Megumi Hashimoto

Publications (3)3.74 Total impact

• Article: The effect of bone morphometric changes on orthodontic tooth movement in an osteoporotic animal model.

  Megumi Hashimoto, Hitoshi Hotokezaka, Irin Sirisoontorn, Takako Nakano, Kotaro Arita, Motohiro Tanaka, Noriaki Yoshida
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  ABSTRACT: Abstract Objective: To elucidate the effect of bone morphometric changes on orthodontic tooth movement (OTM) in zoledronic acid-treated ovariectomized rats. Materials and Methods: Twenty-one 10-week-old female Wistar rats were divided into ovariectomy (OVX), OVX with zoledronic acid administration (OVX + ZOL), and sham operation (control) groups. Two weeks after OVX, ZOL administration was initiated. Twelve weeks after OVX, a nickel-titanium closed-coil spring of 25-g force was applied mesially to the maxillary left first molar. In vivo micro-computed tomography (CT) of the left proximal tibia was performed for bone morphometric analysis every 2 weeks after OVX. In addition, OTM was investigated using micro-CT at 0, 12, and 14 weeks after OVX. Results: There were significant differences in the bone mineral content (BMC), bone volume (BV), BMC to tissue volume ratio (BMC/TV), and BV to TV ratio of trabecular bone between the control and OVX groups and also between the OVX + ZOL and OVX groups. In the OVX + ZOL group, increased BMC and BV in the cortical bone and increased bone mineral density (BMD) in the trabecular bone were observed. Interestingly, OTM in the OVX group was almost two times more than that in the control and OVX + ZOL groups. Moreover, OTM was correlated with BMD, BMC, BV, and BMC/TV in the trabecular bone. Conclusions: OVX accelerated OTM, while ZOL suppressed it. OTM demonstrated a significant negative relationship with trabecular bone mass.
  The Angle Orthodontist 02/2013; · 1.21 Impact Factor
• Source

  Available from: Carmen Beatriz Gonzales

  Article: Orthodontic tooth movement and root resorption in ovariectomized rats treated by systemic administration of zoledronic acid.

  Irin Sirisoontorn, Hitoshi Hotokezaka, Megumi Hashimoto, Carmen Gonzales, Suwannee Luppanapornlarp, M Ali Darendeliler, Noriaki Yoshida
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  ABSTRACT: The effect of zoledronic acid, a potent and novel bisphosphonate, on tooth movement and orthodontically induced root resorption in osteoporotic animals systemically treated with zoledronic acid as similarly used in postmenopausal patients has not been elucidated. Therefore, this study was undertaken. Fifteen 10-week-old female Wistar rats were divided into 3 groups: ovariectomy, ovariectomy + zoledronic acid, and control. Only the ovariectomy and ovariectomy + zoledronic acid groups underwent ovariectomies. Two weeks after the ovariectomy, zoledronic acid was administered only to the ovariectomy + zoledronic acid group. Four weeks after the ovariectomy, 25-g nickel-titanium closed-coil springs were applied to observe tooth movement and orthodontically induced root resorption. There were significant differences in the amounts of tooth movement and orthodontically induced root resorption between the ovariectomy and the control groups, and also between the ovariectomy and the ovariectomy + zoledronic acid groups. There was no statistically significant difference in tooth movement and orthodontically induced root resorption between the ovariectomy + zoledronic acid and the control groups. Zoledronic acid inhibited significantly more tooth movement and significantly reduced the severity of orthodontically induced root resorption in the ovariectomized rats. The ovariectomy + zoledronic acid group showed almost the same results as did the control group in both tooth movement and orthodontically induced root resorption. Zoledronic acid inhibits excessive orthodontic tooth movement and also reduces the risk of severe orthodontically induced root resorption in ovariectomized rats.
  American journal of orthodontics and dentofacial orthopedics: official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics 05/2012; 141(5):563-73. · 1.33 Impact Factor
• Source

  Available from: Carmen Beatriz Gonzales

  Article: Tooth movement and root resorption; the effect of ovariectomy on orthodontic force application in rats.

  Irin Sirisoontorn, Hitoshi Hotokezaka, Megumi Hashimoto, Carmen Gonzales, Suwannee Luppanapornlarp, M Ali Darendeliler, Noriaki Yoshida
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  ABSTRACT: To quantify the amount of tooth movement and orthodontically induced root resorption (OIRR) in ovariectomized rats. Five 10-week-old female Wistar rats undergoing ovariectomy (OVX) were investigated as the experimental group, and the other five without ovariectomy served as the control group. Four weeks after ovariectomy, 25-g nickel-titanium closed-coil springs were applied mesially to the maxillary left first molars. Micro-computed tomography was taken at day 0, 1, 3, 7, 14, 21, and 28. At day 28, the molars were extracted. The surface area of root resorption craters, depth, and volume were measured using electron and laser scanning microscopes. Tooth movement gradually increased with time throughout 28 days. There was a significant difference in the amount of tooth movement between the control group and the OVX group. For OIRR, the OVX group showed wide and shallow root resorption craters scattered on the mesial root. The deep resorption craters were observed on the distal roots distributed in the cervical, middle, and apical thirds of the roots. Statistically significant differences were found between the control and the OVX groups in the depth and the volume of root resorption craters in the distal roots and the total volume of root resorption craters in all three roots. Ovariectomy affected not only tooth movement but also OIRR. Tooth movement in the OVX group was more rapid than the control group. Furthermore, the amount of OIRR in the OVX group was more severe than the control group.
  The Angle Orthodontist 03/2011; 81(4):570-7. · 1.21 Impact Factor