Comparative evaluation of demineralizing resistance over deciduous teeth enamel using silver diamine fluoride and fluoride varnish

Arpita Dutta; Sonu Acharya; Susant Mohanty; Ankita Chandak; Dipmalla Sahoo; Sheetal Acharya

doi:10.4103/jioh.jioh_123_23

ORIGINAL RESEARCH

Year : 2023 | Volume : 15 | Issue : 5 | Page : 484-490

Comparative evaluation of demineralizing resistance over deciduous teeth enamel using silver diamine fluoride and fluoride varnish

Arpita Dutta¹, Sonu Acharya¹, Susant Mohanty¹, Ankita Chandak², Dipmalla Sahoo¹, Sheetal Acharya³
¹ Department of Paediatric and Preventive Dentistry, Institute of Dental Sciences, Siksha’O’Anusandhan (Deemed to be) University, Bhubaneswar, Odisha, India
² Department of Pediatric and Preventive Dentistry, HSRSM Dental College, Hingoli, Maharastra, India
³ Department of Periodontics and Oral Implantology, Kalinga Institute of Dental Sciences, KIIT University, Bhubaneswar, Odisha, India

Date of Submission	29-May-2023
Date of Decision	07-Oct-2023
Date of Acceptance	09-Oct-2023
Date of Web Publication	30-Oct-2023

Correspondence Address:
Dr. Sonu Acharya
Department of Paediatric and Preventive Dentistry, Institute of Dental Sciences, Siksha‘O’Anusandhan (Deemed to be University), Bhubaneswar 751003, Odisha
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jioh.jioh_123_23

Abstract

Aim: Dental caries pose a significant concern among pediatric populations and can substantially impact a child’s overall health. The application of topical fluoride in different forms has been an accurate strategy for combating decay on a global scale. The work done here aims to compare the outcomes of using topical fluoride therapy and silver diamine fluoride (SDF) on deciduous tooth enamel. Materials and Methods: A total of 60 nondecayed anterior deciduous teeth were collected from patients undergoing tooth extraction due to exfoliation or retained deciduous teeth. Following crown removal using diamond disks, the enamel samples were affixed to acrylic blocks, exposing the buccal (outer) surface. Baseline surface microhardness measurements were acquired for all enamel samples. The specimens were then randomly assigned to three groups, each comprising twenty samples: the control group (C) treated with distilled and deionized water, the fluoridated varnish group (V) treated with fluoride varnish, and the SDF group treated with SDF solution. Subsequent to exposure to pH-cycling solutions, microhardness measurements were taken again to evaluate changes in enamel hardness. Results: The group treated with fluoride varnish exhibited the highest mean enamel microhardness, measuring 251.80 ± 56.10. The SDF group displayed a mean enamel microhardness of 226.75 ± 60.25, while the control group (treated with distilled and deionized water) showcased the lowest mean enamel microhardness of 207.75 ± 35.19. Conclusion: In conclusion, this study determined that the fluoride varnish group demonstrated a more effective resistance to enamel demineralization compared to the SDF group. These findings suggest that topical fluoride therapy in the form of varnish is more successful in preventing dental caries in deciduous tooth enamel when compared to treatment with SDF.

Keywords: Demineralization resistance, silver diamine fluoride, sodium fluoride varnish, surface microhardness

How to cite this article:
Dutta A, Acharya S, Mohanty S, Chandak A, Sahoo D, Acharya S. Comparative evaluation of demineralizing resistance over deciduous teeth enamel using silver diamine fluoride and fluoride varnish. J Int Oral Health 2023;15:484-90

How to cite this URL:
Dutta A, Acharya S, Mohanty S, Chandak A, Sahoo D, Acharya S. Comparative evaluation of demineralizing resistance over deciduous teeth enamel using silver diamine fluoride and fluoride varnish. J Int Oral Health [serial online] 2023 [cited 2023 Dec 2];15:484-90. Available from: https://www.jioh.org/text.asp?2023/15/5/484/388784

Introduction

Dental caries is a nonreversible microbial ailment impacting the mineralized structures of the teeth. It is distinguished by the demineralization of the inorganic constituents and the deterioration of the organic components of the tooth. This condition frequently results in the formation of cavities. This process is well-documented in the literature^.[1]

Dental carious lesions typically originate in hidden areas of the teeth where bacterial materials, known as dental plaque, gather and develop as time progresses. These areas encompass on occlusal surfaces, indentations, furrows, and crevices, particularly while the erupting phase, as well as approximal surfaces situated below the joining points or areas and adjacent to the gumline. Importantly, these sites experience relative protection from the physical movements of the tongue, cheeks, rough-textured foods, and even tooth scrubbing.^[2],[3]

This foundational knowledge was notably emphasized by Black nearly a century ago, in 1914, when he postulated that the initiation of tooth decay takes place in locations that facilitate the retention and attachment of microorganisms. This hindrance to their frequent displacement thereby permits sustained growth. This concept elucidates the localized onset of caries in specific regions of the tooth surface, contributing to our understanding of the etiology and progression of the disease.^[4]

The American Academy of Pediatrics emphasizes the critical importance of addressing dental decay in deciduous dentition, highlighting its controllable and revertible nature when treated during its early stages. However, if left untreated, dental caries can lead to various complications, including pain, septicemia, and disruptions in the context of growth and development; the early loss of teeth can lead to several significant consequences, including talking disorders, elevated treatment expenses, reduced self-confidence, and adverse effects on the subsequent permanent teeth.^[5]

The term early childhood caries was introduced over 20 years ago during a workshop that received support from the Centers for Disease Control and Prevention. This terminology aims to bring attention to the multifaceted factors contributing to the development of cavities in these nascent years, encompassing factors that extend beyond the simple use of feeding bottles. These factors include financial, sociopsychological, and behavioral elements that collectively influence the onset of caries.^[6]

Methodology

A significant portion of this research investigation was carried out within the aegis of pediatric and preventive dentistry, while another essential aspect was undertaken at the Department of Biochemistry, Institute of Medical Sciences. The aims and objectives of the study were to contrast the outcomes of topical fluoride treatment and silver diamine fluoride (SDF) on deciduous tooth enamel, to estimate the resistance of deciduous enamel to demineralization utilizing a pH-cycling model, to assess the surface attributes of dentition by employing the microhardness test with the Vickers hardness method and to conduct a comparison of surface microhardness (SMH) among the three groups (SDF group, varnish group, control group) both before and after pH cycling.

Materials and Methods

Experimental design

The study samples were obtained from patients visiting our outpatient department. A total of 60 anterior deciduous teeth without any cavitations were collected, sectioned, meticulously cleaned, sterilized (stored in thymol under refrigeration for nearly a year before the study initiation), and subjected to a pH cycling model [Figure 1]. An in vitro study was conducted to know the “enamel surface micro-hardness” following fluoride therapy in children with more chance of decay. Children aged 6–13 were randomly chosen for this study. Sixty anterior primary teeth (incisors) were collected from cases scheduled for extraction of exfoliating and retained deciduous teeth (with prior informed consent). Teeth displaying any defects or stains visible under a “stereoscopic magnifying lens” and those collected from children under medications or with systemic diseases were excluded from the study.

Figure 1: Removal of roots and preparing tooth for pH cycling

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Materials

Fluoride Varnish (VOCO pro-fluoride varnish) (manufactured by VOCO, The Dentalists), silver diamine fluoride (e-SDF) (manufactured by Kids-e-dental LLP, Mumbai, Maharashtra), Surgical blade, 1% thymol, silicon carbide powder (200, 325, 600), glass slab, distilled/deionized water, demineralizing solution, remineralizing solution, absorbent paper, diamond disk, silk/velvet cloth (for final finishing and polishing), rough stone (for sectioning/polishing of tooth samples), microhardness tester (Vickers-Hardness tester) (manufactured by Fine Spavy Associates and Engineers Pvt. Ltd.), saline water.

Data collection

These teeth were gathered from patients after comprehensive treatment planning for primary teeth extraction of retained or exfoliating teeth, following voluntary agreement. The teeth were put in one percent thymol and kept.^[7] After removing the roots of the teeth using diamond disks, they were affixed to acrylic blocks to expose their buccal surface. Enamel blocks measuring four by four(mm) were obtained [Figure 2]. The top layer was then cleaned, and baseline SMH measurements were conducted utilizing a microhardness tester with a 25 g weight for 5 s [Figure 3]. Five depressions were created in the middle of the enamel surface.

Figure 2: Enamel blocks being prepared

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Figure 3: Surface microhardness testing

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The primary goals of the initial SMH assessment were to choose blocks within a comparable SMH range and to evaluate the alteration in SMH subsequent to pH cycling. Enamel specimens were arbitrarily distributed into three sets, each comprising 20 samples. A single set acted as the reference (treated with distilled and de-ionized water) (C), while the other sets received the administration of either a fluoride-infused coating (V) or an SDF solution onto the enamel pieces. Subsequently, all groups of blocks were exposed to pH-cycling solutions [Figure 4]. After the pH-cycling procedure, SMH measurements were once again recorded for all specimens.

Figure 4: pH cycling solutions

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Treatments and pH cycling

A thin coating of fluoride-infused varnish (5% NaF with a pH of 7.0) was gently brushed onto the enamel blocks in the V group. After 24 h, the varnish was meticulously eliminated using a surgical blade, ensuring complete removal with cotton swabs dipped in acetone. Subsequently, the blocks were rinsed with deionized water for a duration of 1 min.

For the SDF group, a cotton swab was employed to apply SDF (38% w/v) to the enamel blocks for approximately 2 min. Following the application, the blocks were rinsed with a stream of deionized water for about 30 s and gently dried with absorbent paper. All groups of blocks were then subjected to a pH-cycling model that simulated high caries challenge for approximately 30 days, largely following the method outlined by Amaechi et al.^[8]

The blocks were immersed in a demineralizing solution (comprising 2.2 mM calcium chloride, 2.2 mM potassium phosphate, and 0.05 M acetic acid; pH adjusted to 4.4 with 1 M sodium hydroxide) for 3 h and in a remineralizing solution (containing 1.5 mM calcium chloride, 0.9 mM sodium phosphate, 0.15 M potassium chloride, with a pH of 7.0) for 17 h. The demineralizing and remineralizing solutions were refreshed every 48 h and 5 days, respectively. These solutions are commonly employed in dental research to investigate dental caries and the impact of various treatments on the mineral content of tooth enamel. Below is the method used to prepare the demineralization and remineralization solutions for our study.^[9]

1. Demineralization solution: The demineralization solution is formulated to replicate the acidic conditions found in the mouth when bacteria produce acids that erode tooth enamel, creating artificial caries lesions for research purposes.
- • Ingredients:
  - • 2.2 g of calcium chloride dihydrate (CaCl₂·2H₂O).
  - • 2.2 g of sodium dihydrogen phosphate dihydrate (NaH₂PO₄·2H₂O).
  - • 0.05 M acetic acid (CH₃COOH) for pH adjustment (target pH around 4.5).
- • Instructions:
  - • Dissolve the calcium chloride and sodium dihydrogen phosphate in distilled water to create a solution.
  - • Gradually add acetic acid while stirring until the pH of the solution reaches approximately 4.5.
  - • The demineralization solution is now ready for use.
2. Remineralization solution: The remineralization solution is employed to facilitate the deposition of minerals back into the demineralized tooth enamel, emulating the natural remineralization process that occurs in saliva.
- • Ingredients:
  - • 1.5 mM calcium chloride dihydrate (CaCl₂·2H₂O).
  - • 0.9 mM disodium hydrogen phosphate (Na₂HPO₄).
  - • 0.15 M potassium chloride (KCl).
  - • 0.05 M acetate buffer for pH adjustment (target pH around 7.0).
- • Instructions:
  - • Dissolve calcium chloride, disodium hydrogen phosphate, and potassium chloride in distilled water to form a solution.
  - • Adjust the pH of the solution to around 7.0 using an acetate buffer.
  - • The remineralization solution is now ready for use.

The demineralizing and remineralizing solutions were refreshed every 48 h and 5 days, respectively. Following the conclusion of the pH-cycling procedure, all enamel samples underwent SMH assessment using a Vickers hardness tester.

Statistical analysis

The collected data underwent organization, coding, and analysis using the SPSS software (Statistical Package for Social Sciences) Version 24.0 (IBM Corporation, Chicago).

We performed both descriptive and analytical statistical analyses. We evaluated the data’s normality using the Shapiro–Wilk test. Since the data did not adhere to a normal distribution, we utilized non-parametric tests for our analysis. The Kruskal–Wallis test was utilized to examine differences in the means among the various groups. Post-hoc analysis was carried out using Dunn’s test.

Results

To evaluate the surface enamel attributes of the 60 deciduous incisors, they were subjected to a high caries risk simulated by the pH cycling study in the in-vitro procedure, and hence, the following results were obtained [Table 1], [Graph 1]. The enamel microhardness (H.V.-Vickers Hardness) before pH cycling among the three groups was compared. The analysis done by the Kruskal–Wallis test showed no significant differences (P = 0.87) in mean enamel microhardness (H.V.) before pH cycling among the three groups. However, the fluoride varnish group had the highest mean enamel micro-hardness (244.05 ± 57.41), followed by the SDF group (219.00 ± 60.20) and the control group (208.20 ± 37.96) [Table 1].

Table 1: Comparison of enamel microhardness (H.V.) before pH cycling among the three groups

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Graph 1: Comparison of enamel micro-hardness(HV)before and after pH cycling among the Three groups

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The enamel microhardness (H.V.) after pH cycling between the three groups was compared. The analysis done by the Kruskal–Wallis test showed statistically significant differences (P = 0.026) in mean enamel microhardness (H.V.) after pH cycling among the three groups. The fluoride varnish group had the highest mean enamel microhardness (251.80 ± 56.10), followed by the SDF group (226.75 ± 60.25) and the control group (207.75 ± 35.19) [Table 2].

Table 2: Comparison of enamel microhardness (H.V.) after pH cycling among the three groups

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The post-hoc pair-wise comparative analysis by Dunn’s test also showed significant differences in mean enamel microhardness (H.V.) after pH cycling among the three groups. When the control group was compared with the varnish group, a mean difference of 44.05 (95% CI -83.38 to -4.71) was found, which was statistically significant (P = 0.025). The comparisons between the control group and the SDF group (P = 0.415) and between the SDF group and the varnish group (P = 0.206) did not show significant differences [Table 3] and [Table 4], [Graph 1].

Table 3: Post hoc pairwise comparison of mean enamel microhardness (H.V.) after pH cycling among the three groups

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Table 4: Comparison of enamel microhardness (H.V.) before and after pH cycling among the three groups with post hoc pair-wise comparison

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Discussion

Numerous fluoride compounds have been shown to effectively mitigate and even arrest the progression of bacteria-induced caries within the oral cavity. In this study, we focused on evaluating and comparing the effectiveness of SDF and fluoride varnish (F.V.) in reducing enamel demineralization using a pH-cycling model, which simulates a highly cariogenic intraoral environment independently of a living organism.^[10]

Our study highlighted the fluoride varnish group as the more potent fluoride agent, exhibiting the highest mean Enamel Microhardness. This was followed by the SDF and control groups (treated with deionized water) under the pH cycling conditions. The varnish group emerged as the front runner in safeguarding teeth against aggressive caries incidents over the course of 1 month. The plausible factor behind this outcome may be the higher fluoride concentration present in the varnish compared to SDF. This facilitates enhanced absorption of fluoride ions onto the enamel surface layer, leading to the formation of calcium fluoride compounds in conjunction with salivary components. Subsequent to a decrease in pH, these ionic substances gradually release fluoride ions into the oral cavity.

SDF functions primarily through a combination of silver and fluoride, operating through three primary mechanisms. First, SDF creates a bacteria-impermeable substrate that obstructs peritubular and intertubular dentin, thus reducing enamel mineral depletion. Second, it seals off dentinal tubules, preventing the infiltration of cariogenic microbial organisms and the acids they generate. Lastly, SDF thwarts the enzymatic metabolism of bacterial cells, resulting in a bacteriostatic effect.

Parallel findings have been reported in other studies. Sorkhdini et al.^[11] concluded that potassium fluoride (K.F.) exhibited more effective resistance to enamel surface loss than SDF or SDF combined with K.F. Zhao et al.^[12] observed that sodium fluoride (NaF) yielded the shallowest lesion depth, while control groups and the SDF group exhibited greater lesion depths.

Ishiguro et al.^[13] demonstrated that applied fluoride on dentition hindered bacterial acid formation, while SDF displayed an overall inhibitory effect on cariogenic potential in root dentin. Weirichs et al.^[14] suggested that NaF combined with casein phosphopeptide-amorphous calcium phosphate demonstrated potential for reversing high cariogenic challenges compared to SDF. Yiu and Zhao^[15] found that NaF-containing polyethylene glycol with silver nanoparticles could reverse artificially induced dentinal caries while preserving tooth structure integrity. Ainoosah et al.^[16] noted that fluoride varnish caused less enamel surface loss compared to SDF, potassium fluoride, silver nitrate, and water groups^. Gao et al.^[17] conducted a systematic review indicating that the professional application of 5% NaF could reverse newly demineralized enamel lesions, while 38% SDF could arrest dentin lesions. Delbem et al.^[18] emphasized that fluoride expressed through varnish had a greater tendency to interact with unaffected enamel and induce less elemental loss compared to SDF.

While studies have highlighted differences between bovine and human enamel, the chemistry of these teeth implies similarities in mineral dissolution during demineralization or remineralization^.[19] Studies have shown slight disparities in microhardness and wear between deciduous bovine and human teeth under abrasive and erosive conditions.^{[20],[21],[22]}

Contrary to prior findings, Abdil-Nafaa et al.^[23] found that SDF outperformed varnish in stabilizing demineralization during a micro-hardness test on primary enamel. Ortega et al.^[24] examined the superficial resistance of enamel using three fluoridated substances, identifying SDF as the most promising, followed by diamine silver fluoride and acidulated phosphate fluoride during pH cycling^. Chu et al.^[25] conducted an in-situ experiment among preschool children and found SDF to be the most effective in preventing dentinal demineralization. Ahn et al.^[26] discovered that the effects of SDF lasted beyond a week, resulting in increased enamel hardness, rendering it preferable over varnish and control groups. Mohammadi et al.^[27] observed similar resistance to enamel surface loss between SDF and fluoride varnish in a pH-cycling model simulating high demineralization over a week.

In summary, both SDF and fluoride varnish demonstrate efficacy as fluoridating agents. This study’s distinct contribution lies in its chosen duration, an aspect that had not been extensively explored. A 30-day pH-cycling model has established fluoride varnish as a cost-effective and practical solution within a defined timeframe and under conditions of intraoral bacterial exposure. The focus on deciduous anterior teeth is pivotal, given their early eruption and heightened susceptibility to decay. Protecting these teeth lays a strong foundation for future preventive measures.

Conclusion

In alignment with recent findings, the efficacy of sodium fluoride in safeguarding the enamel layer’s SMH in deciduous anterior teeth has become particularly apparent. These results not only reinforce the limited mechanism of SDF but also underscore its superiority in this context. This study underscores the importance of delving further into research within the realm of extended fluoride functionality, as demonstrated by such fluoride agents.

Acknowledgements

The authors would like to convey immense gratitude toward Prof. (Dr.) Subhashree Ray also thank Dr. Ashish Jaiswal regarding the statistical support provided during the entire study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Author’s contribution

Conceptualization: SA; Data acquisition: AD and DS; Formal analysis: AD and SA; Funding: AD; Supervision: SM and SA; Writing—original draft: SA, AD, SM, AC, and DS; Writing—review and editing: SM, SA, AD, AC, and DS.

Ethical policy and institutional review board statement

Not applicable as In-Vitro study.

Patient declaration of consent

Not applicable.

Data availability statement

Data can be made available on request.

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