Effect of sealant versus fluoride varnish on dental caries incidence in Mexican children: A randomized controlled clinical trial

Introduction

Dental caries is a prevalent oral health issue that has a significant impact on the worldwide population [1]. This condition is characterized by a range of etiological variables, and exhibits a higher prevalence in pediatric and young adult age groups [2]. According to official figures, the occurrence of dental caries among children worldwide ranges from 60% to 90%. Additionally, it has been shown that those with a lower socio-economic status tend to experience a higher incidence of dental caries [2, 3]. Negative consequences of this phenomenon are evident in individual’s quality of life, as indicated by various complications [4, 5].
Dental caries is a preventable disease. However, despite the marked reduction in its incidence observed in larger populations of many developed countries, it remains a health issue in developing countries [2]. Topi­cal fluorides in various presentations (i.e., toothpaste, oral rinse, gel, and varnish) significantly contribute to the control of this disease. Fluoride varnish (FV) is a concentrated topical fluoride that increases the exposure of enamel leading to slowing de-mineralization process, supporting re-mineralization process, and undermining bacterial metabolism [6-8]. In recent decades, there have been notable changes in strategies employed for the management of lesions. Understanding of the significance of preventative dentistry and effective handling of early-stage tooth decay had significantly transformed the field of dentistry. Treatments have become minimally invasive, aiming at preserving the maximum amount of tooth enamel for as long as possible [9-11]. Other preventive caries treatments are used in developed countries to reduce caries incidence, including pit and fissure sealants [12-14]. A pit and fissure sealer (PFS) is a relatively low viscosity substance with the ability to infiltrate into depths of narrow grooves and crevices of teeth. The use of this preventative intervention effectively mitigates the likelihood of caries formation on the occlusal surfaces. This is achieved by creating a physical barrier that hinders the accumulation of biofilm [14, 15].
Dental caries among schoolchildren in Mexico pre­sents a significant public health concern [16-22]. Never­theless, there has been limited research conducted on the implementation of preventative interventions, aside from fluorides, among school populations. The application of such interventions remains very infrequent [23]. From the economic point of view, dental caries and its consequences are seen as a burden for both general population and health system. Although prevention methods can improve the population’s oral health status, it is also necessary to consider economic impacts. Moreover, comparing the effectiveness of different approaches available contribute to a better decision-making by health planners [24].

Objectives

The objective of the present study was to compare the effectiveness of two prevention methods during a short-term incidence of dental caries affecting first permanent molars among public elementary schoolchildren aged from 6 to 8 years.

Material and methods

Study design

The study was a randomized clinical trial. Partici­pants were chosen from public elementary schools located in four communities (Pachuca, Tizayuca, San Agui­tín Tlaxiaca, and Mineral del Chico) in Hidalgo State, Mexico. Hidalgo is classified as one of the 32 administrative divisions within the country of Mexico. The region under consideration comprises of a total of 84 distinct administrative divisions known as municipalities, with the primary urban center being Pachuca de Soto City. At the national level, Mexico does not implement a water fluoridation program. Instead, the country relies on the usage of fluoridated salt. It is worth noting that certain regions, such as parts of Hidalgo State, possess naturally elevated fluoride levels in their water sources. However, this phenomenon does not occur in Pachuca and specific localities chosen for the study [24, 25].
Study protocol has been previously published [26], and Figure 1 depicts the methodological design of the study. Children aged six to eight years, with at least one totally erupted and healthy permanent molar were selected. One of two treatments (conventional sealant: Clinpro© 3M, Saint Paul, MN, USA; and fluoride varnish: 5% Duraphat© Colgate, New York, USA) was randomly applied to occlusal surfaces of the first permanent molars.

Sample and selection of participants

Sample size was estimated using a procedure that accounted for disparity in proportions. The study employed the utilization of two figures: a 60% reduction in reported incidence when employing fluoride varnish, and a 40% reduction when using pit and fissure sealant. Statistical power was set at 80%, and 95% confidence interval was applied. Based on these parameters, the sample size required for the study was determined to be 97 individuals. Ten percent was added to compensate for losses to follow-up, yielding a final figure of 105 individuals in each group.

Selection criteria

Participant had to attend one of the schools selected to be eligible for participation in the study, aged six to eight years, with at least one totally erupted and healthy first permanent molar, with high or moderate risk of caries according to the Scottish Intercollegiate Guidelines Network [27]. Subjects whose parents did not sign the informed consent were excluded from the study as well as children who did not assent to the oral exam or intervention.

Intervention

Following the selection of subjects, an initial randomization procedure was conducted to allocate intervention therapy to the first permanent molars of each participant. Treatment procedure was conducted within the educational institution using a mobile tripod apparatus and relying solely on natural illumination. Admini­stration of treatments occurred subsequent to prophylactic measures and within initial hour of classes, with the intention of ensuring that the children would refrain from consuming any food for a minimum of two hours following the treatment, taking into account desig­nated meal breaks. Duration of the follow-up period was six months, as depicted in Figure 1, and it has been thoro­ughly documented in a previous study [27].
The incidence of dental caries was measured with scoring of visible changes on the enamel assessed on the baseline measurement and the second measurement (six months later). Clinical examiner and pointer were calibrated and standardized (kappa > 0.80). Standardized and international caries measurement system was employed (international caries detection and measurement system – ICDAS II), with the following scoring details [28]:
0 – Sound tooth surface: No evidence of caries after 5 sec air drying.
1 – First visual change in enamel: Opacity or discoloration (white or brown) visible at the entrance to the pit or fissure seen after prolonged air drying.
2 – Distinct visual change in enamel visible when wet, and lesion must be visible when dry.
3 – Localized enamel breakdown (without clinical visual signs of dentinal involvement) seen when wet and after prolonged drying.
4 – Underlying dark shadow from dentine.
5 – Distinct cavity with visible dentine.
6 – Extensive (more than half the surface) distinct cavity with visible dentine.

Randomization

Excel software was used for the randomization process. A list of selected participants was prepared in Excel software, and the random number function was applied to distribute the groups. Half of the participants were assigned to the group with pit and fissure sealant, and the rest were allocated into the fluoride varnish group.

Measuring the effectiveness of the intervention

Variables

Dependent variable was the incidence of dental caries using ICDAS II measuring system (0 = healthy, 2 = code 2, 3 = code 3, 4 = code 4, 5 = code 5, 6 = code 6). The main independent variable was the prevention method used (0 = sealant, 1 = varnish). Other factors were included in the analysis, such as sex (0 = male, 1 = female), age (6-8 years), and basal dmft (average number of decayed, missing, and filled primary teeth).

Blinding

The nature of the technologies used limited blinding. The participant may not had been aware of the treatment received, but the dentists performing the interventions had to know the differences, as they followed the manufactures’ recommendations. The clinician who performed the dental examination had not any information about the treatment applied, although the presence or absence of the pit and fissure sealant would likely indicate the treatment received by the patient.

Data collection and statistical analysis

General features of the sample were first described in statistical analysis. Afterwards, a bivariate analysis was conducted that aimed at observing statistically significant differences between loss to follow-up of the participants and across independent variables. Chi-square test was employed to assess the association between the dependent variable and the exposure variable. Mann- Whitney U test and Fisher’s exact test were also used. Statistical package utilized was Stata version 14.0 (Stata Corp. LLC, Texas, USA).

Ethical issue

The study received approval from the Ethics Committee of the Autonomous University of the State of Hidalgo, with the reference number of Cinv/Icsa/0024/2018. The study adhered to the research regulations and legal framework in Mexico, and was carried out in compliance with the Declaration of Helsinki of 1975, as amended in 2013. Legal guardians or parents of the participants involved in the study provided written consent after being adequately informed about the study’s purpose, procedures, and potential risks and benefits.

Results

Of the 210 participants selected for this clinical trial, 53.3% were females, with an overall mean age of 7.25 ± 0.80 years. The average number of decayed, filled, and missing teeth, or teeth indicated for extraction (the basal dmft of the participants) was 3.35 ± 3.45 (Table 1). At six months, there was an attrition rate of 15.7%. One of the subjects refused to continue participating in the project, and the remainder of missing participants could not be found due to address change, school absence during the assessment period, or loss of contact due to health-related incidents. Attrition was not differentially associated across sex (p = 0.979), age (p = 0.776), type of treatment (p = 0.850), and basal dmft (p = 0.9535) (Table 2). The incidence of caries in the first permanent molars is listed in Table 3.
The comparison between the two procedures was carried out using the dental caries incidence. The analy­sis yielded statistically significant differences between the pit and fissure sealant (Clinpro 3M) and the fluo­ride varnish (Duraphat Colgate) only in 16 and 36 of the first permanent molars (p < 0.05), respectively (Table 4). The procedure with the highest number of healthy cases was the pit and fissure sealant.
The dmft examination showed a statistically significant association with caries incidence (p < 0.05). The average dmft was higher in those participants who presented visual changes in the enamel (ICDAS II > 2) (Table 4). A positive correlation between the basal dmft and the severity of carious lesions in the first permanent molars receiving either of the two treatments (Table 5) was observed. The time for the application of treatments was 7.59 ± 2.42 for the varnish, and 11.56 ± 2.79 for the sealant (Mann-Whitney U test, p < 0.0001).

Discussion

The objective of the study was to compare the effect of two procedures on caries incidence. The null hypo­thesis was that there was no statistically significant difference between the procedures. The results partially rejected it, since a difference was indeed noted between the two procedures, but it was only statistically signi­ficant for 26 and 36 teeth. The prevention methods for dental caries used in this work were both proven effective when used on occlusal surfaces [6-8, 12-14, 29].
Although there was a 15% loss to follow-up in this research, probably caused by the current overall health-related incidents, attrition was not statistically significant. Our results are consistent with those reported by Bravo et al. [30] and with a systematic review published by Wright et al. [31]. The latter concluded that pit and fissure sealant reduced the risk of dental caries on occlusal surfaces to a higher extent compared with fluo­ride varnish. Li et al. [32] in their meta-analysis did not report any statistically significant differences between PFS and FV. The follow-up period in the present study varies from that reported by other researchers. Clinical trials conducted by Bravo et al. [30, 33] revealed a decreased occurrence of caries in the group treated with pit and fissure sealant. This finding suggests that the preventive impact of fluoride varnish diminishes over time, whereas the pit and fissure sealant acts as a more durable physical barrier [33]. Given the inconsistencies observed in the existing body of literature, it is imperative to undertake additional research aiming at establishing standardized methodologies and extending the duration of follow-up periods.
A statistically significant relationship was observed between the basal dmft and the caries incidence on occlusal surfaces. Past caries experiences can influence the process of new carious lesions [34, 35]. However, that relationship with the basal dmft did not differ across the type of treatment. Some differences should be considered in the comparison of the materials used. In general, applying fluoride varnish is a simpler process compared with pit and fissure sealants, not requiring complex technique.
A limitation of the research work is the short duration of follow-up interval; it does, however, offer a perspective from a shorter follow-up. We found that pit and fissure sealant was partially more effective than fluoride varnish. It remains to be seen whether a longer follow-up is really needed to further differentiate between the two interventions, or to ascertain effects on additional first permanent molars. Also, other aspects in the competing performance need to be examined, such as cost-effectiveness of materials used and procedures.

Conclusions

In the current study, the pit and fissure sealant treatment was found to be partially more effective than the fluoride varnish. Longer follow-up is needed, including other aspects of the assessment. Pit and fissure sealants and fluoride varnish can be effectively applied as preventive methods on any permanent posterior teeth without adverse effects in their clinical performance.

Disclosures

1. Institutional review board statement: The study was approved by the Ethics Committee of the Autonomous University of the State of Hidalgo, with the reference number of Cinv/Icsa/0024/2018. International register: Sri Lanka Clinical Trials Registry. Trial application No.: APPL/2018/052.
2. Assistance with the article: None.
3. Financial support and sponsorship: This research was partially supported by a fieldwork grant from the Program for Strengthening Quality in Educational Institutions (Programa de Fortalecimiento de la Calidad en Instituciones Educativas – PROFOCIE).
4. Conflicts of interest: The authors declare no potential conflicts of interest concerning the research, authorship, and/or publication of this article.

References