Four reversible hydrocolloid impression materials were studied by nuclear magnetic resonance (NMR).
Temperature hysteresis was observed in spin-lattice relaxation (T₁) and spin-spin relaxation (T₂), which corresponded to that of the sol-gel transition. It was found that the sensitivity of T₂ values were greater than that of T₁ values. T₁ and T₂ values were reduced with increasing concentration of agar.
It was suggested that the differences of T₁ and T₂ values in those impression materials were affected by their viscosity and the paramagnetic ion (Fe²⁺) contained within them.
This study demonstrated that the T₂ values could be one index of gelation in reversible hydrocolloid impression materials.

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The purpose of this research is to evaluate the acid solubility of fluoride treated dentin and the bond strength of an adhesive resin (Panavia EX^®) to their dentin in order to improve the adhesive properties of the adhesive resin to human dentin.
Human dentin were treated with 40% phosphoric acid for 1 min. followed by 1% TiF₄ aqueous solution for 3 min., and 0.2 M EDTA adjusted to pH 7.0 for 1 min. followed by 1% TiF₄ and 30% HEMA solution, respectively.
The results are as followed,
1. The shear bond strength of the adhesive resin to the dentin treated with the former increased more one half times to twice than the former acid treatment alone and the calcium elution into an acid buffer from the treated dentin was reduced to less than 30% of the acid treatment alone.
The presence of an impregnated layer of Titanium in the treated dentin and electron probe microanalytic observations resulted in reduced the dye permeability and advanced the obturation of the dentinal tubles.
2. The shear bond strength of the adhesive resin to the dentin treated with the latter increased more three times than the former acid treatment alone.

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Temporary restoration is useful to decide prosthodontic method. If the strength of the temporary restoration is so higher that is tolerable in services for long period, fixed prosthesis is better than removable one in regard to an appearance and a feeling.
The purpose of this study is to confirm experimentally the strength of the provisional fixed prostheses which are composed of acrylic resin teeth and adhesive resin. The compressive force need to replace the pontic which is directly bonded the extracted human teeth was measured in vitro.
Approximate 30 kg was needed to break the provisional adhesive pontic, whereas about 120 kg was needed to the posterior pontic reinforced with wire.
These results suggest that this method is useful as one of the provisional treatments.

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Clinical applicabilities of MB-4 proposed for the direct relining material to the metal denture base have been studied. Measurements of the amount of residual monomer after polymerization have been made in the first experiment using a spectrophotometer. The volume of the unpolymerized monomer in the sample of MB-4 was about equal to the conventional selfcuring relining resin. After 7-day immersion in water, the residual monomer of MB-4 decreased to the degree of aproximately the same as the heat cured denture base resin. Secondly the dye penetration from the interface of Co-Cr alloy specimen and MB-4 was observed using a stereomicroscope. An extremely small quantity of the dye penetrated between the metal and resin. This observation revealed that MB-4 had a remarkable sealing ability comparing with the conventional resin. It was concluded from these results that MB-4 provided the availability in clinical use for the direct relining material to the metal base.

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The purpose of this paper was to investigate microvibration on the masticatory muscle (M-MV), the possibility of its use for studying the functions of masticatory muscle and its usefulness of clinical application.
M-MV amplitudes of the masseter muscle (Mm) and the anterior temporal muscle (Ta) were measured in different mandibular positions with and without tooth contact. The signal analysis procedure consisted of observations on analogue waves of Mm and Ta and of assessment of M-MV amplitude (the root mean square, RMS) with AID converter and micro-computer (sampling frequency: 100 Hz, points: 512).
The results obtained were as follows:
1) It was considered that M-MV of Mm and Ta at the mandibular rest position most probably originated from the system of circulation (Apexcardiographic activity).
2) M-MV amplitudes of Mm and Ta upon further opening from the rest position were almost the same as those at the rest position and were synchronized with Apexcardiographic activity, but were larger with various degrees of closing from the rest position and were not synchronized with Apexcardiographic activity.
3) With changes of the horizontal mandibular position without tooth contact, M-MV amplitudes of Mm at all the eccentric positions and that of Ta at the retrusive position except the protrusive and lateral positions were increased and not synchronized with Apexcardiographic activity.
4) There were marked increases in the relations of activity in the recordings from Mm and Ta during muscle contraction compared with those at the rest position.
5) It was shown that the typical pattern of M-MV amplitude for Mm and Ta at centric occlusion was smallest in all horizontal and vertical occlusal positions.
6) M-MV amplitudes of Mm and Ta were increased by experimental muscle fatigue.
7) It was considered that M-MV during muscle contraction originated from vibrations of the muscle fibers.

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In this study, the surface roughness and the axial taper of dies were varied and ther influences on the elevation of the complete cast crowns after seating were studied. The result were as follows:
1. Impression materials should have a reproducibility of at least 30-50 μm Rz of surface roughness.
2. At each degree of the axial taper, there was a special range of surface roughness, where the inner surface roughness of the crowns and their elevation increased remarkably.
3. The elevation of the crowns grew proportionally larger, as the surface roughness became larger.
4. Within the range of 4deg;-12deg; of axial taper, GROUP 1 showed the largest elevation at any stage of surface roughness.
5. When the axial taper reached the level of 8deg;-12deg;, elevation of the crowns decreased.
6. When the elevation, the retentive force and other practical factors were taken into consideration, the recommendable surface roughness would be 8μm Rz at 4deg;of axial taper, 30μm Rz at 8deg;, 12deg; and 50μm Rz at 16deg;.

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In case of the retropositioned maxilla by fractures, the prosthetic treatment was performed by focusing to the occlusal balance and favorable results were obtained, functionally and aesthetically.
The purpose of this report is to examine the relation between the support or stability and occlusal contacts of the complete denture under the disharmonic situation of maxilla and mandible.
The results are as follows:
(1) In first stage, a provisional denture was provided to predict the prosthetic prognosis about its support and stability, because this procedure is very important to judge receptive capacity of the patient to the final denture.
(2) In process of the establishment of the final denture occlusion, it was most effective to monitor a mobility of the denture with MKG and to measure a bite pressure with the pressure indicating paper (Prescale).

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This study investigated the influence of the passage of air throughthe space between the upper and lower incisal teeth on phonetics.
Three experimental resin pontics with different horizontal overlaps-2, 4, 8 mm-were in turn temporarily cemented to the abutment teeth in two subjects. Phonetic test were performed with and without the experimental pontics and the resulting objective speech disorders, sound spectrograms, palatograms and mandibular positions were examined.
The results were as follows:
1. Regardless of the change of the horizontal overlap, objective speech disorders were not found in any of the subjects.
2. The sound spectrograms showed a decrease in the energy of the voice sounds /s/, /∫/ and /t∫/ as well as a lowering of frequency when the horizontal overlap was increased.
3. The contour of the anterior region of the tongue palate contact area decreased in one subject when the horizontal overlap was increased.
4. During the articulation of Is/ and /tf/ sounds, the mandibular position altered in one of the subjects by changes in the horizontal overlap.
5. The influence of the horizontal overlap on phonetics differed according to the individual.

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This study was carried out to evaluate usefullness of silent period of masseter electromyography (EMG) for diagnosis of unstable occlusion of full denture wearers one month after setting. Using bipolar surface electrodes, masseter EMG during tapping movement (72/min) was recorded. The latency (S. P. L.), duration (S. P. D.) and frequency of the silent period were measured on the EMG. Occlusal sound was checked simultaneously in order to estimate occlusal condition. The results were summerized as follows:
1. Ten subjects with stable occlusion were selected for a control group. Mean value and standard deviation of S. P. L., S. P. D., and frequency of the silent period obtained from the control group were 12.0±2.4 msec, 18.6±5.4 msec and 80%, respectively.
2. Latency and frequency of the silent period were not very useful parameters for diagnosis of unstable occlusion.
3. S. P. D. was found to be a useful parameter for diagnosis of unstable occlusion. In stable occlusion, S. P. D. was considerably short and less variable.
4. When S. P. D. was over 35 msec and frequency of the silent period was very few, the patient was suspected of having arithrosis of temporomandiblar joint.

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For clarifying the function of occlusion and obtaining better structure of articulator, I measured three-dimensional mandibular movements in lateral excursions starting from the intercuspal position, by a method which regards the mandible as a rigid body.
Firstly, I showed some characteristcs of the paths of some representative jaw points, such as incisor, first molar, and both side condyles, and Compared them with formerly reported data.
Secondly, I analyzed immediate movements which are now considered to be very important. By analyzing movements of the incisal point and the working condyle simultaneously, I found a rapid motion of the working condyle occuring in a initial phase during which the incisal point traveled a distance of merely 0.5mm.
As average moved distance of the working condyle in this phase was 0.19mm which was too small as compared with the immediate side shift, these motions seemed to occur in free way space of the condylar stable position. The influence of initial rapid motions of the working condyle on tooth's paths, however, couldn't be recognized.

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The situation of occlusal contacts is closely related to the masticatory function of edenturous patients. So there are many studies of occlusal contacts for the purpose of explicating masticatory function in edenturous patients. However, at the time of investigation of occlusal contact, they are not considered the interocclusal distance and occlusal position which have an influence on the masticatoy efficiency.
In this longitudinal study, the author measured the areas of occlusal contact in complete denture using a acrylic resin teeth at various occlusal distances and occlusal positions from a insertion of dentures to one year later. The conclusions are as follows:
1. In all occlusal positions, the areas of occlusal contact are about the same in early days.Afterwards, they increase gradually and reach maximum at six months later, and decrease one year later.
2. In all occlusal positions, measurement time and interocclusal distances influence areas of occlusal contacts significantly (α<0.05).
3. As a result of this study, in case of complete denture prosthesis using a acrylic resin teeth, it is clinically suggested that their teeth should be replaced with new teeth or reconstructed ith hard cold-curing resin about six months later.

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Recently Konuskronen has been accepted for the retainer of removable partial denture and the value of its application is recognized. However, there are few basic studies on Konuskronen and many questions aren't answered.
The purpose of this study is to find analytic method of the dynamical behavior of Konuskronen under the loading condition by using the finite element method.
In this analysis, “joint element” was used in order to simulate the conditions such as sticking, slipping and separating, of the contact area between two objects.
The results of the analysis indicated the followings.
The relative behavior of the outer and inner crowns of Konuskronen was showed by using the finite element method with joint element.
It was confirmed that the method of this study was adequate to the analysis of Konuskronen under the loading condition because of the consistency with the results of model experiment whick Kawasaki et al. reported.
From above results, it is expected that this method is applicable for the stress analysis of Konuskronen telescope denture.

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Prior to the clinical application of Pantronic, a device for the analysis and measurement of mandibular movements, we recorded analyzed mandibular movements in 46 subjects, with this device attached, in their 20's to 30's with no subjective abnormalities in jaw function. The mean measurements were obtained for various items displayed digitally. In the subjects with a protrusive angle of 20°C or less, superior wall insert tended to be too small to measure. In the range of immediate side shift between 0.6 and 1.2mm, rear and top walls with directions other than 0°C appeared on the display. Such a tendency in humans was similar to our previous report. Moreover, we studied jaw movements using the pantographic reproducibility index which showed no remarkable characteristics. The relationship of the index to measurement items requires further study.

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Among the various factors that affect the fitness of the soldering bridge, The electrical tacking method has taken into the three dimensional distortions of retainers were measured.
In conducting these studies, the author assembled three units fixed bridge with the second premolar and molar were as abutments and the first molar as a pontic on the mandible.
Following conclusions were obtained as a result.
1. During the electrical tacking stage, the retainers were displaced about 10 microns in each directions.(X, Y, Z)
2. At the soldering stage the liner distortion of retainers were paticulary larger in mesiodistaly.(ΔX)
The fixed bridge become about 25 microns shorter as the result of the distortion.
3. When compared the electrical tacking method and the invest method, electrical tacking method was about three times greater on the mesio-distal distortion, and two times greateron the vector distortion than the invest method.
4. In the case of the electrical tacking method was applied, the liner distortions were greater than the other rotational distortions caused by the complicate movement during the soldering stage on the retainers and pontic.

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The object of this study was to find out the effect of reinforcing wires (Co-Cr wrought clasp wire) in denture repair with the newly developed self-cured type 4-META adhesive resin (META-FAST). Evaluation was performed by the bending test on rectangle shape (70×10×2mm) resin specimens with repair portion in the middle.
Following Results were obtained:
1) Maximum bending strength of the fractured resin specimens repaired with resin alone showed 70% of those original values, but the amount of deflection under 2 kg load did not change.
2) In specimens repaired with META-FAST and Co-Cr wire, the increase of maximum bending strength, the load at the propotional limit and the decrease of deflection under 2kg load were observed.
3) The longer reinforcing wire became, the greater reinforcing effect were obtained.
4) Necessary length of reinforcing wire should be determined by the relation between load and stress distribution pattern in the denture-base for each individual case.

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The following experiment was performed for the purpose of examining the relationbetween changes of dental casting alloys in vivo and results of immersion tests.
Five kinds of dental casting alloys were immersed in 0.05% HCI, 1% lactic acid and Ringer'ssolution, respectively. After one-week immersion tests, surface changes of each alloy were observedby SEM and the chemical composition was also analized by EPMA. And weight changeshad been measured for one month. The results are as follows.
1) Gold alloy and Ag-Pd-Cu-Au alloy showed very few changes in weight, surface andcomposition.
2) Ag-Sn-Zn alloy was obviously changed in weight, surface and composition, especiallyby HC1.
3) Low-chromium Ni-Cr (86 Ni-10 Cr) alloy showed remarkable weight loss in HCI andlactic acid, and also pitting corrosion in HCl. But in lactic acid, its surface was changed soslightly that only dendrite structures were observed. Any immersing solution, however, couldhardly change its chemical composition.
4) High-chromium Ni-Cr (70 Ni-19 Cr) alloy immersed in HC1 showed remarkable loss inweight. But in lactic acid, its weight change was fixed after one day. Ringer's solution causedlittle change in its weight. And its surface was severely changed by HCl.

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