Hiroko Ohmori

Differences in Velopharyngeal Structure during Speech among Asians Revealed by 3-Tesla Magnetic Resonance Imaging Movie Mode

Objective. Different bony structures can affect the function of the velopharyngeal muscles. Asian populations differ morphologically, including the morphologies of their bony structures. The purpose of this study was to compare the velopharyngeal structures during speech in two Asian populations: Japanese and Thai. Methods. Ten healthy Japanese and Thai females (five each) were evaluated with a 3-Tesla (3 T) magnetic resonance imaging (MRI) scanner while they produced vowel-consonant-vowel syllable (/asa/). A gradient-echo sequence, fast low-angle shot with segmented cine and parallel imaging technique was used to obtain sagittal images of the velopharyngeal structures. Results. MRI was carried out in real time during speech production, allowing investigations of the time-to-time changes in the velopharyngeal structures. Thai subjects had a significantly longer hard palate and produced shorter consonant than Japanese subjects. The velum of the Thai participants showed significant thickening during consonant production and their retroglossal space was significantly wider at rest, whereas the dimensional change during task performance was similar in the two populations. Conclusions. The 3 T MRI movie method can be used to investigate velopharyngeal function and diagnose velopharyngeal insufficiency. The racial differences may include differences in skeletal patterns and soft-tissue morphology that result in functional differences for the affected structures.

Unilateral scissors bite treated with a removable plate that incorporates a Ti-Ni wire.

A plate that incorporates a Ti-Ni alloy wire can rapidly correct scissors bite. This article describes its use in the successful treatment of scissors bite. A female patient aged 7 years, 5 months with mixed dentition presented with a Class I molar relationship, Class I skeletal pattern, and average Frankfort-mandibular plane angle. The maxillary right central incisor was in a crossbite. A unilateral posterior scissors bite was also present on the left side. The plate was fitted and prescribed for nighttime wear. Positive overjet was achieved after 1 month of treatment. The posterior scissors bite was corrected after 3 months of treatment, and the midline shift was ameliorated. Because a Ti-Ni wire maintained a weak continuous force, the treatment period was minimized.

Characteristics and clinical application of a surface array electrode for recording masticatory muscle motor unit action potentials

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 (1 mm in diameter and 5 mm 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 69 mV (stable over time) and 415 Ω, 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.

Comparison of the Physiological Properties of Human Periodontal-Masseteric Reflex Evoked by Incisor and Canine Stimulation

Introduction: The present study was designed to clarify whether the bilateral cooperation in the human periodontal-masseteric reflex (PMR) differs between central incisors and canines. Methods: Surface array electrodes were placed on the bilateral masseter muscles to simultaneously record the firing activities of single motor units from both sides in seven healthy adults. During light clenching, mechanical stimulation was applied to the right maxillary central incisor and canine to evoke the PMR. Unitary activity was plotted with respect to the background activity and firing frequency. The slope of the regression line (sRL) and the correlation coefficient (CC) between the central incisor and canine and the lateral differences between these values were compared. Results: There were significant differences in the sRL and CC, as well as lateral differences, between the central incisor- and canine-driven PMR. Discussion: These results suggest that the PMR differs depending on both the tooth position and laterality.

Bilateral asymmetries in periodontal-masseteric reflex activity in man

Abstract Jaw reflexes are evoked bilaterally even when stimulated unilaterally. This bilateral cooperation is one of the characteristics of jaw reflexes. The periodontal-masseteric reflex also shows this bilateral cooperation. The mechanism underlying bilateral cooperation in the periodontal-masseteric reflex, however, still remains unclear. The present study was designed to clarify this mechanism. In order to investigate whether there are bilateral differences in the sensitivity of the periodontal-masseteric reflex, the reflexes were recorded in five healthy subjects using surface array electrodes placed bilaterally. A 0.5 N mechanical stimulation applied to the upper canine teeth evoked a reflex in the ipsilateral and contralateral masseter muscles at a background activity of 10% maximum voluntary contraction. These were obtained at a visually controlled, constant clenching level. There was no significant difference in masseter muscle background activity between sides, but the reflex response was different between the right and left sides. These results together suggest that there is no right and left difference in the response characteristic of the masseter muscle, but that a masticatory muscle feedback mechanism, from periodontal-mechanoreceptor and the masseter muscle spindle, exists. These findings suggest that the periodontal-masseteric reflex is different between the right and left sides, and that it appears to be involved in the reflex control of masticatory movement.

Associations among TMDs, craniofacial morphologies and premature contact in female adult patients with malocclusion

approximately one-half and one-third those of stainless steel wire and cobalt–chromium–nickel alloy wire, respectively. For a cyclic bending test, stainless steel wire, cobalt–chromium– nickel alloy wire, and beta-titanium alloy-2 wire did not fracture even after 10,000 times of bending cycles, although beta-titanium alloy-1 wire fractured after 4500 bending cycles. Orthodontic forces delivered by a quad helix made from both betatitanium alloy wires were lower than those for stainless steel wire and cobalt–chromium–nickel alloy wire.

Gastric emptying rate in subjects with malocclusion examined by [13C] breath test

Masticatory function is significantly lower in individuals with malocclusion than in those with normal occlusion. Although several studies suggest that masticatory function influences gastrointestinal digestive function, the relationship between malocclusion and gastrointestinal symptoms has not been studied extensively. The purpose of this study was to investigate masticatory function and gastric emptying rate in subjects with malocclusion. Eleven healthy dentate female volunteers and eleven female patients with malocclusion underwent a C-acetate breath test with a liquid meal. Maximum CO2 exhalation time (Tmax) was compared statistically between both groups. Masticatory function was assessed by color-changeable chewing gum. The CIE L*a*b color system was used for color recording. The mean Tmax of the malocclusion group was significantly longer than that of the normal occlusion group. Masticatory performance, measured by color changeable gum and questionnaires, was significantly lower in the malocclusion group than in the normal occlusion group. This study suggested that there was a close relationship between malocclusion and gastrointestinal digestive function.