Jaw movements have been analyzed widely in the past (1) for understanding the kinematics of jaw movements, (2) for porsthodontic reasons, and more recently (3) for diagnosing the stomatognathic function and evaluating the clinical outcome of treatment. However, there has been absence of the well-established measurement method of jaw movements that can satisfy dental clinicians. One of the reasons for the difficulties of studies on jaw movements is that they have to be measured and analysed in six degree of freedom. Furthermore a high-performance computer has been essential for studies of jaw movements including dynamic occlusion or occlusal contacts being made during jaw movement. The development of computer technology over recent years has made it possible for researchers to obtain useful information that is necessary and sufficient for studies on jaw movements.
I hope that the results of the past, present and future studies on jaw movements by many researchers will greatly contribute to improve the quality of life of patients with jaw movement-related problems in the near future.

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Pain and tactile sensation have an interactive relationship, i.e. pain inhibits or facilitates tactile sensation, while tactile sensation inhibits pain sensation. Therefore, TMDs are generally given for pain disorders in the orofacial region that are possibly related to occlusal discomfort. Also, it is clinically reported that psychiatric distress possibly affects to the occlusal discomfort.
In this study, we attempted to clarify the relationships between awareness of occlusal comfort and TMD symptoms such as TMJ-noise, TMJ-pain, and jaw movement difficulty, as well as occlusal and psychiatric conditions. The subjects were 135 students. First, we examined TMD symptoms using a diagnostic process composed of an interview and examination, then we classified the subjects into 3 groups; non-symptomatic (n=69), TMJ-noise (n=45), and jaw movement related TMJ-pain (n=21) . In a comparison with the non-symptomatic group, the results of a numerical rating scale (NRS) showing the awareness of TMD symptoms indicated that those with jaw movement related TMJ-pain had significantly aggravated awareness of TMJ-noise, jaw movement related TMJ-pain, and jaw movement difficulty, while the TMJ-noise group had significant aggravated awareness of jaw movement related TMJ-pain and jaw movement difficulty. In addition, subjects with jaw movement related TMJ-pain had a significant decrease in awareness of occlusal comfort demonstrated in NRS findings as compared with the non-symptomatic group, even though there was no significant difference of occlusal contact statues among non-symptomatic, TMJ-noise, and TMJ-pain groups.
Next, the 135 subjects were classified into 2 groups, healthy (0-7 points, n=71) and anxiety suspected (8 points or more, n=64), based on anxiety scores obtained with the Hospital Anxiety and Depression Scale (HADS) . NRS results showed that subjects in the anxiety suspected group tended to have an aggravated awareness of occlusal comfort as compared with those in the healthy group, even though there was no significant difference of occlusal contact statues and awareness of TMD symptoms between healthy and anxiety groups.
Based on our results, we concluded that awareness of occlusal comfort may be modulated accompanying with the aggravated TMD symptoms such as the occurrence of TMJ pain and anxiety and depression mood states.

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Objective: When evaluating swallowing function using MRI, sequences with an extremely short repetition time using an ultra-high-speed applied voltage pulse are required, such as steady-state free precession sequences (SSFP) . In SSFP sequences, the flip angle used determines the level of noise and contrast in various tissues, which in turn determine the quality of the dynamic image of the swallowing process. Thus, we investigated the effects of flip angle on signal intensity and potential for visual evaluation of the tissues involved in swallowing during the resting state. We conclude by identifying an optimal flip angle for evaluation of swallowing function.
Methods: Seven dentulous adults (average age 30.1 years) without any abnormality in stomatognathic function participated in this study. Images of the subjects were obtained with a 1.5-Tesla superconducting MRI unit using SSFP pulse sequences. To capture the swallowing motion using this ultra-high-speed imaging method, extremely short repetition time (TR) and echo time (TE) values are essential. However, to enhance the accuracy of signal intensity measurements, in the present study we used the same voltage pulse parameters to capture resting state images of the neck. The flip angles ranged between 10°and 100°at intervals of 10° (i.e. a total 10 different flip angles were used) . For images obtained with each flip angle, we assessed signal intensity and potential for visual evaluation of the tissues involved in swallowing (i.e. the soft palate, lingual muscles, epiglottis, thyroid cartilage, geniohyoid muscle, mandibular bone and hyoid bone) .
Results: The signal intensities of the tissues changed significantly depending on the flip angle. The greatest differences in the signal intensities of the various tissues, and thus the highest overall contrast, were observed at flip angles of 10°, then 20°and 30° (in that order) . Flip angles of 40-100°yielded the same signal intensities, which were lower than values for the other flip angles. Only flip angles of 20°, 30°and 40°maintained the overall signal to noise ratio (SNR) at a high level. Flip angles of 30°and 40°produced sharp images that permitted clear visual evaluation of the tissues involved in swallowing.
Conclusion: Based on the potential for visual evaluation of an image and differences in signal intensity between the tissues involved in swallowing, when obtaining images using ultra-high-speed MRI with SSFP sequences, a flip angle of 30°is optimal. This information may assist clinicians to clearly visualize anatomical structures during dynamic observations of swallowing function.

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The present study was focused on the tongue atrophy which is one of the common symptom in patients with amyotrophic lateral sclerosis (ALS) and investigated the effects of tongue atrophy on impairment of swallowing function by using videofluorographic assessment.
The subjects included 19 patients diagnosed ALS and 11 age-matched normal adults. Each subject was asked to swallow 3 ml water with 40 vt/wt% barium sulfate. Whether aspiration and/or penetration of bolus before, during and after swallowing was observed or not and amount of bolus residues in the pharynx were evaluated. Furthermore, in case of no aspiration observed, bolus transit times were measured and compared among the groups.
All the cases in which the patient had an episode of aspiration were related to the muscular atrophy of tongue. The patient group showing tongue atrophy exhibited higher scores of pharyngeal residue than the other groups, meaning that the amount of pharyngeal residues after the swallow in the former group was much more than that of patients with no atrophy of the tongue or normal adults.
Comparing the bolus transit time among the atrophic tongue in patients without aspiration, normal tongue in patients and normal adults, Clearance Time, i.e., the time of the bolus invading the pharynx and Upper Esophageal Segment Transit Time were delayed and the bolus head reached at the bottom of hypopharynx before onset of swallowing in the first group. It may be possible that abnormal structure and motility and/or extension of pharyngeal duct due to the atrophy of tongue may cause the difficulty in the bolus handling in the oral cavity and delay of triggering reflex swallowing.
All the results obtained in the present study suggested that the muscular atrophy of tongue in patients with ALS may be a critical sign for the risk of severe problem with swallowing function.

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