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Comparing the Costs of Three Sealant Delivery Strategies
1 Centers for Disease Control and Prevention/Division of Oral Health/Surveillance, Investigations and Research Branch, 4770 Buford Highway, MSF10, Chamblee, GA 30341; and Correspondence: * corresponding author, sig1{at}cdc.gov
We analyzed the cost-effectiveness of 3 sealant delivery strategies: Seal all (SA), seal children assessed to be at risk by screening (TARGET), and seal none (SN). We assumed a nine-year analytic horizon, a 3% discount rate, and zero screening costs. Estimates for sealant costs ($27.00) and restoration costs ($73.77), annual caries increment (0.0624 surfaces), sealant failure rate (20% in yr 1 and 3% thereafter), annual amalgam failure rate (4.6%), and sensitivity (0.635) and specificity (0.795) of screening were obtained from published studies. Under baseline assumptions, TARGET dominated (cost less and reduced caries) SA and SN. If annual caries increment exceeded 0.095 surfaces, SA dominated TARGET, and if increment exceeded 0.05 surfaces, TARGET dominated SN. If sealant costs decreased to $6.00 (reported cost for school programs), TARGET dominated SN for caries increments exceeding 0.007 surfaces, and SA dominated TARGET for caries increments exceeding 0.034 surfaces.
Key Words: dental sealants • cost-effectiveness • screening • delivery of health care
Among US schoolchildren, approximately 90% of dental decay occurs in tooth surfaces with pits and fissures (Kaste et al., 1996). Dental sealants are highly effective in reducing pit and fissure decay, sealants having been shown to be over 50% effective up to 10 yrs after application (Weintraub, 1989). Thus, universal delivery of sealants potentially could reduce the number of decayed surfaces by 45%. However, sealants are not widely used. National data indicate that only about 23% of eight-year-old children have received a sealant on a permanent molar (US Department of HHS, 2000). One reason for the low prevalence of sealants is that this primary preventive service is perceived to cost more than treating caries among children with low caries rates. Caries is not uniformly distributed through the US school-aged population. Approximately 80% of all caries is concentrated in 25% of school-aged children (Brown et al., 1996). Thus, insurers may not cover sealants, since the cost of universal delivery is likely to be greater than the cost of treating decay that could be averted by sealants (Eklund, 1986). Even in community programs that generally target children at increased risk for caries and lack of access to care, most experts have recommended assessing individual risk (ASTDD, 1995; US Department of HHS, 2000), and a risk-based performance measure has been developed (Crall et al., 1999). One study suggested that universal delivery of sealants is cost-saving compared with no delivery among low-income children with high caries prevalence (Weintraub et al., 1993). However, no economic analyses comparing universal delivery with risk-based delivery have been conducted. Our objective in this study was to analyze the relative cost effectiveness of 3 sealant delivery strategies: Seal none (SN); seal if the child is determined, through screening, to be at risk for future caries (TARGET); and seal all (SA). More detailed information on parameter estimates and results from the sensitivity analyses (referenced as Web-Table and Web-Fig.) may be accessed by the interested reader at an appendix on the Journal of Dental Research Web site (www.dentalresearch.org).
Model Overview We calculated the incremental cost, incremental effectiveness, and incremental cost-effectiveness (additional cost divided by additional effectiveness) of SA vs. TARGET, SA vs. SN, and TARGET vs. SN (Web-Table 1). After ranking strategies by dominance (ruling out strategies that were more costly and less effective), we used one-, two-, and three-way sensitivity analysis to examine the stability of the rankings. In the analysis we made the following assumptions:
Clinical Data
Annual sealant loss rates were imputed from a published review of 101 studies (Web-Table 2; Ripa, 1993). Annual amalgam failure rates were imputed from two studies, one that estimated median amalgam survival time (Ryke, 1992) and one that estimated five-year failure rates (Roberts and Sheriff, 1990). Sensitivity and specificity of screening tests with socio-demographic characteristics, tooth morphology, or caries history (Web-Table 3) were obtained from a published review (Powell, 1998).
Costs
Cost-effectiveness Analysis (Baseline Assumptions) Under SN, the annual caries increment equals 0.0624; the nine-year cumulative caries increment equals 0.562 (Web-Table 5), with a discounted value of 0.486 (Table 2  ). Under SA, however, the caries increment depends on both caries increment in the absence of sealants and sealant effectiveness (retention); the nine-year cumulative caries increment under SA equals 0.247 (Web-Table 5), with a discounted value of 0.208 (Table 2). Under TARGET, the discounted nine-year cumulative caries increment equals 0.309. Thus, the additional sound surfaces per child resulting from increased sealant delivery equal 0.278 for SN to SA, 0.101 for TARGET to SA, and 0.177 for SN to TARGET.
The expected per-child restoration costs for SN, SA, and TARGET are $35.84, $15.35, and $22.82, respectively, and the expected sealant costs are $0, $27.00, and $12.06. The total costs per child associated with SN, SA, and TARGET are $35.84, $42.35, and $34.88, respectively. After averted decay is considered, TARGET dominates SN. Going from SN to SA would cost $23.42 per saved tooth surface. Going from TARGET to SA would cost $73.96 per saved tooth surface (Table 2  ).
One-way Sensitivity Analysis
The cost of delivering sealants decreases relative to no delivery as restoration costs increase or as sealant costs decrease or as the ratio of restoration to sealant costs increases. Since sealant delivery costs are realized at the beginning of year 1, while restoration costs do not occur until later years, expected treatment savings decrease as the analytic horizon decreases or as the discount rate increases, in which case SN becomes more attractive relative to SA or TARGET. For example, if we were to limit the analytic horizon to 7 yrs, the respective costs associated with SN would be less costly than those with TARGET, $28.68 vs. $29.31. In addition, for discount rates above 5%, SN becomes the least costly strategy.
If the sealant loss rate takes on its maximum value, 28% in year 1 and 4% thereafter (Web-Table 2), SN becomes the least costly strategy, SN = $35.84 < TARGET = $38.22 < SA = $47.60. Changing the baseline assumption of zero screening costs to a cost 0f $0.96 per child would result in SN being less costly than TARGET (Table 2
Two-way Sensitivity Analysis
Three-way Sensitivity Analysis Increasing the sensitivity and specificity of the screening tests shifts the SA-TARGET break-even frontier outward (Web-Fig. 1). As false-positives and -negatives decrease, TARGET becomes less costly, and thus a higher ratio of restoration to sealant costs is required for SA to be the dominant strategy for a given caries increment. For example, for a caries increment equaling 0.07, if the sensitivity and specificity increased from their baseline values to 0.9, the ratio of restoration to sealant costs would have to increase from 4.6 to 12.7 for SA to remain the dominant strategy. The SN-TARGET frontier shifts inward as screening sensitivity and specificity increase (Web-Fig. 2), because decreasing numbers of false-positives and false-negatives lower the cost of TARGET and thus lower the break-even ratio of restoration to sealant costs required for each caries increment. For example, if the caries increment equaled 0.02, increasing screening sensitivity and specificity from their baseline values to 0.9 lowers the break-even ratio of restoration to sealant costs from 5.0 to 2.8. The vertical shift in the break-even frontier caused by increased screening sensitivity and specificity is greater for lower caries increment values. Thus, changes in sensitivity or specificity will be associated with smaller changes in the break-even ratio of restoration to sealant costs for higher caries increments.
We have shown that delivery of sealants, whether through SA or TARGET delivery, becomes less costly relative to SN with increases in the annual first molar occlusal caries increment and the ratio of restoration to sealant costs. Because changes in these variables have a larger effect on SA than on TARGET, increasing them causes the costs associated with SA to decrease relative to those of TARGET. In addition, TARGET becomes less costly relative to SN or SA as screening sensitivity and specificity increase. The ratio of restoration to sealant costs will vary by community, due to differential resource costs, dental market structures, and regulatory environments. Annual caries increment is also likely to vary by community. Thus, the sealant delivery strategy should be determined at the community level. The most important contribution of this research, the sensitivity analysis, allows decision-makers to determine if a dominant sealant delivery strategy exists. It is important to note that while points on or above the break-even frontier indicate that increased delivery of sealants is the dominant strategy, points below the frontier do not indicate that decreased delivery of sealants dominates. Although increased delivery is more costly, the associated increase in effectiveness may be well worth the investment. For example, spending $23 (SN to SA) to save one tooth surface from caries may be a very good investment, depending on such factors as an individual’s valuation of oral health, his or her aversion to restorative dental care, and the value of competing alternatives. Another caveat that should be mentioned when our results are interpreted is that we used dental fees as a proxy for the cost of resources to provide restorations and sealants in a clinical setting. If dental markets are competitive, or if demand for these two procedures is equally elastic, it is likely that the ratio of restoration to sealant costs will indeed measure relative resource costs. A national survey reported that providing single-surface restorations requires 2.5 times more effort than does providing sealants (RVU, 2000). This value is slightly higher than that which we obtained from dental fees, 2.33 ($63/$27). If we had used 2.5, SA would dominate SN for annual caries increments exceeding 0.075 surfaces. Most of the assumptions used in this analysis are conservative and biased against accepting SA. Our assumptions (that all decay is treated with a single-surface amalgam instead of more costly treatment options, and that the cost of sealing additional teeth is the same as the cost of sealing the first tooth) inflate the costs of SA relative to TARGET and the costs of TARGET relative to SN. The assumption of zero screening costs would deflate the cost of TARGET relative to SA or SN. Finally, our assumption that the annual permanent 1st molar caries increment is constant or, equivalently, that the annual caries attack rate among sound surfaces is increasing deflates expected restoration costs and thus biases the results away from SA. (For example, assuming a constant caries increment equaling 0.105 per yr would imply attack rates of 0.105, 0.1173, and 0.135, respectively, in years 1, 2, and 3.) Almost no data exist on annual occlusal caries increment and its progression over time. We followed the example of two longitudinal studies that examined annual occlusal caries increment and found that it remained fairly constant over time in the first molars of schoolchildren ranging in age from 10-16 yrs and 6-13 yrs (Bohannan et al., 1984; Ripa et al., 1988). For our nine-year caries increment estimate, if we had assumed the attack rate among sound occlusal surfaces to be constant, then the caries increment in earlier years, which are weighted more heavily due to discounting, would be higher, and thus restoration costs would increase relative to sealant costs. [Pr (15-year-old has sound 1st molar occlusal surface) = 1 - 9*0.105 = 0.055; Pr (surface sound sound in previous period) = 0.0551/9 = 0.725; thus, Pr (surface decayed sound in previous period = 1 - 0.725 = 0.275.] The costs of delivering sealants may also vary by setting. Estimates of sealing teeth in community programs, for example, are generally lower than those in clinical settings. Published estimates of the cost of sealing a tooth (1999 $US) range from $4.75 (Calderone and Mueller, 1983) to $6.50 (Klein et al., 1985), and thus the ratio of restoration to sealant costs would exceed 12. If we assume that the effectiveness of sealants does not vary by delivery site, in school-based/-linked sealant programs, SA could be less costly than SN for annual caries increments as low as 0.018 and less costly than TARGET for annual attack rates of 0.035 or higher. These findings suggest that, over a nine-year horizon, individualized risk assessment of children enrolled in most school-based programs may be unnecessary. School-based programs generally target low-income children who are less likely than higher-income populations to receive preventive services and to have a regular source of care (US Department of HHS, 2000).
A supplemental appendix to this article is published electronically only at http://www.dentalresearch.org. Received for publication December 6, 2001. Revision received April 17, 2002. Accepted for publication June 17, 2002.
Journal of Dental Research, Vol. 81, No. 9,
641-645 (2002) This article has been cited by other articles:
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TOP
ABSTRACT
INTRODUCTION
Seal None strategy.
Target strategy.
Seal All.
