The purpose of this study was to investigate the effects of mechanical load on blood flow in the palatal mucosa. In five healthy dentate subjects (mean age 26.4 yrs), the blood flow in palatal mucosa was measured using the laser Doppler flowmeter. A 400 gf load was applied through a 4mm-diameter probe in the posterio-lateral aspect and the central rugae area of the palate for 40 s. The blood flowmetry in the posterio-lateral site of the palate was also performed for loading intervals of 10, 20 and 30 s, and for the load intensity of 100, 200 and 400 gf, respectively. The results obtained were as follows:
1. The effect of load on blood flow varied with the site of force application in the palate. A reactive hyperemia was almost always observed after the removal of load in the posterio-lateral region. However, no reaction or unclear reactive hyperemia was noted at the anterior site.
2. There was a tendency that an increase in the loading interval extended the recovery period to the baseline. The reduction in blood flow during the load and its increase after the load removal tended to be constant regardless of the loading interval.
3. An increase in load intensity resulted in the reduction of blood flow during loading and the extension of recovery period. On the other hand, the degree of increase in blood flow after the load removal was not affected by the change of load intensity.
4. The relationships between the loading interval and the recovery period, between the load intensity and the recovery period, and between the load intensity and the reduction in blood flow during the load were considered to be useful parameters for evaluating the characteristics of the palatal mucosa.

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The aim of this study was to analyze the mandibular movement paths in subjects with normal occlusion. Fourteen adults who were free of signs and symptoms of TMJ disorders were selected. The movements of the incisal point and condylar point during maximum jaw opening-closing phase were recorded and analyzed with the Gnathohexagraph, JM-1000, a comprehensive analyzing system for stomatognathic function. The movement paths of the incisor and condyles were analyzed for: (1) Maximum displacement, (2) maximum velocity, (3) the amount and rate of displacement reached to the maximum velocity, (4) pattern of velocity curve. Maximum displacements of incisor and condylar paths were 50.2mm and 15.5mm, respectively. Maximum velocities of incisor movements during opening and closing phases were 289.6mm/s and 330.6mm/s and those of condylar movement were 90.8mm/s and 160.6mm/s, respectively. The amount and rate of displacement reached to the maximum velocities of incisor movement during the two phases were 16.1mm (32.1%) and 25.5mm (52%) . Those of condylar movement were 9.5mm (59%) and 8.1mm (52%), respectively. Three patterns of velocity curves were found in both incisor paths and condylar paths. The results of this study indicated that the analyzing parameters for incisor movement path and condylar movement path of this study might be useful for mandibular kinetics.

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The type of tooth movement is described simply by the center of rotation. Therefore, orthodontic tooth movements can be predicted, when each location of the center of rotation under various force systems is clarified. The purpose of this study was to develop a magnetic sensing system for three dimensional displacement and to determine the location of center of rotation of the maxillary central incisor. Lingually directed forces were applied at different horizontal levels in human subjects. The main part of the system is composed of eight hall elements and a samarium cobalt magnet. The relationship between the location of center of rotation and theposition of the force application was discussed. It was concluded as follows;
1. Rresolution was determined to be less than 1μm and distortion of the system was calculated at less than 0.7% within the range of ±300μm. This system was estimated to be stable and sensitive enough to be applied in the oral cavity and to measure the tooth movements in vivo.
2. When a lingually directed force was applied at the bracket position of the tooth, the center of rotation was observed at a point 0.44 times the root length from the alveolar crest. This indicated that the tooth crown tended to move lingually and the root tended to move labially, or oppositely when only a single force was applied to maxillary incisors during the anterior teeth retraction.
3. When the point of force application was moved cervically, the center of rotation also moved toward the same direction. It was shown that the center of rotation is located at the root apex when the force was applied at a point 5mm cervical from the bracket position.
4. As the location of force application moved further apically, the direction of rotation changed from crown-lingual to root-lingual at a point between 6 and 8 mm cervical from the bracket position.
This study was supported by DFG Grant Mi198/4-1.

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We have established a system for calculating bite force from integrated electromyograms to evaluate the function of complete denture wearers. However, this system has only measured the value of bite force and could not refer to its direction. Accordingly, we capitalized on the three-dimensional bite force measuring device to assess the direction of bite force.
The purpose of this study was to confirm the accuracy of the device under the load examination.
Results obtained were as follows:
1. The device was in error by less than 2% when it was instituted calibration constant of each load cell, range of 1-50kgf.
2. The maximum variance of mean output value on each load cell by horizontal rotation was 2%. Therefore, it was confirmed that horizontal rotation did not influence the accuracy of the measuring device.
3. The accuracy of the device by inclination was examined. The mean output value of each load cell showed a linear range of 1-50kgf, and the device was in error by above than 24%, toward 5 degrees inclination. So, if the device is to be set up in an experimental denture, it is necessary to install it as parallel as possible on to the horizontal plane.
These results suggested that the measuring device is very precise for measuring the value and direction of bite force.

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The influence of growth and development on occlusion is important for establishment of stomatognathic function. There are, however, few studies on the changes induced by growth and development in occlusion. We have already developed the add-picture system for evaluation of occlusal contact area and location. This paper reports a cross sectional study and describes changes in occlusal contact and a stability of occlusion with growth and development using the add-picture system.
We selected 25 healthy infants and classified them into 4 group according to the stage of development of occlusion: children who attained deciduous occlusion, children who attained first molar eruption, children who lateral segment teeth changing and children who attained second molar eruption. We recorded a silicone occlusal registration at intercuspal position and input it to the add-picture system to analyze occlusal contact areas and locations. We analyzed the ratio in occlusal contact area between both sides as an asymmetry index of occlusal area (AIOA), and occlusal contact location in dentition as a stability index of occlusion (SI) .
Occlusal contact area and its location in the dentition changed corresponding to the developmental stages noticeable to the naked eye. AIOA was stable for developmental stages. SI in the attained deciduous occlusion, the attained first molar eruption and the attained second molar eruption groups showed low values and took on a stable aspect. However, SI was significantly unstable in the lateral segment teeth changing groups.
In conclusion, occlusal balances in the intercuspal position were stable for stages in growth and development without the stage in lateral segment teeth changing.

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We have previously demonstrated that the head moves rhythmically and coordinately with the mandible during functional mandibular movements; however, in those studies we could not provide information on the movement of the head as a whole because only the mandibular and maxillar incisal points were tracked. The objective of the present study was to assess sagittal head movement through analysis of the vectors of several reference points in the head and a mandibular incisal point during open-close tapping movements of different frequency.
The same 6-degree-of-freedom measuring device employed in our previous studies was used again to analyze data from four male adults, age 26-27 years old.
Results:
1) During mandibular tapping movement, head reference points moved in a rotation-like movement; i.e., during opening the head moved clockwise and counter-clockwise during closing in the left side's sagittal plane.
2) There were no significant differences of angulation of the vectors between 1 Hz tapping movement and 3 Hz in all reference points. However, the range of motion of all reference points depended on the frequency of tapping movements in this case. The motion of the 1Hz tapping movement was larger than the 3 Hz one.
3) The hypothetical rotation center was located above the cervical vertebrae, and its sagittal position was dependent on each tapping movement.

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It is important to establish a quantitative evaluation method of the occlusal surface shape in order to make an objective diagnosis and treatment of the dental occlusion. As the most important part in the occlusal surface shape is the occlusal facet, we developed a new method and parameters to evaluate occlusal facets quantitatively. We studied the effectiveness of this new evaluation method in this research.
Material and method: Three dental plaster models from 3 volunteers that had normal occlusion were measured with the CNC 3 dimensional measuring system (Microcord FN503, Mitutoyo, Japan) . Those data were linked with mandibular sliding movement data that were measured with a 6 degree of freedom jaw tracking device. Then an occlusal reference surface was defined by using those combined data for each occlusal facet. Finally, values of facet evaluating parameters were calculated for each occlusal reference surface.
Parameters: Inclination angle of the occlusal facet and x axis value of a direction cosine calculated from a normal vector of an occlusal facet were used for evaluating occlusal facets quantitatively. This x axis value of the direction cosine was named AP value (antero-posterior value) . Occlusal facets were classified into 4 groups with its normal vector for evaluating occlusal facets qualitatively.
Results and discussion were as follows:
1. AP value can represent the degree of resistance for mandibular position changes for anterior-posterior directions during biting. Inclination angle and AP value of occlusal facet enabled us to evaluate the occlusal facet not only numerically but also functionally.
2. The occlusal facet could be classified into 4 group by using 3D measuring and numerical process. They were called the M type (mesial facing type) and the D type (distal facing type) on the working side and the non-working side according to its functional characteristics.
3. The inclination angle and AP value that were calculated from the occlusal reference surface changed regularly according to that surface position in the tooth arch. These changes reflected jaw movement of each subject.
These results suggested that those parameters and new analyzing method could be applied for evaluating the occlusal surface quantitatively.

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This study tested the accuracy of a series of modifications made to an available jaw tracking system (TM Jawgraph) . Namely, pyramidal-shaped sets of markers were designed to allow 3-D measurements by a geometrical method; each of these sets carried four infrared-light-reflecting passive markers whose diameter is 3 mm. The total weight of each set including the connection rods is merely 2g. These sets of markers were expected to provide not only 6-degree-of-freedom recordings of the mandible, but also of coordinated head movements and of objects confined within a small predetermined area. A computer software was also made to analyze the markers' 3-D movement. The CCD cameras in this system require a 200×200×200mm field.
Verification of the accuracy of this system for measuring jaw movements was made with translation tests using pulse stages. The error of measurement among trials was calculated for several positions. The average error in the horizontal axis, between the frontal and the posterior planes was 0.3mm, and 0.2mm for the vertical and horizontal axes between the right and left sides of the measuring field. From this results we concluded that this system allows a precise estimation of 3-D jaw movement with the lightest device attached to the teeth that is available today.

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