Cost-effectiveness of caries excavations in different risk groups - a micro-simulation study

Abstract

Background: Whilst being the most prevalent disease worldwide, dental caries is increasingly concentrated in high-risk populations. New caries treatments should therefore be evaluated not only in terms of their cost-effectiveness in individuals, but also their effects on the distribution of costs and benefits across different populations. To treat deep caries, there are currently three strategies: selective (one-step incomplete), stepwise (two-step incomplete) and complete excavation. Building on prior research that found selective excavation generally cost-effective, we compared the costs-effectiveness of different excavations in low- and high-risk patients, hypothesizing that selective excavation had greater cost-effectiveness-advantages in patients with high compared with low risk.

Methods: An average tooth-level Markov-model was constructed following the posterior teeth in an initially 18-year old male individual, either with low or high risk, over his lifetime. Risk was assumed to be predicted by several parameters (oral hygiene, social position, dental service utilization), with evidence-based transition probabilities or hazard functions being adjusted for different risk status where applicable. Total lifetime treatment costs were estimated for German healthcare, with both mixed public-private and only private out-of-pocket costs being calculated. For cost-effectiveness-analysis, micro-simulations were performed and joint parameter uncertainty introduced by random sampling of probabilities. Cohort analyses were used for assessing the underlying reasons for potential differences between strategies and populations.

Results: Selective excavation was more effective and less costly than both alternatives regardless of an individual's risk. All three strategies were less effective and more costly in patients with high compared with low risk, whilst the differences between risk groups were smallest for selective excavation. Thus, the cost-effectiveness-advantages of selective excavation were more pronounced in high-risk groups, who also benefitted the most from reduced private out-of-pocket treatment costs.

Conclusions: Whilst caries excavation does not tackle the underlying sources for both the development of caries lesions and the potential differences of individuals' risk status, selective excavation seems most suitable to treat deep lesions, especially in patients with high risk, who over-proportionally benefit from the resulting health-gains and cost-savings.

Figure 1

Used Markov-model. We followed posterior teeth in a male patient initially aged 18 years over his lifetime. The prevalence of caries lesions was assumed to differ between risk groups. The probability of a sound surface developing a shallow dentinal lesion was determined by p_develope. Depending on the patient’s utilization of dental services (p_ utilization), the patient attended for a dental checkup, where the dentists detected and invasively treated the lesion with a certain probability (p_detection). Treatment at this stage resulted in a shallow occlusal composite restoration, which failed according to its transition probability (p_fail_composite), resulting either in repair or refill according to the respective allocation probability. If failing a second time, re-treatment was assumed. Progression of a shallow lesion (according to p_progress) was assumed to lead to a deep dentinal lesion, which was subsequently treated by one of three caries excavation strategies. Transition probabilities in follow-up stages were modelled as described elsewhere [15]. Bold variables were found to differ according to an individual’s risk group, and were used to separately model low- and high-risk patients.

Figure 2

Cohort analyses of different excavations in different risk groups. The proportion of teeth without pulpal vitality (root-canal treated or extracted teeth) was monitored over a patient’s lifetime. Selective excavation (green, solid/dashed line: high- and low-risk individuals) retained pulpal vitality more successfully than alternative strategies (blue: stepwise, red: complete excavation), with greater advantages compared to alternative strategies in high- than low-risk individuals.

Figure 3

Cost-effectiveness-acceptability curves. The probability of a treatment being cost-effective depending on a payer’s willingness-to-pay was plotted against the maximal threshold of this willingness. With higher willingness-to-pay, cost-differences between strategies become less important for the probability of being cost-effective. Selective excavation (green, solid/dashed line: high-/low-risk individuals) had the highest probability of being cost-effective regardless of the threshold value.

Figure 4

Sensitivity analysis. The cost-effectiveness (Euro/year) was evaluated for different strategies (green/blue/red: selective/stepwise/complete excavation) in low-risk (A) and high-risk (B) individuals depending on the initial age of a patient. Note that higher cost-effectiveness indicates higher costs per effectiveness, i.e. is less advantageous than lower cost-effectiveness. In older patients, differences between strategies were limited, especially in low-risk patients, since only a few individuals developed caries lesions and less (costly) follow-up treatments occurred. In contrast, selective excavation was most advantageous in younger patients. Cost-effectiveness was significantly worse in high- than low-risk patients.