“Dual path graph” was made out of “a large number superposition graph”. The purpose of that was to compare the relation of condylar paths between protrusive movement and nonworking side of lateral movement. The results obtained were as follows:
1. The average of the distance between both condylar paths was calculated. Then, 56% of the subjects was less than 0.20mm.
2. The crossing state of both condylar paths was classified. In consequence of that it was found that many examples belonged to the type in which the path of nonworking side of lateral movement was nearer to the front wall of mandibular fossa than the protrusive movement was.
3. The inclination of sagittal condylar path of nonworking side was 46.41° on average on the right side and 49.56° on the left side, similarly, that of protrusive movement was 47.82° on the right and 49.78° on the left.
4. The results of the Fischer angles about 100 examples were classified into two kinds. The number of the plus was 43, and the average of them was 4.28°. The number of the minus was 55, and the average of them was-4.83°.

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In this study, contact corrosion of Ni-Cr alloy soldered by gold and silver solder was investigated. After being soldered, Ni-Cr alloys were immersed in physiological saline solution for 100 days. A detailed observation was made of the surface of the soldered alloy and the interface between Ni-Cr alloy and solder, using an optical microscope. In addition, distribution of alloy elements in Ni-Cr alloy-solder interface and strength of the soldered joint were examined.
The following results were obtained.
1. In case of soldering by gold solder, no corrosion occured at the soldered joint.
2. In case of soldering by silver solder, corrosion occured at Ni-Cr alloy-solder interface, and the solder became porous.
3. Pitting occured only at the surface of Ni-Cr alloys containing less than 19% Cr.
4. At Ni-Cr alloy-gold solder interface, a thin layer which might be caused by alloying with each other was observed using an optical microscope and EPMA. Tensile testing confirmed that the soldered joint between Ni-Cr alloy and gold solder was stronger than a layer of gold solder.

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The purpose of this study is to develop the image processing system, which allows the measuring of the thickness of the denture foundation. The system consists of (1) ultrasonic imaging equipment, (2) 8-bit microcomputer (OS-9/6809) and (3) software. The image data is made by the process of (1) smoothing, (2) binarization, (3) thinning and (4) calculation, after the determination of the area (ROI) for measurement and the input of the ultrasonic image data.
The results obtained as follows:
1) It took 11 seconds to transfer the ultrasonic image data (400250 pixcels) from ultrasonic imaging equipment to RAM disk.
2) Capacity for image processing was restricted to 6000 pixcels in raster but not in number of rasters.
3) The image was hardly degraded because the digital data of the frame memory were transfered directly into the computer without D/A, A/D conversion.
4) The alteration of the threshold level did not affect the measured results and the thickness of the denture foundation could be measured at the accuracy of 0.1mm.
At present the ROI and the threshold level are determined manually. The automation of this measuring system remains to be carried out in the near future.

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In this paper the following matters are reported: relationship between etching time and the tensile adhesive strength between the metal plating and the ABS resin-coated acrylic denture base resin, and that between tensile strength and the transverse bending strength of metal plated to the ABS resin-coated acrylic denture base resin.
The results were as follows:
1. Etching treatment gave a pitted surface to the ABS resin, but scarcely changed the surface of the acrylic denture base resin.
2. The adhesive strength between metal plating and the ABS resin was 80-120 kg/cm², with an etching time 30180 seconds, and the adhesive strength was dependent on the tensile strength of the ABS resin.
3. The adhesive strength was not changed following immersion in water for 12 months.
4. The transverse bending strength and the tensile strength of acrylic denture base resin were not decreased by etching treatment.
5. The transverse bending strength and tensile strength of acrylic denture base resin were decreased by coating with the ABS resin.
However, application of metal plating to the acrylic denture base resin coated with the ABS resin increased the transverse bending strength and tensile strength over those of untreated acrylic denture base resin.

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In order to explicate mechanical significance of cervical bulge ofbucco-lingual crown contours, viewed in direct stimulus by masticated food, I put themicrominiaturized pressure sensor on buccal marginal gingiva of mandibular first molar, and observed the foodpressure in masticating. Namely I researched that the difference of buccal crown contours andover-bite influenced the food flow and masticated food pressure on marginal gingiva, and Ihave come to the following conclusion:
1. According to the decrease of buccal convexity of contour, the food flow tendedto approach marginal gingiva, and the masticated food pressure on marginal gingiva tended toincrease.
2. According as convexity of contour was placed cervically, the food flow tendedto approach marginal gingiva, and the masticated food pressure tended to increase.
3. According to the increase of horizontal over-bite, the food flow tended toapproach marginal gingiva, and the masticated food pressure tended to increase.
4. It was suggested that action of buccal was the important element thatinfluenced food flow.
5. As masticated food is harder, the masticated food pressure tended to increase.

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Using several brands of articulators, we examined the precision involved in the manipulation of them. We reported in the first study mainly about the vertical displacement of the upper frame as we adjusted articulators. This time, we measured the lateral displacement of the upper frame as we adjusted the ‘Inclination of sagittal condyle path’(I. S. C. P.) or the ‘Inclination of sagittal incisal path’(I. S. I. P.). And next, we measured the one, which is caused when we loaded statically to the center of the upper frame, or also measured the rest displacement after having removed the vertical load. We got these results. The rigidity or the precision of articulators should be taken into consideration, and we should adjust the I. S. C. P. to 30° and the I. S. I. P. to° as we mount a model. However we found error due to lateral displacement during these adjustments after mounting a model. So we should take that into consideration and use articulators in the clinic.

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For the purpose of the application of laser welding in jointing of dental prostheses, the basic study was systematically performed in case of Ag-Pd-Cu-Au alloy, using a pulsed Nd: YAG laser. This article discribed the effect of the conditions of laser irradiation and specimen surface upon penetration.
Specimens were rolled sheets of 3 mm thickness alloy. Specimens were treated by three surface treatments; polished with emery paper (# 400), with alumina powder and with emery paper then oxidized (CuO, Cu₂O). The laser beam were irradiated on these specimens at various output energy levels and defocused distances from a focal point of a lens.
Increase in the laser power density by increasing the irradiated energy or by decreasing the defocused distance brought the increase in penetration depth. Under the same irradiation condition, the deepest penetration was obtained in the specimen with oxidized surface. And the deep penetrated fusion zone had rough surface.
The above-mentioned results exhibited that the penetration can be controlled by laser irradiation or surface conditions of specimen. Therefore, even with low laser output energy a deep penetration can be obtained, providing the absorptance raise by surface treatment.

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A number of engaging and disengaging of retainers induce those fatigue and consequent decrease in retentive force. In this study on the laboratory-made stud attachment consisting of a male (Type IV gold) like a snap and a female with semi-loop and linear portion made by bending a wrought gold wire, the maximum buldges of males, the distances between the female tips, and the retentive forces were measured before and after each stage of engaging and disengaging of predetermined cycles (10: initial, 1, 000, 3, 000, 5, 000, 10, 000). The males had 0.25 mm undercut. The females were 0.8mm in diameter and 3, 5, 7 and 10mm in length from the contact points with the males at the semi-loop portion to the points fixed in the resin base at the linear portion.
Results:
1. The initial retentive force, the abrasion of male, the permanent deformation of female and the decrease in retentive force all increased with the shorter female.
2. 5mm-length female kept the most amount of retentive force of approximately 380 to 190g during 1, 000 to 10, 000 cycles.

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We reported previously (J Jpn Prosthodont Soc, 30: 88-99, 1986) on the good results of our HV splint therapy for temporomandibular disorders. The present experimental study was made on therapeutic mechanism of HV splint using 11 normal subjects. A comparison was made of the joint spaces with transcranial lateral oblique radiographs of TMJs of each subject both at centric occlusal relation (at CO) and at the time of wearing HV splint (at HVS). Interocclusal relationship at HVS was also analyzed with the casts mounted on an individually adjustable articulator. The following results were obtained: 1) The total area of the joint space at CO was 47.0±12.6mm² (M±SD, N=22). The anterior, middle and posterior regions of the joint space were 15.7±5.4mm², 15.8±7.0mm² and 15.4±5.4mm², respectively, in area. These 3 regions had approximately equal area at CO. 2) The total area of the joint space at HVS was 68.7±7.3mm². The area of anterior, middle and posterior regions of the joint space were 20.6±7.3mm², 23.9±10.1mm² and 24.2±7.7mm², respectively. 3) The total area of joint space at HVS was approximately 1.5 times larger than that at CO. The ratio of expanding joint space by wearing HV splint was greater in the posterior and middle regions than in the anterior reigion. 4) The condyle was moved anteroinferiorly by 4.7±2.1mm, making an angle of 42.5±14.4° following wearing HV splint. 5) No significant differences were found in the interocclusal distances between the right and left sides at HVS.
These results indicate that condyle traction is obtained by use of HV splint.

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To protect the denture supporting tissue, it is important to make the pressure distribution on the tissue itself proper.
Therefore, it is necessary to give the proper occlusal contact. We have not seen any reports on the occlusal contact which produces the proper pressure distribution on the denture supporting tissue.
In this report we studied if the point of application of the biting force given by the occlusal contact can be obtained in the distribution of pressure on the denture supporting tissue.
We had a patient missing the first and second molar on the right lower jaw to test. We placed four diaphragm pressure sensors flush with the surface of the denture base. The nine fiducial points were placed on the occlusal table of the denture to obtain the point of application of the biting force.
To summarize the results:
1. We got the methodical change between the position of the fiducial point and the ratio of pressure on the denture supporting tissue.
2. If the position of the fiducial point was not changed, the ratio of pressure was constant regardless of the load in the region of 0-5kg.
3. We could estimate the point of application of the biting force given by the distribution of pressure on the denture supporting tissue.

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In our laboratory, we have been study the retention of Full Cast Crown was cemented with zinc phosphate cement after temporary cementation with zinc oxide eugenol cement.
In our previous report, we obtained the result regarding the retention force of cemented crowns, it's greater on specimens after temporary cementation.
This time we study to know the influence of temporary cementation and to compare the retention force of crowns, on condition that the specimens was pickled in three different circumstance (temperature at 60°C dries, humidity at 100%, and distiled water). Further more, we weigh the specimens in three different circumstance. Also, vertical dimentional changes with cementation was measured.
From these observations, following results were obtained.
1. Regarding weight changes, the specimens was pickled in humidity at 100% and distiled water is greater than in dries.
2. Regarding the vertical dimensional changes after cementation, it's greater on specimens after temporary cementation on each circumstance.
3. Regarding the retention force of cemented crowns, it's greater on specimens after temporary cementation on each circumstance.

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117 Mandibular first molars were radiographed mesiodistally and buccolingually and the convergency of three root canals was assessed on the supposition that every root canal should be prepared upto the two-thirds depth of canals.
The results were as follows:
1. From the viewpoint of the design of dowel-cores, there were three significant angles that is, angles between the mesial wall of the mesiolingual canal and the distal wall of the distal canal, between the buccal wall of the mesiobuccal canal and the lingual wall of the mesiolingual canal and between the lingual wall of the mesiobuccal canal and the buccal wall of the mesiolingual canal, means of 16.4°, -3.3° and 0.2° respectively.
2. The parallelism between the mesiolingual and the distal canals was easily attained in 12.8% and the one between the mesiolingual and the mesiobuccal canals in 64.8% of all mandibular first molars, because of no or very little undercut in itself.
3. Three root canals were easily prepared in parallel but in 2.7-6.8% of all teeth. In the others, therefore, every root canal should be widely prepared for parallelism or only one main root canal could be utilized for retention or two-piece dowel-cores could be fabricated.

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Disk-shaped materials of methacrylate resin, hydroxyapatite and titanium alloy were implanted in the dorsal subcutaneous tissue of 16 male rats of an inbred Wistar strain. After periods of 1, 2 weeks and 1, 2 months, the rats were sacrificed and the materials with their surrounding tissues were retrieved. For histological examination, the tissues were immediately immersed in a 10% buffered formalin solution, processed through a series of graded alcohols, embedded in paraffin and cut in 4-6μm thick sections. Sections were stained with hematoxylineosin stain and examined by light microscopy.
In the 2 months group, little or no inflammatory reactions were found around all of the materials. Fibrous tissue seemed to adhere to the methacrylate resin more than any other material used in this study.
The histological results indicated that the biocompatibility of the methacrylate resin compared favorably with the clinically used hydroxyapatite and titanium alloy.

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In our first report, we obtained the following result that by using infrared radiation heating furnace “Technomat” on firing, the shear bond strength was 70% greater than that of conventional type furnace using on non-precious alloy as “Uni Metal”. Although there were no significant difference on precious alloy “Uni Gold” and semi-precious alloy as “Aurora”. To get more reference about shear bond strength of other non-precious alloys by using “Technomat” and the relationship of those components, 11 alloys on market were tested by the same method and structural components were investigated by ICP. The results were as follows.
1. By push shear bond test, contained Beryllium alloys showed geater strength except “OC Metal”.
2. Without Beryllium alloys changed thier color strongly after firing and all of these but “Neo Nichrombond” showed less strength than those with Beryllium alloys.
3. By IPC investigation, most alloys component exprssions were generally coincide with real components. Although “Ticon” and “Neptune” contains Beryllium despite “No Beryllium” indication.

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Recently, so called TMJ dysfunction has been increased, but its mechanism and causes are not clear.
We have made researches about TMJ dysfunction by observation and analysis of chewing movement.
The purpose of this study is to examine the effect of human anterior crossbite on their chewing patterns and know a relation between the anterior crossbite and TMJ dysfunction.
The conclusions are as follows:
1. Anterior crossbite was assorted two types. One was functional anterior crossbite of which chewing pattern showed convergence, the other was just morphological anterior crossbite of which pattern showed no convergence. The convergence was found remarkably on the frontal plane and the horizontal plane, but on the sagittal plane, it was not apparent.
2. The subjects whose chewing pattern showed convergence had symptoms of TMJ dysfunction.
3. The convergence was hardly found on the subjects whose type of occlusion was cuspid protected occlusion, it was suggested that cuspid protected occlusion covered the effect of anterior crossbite, and as a result, TMJ dysfunction was not appeared.

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In our first and second report we obtained the following result that by using infrared radiation heating furnace “Technomat” on firing, the shear bond strength was generally greater than that of conventional type furnace on non-precious alloy with Beryllium. Although there were no significant difference on precious alloy “Uni Gold” and semi-precious alloy “Aurora”. The purpose of this study is to get reference about thermal distribution in the muffle of infra-red radiation furnace “Technomat” and conventional type furnace “Ultramat”, and about that how ceramic tray influences the temperature of ceramometal crown.
Sheet type thermocouple “ST-1”(0.15mm×1.0mm) was electrical soldered to Ni-Cr ceramometal frame of canine (measuring point), and were set in each muffle on the tray.
Heat treatment was carried out and data was processed by thermal data collector AM-7001. We obtained the following results.
1. The measured highest temperature was about 80 higher than the setting temperature 1, 000, by each furnace.
2. Thermal distribution of “Technomat” and “Ultramat” were almost uniform on every measuring points, but during firing schedule there was significant difference among points on “Technomat”.
3. The existence of gray ceramic tray for “Technomat” influenced the temperature of measuring points in both muffles, and the one on the tray was higher than the one without tray.
4. On “Technomat” measuring point on gray tray was higher than that on white ceramic tray, although there was no significant difference on “Ultramat”.

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On the concept of the clinical physiological occlusion, chewing movement is one of the most important mandibular movements. We have been studying the effect of a single tooth, the minimum factor of occlusion, on the chewing movement. The previous study of us showed that even the morphological changes of a single tooth might affect several parameters of chewing movements.
The purpose of this study is to investigate the effect of the substance of molar cusps and inclinations on chewing movements. 4 male subjects were carried out, and six types of experimental crowns were utilized on their mandibular first molar in order. Six experimental crowns are as follows. Control crown had Tripodism. 3 crowns were eliminated each contact, which is buccal outer, buccal inner, lingual inner inclinations. 2 crowns had only lingual or buccal cusp.
These subjects were asked to chew by these experimental crowns, and their chewing movements were recorded and analyzed by Sirognathograph Analysing System.
As the results, some parameters of chewing movements were significantly affected by the morphological changes of cusps and inclinations. The analysis of chewing movements, therefore, will be one of a functional examinations about the condition of each cusps and inclinations.

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