Comparison of Occlusion Using Conventional Versus Virtual Model Surgery in Segmental Maxillary Orthognathic Surgery Using the American Board of Orthodontics Discrepancy Index.

Background: Maxillary segmentation is essential for achieving optimal occlusion in some cases by correcting transverse discrepancies, Bolton's discrepancy, arch deformities, and alveolar angulation. Although traditional plaster model techniques are time-consuming and error-prone, many surgeons continue using them to set occlusion in segmental maxillary surgery despite the superior precision and outcomes of virtual surgical planning. Limited research has directly compared the clinical utility of virtual surgical planning-based segmentation versus traditional model surgery.

Purpose: The purpose of the study was to compare the planned occlusion obtained through conventional and virtual model surgeries performed on preoperative intraoral scans for segmental maxillary surgery.

Study design, setting, sample: An in vitro study was conducted using archived, de-identified preoperative intraoral scans from patients who underwent segmental maxillary surgery. Inclusion criteria were cases requiring a 3-piece Le Fort I osteotomy. Exclusion criteria included cases with partial edentulism or cleft palate.

Predictor variable: The predictor variable was the type of model surgery (conventional vs virtual) used for maxillary segmentation.

Main outcome variable(s): The primary outcome variable was planned occlusion outcomes measured using the American Board of Orthodontics (ABO) discrepancy index assessed by 2 orthodontists blinded to the model surgery technique used.

Covariates: None.

Analyses: Parametric statistical tests compared occlusal outcomes and planning times between methods. Two-tailed t-tests analyzed ABO index differences and planning times, with a significance level of P < .05.

Results: Two surgeons conducted both virtual and conventional model surgery for segmental maxillary procedures using random 20 intraoral scans, resulting in 80 final occlusions (40 conventional and 40 digitally planned). Two orthodontists evaluated each final bite using the ABO discrepancy index (160 assessments). The mean ABO discrepancy index was 9.99 (SD = 6.76) for conventional and 4.69 (SD = 4.60) for virtual planning, with a statistically significant difference of 5.30 (P < .001). Virtual planning was faster, with an average time reduction of 25 minutes and 28 seconds (SD = 5:34; P < .001).

Conclusions and relevance: The findings suggest that virtual model surgery outperforms conventional methods in achieving superior preoperative occlusal outcomes while reducing overall planning time.