The distances between the anatomic landmarks on the casts of edentulous residual ridges were measured. These casts were obtained from 81 patients: 38 males and 43 females who had complete dentures at author's clinic. The corresponding distances were also measured on the stock metal trays used widely in Japan.
The measurements from the trays were compared with the ones from the casts. A statistical analysis of the measurements was carried out.
The results revealed that the stock metal trays did not always fit the anatomic oral structures of Japanese patients. An attempt was made to determine the sizes and shapes of stock metal trays which fit Japanese patients more accurately and comfortably, based on the statistical analysis.

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Accurate measurement of tooth mobility has been experimentally developed. In this study, the relationship between tooth mobility and percussion waveform using a new device was determined in a model and in humans. The newly developed tooth percussion device was found to be compact and the measurements obtained with this device were reproducible. Peak acceleration, duration, and peak frequency of the power spectrum of percussion wave corresponded significantly to tooth mobility, suggesting that these measurements are appropriate parameters of tooth mobility. The peak acceleration of the percussion wave caused by tapping a tooth correlated and decreased significantly with the increase in mobility among tooth groups divided according to clinical mobility of Classes 0, 1 and 2. The duration of the percussion wave caused by tapping a tooth correlated and increased significantly with the increase in mobility among tooth groups divided according to clinical mobility of Classes 0, 1 and 2. These findings indicate that the peak value and duration of the percussion caused by tapping a tooth can be used as indicators to objectively evaluate tooth mobility. It was found that tooth mobility can be easily and objectively measured by the newly developed device.

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Mucosal blood flow in human palate was measured by a temperature controlled thermoelectric method based on the thermal conductivity of mucosal tissue by means of a blood flow monitor and a noninvasive surface probe.
The effect of mechanical pressure on the palatal mucosal tissue was studied. Mechanical pressure (2.5, 5.0, 7.5, 10.0, 12.5 or 15.0gf/mm²) to the mucosal surface was exerted circumferentially around the surface probe by using an acrylic resin cover whose width of mucosal contact area was 1 or 4mm. After releasing the mechanical pressure, blood flow showed a tentative increase above that measured before loading the pressure. The rate of development of this phenomenon increased significantly depending on the amount of the mechanical pressure in each width of the mucosal contact area of the acrylic resin cover. The width difference of the mucosal contact area of the acrylic resin cover was shown to result in a different incline of the regression line for the relationship between the rate of development of the phenomenon and the amount of the pressure. It was suggested that the development rate of the phenomenon might be useful as a p arameter for the analysis of the physiological or mechanical properties of denture supporting tissues.

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The purpose of this study was to investigate the correlation between cervical vertebra alignment and factors of occlusion, dentofacial morphology, and head posture. The authors analyzed the relationship of cervical inclination and curve and dentofacial morphology using cephalometric photography. Subjects consisted of one hundred normal young adults without TMJ symptoms (an average age of 26 years old).
The following results were obtained:
1. The inclination of the dens showed a positive correlation to FH plane, palatal plane, occlusal plane and mandibular plane. In the case of forward flexion of dens, each inclination was high. But for backward flexion, each inclination was low.
2. The curve from the second cervical vertebra to the fourth cervical vertebra showed a positive correlation to the inclination of the dens. In case of forward flexion of dens, the curve was small. But for backward flexion, the curve was large. And it did not correlate to each plane. It was shown that inclination of the dens correlated with dentofacial morphology and the curve of vertebra.

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The purpose of this study was to clarify psychosomatic aspects of patients whose chief complaints were esthetic dissatisfaction with their teeth. Cornell Medical Index (CMI) test scores of three patient groups were compared. Three patient groups were the patients with esthetic dissatisfaction, the patients with stomatognathic dysfunction, and the patients who asked for prosthetic treatment without esthetic dissatisfaction and stomatognathic dysfunction.
The results obtained were as aollows:
1. In section Q (questions about Anger), the CMI score of the patients with esthetic dissatisfaction was significantly higher than that of the patients who asked for prosthetic treatment without esthetic dissatisfaction and stomatognathic dysfunction.
2. In the sum of sections CIJ, M-R, and A-R, CMI scores of the patients with esthetic dissatisfaction were significantly lower than those of the patients with stomatognathic dysfunction.

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This study was designed to attest the hypothesis that trabecular patterns of mandible are closely related to the stress distribution or the load transmission pattern. Two-dimensional finite element models of transverse sections at molar and the incisor region of the mandible were prepared for the analysis. Loads ranging from vertically to horizontally were applied at the occlusal surface of the tooth. Stress distribution pattern expressed by the maximum and minimum principal stress vectors was compared with trabeculation patterns of human specimens reported by Masuda (1960).
The following results were obtained.
1. Stress distribution expressed by principle stress vectors in finite element models had patterns similar to the trabeculation in human mandible specimens.
2. According to the frequency of trabecular patterns in human specimens, the trabecular formations in the mandibular molar region were heavily influenced by occlusal forces, particularly vertical forces. In the incisor region, biomechanical factors other than occlusal forces could also contribute to trabecular pattern formation.
3. Trabeculae in the mandible were divisible into tensile and compressive trabecular groups.
4. According to our results, past main loading condition of the tooth can be estimated with the trabeculation patterns.

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It was confirmed that the electrical activity in the upper half of the masseter muscle differed from that in the lower half, since tendon tissue laid along the upper half of the masseter muscle.
This study was conducted for measuring the deep temperatures at the superior and inferior portions of the masseter muscle at rest. Twenty normal subjects (10 males and 10 females) and 10 patients with craniomandibular disorders were selected in this study.
The findings obtained were as follows:
1. In normal subjects, no differences were shown in the deep temperature between the right and left masseter muscles. The deep temperature was significantly higher in the superior portion of the muscle than in the inferior.
2. In patients, the difference of deep temperature between the right and left sides was shown both in the superior and/or inferior portion of the masseter muscle.

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Recently, the number of patients with temporomandibular disorders has gradually increased. It is very difficult for general clinicians and dental students to make a diagnosis correctly on temporomandibular disorders, because signs and symptoms of this disease are extremely complicated. The objective of this study was to report on the process of developing a computer expert system TMDEX for diagnosing temporomandibular disorders and also to evaluate the effectiveness of this system in general practice.
The following conclusions were obtained:
1. TMDEX, the computer expert system for diagnosing temporomandibular disorders, was developed.
2. The coincidence between a clinical diagnosis and a diagnosis by TMDEX was 85.2%.
3. TMDEX was indicated to be useful for clinical education, because this system could propose the systematic analysis and diagnosis of temporomandibular disorders.
4. It was suggested that much clinical use of TMDEX might improve this advanced system.

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The purpose of this study was to investigate the temporal relationship between the masticatory force and the masseter muscles. Three subjects with normal stomatognathic function with the exception that a lower first molar was missing were selected. Three chewing gums differing in hardness were used as the test bolus, and masticatory force and electromyograms of the right and left masseter were recorded simultaneously. Masticatory force was measured using a 3-dimensional transducer mounted in a removable partial denture worn on the lower first molar.
1. With increasing gum hardness, burst duration (D) increased significantly. Burst duration (D) on the balancing side increased more than that on the working side.
2. At each gum hardness, duration from the onset of EMG to the appearance of masticatory force (D1) was almost constant. Duration from the appearance of masticatory force to the offset of EMG (D2) significantly increased on the balancing side, but tended to insignificantly increase on the working side.
3. Duration of resultant force (RD, RDP) was approximately constant.
4. Burst coordination pattern was roughly constant.

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Both visible light and chemical cured composite resins have been used in practice for rebuilding of the endodontically treated tooth.
In this study, a new type of curing method, dual cure, was fundamentally evaluated. After the irradiation of light to the dual-cured and light-cured resin specimens, their degree of conversion were measured at several depth of the resin specimens by a Fourier transform infrared spectrometer having a microscope and the obtained values were compared with one another.
The results were as follows:
1. The maximum degree of conversion in dual-cured composite resin was 83% when irradiated for 90 seconds only from the top of the specimen and 92% in visible light-cured one for 90 seconds, 30 seconds from the top and 30 seconds each from the side walls bilaterally.
2. There was an inhibition area of polymerization due to the existence of oxygen, up to about 1mm depth from the top of the specimens in both composite resins.
3. The maximum degree of conversion in dual-cured resin without the irradiation, actually chemical cure only, amounted to 76% at all depth of the specimens.
4. The irradiation from above only showed the highest degree of conversion at the shallow area in both dual-cured and visible light-cured resins. On the other hand, lateral irradiation resulted in the comparatively high degree of conversion at the wide area up to the deep layer.

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The purpose of this study was to evaluate the bond strengths of two abrasion-resistant plastic denture teeth (Endura, Duradent) bonded to pour-type denture base resin. The bond strengths of abrasion-resistant plastic denture teeth were compared with plastic tooth and porcelain tooth. The effects on bond strength produced by treatment of ridge-laps were also studied. Specimens were prepared and tested in accordance with JIS specification. The bond strengths of Endura, Duradent and the plastic tooth were not statistically different, and those were significantly lower than that of the porcelain tooth. The bond strengths of Endura and the plastic tooth were increased by treatment of ridge-laps surface with Dichloromethane and Duradent were increased by the same treatment and grinding ridge-laps.

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We colorimetrically studied the objective color expression of porcelain fused to metal crowns. It has been previously reported that a single opaque porcelain layer should be 0.25mm thick in order to mask the color of the metal base, regardless of the opaque porcelain color.
It was studied whether an opaque porcelain layer less than 0.25mm could mask the color of the metal base. The color of dentin porcelain baked on the 0.25mm thick opaque porcelain, which was baked on the metal base, was defined as each standard color. We studied the effects of the dentin porcelain layer on the metal color mask of the opaque porcelain layer according to the color difference. The following materials were used in fabricating samples:(1) 77.0% Ni-Cr alloy, (2) Yellow opaque porcelains B₂O and B₄O, (3) Red opaque porcelains D₂O and D₄O, (4) Yellow dentin porcelains B₂B and B₄B, (5) Red dentin porcelains D₂B and D₄B.
The results were as follows:
1. B₂ color (light yellow): If the additional layer of dentin porcelain was over 0.4mm, the 0.25mm opaque porcelain layer could be reduced by 0.05mm.
2. B₄ color (dark yellow): If the additional layer of dentin porcelain was 1.4mm, the 0.25 mm opaque porcelain layer could not be reduced.
3. D₂ color (light red): If the additional layer of dentin porcelain was over 0.8mm, the 0.25 mm opaque porcelain layer could be reduced by 0.10mm.
4. D₄ color (dark red): If the additional layer of dentin porcelain was over 0.2mm, the 0.25 mm opaque porcelain layer could be reduced by 0.05mm.

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Jacket Crowns with castable-ceramics and porcelain do not impede the natural appearance even if their margins are set up supragingivally or at the gingiva, because there is no metalic color for the conventional porcelain fused to metal crowns. Nevertheless, if the abutment teeth are stained or discolored, the margin should be set up subgingivally.
In this study, influences of the changes of the vertical positions of the cervical lines on the depth of the Finish Line was examined concerning clinical experiences of dentists, using three different artificial gingivas.
As the result, regardless of one's clinical experiences, there were tendencies of insufficiency in preparation subgingivally around the deepest part of the cervical lines, and of excess around the proximal interdentium. And when the deepest part of the cervical line is deeper, insufficiency of preparation is seen also around the Mesio and Disto-Facial Line Angle, and the operation of teeth preparations becomes more difficult. And then the cases of margin exposure of restorations on the facial side and inflammation of periodontal tissue at the proximal interdentium would have already existed at teeth preparations.
As a conclusion, it would be necessary to reconsider imperfection of teeth preparations including human errors, and to reexamine the approach through human engineering.

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This study was conducted to examine the influence on bond strength of the white layer produced after ceramic-making and of crystal mica in the cements when Dicor castable ceramics are cemented with enamels using Dicor light activated cements.
Shear and tensile tests of the bond strength were conducted together with observation of the failed surface by means of SEM (scanning electron microscope).
The following results were obtained:
1. Bond strength
1) The bond strength was 229-317kgf/cm² in the shear test, and 108-125kgf/cm² in the tensile test.
2) Cementing without a white layer displayed more bond strength in both tests than that with a white layer.
3) Cementing with cements containing no crystal mica displayed more bond strength in both tents than that with crystal mica.
2. Observation by SEM
1) When cementing with a white layer, destruction of needle-like particles, which developed in the white layer, was found.
2) When cementing with cements containing crystal mica, destruction phases were found on the cement layer.
These results suggest that Dicor cementation is an effective way to eliminate the white layer completely as well as cementing with cements containing no crystal mica.

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A series of studies has been conducted at our department to investigate the relationship between the condition of the stomatognathic system and the systemic condition, on the principle that the stomatognathic system must be regarded as a part of the whole body. As a part of these studies, the gravity fluctuation and activity of antigravity muscles were investigated to estimate the effects on upright posture.
With reference to Shimada's report, the author measured the changes in the gravity fluctuation and activity of antigravity muscles to estimate the effects of the prolonged retention of anterior or lateral mandibular deviation. The results were as follows:
1. Gravity fluctuation tended to increase beyond the normal range of variation when the mandible deviated anteriorly or laterally to the right or left. This parameter tended to increase more with lateral deviation than with anterior deviation.
2. Muscular activity of the anterior temporalis, middle sternocleido-masteoideus, upper trapezius, and lateral gastrocnemius tended to increase beyond the normal range of variation with the mandible deviation. The increase tended to be greater with lateral deviation to the right or left than with anterior deviation.

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At our department, the relation between the stomatognathic system and the systemic condition has been studied from various angles using a gravity fluctuation analysis system, an equilibrium function test, and electronystagmography. We have reported that changes and abnormalities in the stomatognathic system disturb the equilibrium function and also affect the maintenance of the upright posture and nystagmus. In future studies on this relationship, we will try to determine how a stomatognathic disorder affects the auditory pathway and brainstem using the auditory brainstem response (ABR), which is an early component of the auditory evoked response used for neurological testing in the clinical practice of otorhinolaryngology and other fields.
The effect of each occlusal abnormality was investigated in these studies, but not observed in detail for several days after removal of the occlusal interference, although such observation did seem to be necessary.
Accordingly, the author introduced experimental occlusal interference onto the first molar of the mandibular main mastication side in 14 normal subjects and, using ABR, examined mainly the condition of recovery for several days after removal of occlusal interference. As a result, it was noted that the peak latency and the right-left difference of ABR were prolonged by interference, and that the peak latencies of waves I and III had almost completely recovered 1 week and 48 hours after removal, respectively. It was inferred from the prolongation tendency of the peak latency of wave I and the right-left difference of ABR due to interference that abnormalities in the stomatognathic system, such as occlusal interference, affect not only the stomatognathic system, but the auditory pathway as well. It was shown that this prolongation almost completely disappeared 1 week after removal of the occlusal interference. These results indicate that normalization of the stomatognathic system also contributes to the recovery of auditory system.

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The oral condition of 12 inpatients, who were confined to bed and had received dental treatment, were followed up for one to four years and reviewed in order to study the effects of dental maintenance. The following results were obtained.
1. Examinations (Hasegawa Method) made on dementia for four years showed aggravation in seven patients, no change in four patients including a normal patient, and marked improvement in one patient.
2. The average number of the remaining teeth at the first checkup was 9.25, while that of the teeth after the treatment was 3.75. This indicates the teeth necessary for treatments had been left untreated.
3. Clinically, the remaining teeth showed slight mobility because the teeth were combined and played the role of abutment teeth. However, three patients showed 7mm maximum pocket depth and almost all patients had the high value of the periodontal leakage from dental furrow (periodontal value over 100).
4. According to denture plaque scores (revised Tarbet method), only two patients were confirmed to have clean fixed dentures, while ten patients had worn dirty dentures.
5. Candida albicans was detected in oral mucosa in 9 patients. Three of them had levels over 3, 000CFU.

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A method of applying the CCM system to reproduce natural tooth color in metal ceramic restorations was successfully undertaken by a newly modified spectrophotometer and measuring system.
The spectrophotometer utilizes bidirectional (45/0) geometry and a telephoto camera lens capable of measuring small areas (1×2mm) of the tooth and gingiva by the “noncontact” method. Furthermore, color measurements were automatically done by means of a scanning program.
The standard deviation (S. D.) of the reflectance factors, measured 10 consecutive times, was under 0.16, and the color difference dE was around 0.21. Both the measuring data of the Munsell color chips by this spectrophotometer and integrating sphere spectrophotometer Macbeth CE 3000 were nearly identical.
It was concluded that this newly modified spectrophotometer could measure small areas of the tooth efficiently, and also be beneficial for use in dental clinics and research.

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Due to simpleness and the patient's comfort, instruments for the analysis of jaw movements by means of a magnet were very useful. But if has been reported that Mandibular Kinesiograph and Sironathograph have a difference between the actual locus and the reproduced locus.
In this study, we report reproduction accuracy with Bio PAK.

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Bioactive Glass has been known as a material that can be bound directly to bone, and its application for dental implants has drawn much interest recently.
However, there are only limited sources on occlusal contact with the implant.
The purpose of this study was to longitudinally observe the jaw bone around the dental implants using Bioactive Glass with the aid of standard X-ray photographs. Conditions of the jaw bone were determined according to the elapsed time between the period of tooth extraction and implant insertion. The mandibular fourth premolars of 10 beagles were extracted, and implants were inserted into their places at periods of 4 and 12 weeks. Occlusal contact was applied by placing a crown on the opposite tooth.
In case of the 4-week control group, the level of the bone surrounding the implant tended to decrease after 8 weeks, but not so much thereafter.
The study group showed a larger decrease in bone level during the first 4 weeks compared to the control group, but was the same thereafter.
However, regardless of whether the insertion of the Bioactive Glass implant was 4 or 12 weeks, the level of bone change was similar.

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The purpose of this research was to study muscle fiber conduction velocity (MFCV) of the masseter muscle during recovery from fatigue.
The subjects were 7 healthy male volunteers, aged 24-30 years. Masseter muscle fatigue was induced in subjects by asking them to perform protracted clenching at 75% of maximum voluntary contractions (75%MVC) while the mean power frequency (MPF) of surface electromyogram in the muscle was being measured. As soon as 75%MVC clenching finished, the subjects were asked to perform intermittent weak contractions (10 seconds of contraction and 10 seconds of rest) for 8 minutes and MFCV of the masseter muscle was measured.
In all subjects, an average of 32% of MPF reduction was observed at the end of 75%MVC clenching. Although there were some variations in MFCV during recovery due to unequal fatigability of units, from 22 units measured, MFCV increased in 17 units (p<0.05) with an average of 41% increase from the initial velocity value.
Therefore, the findings in this study indicate that MFCV of the masseter muscle decreases during fatigue and decrease of MFCV may be a contributor to the power spectrum in order to lower frequencies during fatigue in the masseter muscle.

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The purpose of this research was to evaluate the manipulation of the newly developed six degrees of freedom jaw tracking device using magnetic fields in quadrature phase. Jaw movements were recorded by this device in 15 female subjects. Further the jaw movement data was compared to that of 15 male subjects recorded by digital jaw tracking device (MM-JI). None of the subjects showed any clinical signs of craniomandibular disorder.
The results were as follows:
1. Manipulation of this device has been improved dramatically compared to the digital jaw tracking device (MM-JI), however it still needs improvement, such as the ability of jaw movement recording range.
2. The maximal jaw opening movement recorded in male subjects was significantly greater in comparison with that in female subjects (p<0.01).
The maximal condylar movement and mandibular rotation in male subjects were also greater than those in females. However, no significant difference was observed between males and females (p>0.05).
3. The influence of measuring point on the mandible or sex differences was found to be minimal in determining maximal mandibular rotation and therefore, it can be regarded as an important parameter of movement to the temporomandibular joint.

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