Occlusion is the basis of dentistry. It is necessary to have good occlusion to maintain a higher level of the QOL. But criteria of optimal occlusion have not been elucidated and we don't have a systematic diagnosing method of occlusion based on scientific evidences. In this symposium, four speakers gave their lectures on evaluating methods of occlusion or their opinions about the optimal occlusion with their thinking behind. In this paper I emphasized importance of objective evaluation of occlusion, and classified elements of occlusion into five as follows, l; maxillomandibular relation at the ICP (intercuspal position), 2; stability of occlusal contacts at the ICP, 3; position of occlusal contacts that guide mandibular movements, 4; directions of any excursion with occlusal contacts from ICP or to ICP and 5; position, curvature and smoothness of occlusal plane and dental arch. We have to select parameters that could represent each element of occlusion. Then we have to verify relation between various occlusal conditions and jaw function, whole body function and the QOL in basic and clinical researches. In order to carry them through, I think we have to establish a database on the stomatognathic functions and occlusion.

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In order to clarify the functional meaning of every part of the occlusal surface, the teeth displacements during clenching and mastication were microscopically measured, especially on the upper and lower first molars which had many possibilities to be restored in the dental treatments. Additionally, the main occluding area and the process of changing the shape of hard food during mastication were macroscopically observed.
Consequently, three elements to realize the form of the functional occlusal surface were led.
1. The occlusal contact to the stabilize intercuspal position
2. The main occluding area between the lingual cusp inner incline of upper molar and the buccal cusp inner incline of lower molar to crush hard food during mastication
3. The overlap of the non-functional cusp to form smoothly swallowable food bolus
To stabilize the intercuspal position by means of the first molar, the buccal cusp of lower molar should firstly interlock the fossa of the upper molar. Secondly, there must be at least one occlusal contact near the top of the cusp so that main force vector may direct to the longitudinal axis of the tooth. Furthermore, as the results of the analysis on occlusal contact patterns at the intercuspal position, it is suggested that above-mentioned occlusal contact is important for the first molars to become the main occluding area during crushing hard food.

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Quantitative analyses of the bite forces that act on the dental arches have revealed the actual scheme of normal dental occlusion, and have contributed to the establishment of the criteria for normal occlusion, including the bilaterally symmetrical distribution of occlusal loads, greater bite forces of posterior teeth than of the anterior teeth, axial loading of occlusal forces on each occluding tooth, and perpendicularly acting occlusal resultant to the occlusal planes. No major discrepancy was observed between the features of the actual scheme and previously proposed criteria for normal dental occlusion, however, more information on the actual features would be required to differentiate the criteria of normal occlusion from those of ideal occlusion and to standardize occlusal diagnosis and its criteria. In this paper, we present the actual scheme of normal dental occlusion, which was recently put forth based on the quantitative analyses of bite forces, and discuss on the potentiality of occlusal diagnosis.

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We proposed the criteria during intercuspation from the viscoelastic aspect in normal dentate subjects. Criteria for the normal Intercuspation were simultaneous contacts on both sides by even pressure between maxillary and mandibular posterior teeth. In the diagnosis whether to fill the criteria, T-Scan II was the only equipment which was able to do the time-series analysis of the occlusal contact in the intercuspal position.
It was suggested to improve the diagnostic usefulness of standardization and the reliability of the dependable measurement technique in the future.

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Occlusal contact and clearance in functional jaw movement can be visualized on the graphic terminal by using three-dimensional tooth surface data and six-degree-of-freedom jaw movement data. This system called as computer visualizing systems for dental occlusion. By this system, we can evaluate the occlusal contact and clearance in functional jaw movement. It will be able to use in dental clinic and the best way to evaluate the dental occlusion.

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The brain blood flow of chewing various flavors of gumi-jelly was analyzed in order to clarify the effect of taste of the food on brain blood flow during chewing. Ten healthy subjects (5 males, 5 females, ages 22 to 34, average age 24.8) were asked to chew three types of gumi-jelly with three different flavors (normal, sweet, bitter) on their habitual chewing side for 20 seconds and the bilateral brain blood flow were recorded using near-infrared spectroscopy (NIRO-300^®, Hamamatsu Photonics) . The measuring probe was placed so that the distance between the irradiation part and the receptive part was to be 4 cm, and was placed on the bilateral sides by pushing away the hair in an area related to cortical masticatory area and thus would mostly react to opening and closing movement. First the brain blood flow of prior to, during and after chewing gumi-jelly were investigated. Next the amount of change in blood flow were compared among the three types of gumi-jelly. The brain blood flow increased during chewing gumi-jelly, started to decrease after chewing and returned to its original state. The amount of change in brain blood flow was smallest when chewing bitter gumi-jelly, increased with chewing sweet gumi-jelly and was largest when chewing normal taste, and significant differences were found among the different flavors. From these results it was concluded that brain blood flow increased by masticatory movement and that the difference in flavor affected increase and decrease in the amount of brain blood flow.

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It is supposed that on the reproduction of lateral movements, the articulator settings of the Condylar type articulator is different from the condylar pathways of the human jaw. The Arcon type articulator shows the same values as the human jaw. It is not clear, however, about the differences of the articulator settings between the Arcon and the Condylar type articulator. In the present study, the angular differences on each adjustable mechanism are analyzed by reproducing the same lateral movement on the Arcon type articulator; which has all guiding systems on the upper member, and the Condylar type articulator; which has all guiding systems on the lower member. The lateral movement is reproduced on the Arcon type using the mandibular movement cubic model three-dimensionally. The lateral movement of the Condylar type is reproduced by calculating the intercuspal position of the Arcon type relative to the lateral occulusal position of the Arcon type. The differences of the articulator settings between both articulators are calculated and compared.
The results are as follows;
The angular differences of the articulator settings between the Condylar and the Arcon type articulator are not the same on each adjustable mechanism. The maximal difference of the non-working side condylar guidance is about 4°on the horizontal projective angle and 1°on the sagittal projective angle, while the maximal difference of the working side condylar guidance is about 2°on the horizontal and frontal projective angle. In addition, the changing of the sagittal projective angle on the non-working side condylar guidance affects the articulator settings of the Condylar type articulator. It is necessary to consider the angular differences from the condylar pathways of the human jaw, when evaluating the lateral movement by the Condylar type articulator.

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The purpose of this study was to characterize mandibular movement during protrusion in anterior crossbite children with primary dentition. Mandibular movements were measured using a TRI-MET^®, an optoelectronic analysis system with six degrees-of-freedom, at a sampling frequency of 100 Hz. This measurement data was transferred to a graphics workstation for analysis. The subjects with primary dentition were categorized into two groups according to their interocclusal relations, group one had normal occlusion and group two had anterior crossbite. The former group consisted of 20 children (mean age: 5 years and 6 months), and the latter group consisted of 15 children (mean age: 4 years and 9 months) . Anterior-posterior range, right-left range, superior-inferior range and three-dimensional linear distance of the incisal point and the condylar points during protrusion were estimated by using multilevel statistical models. Correlation coefficients between incisor and condylar distances were evaluated at both the inter-individual and intra-individual levels. The study's results were:
1) Protrusion of the anterior crossbite group was characterized by smaller ranges and distances of both the incisors and condyles than children with normal occlusion. This suggests that when the teeth are at maximum intercuspal position the condyle is located more anteriorly in anterior crossbite children than in normal children.
2) High correlation coefficients in both groups of children, suggest that condylar movements during protrusion can be reliably estimated from incisor movements.
3) Intra-individual correlations of normal occlusion children were larger than their inter-individual correlations, but the reverse was true for anterior crossbite children.

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