Soo-Byung Park

Genome-wide Linkage Analysis of Mandibular Prognathism in Korean and Japanese Patients

The existence of familial aggregation of mandibular prognathism (MP) suggests that genetic components play an important role in its etiology. In this study, a genome-wide linkage analysis to identify loci susceptible to MP was conducted with 90 affected sibling-pairs in 42 families, comprised of 40 Korean sibling-pairs and 50 Japanese sibling-pairs. Two non-parametric linkage analyses, GENEHUNTER-PLUS and SIBPAL, were applied and detected nominal statistical significance of linkage to MP at chromosomes 1p36, 6q25, and 19p13.2. The best evidence of linkage was detected near D1S234 (maximum Zlr = 2.51, P = 0.0012). In addition, evidence of linkage was observed near D6S305 (maximum Zlr = 2.23, P = 0.025) and D19S884 (maximum Zlr = 1.93, P = 0.0089). Identification of the susceptible genes in the linkage regions will pave the way for insights into the molecular pathways that cause MP, especially overgrowth of the mandible, and may lead to the development of novel therapeutic tools.

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.

Effects of an Asian-specific nonsynonymous EDAR variant on multiple dental traits.

Dental morphology is highly diverse among individuals and between human populations. Although it is thought that genetic factors mainly determine common dental variations, only a few such genetic factors have been identified. One study demonstrated that a nonsynonymous single-nucleotide polymorphism (370V/A, rs3827760) in the ectodysplasin A receptor gene (EDAR) is associated with shoveling and double-shoveling grades of upper first incisors and tooth crown size. Here, we examined the association of EDAR 370V/A with several dental characters in Korean and Japanese subjects. A meta-analysis that combined analyses of Korean and Japanese subjects revealed that the Asian-specific 370A allele is associated with an increase in the grades of shoveling and double shoveling, as previously found. We also showed a highly significant association between EDAR 370V/A genotype and crown size, especially mesiodistal diameters of anterior teeth. Moreover, we found that the 370A allele was associated with the presence of hypoconulids of lower second molars. These results indicated that the EDAR polymorphism is responsible, in part, for the Sinodonty and Sundadonty dichotomy in Asian populations, and clearly demonstrated that the EDAR polymorphism has pleiotropic effects on tooth morphology. As the 370A allele is known to be a most likely target of positive selection in Asian populations, some phenotypes associated with the variant may be ‘hitchhiking phenotypes’, while others may be actual targets of selection.

Effect of Bimaxillary Surgery on Adaptive Condylar Head Remodeling: Metric Analysis and Image Interpretation Using Cone-Beam Computed Tomography Volume Superimposition

PURPOSE The aim of the present study was to use cone-beam computed tomography volume superimposition to investigate the effect of bimaxillary orthognathic surgery on condylar head remodeling. MATERIALS AND METHODS Using a retrospective study design, 2 investigators evaluated the cone-beam computed tomography data of subjects who had undergone Le Fort I osteotomy and mandibular setback surgery. The predictor variable was time, grouped as preoperative versus postoperative. The outcome variables were the measurement changes of the condylar heads and the distribution of the condylar head remodeling signs. Paired t and χ(2) tests were performed for the purposes of the 2-dimensional metric analysis and the condylar head remodeling distribution. P < .05 was considered significant. RESULTS The sample was composed of 22 adults (11 men and 11 women, age 20.3 ± 3.2 years) diagnosed with skeletal Class III malocclusion. The intra- and interoperator reliabilities of the image interpretation showed substantial agreement, according to Cohens kappa index. The condylar heights on the sagittal and coronal planes decreased after surgery. Bone resorption occurred predominantly in the anterior and superior areas on the sagittal plane, the superior and lateral areas on the coronal plane, and the anterolateral and posterolateral areas on the axial plane (P < .05). Bone formation was apparent only in the anteromedial area on the axial plane (P < .05). CONCLUSIONS Bimaxillary orthognathic surgery caused a decrease in the condylar heights and condylar head remodeling. The cone-beam computed tomography volume superimposition method showed that the condylar head had undergone remodeling after bimaxillary surgery.

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 analysis of midfacial soft tissue changes according to maxillary superior movement after horizontal osteotomy of the maxilla.

Three-dimensional diagnostic and treatment planning is a promising means of improving orthognathic surgical results from the standpoint of facial aesthetics. In such planning, cone-beam computed tomography is a useful tool. The purpose of the present study was to evaluate three-dimensional soft tissue changes in the midfacial region, with specific reference to post-Le Fort I osteotomy maxillary superior movement. Twenty-two patients underwent both Le Fort I osteotomy superior impaction and bilateral sagittal split ramus osteotomy of the mandible (ie, double-jaw surgery). Reference planes and 27 × 10 grids were used in evaluating the midfacial soft tissue areas. The extent of soft tissue change before and after surgery was calculated and analyzed. The results showed no statistical difference between the male and female subjects (P > 0.05). For both the male and the female patients after double-jaw surgery, the soft tissue in the triangular area, which includes both the nasolabial grooves and the upper lip, moved in the anterior direction and maxillary superiorly. It is essential that clinicians concerned about the management of soft tissue and the quality of treatment outcomes understand the pattern of soft tissue change after double-jaw surgery.

Midfacial soft-tissue changes after mandibular setback surgery with or without paranasal augmentation: cone-beam computed tomography (CBCT) volume superimposition.

The aim of this article is to compare the soft-tissue changes in the midfacial areas of patients who had undergone mandibular setback sagittal split ramus osteotomy (SSRO) with that of mandibular setback SSRO with paranasal augmentation. The subjects included 15 patients (group I), SSRO with paranasal augmentation and 20 patients (group II), SSRO alone. To evaluate the difference of the midfacial soft-tissue changes between groups, cone-beam computed tomography superimposition was utilized and the soft-tissue changes were measured both preoperatively and postoperatively by a 10 × 27 grid. In group I, the soft tissues were changed at the areas bounded superiorly by the infraorbital foramen, zygomatic eminence, posteriorly by the masseteric muscle and medially by the lateral aspect of the nose and following the nasolabial fold. In group II, the midfacial soft-tissue measurements were unchanged. This study may help clinicians to predict improvement in the midfacial region from mandibular setback SSRO with or without a paranasal augmentation procedure in class III deformities.

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.

Association of common PAX9 variants with permanent tooth size variation in non-syndromic East Asian populations

Studies on the heredity of dental characteristics in humans have indicated that the variance in many dental traits results from genetic variation. However, the genetic factors that influence commonly occurring dental variants are poorly understood. Paired domain box 9 (PAX9) codes a transcription factor that is important in tooth development. We investigated whether PAX9 polymorphisms are associated with normal variations in tooth agenesis and morphology. The study subjects were 273 Japanese and 223 Korean adults. Single-nucleotide polymorphisms (SNPs) in PAX9 (rs2295222, rs4904155, rs2073244, rs12881240 and rs4904210) were genotyped, and third molar agenesis and mesiodistal and buccolingual diameters were measured. We found that four of the five SNPs were significantly associated with the crown size. However, no SNP was associated with third molar agenesis. In additional analyses on non-metric dental traits, we found significant associations of PAX9 SNPs with shoveling of upper first incisors. In summary, common variants in PAX9 contributed to morphological variation in permanent teeth in humans.