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Influence of maxillomandibular ratio dynamics on post-pubertal sagittal classification: A retrospective historical
Rodrigo Oyonarte1, Mónica Valeria Castro2, Mackarena Sáez3
1Graduate Orthodontic Program, Facultad de Odontología, Universidad de Los Andes, Santiago, Chile; Doctoral Programme in Health Sciences, Escola de Doctorat, Universitat Internacional de Catalunya, Josep Trueta s/n08195 Sant Cugat del Vallès, Barcelona, Spain.
Background:
Cephalometric measurements, like the ANB or the Wits, enable sagittal skeletal classification; however, they can be affected by compensations, and the maxillomandibular differential may be subject to radiographic magnification. The maxillomandibular ratio (MxMdR) could provide a dynamic, magnification-independent intermaxillary sagittal assessment.
Aims:
To describe the MxMdR throughout facial development and assess its impact on determining post-pubertal sagittal classification.
Material And Methods:
Retrospective cohort study of 224 untreated individuals (AAOF-Craciofacial Growth Collection), including 1301 profile radiographs from 9 centers (1950s-1970s) with records spanning at least five stages of cervical maturation (CVS 1-6), classified based on final ANB and Wits (97 Class I, 82 Class II, 45 Class III). Measurements included the ANB, SNA, SNB, SN-GoGn, anterior facial height ratio, Wits, maxillary length, mandibular length, and MxMdR. Statistical analysis involved descriptive statistics, mixed models to assess developmental variations, and LASSO regression to identify early-stage predictors for the post-pubertal ANB angle.
Results:
No significant differences were observed between sexes in sagittal measurements. MxMdR decreased progressively and significantly during growth, showing a class-specific distribution similar to ANB, while Wits decreased in Class III, remained stable in Class I, and increased in Class II individuals. LASSO regression identified initial ANB and MxMdR as key predictors for the post-pubertal ANB.
Conclusions:
MxMdR evolves differently across skeletal classes, correlating with the final sagittal classification at all developmental stages. Including it alongside the initial ANB improves predictions of post-pubertal relationships. The MxMdR serves as a valuable, magnification-independent tool for early skeletal assessment, complementing traditional diagnostic methods.
