“A large number superposition graph” was made out of curved lines of condylar top and center. And then, the relation between front wall of mandibular fossa and condylar path was researched with computer graphics.
The results obtained were as follows:
1. The reasonable range of condylar path; nonworking side of lateral movement was 4.210mm on average of both sides, protrusive movent was 4.203mm.
2. The relation between the front wall and condylar path was shown by superposition graph. On the nonworking side, 37 examples were in parallel type, 49 examples were in closing type, 6 examples were in opening type and 8 examples were in undefined type. While on the protrusive movement, 41 examples were in parallel type, 44 examples in closing type, 7 examples in opening type and 8 examples in undefined type.
3. In reasonable range, the gradient of front wall was 54.86° and inclination of sagittal condylar path was 47.93° on the nonworking side, while the gradient of front wall was 54.70° and inclination of sagittal condylar path was 48.43° on the protrusive movement.

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Retrusive movement from intercuspal position (ICP) to retruded contact position (RCP) has been investigated by many authors with various methods.
However, 3 dimensional bodily movement of the mandible has not been yet enough investigated. The author wanted to clarify 3 dimensional movement pattern from ICP to RCP.
The movements of 3 maxillary and 3 mandibular LED targets were measured and the retrusive movements of incisal point, 1st molars and condyles are calculated with Kyusyu University 3-D movement analyzing system. And also tooth contact was checked clinically.
As the result, it was clarified that 3-D bodily retrusive movement pattern was more complex than had ever been thought. And the retrusive movement patterns of 10 cases were devided into 5 types. It is difficult to assume condyle movement from the observation of incisal retrusive movement. And tooth contact during retrusive movement act as an important role for movement pattern of the condyle.
The discrepancy between ICP and RCP is thought to be one of etiologies of stomatognathic dysfunction. Therefore, when we examine patients of mandibular dysfunction, we had better keep in mind the complexity of the condyle movement.
This article may give a basic suggestion as for mechanism of stomatognathic dysfunction.

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One of modern dental materials for crown restoration which is superior to other materials in esthetics and materials and bio-compatibility, is castable glass ceramics.
We have been made basic and clinical studies on one of castable glass ceramics, Dicor, which is developed by Corning Glass Works and Dentsply International Inc.
The stress analysis of the glass ceramic crown on upper central incisor and lower first molar under normal and abnormal functional condition was studied by Finite Element Method.
The following results were obtained by this study:
(1) The glass ceramic crown on both tooth is able to withstand normal functional condition.
(2) But it is not able to withstand parafunctional condition, such as stomatognathic dysfunction or bruxism.
(3) Compare with metal ceramic crown or metal cast crown, the stress concentration of the glass ceramic crown is relieved, because of the thickness of veneering material.

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The purpose of this study is to investigate mechanical properties of a superelastic Ni-Ti alloy for cast clasps. Bending properties of other alloys (Co-Cr, Au-Pt, Au-Ag-Pd) have been examined by the use of a universal testing machine to be compared with that of the Ni-Ti alloy which was examined in part 1. In this paper, repeated bending forces were applied on the tip of specimens supposed clasp arms by the use of a fatigue testing machine, then permanent deflections were measured by the use of a surface-shape recorder. It can be concluded that:(1) The force required to produce the deflection in 0.1mm (P_0.1: bending rigidity) of the Ni-Ti alloy was smaller than other alloys.(2) After repeated deflections (30, 000 times) of 0.25-1.00mm, specimens of the Ni-Ti alloy produced less permanent deflections than other alloys. In clinical cases, it is supposed that large amount of undercut is available by the use of a superelastic Ni-Ti alloy for cast clasps.

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The denture retention is affected with four groups of factors: physical, physiolosical, psychological and mechanical factors. The most important factor is the effect of saliva in the physical factors. A new measuring divice of the denture retention was fabricated for the purpose of exploring the influence of the viscosity of saliva. Six subjects took part in this study and they were classified into three groups according to their palatine shapes: deep, normal and shallow one. Palatal plates were fabricated from these subjects using self-curing resin. Glycerinum solutions diluted to five concentrations and mixed saliva samples were used as the mediating fluid for measuring the retention of the palatal plates. The viscosity of the mediating fluid was measured with a quet type rotation viscometer (Low Shear 30, Contraves).
The denture retention must not be discussed in view of the surface area of the denture base, but in view of the projected area of the denture base. The denture retention stands in direct proportion to the projected area of the denture base. It also stands in direct proportion to the viscosity of glycerinum solution and the viscosity of saliva.

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A 28-year-old man, whose mandible had been surgically corrected because of its prognathisrn, was referred to the prosthetic department for the treatment of his postoperative open-bite.
It was necessary to search and determine the new intercuspal position. The condylar position in the glenoid fossa could be helpful in this procedure. However, in the present case it seemed to be unreliable, because both condyles had shifted from the preoperative place at the stage of the intermaxillary fixation after the operation. Therefore, the habitua lopening and closing movements, which were very stable, were utilized to determine the new intercuspal position.
Follow-up studies were done at the stages of two years and three years and 10 months later after the prosthetic reconstruction and revealed that both condyles occupied about the center of the glenoid fossas.

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The most distal abutments supporting distal-extension removable partial denture are included heavy torsional stress. Therefore, the splinting of abutment teeth are used to distribute the stress among the multiple teeth. The purpose of this study is to analyze the dynamic difference between the primary splinting and the secondary splinting.
Finite element method was used to analyze. Three conditions tested by loading points were the following: 1. Load on the most distal abutment, 2. Load on the artificial teeth, 3. Load on the natural and artificial teeth. The stress and the displacement of abutments and supporting tissues were calculated. The results of this analysis were followings.
1. In the condition of loading on the most distal abutment, the stress concentration of this abutment on primary splinting model was larger than that on secondary splinting model.
2. In the condition of loading on the only artificial teeth and on the natural and artificial teeth, the stress concentration of abutments on the primary splinting model was larger than that on secondary splinting model.

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We developed a compact system for analyzing mandibular movements with the application of an infrared sensor, and examined factors which affected e its precision in order to determine the precision numerically.
The essential points were as follows;
(1) We were able to pick out the following three factors which affected the system.
(i) The distance between the LED and the infrared sensor (repressented as “L”)
(ii) The angle formed between the axis of the LED and the axis of the infrared sensor (called the angle of “deviation”; component of X axis:θ_x, component of Y axis:θ_y)
(iii) The rotation of the infrared sensor (termed the “rotation”:δ)
(2) According to the regression analysis, under the condition that L (=Lo+ΔL: Lo=100.0mm) was in the range (90.0≤L≤110.0), the maximum errors of the X and Y axes components were both 0.04mm when ΔL was neglected.
(3) Under the condition of the range (|θ_x|≤10° and |θ_y|≤10°), the standard error of the X axis component was 8.7 percent and that of the Y axis component was 9.7 percent.
We were then able to determine that δ was zero in the sagittal view.
(4)According to experiments involving trial and error, we could fulfill the requirements of 90.0≤L≤110.0mm, |θ_x|≤10°, |θ_y|≤10°, and δ=0°.
(5)Under the conditions indicated above, the precision of this system was estimated to be 0.15mm.

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Denture stomatitis is a term used to describe certain pathologic changes found in the oral mucosa of denture-bearing tissues. With regard to this etiology, infection with Candida species is one of the factors which may be implicated in the initiation of denture stomatitis. Because Candida species have been cultured more frequently and in larger numbers in denture stomatitis than in controls. C. albicans is the most common species. On the other hand, a carbohydrates is one of factors that promote Candida-induced inflammation. Therefore, we examined whether carbohydrates affected initiation and/or aggravation of Candida-induced stomatitis.
Male Wistar rats were used in this experimental study, and _{C. albicans} A 4-105 and C. albicans BIA-40 were used for inoculation. The animals were fitted with acrylic palatal plates inoculated with C. albicans A or B, and fed on normal or carbohydrate-rich diets. At 1 or 2 weeks afterinoculation, the animals were killed and their palatal mucosae were examined culturally and histologically. As a result, we have found a tendency for intraepithelial penetration of C. albicans A to be promoted by carbohydrates, but initiation and aggravation of C. albicans A-induced inflammation are affected to a lesser degree. With respect to C. albicans B, intraepithelial penetration and occurrence of inflammation are scarcely influenced by carbohydrates.

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We surveyed the restorations fabricated for outpatients at the Tsurumi University Dental Clinic during the ten-year period, from October, 1972 to March, 1983.
The results were as follows:
1) The fabrication rate of the fixed partial dentures and aft complete dentures of all prosthetic restorations changed very little in this period.
2) The rate of the post crowns the jacket crowns of all single artificial crowns decreased remarkably, while that of the full-cast crowns and resin facing crowns increased but slightly.
3) The Platinum-Gold-Alloy has taken place of 20 K-Gold-Alloy as the material of the single artificial crowns.
4) Both porcelain-fused-to-metal crown and the resin facing crown have been increasingly used as the abutment of the fixed partial dentures.
5) In cases of one missing tooth, the space previously occupied by the missing tooth was mostly restored by the fixed partial dentures, it was restored by the removable partial dentures instead of the fixed partial dentures.

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The purpose of this study was to investigate the effect of temporary cements on marginal gingiva after cementation of full cast crowns.
Four temporary cements were used in this study, i. e.: zinc oxide and eugenol cement (IP), non-setting zinc oxide and eugenol cement (TC), zinc oxide and no-eugenol cement (NG) and polycarboxylate temporary cement containing tannin-fluorlide preparation (HS).
Ten full cast crowns located at first and second premolar were cemented temporarily with each type of temporary cement for two weeks. Gingival crevicular fluid (GCF) volume at buccal gingival margin of full cast crowns were measured before and two weeks after temporary cementation.
GCF volumes were significantly increased after cementation of full cast crowns with IP and NG, and slightly incresed after temporary cementation with TC. However, GCF volumes slightly decreased after temporary cementation with HS, and the least effect to marginal gingivae was observed.

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Several points remain unclear about the effects on the periodontal tissues during thetime that an impulse on a tooth is transmitted to the apex of the root.
In this study performed from the standpoint of oscillatory science, random vibration wasapplied to teeth in an attempt to use data from the tooth crown and the apex of the root in determiningindirectly the kinetic properties of the periodontal tissues and whether it is possible toascertain at the tooth crown the kinetic properties of the apex of the root.
The results were as follows:
1. When an impulse was applied to the tooth, it was possible at the tooth crown to ascertaininformation about the apex of the root when the information was in the same direction as that ofthe impulse.
2. There was a high level of reliability regarding the attenuation value of the linear levelmeasured in the same direction as that of the impulse on the teeth.
3. Attenuation values for the tooth crown and the apex of the root were considered to bethe same in the case of a simple rooted tooth. For a multi-rooted tooth there was a difference of 2to 3 dB.

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This study was done to evaluate the thickness and shape of metal frameworks affectingthe adhesive strength of adhesion bridges under shearing loads.
Experimental and numerical models for the pseudo-three dimensional finite element methodwere examined.
The following results were obtained;
1. Adhesive strength of metal frameworks under shearing loads was nearly equal when thethickness was 0.55 mm or more.
2. Proximal extention of the metal framework was the most resistant shape under shearingloads.
3. Dimples of pontic side made in the abutment surface could help increasing the resistanceunder shearing loads.
4. The results of the experiments and the analysis of the pseudo-three dimensional finiteelement method were approximately equal.
5. The adhesive strength under shearing loads was considerably lower when a loose toothwas supposed as the abutment tooth.

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Using several brands of articulators, we examined the precision involved in themanipulation of them. First of all, we measured the vertical dimension between the upper andlower frame as we adjusted articulator. Secondly, we measured the vertical load given to theupper frame by handling. Thirdly, we measured the vertical displacement, which is caused whenwe loaded statically to the center of the upper frame, or also measured the rest displacement afterhaving removed the vertical load.
We got these results. The rigidity or the precision of articulators should be taken intoconsideration, and we should adjust the ‘Inclination of sagittal condyle path’(I. S. C. P.) to 30°and the ‘Inclination of sagittal incisal path’(I. S. I. P.) to 0° as we mount a model. However wefound error due to vertical displacement during these adjustments after mounting a model. Sowe should take these things into consideration and use articulators in the clinic.

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If the silent period is capable of being a useful tool in the diagnosis and prognosis of the temporomandibular joint dysfunction in adolescents, the silent period elicited methods need to be simple and reproducible.
The authors investigated the variable elicited methods of silent period and the variance between days of silent period using the 5 same men. The electromyographic activities in the anterior temporal and masseter muscles during tooth tapping and jaw jerk were recorded bilaterally and the duration and latency of the silent period variance was 3 days. The following results were obtained.
The duration and latency of the silent period during tapping and jaw jerk showed significant differences carring out 3 times for 3 days in both muscles. Therefore we think that carrying out a comparison using defferent days and subjects for the absolute value of the silent period provides data which is incorrect.
A variance of silent period during the jaw jerk was bigger than the tapping.
In regard to the duration of silent period in the tapping, in the temporal muscles it was longer than in the masseter muscles.

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The adherent condition of Candida albicans IFO 1385 to acrylic was studied in-vitro.
The results obtained were as follows:
1) The cells cultured in the synthetic media (YNB) containing 500mM galactose adhered to acrylic greater than that cultured in the YNB containing 500mM glucose.
2) The cells prepared by standing culture adhered to acrylic.greater than that prepared by shaking culture.
3) A sufficient number of the adherent yeasts to acrylic was obtained when the acrylic plates were incubated at 37°C for 90 min in the yeast suspension at the concentration of 1.0×10⁷/ml, and the plates were observed without staining.

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Three-dimensional analysis of condylar registrations, i. e. centric relation, muscular postition and Gothic Arch registrations, were carried out clinically.
The condylar points on the intercondylar axis of the upper articulator member were located most anteriorly by centric relation records and anteriorly by the muscular position records to the position in the intercuspation. It means that the condyle positions in the TMJs can be registered most posteriorly by centric relation records and anteriorly by Gothic Arch tracings to the intercuspal position of the subjects.
The three methods did not show the significant difference on the reproducibility of the registrations. The reproducibility on the antero-posterior and on the medio-lateral directions were better than on the cranio-caudal direction of the condylar position.

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Calcium phosphate crystalline ceramics (hereafter referred to as CPCC) is a glass ceramic and the so-called castable ceramic crown. Therefore, taking up CPCC as a material to be casted, adopting phosphate-bonded investment or cristobalite investment as a casting mold, with mold temperature of 400, 500, 600 and 700°C, and using centrifugal casting or air pressure casting as a casting method, 10 specimens were made respectively to the 16 different casting conditions, so that the occurrence of burn-in and devitrification could be studied. Further, the effect of devitrification on crystalization was also studied.
The following results were obtained.
(1) In case of adopting phosphate-bonded investment, the occurence rate of burn-in became higher as the casting temperature increased. Concering the casting methods, the burn-in occurrence rate was higher for air pressure casting than for centrifugal casting.
(2) When cristobalite investment was used, the occurrence rate of burn-in was higher for air pressure casting, while as for the mold temperature, the occurrence rate was maximum at 600°C, but conversely decreased at 700°C, roughening on the casted surface became prominent.
(3) The lower the mold temperature was, the lower the occurrence rate of devitrification was and the crystalline size became smaller.
(4) Crystals precipitated by devitrification became responsible for deformed crystal structure in the subsuquent crystallization.

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To investigate the effects of coping designs on the abutment teeth displacementsunder the overdentures, we constructed a test model simulated a partially edentulous mandible with only two canines and fabricated an experimental overdenture like an occlusal rim. We measured the displacements of the right canine with six different designs of copings respectively under the overdenture in two kinds of vertical load applications as follows:(1) in height 2 mm (short type) and 4 mm (long type);(2) in buccolingually vertical section the dome configuration and three types of square configurations consisting of the monoplane as primary contour and the unilaterally and bilaterally inclined planes made by grinding the buccal and lingual top contour of the monoplane;(3) the bilateral load (5 kg) and the unilateral load (2 kg).
The results are as follows.
The magnitude and direction of the abutment tooth displacement were influenced by the degree of crown-root ratio, the presence of line angle and inclined plane, and the soat of load application.
The short and dome shaped coping transmitted the least stress to the abutment tooth under the unilateral load.

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Swaged metal dentures have been reevaluated with the recent development and improvement of the 4-META adhesive resin.
18-8 stainless steels have ever been used for the material of swaged metal denture. Now titanium is investigated for the material of swaged denture so that denture bases can be lighter. But the titanium's mechanical strength isn't larger than the 18-8 stainless steel's. Then the titanium's metal denture have the possibility of the deformation during polymerization and function.
The purpose of this investigation is to establish and evaluate the effective reinforcing method of the titanium's swaged metal denture. Titanium plates were swaged on model as samples. In order to give the reinforcing structure, one or two half round shaped wax patterns were attached on the model. Mechanical strength was examined on above mentioned samples by the bending test using Instron universal testing machine.
Following results were obtained.
1) In case one reinforcing structure was given on samples, the load at the proportional limit of these bacame 2.2 times larger than standard samples. In case of two reinforcing structures, it became 2.9 times larger.
2) In case of one reinforcing structure, the deflection at the definite load decreased to 25% of standard samples. In case of two reinforcing structures, it decreased to 16%.

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Recent advances in adhesive resin materials containing 4-META have broadened the technique used in prosthodontic dentistry. Hayakawa et al. have developed a new method for a swaged metal plate system using 5 wt% 4-META resin. This system eliminated the need to build in retention of acrylic resin in customary swaged dentures and also eliminated difficult and time consuming laboratory procedures. In this study, mechanical properties of stainless steel dentures using that system were investigated. This type of denture was also compared with a Co-Cr alloys cast denture and an acrylic denture, using an uniform bending test of upper complete denture with steel wings exerting stress. Findings are as follows: The apparent flexual rigidity and bending strength of stainless steel dentures are superior to those of acrylic resin dentures, but are inferior to those of Co-Cr alloys cast dentures. At the breaking point, acrylic resin with 4-META completely breaks away from the metal surface in stainless steel dentures, but not in Co-Cr alloys cast dentures with regular resin and its retention. Therefore, stainless steel dentures need to have retention of acrylic resin for reinforcement.

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For taking accurate impressions, many material characteristics of the impression materials must be well understood. It is especially important to analyze the viscoelastic behavior of the impression materials. In our study, seven commercial alginate impression materials were used, and their linear viscoelasticity was measured using a creep meter (RE-3305, Yamaden Co.). The measurement condition were: load speed 0.5mm/sec, sample form φ 30mm×40mm, room temperature 23°C.
As for the results, the linear viscoelasticity of seven alginate impression materials appeared lower in stress and strain than expected, and their measurement values were from about 3.40% to 2.01%. Thus, we can consider them a standard for taking accurate impressions.

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The purpose of this study is to examine the impression accuracy of posts and cores using the combined reversible hydrocolloid and irreversible hydrocolloid, especially at various angles between the direction of the posts and the path of withdrawal of the impression tray. Five master models of clear acrylic resin and an impression tray of base metal were made particularly for this study. Each master model had two posts: one, in a parallel direction; the other, at a definite angle (0°, 10°, 20°, 30° and 40°) to the path of withdrawal of the impression tray. The permanent distortions of post impressions were measured on the standardized photographs with a profile projector.
The results are as follows:
(1) The distortions increased in proportion to the degree of angle and the depth of the measuring points.
(2) Dentloid and Hydrostick showed comparatively low distortions at 10°, 20°, but the distortions at 30°, 40° were considerable. A maximum distortion (0.40 mm) was found at the end of the 40° post with Dentloid.
(3) For reversible hydrocolloid, a radial pin proved to be effective in preventing distortion of the post impression and improving the impression accuracy.

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The aluminum slab coated with FEP was developed for the modification of the mixing slab. The influences of this slab and some mixing conditions on zinc phosphate cement were estimated. Selected mixing conditions and their levels were as follows ; mixing slab (glass slab, aluminum slab), mixing method (mixing according to JIS, mixing whole powder at the start), mixing period (30, 45, 60, 90 sec.), slab temperature (23, 18°C). P/L ratio used were standard consistency and clinical consistency. The properties of consistency, setting time and compressive strength were tested using orthogonal array (L 32). Following results were obtained.
1. The new modified aluminum slab was as good as the glass slab.
2. In the test of consistency, several effects of mixing conditions came out when the specimen was loaded soon after mixing. The shorter mixing time and the lower slab temperature spread cement disc larger.
3. In hygrostat set, changes of the net setting time were small. However, the net setting time in laboratory set was prolonged, when the mixing time was long.
4. There was no effective factor on compressive strength.

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The purpose of this study was to develop a three-dimensional measurement system and to investigate the influence of tray design upon alginate impressions.
This measuring system was made up of a measuring microscope and a personal computer.
A metallic model of a simplified maxillary dentition was prepared. Two types of trays were selected to make the impressions. One was a perforated stock tray and the other was an original occlusal tray which does not cover the undercut area of the teeth.
The coordinates of 19 points on the stone cast were compared.
The results were as follows:
1) This measuring system appears to be appropriate for measuring dimensional change and distortion of stone casts. This system could be applied to various uses.
2) The merit of this model is that part of dentition could be removed from the base. Therefore, both the master model and the stone cast were measured with the same three standard points.
3) Under the conditions of this study, all the stone casts had a tendency to be oversized.
4) The anterior teeth distorted toward the buccal direction, but the posterior teeth distorted toward the distal direction.
5) The cast made from the occlusal tray seemed to be more accurate than the cast made from the stock tray.

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