Hiroyasu Kanetaka

Histological Evaluation of the Effects of Initially Light and Gradually Increasing Force on Orthodontic Tooth Movement

OBJECTIVE To investigate histologically the effect of initially light and gradually increasing force on tooth movement in the rat. MATERIALS AND METHODS Cuboids made of neodymium-iron-boron magnets (experimental groups) or titanium (control group) were bonded to the lingual surface of the right and left maxillary first molars of 18-week-old male Wistar rats. The initial distances between materials were 1.0 mm generating 4.96 gf (experimental group 1) and 1.5 mm generating 2.26 gf (experimental group 2). In three groups, rats were killed 1, 3, 7, 10, or 14 days after treatment. Histological sections were prepared and stained with hematoxylin and eosin or for tartrate-resistant acid phosphatase (TRAP) activity. The number of TRAP-positive osteoclasts was counted, and the relative hyalinized area was measured on the pressure side of periodontal ligament. RESULTS There were significant differences in the number of osteoclasts among the three groups (P < .05). On days 1 and 3, the numbers of osteoclasts in experimental group 2 were greater than in experimental group 1. There were significant differences in the relative hyalinized area between the control group and experimental group 1 (P < .01) and between experimental groups 1 and 2 (P < .01). On days 1 and 3, the hyalinized area in experimental group 1 was larger than in experimental group 2. CONCLUSION Initially light and gradually increasing force induced tooth movement without the lag phase and showed smooth recruitment of osteoclasts and inhibition of hyalinization.

Age-Related Morphological Changes in the Human Hyoid Bone

Object: Age-related morphological changes in the human hyoid bone were investigated radiographically and histologically. Materials and Methods: Thirty-two measurements were performed on radiographs of 238 hyoid bones from autopsy cases of known age and sex. Thirty-one hyoid bones that were studied by radiography were also examined histologically in horizontal sections. Results: Analysis of the length and width of the hyoid bone revealed significant increases in the body and the anterior part of the greater cornu and a significant decrease in the posterior part of the greater cornu with aging. Most measurements of the body and the greater cornu revealed differences between male and female hyoid bones. The outer margins of the body and the greater cornu were situated further outside in older males compared with females. The breadth of the joint space showed a significant age-related decrease, and the degree of fusion showed a significant age-related increase. Histological findings showed ossified or calcified fusion, with osteoclasts in the marginal area of the joint space. Conclusions: Increasing age induces fusion of the body and the greater cornu. The morphometric changes in the shape of the hyoid bone may represent functional adaptation to articulation fixation.

Numerical Study on the Improvement of Detection Accuracy for a Wireless Motion Capture System

A detection technique having an accuracy of better than 1 mm is required for body motion analysis in the field of medical treatment. A wireless magnetic motion capture system is one such effective detection technique. We propose a candidate system using an LC resonant magnetic marker (LC marker). Previous studies have showed that the system is capable of repeatable position detection accuracy of better than 1 mm if the system has an adequate signal-to-noise (S/N ratio). However, there are some cases in which the detection results include unignorable errors because some approximations, e.g. a magnetic dipole assumption of the LC marker, are applied to solve the inverse problem to determine the position and orientation of the LC marker. Therefore, a numerical analysis is employed to realize a motion capture system having a high detection accuracy. To elucidate the problem of detection error, the influence of variations in the sizes of the LC marker and the pick-up coil are considered in the numerical simulation. After studying the analysis, the main cause of detection error is determined to be the size of the pick-up coil rather than the size of the LC marker. It was also is found that a pick-up coil measuring 10 mm in diameter with a wound coil width of 1 mm achieves a detection accuracy of better than 0.1 mm.

Orthodontic buccal tooth movement by nickel-free titanium-based shape memory and superelastic alloy wire.

OBJECTIVE To examine the mechanical properties and the usefulness of titanium-niobium-aluminum (Ti-Nb-Al) wire in orthodontic tooth movement as compared with nickel-titanium (Ni-Ti) wire. MATERIALS AND METHODS The load deflection of expansion springs was gauged with an original jig. The gradient of the superelastic region was measured during the unloading process. Expansion springs comprising the two types of alloy wires were applied to upper first molars of rats. The distance between the first molars was measured with micrometer calipers. RESULTS The force magnitude of the Ti-Nb-Al expansion spring was lower than that of the Ni-Ti expansion spring over the entire deflection range. The initial force magnitude and the gradient in the superelastic region of the Ti-Nb-Al expansion springs were half those of the Ni-Ti expansion springs. Thus, Ti-Nb-Al expansion springs generated lighter and more continuous force. Tooth movement in the Ni-Ti group proceeded in a stepwise fashion. On the other hand, tooth movement in the Ti-Nb-Al group showed relatively smooth and continuous progression. At 17 days after insertion of expansion springs, there were no significant differences between the Ti-Nb-Al and Ni-Ti groups in the amount of tooth movement. CONCLUSIONS These results indicate that Ti-Nb-Al wire has excellent mechanical properties for smooth, continuous tooth movement and suggest that Ti-Nb-Al wire may be used as a practical nickel-free shape memory and superelastic alloy wire for orthodontic treatment as a substitute for Ni-Ti wire.

Wireless Magnetic Position-Sensing System Using Optimized Pickup Coils for Higher Accuracy

With the aim of improving the detection accuracy of a wireless magnetic position-sensing system using an LC resonant magnetic marker, a pickup coil with an optimal size (10 mm in diameter × mm thick), as calculated by a previous simulation study, was used and tested in this paper. Our study confirmed that positional errors were reduced to a submillimeter order in the area within y=120 mm from the pickup coil array. On the contrary, in the area outside y=130 mm from the pickup coil array, the errors increased by about 0.5-2 mm compared to the results for the previous pickup coil size (25 mm in diameter × 2 mm thick). Regardless of the size of the pickup coil, however, compensation can be made for these positional deviations, including the influence of the mutual inductance between the LC marker and the exciting coil. After application of the compensation process, the detection results were corrected approximately to the actual positions of the LC marker.

In vitro assessment of poly(methylmethacrylate)-based bone cement containing magnetite nanoparticles for hyperthermia treatment of bone tumor

Poly(methylmethacrylate) (PMMA)-based cements containing magnetite (C-PMMA/Fe(3)O(4)) is useful in hyperthermia treatment for bone tumor. We have prepared C-PMMA/Fe(3)O(4) by incorporating Fe(3) O(4) powders of different diameters (means of 300, 35, and 11 nm) into the polymerization reaction of methyl methacrylate monomer to develop a new bone cement with high heating efficiencies in alternating current (AC) magnetic fields. Further, we have investigated the in vitro heating capability of the cements in different AC magnetic fields. The mechanical strength and biocompatibility of the resultant cements were also assessed. Their heat generation strongly depends on the magnetite nanoparticle sizes and applied magnetic fields. The cement containing Fe(3)O(4) with mean diameter around 35 nm exhibited the highest heating capability in AC magnetic fields of 120 and 300 Oe at 100 kHz while that with mean diameter around 11 nm exhibited optimum heating capability in AC magnetic fields of 40 Oe at 600 kHz. The incorporation of Fe(3)O(4) into cement-30 wt % of the total amount of cement-did not significantly change the compressive strength of cement, and the proliferation of rat fibroblast Rat-1 cells on cement discs was not inhibited. Our investigations are useful for designing new PMMA/Fe(3)O(4) bone cement with high heating efficiencies and biocompatibilities for bone tumor treatments.

Dorsomorphin stimulates neurite outgrowth in PC12 cells via activation of a protein kinase A‐dependent MEK‐ERK1/2 signaling pathway

In this study, we investigated the effect of dorsomorphin, a selective inhibitor of bone morphogenetic protein (BMP) signaling, on rat PC12 pheochromocytoma cell differentiation. PC12 cells can be induced to differentiate into neuron‐like cells possessing elongated neurites by nerve growth factor, BMP2, and other inducers. Cells were incubated with BMP2 and/or dorsomorphin, and the extent of neurite outgrowth was evaluated. Unexpectedly, BMP2‐mediated neuritogenesis was not inhibited by co‐treatment with dorsomorphin. We also found that treatment with dorsomorphin alone, but not another BMP signaling inhibitor, LDN‐193189, induced neurite outgrowth in PC12 cells. To further understand the mechanism of action of dorsomorphin, the effects of this drug on intracellular signaling were investigated using the following signaling inhibitors: the ERK kinase (MEK) inhibitor U0126; the tropomyosin‐related kinase A inhibitor GW441756; and the protein kinase A (PKA) inhibitor H89. Dorsomorphin induced rapid and sustained ERK1/2 activation; however, dorsomorphin‐mediated ERK1/2 activation and neuritogenesis were robustly inhibited in the presence of U0126 or H89, but not GW441756. These findings suggest that dorsomorphin has the potential to induce neuritogenesis in PC12 cells, a response that requires the activation of PKA‐dependent MEK‐ERK1/2 signaling.

Phase Constitution and Mechanical Properties of Ti-(Cr, Mn)-Sn Biomedical Alloys

In order to produce new β (bcc) Ti alloys for medical applications, effects of Mn substitution for Cr on phase constitution and mechanical properties of Ti-Cr-Sn alloys were investigated. All the Ti-7mol%(Cr, Mn)-3mol%Sn alloys investigated by XRD analysis were identified as β (bcc) alloys, and athermal ω phase was also detected in Ti-7mol%Mn-3mol%Sn . The lattice parameter of β was slightly decreased by Mn substitution. Besides, the Mn substitution for Cr raised the hardness and the strength while reduced the ductility of the Ti-Cr-Sn alloys. The hardening by Mn substitution must be due to ω precipitation. The hardening is discussed from the viewpoint of electron atom ratio (e/a) in comparison with Ti-Cr binary alloys in the literature.

Preparation, structure, and in vitro chemical durability of yttrium phosphate microspheres for intra-arterial radiotherapy†

Chemically durable microspheres containing yttrium and/or phosphorus are useful for intra-arterial radiotherapy. In this study, we attempted to prepare yttrium phosphate (YPO₄) microspheres with high chemical durability. YPO₄ microspheres with smooth surfaces and diameters of around 25 μm were successfully obtained when gelatin droplets containing yttrium and phosphate ions were cooled and solidified in a water-in-oil emulsion and then heat-treated at 1100°C. The chemical durability of the heat-treated microspheres in a simulated body fluid at pH = 6 and 7 was high enough for clinical application of intra-arterial radiotherapy.

A new tracking system of jaw movement using two magnets

Summary form only given. Tracking of jaw movement is sufficient to characterize the treatment of periodontal disease. Conventional optical methods or mechanical methods have adverse effect due to the presence of metal clutch in the patients mouth. These clutches disturb the physiology. Conventional magnetic method has utilized a permanent magnet and magnetic field sensors. The conventional magnetic method has inherent limitation that the system provides only the position of the point source and the sensors are fixed to the head. This one point detection is not sufficient to characterize the treatment of jaw movement as a rigid body. A new magnetic tracking system of jaw movement utilized a six degrees of freedom of the lower jaw is proposed here. This technique is based on the magnetic motion capture system of two magnets proposed by us (IEEE Trans. Mgn. vol.36, p.3646, (2000)). The system does not need to fix magnetic field sensors or clutch to the patients body or mouth. The impact of this result goes beyond the conventional optical and magnetic tracking system of jaw movement.