Sensitization and allergic lesions resulting from metals in our living environment have often been reported. However, dentists have paid little attention so far on sensitization or dermal or mucosal lesions caused by metal restorations. We have established a team of 14 research institutions to perform patch tests with 18 kinds of dental metals and to conduct and epidemiological survey on the patch test positive subjects.
Prior to the study, application of the testing solutions and reading of the skin reactions were standardized. Patch tests were done on volunteers and patients with the total of 1, 728 subjects. On those patients who showed positive reactions to the patch tests, metal analysis for the intraoral restorations was done by the method developed by Inoue et al. The analysis results were then compared to the patch test results to investigate the relation between the two.
The following data was collected and discussions were made:(1) patch test posit ive/negative rates for the total subjects, (2) their differences regarding sex, age, or a kind of metal, (3) regional dfference, (4) relation between an individual with patch test positive result and his/her intraoral metal restoration (s), (5) types and locations of the lesions, (6) patch test positive rate (overall and of the each metal) for the patient group, (7) difference in the patch test positive rate between the volunteer group and the patient group, (8) comparison between the patch test positive rates among the M-9, M-11 or M-13 series, and among the different concentrations of the testing solutions, (9) comparison of the results between patch tests and their confirmation tests, (10) changes in the patch test reaction during the testing period.
From these results, it is considered that careful and adequate measures against the metal allergy should be taken, when the dentist starts the prosthodontic treatment.

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The study investigated early stage of regeneration of bone defect by an electrical stimulation in Rats. Electrical current source produced by a sheet of poling VDF/Tr FE film was used as irregular current and membrane.
The subject were Wistar-strain male rats with an average age of 13 to 15 weeks, which were then randomaized into 3 test groups. Under general anaesthesia, a hole (2 mm) was drill in femoral diaphysis of each rat in all groups. In the contral group, the hole was uncovered. In Group A, poling VDF/Tr FE film was covered. In Group B, the hole was covered by poling VDF/Tr FE film which generated a maximum average voltage of +1, 531--1, 612 m V when the rat moved freely. Histopathological observations were made by light and electron microscopy.
The results were as follows.
1. By electrical stimulation of the film, bone regeneration was facilitated to increase the number of mesenchymal cells in the endosteal site, and induced osteoblastic differentiation after three days.
2. By electrical stimulation of the film, new vascula formation had been effected to create a suitable enviroment in which bone regeneration could be facilitated after five and seven days.
3. The film could facilitated bone remodeling by osteoclast after seven days and matured bone tissue at the early stage.
4. The materials and electrical stimulation of the film did not obstruct dysplastic osteoblast and facilitated bone regeneration at early stage.

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We have developed a new denture processing method having with a pour type resin to tightly hold the artificial teeth by using a rigid core made by a two-stage investing procedure with stone and plaster (a low-expansion coefficient plaster core method).
In this study, for the purpose of evaluating dimensional accuracy of denture bases produced with a pour type resin, the denture bases with porcelain or resin teeth were processed by using the low-expansion coefficient plaster core method.
Vertical and horizontal displacements of artificial teeth and dimensional change of denture bases were measured.
The values found for the vertical and horizontal displacements of artificial teeth and dimensional change of denture bases indicated that very little change had occurred.
These results show that both porcelain and resin teeth in the stone-plaster core were more tightly gripped as compared to the conventional molds in pour type resin processing systems, such as hydrocolloid, silicone rubber and gypsum molds.
Consequently, some problems of the conventional pour type curing technique were improved by using the stone-plaster core made by a two-stage investing procedure.
It was suggested that this modified curing technique using a pour type acrylic resin was very useful in the construction of dentures when both porcelain and resin teeth were used.

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Tissue conditioners are temporary materials used to improve the health of the soft tissues of the denture-bearing areas. They are soft and flexible, and because of their pliability, they allow the bruised and distorted soft tissues to return to their normal size and shape, as well as reduce inflammation and swelling. In 1991, the International Standard ISO 10139-1 was established by Technical Committee ISO/TC 106, Dentistry, Sub-Committee SC 2, Prosthodontic Materials.
The purpose of this study was to evaluate the physical and mechanical properties of some tissue conditioners using this standard test, and also to analyze the composition of these materials.
The results were as follows:
1. Consistency test
All materials in this study agreed with ISO standards.
2. Penetration test
Some materials, after 2 hours, were below these requirements, and it seemed that the results were influenced by concentration of ethanol. After 1 week, all tested materials fell within this standard.
3. There was evidence of a correlation between the consistency and the concentration of ethanol.

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The soft denture liner is widely used to improve the comfort of the removable partial denture and reduce the residual resorption by reducing impact force.
The purpose of this study was to measure the impact force absorbing behavior of soft denture liners by drop-ball test with the accelerometer.
The results were as follows:
1. Molloplast-B and Molteno showed excellent shock absorbability. The thick spe Cimen showed higher shock absorbability than the thin specimen.
2. The thickness of the specimen did not affect the change of the shock absorbability with time. The shock absorbability of the Kurepeet-Dough decreased with time and its value showed one-half of the value at 24 hours.
3. An acrylic resin showed the shortest rising time to the peak in the materials investigated. Molloplast-B and Molteno showed the longest rising time to the peak.
4. The average of the rising time for Super Soft and Kurepeet-Dough hardly change with time. For Molteno and Molloplast-B, the variation of the rising time between specimens increased with time.

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Restoration of an edentulous space with a removable partial denture presents various problems of the design of a retainer set on a distal molar, when the molar shifts in angle or position. The two-dimensional finite element technique was used to analyze the design factors of the retainer's arm influencing the periodontium of an abutment tooth, for a direct retainer being set on a tilted molar.
The results obtained are as follows:
1. When only a retentive arm is used, the von Mises stress of the periodontium increases as the shifted position or angle of a retentive tooth increases.
2. When both retentive and reciprocal arms are properly located, von Mises stress is less than what with the retentive arm only. It is suggested that the reciprocation is effective for the stress -relaxation of the periodontium of a abutment tooth.
3. When both retentive and reciprocal arms are properly located and a retentive force is equal to a reciprocal one, the value of von Mises stress is within 0.10 kg/mm².
4. Effective design factors of a retainer's arm for the stress relaxation of the periodontium are suggested.

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In this report, two cases, who were missing anterior teeth and alveolar bone caused by traffic accident were treated by osseointegrated implants (Branemark system), and imediate bone grafting.
The results obtained were satisfactory in cosmetic aspect, as well as in speech and masticatory functions.

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The purpose of this study was to elucidate the properties of the alveolar bone under mechanical stress. The alveolar bone dynamics were examined in the mandibular edentulous ridges by means of two types of dentures, that is, the tooth-bone type (T-type) and the mucosa-bone type (M-type). The ridges under these dentures for 4 and 12 weeks were compared with each other, as well as to those without dentures (controls) in the same dogs.
Decalcified sections of alveolar bone were prepared for observation by contact microradiography and fluorescent microscopy.
The following results were obtained.
1. The trabecular bone in the edentulous ridge, as well as around the abutment teeth, increased in thickness and density under the T-type denture application, but there were few findings like that under the M-type denture application.
2. The resorption in the mucoperiosteal side and the deposition in the endosteal side were increased on the surface of compact bone at the top of the edentulous ridges underboth types of denture application, but such bone resorption was more remarkable under the M-typethan the T -type.
These differences of the bone dynamics seem to depend on the difference between the edentulous ridge and the dentulous ridge in the supporting structure of occlusal force.

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A photoelastic stress analysis technique has been conducted for many years as a test to analyze the stress distribution of the abutments and the alveolar bone under a load. The purpose of this study was to investigate the stress distribution of the abutments and the alveolar bone produced by the direct retainers of unilateral distal-extension removable partial dentures under a static load. Three types of direct retainers (R. P. I., Akers and Double Akers) were chosen, since they were frequently used in clinical case.
In the case of R. P. I., a load was transmitted vertically to the abutment and the alveolar bone. And the value of internal stress around the second premolar root apex was greatest. When Akers was applied, it forced the second premolar to lean distally. And the value of internal stress of the mesial bone near the second premolar root apex was greatest. Furthermore, when Double Akers was applied, it forced the premolars to lean distally, but a load was distributed vertically to the abutments and the alveolar bone. And the value of internal stress around the each premolar root apex was least. And the value of internal force under the denture tended to be least.

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The surface electromyographic (EMG) profiles were proposed for identifying normal muscle activity pattern by Winter et al (1987).
The purpose of this study was to investigate EMG profiles of masticatory muscles during deliberate unilateral gum chewing.
The EMG signals from bilateral masseter (Mm), anterior temporal (Ta) and anterior belly of digastric (Da) muscles of 5 healthy adults were recorded from for 90 seconds. The muscle activity was evaluated by the root mean-square (RMS) rectified EMG. Time averaging of each EMG over each chewing stroke was accomplished by normalizing each stroke period to 100% and then averaging each stroke at each interval over the chewing cycle to 0.3%. Normalization was achieved by setting the mean value of each subject's EMG over the chewing cycle to 100%.
The resuls were summarized as follows:
1. EMG profiles of masticatory muscles during deliberate unilateral gum chewing were made, which reduced inter-and intra-subject variability.
2. Each muscle showed a stable pattern of muscle activity at 60-75 seconds from the beginning of mastication.
3. EMG profiles in Mm of the working side were different from those of the non-working side, however, the profiles of Ta and Da were similar for both working and non-working sides.

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When freestanding individuals raise an arm as rapidly as possible, anticipatory muscle activities are evoked in the ipsilateral biceps femoris muscle (BFi) prior to the initiation of electromyographic activity of the deltoid muscle. This finding indicates that anticipatory activities of BFi are preprogramed in the brain, and reflect the function of positive postural adjustment rather than reorganization by postural reflexes.
The purpose of the present study was to investigate whether or not the above-mentioned anticipatory postural muscle activity, i.e. postural synergy, in sternocleidomastoid muscle could appear during ballistic voluntary jaw movements. Informed consent was obtained from a group of 10 healthy male subjects (24-27 yr) without functional disturbances of the jaw and with natural dentitions. Each subject was asked to perform the maximum clenching, the unilateral food-biting, and the maximum jaw opening as rapidly as possible.
As a result, postural synergy was observed during only the ballistic voluntary jaw opening.

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The purpose of this report was to reproduce accurate colors in metal ceramic restorations by using the Computer Color Matching (CCM) system. The conventional shade guide was used as the objective “target” colors, and a newly modified spectrophotometer was developed by our department that allowed non-contact measurements of small areas. Normal-shaped tooth preparations of the central incisors having labial reductions of 0.8-1.5 mm were done, and color shade guides were used to produce the objective metal ceramic crowns. The CCM program made it possible to calculate the amount and color of each porcelain layer within a specified thickness, and the metal ceramic crown was made based on these findings by using Shofu metal Aurora and Vintage porcelain. Opaque porcelain was baked at an even thickness of 0.3 mm based upon the CCM formulations, and the calibrated dentin and enamel was added later at their specified thicknesses.
Results of the CCM made metal ceramic crown showed the color to be indistinguishable from that of the original shade guide color with the unaided-eye. Furthermore, analyses showed the color difference dE (CMC) to be under 3.0, indicating a high accuracy level in terms of color reproducibility, and its possible use in clinical practice.

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In order to find the difference between the two major patterns of the masticatory movement, pattern I with the smooth opening toward the working side and convex closing, andpattern III with the opening toward the working side after initially being toward the non-workingside and convex closing, the muscular activities of the masseter and temporal muscles when chewingfish paste, chewing gum, peanuts and beef jerky were investigated.
1. In all foods tested, pattern III had a longer duration of masseter muscular activity thanpattern I, and with peanuts and beef jerky a statistically significant difference was observed.
2. In all foods tested, pattern III had a longer duration of the temporal muscular activity thanpattern I.
3. Pattern I had a larger integral value of muscular activity than pattern III for both masseterand temporal muscles.
4. Pattern I had a larger integral value per unit time than pattern III for both masseter andtemporal muscles in all foods tested, and a statistically significant difference was found between thetwo patterns in all foods tested except fish paste.
5. From the above results it was clear that the two major patterns of the masticatory path, pattern I and III, had their own characteristics and that there was a difference in the functionbetween the two patterns.

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We have developed the computer-aided video system for evaluation of occlusal contacts. The system used a video camera to register the transmitted images of silicone occlusalrecords and determined the intraocclusal distances from the intensities of transmitted light. Inorder to evaluate the sensitivity for determining the intraocclusal distances, silicone was pressedbetween glass plates and a steel ball. The steel ball was removed and the glass plates with hardenedsilicone on them were used for image input.
The conditions of the image input were as follows.
1. A glass plate with silicone was inputted ten times into the light box at various locations withat least five-minute intervals.
2. Ten glass plates with siliocone from ten silicone mixture were inputted one at a time.
3. A glass plate with silicone was inputted five times at each distance of 0, 5, 10, 15, and 20mm from the light box. Inputted images were used to make binary images at 23 levels of light intensities. The silicone thicknesses corresponding to the light intensities were geometrically calculated fromthe area of the binary images. Variations of obtained silicone thicknesses were used to evaluate thesensitivity. Influence of silicone inclination to the light box on the sensitivity was also presumedusing geometrical calculation. The result showed that the system could precisely determine thepremature contacts 5μm higher than the other contacts.We have developed the computer-aided video system for evaluation of occlusal contacts.The system used a video camera to register the transmitted images of silicone occlusalrecords and determined the intraocclusal distances from the intensities of transmitted light. Inorder to evaluate the sensitivity for determining the intraocclusal distances, silicone was pressedbetween glass plates and a steel ball. The steel ball was removed and the glass plates with hardenedsilicone on them were used for image input.
The conditions of the image input were as follows.
1. A glass plate with silicone was inputted ten times into the light box at various locations withat least five-minute intervals.
2. Ten glass plates with siliocone from ten silicone mixture were inputted one at a time.
3. A glass plate with silicone was inputted five times at each distance of 0, 5, 10, 15, and 20mm from the light box. Inputted images were used to make binary images at 23 levels of light intensities. The silicone thicknesses corresponding to the light intensities were geometrically calculated fromthe area of the binary images. Variations of obtained silicone thicknesses were used to evaluate thesensitivity. Influence of silicone inclination to the light box on the sensitivity was also presumedusing geometrical calculation. The result showed that the system could precisely determine thepremature contacts 5μm higher than the other contacts.

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The adaptation of crowns and bridges is a significant factor in relation to secondary caries or periodontal disease. In this study, eight premolars which would be extracted for orthodontictreatment were used to investigate in vivo adaptation of full cast crowns. The results wereas follows:
1. The mean cement thickness was similar to the results of an in vitro study previouslyreported.
2. All the impression methods investigated in this study were considered to be clinicallyacceptable. The individual tooth tray method was the most exact and stable of the three methods.
3. In two combined impression methods, the marginal cement was thicker than that of theaxial surfaces. This tendency was more remarkable in the mesial and distal surfaces compared tothe buccal and lingual surfaces.
4. Marginal cement layers of the buccal and distal surfaces were thicker than those of thelingual and mesial surfaces.

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We have investigated pour-type acrylic denture base resin and are convinced that it is very useful in making removable dentures. Recently, abrasion-resistant plastic denture teeth havebeen used frequently in the clinic. In this study, we made a bond strength test for three kinds ofabrasion-resistant plastic denture teeth and two kinds of pour-type denture base resin, in order toexamine clinical treatment methods when using these materials. These artificial teeth consist oftwo or three layers. The basal layer made of PMMA for adhering to the denture base resin wasremoved in this study. The treatment methods in the bonding surfaces of artificial teeth were asfollows: 1) no treatment, 2) treatment with a synthetic detergent, 3) treatment with a supplementalbonding agent, and 4) scraping off the basal surface of artificial teeth.
The results were as follows: 1. In no treatment, most of the teeth peeled completely or partiallyoff the bonding surface, 2. The effect of the treatment with a synthetic detergent was found to beincomplete, 3. In the treatment with a supplemental bonding agent or the scraping off the basalsurface of artificial teeth, we obtained a higher bond strength with all kinds of teeth and foundfractures in artificial teeth or basal resin block, 4. These results show that proper treatments to thebasal surfaces of artificial teeth before curing enable sufficient bonding to the denture base resin.

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Thirty one patients with internal derangement of the TMJ and 12 subjects with normal TMJ were selected and their MR imaging and border movements of the mandible were recorded. Inaddition, the relationship between them was examined.
In this study, the disk position and configuration in MR findings were classified as follows. Diskposition: superior, anterior and anterolateral (medial and lateral were omitted), grade of anteriordisk displacement (with and without reduction): slight, moderate and severe, disk configuration: biconcave, enlargement of posterior band, even thickness and biconvex.
The results were as follows:
1. Border movements of the mandible were influenced not only by unilateral or bilateralinternal derangement but also by with or without reduction of the disk.
2. Border movements in patients with anterolateral disk displacement were more severelyrestricted than those with anterior disk displacement.
3. Border movements were remarkably limited in patients with slight disk displacement, especially in unilateral cases with reduction of the disk.
4. Border movements in patients with even thickness and biconvex types of disk configurationwere a little restricted and rather similar to those of normal subjects.
5. There was significant correlation between border movements and disk position and configu-ration. It means that measurement of the mandibular movements is very significant to diagnose thecondition of internal derangements of the TMJ.

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We studied the effects of complete occluded maxillary and mandibular dentures with regard to maintenance, stability and surrounding supportive tissues and measured the stress-bearing of maxillary denture mucosa and bones at the centric occlusion. The results were compared with the stress-bearing of a complete maxillary denture with a good fit between maxillary and basal mucosa.
The results were as follows:
1. Distribution of stress-bearing
The stress-bearing of the top of the residual ridge of anterior teeth, part of the basal margin and buccal region was remarkably higher than that of fit complete denture (FCD). The stress-bearing of incisive papilla, top of the molar residual ridge, top of the maxillary tuberosity, part of the buccal region, palate and post dam was lower than that of FCD
2. Mobility of stress-bearing
1) It was especially quick in the top of the maxillary tuberosity and palate. The onset of stress-bearing of the residual ridge, basal margin and buccal region was slower than that of FCD. It was quick for the palate and post dam.
2) It was much quicker than the loading time of the maxillary bone of the top of the tuberosity, palate and post dam.
3) The start of stress-bearing was slower than that of loading of the palate and maxillary tuberosity.

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Biting force during functional movements reaches over the teeth, periodontal ligament, mandible and maxilla. It produces distortion in each part. This distortion corresponds to the biting force and influences occlusion. Many studies, therefore, have been made on this subject. But it is not necessarily easy to measure the distortion of periodontal tissues during function in man. The purpose of this paper is to clarify the influence of the distortion of periodontal tissues on physiological tooth movements. The horizontal movements of the upper first molar were measured during function. The upper first molar had made preparation for a cast crown. It had no occlusal and proximal contacts with antagonistic and proximal teeth, so that it did not directly recieve the bite force. The following conclusions were obtained:
1. The movements of the upper first molar, caused by the distortion of periodontal tissues, were influenced by the acting point of the bite force.
2. The movements of the abutment tooth during function were similar to the physiological tooth movements.
3. In the prosthodontic treatment, it is very important to reconstruct an occusal contact not to disturb the tooth movements caused by the distortion of periodontal tissues during function.

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It is known that occlusal contacts in the intercuspal position (ICP) change at different of clenching levels. Despite this fact, an occlusal adjustment generally is carried out at only one clenching level.
We investigated the variation of left-right (L/R) and anteroposterior (A/P) occlusal force balances in ICP with an increase of clenching level using a T-Scan system. In the first experiment, six normal subjects were asked to clench on the T-Scan sensor at 20, 40 and 60% of maximum voluntary contraction level. Statistics, which showed total force, L/R and A/P occlusal force balances, were calculated from these T-Scan data recorded and used to evaluate the occlusal force balances in ICP. Furthermore, we compared variation of L/R and A/P occlusal force balances with an increase of the total force between twenty-six normal subjects and nine patients with craniomandibular disorders (CMD).
As a result, these occlusal force balances of the normal subjects showed significantly less variation than patients with CMD.
We found that occlusal force balances in ICP must be evaluated at various clenching levels in order to discover variation of occlusal force balances.

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We tried to cast the pure titanium with the experimental thermal expansion inhibited investment which has less expansion. In this study, we investigated the effects of the concentration of colloidal silica included into the mixing liquid for castability and fitness of casting.
The results were as follows.
1. Using the mixing liquids including any concentration of colloidal silica, it was easy to dig out the castings and to remove the fired investment from castings.
2. There were few blowholes in castings.
3. On the surface roughness of castings, there was little difference between using the thermal expansion inhibited investment and using the investments on the market.
4. Using the liquid which included 10% colloidal silica for mixing, the castings shrank. But the increase in concentration of colloidal silica included in the mixing liquid for the investment caused the expansion of castings. This result shows that it is possible to compensate the casting shrinkage by using the experimental thermal expansion inhibited investment.

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A study was conducted for the purpose of grasping the influence of food characteristics on electromyographic (EMG) patterns during mastication. Cheese, kamaboko, takuan, senbei, surume and gumi were used as test food. Vertical jaw movement and EMG activities were recorded simultaneously from 10 healthy adults. EMG signal was divided according to the period of the maximum opening position of vertical jaw movement.
EMG profile for chewing stroke was accomplished by normalizing each period to 100% from the beginning of mastication to swallowing. The relationship between the texture of test materials and the EMG profiles was evaluated.
The obtained results were as follows:
1. The EMG profile of each test material showed various patterns. The degree of variability in the masseter was larger than that in the temporal and digastric muscles.
2. Owing to the delay of the onset of EMG activity, the duration of activity in the temporal and masseter muscle was shortened as mastication progressed.
3. Cheese showed the largest difference between the beginning of mastication and just before swallowing in the EMG profile of the temporal and masseter muscles. Surume showed least change in the EMG profile.

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Deflection of tooth and stress in its surrounding periodontium were analyzed with the two-dimensional finite element technique. Two types of finite element models of transverse sections at the mandibular first premolar were prepared. One type consisted of the tooth and its periodontium were used for analyzing the tooth deflection and its center of rotation. Another consisted of the upper components and alveolar bone was used for analyzing the stress distribution in periodontium.
The results were as follows:
1. Deflection and inclination of tooth increased as the loading angle increased and loading position was not on its axis.
2. The center of rotation appeared at the axis of apical side, about third of the tooth root, under the horizontal load. This center of rotation is called CR in the following.
3. CR was moved laterally as the loading angles to the vertical axis was decreased.
4. Total equivalent stress under the load toward the CR was less than that under the vertical loads.
5. Stresses in the horizontal direction at the height of the alveolar crest and the total equivalent stresses in periodontium increased as the moment caliculated around the CR increased. This relationship as not effected by the loading points and angles.

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