Investigating Finite Sample Properties of Estimators for Approximate Factor Models When N Is Small

This paper examines the finite sample properties of estimators for approximate factor models when N is small via simulation study. Although the "rule-of-thumb" for factor models does not support using approximate factor models when N is small, we find that the principal component analysis estimator and quasi-maximum likelihood estimator proposed by Doz et al. (2008) perform very well even in this case. Our findings provide an opportunity for applying approximate factor models to low-dimensional data, which was thought to have been inappropriate for a long time.Approximate factor model, Principal components, Quasi-maximum likelihood

Reducing the Size Distortion of the KPSS Test

This paper proposes a new stationarity test based on the KPSS test with less size distortion. We extend the boundary rule proposed by Sul, Phillips and Choi (2005) to the autoregressive spectral density estimator and parametrically estimate the long-run variance. We also derive the finite sample bias of the numerator of the test statistic up to the 1/T order and propose a correction to the bias term in the numerator. Finite sample simulations show that the correction term effectively reduces the bias in the numerator and that the finite sample size of our test is close to the nominal one as long as the long-run parameter in the model satisfies the boundary condition.Stationary test, size distortion, boundary rule, bias correction

A Multidisciplinary Approach to Malocclusion Caused by Facial Multiple Fracture

In the case of multiple facial fractures, a simple open reduction occasionally causes various disorders during healing process after the surgery. Moreover, esthetic disturbance of a facial deformity might be induced. Therefore, the acquisition of facial symmetry and the recovery of occlusal and masticatory functions become increasingly important. This case report presents a successful treatment of facial multiple fracture induced by a car accident. A 20-year-old male was diagnosed with suffered multiple midface and mandibular fractures induced by a car accident. Midface fractures included the LeFort I and II type fractures, as well as sagittal fracture at midline and fractures from right maxillary sinus anterior wall to orbital wall. In the mandible, midline and left body fractures were detected. The patient underwent open reduction and rigid fixation of the fractured left zygoma, comminuted LeFort I and II fractures, and midline and left body of the mandible with intermaxillary fixation by multibracket appliance; maxillary osteotomy with iliac bone grafting; orthognathic two-jaw surgery with coronoid process grafts onto the depressed zygoma; and onlay graft of hydroxyapatite block on mandible. As the result, the multidisciplinary treatments successfully recover functions and esthetics to the satisfactory level of the patient with multiple facial fractures. As treatments for multiple facial fractures are required complexity due to the extent of trauma, multidisciplinary approach under the close cooperation between hospital departments is thought to be important

Clinical significance of the expression of connexin26 in colorectal cancer

<p>Abstract</p> <p>Background</p> <p>Connexin26 (Cx26) is one of the connexins (Cxs) family members which form gap junction channels. Cx26 is considered to be a tumor suppressor gene. However, recent studies revealed that over expression of Cx26 is associated with a poor prognosis in several human cancers. This study investigated the correlation between Cx26 expression and the clinicopathological features and P53 expression in colorectal cancer.</p> <p>Methods</p> <p>One hundred and fifty-three patients who underwent a curative resection were studied. Tissue samples were investigated by immunohistochemical staining using antibodies for Cx26 and P53. Moreover, apoptotic cells were detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining.</p> <p>Results</p> <p>Cx26 expression was found in 83 cases (54.2%) and P53 expression in 71 cases (46.4%). A correlation was observed between the Cx26 expression and recurrence, histology, and p53 expression (P < 0.05). Cx26 positive tumors had significantly longer survival than Cx26 negative tumors (P < 0.05). A multivariate Cox analysis demonstrated that Cx26 expression was an independent prognostic factor (P < 0.05). However, no significant correlation was observed between Cx26 and AI.</p> <p>Conclusion</p> <p>This study suggests that Cx26 expression is an independent prognostic factor in patients that undergo a curative resection of colorectal cancer.</p

Establishment of a new rehabilitation program using masticatory training food for jaw deformity patients

Background/purpose: Patients with jaw deformities may show a reduction in masticatory function as a result of postoperative hypofunction. This study aimed to establish a novel rehabilitation program using a commercially available masticatory training food for patients with jaw deformities after orthognathic surgery. Materials and methods: Nine patients with mandibular prognathism (the training group: n = 5, and the non-training group: n = 4) and 6 control participants with normal occlusion were included in this study. For the rehabilitation program with masticatory exercise, patients were instructed to chew the training food once a day for 60 days starting from 10 days after the surgery. The effects of the rehabilitation program were assessed by determining the maximum bite force (MBF) and the masticatory performance (MP). Clinical assessments were performed just before orthognathic surgery (Pre) and at 10 days (T0), 1 month (T1), 2 months (T2), and 3 months (T3) after surgery. Results: Compared with the non-training group, the training group showed a trend toward greater recovery amount of MBF from Pre to T3, and a significantly greater recovery amount in MP (p < 0.05) from Pre to T3. When the time-series change of MP was evaluated in both groups from T0 to T3, a significant difference was observed in the interaction terms (p = 0.03). This result indicates that the effectiveness of the training may be demonstrated by following the postoperative course further. Conclusion: The rehabilitation using this training food may become a useful method for postoperative hypofunction in patients with jaw deformities

THE FRICTIONAL COEFFICIENTS IN TI-NB ALLOY

Objectives: To determine the frictional force (FF) of the novel, elastic, bendable titanium-niobium (Ti-Nb) alloy orthodontic wire in stainless steel (SS) brackets and to compare it with those of titanium-nickel (Ti-Ni) and titanium-molybdenum (Ti-Mo) alloy wires. Materials and Methods: Three sizes of Ti-Nb, Ti-Ni, and Ti-Mo alloy wires were ligated with elastic modules to 0.018-inch and 0.022-inch SS brackets. The dynamic FFs between the orthodontic wires and SS brackets were measured at three bracket-wire angles (0゜, 5゜, and 10゜) with an Instron 5567 loading apparatus (Canton, Mass). Results: FFs increased gradually with the angle and wire size. In the 0.018-inch-slot bracket, the dynamic FFs of Ti-Nb and Ti-Ni alloy wires were almost the same, and those of the Ti-Mo alloy wire were significantly greater (P<0.05). FF values were 1.5–2 times greater in the 0.022-inch-slot bracket than in the 0.018-inch-slot bracket, regardless of alloy wire type, and the Ti-Mo alloy wire showed the greatest FF. Scanning electric microscopic images showed that the surface of the Ti-Mo alloy wire was much rougher than that of the Ti-Ni and Ti-Nb alloy wires. Conclusion: These findings demonstrate that the Ti-Nb alloy wire has almost the same frictional resistance as the Ti-Ni alloy wire, although it has a higher elastic modulus

Treatment decision of camouflage or surgical orthodontic treatment for skeletal Class III patients based on analysis of masticatory function

Background/purpose: Surgical orthodontic treatment is recommended for patients with severe dentoskeletal discrepancies, while camouflage orthodontic treatment is recommended for patients with mild to moderate discrepancies. However, the decision as to which treatment should be chosen is complicated. The purpose of this study was to determine differences in masticatory function in patients who underwent camouflage and surgical orthodontic treatment for skeletal Class III malocclusion, as well as the usefulness of Wits appraisal in treatment decision based on masticatory functional analysis. Materials and methods: The study subjects were 45 patients with skeletal Class III malocclusion (15 cases with camouflage orthodontics and 30 cases with orthognatic surgery) and 12 individuals with normal occlusion. We analyzed the pre-treatment records of electromyographic activities of masseter and temporalis muscles and jaw movements. Results: There were no significant differences in various functional measurements between the camouflage and surgery groups. However, there were significant but not strong correlations between ANB and both masseter muscle activity (r = 0.36, p < 0.01) and expression ratio of abnormal chewing (r = −0.54, p < 0.01). Division of patients into two groups using a cutoff value of −6.0 mm for Wits appraisal showed a significant difference in masseter muscle activity between −6.0 mm or less group and the control (p < 0.01) but none between more than −6.0 mm group and the control. Conclusion: Camouflage orthodontic treatment is inappropriate for patients with relatively severe dentoskeletal discrepancies. Wits appraisal of −6.0 mm is a potentially useful parameter for treatment decision

Functional training after orthognathic surgery

Background/purpose: Even after surgical orthodontic treatment, the level of masticatory function in patients with jaw deformities is still lower than that of healthy subjects. The purpose of this study was to evaluate the effects of functional training program using gum chewing exercise after orthognathic surgery on masticatory function in patients with mandibular prognathism. Materials and methods: The study subjects were 16 patients with mandibular prognathism who underwent orthognathic surgery and 8 individuals with normal occlusion. Patients were divided into two groups (training group and non-training group; n = 8 per group). Functional training included gum chewing exercise and patient-education about masticatory function. The training; gum chewing exercise of 5 min twice a day for 90 days, started at 3 months after surgery. For each subject, electromyographic activities of masseter and temporalis muscles during maximum voluntary clenching (MVC) and jaw movement during gum chewing were recorded before and after surgical orthodontic treatment. Two parameters; activity index (AI: ratio of activity of masseter and temporalis muscles) and error index (EI: ratio of the number of abnormal chewing patterns), were used. Results: In the training group, the AI value during MVC increased significantly and the EI value during gam chewing decreased significantly after surgical orthodontic treatment (AI: p < 0.01; EI: p < 0.01), indicating the improvement of activity balance of masseter and temporalis muscles and conversion of the jaw movement from abnormal to normal pattern (p < 0.01). Conclusion: Our findings suggested that functional training using the gum chewing and patient-education exercise improved masticatory function in patients with mandibular prognathism

Thread shape, cortical bone thickness, and magnitude and distribution of stress caused by the loading of orthodontic miniscrews : finite element analysis

Cortical bone thickness is assumed to be a major factor regulating miniscrew stability. We investigated stress distribution in two miniscrews with different thread shapes (type A and B) and in cortical bone of three different thicknesses using three-dimensional (3D) finite element (FE) models. More specifically, 3D FE models of two different miniscrews were created and placed obliquely or vertically into a cylindrical bone model representing different cortical bone thicknesses. When force was applied to the miniscrew, the stress distribution on the screw surface and in the peri-implant bone was assessed using FE methodology. Miniscrew safety was evaluated using a modified Soderberg safety factor. Screw head displacement increased with a decrease in cortical bone thickness, irrespective of screw type. The smallest minimum principal stresses on the screw surfaces remained constant in type A miniscrews on changes in cortical bone thickness. Minimum principal stresses also appeared on the cortical bone surface. Lower absolute values of minimum principal stresses were seen in type A miniscrews when placed vertically and with upward traction in obliquely placed type B miniscrews. Both miniscrews had acceptable safety factor values. Taken together, orthodontists should select and use the suitable miniscrew for each patient in consideration of bone properties