| Research Abstract |
A) The genioglossus (GG) muscle shows a phasic inspiratory activity superimposed on tonic activity to maintain upper airway (UA) patency. However, discharge properties of single GG motor unit (MU) with respiratory-related activity remain to be determined. Single unit activities of 24 GG MUs with respiratory-related discharge were recorded during spontaneous nasal breathing in both the natural head position and 30ﾟ head-up position in 8 adult males. The inspiratory MU (IMU) showed the phasic activity during inspiration, whereas the inspiratory-expiratory MU (IEMU) showed the phasic inspiratory activity superimposed on the tonic activity. The firing duration and instantaneous firing frequency (1FF) of the IMU during inspiration significantly increased in the 30ﾟ head-up position. Although the 1FF of the IEMU also significantly increased in the 30ﾟ head-up position, there was no significant difference between inspiratory and expiratory phases. An interspike interval analysis demonstrated
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that the functional divergence of the IMU and IEMU.
B) (1) To investigate morphologic changes in oropharyngeal structures in mandibular prognathic patients after or thognathic surgery, 25 patients with mandibular prognathism who had undergone surgical and or thognathic treatment were used. A set of 4 standardized lateral cephalograms were obtained from each subject preoperatively and at 3 months, 6 months, and I year postoperatively. Morphologic changes in UA structures were evaluated longitudinally by gender. Parameters of the anteroposterior width of the pharynx significantly decreased at 3 and 6 months in both genders, and these parameters tended to rebound to the preoperative values 1 year postoperatively in females, but not in males. The hyoid hone significantly descended inferiorly 1 year postoperatively in males, white there were no significant changes in females. The distance between the hyoid bone and the third vertebra gradually decreased in males postoperatively ; however, there were no significant changes in females. The cross-sectional area of the hypopharynx significantly decreased 1 year postoperatively in males, but not in females. These results indicate that the UA morphology changed differently in males and females following surgery. To compensate fro skeletal changes following surgery, it appears that males and females responded in differently ways to preserve a functional UA.(2) To extract characteristic three-dimensional dentofacial changes during retention and to clarify morphological factors affecting the stability of postoperative occlusion in mandibular prognathic patients with open bite and asymmetry, 7 adult patients were used. Changes in denture and skeletal components, and anterior occlusion during retention were analyzed three-dimensionally using the lateral and frontal cephalograms. Results indicated that it was important to maintain long-term stability of the anterior occlusion in the vertical dimension in patients with three-dimensional dentofacial deformity.
C) (1) To investigate the relationship between the etiologic factors such as gender, age, and general joint mobility and temporomandibular joint (TMJ) disorders, 110 orthodontic patients were used. Fifty of 78 females and 17 of 32 males showed symptoms of TMJ disorders. No significant gender difference was observed in the prevalence of TMJ disorders. However, TMJ and muscular pain and difficulty in mouth opening were more frequently observed in female symptomatic patients than male patients. There was a significant relative risk of TMJ disorders associated with increasing age. Higher score of general joint mobility was also significantly associated with an increased risk of TMJ disorders. (2) The frequency of TMJ disorders in 174 patients with jaw deformities was surveyed by questionnaires and dental casts. The frequency of reported present or past TMJ disorders was 77.6%. No difference by gender was observed. When the frequency of TMJ disorders in different age groups was examined, the youngest being 15 years of age followed by others at increasing age intervals of 5 years, there was no significant difference between age groups. Among 135 symptomatic patients, 49 patients (36.3%) reported only one symptom of TM) disorders, while 86 patients (63.7%) reported two or more symptoms. As for potential etiologic factors and historical events, poor posture and experience of trauma were more frequently observed among symptomatic patients than asymptomatic patients. There was no significant difference in the frequency of TMJ disorders between different occlusomorphologic types. Less
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