel surface with frequency distribution and variation graphs
Statistical Analysis
Data are presented in mean ± standard deviation. An independent t-test/corresponding nonparametric test was used to compare the groups. Paired t-tests/corresponding nonparametric tests were used to compare pre- and postchanges. Data analysis was done using Statistical Package for the Social Sciences software.
RESULTS
Before demineralization, the mean baseline surface microhardness (SMH) values between the groups were statistically insignificant (Table 1). Statistically, no significant difference was found between the groups in the mean SMH value following demineralization (Table 2). Comparing SMH values after pH cycling to SMH values after demineralization, both treatment groups’ SMH values had comparatively increased (<0.001), which is statistically extremely highly significant (Table 3 and Fig. 5).
| Groups | Ν | Minimum | Maximum | Median ± interquartile range (IQR) | |
|---|---|---|---|---|---|
| 1 | Baseline | 20 | 29.30 | 65.50 | 47.65 ± 8.23 |
| Demineralized | 20 | 23.00 | 63.10 | 40.73 ± 9.05 | |
| GIC | 20 | 24.00 | 67.40 | 45.51 ± 10.23 | |
| 2 | Baseline | 20 | 35.20 | 55.90 | 47.03 ± 6.18 |
| Demineralized | 20 | 33.10 | 53.90 | 44.30 ± 6.12 | |
| SDF | 20 | 36.30 | 61.30 | 47.76 ± 6.69 |
| Characteristics | Ν | GIC median ± IQR | SDF median ± IQR | p-valueA |
|---|---|---|---|---|
| Baseline | 20 | 47.65 ± 8.23 | 47.03 ± 6.18 | 0.860 |
| Demineralized | 20 | 40.73 ± 9.08 | 44.30 ± 6.12 | 0.386 |
| After | 20 | 45.51 ± 10.23 | 47.76 ± 6.69 | 0.442 |
p-valueA, Mann–Whitney U test; *p < 0.05 is statistically significant; **p < 0.01 is statistically highly significant; ***p < 0.001 is statistically very highly significant
| Characteristics | Ν | GIC median ± IQR | SDF median ± IQR |
|---|---|---|---|
| Baseline | 20 | 47.65 ± 8.23 | 47.03 ± 6.18 |
| Demineralized | 20 | 40.73 ± 9.08 | 44.30 ± 6.12 |
| After | 20 | 45.51 ± 10.23 | 47.76 ± 6.69 |
| NA | 0.001*** | 0.001*** |
p-valueA, Wilcoxon sign rank test; *p < 0.05 is statistically significant; **p < 0.01 is statistically highly significant; ***p < 0.001 is statistically very highly significant
Fig. 5: Comparison of SDF and GIC from baseline to remineralization
DISCUSSION
This research examined the effect of SDF and GIC on the microhardness of enamel caries lesions artificially produced in primary teeth. After demineralization, both SDF and GIC led to a comparable increase in the microhardness of enamel caries induced artificially. No significant difference was found between the pretest and posttest microhardness of the SDF or GIC groups. Thus, the findings suggest that GIC and SDF may have an equivalent remineralizing effect on enamel.
Saliva is crucial to the progression of caries remineralization. It is a buffered process of calcium and phosphate supersaturated, with proline and tyrosine-rich proteins limiting excessive nucleation of apatite phases. As calcium and phosphate ions are part of the hydroxyapatite unit cell, calcium and phosphate ion activity in the saliva is critical. Therefore, saliva provides teeth with a protective and reparative environment. Aside from the salivary environment, the residual mineral crystals of the tooth may also play a significant role in remineralization; the crystals serve as a nucleation site for the newly created fluoro hydroxyapatite to precipitate, or they facilitate the ion exchange of F− for OH−. However, the exchange of F− for OH necessitates an acidic microenvironment to break down the tooth mineral and liberate OH. SDF is quite alkaline (pH ~ 10). This alkaline feature coincides with the favorable conditions required to synthesize fluoro hydroxyapatite in chemistry, which may speed up the precipitation process by accelerating the reaction.9
With a high concentration of silver (255000 ppm) and F (448000 ppm) in the commercial SDF solution used in this research, clinical treatment consists of a single application of a minute volume of the solution (0.22 and 0.07 mg) to carious lesions. In the oral environment, SDF is rapidly diluted by saliva in the oral cavity, which has a volume of around 0.60 mL and a concentration of approximately 0.22/0.60 or 0.36 mg/mL per application.9
Rosenblatt et al. demonstrated that SDF and hydroxyapatite create calcium fluoride and silver phosphate in a basic environment.10 During the cariogenic challenge, calcium fluoride serves as a pH-regulated, slow-release F reservoir. Also, hydrogen phosphate ions (HPO4) stimulate the formation of fluorapatite from calcium fluoride. Silver phosphate is more soluble than hydroxyapatite and fluorapatite; as a result, it serves as a reservoir of phosphate ions that facilitates the synthesis of fluorapatite from calcium fluoride.11
The GIC’s core mechanism for caries lesion remineralization under the lesion has been proven without direct oral exposure. The polycarboxylic acid group (COO) in GIC creates ionic interactions with the calcium in enamel and dentin. When the GIC powder and liquid are thoroughly mixed, metals (such as strontium, calcium, and aluminum) and F ions are produced. After placing a GIC filling, F levels in the plaque remained significantly increased for months.12 In addition, hydroxyapatite crystal formation studies indicate that silica produced by the GIC restoration could promote mineralization.13
Initial F release from the restored glass ionomer is caused by an acid-base reaction, with the amount of F released proportional to the material’s F level. This is the cause of the ”burst effect” phenomenon, in which significant levels of F are released in the first 2 days. F release drops fast during the 1st week and stabilizes after 3–4 weeks. F absorbed by the tooth lowers demineralization and enhances remineralization. F ions are released during the cement’s acid-base reaction, but they are not required for matrix formation. They can, therefore, freely enter and exit the cement. Thus, GIC is regarded as a F reservoir, delivering a steady flow of F ions into the surrounding tooth structure and increasing resistance to caries attack for the length of the restoration’s lifespan.14
According to Hatibovic-Kofman et al., the capability of F to influence remineralization under restoration is due to the ion acting as a catalyst and decreasing the activation energy necessary for crystal formation. In effect, the volume and electrostatic charge of the F permits a more favorable stereoscopic arrangement of calcium and phosphate on the surface of the crystal.12 It has been demonstrated that various inorganic exchanges occur between GIC and mineral teeth in addition to F. Moreover, it appears that these exchanges are also necessary to reinforce the enamel structure. Caries protection is enhanced by apatite formations that are more insoluble, such as strontium-apatite, fluorapatite, and hydroxy fluorapatite. Under acidic conditions, however, the glassionomer cement releases significantly higher ions, and the high release levels are retained. This mechanism is critical for caries prevention and lesion remineralization.15
Due to the synergistic impact of strontium (Sr) and fluorine (F), Handelman and Losee et al. observed that acid generation of Streptococcus mutans occurs at low levels, resulting in the decreased dissolution of synthetic hydroxyapatite. Thus, Sr and F ions possess anticariogenic capabilities, and the synergistic impact of F and Sr ions can enhance the remineralization process compared to F alone.16
It is widely known that GIC undergoes at least two reactions during the F elution cycle. The first cycle is a rapid, initial, short-term elution that ceases after some time. The second reaction is a long-term, extended, and slower elution cycle. The F burst produced from the glass particles during the setting reaction with polyalkenoate acid is likely the cause of the initial high release of glass ionomers that several researchers have observed. This release of F burst occurs within the first 24 hours after the reaction begins. Furthermore, according to Momoi and McCabe, the fastest F release occurred for both conventional and light activity during the first 7 days.17 The results of this study are consistent with Nantanee et al. in situ study in which remineralization of SDF and GIC was compared and found to increase the percentage of mean mineral density change of early proximal caries lesions but with different spatial patterns.18
Before applying GIC and SDF samples, deionized water was chosen as a medium; as it is devoid of ions, it is considered a more reliable medium than artificial saliva and other acidic media.19 Amaechi and Higham investigated the possibility of remineralizing an initial erosive lesion by human saliva in vitro. They found that artificial saliva and remineralizing solution promoted a more significant reparative effect on the erosive surface.20 After applying SDF and GIC, the teeth were submitted to a pH cycling model, which comprised exposing the specimen to alternating remineralization–demineralization solutions. Dental caries reflects a system of alternating demineralization and remineralization processes that are a direct function of conditions that maintain a critical pH in the mouth. Incorporating an occasional acid attack into such protocols may increase the sensitivity of in vitro demineralization and remineralization experiments.21
This study is probably the first to evaluate the remineralization potential of SDF and GIC on artificial enamel caries lesions in primary teeth using a microhardness test. While it requires more time and manipulation in the application procedure, adding a layer of glass ionomer gives an alternate treatment when SDF solution application is not acceptable due to the blackening of the arrested lesion.22
Within the study limitation, high remineralizing properties on incipient enamel caries in primary lesions have been shown by both SDF and GIC. In many children’s demographics, it will be of great importance to use simple caries-remineralizing therapy such as SDF for outreach community health services to reduce the prevalent dental caries problem. This is especially true where insufficient dental accessibility and esthetics are not significant issues.
Limitations of the Study
The tooth’s enamel surface needs to be polished before measuring the microhardness, which may influence the measurement of the baseline values. Remineralization of incipient enamel lesions was evaluated through a microhardness test, which may not measure the quality of remineralization.
CONCLUSION
This study evaluated the remineralizing potential of SDF and GIC on early enamel caries lesions using a microhardness test. Results of the study showed no significant difference in the microhardness of enamel lesions between SDF and GIC. The remineralizing potential of GIC is similar to SDF. Therefore, GIC can be recommended as an alternative to SDF in the anterior teeth to eliminate the disadvantage of black staining caused by SDF.
ORCID
Sahanai Sunny https://orcid.org/0000-0003-4769-7098
Sharan S Sargod https://orcid.org/0000-0002-0815-0252
Sham S Bhat https://orcid.org/0000-0002-5875-0141
Ajay Rao HT https://orcid.org/0000-0002-6725-529X
ACKNOWLEDGMENTS
My sincere gratitude to the Indian Council of Medical Research (ICMR) for funding this project.
FUNDING STATEMENT
The study had received grant from Indian Council of Medical Research (ICMR).
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