Yoonji Kim

Contribution of Nuclear Factor of Activated T Cells c1 to the Transcriptional Control of Immunoreceptor Osteoclast-associated Receptor but Not Triggering Receptor Expressed by Myeloid Cells-2 during Osteoclastogenesis

Bone homeostasis depends on the coordination of osteoclastic bone resorption and osteoblastic bone formation. Receptor activator of NF-κB ligand (RANKL) induces osteoclast differentiation through activating a transcriptional program mediated by the key transcription factor nuclear factor of activated T cells (NFAT) c1. Immunoreceptors, including osteoclast-associated receptor (OSCAR) and triggering receptor expressed by myeloid cells (TREM)-2, constitute the co-stimulatory signals required for RANKL-mediated activation of calcium signaling, which leads to the activation of NFATc1. However, it remains unknown whether the expression of immunoreceptors are under the control of NFATc1. Here we demonstrate that the expression of OSCAR, but not that of TREM-2, is up-regulated during osteoclastogenesis and markedly suppressed by the calcineurin inhibitor FK506, suggesting that OSCAR is transcriptionally regulated by NFATc1. NFATc1 expression results in the activation of the OSCAR promoter, which was found to be further enhanced by co-expression of PU.1 and microphthalmia-associated transcription factor (MITF). We further provide evidence that NFATc1 specifically regulates OSCAR by chromatin immunoprecipitation assay and quantification of OSCAR and TREM-2 mRNA in NFATc1-/- cells. Thus, OSCAR but not TREM-2 is involved in the positive feedback loop of the immunoreceptor-NFATc1 pathway during osteoclastogenesis. Although several immunoreceptors have been identified as co-stimulatory molecules for RANKL, the expression and function are differentially regulated. These mechanisms, possibly together with the delicate regulation of their ligands on osteoblasts, may provide the exquisite machinery for the modulation of osteoclastogenesis in the maintenance of bone homeostasis.

Effects of the Taper Shape, Dual-Thread, and Length on the Mechanical Properties of Mini-Implants

OBJECTIVE To analyze the mechanical effects of the length and the various shapes such as cylindrical shape, taper shape, and dual-thread shape on the insertion and removal torque of mini-implants. MATERIALS AND METHODS Mini-implants (diameter 1.6 mm and length 6 mm and 8 mm) consisting of cylindrical, taper, and dual-thread groups were inserted and removed in Sawbones while measuring the torque and time. Mechanical analysis was done of maximum insertion torque (MIT), maximum removal torque (MRT), torque ratio (TR; MRT/MIT), insertion angular momentum (IAM), removal angular momentum (RAM), and time of MIT. Measurements were statistically evaluated to analyze any differences of shapes and lengths. RESULTS The cylindrical shape had the lowest MIT and MRT in each length. Although taper shape showed the highest MIT in each length, dual-thread shape showed significantly higher MRT, TR, and RAM in each length (P < .05). Dual-thread groups showed a gentle increase of insertion torque and a gentle decrease of removal torque in contrast to the other shape groups. However, it had higher IAM and time of MIT. The long length group showed significantly higher measurements except for TR. CONCLUSIONS Dual-thread shape provided better mechanical stability with high removal torque on the broad range than other shapes. However, dual-thread shape may need improvement for reducing the long insertion time to decrease the stress to the surrounding tissue.

Alveolar Bone Loss around Incisors in Surgical Skeletal Class III Patients

OBJECTIVE To test the hypothesis that there is no difference in the vertical alveolar bone levels and alveolar bone thickness around the maxillary and mandibular central incisors in surgically treated skeletal Class III malocclusion patients. MATERIALS AND METHODS The study sample comprised 20 Korean patients with skeletal Class III malocclusion with anterior crossbite and openbite (9 male, 11 female, mean ages 24.1). Three-dimensional cone beam computed tomography images were taken at least 1 month before the orthognathic surgery, and sagittal slices chosen at the labio-lingually widest point of the maxillary and mandibular right central incisor were evaluated. Measurement of the amount of vertical alveolar bone levels and alveolar bone thickness of the labial and lingual plate at the root apex was made using the SimPlant Pro 12.0 program. RESULTS The mandibular incisors showed reduced vertical alveolar bone levels than the maxillary incisors, especially on the lingual side. The alveolar bone thickness was significantly greater on the lingual side in the maxillary incisors, whereas the mandibular incisors exhibited an opposite result (P < .05). The percentage of vertical bone loss to root length showed a statistically significant difference between the upper labial and lower labial alveolar bone and also between the upper lingual and lower lingual alveolar bone, showing more bone loss in the lower incisors (P < .001). CONCLUSIONS The hypothesis is rejected. For the skeletal Class III patients undergoing orthognathic surgery, special care should be taken to prevent or not aggravate preexisting alveolar bone loss in the anterior teeth, especially in the mandible.

Comparison of alveolar bone loss around incisors in normal occlusion samples and surgical skeletal class III patients.

OBJECTIVE To test the hypothesis that there is no difference in vertical alveolar bone loss and alveolar bone thickness around maxillary and mandibular central incisors in normal occlusion samples and skeletal Class III malocclusion patients. MATERIALS AND METHODS The study sample comprised 20 Korean normal occlusion subjects (mean age, 22.1 years; group 1) and patients with skeletal Class III malocclusion with anterior open bite (mean age, 22.4 years; group 2). Three-dimensional (3D) cone beam computed tomography (CBCT) images were taken before orthodontic treatment, and sagittal slices chosen at the labio-lingually widest point of the maxillary and mandibular right central incisor were evaluated, respectively. The amount of vertical alveolar bone loss and/or alveolar bone thickness of the labial and lingual plate at the root apex were measured. RESULTS Group 2 had statistically significant more vertical bone loss than group 1 (P < .05). Alveolar bone at the apex was significantly thinner in group 2 (P < .05), except for the maxillary incisors. Mandibular incisors showed greater alveolar bone loss than was seen in maxillary incisors in both groups, especially at the lingual side in group 2 (P < .05). Overall, alveolar bone thickness at the apex was wider than cementoenamel junction (CEJ) width, except for the mandibular incisors in group 2, for which the percentage was 81.33%. CONCLUSIONS The hypothesis is rejected. Special care should be taken to avoid aggravating preexisting alveolar bone loss in the anterior teeth, especially in the mandible, in skeletal Class III patients, who may be more vulnerable to alveolar bone loss during orthodontic treatment.

Three-dimensional changes of the hyoid bone and airway volumes related to its relationship with horizontal anatomic planes after bimaxillary surgery in skeletal Class III patients

OBJECTIVE To evaluate longitudinal changes of the hyoid bone position and pharyngeal airway space after bimaxillary surgery in mandibular prognathism patients. MATERIALS AND METHODS Cone-beam computed tomography scans were taken for 25 mandibular prognathism patients before surgery (T0), 2 months after surgery (T1), and 6 months after surgery (T2). The positional displacement of the hyoid bone was assessed using the coordinates at T0, T1, and T2. Additionally, the volume of each subjects pharyngeal airway was measured. RESULTS The mean amount of posterior maxilla impaction was 3.76 ± 1.33 mm as the palatal plane rotated 2.04° ± 2.28° in a clockwise direction as a result of bimaxillary surgery. The hyoid bone moved backward (P < .05, P < .001) and downward (P > .05, P < .05) at 2 months and 6 months after surgery, while the total volume of the pharyngeal airway significantly decreased at the same time points (P < .001, P < .001). There was significant relationship between the changes of the hyoid bone position and airway volume at 2 months after surgery (P < .05). The change of the palatal plane angle was positively correlated to the decrease in the total airway volume (P < .001). CONCLUSIONS The null hypothesis was rejected. The hyoid bone moved inferoposteriorly, and the pharyngeal airway volume decreased for up to 6 months after bimaxillary surgery. The decrease in the pharyngeal airway volume was correlated to the changes in the palatal plane inclination and the positional change of the hyoid bone.

Early Correction of a Developing Skeletal Class III Malocclusion

This case report describes the treatment of a Japanese girl aged 11 years 10 months who had a severe Class III malocclusion with a concave facial profile. She presented hypodivergent skeletal pattern with a -4.0-mm anterior crossbite and a deep overbite. She also had facial asymmetry attributed partly to the lateral mandibular shift to avoid incisal interferences. The treatment plan included a monoblock appliance, rapid palatal expansion, and fixed edgewise appliances at the final stage. The monoblock appliance was used to redirect the growth of the mandible to a clockwise direction and simultaneously correct the incisal relationships along with fixed edgewise appliances. Good incisal relationships were achieved, and facial esthetics was greatly improved after 28 months of treatment. Stability of the treatment result was excellent in the 3-year 9-month follow-up at the age of 18.

Assessment of asymmetry in a normal occlusion sample and asymmetric patients with three-dimensional cone beam computed tomography A study for a transverse reference plane

OBJECTIVE To characterize symmetrical features of patients with facial asymmetry and thus to find the most reliable horizontal reference lines easily used in three-dimensional images. The hypothesis was that there is a difference in the location of bilateral landmarks of the upper skull between the normal occlusion sample and skeletal Class III patients with asymmetry. MATERIALS AND METHODS Group 1 (normal occlusion sample) was composed of 20 Korean adults with normal occlusion and no noticeable asymmetry. Groups 2 through 4 were selected from patients who were diagnosed as skeletal Class III malocclusion and grouped according to the extent of asymmetry (group 2: symmetric mandible, no maxillary cant; group 3: asymmetric mandible, no maxillary cant; group 4: asymmetric mandible, more than 4 mm maxillary cant measured at maxillary first molars). Three-dimensional cone beam computed tomography images were taken before treatment, and bilateral landmarks of the skull were located and their vertical and horizontal differences compared. RESULTS No statistically significant difference was noted in the position of bilateral landmarks between groups, except for AG (P < .05). AG showed significant differences in vertical dimension (P < .001) and in horizontal dimension (P < .0001) between groups. The mean of the difference was clearly greatest at FM. CONCLUSIONS The hypothesis is rejected. All groups had a similar pattern of asymmetry in the upper third of the face. Therefore, the transverse reference line of the bilateral Z or orbitale may be used even in patients with severe asymmetry of the maxilla with reference to the clinical photos.

Skeletal and dental effects of molar distalization using a modified palatal anchorage plate in adolescents

OBJECTIVE To evaluate and compare skeletal effects and the amount of molar distalization in maxilla using modified palatal anchorage plate (MPAP) vs headgear appliances in adolescent patients. MATERIALS AND METHODS Pre- and posttreatment lateral cephalograms of 45 Class II malocclusion patients were analyzed; 24 were treated with MPAP appliances (age, 12.4 years) and 21 with headgear (age, 12.1 years). Fixed orthodontic treatment started with the distalization process in both groups. Thirty-two variables were measured and compared between both groups using multivariate analysis of covariates. RESULTS There was no significant main effect of the appliance type on the treatment results (P  =  .063). Also, there was no significant main effect of the appliance type on both pre- and posttreatment comparisons (P  =  .0198 and .135, respectively). The MPAP and headgear groups showed significant distalization of maxillary first molars (3.06 ± 0.54 mm and 1.8 ± 0.58 mm, respectively; P < .001). Sagittal skeletal maxillomandibular differences were improved after treatment (P < .001), with no significant differences between the two groups. No significant difference in treatment duration was found between the groups. CONCLUSIONS The MPAP showed a significant skeletal effect on the maxilla. Both MPAP and headgear resulted in distalization of maxillary first molars. Therefore, it is recommended that clinicians consider the application of MPAP, especially in noncompliant Class II patients.

Three-dimensional evaluation of maxillary dentoalveolar changes and airway space after distalization in adults

OBJECTIVES To evaluate the changes in position of the maxillary dentition and the airway space after distalization using a modified C-palatal plate (MCPP) in adult patients through CBCT images and to analyze the relationship between the amount of distalization and the changes in the airway space. MATERIALS AND METHODS CBCT images of 33 adult Class II patients (22.2 ± 4.0 years old; 27 women and 6 men) treated by total maxillary arch distalization using the MCPP were evaluated before and after distalization. The patients were divided into nonextraction and extraction groups. The changes in the airway space as well as the changes in the positions of the maxillary dentition were evaluated. The distalization effects were calculated and assessed using paired t-tests. RESULTS After distalization, the first molar showed significant distalization and intrusion ( P < .001) with no significant rotation of the crown and no significant buccal displacement of its root in the transverse dimension. There were no significant changes in the airway volume or the minimum cross-sectional area of the oropharynx. CONCLUSIONS The application of the MCPP resulted in significant total arch distalization without a significant effect on the transverse dimensions or changes in the oropharynx airway space. The MCPP can be considered a viable treatment option for patients with Class II malocclusion.

The thickness of alveolar bone at the mandibular canine and premolar teeth in normal occlusion.

PurposeThe purpose of this study was to investigate the alveolar bone thickness on the buccal and lingual aspects of mandibular canines and premolars using cone-beam computed tomography (CBCT). The differences between the left side and the right side and that in male and female measurements were reviewed. Patients and MethodsThree-dimensional CBCT of 20 subjects with normal occlusion (9 males and 11 females; mean [SD] age, 21.9 [3.0] y) were used. The thickness of the buccal and lingual bone walls, perpendicular to the long axis of the root, was evaluated at 3 and 5 mm apical to the cementoenamel junction (CEJ) and at the root apex. ResultsThe mean buccal bone thickness measured at 3 and 5 mm apical to the CEJ was less than 2 mm on the canines and the premolars. The buccal bone thickness of the second premolar at 3 and 5 mm from the CEJ was significantly greater than that of the canine and the first premolar. There were no significant differences between the left and right sides, and the overall measurements of the alveolar bone thickness did not show significant male/female differences. ConclusionsThis study presented the thickness of the buccal and lingual bone in different locations apical to the CEJ in subjects with normal occlusion and the frequency distribution of thick buccal bone wall (≥ 2 mm). The second premolar had the highest frequency distribution of thick buccal bone (≥ 2 mm) when compared with canine and the first premolar. The teeth with thin buccal bone (< 2 mm) should be treated with care for the implant because a thin buccal bone may be damaged more easily and buccal bone resorption may occur. This study may provide estimated value for patients with normal occlusion during tooth extraction and implant installation in the canine and premolar area of the mandible. Preoperative radiographic analysis, with care in using CBCT, may be applied for tooth extraction and implant therapy.