Predicting The Outcome Of Comprehensive Occlusal And Temporomandibular Rehabilitation In Adults With Class II Malocclusion: Development And Internal Validation Of A Weighted Four-Domain Compensatory-Reserve Index

Abstract

Objective. Angle’s classification describes the occlusal contact but does not define how much dentoalveolar movement an adult can absorb, nor how the condylar position constrains the mechanics that may be used. The study aimed to identify pre-treatment determinants of a stable occlusal and temporomandibular result in adults with Class II malocclusion and to develop, weight and internally validate an interpretable prognostic index of dentoalveolar compensatory reserve.

Materials and Methods. A single-centre observational cohort of 129 adults aged 18–45 years with completed facial growth was stratified before outcome assessment into four clinical–morphological groups: dentoalveolar (n = 41), skeletal–dentoalveolar with mandibular retrognathism (n = 47), hypodivergent Class II division 2 (n = 26) and complicated forms (n = 15). Every patient underwent clinical, digital-model, lateral cephalometric, cone-beam computed tomographic (CBCT) and periodontal examination. CBCT quantified the Pullinger–Hollender condylar position index, its inter-side difference, intercondylar and intergonial width, and mandibular spatial asymmetry. The composite unfavourable endpoint at 24 months of retention combined occlusal relapse, incisor irregularity, new clinically relevant recession and forced abandonment of planned movement. The cohort was split, with strata preserved, into a development sample (n = 89) and a validation sample (n = 40).

Results. The unfavourable endpoint occurred in 38.2 % of the development and 37.5 % of the validation sample. Univariable odds ratios were highest for periodontal phenotype (OR = 3.43), Jarabak ratio (3.39), dehiscence and fenestration (3.18) and buccal plate thickness (2.71). After collapsing collinear variables into four domain modules, all remained independent (Nagelkerke R² = 0.49); the vertical and periodontal–alveolar modules carried the largest standardised coefficients (β = 0.34 and 0.32). The resulting weighted index (0.18·M1 + 0.30·M2 + 0.24·M3 + 0.28·M4) reached an area under the ROC curve of 0.86 (95 % CI 0.77–0.93), exceeding every single module. Across the three prognostic bands the unfavourable outcome rose from 9.7 % to 31.8 % and 66.7 % (trend p < 0.001). In the validation sample accuracy was 82.5 %, sensitivity 80.0 %, specificity 84.0 %, calibration slope 0.93. Where the delivered tactic matched the index recommendation, 24-month stability was 87.5 % versus 56.3 % (p = 0.034) and biologically risky incisor movement 8.3 % versus 43.8 % (p = 0.012).

Conclusions. Stability of comprehensive occlusal and temporomandibular rehabilitation in Class II adults is governed less by the magnitude of the sagittal discrepancy than by the vertical and periodontal–alveolar reserve available to compensate it. A four-domain weighted index computed before appliance placement separates favourable from unfavourable courses with good discrimination and calibration, and its dominant module converts the numerical grade into a specific mechanical restriction.