An economic evaluation of pit and fissure sealants and fluoride varnishes in preventing dental caries: a systematic review

2.1 Inclusion criteria

This systematic review was conducted following the guidelines proposed by the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) [27]. The PICO framework including population, intervention, comparator, and outcome was used to guide the search strategy:

• Types of Participants (P).

Children and adolescents aged 3–18 years with primary and/or permanent teeth.

• Types of Intervention (I).

PFSs and/or FVs that can be applied in clinical, school or community settings.

• Types of Control/Comparison (C).

The control groups were those not receiving sealants or professional topical fluoride application. The FVs group was used as the control when making a comparison with the PFSs group.

• Types of Outcome Measures (O).

The primary outcome was to assess the effectiveness, utility, or benefits of PFSs and FVs, such as DMFT(S) reduction percentage, full mouth dental reconstructions (FMDRs) avoidance, quality adjusted life-year (QALY) and disability-adjusted life years (DALY) averting, the decrease in increment of dental caries reduction. The secondary outcome was the cost-saving and benefit associated with applying PFSs and FVs, such as the incremental cost-effectiveness ratio (ICER).

2.2 Exclusion criteria

Publications comparing PFSs or FVs with other preventive interventions without control were excluded. The language was restricted to English.

2.3 Search strategy and study selection

We searched the electronic databases Cochrane Oral Health Group’s Trials Register (till to 03 June 2022), Web of Science (from 1945 to 03 June 2022), PubMed (from 1996 to 03 June 2022), and EMBASE via Ovid (from 1980 to 03 June 2022). A predefined search strategy was used in the search procedures: (((((Pit and fissure sealants) OR (Fissure sealants) OR (Dental sealants) OR (Tooth sealants))) OR Fluoride varnish)) AND ((Economic evaluation) OR (Cost evaluation) OR (Cost-effectiveness analysis) OR (Cost-benefit analysis) OR (Costs and benefits) OR (Cost-utility analysis) OR (money saving)). Two review authors independently performed a preliminary screening of the articles by reading the titles and abstracts. Next, they screened the selected articles by full text. The agreement about study inclusion, data extraction, and risk of bias assessment was achieved by discussion. We attempted to contact the study authors to obtain missing or unclear information.

2.4 Data extraction

We used a predesigned data extraction form to extract the following study characteristics: first author, year of publication, country, length of follow-up, age of the target population, number of participants, type of teeth, type of preventive program, type of economic evaluation, currency, discount rate, perspective (societal, public health, payer, or Medicaid payer), and outcomes (number of restorations avoided, dental caries reduction, calculation of cavity-free months/year, quality/disability-adjusted life years).

3.1 Study characteristics

A total of 19 selected studies were summarized. Nine studies were conducted in the USA [7, 9, 19, 24, 25, 28, 29, 30, 31], three in Chile [16, 26, 32], one in the UK [33], one in Spain [3], one in Germany [34], and one in Australia [35], and three studies did not mention the country [36, 37, 38]. For intervention comparison, nine studies compared PFSs with control [9, 24, 28, 29, 30, 31, 32, 36, 38], five compared FVs with control [16, 26, 34, 35, 37], and five studies compared PFSs with FVs [3, 7, 19, 25, 33] (the general and methodological characteristics of the included studies was listed in Supplementary Table 1).

3.2 Summary assessments of ”risk of bias”

To conclude the overall risk of bias for economic evaluation analysis of the intervention, the studies were classified as low, unclear, or high risk of bias. Our classification was mainly based on the following domains: random sequence generation, allocation concealment, blinding of outcome assessment, incomplete outcome data, and selective outcome reporting. Most of the included studies were retrospective cohort studies, except for a few studies that were randomized controlled trials [7, 16, 33]. As information to judge most domains was often incomplete or missing, the quality of the studies was generally low, which was shown in Figs. 2,3.

Fig. 2.Risk of bias graph: review authors’ judgments about each risk of bias domain presented as percentages across all included studies.

Fig. 3.Risk of bias summary: review authors’ judgments about each risk of bias domain for each included study. Green, low risk of bias; Yellow, unclear risk of bias; Red, high risk of bias.

3.3 Synthesis of the results

The most appropriate relevant results were summarized in a narrative synthesis, focusing on currency, economic evaluation type, and methodological characteristics that estimated the cost and effectiveness and cost. The characteristics of cost and effectiveness in the economic evaluations were presented in Supplementary Table 2. Given the heterogeneity of the studies, no meta-analysis or statistical grouping of the summary measurement was performed. 13 studies conducted CEA [3, 7, 16, 19, 24, 25, 26, 28, 30, 31, 34, 36, 37], five conducted CUA [9, 29, 32, 33, 38], and one conducted both CEA and CUA [35]. The discount rate in most studies was 3%.

4.1 Overview

The high prevalence of dental caries renders an urgent requirement for effective caries control strategies. PFSs and FVs are two common professional approaches for caries prevention globally [7, 24]. In China, the National Oral Health Comprehensive Intervention Program for Children has funded a free dental sealing service for school children aged 6–9 years old since the late 2000s [39]. The American Dental Association recommends that sealants should be applied on both primary and permanent molars in children who are at high risk of dental caries [40]. Preschool and school-based FV programs have also been conducted in many countries, including the United States, Canada, Australia, Sweden, and Scotland [41, 42, 43]. Many studies have already evaluated the effectiveness of PFSs and FVs in caries prevention [44, 44, 45]; however, there is no agreement on how these prevention approaches affect downstream dental care expenditures and outcomes [3, 7, 19, 25, 33]. Economic evaluation has been defined as the comparative analysis of alternative programs in terms of their costs and consequences to assist policymakers to make effective use of scarce resources to obtain the largest benefit [22, 47]. However, the application of economic evaluation is still limited in preventive dentistry [21, 45]. Given the fact that the incidence of dental caries in developing countries remains unchanged and has shown no decreasing trend in the past two decades [48], approaches for reducing caries increment and following treatment costs are worth considering. In this study, 19 economic evaluations on PFSs and/or FVs published between 2002 and 2021 were reviewed. Most studies were conducted in America and Europe, and only a few were conducted in developing countries [16, 26, 32]. The length of follow-up was at least 3 years.

4.2 Assessing the costs and effectiveness of PFSs and FVs

The incidence of caries is one of the most important variables associated with economic evaluations of PFSs and FVs [16]. The application of PFSs and FVs became less costly as the annual caries increment increased [16, 36]. Griffin et al. [28] reported that if caries increments exceeded 0.019, seal all (SA) children would dominate seal none (SN) and if caries increment exceeded 0.034, seal all children would dominate seal high-risk children. This result was similar to that of Rocio’s [36] conclusion, if the annual risk of developing a cavity was above 0.04, seal all will save more money than the cost. There is evidence suggesting that approximately 80% of caries is concentrated in 25% of high-risk people [28, 29]. Thus, it was proposed that PFSs and FVs are more effective and less expensive for children in the high-risk groups because the costs for the preventive methods would be compensated by avoiding consequent dental treatment [30, 34, 39]. The reduction in expenditures for high-risk children was greater than that for low- risk ones [9, 28, 36].

Pit and fissure caries remain the prominent in children and adolescents [36]. The clinical effectiveness of occlusal caries prevention of PFS has been established; however, the reduction of occlusal caries is mainly dependent on the maintenance of the sealants. The rate of sealant loss had the greatest effect on the increment cost-effectiveness ratio [32]. Sealants retention in molar teeth was projected to be 90% during the first 2 years, with a decrease of approximately 60% by 5 years [49]. The sensitivity analysis demonstrated that if the constant annual rate of sealant loss was less than 7%, the strategy of the seal all became more cost-effective, and that seal none would save money only if the annual rate of sealant loss exceeded 35% [36].

The costs of delivering PFSs and FVs may also differ based on different delivery settings. The application of PFSs and FVs in clinical settings by dentists or dental nurses is more expensive than that in non-clinical settings such as schools and communities. PFSs applied by a dental hygienist are more cost-effective than those applied by a dentist [50]. Usually, school sealant programs use portable dental equipment to apply sealants in schools at little to no cost to students [29]. Thus, it provides opportunities to reduce disparities in children with a low socioeconomic state and It offered opportunities to reduce disparities for children with low socioeconomic state and at high-risk of caries [30, 32]. Furthermore, school-based programs remove obstacles to accessing healthcare and reduce the high rate of broken appointments and time off work for parents [33]. However, the application of sealants costs more than the varnishes per student. This higher cost may largely stem from the differences in labor. The time spent in applying FVs in the school-based setting is 3–5 min per child [51, 52], whereas it takes approximately 30 min for dentists to apply PFS to four occlusal surfaces in a school setting [3]. The application of PFSs requires enamel etching, aspiration, and maintenance of a dry field, thus requiring more time than FVs [53]. When considering delivery costs, FVs do not require professional dental infrastructure, such as a dental chair with illumination, fluid evacuation, and so on, which is more cost-effective than PFSs when considering delivery costs [7]. Furthermore, the cost-effectiveness of FVs increases if some equipment such as an oral hygiene kit is not used and it is applied by qualified staff rather than dentists [26].

Since dental caries often takes long period to progress to a degree that restorative care is required, the studies used a shorter length of follow-ups which might have influenced the economic evaluation because the benefits did not have enough time to accumulate [26, 36]. Falk [34] reported that the health gains of FVs were greatest only if they were applied for a lifetime. Rocio [34] also discovered that FVs were not cost-saving when used in the medical setting in the first 42 months. Moreover, the cost-effectiveness of sealing the first permanent molar is less favorable when used for shorter periods [36]. In the sensitivity analyses, the application intervals of FV would affect the cost-effectiveness. If the application is only once per year, it would significantly lower the incremental cost-effectiveness ratio than when applied four times per year. Moreover, the US Preventive Services Task Force recommended that FVs should be applied at the beginning of eruption of the first primary tooth, suggesting that the age of FV application professionally is earlier than that of PFS [7].

The payer’s willingness to pay for avoiding carious lesions is also an influencing factor [54]. Tumader [3] reported that when the willingness to pay threshold was between $0–$60 per caries lesion averted, seal none was more favorable; however, for willingness to pay thresholds above $300, PFS was the preferred strategy. Furthermore, regular application of FVs to Medicaid-enrolled children was found to be cost-saving although at a lower reimbursement rate [55, 56]. However, most studies were cohort studies rather than randomized controlled trials; thus, their effectiveness needs to be further verified.

4.3 Economic evaluation model

Economic evaluation is commonly adopted by decision policymakers in the health sector for investigating the cost and effectiveness of public health programs to help plan future initiatives [22]. Unlike clinical studies that report the consequences of the intervention only, economic evaluations require more reporting items, such as resources used,, costs, and effectiveness results [23]. Although economic evaluations are commonly used in decision-making processes for health programs, only a few of examples exist in the oral health literature. The present systematic review compared PFSs and FVs in preventing dental decay in children and adolescents. At present, PFSs were most commonly evaluated by CEA. CEA measures consequences in natural units, such as cavity-free months, carious teeth reduction, or DMFT detection. It is useful to help public health policymakers and aid primary dental care providers in choosing a more preferable intervention for reducing the prevalence of dental caries. However, a recognized drawback of CEA is the lack of intangible benefits such as relief from pain or quality of life, assigned a monetary value [23]. The use of CUA has been observed in other areas of dental service research. Patita [9] weighted the outcomes of quality-adjusted tooth years (QATYs) as the measure to assess the effectiveness of PFSs. Such methods of assessing cost quality-adjusted tooth year ratios can be used in the future comparison of preventive regimens such as FVs and oral hygiene instruction in preventing caries.

The findings of the present systematic review found that the quality of economic evaluation of PFSs and FVs needs to be improved. Therefore, future studies should include long-term costs and expenses assessment, the risk sub-groups analysis, and the patients’ point of view [32], which would provide a greater understanding of the social effects of PFSs and FVs. There is a strong requirement for health economists and oral health researchers to work together on projects that will improve the quality and validity of future economic evaluations of dental caries prevention programs.

4.4 Limitations

There are some limitations to this systematic review. First, there was a lack of randomized controlled trials in the review as most of them did not meet our inclusion criteria. Next, while considering the results of this review, it should be recognized that most articles conducted theoretical models, wherein both cost and effectiveness were estimated according to the literature and general market conditions.