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Biomedical subjects

S Hiyama

Publications and source records attributed to S Hiyama.

15 recordsLinked to original sources
PubMed2003

First night effect of an interocclusal appliance on nocturnal masticatory muscle activity.

The purpose of this study was to examine the effect of an interocclusal appliance on nocturnal masticatory muscle activities. Six healthy Japanese males (mean age: 26.8 years) participated in this study. Electromyographic (EMG) activities of the right anterior temporalis and masseter muscles were recorded using a portable EMG recording unit at night both with and without an interocclusal appliance. In both muscles, the maximal EMG activity and the number of bruxing events decreased significantly by wearing the appliance. Moreover, the duration of a higher level of muscle activity was decreased while that of a lower level of muscle activity increased by wearing the appliance in both muscles. These findings suggest that nocturnal masticatory muscle activity is significantly reduced by wearing an interocclusal appliance, and that the use of such an appliance at night could help to relax masticatory muscles.

Adult↗
PubMed2001

Effects of a titratable oral appliance on supine airway size in awake non-apneic individuals.

STUDY OBJECTIVES: To define morphological changes in the upper airway and its surrounding structures after the insertion of a titratable mandibular repositioner. DESIGN: Ten non-apneic adult males participated in this study. A set of supine lateral cephalograms was taken for each subject at the end of expiration with a titratable oral appliance in place in four mandibular positions: most retruded (RP), maximum protrusion (MAX), 33% of MAX (MAX33), and 67% of MAX (MAX67). Changes in the anteroposterior width of the upper airway, positions of the hyoid bone and the third cervical vertebra were compared between the four mandibular positions. An ANOVA was used to test for statistical significance. SETTING: N/A. PATIENTS OR PARTICIPANTS: N/A. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: The anteroposterior width of the velopharynx significantly increased when the mandible was advanced from RP to MAX67 and MAX. However, there were no significant changes in the anteroposterior width of the oropharynx. Significant forward displacement of the hyoid bone and third cervical vertebra together with the mandible was found in MAX67 and MAX compared to RP. CONCLUSION: Especially in MAX67 and MAX, the titratable oral appliance significantly enlarges upper airway size in the velopharynx and results in a forward displacement of the hyoid bone and the third cervical vertebra.

Adult↗
PubMed2001

Changes in mandibular position and upper airway dimension by wearing cervical headgear during sleep.

We previously reported that the wearing of cervical headgear induced forward displacement of the mandible in awake subjects. However, it was unclear whether such mandibular displacement also occurred during sleep. The purpose of this study was to examine changes in mandibular position and oropharyngeal structures that were induced by the wearing of cervical headgear during sleep. Ten healthy adults (7 male and 3 female) who gave their informed consent were included in this study. A pair of lateral cephalograms was taken with the patient in the supine position with and without cervical headgear at end-expiration during stage 1 to 2 non-rapid-eye-movement sleep. The Wilcoxon signed-rank test was used for a statistical analysis. The amount of jaw opening was significantly decreased by the wearing of the cervical headgear (P <.05), although no significant anteroposterior mandibular displacement was induced. The sagittal dimension of the upper airway was significantly reduced (P <.05); however, no significant changes were observed in the vertical length of the upper airway. Although the hyoid bone and the third cervical vertebra moved significantly forward by the wearing of the cervical headgear (P <.05), the relationship among the mandibular symphysis, the hyoid bone, and the third cervical vertebra did not change. These results suggest that cervical headgear significantly reduced the sagittal dimension of the upper airway during sleep, although there was no significant anteroposterior displacement of the mandible.

Adult↗
PubMed2000

Supine cephalometric study on sleep-related changes in upper-airway structures in normal subjects.

The purpose of this study was to examine sleep-related changes in the upper airway and surrounding structures including the mandible, hyoid bone, and cervical vertebra in normal subjects using lateral cephalograms in the supine position. Eleven male and nine female healthy adults participated in this study. Supine cephalograms were taken at end-expiration during wakefulness and in stage 1-2 non-rapid-eye-movement (NREM) sleep judged from the electroencephalogram and respiratory monitoring. A paired t-test was used to compare differences between the values measured during wakefulness and sleep. A significant increase in the amount of jaw opening was observed during sleep. The anteroposterior width of the upper airway was significantly decreased during sleep. The distances between the hyoid bone and the mandibular symphysis and between the cervical vertebra and the hyoid bone were significantly decreased during sleep. Consequently, the distance between the cervical vertebra and the mandibular symphysis was significantly decreased. These results suggest that the upper-airway dimension is significantly decreased and relatively small structural changes are induced during sleep in normal subjects.

Adult↗
PubMed2000

Neuromuscular and skeletal adaptations following mandibular forward positioning induced by the Herbst appliance.

The purpose of this study was to examine neuromuscular and skeletal adaptations to changes in sagittal jaw relationships induced by the Herbst appliance. Six patients (age, 9 years and 5 months to 11 years and 2 months) with Angle Class II, division 1 malocclusions were studied longitudinally. The structural changes were determined by analyzing serial lateral cephalograms. Electromyographic recordings of specific masticatory muscles were used to evaluate neuromuscular adaptations. Similar cephalometric changes were observed in all patients. In all patients, lateral pterygoid muscle activity increased immediately after insertion of the appliance, but the activity decreased markedly after 4 to 6 months of treatment. In 4 of the 6 patients studied, however, the condyles were located in a slightly more downward and forward position. These findings indicate that the adaptation of muscular function occurs within a relatively short period and precedes the compensatory morphological changes produced through functional appliance therapy.

Adaptation, Physiological↗
PubMed2000

Genioglossus muscle activity during rhythmic open-close jaw movements.

The purpose of this study was to examine genioglossus muscle activity during rhythmic open-close jaw movements. The electromyographic activity of the genioglossus muscle was recorded with a bipolar fine-wire electrode in six healthy males. The electromyographic activities of the ipsilateral masseter and digastric muscles were simultaneously recorded with bipolar surface electrodes. The subjects were instructed to perform rhythmic open-close jaw movements in time with a metronome set at 23, 27, 33, 42 and 50 beats/min. In all of the subjects, rhythmic electromyographic activity of the genioglossus muscle was recorded in both the jaw-opening and jaw-closing phases. The activity of the genioglossus muscle was predominantly recorded in the jaw-opening phase in two subjects, and in the jaw-closing phase in two subjects. The burst duration of the electromyographic activity of the genioglossus muscle changed linearly in accordance with the cycle duration. However, the latency from the onset of the electromyographic activity of the masseter or digastric muscle to that of the genioglossus muscle was almost constant, independent of the cycle duration. Based on these findings, we conclude that the activity of the human genioglossus muscle is closely linked to that of masticatory muscles under the control of a closely related central pattern generator.

Adult↗
PubMed2000

Effective treatment plan for maxillary protraction: is the bone age useful to determine the treatment plan?

A major skeletal effect of reverse-pull headgear is a forward movement of maxilla, via remodeling of the circummaxillary sutures. We hypothesized that an evaluation of bone age would help to determine the effective planning and optimum timing using reverse-pull headgear. Differences in the cephalometric measurements between the initiation of treatment and after 1 year of treatment were calculated from 60 Japanese patients in mixed dentition with skeletal Class III malocclusions. Bone age was appraised by the Tanner-Whitehouse 2 method using hand-wrist radiographs at the initiation of treatment. The control groups (mean chronologic age, male 10.3 years and female 9.6 years) were treated by lingual arch and/or chincup, and the reverse-pull headgear groups (mean chronologic age, male 9.7 years and female 9.4 years) by reverse-pull headgear. The forward movement of the maxilla and increase in the palatal length were larger in the bone age-based younger male reverse-pull headgear subgroup than in the bone age-based older male reverse-pull headgear subgroup. The increase of SNA in the male reverse-pull headgear group was significantly larger than that of the female reverse-pull headgear group, which had a more mature skeletal status than the former. In the male reverse-pull headgear group, the forward movement of the maxilla and increase in the palatal length showed significant inverse correlation with the bone age, but not with the chronologic age. These results support our hypothesis that the bone age is a useful clinical indicator to determine the effective treatment plan with reverse-pull headgear.

Adolescent↗
PubMed1999

Condylar resorption 2 years following active orthodontic treatment: a case report.

We recently treated a patient with degenerative disease of the temporomandibular joint. A healthy, 12-year-old female with bilateral high maxillary canines presented for orthodontic treatment. Two years after active orthodontic treatment, at age 17, symptoms in her temporomandibular joint manifested and progressed. By the time she revisited our hospital at age 21, the patient had developed an anterior open bite with a long, slender facial appearance. Cephalometric analysis showed shortening of the ramus and backward and downward rotation of the mandible. Imaging studies revealed severe deformity and resorption of the bilateral condyles. Her occlusal and morphologic changes seemed to be caused by degenerative disease of the temporomandibular joint.

Adolescent↗
PubMed1998

High-speed video cinematographic demonstration of stalk and zooid contraction of Vorticella convallaria.

Stalk contraction and zooid contraction of living Vorticella convallaria were studied by high-speed video cinematography. Contraction was monitored at a speed of 9000 frames per second to study the contractile process in detail. Complete stalk contraction required approximately 9 ms. The maximal contraction velocity, 8.8 cm/s, was observed 2 ms after the start of contraction. We found that a twist appeared in the zooid during contraction. As this twist unwound, the zooid began to rotate like a right-handed screw. The subsequent stalk contraction steps, the behavior of which was similar to that of a damped harmonic oscillator, were analyzed by means of the equation of motion. From the beginning of stalk contraction, the Hookean force constant increased, and reached an upper limit of 2.23 x 10(-4) N/m 2-3 ms after the start of contraction. Thus, within 2 ms, the contraction signal spread to the entire stalk, allowing the stalk to generate the full force of contraction. The tension of an extended stalk was estimated to be 5.58 x 10(-8) N from the Hookean force constant of a stalk. This value coincides with that of the isometric tension of a glycerol-treated V. convallaria, confirming that the contractile system of V. convallaria is well preserved despite glycerol treatment.

Animals↗
PubMed1998

Type A fibril of the mouse tectorial membrane shows D-periodicity: an atomic force microscopic examination.

This study demonstrated that type A fibrils of the mouse tectorial membrane showed a morphology characteristic of collagen, as demonstrated using an atomic force microscope. In the topographical imaging mode, the surface of the type A fibrils showed a periodic pattern, consisting of alternating grooves and ridges. The periodicity of the type A fibrils was 69.1 +/- 0.6 nm, which is in accordance with characteristic collagen D-periodicity. The difference in height between grooves and ridges was 1.6 +/- 0.3 nm. In the variable deflection imaging mode, the type A fibrils showed a clear banding pattern, which consisted of alternating light and dark zones, with D-periodicity. In addition, the type A fibrils exhibited one minor dark band in the light zone and one minor light band in the dark zone.

Aged↗
PubMed1997

Human jaw-tongue reflex as revealed by intraoral surface recording.

The purpose of this study was to examine if there is a human jaw-tongue reflex. This study was carried out in seven healthy adult males and recorded the genioglossus muscle activity during various functions by using a miniature intraoral surface electrode, which is comparable with intramuscular fine-wire electrodes, but without pain or disturbance of the tongue movement. The ipsilateral masseteric and digastric muscle activities were simultaneously recorded with the surface electrodes. Tonic genioglossus muscle activity was recorded during clenching. A passive jaw opening elicited the stretch reflex in the masseteric muscle and increased genioglossus muscle activity. Electrical stimulation of the lower lip inhibited the tonic activity in the masseteric and genioglossus muscles during both clenching and tongue protrusion. Moreover, the latency of the inhibition in the genioglossus muscle activity was shorter during clenching than during tongue protrusion. Based on these findings, the authors conclude that the human jaw-tongue reflex exists and that the jaw-closing muscle is involved in evoking the reflex.

Adult↗
PubMed1996

[An electromyographic study on functional adaptations--associated with herbst appliance].

The purpose of this study was to examine functional muscular adaptation to changes in sagittal jaw relation by electromyography. The structural changes were induced by the Herbst appliance. The subjects consisted of four patients with Angle Class II Division 1 malocclusion. The structural changes were evaluated by lateral cephalograms. Functional muscular adaptation was evaluated by electromyogram (EMG) of masticatory muscles, including the inferior head of the lateral pterygoid (ILpt) muscle. The EMG of the ILpt muscle was recorded by using an intraoral surface electrode. The same pattern of cephalometric changes was observed in all patients. The ILpt muscle activity increased immediately after wearing the appliance just like when the construction bite position was taken. However, it reduced remarkably after 4 to 6 months in all patients. On the other hand, the superimposed cephalometric tracings indicated that the locations of the condyles related to the glenoid fossae were still more anteroinferior than their original positions 4 to 6 months after wearing the appliances in three patients. These findings seem to indicate multifactorial effects on the adaptation of the muscle function. It was concluded that functional adaptation to the newly-created morphological changes were not dependent only on the intensity and the duration of the functional stimulation.

Adaptation, Physiological↗