ORIGINAL RESEARCH

https://doi.org/10.5005/jp-journals-10005-2621
International Journal of Clinical Pediatric Dentistry
Volume 16 | Issue S-1 | Year 2023

Comparative Evaluation of Fluoride Release from Four Commercially Available Pediatric Dental Restorative Materials

Raviraj S Dhumal¹, Rashmi S Chauhan², Vishwas Patil³, Nilesh Rathi⁴ https://orcid.org/0000-0003-0595-5191, Krishnapriya Nene⁵, Sunny P Tirupathi⁶, Lalit Patil⁷, Meenakshi Y Nankar⁸ https://orcid.org/0000-0002-2924-4223, Ankita P Khandelwal⁹

^1-9Department of Pediatric and Preventive Dentistry, Dr. D. Y. Patil Dental College & Hospital, Dr. D. Y. Patil Vidyapeeth Pimpri, Pune, Maharashtra, India

Corresponding Author: Sunny Priyatham Tirupathi, Department of Pediatric and Preventive Dentistry, Dr. D. Y. Patil Dental College & Hospital, Dr. D. Y. Patil Vidyapeeth Pimpri, Pune, Maharashtra, India, e-mail: dr.priyatham@gmail.com

ABSTRACT

Objectives: The aim of this study was to evaluate the fluoride-releasing abilities of commercially available restorative materials such as—Activa™ BioActive-restorative™ material, Zirconomer (Shofu Inc), Beautifil^® II (Shofu Inc), GC Gold Label 9 high strength posterior restorative glass ionomer cement (GIC Corp).

Materials and methods: A total of 40 disk specimens (10 of each material) were placed into distilled/deionized (DI) water and the fluoride release was measured for 30 days. Fluoride ion measurement was performed at the end of the 1st, 3rd, 7th, 15th, and 30th day under normal atmospheric conditions by fluoride ion selective electrode (F-ISE) (Orion 9609 BNWP, Ionplus SureFlow fluoride electrode, Thermo Scientific, United States of America) coupled to a benchtop analyzer (Hachsen Ion+).

Results: All the materials included in the study exhibited fluoride release. Although there were differences in the amounts of fluoride released between Activa™, Zirconomer, and GC Gold Label 9 the mean difference between these three groups was not found to be statistically significant. Beautifil^® II showed low amounts of fluoride released at all time intervals.

Conclusion: Among the above-compared materials Activa™ and Zirconomer exhibit both improved mechanical properties as well as they have fluoride-releasing ability so can be preferred over conventional glass ionomer restorations.

How to cite this article: Dhumal RS, Chauhan RS, Patil V, et al. Comparative Evaluation of Fluoride Release from Four Commercially Available Pediatric Dental Restorative Materials. Int J Clin Pediatr Dent 2023;16(S-1):S6–S12.

Source of support: Nil

Conflict of interest: None

Keywords: Beautifil^®, BioActive-restorative, Zirconomer, Glass ionomer, Fluoride release, Restorations

INTRODUCTION

Dental caries has continued to be one of the most common chronic diseases globally.¹ Acidogenic bacteria play a vital role in the causation of dental carious lesions.¹ Dental caries is prevalent in all age-groups, demographic, and socioeconomic groups.² A form of dental caries known as early childhood caries (ECC) is very common in children and affects the pediatric population globally. ECC also has a deleterious effect on the general well-being and health of the child.² Another form of ECC is severe ECC, which affects younger age-groups of children under 3 years of age which in untreated cases may have more severe and detrimental effects.³ Dental restorative treatment is the mainstay of therapies to eliminate dental caries and is often an ideal reparative solution for restoring a tooth damaged by dental caries, to its optimal form and function. In order to lower the viability of redundant bacteria and also to promote the healing of the dental tissues, restorative materials possessing antimicrobial, and remineralizing properties are placed in direct contact with the residual dental tissues, thus preventing the occurrence of secondary caries.⁴ Studies have shown that the success of restorations is affected by the presence of residual traces of infection.⁵ As per the literature, secondary caries is the cause of approximately 60% of the total replacements of restorations.⁶

The anticarcinogenic effects of fluorides have been well documented.⁷ Fluoride that is released from dental restorative materials presumably inhibits caries formation and thus brings about reduction or prevention of the demineralization process, and enhances the remineralization.⁸ Fluoride is released from various restorative materials, the aim of the present study is to compare fluoride-releasing properties of newer restorative materials high strength glass ionomer posterior restorative material [(GC Gold Label 9), Zirconomer, Giomer, Activa BioActive-restorative] used in dentistry. Fluoride elution from various restorative materials is governed by different factors. But the more pertinent question would be “for how much duration these advantageous effects of fluoride ion release from the dental restorative materials be retained?” Taking into account the above-mentioned aspects, the current study intends to be undertaken to establish the fluoride ion release (pattern and amount) from four commercially available restorative materials at five different time intervals.

MATERIALS AND METHODS

This in vitro study was undertaken at the “Department of Pediatric and Preventive Dentistry, Dr. D. Y. Patil Dental College & Hospital, Pune, Maharashtra, India” and carried out in association with “Environmental Science Technology Study Center (Laboratory) of Bapuji Institute of Engineering & Technology, Davangere, Karnataka, India,” to assess the fluoride release of four different restorative materials used in pediatric dentistry: group I—Activa™ BioActive-restorative™ (Pulpdent) (Fig. 1); group II—Zirconomer (Shofu Inc.) (Fig. 2); group III—Beautifil II (Shofu Inc.) (Fig. 3); group IV—GC Gold Label 9 (GC Corp.) (Fig. 4). Sample size was determined manually using the experimental formula, hence the sample size required for the study is found to be 40 specimens (10 in each group). Around 40 specimens (10 of each restorative material) were analyzed for fluoride release using a fluoride ion selective electrode (F-ISE). The data obtained were tabulated and sent to a statistician for analysis. The data was measured with one-way analysis of variance (ANOVA), repeated measures ANOVA followed by a post hoc test. A p-value of <0.05 was considered to be significant.

Fig. 1: Activa™ Bioactive-restorative™ (Pulpdent®)—group I

Fig. 2: Zirconomer (Shofu Inc.)—group II

Fig. 3: Beautifil® II (Shofu Inc.)—group III

Fig. 4: GC Gold Label 9 high strength posterior restorative GIC (GC Corp.)—group IV

Specimen Preparation

Around 10 disk-shaped specimens were made (7 mm inner diameter × 2 mm in thickness) from each of the materials in the four groups using a polytetrafluoroethylene mold and suspended in a sterile bottle containing deionized (DI) water (20 mL) separately.⁹^,¹⁰ The containers were then placed in an incubator and were incubated at 37°C and stored for 24 hours (Figs 5 and 6).¹¹^,¹²

Fig. 5: Test materials and armamentarium for specimen preparation

Fig. 6: Dental floss incorporated in the disc specimens

Fluoride Ion Evaluation

Fluoride ion release was calculated at the end of the 1, 3, 7, 15, and 30th day under normal atmospheric conditions by the selective electrode (Orion 9609 BNWP, Ionplus Sure-Flow fluoride electrode, Thermo Scientific, United States of America) attached to an analyzer (Hachsen Ion+) (Fig. 7). The F-ISE was calibrated with 2.5, 5, and 10 parts per million (ppm) of fluoride solution. After 24 hours, each disk specimen was taken out from the bottle and the disk specimen was washed with 1 mL of DI water. Drying of the disks (absorbent paper) was followed by again submerging in fresh 20 mL of DI water. These disks after being transferred into a fresh medium were then again incubated at 37°C till the next testing. Around 20 mL of the previous solution from the polyethylene bottle and 1 mL of DI water used for washing the disk were mixed with an equal amount of total ionic strength adjustment buffer (TISAB II).¹³ This was then moved to the polyethylene container into which a magnetic stirrer was placed. Fluoride concentration was recorded in ppm by dipping the electrode (Fig. 8). TISAB II is used to decomplex the fluoride ions, to provide a constant background ionic strength, and to hold the pH of water between 5.0 and 5.5 as the fluoride ion selective electrode is sensitive to changes in pH.¹³ Similar steps were followed for the 1st, 3rd, 7, 15, and 30th day and the electrode.

Fig. 7: F-ISE connected to an ion-selective electrode meter

Fig. 8: Study sample being tested using F-ISE

RESULTS

Analysis of data revealed that there was a significant difference in fluoride release of the test materials at different time intervals. Mean fluoride release (in ppm), intragroup, and intergroup comparison is depicted in Table 1.

**Table 1:** Comparison of fluoride release values (mean with standard deviation) (ppm) of the four test groups at the specified time intervals (days 1, 3, 7, 15, and 30)
Time interval	Groups	N	Mean	Standard deviation	F	p–value
Day 1	Group I	10	3.6960	0.26175	79.918	<0.001
	Group II	10	3.7550	0.13352
	Group III	10	2.6540	0.16167
	Group IV	10	3.7260	0.17753
	Total	40	3.4578	0.50452
Day 3	Group I	10	3.5410	0.34336	52.488	<0.001
	Group II	10	3.6090	0.21242
	Group III	10	2.4610	0.18520
	Group IV	10	3.5740	0.19890
	Total	40	3.2962	0.54200
Day 7	Group I	10	2.1880	0.32751	26.877	<0.001
	Group II	10	2.0720	0.35207
	Group III	10	1.1890	0.17394
	Group IV	10	1.9170	0.19619
	Total	40	1.8415	0.47356
Day 15	Group I	10	1.8380	0.03967	61.820	<0.001
	Group II	10	1.7790	0.18953
	Group III	10	1.0900	0.20374
	Group IV	10	1.7700	0.04619
	Total	40	1.6192	0.33939
Day 30	Group I	10	1.5520	0.11970	48.998	<0.001
	Group II	10	1.5670	0.17030
	Group III	10	0.9500	0.15535
	Group IV	10	1.5590	0.09134
	Total	40	1.4070	0.29820

p < 0.001 significant

Intragroup Comparison

Intragroup comparison in all the groups showed maximum fluoride release (mean ± standard deviation) (ppm) on day 1 (3.6960, 3.7550, 2.6540, 3.7260, and 3.4578) and 3 (3.5410, 3.6090, 2.4610, 3.5740, and 3.2962), and 7 (2.1880, 2.0720, 1.1890, 1.9170, and 1.8415) followed by significant decline at day 15 (1.8380, 1.7790, 1.0900, 1.7700, and 1.6192), and day 30 (1.5520, 1.5670, 0.9500, 1.5590, and 1.4070) for group I–IV, respectively (p-value < 0.001).

Intergroup Comparison

Intragroup comparison of fluoride release values (ppm) of the four test groups at the specified time intervals (days 1, 3, 7, 15, and 30). The intergroup statistical analysis was performed using Bonferroni post hoc analysis. The intergroup comparison showed that all four test materials exhibited a similar fluoride release pattern with the highest fluoride being released on the 1st day followed by a decline in the amount of fluoride elution until the last time interval (Table 1). The pattern of fluoride release was as follows:

Day 1: Groups II > IV > I > III.
Day 3: Groups II > IV > I > III.
Day 7: Groups I > II > IV > III.
Day 15: Groups I > II > IV > III.
Day 30: Groups II > IV > I > III.

Though there were differences in the amounts of fluoride released between groups I, II, and IV, the mean difference between these three groups was not found to be statistically significant. Group III showed low amounts of fluoride release at all time intervals and the mean difference was statistically significant (p-value < 0.001) when compared with groups I, II, and IV.

DISCUSSION

Dental caries is considered to be a chronic disease with a high prevalence that affects humankind. It is a health issue of major concern since approximately 60–90% of school-aged children and a large part of the adult population are affected by the disease.¹⁴ Restoration of carious teeth is one of the primary treatment needs.¹⁵ The chief objective of contemporary dental treatment is not confined only to the restoration of the carious teeth but to make attempts at inducing changes in the dental hard tissues to enhance the resistance potential to initiation of caries process itself.¹⁰ However, several factors influence the longevity of dental restorations such as the type of materials used and the patient and dentist-related factors. Of all the factors described in the literature, secondary or recurrent caries has been quoted to be the commonest cause that results in the failure of dental restorations.¹⁶ This recurrent or secondary caries which is located at the restoration-tooth interface is considered to be a critical contributing factor for replacement of amalgam and composite restorations.¹⁷^,¹⁸ Even after the removal of carious dentin, the accumulation of microbes underneath the restoration can lead to undesirable events such as pulp injury and pulp necrosis, as a result of microleakage. and ingress of new microorganisms at the restoration-tooth interface. This results in the development of secondary caries, eventually leading to the failure of restoration.⁵ The anticarcinogenic effect of fluoride has been well documented. Various mechanisms including initiation of fluorapatite formation, which is less soluble compared to the initial carbonated apatite, interference with ionic bonding when pellicle and plaque are being formed, enhancing remineralization, and inhibiting the growth and metabolism of microorganisms, are all involved in imparting the anticarcinogenic property to fluorides.⁸^,¹⁹ The incorporation of fluoride in restorative materials can prove to be beneficial owing to the observed cariostatic effect of fluorides.²⁰^,²¹ There is evidence that recurrent caries is reduced in the proximity of fluoride-releasing dental restorative materials.¹⁸^,²² Dental restoratives that leach out fluoride have been shown to have an antibacterial effect²³^-²⁵ which potentiates prevention of secondary caries around restorations, causing lesser demineralization at the enamel and dentin restoration interfaces, when compared to nonfluoride releasing dental restorative materials.²⁶^,²⁷ Thus it is clear that the fluoride releasing property of dental restorative materials is imperative to bring about reduction in secondary caries formation and also to neutralize pH decrease, primarily in patients with high caries risk.

To some extent, glass-ionomer cements (GIC) represent a golden standard for the prevention of secondary carious lesions.²⁸ Precipitation of calcium complexes is facilitated by the fluoride ions at the restoration-tooth interface to demineralization.²⁸ However, glass ionomer restoratives possess certain limitations such as insufficient working time, prolonged setting time, desiccation after setting and susceptibility to early moisture and salivary contamination, poor esthetics, weak bond strength, compromised mechanical properties, and less esthetics. In order to overcome these shortcomings, hybrid materials were developed to conciliate the desirable fluoride-releasing properties of GIC in addition to better esthetic, mechanical, and biological properties. Manufacturers have attempted to incorporate fluoride into esthetic restorative materials in view of the consensus that fluoride when released in low and constant concentrations increases the remineralization, and reduces the demineralization of the dental enamel adjacent to the restoration, thereby preventing the initiation of secondary caries.²⁸ One such addition to the spectrum of hybridized restorative materials is the contemporary category of anhydrous restorative materials with a resin-based matrix which makes use of glass ionomer technology that is “prereacted.” In the current study, Beautifil II belonging to the class of Giomers introduced by Shofu Inc., Kyoto, Japan in the year 2000.²⁹ Zirconomer improved introduced by Shofu Inc., Kyoto, Japan was selected in this study as the test material because of the manufacturer’s claims about it being a combination of durability and strength that is comparable with that of amalgam and fluoride release similar to that of GIC.³⁰ It contains glass powder integrated with zirconium oxide particles, polyacrylates in the concentration of 20–50%, tartaric acid in a concentration of 1–10%, and the liquid component is composed of DI water. Activa Bioactive restorative by Pulpdent, Watertown, Massachusetts, United States of America is an enhanced resin-modified glass ionomer (RMGI) cement as it is composed of polyacid components of RMGIs and glass particles which undergo the usual acid-base setting reaction. Another terminology used for this material is “ionic resin-based composite” as it is also formulated with patented “bioactive ionic resilient resin matrix” having a dual cure.³¹ This renders the material with physical and chemical properties that mimic the natural tooth structures and fluoride release more than glass ionomers. Previous studies have used test mediums such as DI water, tap water, and real or artificial saliva, for pH-cycling models are used to estimate the quantity of fluoride released from dental materials. DI water was selected as the storage medium for the immersion of test specimens and fluoride analysis as it provides a baseline for the potential of fluoride release of the specimens in unstimulated conditions. Also, DI water is devoid of minerals or organic molecules, so it better reflects the fluoride release without confounding the influence of other organic molecules and ions, which might be present in artificial saliva and pH cycling solutions.³⁰^,³² A variety of intrinsic as well as extrinsic factors govern the fluoride elution from the dental restorative material. The intrinsic factors include—(1) material composition; (2) powder/liquid ratio; (3) mixing time; (4) temperature; (5) specimen geometry; (6) the contact area of the specimens with the storage medium; and (7) permeability. The extrinsic factors include—(1) the type of medium in which the specimens are stored; (2) the design of the study (volume of medium used for storage of specimens, periodicity of medium change, stirring); and (3) the method used for analysis.³¹^,³³ The difference in the matrix as well as the setting mechanisms of different restorative materials also influences the pattern of fluoride release from these materials.³² The difference in the matrices and setting mechanisms brings about differences in the pattern and amount of fluoride released in different restorative materials.⁸

In our study, all materials could release fluoride in the 30-day model. A comparison of the four test groups revealed that all the tested restorative materials except Beautifil II (group III) showed more release on the 1st day and a sharp decline in the release of fluoride after the 3rd day and thereafter decreased slowly to reach a low steady level on the 30th day (Table 1). This can be attributed to a phenomenon known as the “fluoride burst” effect.”¹⁴^,²⁰^,³⁴^,³⁵ Initial high level of fluoride release is caused by the “superficial rinsing effect” or the “surface wash off effect” or “cleaning effect” which is caused by contact of water or medium with the surface of the material.³⁶ Fluoride releasing ability of the restorative materials is diffusion limited and is influenced by the concentration of the particles as well as the cement matrix. During the early phase of acid dissolution from the surfaces of the powder particles, a substantial amount of fluoride becomes part of the reaction product matrix, which diffused quickly. This fluoride is then replaced gradually by the fluoride ions diffusing from the subsurface matrix. “Initial fluoride burst” is advantageous as it induces remineralization of enamel and dentin and also causes reduction of bacteria which may continue to remain viable in the inner carious part of the dentin whereas the sustained release of fluoride over time enhances the resistance of enamel and dentin to new carious lesions.³⁶^,³⁷ Fluoride release declined rapidly after 3rd day then decreased gradually from 7th to 15th and 15th to 30th day. This rapid decrease in the amount of released fluoride can be explained on the basis of the process in which the diffusion of fluoride ions occurs through the cement cracks and pores. After the initial fluoride burst effect, the second phase of the diffusion process from the bulk of the cement releases fluoride in small amounts at a more or less constant level into the surrounding medium over extended periods of time.¹⁰^,³⁸ This is exhibited by long periods of fluoride release from 7th to 15th day and 15th to 30th day at nearly constant levels, after immersion of the specimens into the medium (DI water). Thus after the 7th day, there was a gradual decline resulting in the slow release of fluoride ions from the specimens as the fluoride ions diffused through the bulk of the cement.

In this study, Beautiful II (Giomer) did not show the initial fluoride burst effect which was in accordance with previous studies by Mousavinasab and Meyers,³⁸ Gururaj et al.,²⁰ Bansal and Bansal,³⁹ Attar and Onen,⁴⁰ Yap et al.,⁴¹ and Beautiful II (Giomer) showed low amounts of controlled fluoride release. Beautifil II exhibits minimal or no glass ionomer matrix phase, as there is a deficit of a significant acid-base reaction. The fluoride component in Beautifil II is the prereacted glass ionomer (PRG). Water sorption results in the ionization of the acid groups and subsequent fluoride release from the acid-base reaction. Hydroxyethyl methacrylate (HEMA) is a hydrophilic resin that absorbs water slowly and brings about the diffusion of fluoride ions,³² However Giomers class of materials contain an anhydrous resin matrix in which the silanized fillers are incorporated. The HEMA in the resin matrix of these materials undergoes copolymerization with urethane dimethacrylate, which is more hydrophobic subsequently leading to lesser uptake of water than expected. Thus during the acid-base reaction, the crucial water sorption phase does not occur which is consistent with the results found in other studies Yap et al.,⁴¹ Tay et al.,⁴² Itota et al.,⁴³ and Forsten⁴⁴. Another factor influencing the fluoride release is the porosity of the material which affects the filler solubility. The porosity of Beautifil II is lower as compared to GIC. In addition to differences in the filler solubility, Giomers such as Beautiful II exhibit an increased barrier to the diffusion of fluoride and water due to the addition of resin contents to the material which increases the barrier through which water and fluoride can diffuse, so the fluoride release from Beautiful II was not as much as expected from GIC. As per the study results, this material showed low levels of controlled fluoride release throughout the study period. In this study, zirconomer improved showed the initial “fluoride burst effect” like glass ionomer restorative cement (Table 1) and this finding is in accordance with the previous studies conducted to determine the fluoride release of zirconomer by Kishore et al.,¹⁴ Tiwari et al..¹² At all-time intervals, zirconomer improved and showed higher fluoride release than GIC (GC Gold Label type 9 high strength posterior restorative glass ionomer cement) which is consistent with the previous studies. Higher amount of fluoride release from zirconomer improved may be attributed to its physical properties and chemical composition. Zirconomer involves the use of finely controlled micronization of the glass ionomer particles which results in optimum homogenous particle size that contributes to the major acid-base mechanism. Studies on particle size have shown that a larger surface area is provided by smaller glass particles, which increases acid-base reactivity.

Though there were differences in the fluoride release, the difference in the levels of fluoride release between Activa Bioactive (enhanced RMGIC) and GC Gold Label 9 high strength restorative GIC or zirconomer improved was not found to be statistically significant.

After the 1st week, the fluoride release from the four groups of test materials was low, and comparing the amounts of fluoride within the groups from 7th to 15th and 15th to 30th day there was no statistically significant difference between the values from 7th to 15th and 15th–30th day (Table 1), indicating that the fluoride elusion from the test specimens had reached a low steady state of fluoride elution. This gradual release and low steady state are exhibited by the material as a result of the equilibrium between leaching as a result of erosion from the bulk of the cement and diffusion of the fluoride ions that have already leached out from the matrix of the cement. This pattern of fluoride release is consistent with previous studies (Vermeersch et al.,⁴⁵ Garcez et al.,⁴⁶ and Upadhyay et al.⁴⁷).

Therefore, it can be concluded within the limitations of this study that, Beautifil-II (Giomer) released low sustained amounts of fluoride at all time points, with the difference being statistically significant when compared with the other three tested materials. Whereas, the zirconomer improved and Bioactive Activa restorative released fluoride in amounts comparable to that of GC Gold Label type 9 posterior high strength GIC. Also, both these materials (zirconomer improved and Bioactive Activa restorative) have better mechanical properties when compared to GICs. The smaller grain size of zirconia-filled GICs imparts the material with an exclusive characteristic called “transformation toughening” providing the restorative with higher strength and hardness, toughness and corrosion resistance, reinforcing the material with lasting durability and higher tolerance to occlusal load. Zirconia improved has been termed as “white amalgam” as it has been shown to exhibit the strength of amalgam and also retain the fluoride-releasing property of GICs.¹⁸ However, one drawback of the zirconomer family of restorative materials is that it is a powder and liquid system which requires manual mixing. Hand mixing can be a time-consuming step in clinical practice.⁴⁴

Limitations

The limitation of this research is the in vitro nature of the study. Since the oral environment is dynamic and different from laboratory conditions, there may be different challenges in the oral cavity. The release of fluoride ions is influenced by various factors such as the pH and composition of saliva and the formation of pellicles and plaque. Therefore, the findings of this study cannot be directly extrapolated to clinical conditions and further in vivo and in vitro studies are recommended in order to establish the clinical efficacy of these materials.

CONCLUSION

The study led to conclusions which were as follows—all the tested restorative materials except for Beautifil II (group III) showed the initial “fluoride burst effect.” After the initial fluoride burst effect, all the materials exhibited a decline in the amounts of fluoride released. From day 3 to 7 the materials showed a rapid decline in the levels of fluoride release whereas from day 7 to 15 and from day 15 to 30 the decline in the levels of fluoride release was gradual. From day 15 to 30, the fluoride release was nearly constant indicating the values reached a low steady state of fluoride release. The maximum amount of fluoride released on days 1 and 3 was shown by zirconomer improved (group II) followed by GC Gold Label 9 high strength restorative GIC (group IV) followed by Active Bioactive restorative (group I) whereas, on days 7 and 15, this pattern of fluoride release changed and the maximum fluoride release was shown by Active Bioactive restorative (group I), owing to its lower solubility and compact matrix, followed by zirconomer improved (group II) followed by GC Gold Label 9 high strength restorative GIC (group IV). Zirconomer improved (group II) showed more fluoride release than GC Gold Label 9 high-strength restorative GIC (group IV) at all time intervals. At all time intervals, lowest values of fluoride release were shown by Beautifil II Giomer (group III). On the last time interval (i.e., on the 30th day), the amounts of fluoride released by Active bioactive (group I), zirconomer improved (group II), and GC Gold Label 9 high strength restorative GIC (group IV) reached a low steady state and were equivalent with no statistically significant differences in their fluoride release.

ORCID

Nilesh Rathi https://orcid.org/0000-0003-0595-5191

Meenakshi Y Nankar https://orcid.org/0000-0002-2924-4223

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