Woo-Sung Son

Cone-beam computed tomography evaluation of short- and long-term airway change and stability after orthognathic surgery in patients with Class III skeletal deformities: bimaxillary surgery and mandibular setback surgery

The purpose of this study was to evaluate the volumetric change of the upper airway space in 36 Class III patients who had undergone bimaxillary surgery or isolated mandibular setback, and, further, to analyse the relation between post-surgical stability and airway change using cone-beam computed tomography (CBCT). A three-dimensional (3D) CBCT examination was performed at three stages: T0 (before surgery), T1 (an average of 4.6 months after surgery), and T2 (an average of 1.4 years after surgery). The results showed that the volumes of the oropharyngeal and hypopharyngeal airways decreased significantly 4.6 months post-surgery in the mandibular setback group (p<0.05), and these diminished airways had not recovered 1.4 years post-surgery. In the bimaxillary surgery group, the volume of the oropharyngeal airway also decreased. A Spearman correlation analysis showed that the anteroposterior length of the hypopharyngeal area had a correlation with post-surgical stability in the isolated mandibular surgery group, and that the cross-sectional area of the nasopharynx was correlated with maxillary relapse only in the bimaxillary surgery group (p<0.05).

Cone-beam computerized tomography evaluation of condylar changes and stability following two-jaw surgery: Le Fort I osteotomy and mandibular setback surgery with rigid fixation

OBJECTIVES The purpose of this study was to compare the changes of the condylar axis, the anteroposterior condylar position relative to the glenoid fossa, and post-2-jaw surgery stability. STUDY DESIGN All of the patients (12 male, 14 female) were assessed by cone-beam computerized tomography (CBCT) before surgery, after surgery, and at follow-up. CBCT images were referenced to assess skeletal stability, the condylar axis change, and the anteroposterior condylar position in the glenoid fossa. A repeated-measures analysis of variance (P = .05) also was performed. RESULTS The skeletal changes between postsurgery and follow-up (P < .05) were insignificant. Both the axial condylar angles and the anteroposterior condylar position significantly differed among the groups (P < .05). CONCLUSIONS After surgery, the coronal condylar axis was rotated inward. The anteroposterior condylar position in the glenoid fossa had moved from the anterior to the concentric position, tending to return slightly toward the original position. These changes did not negatively affect the stability.

Midfacial Soft-Tissue Changes After Advancement of Maxilla With Le Fort I Osteotomy and Mandibular Setback Surgery: Comparison of Conventional and High Le Fort I Osteotomies by Superimposition of Cone-Beam Computed Tomography Volumes

PURPOSE To compare the soft-tissue changes in the midfacial areas of patients who underwent conventional and high Le Fort I osteotomies with maxillary advancement, using voxel-by-voxel registration at the cranial bases, and to evaluate the influence of the level of the osteotomy cut on those soft-tissue changes. MATERIALS AND METHODS The subjects included 42 patients (28 in group 1 and 14 in group 2) who had undergone conventional or high Le Fort I osteotomy with maxillary advancement and mandibular setback sagittal split ramus osteotomy. Using the method involving superimposition of 3-dimensional cone-beam computed tomography volumes, we evaluated the soft-tissue changes preoperatively and postoperatively. The midfacial area was measured with a 10 × 27 grid at 4.5-mm (vertical) and 5-mm (horizontal) intervals. RESULTS The maxillary advancement in group 1 averaged 3.35 ± 1.06 mm at the A-point and 3.23 ± 0.98 mm at the same location in group 2. Both of the Le Fort I osteotomies induced an overall hard-to-soft tissue response in the midfacial area (P < .05). CONCLUSIONS In group 1, the distinctly changed soft tissue was marked near the osteotomy line and upper lip. The distribution of the changed points was within a roughly triangular area between the 2 nasolabial folds and the upper lip. In group 2, the soft-tissue changes were concentrated just below the infraorbital foramen. The distribution of the affected soft tissue after the high Le Fort I osteotomy was within the rectangular malar region between the 2 infraorbital foramens and the upper lip.

Alveolar bone loss around lower incisors during surgical orthodontic treatment in mandibular prognathism.

OBJECTIVES To evaluate the alveolar bone loss around lower incisors incurred during surgical orthodontic treatment in individuals with mandibular prognathism. MATERIALS AND METHODS The samples consisted of 25 patients (13 men, 12 women; mean ages: 26.3 ± 2.7 years) treated with jaw surgery and orthodontic treatment. Lateral and frontal cephalograms and cone-beam computed tomography (CBCT) images of the patients were obtained before treatment (T0) and after presurgical orthodontic treatment (T1) and after debonding (T2). After measurement of variables, repeated-measures analysis of variance with Bonferronis multiple comparison test and Pearson and Spearman correlation analysis were performed. RESULTS The lower central and lateral incisors showed that the vertical alveolar bone level and the alveolar bone thickness of the labial and lingual plates were reduced after presurgical orthodontic treatment but were not deteriorated during postsurgical orthodontic treatment. CONCLUSION Excessive forward movement of lower incisors during presurgical orthodontic treatment could cause alveolar bone loss around the lower incisors; thus, special care should be considered in individuals with mandibular prognathism.

Three-dimensional evaluation of midfacial asymmetry in patients with nonsyndromic unilateral cleft lip and palate by cone-beam computed tomography

Objective To compare three-dimensionally the midfacial hard- and soft-tissue asymmetries between the affected and the unaffected sides and determine the relationship between the hard tissue and the overlying soft tissue in patients with nonsyndromic complete unilateral cleft lip and palate (UCLP) by cone-beam computed tomography (CBCT) analysis. Methods The maxillofacial regions of 26 adults (18 men, 8 women) with nonsyndromic UCLP were scanned by CBCT and reconstructed by three-dimensional dental imaging. The frontal-view midfacial analysis was based on a 3 × 3 grid of vertical and horizontal lines and their intersecting points. Two additional points were used for assessing the dentoalveolar area. Linear and surface measurements from three reference planes (Basion-perpendicular, midsagittal reference, and Frankfurt horizontal planes) to the intersecting points were used to evaluate the anteroposterior, transverse, and vertical asymmetries as well as convexity or concavity. Results Anteroposteriorly, the soft tissue in the nasolabial and dentoalveolar regions was significantly thicker and positioned more anteriorly on the affected side than on the unaffected side (p < 0.05). The hard tissue in the dentoalveolar region was significantly retruded on the affected side compared with the unaffected side (p < 0.05). The other midfacial regions showed no significant differences. Conclusions With the exception of the nasolabial and dentoalveolar regions, no distinctive midfacial hard- and soft-tissue asymmetries exist between the affected and the unaffected sides in patients with nonsyndromic UCLP.

Cone-beam computed tomographic evaluation of the condylar remodeling occurring after mandibular set-back by bilateral sagittal split ramus osteotomy and rigid fixation

Objective To evaluate condylar head remodeling after mandibular set-back sagittal split ramus osteotomy (SSRO) with rigid fixation in skeletal class III deformities. The correlation between condylar head remodeling and condylar axis changes was determined using cone-beam computed tomography (CBCT) superimposition. Methods The CBCT data of 22 subjects (9 men and 13 women) who had undergone mandibular set-back SSRO with rigid fixation were analyzed. Changes in the condylar head measurements and the distribution of the signs of condylar head remodeling were evaluated by CBCT superimposition. Results The subjects showed inward rotation of the axial condylar angle; reduced condylar heights on the sagittal and coronal planes; and resorptive remodeling in the anterior and superior areas on the sagittal plane, superior and lateral areas on the coronal plane, and anterior-middle and anterior-lateral areas on the axial plane (p < 0.05). Conclusions The CBCT superimposition method showed condylar head remodeling after mandibular set-back SSRO with rigid fixation. In skeletal class III patients, SSRO with rigid fixation resulted in rotation, diminution, and remodeling of the condylar head. However, these changes did not produce clinical signs or symptoms of temporomandibular disorders.

Treatment of an ankylosed maxillary incisor by intraoral alveolar bone distraction osteogenesis.

An ankylosed tooth and adjacent alveolar process can lead to the development of an open bite, an unesthetic smile line, and abnormal function in mastication. Intraoral alveolar bone distraction osteogenesis is an option for treating an ankylosed tooth. The purpose of this clinical report was to show the treatment of a growing patient with an ankylosed maxillary central incisor. A simple tooth-borne intraoral distractor was made with an expansion screw and 0.9-mm stainless steel wire, which enabled it to move easily. Intraoral alveolar bone distraction osteogenesis will give the best results in patients with favorable root length and severely resorbed alveolar bone in the vertical dimension.

Effect of post-orthognathic surgery condylar axis changes on condylar morphology as determined by 3-dimensional surface reconstruction.

OBJECTIVE To evaluate the effect of postoperative condylar axis changes on mandibular condylar remodeling by comparing the condylar head in three-dimensional (3D) surface reconstructions before and after surgery in skeletal Class III deformities (one-jaw [mandibular setback] or two-jaw surgery), and also to determine the relationship between condylar inward rotation and condylar surface remodeling after orthognathic surgery. MATERIALS AND METHODS A retrospective analysis was conducted of 30 patients with skeletal Class III deformities who had received orthognathic surgery. Group 1 underwent one-jaw surgery (10 men, five women, age 22.4 ± 3.3 years), and group 2 underwent two-jaw surgery (10 men, five women, age 22.3 ± 2.2 years). Sixty condyles were reconstructed and superimposed pre- and postoperatively to compare the changes of condylar surfaces. The relation between the condylar axis change and the surface change using the Pearson correlation were investigated from the 3D image software. RESULTS Condylar surface changes before and after the surgery were significant. The postoperative inward rotation of the condyles was correlated with the average absolute deviation of the condyles, regardless of the surgery type (one- or 2-jaw surgery; r  =  .70, P < .05). CONCLUSION After orthognathic surgery, condylar surface changes occurred, and condylar inward rotation was closely related to changes of condylar surface.

Relationship between chin deviation and the position and morphology of the mandible in individuals with a unilateral cleft lip and palate

Objective In this study, we aimed to examine the relationship between chin deviation and the positional and morphological features of the mandible and to determine the factors that contributed to chin deviation in individuals with a unilateral cleft lip and palate (UCLP). Methods Cone-beam computed tomography (CBCT) images of 28 adults with UCLP were analyzed in this study. Segmented three-dimensional temporomandibular fossa and mandible images were reconstructed, and angular, linear, and volumetric parameters were measured. Results For all 28 individuals, the chin was found to deviate to the cleft side by 1.59 mm. Moreover, among these 28 individuals, only 7 showed distinct (more than 4 mm) chin deviation, which was toward the cleft side. Compared to the non-cleft side, the mandibular body length, frontal ramal inclination, and vertical position of the condyle were lower and inclination of the temporomandibular fossa was steeper on the cleft side. Furthermore, the differences in inclination of the temporomandibular fossa, mandibular body length, ramus length, and condylar volume ratio (non-deviated/deviated) were positively correlated with chin deviation. Conclusions UCLP individuals show mild chin deviation to the cleft side. Statistical differences were noted in the parameters that represented positional and morphological asymmetries of the mandible and temporomandibular fossa; however, these differences were too small to indicate clinical significance.

New bimaxillary orthognathic surgery planning and model surgery based on the concept of six degrees of freedom

The aim of this paper was to propose a new method of bimaxillary orthognathic surgery planning and model surgery based on the concept of 6 degrees of freedom (DOF). A 22-year-old man with Class III malocclusion was referred to our clinic with complaints of facial deformity and chewing difficulty. To correct a prognathic mandible, facial asymmetry, flat occlusal plane angle, labioversion of the maxillary central incisors, and concavity of the facial profile, bimaxillary orthognathic surgery was planned. After preoperative orthodontic treatment, surgical planning based on the concept of 6 DOF was performed on a surgical treatment objective drawing, and a Jeons model surgery chart (JMSC) was prepared. Model surgery was performed with Jeons orthognathic surgery simulator (JOSS) using the JMSC, and an interim wafer was fabricated. Le Fort I osteotomy, bilateral sagittal split ramus osteotomy, and malar augmentation were performed. The patient received lateral cephalometric and posteroanterior cephalometric analysis in postretention for 1 year. The follow-up results were determined to be satisfactory, and skeletal relapse did not occur after 1.5 years of surgery. When maxillary and mandibular models are considered as rigid bodies, and their state of motion is described in a quantitative manner based on 6 DOF, sharing of exact information on locational movement in 3-dimensional space is possible. The use of JMSC and JOSS will actualize accurate communication and performance of model surgery among clinicians based on objective measurements.