Mandibular autorotation: a critical virtual parameter in clinical decision-making regarding maxilla-first versus mandible-first sequence.

ABSTRACT

Large degrees of mandibular autorotation during intermediate splint design are prone to transfer error and decrease accuracy. The purpose of this study was to evaluate the amount of mandibular autorotation necessary to design intermediate splints for maxilla- and mandible-first sequences using virtual planning software, to help the clinical decision-making regarding the most adequate sequence for each patient. The influence of specific orthognathic movements (different vertical and sagittal changes at the Le Fort I level, cant correction) and the type of maxillofacial deformity (skeletal Class II, III, anterior open bite) were evaluated to identify those that would require higher levels of autorotation for each sequence. Three-dimensional virtual surgical planning data of 194 patients were reviewed (126 female, 68 male; mean age 26.5 ± 11.0 years; 143 skeletal Class II, 51 skeletal Class III) and subgroup analyses were conducted using the Kruskal-Wallis test and post-hoc pairwise comparisons. As an additional parameter (mandibular autorotation), maxilla-first is indicated for bimaxillary osteotomies with Le Fort I posterior intrusion, anterior open bite, and skeletal Class III, while mandible-first is recommended for Le Fort I global extrusion, especially with maxillary cant correction.