Je Uk Park

Three-dimensional finite element analysis of stress distribution and displacement of the maxilla following surgically assisted rapid maxillary expansion

PURPOSE The aim of this study was to investigate the displacement and stress distributions during surgically assisted rapid maxillary expansion under different surgical conditions. MATERIALS AND METHODS 3-dimensional finite element model of a maxilla with a Hyrax appliance was constructed and an expansion force of 6000 grams was applied using the expansion screw. According to the surgical procedures, 5 groups including a control group without surgery (Group I) were simulated. The experimental groups were as follows; Group II (Le Fort I osteotomy), Group III (Le Fort I osteotomy and paramedian osteotomy), Group IV (Le Fort I osteotomy and pterygomaxillary separation), and Group V (Le Fort I osteotomy, paramedian osteotomy, and pterygomaxillary separation). RESULTS Displacement of the maxilla gradually increased from Group 1 to Group 5 in all three planes of space, indicating that combination of the Le Fort I osteotomy with paramedian osteotomy and pterygomaxillary separation produce greatest displacement of the maxilla. By surgical relief, the stress exerted on anchor teeth was significantly reduced. CONCLUSION The results suggested that the combination of Le Fort I and paramedian osteotomy with pterygomaxillary separation is an effective procedure for increasing the expansion of the maxilla with lower side effects caused by excessive stresses around the anchor teeth.

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.

Evaluation of minimal versus conventional presurgical orthodontics in skeletal class III patients treated with two-jaw surgery.

PURPOSE The purpose of this study was to compare changes in hard and soft tissues and the treatment efficacy of 2-jaw surgery combined with nonextraction treatment for skeletal Class III malocclusion in patients who received minimal presurgical orthodontics (MPO) versus those who received conventional presurgical orthodontics (CPO). MATERIALS AND METHODS Thirty-two patients (16 in each group) with skeletal Class III malocclusion who underwent 2-jaw surgery were included in the study. Serial lateral cephalometric films were traced at 4 stages: before treatment (T0), before surgery (T1), 1 month after surgery (T2), and at debonding (T3). Cephalometric measurements and treatment duration were compared using independent t test and Mann-Whitney U test. RESULTS After the presurgical treatment phase, the angle between the lower incisor axis and mandibular plane, overjet, and soft tissue pogonion to the vertical reference line showed larger changes (P < 0.01) in the CPO group, whereas the pogonion to the horizontal reference line showed larger changes (P < .05) in the MPO group. In the postsurgical phase (T2 to T3), there were no significant differences between the 2 groups. Total treatment duration was significantly shorter in the MPO group. CONCLUSIONS There were no significant differences between the MPO and CPO groups in the hard and soft tissue cephalometric variables. The MPO group had a shorter total treatment time. It is therefore recommended that clinicians consider these results when selecting MPO as a treatment option for accurate diagnosis and treatment planning of Class III surgical patients.

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.

Bone formation on biomimetic calcium phosphate-coated and zoledronate-immobilized titanium implants in osteoporotic rat tibiae.

PURPOSE Coating prostheses with calcium phosphate (CaP) can boost ossification and provide an appropriate vehicle for drug delivery. In this study, CaP coating was performed using a biomimetic method, and zoledronate (ZOL) was incorporated to promote peri-implant bone formation in an osteoporotic environment. MATERIALS AND METHODS Twenty female 8-week-old rats were ovariectomized to induce osteoporosis. Twelve weeks later, the animals were randomly separated into four groups representing different ZOL concentrations in the immersion solution: 0 (control), 8, 80, and 800 μg/mL. Surface-treated implants were inserted in both tibiae, and the rats were sacrificed 8 weeks after implantation. Specimens were retrieved for histomorphometric and microcomputed tomographic analyses. RESULTS A thin CaP coating was formed on the surface of the titanium implants, and ZOL was successfully incorporated into the structure of the biomimetic CaP coating. There were significant differences between the groups with regard to bone volume, whereas bone-implant contact comparisons did not yield any significant differences. The microstructural results clearly illustrated the positive effect of ZOL loading on the implants, as compared to the controls. CONCLUSIONS The data suggest that biomimetic CaP coating followed by bisphosphonate immobilization is effective in improving bone quality and preserving bone volume around dental implants; therefore, this technique may be beneficial for osteoporosis patients.

Stability After Bilateral Sagittal Split Osteotomy With Rigid Internal Fixation in Surgery-First Approach

PURPOSE The purpose of this study was to evaluate the stability of bilateral sagittal split ramus osteotomy (BSSO) setback with rigid internal fixation in a surgery-first approach (SFA) for patients with skeletal Class III malocclusion. PATIENTS AND METHODS Twenty-seven consecutive patients with skeletal Class III malocclusion treated with BSSO with the SFA were included in the study. Lateral cephalograms were taken and traced before surgery and 1 and 6 months after surgery. Cephalometric measurements were compared using repeated-measures analysis of variance. A P value less than or equal to .05 was considered significant. RESULTS The study included 9 men (age, 25.7 ± 2.9 yr) and 18 women (age, 26.6 ± 4.2 yr). Treatment time was 8.4 ± 1.5 months. Horizontally, there were no meaningful anteroposterior changes of the pogonion and B point during the postsurgical period (0.9 and 0.6 mm, respectively). Vertically, the pogonion showed superior movement after surgery (2.4 mm) without major postsurgical change (0.6 mm). The B point showed major superior movement after surgery (2.3 mm) and during the postsurgical period (1.2 mm). The inclination of the lower incisor was increased labially during the postsurgical period (2.4°), although this was not statistically important. CONCLUSIONS In the present study, there was no major horizontal relapse for any variable (<1 mm). Vertically, all variables showed no meaningful changes during the postsurgical period except the B point showed 1.2 mm of superior displacement. BSSO with rigid fixation using the SFA seems to be an effective and predictable procedure in patients with skeletal Class III malocclusion.