Supplementary Material for: Cost-Effectiveness of the Toddler Oral Health Intervention in Dutch Well-Baby Clinics: A Trial-Based Economic Evaluation

Background & objective: Early Childhood Caries (ECC) affects one in four Dutch five-year-olds and disproportionately impacts children from lower socioeconomic backgrounds. The Toddler Oral Health Intervention (TOHI) integrates oral health promotion into well-baby clinics, aiming to prevent ECC from the eruption of the first tooth. This study evaluates the cost-effectiveness of TOHI compared to care-as-usual (CAU) from a societal perspective, using caries reduction and quality-adjusted life years (QALYs) as outcomes. Methods: A trial-based economic evaluation was conducted alongside a pragmatic randomized controlled trial with approximately 3 to 3.5 years of follow-up (n=353). Costs (intervention delivery, dental healthcare, parental travel, and productivity losses) were combined with clinical and utility outcomes to calculate incremental cost-effectiveness ratios (ICERs). Missing and skewed data were handled using multiple imputation and bootstrapping, respectively. Analyses were adjusted for maternal socioeconomic position. Results: TOHI reduced cavitated caries lesions (ICDAS ≥3) by 0.93 lesions per child at an incremental cost of €93, resulting in an ICER of €100 per lesion prevented compared to CAU. The probability of cost-effectiveness exceeded 80% at a willingness-to-pay (WTP) threshold of €250 per lesion. TOHI also yielded a QALY gain of 0.01 per child, with an ICER of €6,262 per QALY gained. The probability of cost-effectiveness for QALYs exceeded 80% at a WTP threshold of €20,000 per QALY and increased to approximately 85% at €40,000 per QALY. Sensitivity analyses supported the findings’ robustness. Conclusion: TOHI is a more costly, yet also more effective strategy for reducing ECC and improving quality of life within the Dutch well-baby clinic system. With a low upfront investment and ICER and a moderate-to-high probability of cost-effectiveness at the €20,000 per QALY threshold, TOHI seems to represent good value for money. Future research should assess long-term cost-effectiveness, broader healthcare impacts, and scalability across healthcare settings.