Silver Diamine Fluoride versus Bioactive Giomer Light-Curing Varnish: An In Vitro Study on Caries Arrest

ABSTRACT

Objective

To compare the capacity of silver diamine fluoride (30%) and the bioactive giomer light-curing varnish for arresting ICDAS score 5 non-retentive caries lesions.

Material and Methods

An in vitro analytical study was conducted using 36 healthy primary teeth, in which a cavity was created, divided into 3 groups: control (distilled and deionized water), giomer-based light-curing varnish – Barrier Coat, and Silver Diamine Fluoride 30% – Cariestop (SDF). The samples were analyzed for mineral loss as measured by surface microhardness (SMH).The Knoop microhardness test was performed using the HVS-1000 microhardness tester. The data were compared by two-way analysis of variance – treatment and time (before and after treatment) followed by Tukey’s post-test. The significance level adopted in all analyzes was 5%.

Results

The specimens treated with giomer showed higher SMH compared to the untreated group but were similar to those of the SDF group. The SDF group, on the other hand, showed no statistically significant difference from the control group (p=0.010).

Conclusion

The giomer varnish had a remineralizing effect on artificial dentinal caries.

Keywords:
Dental Caries; Fluorides; Mechanical Tests; Hardness Tests; Dentin

Introduction

Dental caries remains a global health problem and is considered one of the most common chronic diseases in the world [¹,²]. The most affected population is young children, and their cooperation during restorative procedures is not always satisfactory. Therefore, alternative, easy-to-perform, and cost-effective treatments are indicated to treat dental caries in children [³,⁴]. Recently, there has been a greater interest in non-invasive treatments, and studies show their comparable efficacy with conventional restorative methods [⁵,⁶].

The 30% Silver Diamine Fluoride (SDF) is a medication used for caries arrest, whose mechanism of action is based on its ability to increase enamel surface microhardness (SMH) and reduce mineral loss [¹]. More than 20 clinical studies conducted worldwide have demonstrated the effectiveness of SDF in arresting caries [³]. In a recent systematic review, 38% SDF was shown to be effective in arresting lesions in primary teeth, with an overall success rate of 81%, suggesting that this may be a promising strategy for treating caries in young children or in patients with special needs [²]. However, a disadvantage is that the arrested caries is discolored brown-black.

With advances in Pediatric Dentistry, new materials have been developed to prevent caries lesions. The giomer varnish has the advantage of being aesthetically pleasing. It consists of a light-curing varnish composed of a resin-based material incorporated with the surface pre-reacted glass-ionomer (S-PRG) technology. Its bioactive functions are due to the gradual release of multiple ions, including sodium (Na+), aluminum (Al3+), borate (Bo3-), silicate (SiO2-), fluorine (F-), and strontium (Sr2+). Therefore, this technology can be advantageous for dental materials that require the release of fluoride ions for demineralization inhibition [⁶–¹⁰].

No study has compared the capacity of SDF and giomer varnish for dentin caries control. Therefore, this study aimed to compare the caries arrest capacity of 30% SDF and giomer light-curing varnish.

Material and Methods

Ethical Aspects

This in vitro study was approved by the Research Ethics Committee (CEP) of São Leopoldo Mandic Faculty, report number 3,575,656. The teeth used had been collected and authorized by a biorepository letter from São Leopoldo Mandic Faculty. The research complied with the ethical guidelines of Resolution No. 466/12.

Sample

Healthy primary teeth (incisors, canines and molars) lost due to normal exfoliation or extracted due to orthodontic purposes or prolonged retention were selected, immersed in distilled water, and stored in a refrigerator until use. Teeth with caries, cracks, enamel developmental defects and extrinsic or intrinsic stains were excluded.

For sample size calculation, a mean hardness value of 158 was considered for 30% SDF-treated enamel after cariogenic challenge and a value of 121.8 for untreated enamel [¹¹]. With an effect size of 1.11, a significance level of 0.05, and a power of 0.80, a sample size of 12 specimens for each group was obtained, resulting in 36 specimens in total.

Teeth were cleaned with pumice stone and a Robinson brush at low rotation. Next, the roots were cut out with diamond disks (Microdont, São Paulo, SP, Brazil) and the tooth was fixed in a 1-inch high PVC tube with JET acrylic resin (Artigos Odontológicos Clássico, São Paulo, SP, Brazil). Then, the specimens were sanded with a 180 grit sandpaper until dentin exposure, and then the surface was polished with 600- and 1200-grit sandpapers.

Artificial Dental Caries Protocol

Specimens were subjected to cariogenic challenge by individual immersion in 10 mL of demineralizing solution (2.2 mM CaCl₂, 2.2 mM NaH₂PO₄, 0.05 M acetic acid adjusted to pH 4.8 with 1 M KOH) for 8 hours, followed by immersion in 10 mL of remineralizing solution (1.5 mM CaCl₂, 0.9 mM NaH₂PO₄ and 0.15 mM KCl adjusted to pH 7.0) for 16 hours; the cycle was repeated for 14 days. The solutions were changed after each cycle and at each interval, the teeth were washed with distilled water and dried with sterile absorbent paper [¹²].

Randomization

The teeth were randomly allocated to three experimental groups according to the sequence obtained by a statistical software (Sealed Envelope Ltd., London, UK). The sequence was stored in sealed envelopes, which were opened only at the time of specimen preparation.

Specimen Treatments

The control group was immersed in distilled and deionized water. For the SDF group, 30% SDF – Cariestop (Biodinâmica, Ibiporã, PR, Brazil) was applied with a cotton swab for 2 min. After application, the blocks were washed with deionized water for approximately 30 seconds and lightly dried with absorbent paper. For the giomer group, a thin layer of the giomer light-curing varnish – PRG-Barrier Coat (Shofu Inc., Kyoto, Japan) was applied following the manufacturer’s recommendations. The layer was light-cured with a LED unit for 10s, with a wavelength of 440-490 nm and an intensity of at least 1000 mw/cm². Then, the non-cured residual layer was removed gently with a cotton ball soaked in water.

Surface Microhardness Analysis (SMH)

The Knoop microhardness test was performed using the HVS-1000 microhardness tester (Pantec, São Paulo, SP, Brazil). Five indentations 100-μm equidistant from each other were performed on the dentin surface with a load of 5 g for 5 seconds [¹³]. The values for each sample were averaged and their mean was used for data analysis.Each specimen underwent 3 standardized tests performed by the same operator immediately after pH cycles and after 30 days of product application.

Statistical Analysis

The Kolmogorov-Smirnov test was used to verify the normality of the data distribution, and the Levene test was used to verify the homogeneity of the variances.The data were compared by two-way analysis of variance – treatment and time (before and after treatment) followed by Tukey’s post-test. The significance level adopted in all analyzes was 5%. Analyzes were performed using the SPSS v25 software (SPSS Inc., Chicago, IL, USA).

Results

Table 1 shows the means and standard deviations for Knoop microhardness (KHN) of experimental groups. A statistically significant difference was found only for the treatment factor (p=0.01). However, the interaction of treatment and time variables (p=0.547) was not significant. The giomer varnish-treated specimens showed higher SMH values compared to the untreated group, similar to the SDF group. On the other hand, the SDF group showed no significant difference from the control group.

Table 1.
Mean and standard deviation of Knoop hardness values (KHN) according to the experimental group.

Time-point	Treatment
	Giomer-Based Varnish	30%Silver Diamine Fluoride	Control
Immediately After pH Cycles	39.30 ± 9.07a.A	36.10 ± 9.95a.b.A	34.0 ± 8.37b.A
30 Days After Treatment	45.9 ± 11.12a.B	39.3 ± 7.31a.b.B	34.8 ± 8.18b.A

Different superscript lowercase letters indicate a significant difference among treatments regardless of the time-point (columns). Different superscript capital letters indicate a significant difference between time-points for each treatment (lines).

Discussion

The giomer-based varnish and the 30% SDF increased the microhardness values compared to the control group in non-retentive ICDAS 5 caries, suggesting tissue remineralization, and showed to be effective for caries arrest. The microhardness of the SDF group was higher than the control group but not statistically different. The microhardness of the giomer group was significantly higher than the SDF, thus indicating a higher remineralizing effect.

Although SDF at 30% is known to be effective for early childhood caries control, used especially in less cooperative children [¹⁴], its clinical use is limited by adverse effects, such as caries discoloration, which may affect aesthetically demanding patients [¹⁵,¹⁶]. The giomer varnish was shown to be as equally effective as SDF in increasing the microhardness of the tissue without causing discoloration.

According to the manufacturer, the giomer varnish protects the dental tissue from external irritants for over 6 months, releases and recharges fluoride ions, has self-adhesive properties that allow the application of a thin layer to any surface with good esthetic results (15 μm), and has an acid-neutralizing and anti-plaque effect. One of its many indications is for enamel white spots. Although not yet officially indicated for caries arrest, this in vitro study proved that it might control dentin caries and remineralize the tissue. This is probably due to the fluoride release and acid buffering properties of the material. However, the mechanism of action of this material in arresting dentin caries remains unclear. It is known that the hardness of the varnish layer can influence and mask the dentin remineralization results, but the samples were immersed in artificial saliva for 30 days after product application without retention of the material in the second hardness measurement. Therefore, the authors believe that the substance did not affect the dentin hardness measurements.

On the other hand, 30% SDF prevents and controls caries in primary and permanent teeth [¹⁷,¹⁸] by inhibiting plaque formation and decreasing the acid production by bacteria. The silver ions in SDF alter hydrogen bonding, inhibiting respiratory processes, cell wall synthesis, and cell division. In addition, SDF increases enamel resistance by reacting with the mineral component of the tooth, forming fluorapatite and obliterates dentinal tubules blocking the diffusion of acids and bacteria [¹⁹–²⁴]. The application of the product is non-invasive, cost-effective, and easy-to-perform. SDF has also been shown in laboratory studies to increase dentin resistance to demineralization [²⁵]. The use of SDF can be an effective treatment option in public healthcare services, where often treatment options are limited [²⁶].

Our results suggest that the giomer varnish may be a better anticaries agent for superficial, non-retentive lesions on anterior teeth because it resulted in higher dentine hardness than both the control group to the SDF group, and the color of remineralized tissue remains unchanged.

In vitro studies provide ideal control of the conditions and variables that could affect the results and high precision in measuring the relationships between variables [²⁷]. However, their major limitation is the extrapolation of results to humans, as clinical conditions, such as oral microbiota, presence of saliva, and contact with food and microorganisms, cannot be reproduced. Although microhardness is not the gold standard for measuring remineralization, it is widely used because it reflects mineral gain or loss, which can be extrapolated to demineralization or remineralization of substrates. Another limitation of this study was the relatively short observation period. A longer follow-up could be more representative of a clinical situation.

The silver nanoparticles in SDF have strong antibacterial and anti-biofilm properties, providing effective and long-lasting protection against bacteria [²⁸,²⁹]. However, the mechanism of caries arrest by the giomer varnish is unclear, and further studies should be conducted to evaluate this mechanism of action and assess the acceptability and cost of this material compared to other treatments.

Conclusion

The giomer-based light-cured varnish had a remineralizing effect on experimental dentinal caries.

• Data Availability
  The data used to support the findings of this study can be made available upon request to the corresponding author.

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Edited by

Academic Editor: Alidianne Fábia Cabral Cavalcanti

Publication Dates

• Publication in this collection
  06 Dec 2021
• Date of issue
  2021

History

• Received
  29 Oct 2020
• Reviewed
  21 May 2021
• Accepted
  10 June 2021