Zuisei Kanno

Effects of mechanical strain on proliferation and differentiation of bone marrow stromal cell line ST2

Differentiation of mesenchymal stromal cells into osteoblasts is regulated by many factors including growth factors, cytokines, and hormones. Mechanical stress has been considered to be an important factor in bone modeling and remodeling. However, biological responses of stromal cells to mechanical stimuli are still unknown. To show the correlation between magnitude of mechanical strain and differentiation of stromal cells into osteoblasts, we investigated the proliferation and the expression of osteoblast-related genes in stromal cell line ST2 that is in the process of osteoblastic differentiation by treatment with ascorbic acid and β-glycerophosphate, under 0.8%–15% elongation using the Flexercell Strain system. The expression of osteoblast-related genes was analyzed by real-time quantitative polymerase chain reaction (PCR). Cell proliferation significantly increased at 5%, 10%, and 15% elongation compared to that of unloaded controls. Alkaline phosphatase (ALPase) activity significantly increased at 0.8% and 5% elongation but decreased at 10% and 15% elongation. At 1 h and 6 h, mRNA level of Cbfa1/Runx2 increased at lower magnitudes of strain (0.8% and 5% elongation) but decreased at higher magnitude of strain (15% elongation). At 24 and 48 h, Cbfa1/Runx2 and osteocalcin mRNAs decreased at 5%, 10%, and 15% elongation, whereas cell proliferation and expression of type I collagen mRNA increased at the same elongation. These results indicate that mechanical strain stimulates osteoblastic differentiation of stromal cells at low magnitudes of strain.

Three-dimensional quantification of susceptibility artifacts from various metals in magnetic resonance images

Susceptibility artifacts generated in magnetic resonance (MR) images were quantitatively evaluated for various metals using a three-dimensional (3-D) artifact rendering to demonstrate the correlation between magnetic susceptibility and artifact volume. Ten metals (stainless steel, Co-Cr alloy, Nb, Ti, Zr, Mo, Al, Sn, Cu and Ag) were prepared, and their magnetic susceptibilities measured using a magnetic balance. Each metal was embedded in a Ni-doped agarose gel phantom and the MR images of the metal-containing phantoms were taken using 1.5 and 3.0 T MR scanners under both fast spin echo and gradient echo conditions. 3-D renderings of the artifacts were constructed from the images and the artifact volumes were calculated for each metal. The artifact volumes of metals decreased with decreasing magnetic susceptibility, with the exception of Ag. Although Sn possesses the lowest absolute magnetic susceptibility (1.8×10(-6)), the artifact volume from Cu (-7.8×10(-6)) was smaller than that of Sn. This is because the magnetic susceptibility of Cu was close to that of the agarose gel phantom (-7.3×10(-6)). Since the difference in magnetic susceptibility between the agarose and Sn is close to that between the agarose and Ag (-17.5×10(-6)), their artifact volumes were almost the same, although they formed artifacts that were reversed in all three dimensions.

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.

Preapplication of orthodontic forces to the donor teeth affects periodontal healing of transplanted teeth.

OBJECTIVE To investigate how the preapplication of orthodontic forces to the donor teeth affects the periodontal healing after transplantation. MATERIALS AND METHODS The orthodontic force (1.5 cN) was applied to the maxillary right molars of 6-week-old male Spraque-Dawley rats (n = 21) in the experimental side, and the left side of the same animals was used as the control. After 7 days, both right and left maxillary second molars were extracted or replanted. Periodontal conditions were evaluated in the histological specimens 7 days after applying orthodontic force (before and after extraction) and 14 days after replantation. RESULTS The application of orthodontic force for 7 days significantly increased the periodontal ligament (PDL) space and also the width of the alveolar socket, which resulted in a rich attached PDL to the root surface of the extracted teeth. Significantly more root resorption was also detected in the control side without preapplication of orthodontic force 14 days after replantation. This root resorption might involve in the disruption of the PDL. CONCLUSION These results suggested that the preapplication of orthodontic force to the donor teeth increased the PDL width and eased the extraction, which might decrease root resorption after replantation.

Mechanical properties of orthodontic wires made of super engineering plastic

Most orthodontic equipment is fabricated from alloys such as stainless steel, Co-Cr and Ni-Ti because of their excellent elastic properties. In recent years, increasing esthetic demands, metal allergy and interference of metals with magnetic resonance imaging have driven the development of non-metallic orthodontic materials. In this study, we assessed the feasibility of using three super engineering plastics (PEEK, PES and PVDF) as orthodontic wires. PES and PVDF demonstrated excellent esthetics, although PEEK showed the highest bending strength and creep resistance. PEEK and PVDF showed quite low water absorption. Because of recent developments in coloration of PEEK, we conclude that PEEK has many advantageous properties that make it a suitable candidate for use as an esthetic metal-free orthodontic wire.

Retrospective study of 100 autotransplanted teeth with complete root formation and subsequent orthodontic treatment

INTRODUCTION Autotransplantation has become a major therapeutic option for replacing missing teeth in adult orthodontic patients. However, little systematic information is available about the long-term stability of autotransplanted teeth with complete root formation after the application of an orthodontic force. The objective of this study was to investigate the outcomes of autotransplanted teeth with complete root formation that underwent orthodontic treatment. METHODS One hundred teeth, autotransplanted in 89 patients, were examined over a mean observation period of 5.8 years. Orthodontic force was applied with nickel-titanium wires 4 to 8 weeks after autotransplantation. Root resorption, ankylosis, mobility, pocket depth, and inflammation at the recipient site were investigated clinically and with radiographs. RESULTS The survival rate of the autotransplanted teeth was 93.0%. Abnormal findings were found in 29 teeth, including 7 lost teeth, for a success rate of 71.0%. Donor tooth type and occlusal condition of the donor tooth before transplantation were associated with abnormal findings. CONCLUSIONS The early application of orthodontic force may increase the success rate of autotransplanted teeth, and the type and presurgical occlusal condition of donor teeth affect the success rate.

Clinical study of frontal chewing patterns in various crossbite malocclusions.

INTRODUCTION The purpose of this study was to clarify the frontal chewing patterns of various crossbite malocclusions. METHODS A mandibular kinesiograph was used to record the masticatory movements of 106 subjects (ages, 12-35 years) with crossbite malocclusion and 22 subjects (ages, 16-30 years) with normal occlusion. The chewing patterns were classified into 8 chewing types according to the cycle shape of the frontal incisor point movement. The crossbite subjects were divided into 5 groups by the anteroposterior position of the crossbite, and then the subjects with posterior crossbite were divided into 3 groups by the transverse position of the crossbite. The Mann-Whitney U test was used to compare the frequency of each chewing type between any crossbite group and the control group; and between the various crossbite groups. RESULTS In the crossbite groups, normal chewing occurred much less often than in subjects with normal occlusion. In the posterior crossbite group, reverse chewing was greater (P = 0.002), and normal chewing was less frequent (P = 0.001) compared with the anterior crossbite group. When accompanied by mandibular shift, mandibular prognathism, arch crossbite, in the crossbite or shift side, reverse type, and reverse-crossing type occurred more often than in contralateral side. CONCLUSIONS In the frontal plane, patients with posterior crossbite might have more abnormal chewing types than those with anterior crossbite, and posterior crossbite could contribute to the high frequency of reverse and reverse-crossing chewing types, especially when accompanied by mandibular shift, mandibular prognathism, or arch crossbite.

Occlusal hypofunction induces atrophic changes in rat gingiva.

OBJECTIVE To clarify the influence of occlusal hypofunction on the integrity of gingival tissue and gingival extracellular matrix biosynthesis. MATERIALS AND METHODS Thirteen-week-old male Wistar rats were divided into two groups. To eliminate occlusal forces, all the right maxillary molars were extracted in the hypofunctional group. The control group was anesthetized but not subjected to surgery. The rats were killed at 2 and 4 weeks after the procedure, and the lower right second molars were prepared for histological analysis. To investigate the effect of occlusal hypofunction on collagen biosynthesis, the expression of connective tissue growth factor (CTGF) and lysyl oxidase (LOX) was determined by immunohistochemistry as well as histological examination by hematoxylin and eosin staining. RESULTS Disorientation of the collagen fibers, proliferation of the connective tissue fibroblasts, and enlargement of epithelial intercellular gaps were observed in gingival tissue of rat molars with experimental occlusal hypofunction. Immunohistochemically, the expression of CTGF and LOX was increased significantly (P < .05) in the hypofunctional group. CONCLUSION These results suggest that occlusal hypofunction can affect the structural integrity and the expression of CTGF and LOX in gingival tissue.

Autotransplantation combined with orthodontic treatment in adult patients

Abstract Autotransplantation has been a reliable approach to replace the missing tooth. However, some undesirable prognoses are still remaining especially in those teeth with complete root development. This case report presents the treatment of three adult patients with missing teeth, and autotransplantation was carried out to reconstruct their dentition. In order to avoid dentoalveolar ankylosis and inflammatory root resorption of the transplanted teeth, the period for splinting was limited to a minimum and the following orthodontic treatments were performed with Ti–Ni alloy wires which possess stable light forces. Neither ankylosis nor root resorption was evident during the treatment, and the conditions of the transplanted teeth were excellent in more than 4 years after transplantation.

Comparative cephalometric study of Class I malocclusion in Egyptian and Japanese adult females

Abstract Orthodontic diagnosis is the key factor for conducting a successful orthodontic treatment. It typically includes comparing a patients cephalometric measurements to standard values. However, lateral cephalometric norms, may be specific to an ethnic group and cannot always be applied to other ethnic types. Thus the purpose of this study was to compare the cephalometric features of Class I malocclusion in Egyptian and Japanese adult females inorder to understand the ethnic differences between these two groups. The lateral cephalograms of 50 Egyptian adult females and 50 Japanese adult females were traced and digitized by one investigator. Seventeen angular measurements and thirteen linear measurements of facial form were computed. A comparison of the vertical dimensions showed that, the Japanese had a significantly steeper mandibular plane angle. Also, Japanese females had a significantly larger lower face height together with increased distances of the posterior teeth to the mandibular plane. For the soft tissue dimensions, the Japanese subjects had a significantly less prominent nose, protruded lip positions, and a more retruded chin compared with Egyptians. These characteristic skeletal and soft tissue different features should be taken into consideration when formulating an orthodontic treatment plan for patients of varying ethnic backgrounds to optimize the final results.