Evaluation of caries arresting potential of silver diamine fluoride and sodium fluoride varnish in primary molars

A randomized controlled trial

Abstract

Background: 

Caries management in the modern era has shifted away from the traditional surgical method toward a medical paradigm, which often includes fluoride therapy. Fluoride used in various forms has been proven to be effective in dental caries prevention. Silver diamine fluoride (SDF) and sodium fluoride (NaF) varnish are effective in arresting caries in primary molars.

Aim: 

This study aimed to evaluate the effectiveness of 38% SDF and 5% NaF varnish in arresting caries in primary molars.

Settings and Design: 

This study was a split-mouth randomized controlled trial.

Materials and Methods: 

The randomized controlled trial comprised 34 children aged 6–9 years with teeth having caries in both right and left primary molars without pulpal involvement. Teeth were randomly allocated into two groups. In Group 1 (n = 34), 38% SDF + potassium iodide was applied and in Group 2 (n = 34), 5% NaF varnish was applied. The second application was done after 6 months in both groups. Children were recalled at 6- and 12-month intervals and evaluated for caries arrest.

Statistical Analysis: 

Chi-square test was used to analyze the data.

Results: 

Caries arresting potential was found to be higher in the SDF group compared to the NaF varnish group at both 6-month (SDF – 82% and NaF varnish – 45%) and 12-month intervals (SDF – 77% and NaF varnish – 42%) and the difference was found to be statistically significant (P = 0.002 and 0.004, respectively).

Conclusion: 

SDF was more effective in arresting dental caries in primary molars compared to 5% NaF varnish.

Introduction

Dental caries is considered one of the public health challenges to date. Approaches to arresting dental caries have been a matter of interest for more than two decades. A better understanding of the caries process has led to the shift of concept from surgical intervention to prevention with minimal intervention using caries arresting agents. Silver diamine fluoride (SDF), nanosilver fluorides, fluoride varnish, sealants, and arginine are examples of materials that have cariostatic qualities by lowering the bacterial load.[¹]

In 1940, fluoride was introduced into clinical dentistry to combat dental caries. Sodium fluoride varnish (NaF), by promoting remineralization and inhibiting demineralization, is found useful in limiting caries progression. Studies have shown that the use of fluoride varnishes is effective in the prevention of early childhood caries and reduce caries by 25%–45%.[^2,3]

SDF was approved by the Food and Drug Administration of the United States in 2014. Since then, there has been growing interest in its “off-label” use for arresting carious lesions in children.[⁴] There is a multitude of benefits with SDF in caries management. It is cost-effective, non-aerosol generating and does not require any dental equipment.

Literature evidences have shown that SDF has been effectively arresting cavitated carious lesions.[^5-7] However, its main disadvantage is discoloration.[⁷] Topical fluorides such as fluoride varnishes are widely used in dentistry to remineralize early enamel lesions without causing any discoloration. However, the ability of these topical fluorides to arrest cavitated lesions needs to be evaluated. Hence, the present study was conducted to evaluate and compare caries arresting potential of semiannual application of 38% SDF and 5% NaF varnish in primary molars. Null hypothesis of the study is there was no difference in the effectiveness of 38% SDF and 5% NaF varnish in arresting caries of primary molars.

Materials and Methods

The study design was approved by the Institutional Review Board and Ethical Committee and it was in accordance with the ethical standards laid down by the Helsinki Declaration. The study was registered with the Clinical Trials Registry of India (CTRI/2020/20/031361). The study has been carried out in schoolchildren of lower socioeconomic status who were brought to the outpatient department of pediatric dentistry as a part of a school dental health program. The children were screened and those who met the inclusion criteria were considered for the study. Before the start of the study, permission was obtained from the respective school authorities and parental consent was obtained through school headmasters after explaining the background of the study and its protocol.

The study is a double-blinded, randomized controlled trial with a split-mouth design consisting of 34 children with 68 cavitated carious primary molars. Cooperative children of age 6–9 years with occlusal caries of ICDAS II code 5 involving both right and left upper or lower primary molar teeth without any pulpal involvement and willing to participate in the study were included. Children were selected after examination of the carious lesion with CPITN probe, and the confirmation of lesion depth with intraoral periapical radiograph where the teeth with radiolucency limited to outer one-third of dentin, i.e., ICDAS/International Caries Classification and Management System™ radiographic scoring system code RA3[⁸] with no periapical pathology were included. Children who are medically compromised, allergic to silver, and participating in any other studies were excluded.

The sample size was calculated based on the results of the previous study[⁵] using the G power software version 3.1.9.7 (Heinrich-Heine-Universitat Dusseldorf, Dusseldorf, North Rhine-Westphalia, Germany). At a level of significance set at 5%, the power of the study at 80%, and for an expected critical Z value of 3.193, it was calculated that 48 teeth, i.e., 24 teeth per group were required to perform the study. Finally, a sample size of 34 teeth was taken in each group assuming a 40% of loss to follow-up.

Selected 68 primary molars (36 lower molars and 32 upper molars) were randomly allocated to two groups: Group 1–38% SDF (control group) and Group 2–5% NaF varnish (test group). With computer-generated block randomization of block sizes 2 and 4, a randomization sequence was generated using Excel, 2007 by an independent operator. The selected teeth were cleaned using rubber cup and nonfluoridated pumice powder which were then washed and dried for 5 s. Isolation was done using cotton rolls. Application of SDF and NaF varnish was done on each carious mandibular primary molar in contralateral quadrants in the same patient at the first visit and after 6 months. All the clinical procedures were carried out by a single operator.

In Group 1, vaseline was applied around the tooth and gingiva to avoid SDF staining. Then SDF (Riva Star, SDI Inc., Australia) was coated over the cavitated lesion using a micro applicator tip and waited for 20–30 s, followed by the application of potassium iodide (KI) (Riva star, SDI Inc., Australia) with micro applicator tip. Then, the formed precipitate was cleaned using a moistened cotton pellet. Whereas in Group 2, topical NaF varnish (Embrace Varnish, Pulpdent, USA) was applied using the micro applicator tip and was allowed to dry for 1 min. The patient was advised not to drink or eat for 30 min, and oral hygiene instructions were given. The children were recalled at 6- and 12-month intervals and evaluated for caries arrest by two-blinded evaluators.

In the recall visits, if the cavity wall or floor was easily penetrated by the CPITN probe using light force, it was diagnosed with active caries.[⁵] Cavities with hard surfaces were classified as arrested caries. Two clinicians were trained to evaluate caries and interexaminer variability was checked to avoid bias. The interexaminer reliability values were 0.904 and 0.832 for the SDF group and 0.693 and 0.934 for the NaF varnish group. The agreement between the examiners was observed to be substantial to almost perfect.

The obtained data were analyzed using the Chi-square test. Data analyst has been blinded to the sample distribution. A probability value of ≤ 0.05 was considered for statistical significance.

Results

Participation of children through the study is depicted in the CONSORT flow diagram [Figure 1]. The study was carried out from October 2020 to January 2022. There was one loss of follow-up at 6 month interval and 3 loss of follow-ups at 12 month interval.

Figure 1: CONSORT flow diagram

On intragroup comparison of caries arresting potential at 6- and 12-month intervals, the difference was found to be statistically not significant in both SDF (P = 0.662) and NaF varnish (P = 0.777) groups, suggesting that caries arresting potential of both the materials was almost similar at 6- and 12-month intervals [Table 1].

Table 1: Intragroup comparison of the effectiveness of silver diamine fluoride and sodium fluoride varnish in arresting carious lesions at two different time intervals

On intergroup comparison, at 6-month intervals, caries arresting potential was found to be higher for SDF (82%) compared to NaF varnish (45%) and the difference was found to be statistically significant (P = 0.002). Similarly, at 12-month intervals also, SDF (77.4%) showed superior performance compared to NaF varnish (41.9%) with a statistically significant difference (P = 0.004) [Table 2].

Table 2: Intergroup comparison of the effectiveness of silver diamine fluoride and sodium fluoride varnish in arresting carious lesions at two different time intervals

Discussion

It is proposed that active carious lesions can be managed in two ways. They are restorative cavity control and nonrestorative cavity control (NRCC).[⁹] Although restorations of the cavitated lesions are still the standard of care, this was not used as a control group since the study has been done in schoolchildren who were brought to the department of pediatric dentistry as a part of the school dental health program. Only the children were brought from the schools without their parents, hence, we were not permitted to do restorative procedures.

In primary teeth, NRCC aims to preserve the tooth’s functionality until its exfoliation without requiring drilling or anesthesia, and hence, it is considered a child-friendly treatment.[⁹] It is advantageous over traditional restorative treatment as it eliminates the stress and fear that often results from invasive restorative therapy.

Currently, SDF has drawn much attention from both researchers and dental practitioners. SDF’s ability to control the caries process makes it different from other caries-preventive agents. Silver ions in SDF inhibit bacterial growth by interacting with the bacterial cell wall and enzymes. They have an antibacterial action by forming silver-integrated hydroxyapatite, which inhibits cathepsins.[^6,10] The fluoride component of the SDF reacts with calcium phosphate and hydroxyapatite to form fluorapatite and calcium fluoride, which improves the acid resistance of the dental hard tissues.[^6,10] Since SDF is a proven topical agent for arresting cavitated caries lesions, it was considered as control group.

The fluoride varnishes have gained immense popularity in the field of pediatric dentistry due to their ease of application in precooperative children, and those demanding special health-care needs. Virupaxi et al. reported that fluoride varnish is effective in the prevention of early childhood caries and can achieve caries reduction by 25%–45%.[¹¹]

Children in the age group of 6–9 years were considered in the study since it is learned from the literature that there is a high prevalence of nontreated carious lesions in this age group. We considered semiannual application protocol for SDF and NaF varnish to arrest dentinal caries. Fung et al. reported that semiannual application of 38% SDF (75.7%) is more effective than annual application (66.9%) in arresting dentinal caries.[¹²] The American Dental Association Council on scientific affairs concluded that applying fluoride varnish every 6 months effectively reduces caries prevalence in high-risk populations.[¹³]

No attempt was made to excavate diseased carious tissue in the current study, making the application process easier and faster. This noninvasive technique made subject compliance possible even for young children. Occlusal cavitated lesions were chosen as they are easily accessible for hygiene maintenance than proximal lesions. The lesions treated with SDF tend to have grayish-to-black discoloration. Hence, to combat discoloration, potassium iodide was applied after the SDF application in the current study. Studies have shown that there is no significant difference between the antimicrobial actions of SDF alone, and SDF/KI combination, indicating that KI does not affect the microbicidal action of SDF.[^14,15] However, in the present study, the application of KI did not fully eliminate the discoloration.

In the current study, it was observed that SDF displayed a better caries arresting potential than NaF varnish at both 6- and 12-month intervals in primary molars. This could be because 38% SDF contains a high concentration of both silver (253,870 ppm) and fluoride (44,800 ppm) and has an alkaline property. It inhibits bacterial growth initially and eventually increases dentin remineralization. Whereas, 5% NaF varnish has a lower concentration of fluoride (22,600 ppm).

These results are in accord with a randomized controlled trial conducted by Mabangkhru et al. on young children who were followed up for 12 months.[¹⁶] They concluded that caries arresting potential of 38% SDF was higher than 5% NaF varnish when applied semiannually.[¹⁶] Furthermore, Duangthip et al. concluded that SDF was 66% effective in arresting carious lesions when compared to NaF varnish which has 41% effectiveness.[¹⁷] Similarly, in an umbrella review, Seifo et al. reported that 38% of SDF has 65%–91% and fluoride varnish has 38%–44% caries arresting potential in the primary dentition.[¹⁸]

In the present study, fluoride varnish demonstrated a caries arresting potential of 42% at 12-month interval. A Cochrane systematic review on fluoride varnish application concluded that it reduced caries in the primary dentition with a prevention fraction of 37%.[¹⁹] Fluoride varnish relies mainly on a single mechanism to control caries progression. It restores the mineral content lost during the active caries process and makes the hard tissues more resistant to demineralization in future pH drops.[⁶]

In the current study, almost similar rate of caries arrest was observed at 6- and 12-month intervals in SDF as well as NaF varnish groups. This might be due to the second application at 6-month intervals. Similarly, Zhi et al. concluded that the proportion of active dentin that had become arrested increased after increasing the frequency of SDF application to every 6 months.[²⁰] Mabangkhru et al. stated that the caries arrest rates of SDF and NaF varnish at the 12-month time interval were higher than those at the 6-month time interval.[¹⁶] This might be due to good oral hygiene maintenance and periodic topical fluoride application.

SDF is safe for children who cannot cooperate with traditional caries treatment. It is simple and practical to implement in a community setting because it requires less time and minimal resources. This helps in improving access to dental care in remote areas. In most situations, the advantages of SDF application outweigh the drawbacks, such as black discoloration of dentin lesions. NaF varnish has shown caries arresting potential but is less effective than SDF. Hence, SDF can be routinely used as an interim treatment modality in cavitated primary molars.

The clinical implication of the study is it provides evidence that 38% of SDF effectively arrests cavitated caries lesions. Hence, this can be used in disadvantaged communities where untreated dental caries and early loss of primary teeth are persistent. The limitation of the study is plaque levels and DMFS levels of the subjects were not considered in the study. Plaque and DMFS levels may influence caries lesion activity; hence, there is a future scope to carry out the research in these lines.

Conclusion

SDF has shown better caries arresting potential than NaF varnish in cavitated primary molars when applied semiannually.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.