Three-dimensional virtual operations can facilitate complicated surgical planning for the treatment of patients with jaw deformities associated with facial asymmetry: a case report
The patient was a 26-year-old man who had a class III jaw deformity with a cant occlusal plane cant, along with transverse discrepancy of the maxillary and mandibular dental arch widths (the maxillary width was larger than the mandibular width), associated with an open bite and facial asymmetry. Crowding of the front teeth, an open bite of the front teeth, deviation of the mandibular center to the left, and a left molar crossbite were also observed ().\nAlthough the maxillary premolar tooth was extracted, and the alignment of the row of teeth was good in the mandible with no tooth extraction, the transverse discrepancy of the dental arch width had not improved ().\nThe facial angle between the FH plane (Frankfort plane; Or–Po, Or: Orbitale—the most inferior anterior point on the orbit's margin, Po: Porion—the most superior point of the external acoustic meatus) and the facial plane (facial plane; N–Pog, N: Nasion—the midpoint of the frontonasal structure—the intersection of the internasal and frontonasal sutures in the midsagittal plane, Pog: Pogonion—the most anterior midpoint of the chin in the midsagittal plane) was larger on the right side, which measured 87.29°, than on the left side, which measured 83.02°. The distance from the FH plane to the maxillary first molar was greater on the right side, which measured 59.57 mm, than on the left side, which measured 55.60 mm; the angle between the facial median line and the occlusal plane was 84°, showing a cant upon counterclockwise rotation.\nThe median line of the mandible also showed a cant upon counterclockwise rotation ().\nUsing virtual operations with SimPlant OMS, we performed an LF1 osteotomy: cant and yaw correction on the maxilla; intraoral vertical ramus osteotomy (IVRO) on the right side of the mandible (the side without deviation); sagittal split ramus osteotomy (SSRO) fixed semirigidly with a sliding plate on the left side of the mandible (the side with deviation); mandibular constriction (MC); and mandibular border genioplasty (bone removal) in the mental region.\nCant correction and yaw correction were implemented in the maxilla, while mandibular midline osteotomy was implemented in the mandible to shorten the mandibular width (MC), with a setback of the mandible on the right side and extension of the mandibular ramus height (downward shift) on the left side.\nFurthermore, mandibular boarder osteotomy, including genioplasty due to bone removal, was planned for the asymmetry of the mandible angle/mental region that remained after osteotomy.\nThis stage was designed carefully to avoid trismus due to bone inference with the coronoid process and the zygomatic arch ().\nIt is important to evaluate the case from the lower side of the face in cases of facial asymmetry, in addition to implementing a design such that the left–right asymmetry of the mandibular border, which forms the facial outline, is prevented from moving in this direction ( and ).\nPresurgical and postsurgical facial changes were simulated by mapping a picture of the patient's facial profiles onto the soft tissue on the 3D-CT images. The asymmetry was improved in the front and lower areas, including the facial profile, following the surgery simulation.\nThe reduction of the mandibular width was measured, upon confirming the precise occlusal relationship after osteotomy, by optical scanning of the dental cast to link the data to the 3D-CT images.\nCant correction and yaw correction were implemented in the maxilla with a LeFort I osteotomy, and the right molar tooth was impacted in the upper area, resulting in complete down fracture, while Piezo Surgery (Mectron, Carasco, Italy) was applied for bone removal in the area surrounding the descending palatine artery.\nMC was implemented using two lag screws, following a mandibular midline osteotomy.\nSetback of the mandible with IVRO was performed on the right side of the mandible, and extension of the mandibular ramus height (downward shift) with SSRO was performed by semirigid fixation, using the sliding plate and one additional screw fixation on the left side of the mandible.\nFurthermore, bone removal in the distorted position was applied to the asymmetry in the mental region that remained following osteotomy (). The seating of the condyles was good postoperatively.\nWith regard to the presurgical and postsurgical evaluations of the frontal cephalogram, as no precise superimposition was possible due to the discordance of the upper and lower slant (rolling) of the face on the frontal cephalogram, an evaluation was undertaken by rotationally transferring the presurgical 3D-CT image to the location matching the postsurgical frontal cephalometric X-ray image ().\nAlthough the distance from the FH plane to the upper first molar was greater on the right side prior to surgery, the postsurgical distance was improved and was almost equal on both sides ().\nWith regard to the dental arch widths of the maxilla and mandible (the distance between the first molars), although the width of the mandible was greater than that of the maxilla presurgically, that of the mandible was improved to create a normal relationship (the maxillary width is larger than the mandibular width) postsurgically ().\nRegarding the positional relationship between the right and left mandibular angles and the facial midline, although the positional relationship between the right and left mandibular angles was larger on the left side than the right side presurgically, the postsurgical location was improved to being almost equal on both sides. Furthermore, the total was shortened from 114 mm to 105 mm. The presurgical intersecting degree of 95° was improved to a perpendicular angle of 90° postsurgically ().\nSubsequently, with regard to the positional relationship between the right and left mandibular angles and the mandibular midline, although the right side was larger presurgically, it was improved to being almost equal on both sides postsurgically. The presurgical intersecting degree of 86° was improved to a perpendicular angle of 89° postsurgically.\nThe superimpositions of the presurgical–postsurgical frontal cephalotraces are shown in . Upon superimposing the postsurgical mirror image of the half on the right side onto the other side (orange), it was confirmed that the postsurgical image (red) was close to bilateral symmetry ().\nThe summary of the results regarding the presurgical and postsurgical frontal cephalograms is shown in . The occlusal plane measured 9°, while the median mandible measured 14° upon CR (clockwise rotation) ().\nThe superimposition of the lateral cephalotrace is shown in (). It improved from class III to class I.\nThe splint was removed 1 month after surgery and was replaced with occlusal guidance, using only intermaxillary elastics.\nThe facial pictures 3 months after surgery confirmed that the asymmetry in the frontal view, as well as the profile view, was improved. The asymmetry was nearly in accordance with soft-tissue simulation (). Furthermore, even in the upward view, left-right symmetry was almost obtained, similar to the soft tissue simulation ().\nThe intraoral photographs 3 months after surgery showed the accordance of the median of the maxilla and mandible, obtaining a class I occlusal relationship ().\nIt was confirmed that the seating of the mandibular head was well maintained even 3 months after surgery, resulting from the reduction in interference with the osteotomized segments, as a result of the surgery to reduce the mandibular width (MC) ().\nThe facial pictures and intraoral photographs 1 year and 6 months after surgery confirmed that the improved soft tissue symmetry in the frontal view, the profile view, the class I occlusal relationship without an open bite, the accordance of the median of the maxilla and mandible and the right temporomandibular joint seating without temporomandibular joint symptoms were maintained ().