The T-Scan system which was developed by Dr. W. L. Maness in 1987 is a new computerized device which can analyze time and force of occlusal contacts. It has potential to analyze occlusal contacts quantitatively.
The purpose of this study is to investigate its accuracy for measurement as quantitative analysis device.
The following conclusions can be drawn from this study:
1. The time display of T-Scan system was approximately 64/100 of real time.
2. The force display of T-Scan system showed weak correlation to loads when loads from 1 to 10kg were added on the sensor at random position.
3. T-Scan sensor had non-sensible areas caused by its structure.

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Eight healty participants performed horizontal isometric jaw movements with maximum voluntary contractions of the jaw muscles until they could not tolerate the task. Electromyographic activities bilaterally recorded from the superior and inferior regions of the sternocleidomastoid muscle and the nuchal and shoulder regions of the trapezius muscle were observed.
The results obtained were as follows:
1. In more than 94% of 32 trials, the amplitude of EMGs during the task were higher than those at rest, and in more than 78%, temporal changes in EMG burst were synchronized with the onset-offset of the exercise.
2. In more than 72% of all trials, small amplitude EMG lasted after cessation of the task.
3. Muscle activities of the lateral cervical region during the exercise were superior to the activity of the nuchal and shoulder regions, and amplitude of EMGs in the neck and shoulder regions tended to be the highest during isometric retrusion.
4. These results don't contradict with our hypotheses that occlusal habits might be one of cause of the unpleasant sensation in the neck and shoulder regions and that sustained isometric retrusion might have heavier effects on it.

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The abutment teeth preparation had been done by five dentists who had 2-5 five years clinical experiences.
During the teeth preparation, dentists had kept home position of operator's posture.
The abutment teeth preparation with full cast crowns for the maxillary left fixed prosthodontics (three-unit bridge, the abutment teeth were the second premolar and the second molar) had been done for the first molar tooth loss.
The prepared teeth surfaces were measured, examined and following results were obtained.
1. The reduction of the teeth for bridges abutment showed same tendency as the single crown preparation.
2. The parallelisum of prepared abutment teeth.
1) Both abutment teeth had been inclined toward mesially on mesio-distal direction.
2) Both abutment teeth had been inclined toward buccally on bucco-lingual direction. Furthermore, highly correlation (r=0.62) had been showned between both abutment teeth.
3. The total required time for preparation was 1235.3sec.(mean), and driving time of the air turbine occupied about 60%(740.8sec.) of the total required time. The time for the axial surface reduction was the longest of all, and it was occupied about 24%(291.7sec.) of the total required time.

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14 natural dentitioned subjects with no signs of TMJ disorders, aged 19-58, were used in this study. They were divided into three groups according to their occlusal guidance. One is canine guidance group (CG group), the other is group function group (GF group), and the last is group having non-working side contacts (FB group). All subjects were asked to perform maximum biting in 1) intercuspal position (IP), 2) right lateral position (rLP), 3) left lateral position (1LP), 4) retruded position (RP), and 5) protruded position (PP). EMG recordings of right and left masseter, anterior and posterior temporal muscles from pairs of surface electrodes were taken in each occluded position. The results were as follows:
1) Total integrated EMG activity of FB group was approximately equal in any occluded position, whereas that of CG and GF group varied from position to position.
2) EMG patterns in rLP and lLP of CG group were obviously different from those of GF group. Ratio to maximum biting in IP of CG group in rLP and lLP were significantly small, approximately half of GF group.

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Dental Air Turbine sound depends on the mechanical performance such as rotation and it is impossible to neglect connections of the sound with fluid mechanics and acoustics. Turbine sound must be considered from the standpoint of the sound pressure level and frequency component.
In this study, the sound samples was measured and analysed in octave band spectrum. Turbine sound has three resonance bands of the frequency with the rang from 0 to 1, 600Hz and the resonance band increased as air pressure increased.
The frequency of the second resonance band decreased as the cutting load and cutting point diameter increased. Damping of the second resonance band frequency shifted downward by polishing point.

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A cross-linking agent was added to increase the bonding strength of Superbond C & B by improving its cohesiveness. PMMA powder, which was copolymerized with 0.5%(w/w) neopentylglycol dimethacrylate as a cross-linking agent, was used for the preparation of Superbond C & B. The bonding of Superbond C & B to which the cross-linking agent had been added was then examined by the pull-out test using an alloy with different levels of surface roughness prepared by two surface-processing methods (polishing with #600 waterproof abrasive paper or 50μm sandblast processing).
The results were as follows:
1. Superbond C & B had a bonding strength of 205kgf/cm² after polish processing of the alloy with #600 waterproof abrasive paper and 199kgf/cm² after 50μEm sandblast processing. The t-test showed no significant difference between the two types of processing.
2. Superbond C & B to which the cross-linking agent had been added showed a bonding strength of 285kgf/cm² in the material processed with #600 waterproof abrasive paper and 347kgf/cm² in that processed with 50μm sandblast processing.
3. Among various combinations of bonding agents and surface processing methods, the combination of Superbond C & B with the cross-linking agent and 50μm sandblast processing showed the highest values under all conditions.

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The purpose of this study was to develop a new observation method of marginal leakage of complete crowns with ³⁵SO₄⁼ labeled compound. The new point of this method was to use 15% gelatine solution, which was very effective to get clear autoradiograms. Once the labeled tracer penetrated marginal gaps, it didn't move away but stayed there.
Complete crowns actually cemented to abutment teeth were treated using the new method, so that we could observe marginal condition more clearly than with the conventional method using various dyes or usual simple radioisotope.
In this study, we found close relationship between film density of autoradiograms and marginal distance of gaps.

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Cornell Medical Index (CMI), Manifest Anxiety Scale (MAS) and Yatabe-Guilford Character test (Y-G test) were carried out on165dental students in the course of clinical prosthetics to understand the psychological changes after study in this course.
According to the Y-G profile patterns, in male students, the ratio of A, B, C, D, E and F types were 12.6, 6.7, 14.8, 63.0, 2.2 and 0.007%, and in female students, 6.9, 34.5, 17.2, 34.5 and 6.9%respectively.
From the results of CMI, most of the students were stable after study in this course. Psychosomatic profile patterns of CMI before study were similar to those after in both sexes. All items of CMI were decreased in males, but some items were not decreased in females.
Anxiety measured by MAS was decreased in many students but was increased in some students after study in this course.
These results indicate that it is necessary to be concerned with the mental as well as physical well-being in unstable students.

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Using several brands of articulators, the precision involved in the manipulation of them was examined. First of all, the extent of three-dimensional displacement caused in the upper frame was examined when the ‘Inclination of sagittal condyle path’(I. S. C. P.) and the ‘Inclination of sagittal incisal path’(I. S. I. P.) of articulators were adjusted. Secondly, the displacement was measured, which is caused as it was loaded statically to the center of the upper frame. Thirdly, the vertical displacement of the upper frame and cast were measured when the cast is mounted by the plaster.
Following results were obtained. The various displacement occurred between the upper and lower frame during articulator handling. After all, the rigidity or the precision of articulators should be taken into consideration, and the I. S. C. P. should be adjusted to 30° and the I. S. I. P. to 0° as the upper cast was mounted. However, the error due to three-dimensional displacement was found, which was caused by these adjustments after mounting casts. When casts are mounted with high or low ratio of water and powder, the expansion was smaller in the case of high ratio, so the ratio should be taken into consideration. Accordingly, I planned out the ‘Remounting Method’ which is able to use the articulator in high precision.

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Autopolymerizing hard-setting direct relining resin is currently being used in dentistry to attain denture bases that conform to the supporting tissues with a high degree of accuracy. The purpose of this study is to investigate the flow of six commercial hard-setting direct relining resins (Denture Liner, Kooliner, New Truliner, Rebaron, Swift, Tokuso Rebase) and several types of impression materials (zinc oxide-eugenol, polysulfide rubber, silicone rubber) using the parallel plate viscometer. The viscometer is used to measure the spread radius of samples (a volume of 0.5cm³) between two parallel flat plates when a load of 750-gram weight is applied at 1, 10, 60, 100 seconds after loading has begun. In this experiment, the load was applied at 120, 150, 180, 210, 240, 300 seconds after mixing had begun. All the samples were mixed according to the manufacturer's recommendations.
The findings were as follows;
1. The flow of the six commercial hard-setting direct relining resins could be compared with one another by the spread radius at 1 second after loading (r₁) with no relation to time lapse after initiation of the mix.
2. Denture Liner, Kooliner, Rebaron and Swift had the same flow characteristic when r₁ was the same.
3. Polysulfide rubber impression materials had similar flow characteristic to hard-setting direct relining resins.

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The purpose of this study is to investigate the relation between the metal surface texture and bacterial adherence. The surface of Au-Ag-Pd alloy was treated with or without air-powder abrasion. Seven standard strains and two clinical isolates were used. The alloys were mixed with [6-³H]-thimidine labelled bacteria. The radioactivity was measured with a scintilation counter.
Streptococcus sanguis and clinical isolated Bacteroides gingivalis were adhered in a larger amount to the air-powder abraded alloy surface than to nonabraded alloy surface.
These results indicated that careful consideration is needed for application of air-powder abrasive system on metal crown with secondary caries and periodontal disease.

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Recently, the dimethacrylates, such as Bis·EGMA and Triethylene glycol dimethacrylate (Tri·EDMA), have been used increasingly as a base material of composite restorative resins. The mechanical deterioration of these monomer-based resin may cause the unfavorable actions in clinical application.
The purpose of this investigation was to examine the effects of photodeterioration on viscoelastic properties of the base materials (copolymers) for the composite restorative materials and to determine the monomer ratios of copolymers which have a superior light stability. Two lamps of visible light (VL) and ultraviolet (UV) were used for deterioration.
In the case of polyethylene glycol dimethacrylate (Di·EDMA, Tri·EDMA and Tetra·EDMA), the degree of photodeterioration enlarged for UV than for VL and increased markedly according to an increase of repeated number of (-CH₂-CH₂-O-). The addition of Bis·GMA to EDMA improved extremely the light stability. This phenomenon may relate with the amount of benzene ring included in copolymer.
Furthermore, in the case of an experimental composite resin, it was seen that the photodeterioration of the material proceeded from a relatively early stage after polymerization.

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Interrelationships between mandibular bone reduction and morphological features of craniofacial skeleton was fundamentally demonstrated in this study. Forty-nine denture wearers were engaged in this research as edentulous subjects, and categorized into three groups based upon their resorption points on radiographic and cephalometric views.
Cephalometric landmarks and lines after Downs and Ricketts were independently employed in informations of multivariate data base, and the data were analyzed in components and summarized as follows: Ricketts' landmarks were more advisable to prosthetic applications than Downs' anatomical ones. The resorption peaks shifted forward as mandibular reduction increased. Mental regions were shifted “forward-upward” as longitudinal reductions progressed.
Sharp angles and narrow rami were induced by apparently resorption of mandibles.

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Gysi Simplex OU articulator was constructed by modifying Gysi Simplex 1914, and has been used for students' practice of complete denture construction at 18 Japanese dental schools.
Therefore, the mechanism and movement of the articulator should be explained and understood clerly from the educational standpoint of view.
In this study, the movement was analyzed by geometrical drawing after Ishiwara-Suetsugu's simplified method.
The following results were obtained:
1. Sagittal inclination of incisal guidance acted as an important role for location and inclination of lateral axis.
2. Accessory working condylar guide, which is located behind the condyle post, is another important mechanism as one of determinants of the movement.
3. The lateral wall of balancing condylar guide should be forced to touch always the balancing condyle.
4. It was clarified that the movement of Gysi Simplex OU followed the Gysi's axis theory.

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Most of unilateral cleft lip and palate patients are accompanied with cross-bite in minor segment.
The purpose of this study is to investigate the effect of different buccal overlap on the chewing pattern.
Three unilateral cleft lip and palate patients were selected, and 2 different experimental crowns, which were the normal crown with 2mm horizontal overlap and the cross-bite crown with -2mm, were fabricated for each subject.
The mandibular movement of chewing peanuts was recorded with the MKG. Patterns of chewing cycle in the frontal view, namely the normal pattern, the upper crossed, the lower crossed, the reversed, the contra-lateral and the others were counted in number. And also, the time of chewing cycle was analyzed.
The findings were as follows;
1. With the normal crown, the normal patterns were seen more in number, whereas the reversed patterns were seen more with the cross-bite crown.
2. With the normal crown, the value of the lateral component of the chewing cycle was larger than that with the cross-bite crown.
3. With the normal crown, the value of the coefficient of variation in the time of chewing cycle was smaller than that with the cross-bite crown.

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It is well-known that unsuccessful dental implants sometimes give rise to pronounced inflammatory bone resorption of the upper and lower jaw, and that in such cases it is practically much difficult to attain adequate prosthodontic rehabilitation after removal of the implants.
On this study it is completely reported that two patients suffering from implant-induced osteomyelitis could be finely compensated for with the removable partial dentures using telescopic crowns after removal of the implants, and then the results are shortly discussed from the view of pathology, oral surgery and prosthodontics.
In the first case a 52-year-old woman had been suffering from osteomyelitis of the right mandible due to the both bladevent and endodontic-endosseous implant, and in another case a 43-year-old woman had been suffering from osteomyelitis of the right maxilla due to the endosseous subperiosteal implant, and they had borne insufficient mastication on the affected side of the jaws. Several months after removal of the unsuccessful dental implants, they were rehabilitated with the removable partial dentures using telescopic crowns to recover and maintain good functions such as occlusion, mastication, cosmetics and speech, and oral and general health.

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The purpose of this study is to investigate the relationship between gingival discoloration and Ag₂S. Minute granules of dental alloys were embedded in the gingiva during a 5-11 months span, and their histological and colorimetric analyses were undertaken. Results showed the following;
1. Cases of low melting silver alloy, 12% Au-Ag-Pd alloy, and Ni-Cr alloy all resulted in gingival discoloration, but it did not occur during the specified experimental period.
2. Regardless of the size of the granules or time, the electron microanalyser showed no signs of sulfer detection in cases of low melting silver alloy. However, in the case of 12% Au-Ag-Pd alloy, sulfer was detected 5 months later for only those granules having the size of 0.2-0.3μm. No surfer was detected in cases of Ni-Cr alloy.
3. Although no proliferation of inflammatory cells were observed around those areas surrounding the 12% Au-Ag-Pd alloy granules, they appeared in cases of the low melting silver alloy and Ni-Cr alloy.

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To investigate the principle of Periotest measurement, we compared PT-value and the duration of contact between the rod of the Periotest-Instrument and the tooth measured directly in an oral cavity. Then we applied this apparatus to the subjects with normal periodontium and the patients of prosthetic treatment.
The conclusions are as follows:
1. We confirmed that PT-value was calculated from the duration of contact between the rod of the Periotest and the tooth and it showed mainly the dumping effect of the periodontium.
2. There was a close relationship between PT-value and the clinical degree of tooth mobility, especially in the degree of o and 1 of tooth mobility.
3. Periotest was very useful not only for the periodontal treatment but also prosthetic application.

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By applying the heat effect of laser, it was attempted to fuse artificial materials to tooth enamel with laser irradiation for direct bonding tooth restoration. At first the fusing methods of enamel were studied, and then the fused enamel was analized by polarized microscope, contact microradiogram, vickers hardness, electron probe microanalysis and X-ray diffraction. Furthermore the methods of fusing artificial materials to tooth enamel. Through these studies, the following results were obtained.
1. Among the pigments that were placed on the enamel surface, Fe₂O₃- particulatedispersed agents solution was most suitable for the fusion of enamel, and the best irradiation condition was the focused beam of 20J energy (20W×1.0sec.).
2. Fused enamel, which is proved to be composed of not only hydroxyapatite but also α-tricalcium phosphate, is more radiopaoue than non-fused enamel and the birefringence is dissimilar also, but the hardness is the same.
3. It was possible to fuse artificial α-tricalcium phosphate to fused enamel, and the results of the analysis were the same as those mentioned before.

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Interdental dimension discrimination (IDD) ability in 11 patients with implant dentures was compared with that in 10 normal dentate subjects and bridge wearers. Using a 3.0mm diameter wire as a reference, minimum perception difference between reference wire and test wires were measured at first molar region.
In discrimination of thicker wires from reference wire, IDD ability was highest in normal dentate subjects followed by bridge wearers. It was lowest in implant denture wearers.
In discrimination of thinner wires from reference wire. IDD ability was highest in bridge wearers followed by normal dentate subjects. It was lowest in implant denture wearers.
A so-called “directional specificity”, namely, higher IDD ability between thinner wires and reference wire than between thicker wires and reference wire, was recognized in normal dentate subjects and bridge wearers. However, there was no demonstrable directional specificity in implant denture wearers.
On analyzing IDD ability in individual patients of implant denture wearers. IDD of both thicker and thinner wires from reference wire were approximately the same in 3 of the patients as those in normal dentate subjects and bridge wearers. In 7 patients, IDD ability of either thicker or thinner wires from reference wire was lower compared to the two other groups. In remaining patient, IDD of both thicker and thinners wire was impaired.

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The wear properties of Bis·EGMA-Tri·EEDMA based composite resins to an Ag-Pd-Cu-Au alloy examined, using a trial sliding frictional wear testing machine, and the effects of water in a specimen on wearing characteristics were discussed. The water absorbed into the specimens softened the surface of the material and decreased the wear-resistant properties of them. On the other hand, the increase of Bis·EGMA content improved slightly the wear characteristics. In the range of 60-76wt% filler content, the wear of experimental composite resin decreased according to increase of filler content. In the case of 50wt% filler content resins, however, the wear of experimental composite resins was significantly less than in the o ther cases. There was high negative correlation between wear rate and Vicker's hardness of experimental composite resins (r=-0.84). In addition, there was high correlation between wear rate and amout of absorbed water in the specimens of76wt% filler (r=0.92).

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The dispersion of occlusal forces around both the abutment teeth and the alveolar mucosa is generally considered as an most important principal in minimizing the denture mobility and the local over-load on designing the distal extention-type denture. This study was undertaken to investigate the principal factors in designing uni-lateral-type clasp denture equipped with direct and indirect retainer.
Our date show:
1. Guide-plane provides maximam retention power in cooperation with high fixable indirect retainer.
2. Direction of load and design of the denture are the major responsible factors for shifting the horizontal rotation center of denture body. Especially the shape of indirect retainer was demonstrated to alter direction and amount of displacement of the denture base and abutment teeth.
3. Most types of uni-lateral distal extention denture exhibited upward and downward movement when they function in vivo.
4. Negative type indirect retainer plased at incisor was shown to be harmful due to its intrinsic slunting force on teeth to labial direction. On the other hand positive type indirect retainer was considered to be more desirable because the force through clasp moves abutment teeth vertically.

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For purpose of evaluating the characteristic of electromyographic activities of masticatory muscles with front or molar tooth loss, electromyographic activities of masticatory muscles and mandibular movements during tooth tapping and gum chewing were investigated in each group of tooth loss, and were compared with those of control group. The results were as follows.
1. In reference to the group with front tooth loss,
1) On tooth tapping, each S.D. of the time parameters of electromyographic activities of jaw closing muscles especially masseter and posterior temporalis was small, and that of jaw opening muscle was large.
2) On gum chewing, offset of jaw closing muscles' activities especially masseter and anterior temporalis were delayed.
3) On both tooth tapping and gum chewing, there was no difference in mandibular movements from control group.
2. In reference to the group with molar tooth loss,
1) On both tooth tapping and gum chewing, each S.D. of the time parameters of electromyographic activities of jaw closing muscles was large.
2) On tooth tapping, S.D. of opening ratio was large.
3) On gum chewing, both S.D. of chewing cycle and opening ratio were large.

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Today the removable partial dentures are used as permanent prosthetic devices. Thus, their designs must be considered the prevention of breakage or deformation. A metal plate denture consisting of double structure has been designed with the intention of improved mechanical strength and durability.
Principal investigations of this study were to introduce structural design techniques and apply them to denture design, to analyze the double structure using the finite element method, to judge reliability using a statical bending test, to compare the breaking strength of each structure, and to measure movement during function of mandibular extension base removable partial dentures on the simulation model.
The summary of results is shown below:
1. Calculated values and experimental values were a fairly good approximation.
2. The reintorcement and Lightweight method of double structure was mede evident.
3. Regarding the packing resins, METADENT was slightly superior in mechanical strength to ACRON.
4. Maximum stiffness of the double structure was approximately 7-10 times that of skeleton types, and breaking strength was about 9 times.
5. Tensile strain generated at the double structure was statistical less than for skeleton types.
6. When loads of 10kg applied, the difference of distal displacement between double structure and skeleton types was between 70-80μm.
7. The stiffness of the skeleton types decreased remarkably by shortening the denture flanges, but the double structure did not show significant change.

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