Yoshinaka Shimizu

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.

Osteogenesis by gradually expanding the interface between bone surface and periosteum enhanced by bone marrow stem cell administration in rabbits.

OBJECTIVE We investigated whether administration of mesenchymal stem cells (MSCs) promotes bone formation at the gap created by periosteal distraction. STUDY DESIGN A mesh plate was placed subperiosteally in rabbit parietal bones. Following elevation of the mesh plate, rabbit MSCs were administered into the gap. Controls received phosphate-buffered saline (PBS). The volume, height, bone mineral density (BMD), and bone mineral content (BMC) of newly formed bone were examined using microcomputed tomography. Histological analysis was performed by hematoxylin and eosin staining and immunohistochemistry for type I collagen and osteocalcin. RESULTS The experimental group showed significantly increased volume, height, BMD, and BMC in newly formed bone tissues at the gaps compared with the control group (P < .05). The newly formed bone tissues showed both type I collagen and osteocalcin expression in the MSC-administration group. CONCLUSION Mesenchymal stem cell administration may be useful to induce osteogenesis at sites of periosteal distraction.

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.

Simplified procedure for augmentation of the sinus floor using a haemostatic nasal balloon.

Perforation of the sinus membrane is the most common complication of sinus lift augmentation. A haemostatic nasal balloon can easily separate the sinus membrane without perforating it. The use of a haemostatic nasal balloon has three major advantages: a low risk of perforation of the sinus membrane even in anatomically complex conditions, a low incidence of infection and bleeding, and a shorter operating time.

Age-Related Morphological Changes in Squamous and Parietomastoid Sutures of Human Cranium

Age-related morphological changes in the inner and outer surfaces of the squamous and parietomastoid sutures were examined in 65 skulls (35 male, 30 female) obtained from Japanese subjects 5–90 years of age at the time of death. Dimensions were measured in both the horizontal and sagittal planes. Wavelength analysis was done by three-dimensional construction. Irregularities were evaluated by calculating fractal dimensions. The outer squamous suture showed no significant age-related changes in size, but wavelength increased because of the development of bony interdigitations with aging. The posterior part of the outer squamous suture showed significant age-related increases in both wavelength (p < 0.01, R2 = 0.164) and fractal dimension (p < 0.01, R2 = 0.101) in males. The parietomastoid suture showed significant age-related changes in size (p < 0.05), but not in wavelength or fractal dimension. These distinct morphological changes found on both the inner and outer surfaces of the squamous and parietomastoid sutures suggest that the age-related morphological characteristics of these sutures are affected by extrinsic mechanical forces.

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.

A Morphometric Study of Age-Related Changes in Adult Human Epiglottis Using Quantitative Digital Analysis of Cartilage Calcification

The epiglottis plays an important role in deglutition in humans. The present study investigated age-related changes in the epiglottis using macroscopic and microscopic measurements. Epiglottic specimens from 281 Japanese adult cadavers (177 males, 104 females) were obtained. Specimens were divided into three groups according to age: group I: 20–39 years old (32 males, 26 females), group II: 50–69 years old (82 males, 36 females), and group III: 80–98 years old (63 males, 42 females). Width, height, and thickness were measured macroscopically. To evaluate the degree of calcium deposition, the calcium volume in digitalized von Kossa-stained sections was assessed using a quantitative analysis. An elemental analysis of the area detected with von Kossa staining was done using energy-dispersive X-ray fluorescence spectrometer (EDX). Measurements of the thickness and cell density in the superficial and deep layers of epiglottic cartilage were performed in horizontal histological sections. No significant differences in macroscopic width or height were found across the age groups in either sex. A series of three measurements in males was significantly larger than in females (p < 0.05). The volume of the calcium deposit area was greater in males than in females (p < 0.05) and was significantly increased in group III in males (p < 0.05). The lower level of the epiglottic cartilage showed a greater calcium deposit area than the upper level. In the scanning image by line and surface analysis using EDX, the calcium deposit areas detected with von Kossa staining indicated a close association of calcium and phosphorus ions. The mean Ca/P molar ratio in the calcium deposit area was 1.32 ± 0.12. Microscopic cartilage thickness increased significantly with age (p < 0.05), and was greater in males than in females (p < 0.05). Cartilage cell density in the superficial cartilage layer was higher than in the deep layer and was decreased in group III (p < 0.05). Cartilage cell density was lower in males compared to females. Diameter of chondrocytes significantly increased in group III (p < 0.05) and was larger in males than in females in group III (p < 0.05). Epiglottic cartilage exhibited marked sex-related differences and progression of calcification with age. Calcification of epiglottic cartilage in elderly individuals may affect movement patterns in deglutition.

Assessment of protein expression and gene status of human epidermal growth factor receptor (HER) family molecules in ameloblastomas.

BACKGROUND To evaluate roles of human epidermal growth factor receptor (HER) family molecules in ameloblastomas, protein expression and gene status were analyzed in odontogenic tissues. METHODS Sixty five ameloblastomas, 10 dental follicles, and 11 dentigerous cysts were immunohistochemically examined with antibodies against epidermal growth factor receptor (EGFR) and HER2, HER3, and HER4. Amplification of EGFR and HER2 was evaluated by chromogenic in situ hybridization (CISH). In 18 ameloblastomas, EGFR exons 19 and 21 were analyzed by direct DNA sequencing. RESULTS Immunohistochemical reactivity for EGFR and HER2, HER3, and HER4 was detected in odontogenic epithelium. Expression of EGFR and HER4 was remarkable in these odontogenic tissues, as compared with that of HER2 and HER3. The level of HER2 immunoreactivity was significantly lower in ameloblastomas than in dental follicles and dentigerous cysts. Follicular ameloblastomas showed significantly higher expression of HER2 and HER4 than plexiform ameloblastomas. Reactivity for EGFR and HER3 was slightly stronger in recurrent ameloblastomas than in primary ameloblastomas. CISH did not reveal obvious amplification of EGFR or HER2 in ameloblastomas; however, EGFR and HER2 gene signals were significantly higher in follicular ameloblastomas than in plexiform ameloblastomas. Direct DNA sequencing of EGFR did not show any gene alteration in ameloblastomas. CONCLUSION Expression of HER family molecules, especially EGFR and HER4, in odontogenic tissues suggests that growth signals mediated by these receptor molecules contribute to cell proliferation, survival, and differentiation in both normal and neoplastic odontogenic epithelial tissues. Some of these molecules might be useful for predicting outcomes in patients with ameloblastomas.

90Sr in teeth of cattle abandoned in evacuation zone: Record of pollution from the Fukushima-Daiichi Nuclear Power Plant accident

Here we determined the 90Sr concentrations in the teeth of cattle abandoned in the evacuation area of the Fukushima-Daiichi Nuclear Power Plant (FNPP) accident. 90Sr activity concentrations in the teeth varied from 6–831 mBq (g Ca)−1 and exhibited a positive relationship with the degree of radioactive contamination that the cattle experienced. Even within an individual animal, the specific activity of 90Sr (Bq (g Sr)−1) varied depending on the development stage of the teeth during the FNPP accident: teeth that were early in development exhibited high 90Sr specific activities, while teeth that were late in development exhibited low specific activities. These findings demonstrate that 90Sr is incorporated into the teeth during tooth development; thus, tooth 90Sr activity concentrations reflect environmental 90Sr levels during tooth formation. Assessment of 90Sr in teeth could provide useful information about internal exposure to 90Sr radiation and allow for the measurement of time-course changes in the degree of environmental 90Sr pollution.