Digital type jaw movement analyzer MM-JI is a jaw-tracking device that measures jaw movement in six-degree-of-freedom. Jaw movement data measured with this device potentially contain many diagnostic information of stomatognathic function. The current status and issues of jaw movement analysis were presented herein. Visual evaluation of jaw movement pathways and multi-variable analysis of numerical jaw movement parameters are fundamental techniques of these analyses. Combination of these techniques is essential to elicit diagnostic information from jaw movement data. Clinical application for diagnosing temporomandibular disorders and dental prosthesis were also discussed. When the development of jaw movement database and the further study of occlusion and jaw function proceed, six-degree-of-freedom jaw movement analysis will be come widely used.

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From a clinical viewpoint, it is important to clarify the stomatognathic functions. In order to diagnose stomatognathic dysfunctions, it is necessary to record and examine stomatognathic functional phenomena simultaneously such as mandibular movement, muscular activities, TMJ sounds, and occlusal sounds.
A Gnatho-hexagraph is capable of recording simultaneously the various phenomena related to stomatognathic functions in the following manners.
1. It can record many phenomena simultaneously such as EMG, TMJ sounds, and occlusal contact sounds related to mandibular movement.
2. The mandibular movement is recorded in six-degree-of-freedom with an accuracy of ±150 μm.
3. The reference points can be indicated by employing a handy optical pointer.
4. By applying a lightweight facebow (weight: 12 g), the patients can demonstrate mandibular movements more physiologically without feeling any stress.
5. In this system, the operation is easy and does not require much space.
The outline, advantages, and disadvantages of the Gnatho-hexagraph are presented herein, and clinical application of the system to stomatognathic functional examination are discussed using some results obtained from patients.

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A six-degree-of-freedom jaw tracking digital device, TRIMET was developed. In total, eight small LEDs are set on upper and lower facebows which are attached to the buccal surfaces of the dental arches. The weight of a complete facebow for the upper and lower jaws is just 40 g. The motion of the LEDs is registered with six high-resolution linear CCD cameras set around the subject's head. The TRIMET is a no-contact measuring device that allows precise six-degree-of-freedom jaw tracking without fixation of head or jaws or causing intercuspal obstructions that could alter oral function. Using these outstanding features it was attempted to determine whether there is coordination between head and mandibular movements in normal subjects and in TMD patients. It was found that, during jaw tapping movements, the head and the lower jaw have a functional synergy characterized by opposite trajectories of the upper and lower incisor point traces ; the incidence of such coordination was lower in TMD patients. A rotation-like head movement was also found in the sagittal plane during tapping whose center was located above the cervical vertebrae region.

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Pediatric dentistry comprehensively covers the oral health care through the active period of growth and development in human life cycle. Not only the normal physical growth in the orofacial region, but also the developmental process of stomatognathic function in this period are necessary to clarify it, because the functional development of children is always progressing and leads to the maturation of masticatory function in adulthood. Jaw motion should give a lot of important information about oral function because it is performed by the functional integration of teeth, maxillary and mandibular bones, masticatory muscle, nervous system, and other organs. The application of six-degree-of-freedom jaw movement tracking devices must be the most suitable method to evaluate jaw motion, and to detect in detail the dynamic characteristics of the whole mandibular function. In this study, the application of a few measurement systems to children was discussed including two sets of our systems, and some results on jaw motion analyses of children were presented, 1) Characteristics of mandibular excursion of children, 2) Relationship between occlusal facets and lateral excursions of primary molars, 3) Six year longitudinal changes of jaw tracks of one child, 4) Characteristics of condylar motion during opening-closing movement, 5) Focusing characteristics of the condylar tracks, 6) Design of the curved mesh diagram of mandibular excursion, etc. Jaw motion of children had many different characteristics in comparison with adults.

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Since mandibular movements have six-degree-of-freedom, they must be measured by using the six-degree-of-freedom jaw movement tracking device. In consideration of measurement accuracy, operational ease, and so on, two devices were proposed, a monitor for the clinic and an accurate measurement for investigation. The condylar reference points were also said to be located morphologically and used easily in diagnosis.

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There is an intimated relation between the condition of periodontal ligament tissue and the success of tooth transplantation and replantation. In this study, the biological activity of periodontal ligament tissue after tooth extraction and storage was investigated to establish a long-term storage method for periodontal ligament tissue.
Rat incisors were used as the study teeth. UW solution, Euro-Collins solution, DMEM, and sterile physiological saline were used as storage solution. The storage condition were refrigeration (4°C), controlled-freezing point storage (CFP storage;-2°C), and frozen (-80°C), and the storage period was 1-28 days. At the end of the storage period, cell cultures and double fluorescent staining were performed.
The results of the cell cultures showed better growth of the periodontal ligament cells in the CFP-storage group than in the refrigeration-storage group or the frozen-storage group, and the results for the 4 different types of storage solution showed the best growth in the UW solution storage group, with a maximum storage period of 21 days. Similarly, double fluorescence staining showed the greatest viable cell fluorescence level in the CFP-storage and UW solution group.
The above findings suggested that CFP storage in UW solution is useful for long-term storage of periodontal ligament tissue.

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Although there have been reports on the abrasion of resin cements, cement film thickness was hardly considered.
Takamisawa evaluated the influence of the cement film thickness on the abrasion of non-filler type resin cement, and concluded that there was a close relationship between number of times and depth of abrasion. The rate of increase of the wear depth was affected by the cement film thickness.
Since most resin cements contained microfiller, Variolink (Vivadent) was examined and it was IPSEmpress (Vivadent) cem kit.
Newly-designed appliances to prescribe 3 cement film thicknesses were used, namely 50, 100, and 200 μm, and the abrasion for each thickness in toothbrush abrasion test was observed.
Continuous measurements were made of the sectional profile, wear depth, and surface roughness by scanning laser microscope.
In SEM observation, the abrasion surface showed different aspects between non-filler and microfiller types.
While there was a close relationship between number of times and depth of abrasion as in the case of non-filler type, the amount of increase of the wear depth varied with the cement film thickness.
Test results indicated that the cement film thickness had influence on the abrasion of resin cement, and resistance of abrasion was influenced by filler type and resin matrix.

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The purpose of this study was to survey the oral conditions of the severely disabled patients in Tokyo Metropolitan Higashiyamato Medical Center for the Severely Disabled.
Their teeth, occlusal conditions, and kinds of prosthodontic treatment were recorded and analyzed for 90 inpatients who underwent treatment at the dental clinic of this center.
The results were as follows:
1. The DMFT-index of the patients was 14.91 and its national average was 15.15, which showed little difference. However, the numbers of untreated teeth and missing teeth of a patient were larger than those of the national average.
2. Bruxism was recognized in 21.1% of the patients.
3. Maxillary protrusion was recognized in 32.2% of the patients.
4. Removable prostheses were not applicable to the patients. Fixed prostheses were effective because of preventing of accidental swallowing.
5. More than 90% of the patients did not have chief complaints, but their family and physician did. It is desirable and important to consult with their family and physician about dental treatment of patients.

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The change in perioral soft tissues especially in the lips caused by clenching were investigated to elucidate the effect of experimentally induced muscle fatigue on the articulatory movement for 5 vowels.
The quantity of movement during vocalizing a vowel immediately after clenching was not increased at any measuring point compared with that just before clenching and the clenching effects were classified into three patterns based on the quantitative changes in the movements 10 minutes after clenching.

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The purposes of this study were to verify unidimensionality of the questionnaire comprising 58 food items designed to evaluate the masticatory ability of complete denture wearers, and to reconstruct it to be shorter but accurate using the item response theory (IRT). The 230 subjects were edentulous and complete denture wearers.
The results were as follows:
1. Forty-one items showed unidimensionality based on principal factor analysis of the tetrachoric correlation matrix, except 17 items whose proportions of correct answers were above 0.90.
2. A one-parameter logistic model was applied to 26 items, whose principal factor solutions were above 0.69, and fitted the model based on chi-square statistics. The parameters were standardized according to ability.
3. The scale, which comprises 10 items and serves as an approximate interval scale, was reconstructed.
4. The KR-20 coefficient of the scale was 0.83.
5. The scores showed significant differences between the three groups which were classified by subjective assessments of their own masticatory abilities (p<0.01): male scores were higher than those of females (p<0.05), were unrelated to age (r=-0.15, p<0.05), and increased when new dentures were made (p<0.01).
6. It appeared that the scale has high reliability and validity as a clinical test.

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The morphological changes in periodontal tissues around root caps, anchor teeth, and dentures were examined in 24 denture wearer with root caps (mean age: 63.4 years) to study the influence of root caps on tooth preservation and protection of the residual ridge and denture conditions. Sixty-two root caps were morphologically classified into five types. The root caps of long square type were frequently worn on premolar teeth, while those of short dome type were worn on the incisor and canine teeth. The mobility of tooth was significantly largest in the group with the short dome type and in the subjects wearing denture for 4-10 years, while it was lowest in those wearing denture for 10 years. The periotron value, which reflects periodontal inflammation, was significantly smallest in the group with the long square type. These results suggested that the shape of root caps might relate to the prognosis. The major mastication is more likely to be done on the same side as in the root cap in full overdenture wearer with root caps.

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Piezography used mainly within France and Spain is one of the functional approaches to obtain the proper denture space in complete and partial dentures. The purpose of this study was to find impression materials suitable for Piezography. Five subjects and five operators (mean age: 27.0±1.5 years) were selected for the study. Eleven kinds of commercially available soft impression materials were examined by using Visual Analog Scale (VAS) on six items, irritation to oral soft tissues, operability, aptness to pronounce and to hear words, hardening time, and surface smoothness.
As a result, FITT (Kerr Co.) used in the original Piezography was the best impression material. Tissue Conditioner (Shofu Inc.) and Evatouch H-type (Neo Dental Chemical Products Co.) also obtained high evaluation among impression materials tested in this study. In consideration of economic efficiency, it was suggested that Tissue Conditioner was the best impression material for Piezography in Japan.

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The layering technique which forms layered ceramics on heat-pressed dentin ingot is utilized to produce esthetic colors for all ceramic crowns. While the color of ceramic crowns has been determined based on the experience of individual dental technicians, an objective method was developed for the colordetermination using computer color matching (CCM). The purpose of the present study was to utilize a CCM system based on the CIBA-Q method for an all ceramic crown, IPS-Empress®, and evaluate the color reproducibility. Five characteristic colors for IPS-Empress® were set, and the ceramic samples composed of layering ceramic on dentin ingot were made according to the formulations prescribed by the CCM program. The colors of the ceramic samples were compared with the respective target ones. The results were as follows:
1. Reflectance curves of CCM samples were very similar to that of the target ones.
2. dL*was higher than dC*. Both coordinates tended to be small in case of low translucency target.
3. dE between targets and CCM samples were under 2. In conclusion, the CCM system will be a great tool to reproduce esthetic colors for layered ceramics.

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The object of this study was to analyze mathematically the effect of lateral condylar path of nonworking side on tooth paths.
The conclusions of calculation were
1. The error that gives the lateral condylar path of the nonworking side is directly proportional to the error that appears in tooth paths. The error of tooth path was about 90% of the error's value which produces the lateral condylar path of the nonworking side.
2. The relation between the lateral condylar path of the nonworking side and tooth paths is not influenced by the direction of nonworking condylar movement or the angle of the sagittal incisal path. However, it is influenced by the direction of working condylar movement.
3. Angle of the lateral condylar path has more influences on the angle of tooth paths than that of the sagittal condylar path as for the condylar path of the nonworking side.

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The purpose of this study was to clarify the long-term endurance of crown retention cemented with resin-modified glass-ionomer cements (RMGI) by thermal cycling simulating the oral environment.
In this study, two kinds of cement, Fuji lute (FL) and Vitremer luting cement (VL), were selected, and Super bond C & B (SB), a resin system cement, and Fuji I (F I), a traditional GI cement, were also tested as controls.
All specimens were cemented to metal abutments with each cement, and put through the thermal cycling (4°C-60°C-37°C) test 0 times, 5, 000 times, 10, 000 times, and 15, 000 times, respectively.
The result was as follows:
1. The retention force of crowns cemented with FL showed little variation due to thermal cycling.
2. The retention force of crowns cemented with VL increased due to thermal cycling.
3. After 15, 000 times of thermal cycling, the values of FL and VL were similar to the value of SB, and these were about two times that of F I.

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To understand the relationship between disc displacement status and condylar movement, the mandibular movement together with articular disc position of 80 outpatients with temporomandibular disorders were examined. Articular disc position was detected with a 1.5 T MR scanner. Mandibular movement was analyzed with a six-degree-of-freedom jaw tracking device.
Evaluation of nonworking condylar movement during lateral excursion jaw movement made it possible to reduce the effect of contralateral condylar movement.
The results were as follows:
1. Out of 160 mandibular joints, 80 joints were found to be disc displaced. Thirty-nine cases involved reduction and 41 nonreduction.
2. No joint having disc displacement with reduction was classified as grade 3, implying the most prominent displacement in terms of condylar head and disc positional relationship.
3. It showed a high correlation between the range of condylar movement and that of incisal movement regardless of the disc situation.
4. Range of lateral movement at the nonworking condylar point was influenced by the degree of displacement rather than by the instance or lack of reduction.

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During clenching at the intercuspal position, the direction and the amount of teeth displacement are different even between occluding upper and lower teeth of one subject. Therefore, there is a possibility of change in the occlusal contact relation depending on the clenching force. In this investigation, teeth displacements were measured with the Displacement Transducer type M-3 and interoccluion at the intercuspal position was recorded.
The conclusions were as follows:
1. Using black silicone, agar and silicone impression materials, real occlusal contacts can be recorded in addition to close occlusal areas.
2. The clenching force is related to the amount rather than the direction of teeth displacements.
3. The more different the direction and the amount of displacements between upper and lower teeth are, the greater the change of the occlusal contact relation becomes.
4. The occlusal contact relation is changed depending on the clenching force, which is the buccal parts of the occlusal surface becomes closer, and real occlusal contacts increase.
5. Since the number of actual contact is few in dental arches in light clenching at the intercuspal position, the mandibular position is unstable. Thus the mandibular position in heavy clenching with more contacts should be a reference.

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The theoretical equation concerning the direction of tooth guidance, which was statistically based on the direction of balancing condylar path, was applied to three subjects and their stomatognathic functions were discussed. The stomatognathic functions were evaluated by clinical symptoms, mandibular movements, and muscle activities as parameters.
The conclusions were as follows:
1. Depending on the direction of tooth guidance calculated from the theoretical equation, that of subjects should be gentler or steeper.
2. In reconstructing the direction of tooth guidance:
1) Some clinical symptoms were alleviated.
2) The mandible was smoothly moved, not even affecting the condylar path.
3) The leftand right masseter muscles, anterior temporal muscles, and posterior temporal muscles showed nearly normal activities.
3. The meaning of theoretical equationin stomatognathic function became obvious.

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The discoloration of the fixed metal prosthodontic appliances, which had been removed from the oral cavity, was observed to obtain epidemiological and clinical suggestions to select the dental alloy. This study was performed on 396 fixed metal prosthodontic appliances which were removed from the oral cavity.
The findings were as follows:
1. The appliances were composed of 7 kinds of dental alloy, Au-Pd-Ag-Cu-alloy (74.4%), Ag-alloy (9.8%), Ni-Cr-alloy (9.5%), Au-alloy (4.5%), Amalgam (0.5%), Co-Cr-alloy (0.3%), Titanium alloy (0.3%), and others (0.7%). The appliances observed were full cast crowns (33.1%), bridges (21.0%), fillings or partial veneer crowns (16.7%), resin faced cast crowns (13.1%), connected crowns (6.3%), root caps (2.5%), band crowns (2.3%), porcelain-fused-to-metal-crowns (1.8%), metal cores (1.8%), and attachments (1.5%).
2. The proportionof the discoloration of appliances removed was 69%, and this was about 1.7 timeshigher than before removal (p > 0.01).
3. The discoloration of appliances increased with the duration of use in the oral cavity (p > 0.01), and theappliances of Ag alloy were the most discolored (88.9%, p> 0.05) among 7 kinds of alloy.
4. Discoloration was frequently observed at the soldered portions, inner margin, and basal surfaces of pontic or the lower parts of connectionat the proximal embrasure (p > 0.05).
5. The proximal surfaces adjoiningdiscolored appliances were more discolored than those adjoining nondiscolored appliances (p > 0.01).
6. In patients whose oral prophylaxis status were better, the appliances tended to be less discolored.

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Temporary soft lining materials (TSLM) can not be used for a long time. However, removing this material from denture base with burs causes an unhygienic environment and requires much labor. Therefore, it is necessary to prime the separator for improving separability (ease of separate) between TSLM and denture base.
The purpose of this paper was to examine the effect of the passage of time after attaching TSLM, SOFT-LINER, COE-SOFT, and Visco-gel to the denture base ACRON, ACRON MC, and Palapress on separability. To simulate the chewing cycles, a loading apparatus, which enables loading repeatedly adequate masticatory force, was designed. The separability was evaluated from tensile strength and the ratio between interface failure and cohesive failure after testing.
Furthermore, Visco-gel was tested after warming specimen's attached TSLM (70°C, 5 min) or cooling (5°C, 1 min).
The conclusions were as follows:
1. The tensile strengths of all specimens without separator were gradually increased by the passage of time. However, there were no significant difference of tensile strength with separator for days 1, 3, and 7.
2. Although most of the separating surfaces of specimens without a separator showed cohesive failure, specimens with a separatorrevealed interface failure, and specimens with Vaseline showed mixed failure.
3. The tensile strengths of the TSLM to ACRON, and ACRON MC was greater than that for Palapress.
4. In case of Visco-gel, greater separability was obtained when specimens were warmed or cooled before testing.

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Recently, adhesive dentistry has made a lot of progress, and now its effects should be shared by post and core techniques for restoration of endodontically treated teeth. The purpose of this study was to compare the prefabricated metal postand composite resin cores with the conventional cast post and cores with respectto retention. Three kinds of luting cement for the cast post and cores, that is, zinc phosphate cement (EC), Panavia 21 (P 21), and Super-bond C&B (SB) were examined. In addition, three kinds of core build-up technique for the prefabricated post and composite resin cores were prepared for dislodgment tests. They were the prefabricated post cemented with P 21 and light polymerized Clearfil photo core (P 21+PC), the same post and dual polymerized Clearfil DC core (P 21+DC), and the prefabricated post cemented with DC and DC core (DC + DC).
The results were as follows:
1. The dislodgment forces of the cast post and cores cemented with EC were the smallest, although the forces did not decrease after thermocycling.
2. Three kinds of the prefabricated post and composite resin core were equal in retention to the cast metal post and cores cemented with resin cements, P 21 and SB.
3. The cast post and cores cemented with SB, and two types of the prefabricated post and core, P 21+PC and DC+ DC, showed significantly lower values in retention after thermocycling.
4. SEM photographs showed different images in each post and core technique. Fractured dentin surfaces in EC were covered with a smear layer. P 21 and SB were covered using a resin cement layer, and P 21+ PC, P 21 + DC, and DC + DC were covered using a bonding layer.

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It has been proved in previous studies that the surface treatment of cobalt-chromium alloy with gold dust was effective not only to increase the bonding strength between metal and porcelain, but also to cover metal color and prevent the border coloring.
In this study, two kinds of gold alloys for porcelain fusing indifferent compositions (Select 50 and Select 77 H, Ohura Precious Metal Co.) were selected to examine the effect of metal surface treatment with gold dust on the bonding strength. The size of gold dust (Super-Binder OG, Ohura Precious Metal Co.) used in this study was 1.0 μm in a uniform diameter.
The results showed that both alloys exhibited stronger bonding strength after treated with gold dust, particularly in the case of Select 50. Most of the gold dust remained on the fractured surface of Select 50 specimens after the shear test, observed by scanning electron microscope. It was also found that gold dust existed on both metal and porcelain surfaces in the case of Select 77 H.
The above results suggested that the treatment of a metal surface with gold dust could reinforce the bonding strength between gold alloy and porcelain. Furthermore, the bonding strength would increase greatly if the gold dust was bonded firmly to the metal surface.

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Unsteady temperature distribution was analyzed by using a two-dimensional finiteelement method. An excessive thermal stimuli was added to a maxillary central incisor which was restored with porcelain fused to metal crown and all ceramics crown. The results were as follows:
1. In the pulp, the pulp horn showed earliest temperature response.
2. Temperature distributions with time in the porcelain fused to metal crown were different from those in the all ceramics crown. Incase of all ceramics crown in thermal loading condition B (the lingual surface and part of the labial surface), the temperature rises on the labial side were late, and the influence orthermal distribution according to the kind of restorative materials was greater than porcelain fused to metal crown.
3. The temperature distribution with time under different thermal loading conditions was different for the porcelain fused to metal crown and all ceramics crown. In case of porcelain fused to metal crown in thermal loading condition B (the lingual surface and part of the labial surface), the temperature rises on the labial side were early, and it was similar with thermal distribution of loading condition A (all surface), the influence on thermal distribution according to the loading conditions was smaller than all ceramics crown.
4. Thermal loading condition A (all surface) gave higher temperature, 1.8°C, in porcelain fused to metal crown and, 2.6°C, in all ceramics crown at point P (the pulp horn) than thermal loading condition B (the lingual surface and part of the labial surface).
5. The highest temperature at point P (the pulp horn) in all ceramics crown was higher than in porcelain fused to metal crown and the highest temperature at point S (the lingual side near the center in coronal pulp) in porcelain fused to metal crown was higher than in all ceramics crown.

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