Journal of International Oral Health

: 2022  |  Volume : 14  |  Issue : 6  |  Page : 629--635

Assessment of microtensile bond strength of silver diamine fluoride with potassium iodide–treated carious primary dentin restored with glass ionomer cement and/or composite: In vitro study

Zaineb M F Haradwala, JJ Winnier, Arwa M Soni, Ishani Ratnaparkhi, Heer Kadhi 
 Pediatric and Preventive Dentistry, D.Y. Patil University, School of Dentistry, Nerul, Navi Mumbai, Maharashtra, India

Correspondence Address:
Dr. J J Winnier
Pediatric and Preventive Dentistry, D.Y. Patil University, School of Dentistry, Nerul, Navi Mumbai, Maharashtra


Aim: Silver diamine fluoride (SDF) followed by potassium iodide (KI) application helps minimize discoloration; however, such an application may interfere with the bond strength of the restorative material. The aim was to assess the microtensile bond strength (mTBS) of SDF with KI–treated carious primary dentin, which were restored immediately or on the seventh day with glass ionomer cement (GIC) and/or composite resin. Materials and Methods: Thirty-six carious primary molars were collected, and gross debris was removed. Prior to the placement of the restoration, SDF/KI was applied to all the specimens and divided randomly into group I: immediate placement of restoration, and group II: seventh-day placement of restoration (n = 18, per group). Group I was further divided into group Ia: GIC was placed immediately, and group Ib: composite resin was placed. Group II was divided into group IIa: GIC placed on the seventh day, and group IIb: composite placed on the seventh day (n = 9, per group). The specimens were then stored in artificial saliva at 37°C. After 7 days, the specimens were sliced for microtensile strength test using a slow-speed diamond saw (Isomet 1000). The failure mode was evaluated with stereomicroscope at 40× magnification. Results: The mTBS was compared using Kruskal–Wallis test. Group Ib (immediate composite) showed the highest bond strength (1.71 ± 0.80) though this difference was not statistically significant (P = 0.88). The failure modes were compared using chi-square test, which showed no statistically significant difference between the groups. Conclusion: The mTBS showed no difference with the time of placement between the materials.

How to cite this article:
Haradwala ZM, Winnier J J, Soni AM, Ratnaparkhi I, Kadhi H. Assessment of microtensile bond strength of silver diamine fluoride with potassium iodide–treated carious primary dentin restored with glass ionomer cement and/or composite: In vitro study.J Int Oral Health 2022;14:629-635

How to cite this URL:
Haradwala ZM, Winnier J J, Soni AM, Ratnaparkhi I, Kadhi H. Assessment of microtensile bond strength of silver diamine fluoride with potassium iodide–treated carious primary dentin restored with glass ionomer cement and/or composite: In vitro study. J Int Oral Health [serial online] 2022 [cited 2023 Apr 1 ];14:629-635
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In the late 18th century, the traditional management of carious lesion dictated the removal of infected and affected dentin to prevent further cariogenic activity.[1] Later, in 1960s, researchers proposed an alternative approach where only the infected dentin was removed prior to the restoration.[2],[3] In 2000, studies evaluated partial caries removal and suggested that it is preferable for deep carious lesions.[4] The advantage of partial caries removal is two-fold. In addition to preserving tooth structure, it may also help in limiting negative behavioral issues and enhance patient cooperation.

In this current scenario, the use of silver diamine fluoride (SDF) is considered as a novel pharmacological approach to combat and arrest the progression of dental caries.[5] In recent years, SDF has been advocated because of its economic benefits and the ease of use for children.[6] SDF (38% w/v Ag(NH3)2F) is a colorless liquid that contains approximately 24%–28% (weight/volume) silver and 5%–6% (weight/volume) fluoride.[7] However, SDF-treated areas turn dark because of the oxidation of silver ions leading to black staining, which limits it use. For SDF to be acceptable on a wider scale, the use of potassium iodide (KI) was proposed.[8] KI is applied immediately to SDF-treated tooth structure, which reacts with the remaining free silver ions to produce silver iodide, a creamy white reaction product, which after adequate application turns colorless.[9]

However, the application of SDF/KI may affect the bond strength of restorative material such as glass ionomer cement (GIC) or composite. Previous studies conducted in permanent teeth have shown that the application of SDF/KI does not affect the bond strength with GIC.[8],[10] However, conflicting results are obtained with composite resin.[11],[12],[13] It has also been suggested that the placement of GIC after 7 days may improve the bond strength.[14] Studies evaluating SDF/KI in the primary teeth are limited.[15] A systematic review in 2020 reported that the available evidence is inconclusive with regard to the application of SDF/KI on the bond strength.[7]

Against this background, the present study was conducted to (1) evaluate the microtensile bond strength (mTBS) between the immediate and 7-day placement of glass ionomer, (2) evaluate the mTBS between immediate and 7-day placement of composite resin, and (3) evaluate the failed interfaces. The null hypothesis was that there was no significant difference between any of the groups.

 Materials and Methods

This in vitro study was conducted in the Department of Pediatric and Preventive Dentistry, D.Y. Patil University, School of Dentistry, Nerul, Navi Mumbai. It was reviewed and approved by Institutional Ethical Committee of D.Y. Patil University (FRC/2021/PEDO/05). The study was conducted between March 2021 and July 2021. This laboratory study considered the time of placement of different materials to restore teeth after the application of SDF/KI.

Eligibility criteria

Thirty-six extracted carious primary molars having dentinal caries without pulpal involvement, International Caries Detection and Assessment II Score of 5 (ICDAS II), and carious primary teeth about to exfoliate were collected. Primary teeth with the presence of fracture lines, wear defects or crack, and pulpal involvement were excluded (ICDAS II score 6).

Sample size calculation

The sample size was calculated using the following formula:


It was calculated at 5% level of significance and 90% power, assuming that the difference to be tested relative to the standard deviation of the mTBS is 3.8.[14] The sample size was calculated as five in each group. To accommodate for pretest failures, the samples allocated per group were nine. The randomization was carried out using


Thirty-six carious primary molars were collected and stored in 0.1% thymol solution for a maximum period of 2 months before the start of the study. Gross debris was removed with a sharp spoon excavator.

Application of silver diamine fluoride with potassium iodide and restorations

All the specimens were treated with 38% SDF with KI (Riva Star, Australia) [Table 1] and [Appendix table]. SDF solution was applied topically to the carious lesion with immediate application of KI solution, until creamy white precipitate turned clear. These treated surfaces were then washed with distilled water using a syringe for 30 s and air-dried. Following this, the specimens were allocated either to group I—immediate restoration (n = 18) or group II—7-day restoration group (n = 18). The specimens in the 7-day group were stored in artificial saliva (KCl, NaCl, CaCl2·2H2O, NaH2PO4·2H2O, Na2S·9H2O, and 1 g urea) at 37°C to prevent any dehydration changes in the dentin material that could affect the bond strength.{Table 1} {Table 3}

The specimens in group I were further divided into group Ia—restored with conventional GIC (n = 9), and group Ib—restored with composite resin (n = 9). In group Ia, GIC (Fuji IX, GC, Gold, India) was mixed according to manufacturer instruction and a 4-mm thick build-up was carried out. This was done with the help of a clear tape wrapped around the specimen as a temporary mold. In group Ib, composite resin was placed, and etching (Solo etch, Medicept Dental, United Kingdom) was done with 37% phosphoric acid for 20 s. The gel was removed with vigorous distilled water spray for 15 s; excess water was removed with a soft blow of air to avoid desiccating the dentin. Bonding agent (Single Bond Universal Adhesive, 3M Espe, USA) was applied with a fresh applicator tip on to the surface. The surface was then light-cured for 15 s with a light cure unit (Being Tulip, LED Dental Light Cure Unit, 420–480 nm, Being Foshan). The composite (3M Filtek, Universal Restorative, USA) build-up was done incrementally with the help of a composite instrument. The material was light cured as and when the increment (1.5–2 mm thickness) was placed.

The group II was also similarly divided into group IIa—GIC placement, and group IIb—composite placement. Similar procedures were carried out after 7 days for the 18 specimens previously stored in artificial saliva [Figure 1].{Figure 1}

Bond strength test

Specimens embedded in cold cure acrylic resin using Teflon molds to facilitate sectioning at slow speed using the diamond saw (Isomet 1000, Buehler Ltd., Chennai, Tamil Nadu). Sectioning was done in the horizontal direction through the restoration to obtain slabs of 1.5 × 1.5 mm thickness. The width and thickness of each specimen were measured with vernier caliper. Only one slab could be obtained per specimen because the remaining tooth structure was too fragile.

These specimens were then tested for mTBS. The specimens were secured to the jig of the universal testing machine and tested for tensile strength until failure [Figure 2]. The tensile load at failure was divided by the cross-sectional area of the bonded interface to determine tensile bond strength [Figure 3]. This was then recorded and converted to megapascal for measuring of mTBS.{Figure 2} {Figure 3}

Failure evaluation

The surfaces were then evaluated under 40× magnification using stereomicroscope and classified into adhesive or mixed failure [Figure 4] and [Figure 5]. All data were subjected to statistical analysis to compare and evaluate the bond strength and failure interface.{Figure 4} {Figure 5}

Statistical analysis

All data were analyzed using IBM SPSS statistics 20.0 (IBM Corporation). Descriptive data were obtained, and Shapiro–Wilk test was used for testing the normality of the data. Nonparametric Kruskal–Wallis test was used for the comparison of mTBS values between the groups. The mode of failure was analyzed using the chi-square test. The level of significance was fixed at P = 0.05, and any value less than or equal to 0.05 was considered to be statistically significant.


Microtensile bond strength assessment

Intragroup comparison of group I using Kruskal–Wallis test revealed that the bond strength with group Ib (1.71 ± 0.80) was higher than group Ia (1.37 ± 0.46) although this difference was not statistically significant (P = 0.88).

Intragroup comparison of group II using Kruskal–Wallis test indicated that the bond strength with group IIa (1.88 ± 1.56) was higher than group IIb (1.33 ± 0.79). On further assessment, it revealed a median of 1.20, which was similar for both the groups, and it showed no statistically significant difference (P = 0.88).

Intergroup comparison of groups I and II revealed a higher bond strength with group Ib, but this difference was not statistically significant using Kruskal–Wallis test (P = 0.88) [Table 1].

Failure mode

The failure rates among all the groups were analyzed using chi-square test, which revealed no statistically significant difference between the groups [Graph 1].{Figure 6}

[Figure 4] shows adhesive failure under stereomicroscope at 40× magnification where most of the dentin surface is exposed. [Figure 5] shows mixed failure under stereomicroscope at 40× magnification where some material is adherent to dentin surface, and the dentin is partially denuded.


The principal objective of this study was to assess the mTBS of glass ionomer and/or composite restoration after the application of SDF/KI, which was restored immediately or on the seventh day. In the present study, the collected teeth were stored in 0.1% thymol solution for up to 2 months. Previous studies have indicated that the storage of teeth for up to 6 months in thymol solution does not affect the microhardness of enamel and dentin.[16],[17] Only gross debris was removed, and complete caries removal was not carried out in this study because it has been reported that carious tissue excavation has shown to have no beneficial effect.[18]

SDF/KI was applied on all the specimens, and the white precipitate formed after KI application was washed away using distilled water. Knight et al. (2006) recommended that the white precipitate should be washed because it may interfere and decrease the bond strength between the restorative material and dentin.[8] Thereby, in this study, the precipitate was washed away using distilled water for 30 s.

{Table 2}

After the placement of restorative material, the specimens were sliced using a slow-speed diamond saw (microtome-Isomet 1000). Diamond saw was preferred in comparison to vibratory microtome because of its ability to slice to precision.[19] The specimens obtained in this study were 1.5 mm in thickness for mTBS test, which was evaluated using universal testing machine. mTBS was preferred in comparisons to microshear bond strength as it considered to be more reliable in reflecting the interfacial bond strength offering more uniform stress distribution.[7]

This study found no statistically significant difference in bond strength after the application of SDF/KI with respect to time of the placement or the type of restorative material. However, it was seen that immediate placement of the restorations resulted in a higher bond strength. It is possible that, when the reaction product is immediately washed away, they are easier to remove and do not interfere with the bond strength of the material to the dentin. Therefore, the seventh-day placement of GIC and composite resin resulted in lower bond strength as compared to immediate placement.

It was also noted that the immediate placement of composite resin had higher bond strength in comparison to glass ionomer placement, although this was not statistically significant. It has been suggested that this could be due to the action of phosphoric acid, which helps remove the white precipitate leading to a better biomechanical adhesion of the restorative material.[12]

This study analyzed the adhesive–tooth interface using a stereomicroscope at 40× magnification. Adhesive and mixed failures were included. Cohesive failure was not evaluated as it does not represent the true interfacial bond strength, but rather the mechanical properties of the substrate.[7] It was seen in the current study that there was no statistically significant difference between adhesive or mixed failures in any of the groups.

Though statistically no significant result is obtained in our study, it is seen that immediate composite leads to higher bond strength. Further studies with increasing sample size would help determine the best application protocol. No study has compared the bond strength of primary carious dentin after SDF/KI application with respect to restoration and time placement to draw a comparison.

This study used conventional GIC and not resin-modified GIC, which could have resulted in improved bond strength. It would also be interesting to note the degree of discoloration seen over a period of time post the placement of restoration. Further work is needed on this finding.


Based on the study’s result, it can be concluded that the bond strength after the application of SDF/KI and immediate placement of composite resin results in higher bond strength.


Not applicable.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

Authors contributions

ZMFH: conceptualization, methodology, validation, formal analysis, investigation, data curation, and writing original draft; JJW: conceptualization, methodology, writing, review and editing, supervision, project administration; AMS: formal analysis, investigation, data curation; IR: investigation, writing–editing, data curation; and HK: conceptualization, formal analysis, investigation. All authors have made substantial contributions to this study and all have reviewed the final article prior to its submission. Finally, all authors have given approval for publication.

Ethical policy and institutional review board statement

All procedures were in accordance with the ethical standards of Research Ethics Committee of D.Y. Patil University, School of Dentistry, with ethical approval number IREB/2021/PEDO/05.

Patient declaration of consent

Not applicable.

Data availability statement

Data is available on reasonable request.


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