K Soma

Chulalongkorn University, Bangkok, Bangkok, Thailand

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Publications (185)227.87 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The jaw-opening reflex (JOR) plays an important role in the regulation of jaw movement during mastication. Previous study showed that altered masticatory function during growth impedes JOR maturation and thus may affect masticatory performance in adults. However, no studies have compared the benefit of early and delayed correction in terms of functional development. Therefore, this study tested the hypothesis that early-stimulation of masticatory function during growth can promote JOR maturation better than late-stimulation during adulthood. Soon after weaning, 120 female Wistar rats were divided into two groups and fed either solid (control group) or liquid (experimental group) diets. The experimental group was further divided into early-, late-, and non-stimulation subgroups. Early- and late-stimulation groups were fed a solid diet instead of a liquid diet at 5- and 11-week-old, respectively, whereas non-stimulation group was fed only a liquid diet until the end of the experiment. At 3, 5, 7, 9, 11 and 13 weeks, JOR recordings were conducted in anaesthetised rats of all groups. Latency and peak-to-peak amplitude of the JOR were compared between the groups. From 7 to 13 weeks, early-stimulation group showed a JOR with short latency and high amplitude similar to that of control group. In contrast, late- and non-stimulation groups showed significantly longer latency and smaller amplitude of the JOR than in control group. We demonstrated that early masticatory stimulation within the critical period for programming mastication may have greater potential to restore JOR maturation to values close to those in normal adults.
    Journal of Oral Rehabilitation 09/2012; · 2.34 Impact Factor
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    ABSTRACT: Aim: An onplant is an orthodontic anchorage device fixed to the bone surface with osseointegration. Compared with implants, the onplant has fewer limitations regarding placement and is less invasive. The purpose of this study was to clarify the effect of bone-surface treatment and the fixing method of a newly designed smaller-sized onplant and establish a prospective surgical procedure for placement of the onplant. Methods: Thirty-eight onplants were placed in six beagle dogs. The bone surface was planed where the cortical bone was thick and reducible (bone-planed). Where the cortical bone was thin and uneven, a filling was inserted in the space between the onplant and bone (filled). The onplant was fixed to the bone in one of two ways: using a membrane that covered the onplant and fixing the membrane with titanium pins (membrane-fixed) or fixing the onplant directly to the bone using the same titanium pins (pin-fixed). Results: Twelve weeks later, all the onplants were osseointegrated. The bone-planed group showed significantly (P < .05) larger shear stress than the filled groups. In the bone-planed group, the pin-fixed group showed significantly (P < .05) larger shear stress than the membrane-fixed group. The shear stresses were considered strong enough to function in orthodontic treatment. Conclusion: The effect of the bone-surface treatment and the onplant-fixing method on the shear stress was clarified, and the findings in the present study may be useful for the improvement of surgical procedures for orthodontic onplants.
    Orthodontics : the art and practice of dentofacial enhancement. 01/2012; 13(1):216-25.
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    ABSTRACT: Bone is maintained by continuous bone formation by osteoblasts provided by proliferation and differentiation of osteoprogenitors. Parathyroid hormone (PTH) activates bone formation, but because of the complexity of cells in the osteoblast lineage, how these osteoprogenitors are regulated by PTH in vivo is incompletely understood. To elucidate how signals by PTH in differentiated osteoblasts regulate osteoprogenitors in vivo, we conducted bone marrow ablation using Col1a1-constitutively active PTH/PTHrP receptor (caPPR) transgenic mice. These mice express caPPR specifically in osteoblasts by using 2.3 kb Col1a1 promoter and showed higher trabecular bone volume under steady-state conditions. In contrast, after bone marrow ablation, stromal cells recruited from bone surface extensively proliferated in the marrow cavity in transgenic mice, compared to limited proliferation in wild-type mice. Whereas de novo bone formation was restricted to the ablated area in wild-type mice, the entire marrow cavity, including not only ablated area but also outside the ablated area, was filled with newly formed bone in transgenic mice. Bone mineral density was significantly increased after ablation in transgenic mice. Bone marrow cell culture in osteogenic medium revealed that alkaline phosphatase-positive area was markedly increased in the cells obtained from transgenic mice. Furthermore, mRNA expression of Wnt-signaling molecules such as LRP5, Wnt7b, and Wnt10b were upregulated after marrow ablation in bone marrow cells of transgenic mice. These results indicate that constitutive activation of PTH/PTHrP receptor in differentiated osteoblasts enhances bone marrow ablation-induced recruitment, proliferation, and differentiation of osteoprogenitors.
    Journal of Cellular Physiology 08/2011; 227(2):408-15. · 4.22 Impact Factor
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    ABSTRACT: The objective of this study was to explore factors associated with hara-kiri as a method of suicide and suicidal behavior in contemporary Japan. A retrospective study was conducted on medical records of 421 patients (174 male; 247 female) who were considered suicidal and treated at the Kitasato University Hospital Emergency Medical Center in Japan between January 2006 and March 2008. We compared hara-kiri and all other methods regarding sociodemographics and clinical features of all suicidal patients. Instances of hara-kiri suicide attempt had the highest proportion of males (63%) among all suicide and suicidal behavior. One-way analysis of variance revealed significant differences between hara-kiri and other suicide attempt methods in the age of the suicidal patients. Result of multiple logistic regression analysis indicated that those who attempted hara-kiri suicide were likely to be male, be diagnosed with schizophrenia, survive, and be married. Our findings indicate that hara-kiri as a method of suicide and suicidal behavior remains prevalent in Japan, and the study findings also suggest that both clinical and cultural factors might play a role in hara-kiri as a method of suicide and suicidal behavior.
    European Psychiatry 11/2010; 25(7):409-13. · 3.29 Impact Factor
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    ABSTRACT: The purpose of this study was to clarify the frontal chewing patterns of various crossbite malocclusions. 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. 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. 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.
    American journal of orthodontics and dentofacial orthopedics: official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics 09/2010; 138(3):323-9. · 1.33 Impact Factor
  • Mona A Abbassy, Ippei Watari, Kunimichi Soma
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    ABSTRACT: The aim of this study was to assess the effect of type 1 diabetes mellitus (DM) on the structure of mandibular bone and on the changes of alveolar/jaw bone formation. Experimental DM was induced in 3-wk-old male Wistar rats by a single dose of 60 mg/kg body weight of streptozotocin. All rats were injected with calcein on days 21 and 28. The rats were killed when 8 wk of age. Bone structure was analyzed by bone histomorphometry, microcomputed tomography (micro-CT), and histological section. Histomorphometric analysis showed that the mineral apposition and the bone formation rates in most of the mandibular regions were significantly decreased in the DM group compared with the control group. Micro-CT analysis showed significant deterioration of the bone quality in rats with DM. For a histometric measure of bone resorption, the number of osteoclasts along the distal surface of the alveolar wall was counted. The number of osteoclasts was significantly lower in the rats with DM than in the controls. These findings suggest that uncontrolled DM decreases mandibular bone formation, reduces the rate of bone turnover in the alveolar wall surrounding the root, and affects the quality of bone structure resulting in retardation of its skeletal development.
    European Journal Of Oral Sciences 08/2010; 118(4):364-9. · 1.42 Impact Factor
  • Emi Oie, Mariko Horiuchi, Kunimichi Soma
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    ABSTRACT: To examine changes in gravity fluctuation caused by experimentally altering the area of occlusal contact. Subjects consisted of 15 adult Japanese males with normal stomatognathic function, no missing teeth except for the third molars, and equivalent occlusal contact in the anterior and bilateral posterior regions. Silicon biteplates fabricated for each subject to evaluate gravity fluctuation in relation to changes in occlusal contact area were as follows: RP(-)-OC(+) (entire occlusal surface covered in centric occlusion); RP(+)-OC(+) (entire occlusal surface covered with bite slightly raised); Ant or Pos/RP(+)-OC(+) (anterior or posterior region selectively covered); and RP(+)-OC(-) (only retromolar pads covered, no occlusal coverage). No significant differences in gravity fluctuation were noted between subjects wearing biteplates covering the entire occlusal surface. Subjects wearing biteplates with no occlusal contact showed greater gravity fluctuation than those with occlusal contact. In addition, gravity fluctuation for the Ant/RP(+)-OC(+) group (no occlusal contact in the posterior region) was greater than for RP(+)-OC(+) and Pos/RP(+)-OC(+). However, groups with unilateral occlusal contact in the posterior region exhibited large right and left sway amplitude. These results suggest that occlusal contact, especially posterior occlusal contact, affects gravity fluctuation, and that appropriate occlusion attained by maintaining even occlusal contact in the posterior region is crucial for gravity fluctuation.
    The Angle Orthodontist 05/2010; 80(3):540-6. · 1.18 Impact Factor
  • Hangsul Jung, Mariko Horiuchi, Kunimichi Soma
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    ABSTRACT: To analyze the age-dependent changes in nerve fibers immunoreactive to calcitonin gene-related peptide (CGRP-ir) in the periodontal ligaments of rats. Thirty male Wistar-ST rats were divided into growing groups (5, 9, and 15 weeks of age) and aging groups (6, 12, and 24 months of age) (n = 5 in each group). Eight serial sagittal sections, 5 microm thick, were cut parallel to the distobuccal root of the maxillary right first molar. These tissues were stained with a rabbit monoclonal antibody against CGRP. The observation area was divided into three parts (mesial, apical, and distal) and observed using a light microscope. CGRP-ir nerve fibers were primarily distributed in the apical periodontal ligament in the growing group, with significantly more fibers than in the aging group. CGRP-ir nerve fibers in the periodontal ligament are dense during the growth period and decrease gradually with aging, indicating that CGRP may affect periodontal tissue with growth and aging.
    The Angle Orthodontist 03/2010; 80(2):309-15. · 1.18 Impact Factor
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    ABSTRACT: To examine the influence of occlusal stimuli on the vasculature in the dental pulp, using an occlusal hypofunction model. Twenty 7-week-old male Sprague-Dawley rats were divided into two groups. To produce occlusal hypofunction, the appliances were attached to the maxillary and mandibular incisors. Untreated rats served as controls. Serial horizontal paraffin sections of the mandibular first molar were processed by conventional methods. To evaluate the microvasculature in the dental pulp, sections of each specimen were stained with hematoxylin-eosin. In the experimental group, the arterioles in the tooth pulp tissue ran convergently, and their inside diameter was significantly smaller than that of the control group. This study suggests that occlusal stimuli influence the periodontal ligament throughout the microvasculature of the dental pulp.
    The Angle Orthodontist 03/2010; 80(2):316-21. · 1.18 Impact Factor
  • Mona A Abbassy, Ippei Watari, Kunimichi Soma
    European Journal Of Oral Sciences 01/2010; · 1.42 Impact Factor
  • Toxicology Letters - TOXICOL LETT. 01/2010; 196.
  • Aya Kurusu, Mariko Horiuchi, Kunimichi Soma
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    ABSTRACT: To clarify the relationship between occlusal force and mandibular condyle morphology using clinical data. The subjects were 40 female patients with malocclusion. The mandibular condyle morphology was assessed by using limited cone-beam CT imaging. The maximum occlusal force was calculated by using pressure-sensitive films. Maxillofacial morphologies were analyzed by using data from lateral cephalograms. Correlation analysis showed that the occlusal force was correlated with the lateral and posterior radii of the condyles, and with the mandibular plane angle to the Frankfort horizontal plane (FH). Moreover, condylar length was significantly correlated with the occlusal plane angle to the FH, the mandibular plane angle to the FH, the ramus inclination, and the posterior facial height (S-Go). Low-occlusal-force patients tended to have smaller mandibular condyles. This size-related difference was more remarkable on the lateral and posterior side. Occlusal force influences not only maxillofacial morphology but also mandibular condyle morphology.
    The Angle Orthodontist 11/2009; 79(6):1063-9. · 1.18 Impact Factor
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    ABSTRACT: To determine the influence of masseter muscle activity during growth on the functional characteristics of temporomandibular joint (TMJ) mechanoreceptors. Sixty-six 3-week-old male Wistar rats were divided into an experimental group, in which the masseter muscles were bilaterally resected at 3 weeks of age, and a control group. Single-unit activities of the TMJ mechanoreceptors were evoked by indirect stimulation of passive jaw movement. Electrophysiologic recordings of TMJ units were made at 5, 7, and 9 weeks of age. During this period, the firing threshold of the TMJ units was significantly lower and the maximum instantaneous frequency of the TMJ units was significantly higher in the experimental group than in the control group. Reduced masseter activity during the growth period alters the response properties of TMJ mechanoreceptors.
    The Angle Orthodontist 10/2009; 79(5):978-83. · 1.18 Impact Factor
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    ABSTRACT: To test the hypothesis that the effects of mechanical stress from a functional lateral shift of the mandible have no effect on the expression of two main condylar cartilage extracellular matrix components, type II collagen and aggrecan, in rats from early puberty to young adulthood. Functional lateral shift of the mandible was induced in experimental groups of 5-week-old male Wistar rats, using guiding appliances. The rats were sacrificed at 3, 7, 14, and 28 days post appliance attachment. The condyles were immunohistochemically evaluated for type II collagen and aggrecan (the immunoreactive areas were quantified). As compared with the control group, on the contralateral condyles, the immunoreactivity of the experimental groups was significantly increased from 7 to 14 days. While on the ipsilateral condyles, the immunoreactive areas were significantly decreased throughout the experimental period. A functional lateral shift of the mandible modulated the condylar cartilage extracellular matrix differently on each side of the condyle, which affected condylar morphology, growth, biomechanical properties, and even the susceptibility of the condylar cartilage to pathogenesis.
    The Angle Orthodontist 08/2009; 79(4):652-9. · 1.18 Impact Factor
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    ABSTRACT: Objectives: The understanding of mandibular growth is important in the practice of clinical orthodontics. This may have a considerable impact on diagnosis, treatment planning and the eventual outcome of orthodontic treatment. The goal of this study was to assess the effect of Type 1 diabetes mellitus (T1DM) on the mandibular growth and the quality of mandibular bone using the Streptozotocin diabetic rat model. Methods: Experimental T1DM was induced in 3-week old male Wistar rats by a single dose of 60mg/kg body weight of streptozotocin (STZ). Body weights, the presence of glucose in urine and blood glucose levels were recorded on day 0,2,7,14,21 and 28 after STZ injection. All rats were injected with calcein. After sacrifice the right mandible was dissected and qualitative analysis of the mandibular bone structure was imaged by micro-CT (inspeXio, Shimadzu, Tokyo), and evaluated using an automated image analyzer (TRI/3D-BON, Ratoc, Japan). Bone histomorphometric analysis was evaluated using double labeled frontal section of mandibular second molar. Quantitative analysis of bone formation was done using a digitizing morphometry system which consisted of a confocal laser scanning microscope (LSM510, Carl Zeiss, Germany). Mann-Whitney U-test was used to analyze the rate of bone formation, while micro-CT results were analyzed with t-test (p<0.05). Results: In STZ-DM rats micro-CT analysis showed the significant decrease of bone volume, bone surface and all the trabecular properties indicating the deterioration of the bone quality in T1DM. Histomorphometric analysis showed the tendency of decrease of bone formation during the growth period. Conclusion: T1DM reduces mandibular bone formation, and affects the quality of bone structure resulting in retardation of skeletal development. These findings should be considered when orthodontic problems are diagnosed and treated in T1DM. A better understanding of how diabetes affects bone will improve our ability to protect bone health during orthodontic treatment in diabetic patients.
    IADR General Session 2009; 04/2009
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    ABSTRACT: To test the null hypothesis that alteration in masticatory function due to liquid-diet feeding during growth does not affect jaw-opening reflex (JOR) maturation. Soon after weaning, 70 female Wistar rats were divided into two equal groups and fed either solid (control group) or liquid (experimental group) diets. At 5, 9, and 13 weeks, the rats were anesthetized and the JOR was recorded in the anterior belly of the digastric muscles as evoked by a low-intensity electrical stimulation of the left inferior alveolar nerve. There were similar tendencies at each recording age. Peak-to-peak amplitude of the JOR was significantly smaller, and the latency was significantly longer in the experimental group, although the duration was not significantly different between the two groups. These data suggest that long-term masticatory functional change due to liquid-diet feeding during growth may impede the learning for JOR maturation, and thus may affect the masticatory performance in the adult.
    The Angle Orthodontist 04/2009; 79(2):299-305. · 1.18 Impact Factor
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    ABSTRACT: Load during mastication is an important factor for the development and maintenance of mechano- receptor properties. The purpose of this study was to examine property changes in the rat TMJ mechano-receptors under conditions of liquid diet feeding and low articular load during the growth period. The hypothesis was that alterations in mastication of liquid diet might increase TMJ mechano-receptor sensitivity. Sixty-six two-week-old male Wistar rats were divided into two groups: a control group that was fed on whole pellets, and an experimental group that was fed a liquid diet. Electrophysiological recordings from the TMJ units were obtained from the trigeminal ganglion when the rats were 5, 7, and 9 weeks old. In the experimental group, TMJ mechanoreceptor sensitivity increased, because the firing threshold gradually decreased and the maximum instantaneous frequency gradually increased. In conclusion, functional properties of TMJ mechano-receptors under low articular loading conditions cannot mature normally within the growth period.
    Journal of dental research 03/2009; 88(2):187-91. · 3.46 Impact Factor
  • Hiroko Ohmori, Hiroaki Kirimoto, Kunimichi Soma
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    ABSTRACT: To date, a number of needle electrodes have been used to measure motor unit action potentials (MUAPs) during masticatory muscle activity. On the other hand, surface electrodes are non-invasive and simple to use, but it is necessary to analyze recorded composite wave data to determine MUAPs. Herein, we describe an improved non-invasive surface electrode with improved capability for capturing masticatory muscle MUAP. We investigated the characteristics and clinical application of this electrode. Surface array electrodes comprised silver–silver chloride electrode poles (1mm in diameter and 5mm in length) fixed by silicon, which were smaller than previous surface array electrodes. The electrode potential and the impedance measured in physiological saline at 25°C were 69mV (stable over time) and 415Ω, respectively. The MUAP was measured in a human masseter muscle using this electrode, and was found to be fairly constant over time. Thus, the electrode fulfilled the criteria necessary for measuring MUAPs.
    Orthodontic Waves 01/2009; 68(2):57-63.
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    ABSTRACT: We previously reported a 65-year-old man who aspirated an alkaline detergent containing 3.3% w/v (weight of solute per volume of solution) monoethanolamine (MEA) into his lungs, causing asthma-like symptoms. We presently describe the mechanism of MEA-induced bronchoconstriction according to findings in guinea pigs. In anesthetized, artificially ventilated animals, changes in airway opening pressure (P(ao)) were measured as an index of bronchoconstriction. An aerosol of 3.3% MEA solution (0.1 ml kg(-1)) inhaled through a tracheal cannula induced significantly stronger bronchoconstriction than an aerosol of potassium hydroxide (KOH) solution (0.1 ml kg(-1)) at the same pH. MEA-induced bronchoconstriction was significantly suppressed by premedication with intravenously injected atropine sulfate (3 mg kg(-1)), a muscarinic receptor antagonist, or diphenhydramine hydrochloride (10 mg kg(-1)), a histamine-H(1) receptor antagonist. MEA-induced bronchoconstriction was not enhanced by premedication with an intravenous injection of neostigmine (0.1 mg kg(-1)), an acetylcholinesterase inhibitor. When bronchoconstriction was induced by MEA, histamine concentrations in bronchoalveolar lavage fluid (BALF) were not significantly greater than in BALF after KOH-induced bronchoconstriction or in BALF after inhalation of physiologic saline. In vitro, contraction of trachea denuded of epithelium during superfusion with MEA (10 mm) was suppressed by premedication with pyrilamine maleate, a histamine-H(1) receptor antagonist, at 10 and 100 microm. Contraction of trachea denuded of epithelium during superfusion with MEA (10 mm) was suppressed by premedication with atropine sulfate at 10 and 100 microm. These results suggest that asthma-like symptoms may result partly from agonistic MEA effects at histamine-H(1) receptors and muscarinic receptors.
    Journal of Applied Toxicology 01/2009; 29(1):15-9. · 2.60 Impact Factor
  • Journal of Vascular and Interventional Radiology - J VASC INTERVEN RADIOL. 01/2009; 20(2).

Publication Stats

1k Citations
227.87 Total Impact Points

Institutions

  • 2012
    • Chulalongkorn University
      • Department of Orthodontics
      Bangkok, Bangkok, Thailand
  • 1992–2011
    • Tokyo Medical and Dental University
      • • Department of Molecular Pharmacology
      • • Department of Orofacial Development and Function
      • • Faculty of Dentistry
      • • Department of Orthodontics
      Edo, Tōkyō, Japan
  • 2010
    • Peking University
      • Department of Orthodontics
      Beijing, Beijing Shi, China
  • 2008
    • Jilin University
      Yung-chi, Jilin Sheng, China
  • 2007
    • Yonsei University
      • Department of Orthodontics
      Seoul, Seoul, South Korea
    • Massachusetts General Hospital
      • Endocrine Unit
      Boston, Massachusetts, United States
  • 2006
    • Chiang Mai University
      • Department of Orthodontics
      Chiang Mai, Chiang Mai Province, Thailand
  • 2004
    • Yokohama City University
      • Advanced Critical Care and Emergency Center
      Yokohama, Kanagawa, Japan
  • 1993–2002
    • Kitasato University
      • • Department of Emergency and Critical Care Medicine
      • • Medical Department
      Edo, Tōkyō, Japan