This study assessed how the location of the tapping point is affected by changing the head position. An intra-oral tracing device consisted of a metal tracing plate and a central bearing pin was used in five fully dentate subjects. The tracing plate was fixed to the maxillary part of the device parallel to the occlusal plane. The central bearing pin was fixed to the mandibular part of the device and was located at the midpoint of a line connecting the bilateral first molars. The pin was placed perpendicular to the tracing plate. The appliance was inserted in the mouth and the subject was asked to perform tapping movements with the head Camper and Frankfort plane placed horizontally. The tapping movements (n=30) were made at a 30 mm-range of motion, and the incisal and condylar points were tracked with a 6-degree-of-freedom jaw movement tracking system (TRIMET; Tokyo Shizaisha Co., Japan) .
The antero-posterior distribution of 30 tapping points and their mean position from intercuspal position were analyzed in incisor and condylar points between two head positions. Result revealed that the condylar points corresponding to the tapping points converged into a small area when the head was positioned with the Camper plane horizontal. However, in both head positions, condylar points were located anteriorly from the intercuspal position. From the results, it can be concluded that head position has it's effects on the distribution and mean position of tapping points. In addition, it can be suggested that from the distribution of scattered tapping points, the head should be positioned with the Camper plane horizontal to record the tapping points at a convergent area.

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The purpose of this study was to examine whether palatography can be used for the diagnosis in dysphagic patients who experience difficulty of bolus formation and bolus transport into the pharynx. Four dysphagic patients with difficulty at the preparatory and oral stage of deglutition were selected, another five dentulous students with normal feeding, swallowing and stomatognathic function were chosen as subjects. Using palatal plate (black vinyl chloride seat) in powdery method, palatograms of the syllables and saliva swallowing were recorded. The syllables [ta], [na], [ra] and [ki] were selected which have been used for dysphagic patients to train the articulation. Palatograms to pronounce the syllables [ta] and [na] were used to examine the ability of bolus formation by the anterior part and the lateral margin of the tongue; the syllable [ra] was used to examine the ability of bolus formation by the apex of the tongue; and the syllable [ki] was used to examine the ability to transport the bolus into the pharynx by the elevation of the posterior part of the tongue. Palatogram of swallowing was used to examine the ability to transport the bolus into the pharynx by the elevation of the dorsum of the tongue. The results were as follows;
1. In subjects from whom the disorders of bolus formation was admitted, abnormalities were not found in palatogram to pronounce the syllables [ta] and [na] . Therefore, in this study, it was indicated that the disorders of the bolus formation might not be caused by the anterior part and lateral margin of the tongue.
2. In subjects from whom the disorders of bolus formation was admitted, abnormalities were found in palatogram to pronounce the syllable [ra] . Therefore, it was indicated that the apex of the tongue was responsible for the disorders of bolus formation.
3. In subjects from whom choke was admitted, abnormalities were found in palatogram to pronounce the syllable [ki] and saliva swallowing. Therefore, it was indicated that the decreased ability to elevate the tongue was responsible for the choke.
From these results, the possibility to diagnose the disorders of bolus formation and the difficulty to transport the bolus into the pharynx of dysphagic patients by palatogram was indicated through these subjects.

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It is well known that the range of motion during mouth opening changes with the food size.
We have previously reported the relation of head movement to the mandibular movement; the head moves in the extended direction during mouth opening. In this study, we analyzed the head movement simultaneously with the mouth opening during food intake.
One male and two female adults (age range: 24-26yrs.) without any craniomandibular dysfunction were selected as subjects. The test food consisted of an apple cut into the different square size (6 to 35mm) . Then, we recorded the head and mandibular movements at two head positions (horizontal to the Frankfort and Camper plane) with the 6-degree-of-freedom measuring device without any restrictions of the subjects' head.
The results were as follows:
1) The food space was observed during food intake. The size of this space at the same food size was kept constant even when the head position was changed.
2) The head movement was larger when the head position was horizontal to the Frankfort plane than to the Camper plane. This suggests that the head movement exists in order to acquire support for the mandible during mouth opening.

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The present study reports a newly developed laryngeal movement tracking system. The system consists of a metal rod, a displacement sensor, a plastic plate, and two identical magnets. The plastic plate was fixed to the skin over laryngeal prominence. The rod and magnets conduct the movement of the plate in relation to laryngeal movement to the sensor during swallowing. To evaluate the performance of the system, sensor outputs during swallowing were compared with recordings of masseter and digastric muscle EMGs in 6 young and healthy adults. Tests were conducted both in head-fixed (n = 3) and head-free (n = 3) conditions. Each subject was given a test fluid (2.0 ml of tea, at a temperature of 25°C) into the oral cavity and was instructed to swallow it. Actual motion picture of the laryngeal movement during swallowing was also recorded in the sagittal plane using a video tape recorder in one subject. The swallowing event in the laryngeal movement could be recorded as a biphasic curve by the system both in head-fixed and head-free conditions. Temporal analysis of the recorded curve together with the EMGs and the motion picture revealed that; the recorded curve reflects natural movement of the larynx during swallowing; and the inflections on the curve corresponded to laryngeal upward and downward movements respectively. The present results suggest that the developed system may be applicable to obtain temporal aspects of swallowing easily and safely in the clinic and laboratory.

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In this study, daily reproducibility of ranges of border jaw movements in healthy dentulous subjects was examined in the short term. We also examined the reproducibility of positions of reference points that determine the standard of coordinates used for a jaw movement-analyzing device and that are thought to be one of factors that influence the daily reproducibility of jaw movements.
‹Methods› The subjects were 5 healthy dentulous people aged 26 to 31 years. Tracings of border jaw movements in sagittal and frontal planes were recorded five times a day using a Gnatho-hexagraph JM-1000 (Ono Sokki Co.) . The recording was repeated for five successive days. The back and forth width of border jaw movements in the sagittal plane (B-F width) and the right and left width in the frontal plane (R-L width) were measured and examined. The reference points for coordinates of Gnatho-hexagraph were the right orbitale and bilateral porions, and the analyzed point was the lower incisal point. To fix these points, dimples made of self-cured resin were set using a Pro-arch face bow.
‹Results› 1. Standard deviations (SD) of coordinates of the incisal points among the five days were 0.48-1.49 mm, and SD of the distances between the right orbitale and the bilateral porions were 0.31 1.55 mm for the five subjects, while SD of coordinates of the reference points and the incisal point on each day for one subject were 0.23-0.38 mm, and those of the incisal point of the subject's cast on an articulator were 0.19-0.42 mm. Therefore, it was thought that the variance among days was mainly due to the gap of each reference point at re-wearing each day.
2. As for variance of R-L width and B-F width within each day, there was a significant difference in R-L widths in one subject within each day. As for variance among the five days, on the other hand, there were significant differences in the B-F widths of one subject and in the R-L widths of four subjects. SD of R-L and B-F widths among the five days ranged from 0.12 to 0.62, tending to be larger than those within each day. However, SD of R-L and B-F widths among the five days were smaller than SD concerning reference points among the five days.
In concluding, it was suggested that R-L and B-F widths in some healthy dentulous subjects could change in the short term, while it became clear that the change is relatively small.

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