A remarkable gingival pigmentation around the restorated teeth was successfully treated by simple surgical removal; incision & coagulasion of deposits by electrosurgery. Before the treatment, a biopsy from the pigmented gingiva was histopathologically examined, and a lot of small pigment deposits were found in the lamina propria with no inflammation, but not in the epitherium. Elements constructing the deposits were also determined by means of an electron probe X-ray microanalyser. Silver was found to be the principal element of the deposits, but not found at all in the crown metal. These results suggested that the cause of the pigmentation was implantation of metal fragments from metal cores during abutment teeth preparation. Therefore, the surgical removal was performed. Relapses have not occured for 3 years since the treatment.

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The purpose of this study was to investigate the effect of the height of remained coronal tooth structure on the retention of post and core. This study was directed to detect micro-separation after application of intermittent compressive force using India ink. 130 extracted human teeth were prepared for samples, and complete cast gold crowns were cemented with zinc-phosphate cement on the two types of post and core; composite resin core with steel post, cast core and dowel.
Conclusions were as follows:
1. Application of force to the crown on the tooth which lost coronal structure caused micro-separation between the tooth and the core.
2. The height of remained intact coronal tooth structure was effective to increase in the retention of post and core.

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A highly skilled surgical technic is an important factor for the success of implant. But the heat generation during bone preparation will greatly affect the healing process of bone and prognosis of implant.
In this study, the heat occurence and distribution during bone preparation which performed on an in vitro mandible model (ribs of pig) were considered with the aid of a real-time thermography.
IMZ implant drills and bur, designed for cylindrical type implant were used for the bone preparation.
The conclusion are as follows:
1. Any drill or bur generates higher heat without water irrigation.
2. Heat distribution produced different shape of range according to different type of drills.
3. On a relationship of preparating time to heat generation, spiral drill takes the longest time to complete drilling but heat rising ratio is slow. Round bur and Canon drill take short time to complete drilling but it is accompanied with rapid heat rising.

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Hydroxyapatite (HAP) tooth root substitute implantation have been applied to extraction sockets in many studies for purpose of preservating alveolar bone. Dimensional changes were measured with sectioned study cast of cephalometric X-ray photo.
In this study, dimensional changes were determined by newly developed evaluation system which utilizing image analyzer (Immunomedica Co., Ltd.), in a view of conserving alveolar ridges beneath the denture base. Cone shaped HAP tooth roots (5 or 6mm in length) were implanted to one subject and disk-like shaped HAP tooth roots (2mm in length) were also implanted to the other subject.
Preservation of alveolar bone was observed in both shaped HAP tooth roots implanted site compared to control site. Bony ankylosis between HAP tooth root and alveolar bone, observed on 1 month after histological specimens, may contribute to this result. Smaller changes of blood flow compared to controls were obtained on implanted site, which were measured with Laser Doppler blood flow meter (Perimed KB; Sweden) on buccal mucosa. We consider that HAP shows good biocompatibility and HAP tooth roots implantation decrease the wound volume consequently.

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Distal extention denture has intrinsic characteristics of cantilever and inevitably rotates around abutment tooth due to the difference of force transmissive characteristics between abutment tooth and alveolar mucosa. This study was undertaken to figure out the possible forms of advanced unilateral clasp denture and the principle to design them in the co-operation of direct and indirect retainer, and telescope retainer.
The results were as follows;
1. Splinting of abutment resulted in much more efficient dispersion of load and in reduction displacement of abutment and denture base.
2. Generally the distal extention denture without indirect retainer exhibited considerable amount of displacement of abutment and denture base. Therefore this type of denture could not be an option upon designing unilateral denture.
3. Adequate organization of splinting of abutment, guide plane, and retainer with millinged abutment on clasp design denture was shown to improve retaining power as high as that of telescopic design denture.
4. Telescopic design denture with multiple abutment was much more preferable than that with single abutment. The amount of displacement of abutment and denture base could be greatly reduced by addition of positive-type indirect retainer to telescopic design denture with multiple abutment.

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The chrome-cobalt alloys containing titanium (Dentitan) has excellent porcelainto-metal bond strength. Therefore, it is used as outer telescope crown alloys of cone telescope denture in actual clinic.
The purpose of this study is to investigate the fitness and the change of metal before or after porcelain firing of chrome-cobalt alloys containing titanium.
The results of this investigation indicate that (1) chrome-cobalt alloys containing titanium can be used as metal for inner crown because it showed the same degree of fitness compared with precious metal, and (2) the optimal water/powder ratio of the outer telescope crown was 28ml; 2ml, or 27ml; 3ml, and (3) although the full porcelain-veneer-coverage was greater vertical distortion than the partial-veneer-coverage, either metal can be applied to outer crown by adjusting of the retention.

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In order to measure the pressure distribution on supporting structures under complete denture, we used impedance grid pressure sensor and examined its accuracy and availability.
The results were as follows:
1. The sensitivity of this sensor was high when the distance between electrodes was short.
2. This sensor showed large change in output voltage and high sensitivity in the case of soft elastic materials.
3. This sensor showed the high linearlity between output voltage and applied load.
4. This sensor showed hysteresis loop under cycle load.
5. Base line of this sensor that has the urethane rubber as elastic material was changed when the load was applied intermittently.
We measured the pressure distribution over supporting bones under upper complete denture by using simulator of maxillary edentulous with this impedance grid pressure sensor. We could observe the pressure distribution and pressure region in detail and visually when the load was applied to the both occlusal tables evenly.

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An EMG computer analysis system was developed to analyze the mandibular function. The system enabled measurements of the masticatory muscle's rhythm, activity, and power spectrum for the same EMG burst during mastication. This study revealed that a power spectrum analysis was able to be carried out by a fast Fourier transform algorithm of the isometric contraction components of EMG bursts during mastication.
The normal regulatory mechanism of the mandibular function was temporarily disturbed by clenching to inflict fatigue upon the masticatory muscles. EMG analysis of the masticatory muscles during gum chewing were observed before and immediately after clenching, and during their recovery periods. After fatigue induction, all of the masticatory rhythms of the masticatory muscles showed a decrease in EMG burst duration time (duration) and duration per cycle (D/C) that recovered with time. However, only the coefficient variation of the duration and D/C in the working side increased immediately after fatigue induction.
The power spectrum shifted to a lower frequency immediately after fatigue induction, and recovered along with time. Furthermore, it was found that EMG activity influenced the power spectrum during gum chewing.
In conclusion, this EMG analysis system may be used as a possible future diagnostic aid for mandibular dysfunction syndromes.

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It was examined, in this study, whether the tannin-fluoride preparation (HY preparation), which might have a caries-reductive, plaque inhibiting and astringent action, could reduce the incidence of gingival inflammation around abutment teeth for removable partial dentures. Zinc oxide eugenol cement mixed with HY preparation filled in the cavity prepared in the resin base facing the abutment tooth. Crevicular fluid (Periotron unit: GCF), gingival index (GI), plaque index (P1I), probing depth and caries activity around the abutment tooth were measured during 12 months. The following results were obtained:
1. GCF decreased at 1 month later and showed low values at 2, 3, 6 and 12 months.
2. The percentage of low GI value showed an increasing tendency during the experimental period.
3. There was slight variation in P1I and probing depth during the experimental period.
4. Caries activity showed a decreasing tendency.
These results indicate that the tannin-fluoride preparation reduces not only caries activity but also gingival inflammation around abutment tooth.

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Although the prognoses of the adhesive bridges are practically satisfactory, some disconnections have been reported. Physical bite, twisting and tearing forces areconsidered to be the causes for these disconnections. Paired natural human teeth; 2 incisal and 2 molar teeth, were embedded in cold cured resin for fatigue test and axial reduction was slightly performed. Cast bridges which were designed to come to 30mm² in every abutment and to resemble clinical design, were made from two kinds of metal; Ni-Cr alloy and Ag-Pd-Au alloy, and adhered with teeth by Panavia EX (Kurarey Co. Ltd.). Incisal bridges were disconnected easier than molar bridges in the fatigue test. There was no significant difference between 2 kinds of metal. With stereoscopic microscope, cohesive fracture of resin was observed on the region which was farthest from supporting point of fatigue force in incisal bridges. Dimple patterns characteristically in fatigue fracture were also observed in some cases. In modified tensile test of incisal teeth using Ni-Cr alloy, force point was given far 1mm &12mm apart from approximal surface, and various twisting and tearing forces were loaded in 12mm cases. The cases loaded by higher twisting and tearing forces had significantly smaller bond strength.

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A transducer for the measurement of torque transmitted to abutment teeth of removable partial dentures was newly developed.
The transducer was composed of a right cylinder (12.0 mm×3.5 mmφ) made of phosphor bronze as the torsion bar, to the surface of which two strain gauges (KFC-2-D2-11, KYOWA) are adhered symmetrically about the axis of the bar. Torque transmitted to the transducer was detected and evaluated as tensile strain and compressive strain on the torsion bar surface by means of strain gauges.
The transducer was small enough to be easily applied to removable partial dentures for the measurement of torque transmitted to crowns of abutment teeth, and showed satisfactory precision (The instrumental error in measurement was within 3%).
In the present study, the newly developed transducer was revealed to be useful for the measurement of torque transmitted to crowns of abutment teeth by removable partial dentures.

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The sagittal incisal jaw movement during swallowing saliva was measured on 11 subjects (range: 24-30 years old) with “normal occlusion” by using a two-dimensional system applied infrared sensor.
The duration of swallowing saliva and that of tooth contact were calculated with the program developed in our laboratory.
The results obtained were as follows:
1. The average of the duration of swallowing saliva (T1) was approx. 3.5 sec on 11 subjects.
2. The average of the duration of tooth contact during swallowing saliva (T2) was approx. 2.1 sec on 11 subjects. Type Ia had the longest T2 (approx. 2.5 sec) among the types of tooth contact.
3. Type Ia had a greater ratio T2/T1 (74.4%) than those of the other types.
In conclusion, it was clearly shown that the subject of type Ia had a longer duration of tooth contact during swallowing saliva than those of the other types in the absolute and relative values.

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The purpose of this paper is to investigate the motor unit activities of the human masseter muscle during sustained the bite force at a constant level. The electrical activities recorded with surface and inserted electrodes were studied, with the following results.
1. The masseter muscle had the changes of activities in two phases as a contraction progressed.
2. In the first phase, surface EMG activities decreased and discharge frequency of motor units also decreased.
3. In the second phase, surface EMG activities increased and discharge frequency of motor units also increased.
4. In the first phase, it was suggested that the bite force was maintained by an increase in the twitch tension produced by a motor unit and that there were no recruitment of additional motor units.
5. In the second phase, it was indicated that the bite force was maintained by the recruitment of new motor units and an increase in the discharge frequency of motor units to compensate a loss of force resulted from the contractile element fatigue.

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The ordinary denture movement during function is defined as the“Denture dynamics”in R. P. D.'s. by K. H. Körber (1975). The Author has already reported the evaluating method of the denture dynamics objectively by two ways;
The displacement sensors of magnetoresistors detected the vertical and horizontal movements of denture saddle in free-end situation. Tiny accerelometer also detected the accerelation during the movements.
In this present study, the correlations among the retainers used, the extent of the denture dynamics in displacement and accerelation, the occluding force and the abutment tooth mobility induced by the denture support were correlatively evaluated in two patients with class I freeend R. P. D.'s. with interchangeable retainers by above methods. All the data were collected simultaneously by the electronic measuring and recording apparatus.
Following results were obtained;
1. The denture dynamics depended on the selection of retainers examined. The extent of the dynamics reduced from the denture with the wrought wire clasps, the denture with the cast clasps, then to the denture with cone-crown telescopes in sequence.
2. The occluding force increased just as the changes in sequence of the denture dynamics.
3. The abutment tooth moved to the distal in each case. The highest value of the mobility was found in the denture with the cast clasps, then in the denture with the wrought wire clasps. The least value of the tooth mobility was found in the denture with the cone-crown telescopes.
These results will strongly support the concept of the free-end saddle R. P. D.'s. anchored and supported rigidly by the abutments and the residual ridges in clinics.

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The objective of this study was to clarify some of the dimensional change patterns of the denture base of the complete denture following polymerization. Dimensional changes of three polymerization method types were compared. The complete dentures were measured by using the three dimensional measurement system.
The results obtained were summarized as follows.
1. Dimensional changes from the original model immediately after polymerization of complete upper and lower dentures were recorded and all three polymerization methods produced shrinkage on all three axes toward the center. Heat-cured resin samples and microwave-cured resin samples showed the same shrinkage with pour-type resin samples only showing 1/2 that amount.
2. The gradual dimensional changes occuring after polymerization up until 4 weeks werealso recorded. The heat-cured resin samples showed no additional changes but remained in its shrunken state. The pour-type resin samples began to enlarge until almost all of them reached the original model size within 4 weeks. The microwave-cured resin samples began to enlarge but only slightly and then soon stopped changing.
3. All polymerization method types showed more dimensional change in the lower plate than in the upper plate.

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The ability of hardness discrimination in 11 implant denture wearers was compared with those in 10 bridge wearers and 11 normal dentate subjects.
The hardness discrimination was tested using silicone rubber blocks having rubber hardness that ranged at intervals of 10° from 30° to 70°. Using a rubber block with rubber hardness of 50°as a standard, the ability of discriminating rubber blocks of different hardness was examined.
All the three groups examined had excellent ability of discriminating the rubber blocks of rubber hardness of 30° and 70° from the standard block. The ability to discriminate the rubber block of rubber hardness of 40° from the standard block was only slightly lower than but almost the same as the ability of discriminating the hardness of 30° and 70° in all the three groups. However, the ability of discriminating the rubber block of rubber hardness of 60° from the standard block was significantly lower in the implant denture wearers, compared to the normal dentate subjects and bridge wearers.

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Eleven healthy participants were made to perform isometric horizontal jaw movements with maximum volantary efforts in various postures. Surface EMGs from the laterocervical, nucha, shoulder and back regions were bilaterally picked up, and simultaneously recorded with jaw force.
The results obtained were as follows:
1. Electromyographic power value in these regions depended on the directions of the jaw exercises (posteriorly pull> posterolaterally pull> anteriorly push anterolaterally push, P<0.0001).
2. The directional effects mentioned above were significantly obvious in the inferior laterocervical (Electrode No.2) and back Electrode No.5) regions (P<0.0001).
3. The postural effects on the power value were varied with the directions of the jaw exercises (P≈0.03); i.e., the highest value during jaw pull was observed in an upright position, while that during jaw push was found in a supine position.
4. From above results, it would be considered that occlusal habits with sustained isometric jaw retrusion might have higher probability to provoke the discomfortableness in the neck, shoulder and back regions than those with protrusion, and that the habits with the retrusion might be more injurious in a supine than in an upright position, while those with the protrusion more injurious in an upright position.

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The penetration by bacteria through dentinal tubules was studied using a device that included portion of bovine anterior teeth. Strains of 4 genera, Streptococcus mutans, Lactobacillus casei, Staphylococcus aureus and Escherichia coli, were used for the experiment, and the effects of acid etching of dentin on the penetration of bacteria through the dentin was examined. The time required for penetration through dentinal tubules of acid-etched samples was shorter than that of unetched samples. The minimum time required for half the samples to become positive for bacterial penetration through dentin MPT₅₀ was 4 hours for all strains chosen when the acid-etched dentin was the target.
In non-acid etched samples, the MPT₅₀ varied among the genera and ranged fom 20 hours to 48 hours; the speed of penetration was Sta. aureus=L. casei> Str. mutans> E. coli.
Observation under the scanning electron microscope indicated that the smeared layer was completely coated on the surface of the prepared cavity, and when bacterial penetration acurred, a portion of the smear layer on the dentin disappeared.
In longitudinal sections, the penetration by the bacteria into the tubules was visible. From these results, it is suggested that the smeared layer have an important effects on bacterial penetration through these tubules.

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Stress analysis of bridge abutment teeth having cemented dowels was conducted using a two-dimensional finite element method.
The results obtained are as follows:
1. In fixed-fixed bridges, compressive stress was found concentrated within the dowel, on the mesial side of the dowel apex, and in the distocervical part of the crown.
2. In cantilever bridges, tensile stress was found concentrated in the disto-occlusal and mesiocervical parts of the crown, and along the mesial sides of the root and the dowel. Compressive stress was concentrated in the distocervical part of the crown, along the distal sides of the root and dowel, and on the mesial side of the dowel apex.
3. In comparison with fixed-fixed bridges, stresses were significantly greater in cantilever bridges in the abutment teeth, the dowel, and crown margins.
4. In both fixed and cantilever bridges, stresses increased in relation to the length of the span. The rate of increase was less, however, in fixed-fixed than cantilever bridges.

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The materials for porcelain fusing used in this study were nickel-chromium alloy and ceramco opaque porcelain. The opaque porcelain was fused on the metal surface firing in routine method and in H₂. And, the shearing test, X-ray diffraction and quantative analysis of O₂ were done.
The strengths of the specimens firing in H2 were larger than those of ones firing in routine method. We found that SnO₂ of porcelain changed into Sn after firing in H₂.

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In order to evaluate the effect of titanium diameter on reinforcement of titaniumhydroxyapatite implant and calculate the diameter of the implant under loading, stress analysis was performed using the finite element method. In finite element model, 100% or 70% of root length was supported by PMMA in place of bone and the implant was loaded 15 kgf at 45° of the implant axis.
The results were obtained as follows,
1. In the case of 100% support, the titanium diameter had little effect on the reinforcement of the implant, whereas in the case of 70% support, it had much effect.
2. The diameter of this implant was calculated to be more than 3.7mm under loading.
From these results and the view point of manufacturing techniques, the diameter of this implant was supposed to need 4.0mm and that of titanium was to be 2.0mm.

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Tooth tapping frequency was measured in young (21-29 years) and elderly (61-67 years) subjects. They were asked to continue the maximal frequent tapping during 1 min., and their mandibular movement were measured with a Mandibular Kinesiograph.
The results are as follows:
1. Each phase of closing, occluding, opening and cycle was prolonged at the terminal of the 1 min. tapping. That is, tapping frequency decreased. Young subjects had 4.6 Hz tapping frequency and 2.7 Hz for elderly subjects.
2. Although the opening phase per cycle and the closing were not changed in spite of the tapping continuity, the occluding one increased at the terminal of the 1 min. tapping.
3. No difference existed between the young subjects and elderly in the maximal velocity of the mandibular movement at the opening and closing. Opening velocity was larger than closing velocity at the young subjects.

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A previous study suggested that denture plaque played an etiologic role in denture stomatitis. In daily practice, it is important to instruct denture wearers about denture plaque control. In this study, the major areas of investigation were the degree of denture stomatitis and denture plaque, denture hygiene habits, wearing habits and age of present denture.
643 patients wearing dentures (1981-1988) were selected, from 47 to 91 years old.
The following results were obtained.
1. About 50 percent of the 643 patients used brush for cleaning their dentures. The number of people wearing dentures during sleep was fewer than those who preferred removal of dentures during sleep.
2. Soaking dentures in denture cleanser reduced the degree of denture stomatitis and denture plaque.
3. The patients wearing dentures during sleep showed much more occurrence of denture stomatitis than those who had not that habit.
4. Denture stomatitis occured frequently with increasing the age of the present denture.The present results indicate that the occurrence of denture stomatitis is closely related to the quality of the maintenance of denture.

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The purpose of this study was to investigate the influence of tongue brushing on the change of oral Candida species. Among the tongue brushing programs for 50 days, 5 subjects wearing dentures were measured the number of Candida species at tongue, denture and denture bearing mucosa and in oral rinsing.
The following results were obtained.
1. After the tongue brushing program, the number of Candida species at tongue and in oral rinsing decreased significantly.
2. The tongue brushing with denture plaque control decreased in number of Candida species at denture more effectively than without denture plaque control.
3. The number of Candida species at denture bearing mucosa decreased by tongue brushing.
4. It seemed that the tongue brushing was effective to prevent denture stomatitis caused by denture plaque.

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At the coronal cervix, the so-called uncleaned area, the path of the food bolus and its rubbing effect are said to be regulated by the coronal and gingival contours.
However, it has not been ascertained whether such regulation really exists. So, the force which was generated by a food bolus rubbing on the buccal surface was measured at the height of the cervical third of the lower first molar with a load cell inserted into the denture.
The results obtained were as follows:
1. Cervixward forces were observed in the closing phase and cuspward forces, in the opening phase during mastication. The intensity of cervixward forces was stronger than that of the cuspward ones. And the occurrence of the former was more frequent than that of the latter.
2. The intensity and frequency of cervixward forces differed according to the kind of food.
3. Cervixward force under the degree of convexity of 0 mm was stronger in intensity and more frequent than that under the degree of convexity of 0.5 mm.
4. Cervixward force under the marginal gingiva thickness of 1 mm was stronger in intensity and more frequent than that under the marginal gingiva thickness of 2 mm.

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