An experimental study on occlusal change of monkey by increasing vertical dimension to 1 mm and 5 mm sections with crown work was done. There were two groups used for study, one was setting crown work at only one side while the other was atboth sides. The period were divided into 10 days, 30 days, 90 days, 120 days and180 days after crown setting. The histological studies of temporomandibular joint were taken with the following results;
1. The tissues of the temporomandibular joint were changed at both 1 mm and 5 mm sections, especially the 5 mm sections.
2. Pathological changes on condyle head, disc and condyle fossa were present at both groups, especially on the opposite side to the crown work setting side.
3. Hyaline degeneration was present in all sections of the disc, and thedisappearance of the cartilage layer on condyle head and fossa made the tissues retrogress.
4. Bone absorption was present in the anterior portion of condylehead and the cartilage proliferation at the posterior portion of condyle head was recognized at both groups.
5. The condyle head and fossa of both groups on the 120 day and 180 day divisions were flat.

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This study is based on the notion that the mandibular rest position is made change by many different stimuli and those changes may reflect the funktional condition of the stomatognathic system.
On the other hand there were some observations that the mandibular oscillation was able to be found in mandibular fluctuation. The purpose of this study was to design the measurement system of mandibular oscillation and examine the electro-mechanical property of that system.
The subjects were 3 males with a normal tooth alignment and normal occlusion and 2males with some clinical dysfunctional symptoms in stomatognathic system. This system, appling a MKG, is able to record a mandibular oscillation and interocclusal distance.
Then the following results were obtained.
1. Mandibular oscillation was able to be measured by this system, appling a MKG.
2. Mandible always oscillated at rest.
3. In normal subjects, some characteristics were observed in mandibular oscillations at rest, and in the amplitude and the rhythm of mandibular oscillation there were some differences between nomal subjects andsubjects with some clinical dysfunctional symptoms.

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The present study concerns the effect of differences in the type of direct retainers and in the arrangement of rests on the distribution of pressures under dentures. A model with both mandibular molars missing (Kennedy classification of partial dentures-Class I) was prepared. Then two types of direct retainers, one using the Krol type R.P.I.clasp and the other using the Kratochvil type R.P.I.clasp, were selected.Then three types of rests were prepared.
Then the pressures under dentures were measured and the conclusions presented below were obtained.
1.Between the direct retainer and rest, the direct retainer tended to exert greater effect on the pressures under dentures.
2.Between direct retainers, the Krol type R.P.I.clasp tended to show greater pressures than the Kratochvil type R.P.I.clasp.
3.In the effect of differences in the rest arrangement, the smaller the number of rest, the greater the effect on the pressures.
4.In case of the fabrication of partial dentures against the mandibular bilateral distal extention case, the combination of the use of the direct retainer as the Kratochvil R.P.I.clasp and arrangement of the rests on the mesial side of the occlusal table of the second premolars on both sides and on the mesial and distal side of theocclusal table of the first premolars on both sides was suggested to be clinically the best design from the viewpoints such as distribution and uniformity of the pressures under dentures.

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Lately many researchers are advocating the dentist's posture known as the Home Position, claiming the need for reappraisal of the sitting posture from the standpoint of the systematization of work and the health of the dentist. In fact, theeffectiveness of the Home Position on cavity preparation has been observed from the standpoint of restorative dentistry, but there are many unclear points on the abutment tooth preparation of fixed prosthodontics. The author undertook a study of the effect that will be exerted on the prepared abutment tooth contour, when an abutment tooth was prepared for full cast crown of the mandibular right first molar. As the result of this study the author reached the conclusions as follows.
1. The distinctive features of the contours of the abutment prepared under the Home Position system were observed on the reduced extent of occlusal surface, the reduced extent on subgingiva and the axial tapers, but not on the reduced extent on axial surface.
2. The reduced extent of occlusal surface in excess of the directed extent was found on the mesiolingual cusp, the lingual groove and the mesiolingual cusp.
3. Subgingival reduction close to the directed extent was found on the lingual and distal surface; in the other parts, reduction had not reached the directed values.
4. Axial taper in excess of the directed degree was found on the distal surface, distolingual lineangle, lingual surface and mesiolingual lineangle. As the result the abutment teeth on the whole inclined in the direction of the mesiobuccal side.
5. While abutment tooth preparation for the full cast crown of the mandibular right first molar under the Home Position system gives rise to problems in the detailes of work, which constitute one of the most important clinical procedures like the continuity of margin, the present system has been found to be the clinically effective abutment teeth preparing method on the point of allowing work in conformity with directions.

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The author, conducted the following studies in order to clarify the causes of displacements and distortions in the ceramometal fixed partial prosthodontics (bridge) using the pre-solderd joint that occur during the laboratory procedure. In conducting these studies, the author assembled a ceramometal fixed bridge consisting of 8 units with a canine and a first premolar on either side in the maxillaserving as the abutment, for the portion in which four teeth-the central incisors and lateral incisors on both sides-were missing. Then, in order to find out when the framework of the fixed bridge was displaced or distorted and what the extent and direction of such displacements or distortions were, three-dimentional deviations of the framework were measured. As a result of these studies, the following conclusions were reached;
1. Throughout the laboratory procedure, it was at the time of pre-soldering and degassing that a substantial displacement ofthe fixed bridge was noted. Some displacement, although a minor one, was found at the time of the firing of body-incisor porcelain and that of glazing, too. However, no significant displacement was noted at the time of surface-grinding and that of the firing of opaque porcelain.
2. As to the displacement at the time of pre-soldering, the distortion of the soldered body (the portion made with one-piece cast method) itself was minimal; a kind of displacement was seen where the curve of the fixed bridge closed mainly as a result of two soldered bodies coming close to each other.
3. At the time of degassing, the curve of the fixed bridge opend wide as a result of the distortion in the portion made with one-piece cast method and the displacement at the soldered portion.

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Human chewing movement has been considered to be a cyclic movement with a regular rhythm for each individual. Chewing path, however, has been proved to be changed according to‘sensory input’from various peripheral nervous system (PNS). Analysis of paths of human chewing movements have been known to be useful to find clinical disorder of PNS and to diagnose the mandibular function and evaluate the prosthodontic appliances. Analysis of chewing paths for normal dentition adults and favorable full denture wearers have been performed to find and compare the basic data for the functional evaluation.
From results of this study, the chewing paths of full denture wearers with good retentive and balancing denture were found to be similar to those of normal dentition adults except delay of the cycle time according to extension of the closing phase and tendency to reduce maximum lateral movement.

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DME automatic analysis system of the jaw muscle activity during gum chewing was developed by aiming at obtaining higher efficiency and standardization of data analysis. The software was composed considering the actual process used in ordinary analysis: that is, the programs which were used to differentiate the onset and offset time of EMG burst were characteristically based on the differential values with the lapse of time of EMG envelope and MKG vertical movement per stroke.
Thirteen normal subjects' EMGs were analysed by DME system and compared with ones obtained by manual measurement. Time and power coordination patterns showed no significant differences compared with ones based upon manually measured data, though burst duration and integrated value generally exceeded ones obtained by manual.
In conclusion, the data obtained by this system in normal subjects were proved to be satisfactorily comparable with ones measured by manual.

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The pourpose of this study is to develop a more scientific system which can objectively catch the biophysical qualities of the tooth supporting structures, for the proper evaluation of the actual conditions of the structures.
The experimental tests have been started by bonding a force transducer and an accelerometer onto a maxillary central incisor. A certain amount of impact force has been applied by a spring-driven impactor to the force transducer to vibrate the tooth and its supporting structures, and then the force signal and the acceleration signal have been recorded simultaneously.
In the next experimental stage, a new analysis system has been developed and improved for easier application in the clinic, and put to the test on the subjects with teeth of different degree of clinical mobility.
The following results were obtained by this study:(1) The behavior of the impact force has been caught by the piezo-plastic-film force transducer.
(2) It has been found that the analysis of the vibration response obtained from the tooth and its supportingstructures under the impact force requires special consideration of the influence from the time duration of the impact force.
(3) There have been some differences in the results of the frequency analyses between the case where the whole acceleration response was taken as the object of the analysis and the case where only the free vibration was taken, in vivo.
(4) Both results obtained by the new analysis system and by the forced excitations (random excitation and swept-sine excitation) agree with each other.
(5) In the normal teeth tested, three peaks on the Fourier spectrum have been observed.
(6) It has been also observed that the peaks shown in the cases of the abnormal teeth move toward the lower area, compared with the cases of normal teeth.
From the above test results, it is obvious that the application of this new analysis system makes possible more objective evaluation of the tooth supporting structures.

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In order to estimate the influence of dental calculus on marginal bony changes in the interalveolar septa radiographically, inter-oral roentgenograms of 3002 teeth were observed.The roentgenograms were obtained from 166 dental patients with the bisecting-angle technique.The mean value of crestal bone height (bone score) on radiograms was less than 2.5 score units for each patient.
The results obtained implied that dental calculus probably take part in decrement in bony height of the interalveolar septa in the initial phase of bony loss.However, the calculus would not be a local factor from which V-type (Vertical or Wedge type) of bone defect in the septal margin originated, or if so, its effect seemed to be little.

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Intra-oral roentgenograms were taken with the bisecting-angle technique from 166-dental patient whose mean value of bone score was less than 2.5 units.The roentgenograms included pictures of 175 teeth with ill-fit restoration and of 955 teeth with dental calculus.
The results suggested that ill-fit restoration should accelerate a progression of marginal bone loss in the interalveolar septa.There were much in common between effects of ill-fit restoration and of dental calculus on the septa, although the deleteriousness seemed to be severer in the former than in the latter.

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The objective of this work is to investigate the horizontal tooth displacement and the behavior of the interdental proximal contact relation in function. As the transducer, two Magnesensors^®were used. The movement of the upper and lower left molars were measured. Based on the results of these experiments, the following conclusions can be made:
1. The upper molars showed the displacement ranging from 10to 146μm in the disto-lingual direction during biting.
2. The lower molars showed the displacement ranging from 16to 109 μm in the mesio-lingual or the lingual direction during biting.
3. The displacement of the lower molars in the mesiodistal direction was less than that of the upper molars. 4. The upper molars showed the displacement ranging from 91to 196 μm in the disto-lingual direction during mastication.
5. In the lingual or the disto-lingual direction, the lower molars showed the displacement ranging from 29 to 55 μm and 56to 73 μm in the buccal or the mesiobuccal direction during mastication.
6. The tooth which has the loose contact showed wider displacement path in the mesio-distal direction during mastication.
7. The dental arch width decreased in function.

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