Identifying the optimal facial midsagittal plane: Harmonizing soft-tissue and skeletal references for precise incisor positioning in virtual surgery

In virtual orthognathic surgery, accurate upper incisor positioning relative to the facial soft-tissue midsagittal plane is essential. However, the optimal method for constructing this plane and its relationship to the skeletal midsagittal plane remain unclear. This study aimed to identify the optimal facial soft-tissue midsagittal plane and to establish clinical guidelines for reconciling soft-tissue and skeletal planes in virtual surgery. The study analyzed pretreatment records of 60 patients with skeletal Class III malocclusion (symmetric and asymmetric). Outcomes included root-mean-squared (RMS) distance and incisor deviation measurements to assess plane accuracy and alignment across various planes between groups. The Ex-Ex.midEn plane—defined by bilateral exocanthions and the midpoint of endocanthions—showed the lowest RMS distance in both groups, approximating the optimized plane. In the asymmetric group, incisor deviations varied significantly across plane types, with midEn-midTr-SubN < Ba-Na-ANS < Ex-Ex.midEn < FH⊥Ba-Na (mean difference ∼1 mm between pairs). Therefore, the Ex-Ex.midEn plane closely approximates the optimized midsagittal plane and is compatible with both Ba-Na-ANS and FH⊥Ba-Na within a 1 mm margin. Clinicians are advised to initially position the incisor using the skeletal midsagittal plane and adjust the resultant maxilla-mandibular complex position only if the discrepancy with the soft-tissue midsagittal plane exceeds 2 mm.