Inter-method agreement between digital occlusograms and mounted-cast articulator analysis in temporomandibular disorders with degenerative joint changes

Abstract

Intraoral scanner occlusograms are increasingly used for non-invasive digital occlusal analysis, yet their agreement with an articulator-mounted reference in temporomandibular disorder (TMD) patients with degenerative joint changes is unknown. This is a methodological question about the fidelity of digital occlusal recording in a population with altered occlusal anatomy, not a claim that occlusal factors cause TMD or that occlusal adjustment treats it. This study aimed to quantify per-cusp inter-method agreement between an iTero Element 5D Occlusogram and a semi-adjustable articulator with 8 μm articulating paper on identical mounted casts, and to compare agreement between TMD patients with cone-beam computed tomography (CBCT)-confirmed degenerative joint changes and Class I controls. Sixty adults (30 TMD with DC/TMD Axis I and CBCT-confirmed degenerative joint changes; 30 Class I controls selected to have comparable age and sex distributions) had Type IV stone casts mounted on a SAM 3 articulator in centric relation, recorded with the Dawson bimanual manipulation technique; after removal of the interocclusal record the articulator was closed until the mounted casts came into occlusal contact, and the incisal pin was locked to preserve that standardised position; both methods were then read with the casts held in it. Two operators, blinded to study-group allocation during their respective occlusal assessments, classified 12,718 cusp/surface sites on identical casts using 8 μm Arti-Fol (reference) and the iTero Element 5D Occlusogram (index). The Occlusogram threshold was selected by maximising pooled Cohen’s κ, Matthews correlation coefficient (MCC), and F1 score. Group comparisons were adjusted for within-patient clustering using a patient-level generalised estimating equation (GEE) and per-patient nonparametric tests. At the optimised ≤ 0.2 mm threshold, inter-method agreement fell from substantial in controls to fair in TMD patients (Cohen’s κ 0.636 vs. 0.392; p = 2.5 × 10⁻⁶). Sensitivity decreased by 20.1% points in TMD (93.16% vs. 73.08%) and positive predictive value by 21.2 points (49.32% vs. 28.15%; both p < 0.001); specificity and negative predictive value remained high (≥ 96.9% and ≥ 99.5%, respectively) and overall accuracy was 96.51% in TMD and 98.11% in controls. Both reductions persisted after adjustment for within-patient clustering (GEE odds ratio 0.17 [95% CI 0.05–0.62]; p = 0.007 for sensitivity and 0.51 [0.30–0.89]; p = 0.017 for positive predictive value). False positives clustered predominantly at mandibular incisal edges. Even under controlled mounted-cast conditions, agreement between the iTero Occlusogram and the articulator-mounted reference dropped from substantial in controls to fair in TMD patients with degenerative joint changes, driven by reduced sensitivity relative to the articulating-paper comparator. Digital occlusograms should therefore be interpreted with caution when accurate static contact information is required in this population, and confirmation with a physical occlusal indicator on mounted casts may be advisable before irreversible restorative procedures. These findings concern the fidelity of digital occlusal recording and do not bear on the aetiology or management of TMD itself.