Repeatability and Geometric Sensitivity of Digital Mandibular Displacement Measurements in Orthodontic Records

Digital mandibular displacement measurements require estimates of variability before small differences can be interpreted. In this secondary methodological analysis, we assessed the same-examiner agreement of stored digital centric-relation–maximum-intercuspation (CR–MIP) measurements and examined defined geometric sensitivities. Four anterior mandibular sites were measured twice, two weeks apart, by the same examiner using stored records from 14 patients in a doctoral cohort. The principal summary was the four-site mean. Analyses included an absolute-agreement intraclass correlation coefficient, ICC(A,1), patient-level bootstrap confidence intervals, Bland–Altman limits of agreement, standard error of measurement (SEM), and minimal detectable change (MDC95). Separate rigid-body calculations examined axis translation, closure to first contact, and landmark correspondence. Session means were 1.473 and 1.421 mm; ICC(A,1) was 0.915 (95% confidence interval, 0.761–0.972), bias −0.052 mm, SEM 0.238 mm, MDC95 0.661 mm, and limits of agreement −0.713 to 0.609 mm. At a retained 3° closure angle, a specified 5 mm perpendicular axis offset produced a calculated point-position change of 0.262 mm. Recalculating first contact could alter the closure angle and active contact. High relative reliability coexisted with appreciable absolute variation. Whether closure and landmark selection were repeated was undocumented; the estimates therefore do not establish repeatability of the complete measurement procedure, clinical accuracy or full-workflow reproducibility.