Surgical Occlusion Setup in Correction of Skeletal Class III Deformity Using Surgery-First Approach: Guidelines, Characteristics and Accuracy

Abstract

The aims of this study were to establish guidelines for the surgical occlusion setup of surgery-first orthognathic surgery, and evaluate the resulting characteristics and accuracy. Skeletal Class III patients (N = 53) underwent Le Fort I osteotomy and bilateral sagittal split osteotomy. Study models before orthognathic surgery were set according to the guidelines. Occlusion was measured and computer-aided surgical simulation was used to evaluate the characteristics and accuracy of the surgical occlusion. The mean age of participants was 25 ± 6 years with 24 males and 29 females. The occlusion was set as positive overjet (4.4 ± 2.0 mm) and overbite (1.4 ± 1.8 mm), Class II or I molar relation, and posterior cross bite (overjet: 4.9 ± 2.0 mm and 4.4 ±1.9 mm, respectively for the right and left second molars) and open bite (overbite: -2.0 ± 1.6 mm and -1.9 ± 1.3 mm, respectively for the right and left second molars). Normal jaw relationship and symmetry were noted after virtual surgery. None of the patients required new occlusal setup. Our data contribute the use of the surgery-first approach for skeletal Class III patients by establishing guidelines for a surgical occlusion setup in three dimensions.

Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1

Dental casts showing surgical occlusion of a patient. (Top) Maxillary (left) and mandibular (right) casts; red indicates midlines. (Bottom) Surgical occlusion showing the coordination of the maxillary and mandibular jaw midlines; red indicates midlines.

Figure 2

Maxillary dental cast of a patient showing surgical occlusal contact on three segments and six teeth.

Figure 3

Computed tomography images used for linear and angular measurements of jaw symmetry. (Left) Horizontal deviation for maxilla (anterior nasal spine and upper incisor) and mandible (lower incisor and menton); ANS, anterior nasal spine; UI: upper incisor; LI: lower incisor; Me: menton. (Center) Vertical discrepancy for mandible (distance between point R and point L); point R: inflection point of mandibular body at the level of right mental foramen; point L: contralateral corresponding point of mandibular body on the left side. (Right) Horizontal discrepancy for mandible (distance discrepancy between dr and dl); dr: distance from point R to the facial midsagittal plane; dl: distance from point L to the facial midsagittal plane.

Figure 4

Computed tomography images used for volumetric measurements of jaw symmetry (volumetric discrepancy between right and left mandibular body).