The present study was carried out to compare back strengths and electoromyogram of all related muscles among 8 healthy subjects as well as among different maxillomandibular relation for the purpose of investigating influences of postural changes in vertical maxillomandibular relation on the back strengths. The results obtained are described below:
1. Back Strength
1) In the opening position, back strengths were small in all subjects.
2) In the intercuspal position, back strengths tennded to increase when a splint was worn.
3) In other maxillomandibular relations, back strengths tended to increase when a 2-, 5- or 10-mm splint was worn, but tended to decrease when a 15-mm splint was worn.
4) Many of the subjects showed the maximum strengths when they wore a 2- to 10-mm splint.
2. Muscular Activity
1) In comparison with the activity of the masseter muscle measured in the opening position and the intercuspal position, its activities tended to markedly increase in other maxillomandibular relations. In comparison with those measured in other maxillomandibular relation, its activities tended to increase when a 2-, 5- or 10-mm split was worn.
2) Although the activity of the sternomastoid muscle measured in the opening position tended to decrease in all subjects in comparison with those measured in other maxillomandibular relations, no certain tendencies were observed on comparison of its activity measured in the intercuspal position.
3) There were no certain tendencies in activities of the trapezius muscle in all maxillomandibular relations.
4) There were no certain tendencies in activities of muscles of the upper and lower extremitis, including the gastrocnemius muscle.

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The rebuilding abutment teeth with metal casting had been applied mainly for thesingle root teeth down to 1970. On the other hand, carbon rod, investment materials, and the split method by using the metal casting have been applied for the rebuilding abutment teeth of the divergent and multi-rooted teeth.
On and after the 1970's, the study on the rebuilding abutment teeth of the multi-rooted teeth has been initiated to realize the practical application of the core for casting.
Co-Cr, Cu, Ni-Cr, brass, Ni-Ag, and graphite were used for the preliminary examination, since it was difficult to get the prescribed material which was previously designed by the other researchers. But, the results from the combined method of these materials and the precise readymade post did not seem to satisfy the object of this study.
6 years ago, it was easy to get the carbon steel by which the good fitness could be obtained in the combined method with ready-made post. The laboratory procedure on this technique was presented at the 42 nd meeting of Nihon University School of Dentistry by the author. Thereafter, the study on the development of the new materials was initiated, since it became difficult to get the carbon steel.
The experiments by using some materials for this technique indicated that the stainless steel and Co-Cr plated with Cu had a good fitness to the post channel.

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The purpose of this study was to investigate effects of typical Japanese eating positions on mandibular movement and EMG activities in head and neck muscles during chewing.
10 males chewed gums of 3 different hardness (soft, medium and hard) in cross-legged sitting (CL), chair sitting (CS) and standing (S) positions. Mandibular movement and surface EMG signals were recorded. In each position during chewing, head movement (HM) and forward inclination of the head and body (FIH, FIB) were measured by photography.
The results were as follows:
1. Maximal vertical displacement was the largest in CL position in chewing of hard gum.Maximal opening velocity was the largest in S position in chewing of medium gum. Opening phase time, closing phase time and cycle time were the longest in CL position in chewing of medium and hard gum.
2. Burst duration was the longest in CL position in chewing of all gums. Muscle activities at anterior temporal, posterior temporal, masseter and nuchal region of the trapezius muscles were most increased in CL position in chewing of medium and hard gum.
3. HM was the largest in S position while FIH and FIB were the largest in CL position in chewing of all gums.

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Based on the recent development of bonding technique and new ceramics, i.e. castable glass ceramics and high strength porcelain, the clinical use of laminate veneer crowns has been expected. The purpose of this study is to analyze the stress distribution in laminate veneer crowns and to establish the most effective clinical use.
Using some upper central incisor models, three dimensional finite element analysis was carried out to investigate the effects of various mechanical factors: location of loading points, preparation designs and type of ceramics. In each experiment, 180N loading force was applied to the model at 45 degree to the tooth axis.
The results were summarized as follows
1. By the load at the mesial line angle, the highest tensile stresses were caused in laminate veneer crown.
2. In case of covering the incisal edge, the tensile stresses were caused higher in laminale veneer crown.
3. It was found that the stress distribution pattern of Dicor crown was similar to those of CD-200 and Optec.

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We previously reported the three-dimensional analyzing system of occlusal tooth contacts. Using this system, we studied the functional tooth contacts and clearance of five subjects particularly during masticatory movements.
1. Tooth contacts and interocclusal clearance less than 1 mm can be analyzed during functional mandibular movements by using the six-degree-freedom jaw movement data and the three-dimensional morphology measurement of tooth surfaces.
2. Dominant tooth contacts were observed on the non-chewing side than on the chewing side during masticatory movements. The tooth contact sites on the non-chewing side corresponded to the region of contacts or tiny clearance which occurs during mediotrusive movement.
3. Tooth contacts and clearance at the beginning and the end of chewing cycle (jaw opening and jaw closing) were compared with those during lateral- excursive movement. Tooth contacts and clearance during masticatory movement toward opening more corresponded to those during lateral excursive movement.
In summary, the non-chewing side tooth contacts may play an important role in the support and guidance of mandible throughout the functional masticatory movements. That means there is a need for more precise evaluation regarding non-working side occlusal tooth contacts in functional movements.

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It is important to understand the mental states of erderly patients in their dental treatment. The purpose of this study was to investigate the relationship between oral status, masticatory function and intelligence level in elderly patients. Subjects were 37 outpatients among those who visited the Gerodontic Clinic at Tokyo Medical and Dental University. Twenty-seven patients (average age 76.4 yrs) had both upper and lower full dentures, and 10 patients (average age 76.9 yrs) had occlusal contacts with the remaining teeth in their molar region. Dental examinations which includes recording of the number of residual teeth and centric stops were performed. Each patient's masticatory ability was estimated by the standardized questionnaire which was based on the patients' subjective response in masticating 100 different kinds of food. Both the edentulous and the partially edentulous patient groups were evaluated and compared using Okabe's simplified intelligence scales and Hasegawa's dementia rating scale.
The results were as follows:
1. There was no relationship between patient's edentulous/partially edentulous status and their intelligence level.
2. There was no relationship between patient's masticatory ability and their intelligence level.

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The purpose of this study was to set up a questionnaire for evaluating the masticatory ability and the change of the masticatory ability of complete denture wearers. Twenty kinds of food were selected from Uchida's 100 foods and the masticatory ability and the change of masticatory ability of 145 complete denture wearers were scored.
The following results were drawn from the data:
1. The scores of the masticatory ability and the change of the masticatory ability obtained from chewing aspect of 20 foods were the same as the scores obtained from 100 foods.
2. The masticatory scores were associated with the maximal bite force of the patients.
3. The average score of the masticatory ability with new dentures was significantly higher than with present dentures.
4. The scores of the change of the masticatory ability between the new denture and the present denture were associated with the scores of the masticatory ability of the present denture.

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In conservation of basal seat under denture, it is important to know the intensity and distribution of pressures on alveolar mucosa and alveolar bone.
Using a simulation model of upper maxillas and poly-vinylidene fluoride film (PVDF) having piezoelectricity, we investigated how pressures on basal seat under denture are affected by load on artificial teeth. Strain in denture base was also considered.
The results were following:
The quantity of strain was greater on palatal side or palate than on buccal side or ridge. The direction of strain was inner on buccal side and ridge and outer on palatal side and palate.
When the distribution of pressure on alveolar mucosa and on alveolar bone was examined, pressure level was found to be greatest on ridge, followed by palatal side, buccal side and palate at a given load amount.
The peak of output voltage first appeared at strained part of denture base, followed by alveolar bone and alveolar mucosa in order.
These results indicate that PVDF is useful for determining the condition of strain in denture base and pressures on alveolar mucosa and alveolar bone.

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It has been commonly accepted that the craniomandibular disorders (CMD) have been characterized to show various clinical signs and symptoms. However the prevalence patterns of CMD signs and symptoms have not been thoroughly studied. The aim of this study was to clarify the clinical aspects of CMD. The samples were 413 CMD patients treated in our clinic. The prevalence of the symptoms were analyzed using the clinical records at first examinations. The following results were obtained.
1. Age distribution showed two peaks in twenties and fifties. The ratio of male to female was about 1: 5.
2. Pain of TMJ regions and masticatory muscles was the most frequent chief complaint, reported by 58.3% of patients.
3. Opening pain and limited opening were frequently observed with percentage of 65.0% and 60.4% of prevalence, respectively. TMJ noise and chewing pain were followed with percentage of about 50%. Spontaneous pain was less prevalent (25.3%).
4. Palpation pains of TMJ region, superficial masseter and medial pterygoid were observed in more than 50% of the patients, and those of lateral pterygoid, deep masseter, and posterior digastic were followed. Palpation pains of the other muscles were relatively low in percentage. Those of trapezius and occipital muscle were in less than 10%.
5. In associated symptoms, shoulder stiffness and headache were observed in about 30% of patients, however earache, tinnitus and dizziness were less prevalent.

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it has been well known that various symptoms are observed in craniomandibular disorders (CMD). The aim of this study was to clarify the prevalence patterns of the symptoms observed at the first examination of 391 CMD patients. Relationships between two different symptoms were analyzed using chi-square test and phi-coefficient. The following results were obtained.
1. There were strong relationships between opening pain (OP) and chewing pain (CP), OP and limited opening (LO), LO and CP, with phi-coefficient of 0.356, 0.270 and 0.237, respectively. Percentages observed were the following, OP-65.0%, LO-60.4% and CP-42.2% in samples.
2. Spontaneous pain (SP) was less prevalent (25.3%), however it was accompanied by CP, OP and LO with high percentage of 58.6%, 74.7% and 62.6%, respectively. Spontaneous pain would be regarded as a symptom indicating the severe stage of CMD.
3. Although TMJ noise was the third prevalent symptom (51.9%), there were no relationships to the other symptoms except LO. The onset mechanism of TMJ noises would be different from the other symptoms.
4. Headache and shoulder stiffness showed strong relationships to the other symptoms except TMJ noise, so that these could be typical in CMD symptoms.
5. Earache and tinnitus observed in less than 10% of patients showed strong relationships to spontaneous pain.
6. Dizziness showed no relationships to major symptoms. Dizziness would not be a typical CMD symptom.

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Palpation pains of head and neck muscles are important signs of craniomandibulardisorders (CMD). The purpose of this study was to clarify prevalences of palpation pains (PPs) of the muscles in 391 CMD patients. Relationship among PPs examined in different muscles were analyzed with the chi-square test and o-coefficient. The results obtained were as follows.
1. Frequencies of PPs ranged from 8.2% for occipital muscle (OC) to 54.7% for medial pterygoid (MP). PPs of the other muscles in this study -superficial masseter (SM), lateral pterygoid (LP), deep masseter (DM), posterior digastric (PD), sternocleidmastoideus (SC), anterior temporalis (AT), posterior temporalis (PT), and trapezius (TR)- were ranked in decreasing order of prevalence.
2. Mean rates accompanying the other muscle PPs of the individual muscles were ranged from 43.2% for MP to 81.1% for TR. The other muscles -OC, PT, AT, SC, DM, LP, and SM- were ranked in decreasing order of accompanying rate. That was almost in reverse order of prevalence. The prevalence and accompanying rate of PPs suggest that there was an order in onsets of the muscle disorders of CMD.
3. There were strong relationship statistically between PPs of OC-TR, SM-DM, PD-SC, AT -PT, MP-LP, and PD-LP. Those would indicate each, pair of muscles had kinds of functional relations in mastication.
These findings could contribute to understanding the muscle functions and the onset mechanisms of CMD.

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The present study was made to analyze the phonological adaptative phenomenon following the setting of plate denture.
Five subjects were used, with 6 words, including monosyllables, in sound cord connection of voiceless fricative /s/or/∫/as test sound and vowels, being adopted as test vocabulary. Taking mean and variance of the speech duration of consonant /s/·/∫/as well as coefficient of correlation of the duration between consonant and vowel within the monosyllable, as parameters, observational examination was made of the diurnal variation in 7 consecutive days.
The results indicated the appropriateness of an analysis by means of the vocabulary including/∫a/following the syllabic nasal or leptovowel and/se/following the syllabic nasal, for overall grasp of the adaptative phenomenon.

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In order to investigate the characteristics and reproducibility of the mandibular position during phonation of a Japanese syllabary single sound, intra- and inter-individual variations of the mandibular position were analyzed in 10 normal subjects using the Sirognathograph Analyzing System.
Results were summerized as follows:
1. With regard to the characteristics of the mandibular position during phonation of each vowel pronunciation, the order of the amount of the mandibular displacement in the vertical and anterior-posterior directions from maximum to minimum was IA/, /E/, /O/, /I/, and /U/ vowel pronunciation.
2. With regard to the characteristics of the mandibular position during phonation of each consonant pronunciation, IS/ consonant pronunciation showed the smallest mandibular displacement in the vertical and anterior-posterior directions of all the consonant pronunciation.
3. Phonation of each distinct single sound was performed at each characteristic mandibular position. However, high degree of reproducibility of the mandibular position during phonation was demonstrated in every subjects.
4. The mandibular position during phonation of a Japanese syllabary has a little inter-individual variations in both antero-posterior and lateral direction. However, they showed a large inter -individual variation in superio-inferior direction.

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The purpose of this study was to investigate the characteristics of patients' satisfaction on prosthetic treatment with removable dentures. One hundred and two Full dentures, 95 A-P dentures, and 106 P dentures were analyzed. On each denture group, applying the quantification method of the third type, scores of content and strength of their satisfaction were assigned to each rating grade of the factors constructing the structure of patients' satisfaction.
The following results were obtained.
1. In terms of statistic point of view, the most reasonable rating scales of the satisfaction were graded by the following 3 ratings ;“very satisfied”, “satisfied”, and “not satisfied”.
2. Determinants of dissatisfaction were “dental service” and “structure” in Full denture, “dental service” in A-P denture and “pain” in P denture.
3. Determinants of satisfaction were “esthetics” and “performance” in Full denture, “performance” and “taste” in A-P denture, and “strangeness” in P denture.
4. It is considered that above results should have to be verified with valid methods to measure patients' opinions on denture treatment.

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Difference in the area of preliminary impression surface resulted from two different impression techniques for edentulous arches, which employed alginate impression material and modeling compound, were examined. Projected areas on the tentative plane of occlusion and superficial areas of maxillary and mandibular impression surface of twelve edentulous patients were measured with the two-dimensional and three-dimensional graphic analyzing system. The areas of impression surface resulted from each impression technique were compared in maxilla and mandible. In maxillary impressions, projected and superficial areas of the two different impressions did not show any significant difference, whereas modeling compound impression were significantly larger than those of alginate impression in mandibular impressions.
Mandibular impression of seven edentulous patients were made five-times with each impression technique. The reproducibility of the outline of impression periphery were examined in each impression technique. The range of the outline indicated from these five impressions showed no significant difference between the two impression techniques, and also showed small value in each impression technique.
From these results, it was revealed that the area of modeling compound impression surface of mandible was significantly larger than that of alginate impression surface. And the range of the outline of impression periphery was revealed to be clinically small in each impression technique.

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Nowadays crowns and bridges are often provided to patients as prosthodontic care, which indicates the improvement of endodontic treatment and rebuilding of abutment teeth.
It also makes us use nonvital teeth as abutment teeth.
Although the opportunities are increasing, it's hard to say that all rebuilding of abutment teeth is carried out under ideal conditions. Therefore, we investigated the present conditions with X-ray film.
A study was made of 2, 543 posts which were fabricated for patients at the Department of Oral Radiology at Matsumoto Dental College from 1988 to 1989.
Some of the result were as follows:
1. Most of the length of the posts were 2-6mm.
2. 13.7% of posts in the upper jaw and 6.2% of posts in the lower jaw were 2/3 to 3/4 the ratio of post the length to root length.
3. In both upper and lower jaw, the ratio of clinical post length to clinical root length was less than 1/2 in most of the cases.
4. In most of the cases, the number of the posts for multirooted teeth were 1-2 posts.
5. In 70% of the cases, cast posts were fabricated.
6. In less than 10% of the cases, it was less than 1 mm in the minimum tooth substance width.

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Most wrought wire clasps are attached to the framework of removable partial dentures by soldering. The purpose of this study is to investigate the influence of soldering procedures on deformation and mechanical properties of clasp arms and strength of jointing parts.
In this study, circular clasp arms were made from Co-Cr alloy wires and soldered to supporting parts with a silver solder. Two kinds of temporary attachments, investing and spot welding, and two kinds of soldering methods, torch and electric resistance soldering were applied. These temporary attachment and soldering methods were combined, then four different procedures were compared.
The results were follows.
1. The change of distance between clasp tips during soldering procedure was smaller for temporary attachment by investing than spot welding, and for electric soldering than torch soldering.
2. By any soldering procedure, load required for 0.1 mm deflection of clasp arms increased significantly and permanent deformation after 0.5 mm deflection of them decreased considerably.
3. In both tensile strength and fatigue profile of jointing part, combination of spot welding and electric soldering was the best of all procedures.
These results indicated that without the deformation of clasp arms, combination of spot welding and electric resistance soldering was the most effective procedure in wrought wire clasp construction.

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Recently, with the development of good elastic impression materials and impression technique, very precise impression became available. Also, it is well known that forming precise impression of complete denture is important factor in the process of making denture which fits to a living body.
Various technique of forming impression to make denture are reported. As to forming impression at edentulous jaw, there are the ways such a pressurized impression, non-pressurized impression
and selective pressure impression in accordance with the degree of pressurization on oral mucosa. Among there ways of impression, the factors of controlling impression pressure are fluidity of impression material, forms of individual tray (vent, spacer and relief, etc.) and how to giving pressure (pressure load, pressure speed) are considered.
Accordingly, could not recognize the big difference in impression pressure among the impression materials made by different manufacturer. On the other hand, it has been clarified that the fluidity of the impression material and quantity of impression material have largely affected on the impression pressure.
The thickness of the spacer has also affected the mutation of impression, and appropriate thickness to minimize the impression pressure has been a sheet of paraffin wax.
As a result, herewith report that have contrived “the condition in the ways of gaining the impression” which proves the obtain ability of more precise impression.

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The purpouse of this study was to evaluate hydrophilicity of elastomeric impression materials. The contact angles before and after hardening were measured, using 8 types of hydrophilic impression materials and 8 types of hydrophobic impression materials and the following findings were obtained;
1. The contact angle 2 minutes after start of mixing was similar between hydrophilic and hydrophobic impression materials, and it showed to significantly decrease after 2 minutes (P<0.05).
2. The contact angle of hydrophilic impression materials was smaller than that of hydrophobic materials 10 minutes after start of mixing. The contact angle of all hydrophilic impression materials and 4 types of hydrophobic materials showed to significantly decrease after 10 minutes (P<0.05). However the contact angle of the remaining 4 types of hydrophobic impression materials did not significantly decrease as time went by (P<0.05).

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The gingival margins of restorations are mostly placed subgingivally because of esthetics for prosthodontic treatment on the anterior teeth. But the exposed area of the gingival margins of full coverage crowns, clinically called “black line, ” is usually seen with porcelain fused to metal crowns.
The gingival margins of crowns are already set along the “finish line” at tooth preparations. Such clinical procedures, however, are not always carried out precisely.
It was therefore assumed that one of the causes of margin exposures, occurring mostly near the deepest positions of the gum lines, might be traced back to the tooth preparations. Next, the influence of the differences in the shape and the deepest positions of the gum lines on the finish lines at tooth preparations was examined.
As a result, the deeper the depths of scalloped form of gum lines were, the less the amount of subgingival elimination. The exposure of gingival margins of full coverage crowns, “black line, ” is therefore ascertained to be already occuring at tooth preparations.

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A method for calculating the biting forces in healthy subjects with natural dentitions by electromyographic recording has been developed previously by T. Okajima (Tsurumi Univ Dent J 12: 367-390, 1986). This method was compared with two others for calculating the biting forces during voluntary isometric contractions in complete denture wearers. The other two methods were a calculation by curvilinear regression analysis and a calculation of the biting forces directly from data on the scatter diagram. Two conditions of isometric contractions of masticatory muscles of 10 subjects were tested. The two conditions labelled F and R differed from each other in the frequency of the contractions over a period of five seconds. The contraction cycle time of the condition F was approximately 1 sec. and the condition R was approximately 0.63 sec. In both conditions (F, R), no linearlity between the integrated electromyograms and the biting forces was found, moreover as the frequency was increased the correlation coefficients tended to decrease. By comparing the calculated values for the biting force with the known actual values, the errors in the calculation by curvilinear regression and the calculation of the biting force directly from the scatter diagram were significantly smaller than the calculation by linear regression analysis (p<0.01). There was no significant difference between the errors of the calculation by curvilinear regression and the calculation of the biting forces directly from the scatter diagram.

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There have been many reports on the relation between craniofacial morphology and jaw functions such as mastication, swallowing, jaw movement and bite force. However, most of these reports have to provided appropriate classifications of craniofacial morphology or definite indicators of jaw function in subjects.
The present study included 11 men having normal occlusion with natural dentition in the short face group, as in Takeuchi's study, and the relation between the EMG activity of masticatory muscles during vertical clenching and craniofacial morphology or force was studied. The results were also compared with the EMG activity obtained for normal face individuals.
The above finding suggest that careful attention to craniofacial morphology is necessary for evaluation of jaw function using the EMG activity of masticatory muscles as an index.

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In the present study, the author determined the effects of clinical experience of the examiner, surface properties of the material and environmental conditions on the quality of occlusal adjustment supply in terms of the discriminating ability, marking repeatability and the bleeding rate in the case of marking on precious metals for dental use.
The above findings indicate that marking of highest quality can be achieved when polyethylene-supported EM is used with untreated casting surfaces of precious metals for dental use under dry conditions, regardless of the length of clinical experience of the examiner.

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It is essential to determine the site and cause of impairment in the diagnosis of abnormality in function of the nervous and muscular systems. For this purpose, comprehensive judgment of data obtained from interview and various examinations is necessary. Such examinations utilize various types of reflex.
A myotatic reflex, jaw closing reflex, and a flexion reflex, jaw opening reflex, are two major reflexes in the stomatognathic system.
In this connection, with the aim of promoting the application of data on jaw opening reflex to determination of abnormality in the nervous and muscular systems in examination of stomatognathic function, the time course of muscular activity and the path of mandibular movement during jaw opening reflex was investigated in the same patients with craniomandibular disorder and healthy subjects as those examined in preceding Kawamura's study.

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