When Can Orthodontic Over-Treatment Be Measured? A Pre-Registered Identification Assessment, a Falsified Claim, and a Cross-Sectional Analysis of Untreated Occlusal Need in NHANES III

Background/Objectives: Orthodontic care is widely described as simultaneously over-supplied to those with little clinical need and under-supplied to those with much. Testing the first half of that claim requires a data source in which need is recorded independently of entitlement. We asked whether any such source exists, and, where need can be measured independently, how much of it remains untreated and how that residual is distributed socially.

Methods

We pre-registered four conditions under which population-level over-treatment is identified from a data source: need measured before treatment on the same individuals (I1); a sampling frame containing treated and untreated individuals (I2); need measurement not conditioned on treatment eligibility or reimbursement (I3); and treatment receipt observed irrespective of payer (I4). The pre-registered falsification rule was that if any source satisfied all four, the central claim would be reported as falsified. At reviewers' request, we replaced the original four-source convenience assessment with a documented search: 112 requests logged across eight frames, 15,341 records identified, and 14,139 records screened. Residual untreated occlusal need and its social gradient were estimated in a cross-sectional analysis of the Third National Health and Nutrition Examination Survey (NHANES III, 1988-1994) using a design-informed Bayesian hierarchical logistic model, cross-checked against Taylor-linearised design-based estimation.