Pressures exerted by the oral soft tissue which surrounds a denture have a great influence upon the location of the dunture border, the shape of the flange and the arrangement of artificial teeth.
The amount of pressures has been measured by electrical methods in prosthodontics, orthodontics and in other fields of dentistry. However, it is difficult to study the direction of the pressure and those reports are few. In this type of study, it is necessary not only to measure the amount of the pressure but also to record the direction with respect to the oral tissue involved in dynamic movements.
To record the direction of the pressure, we developed a new transducer having three different dimensional outputs with respect to the X, Y and Z axes.
From the result of standardized controlled experiment, it could be concluded that this transducer has sufficient quality to be used in the oral cavity as well as recording the direction of the pressure.

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The diagnostic significance of the endoscopic examination of the cystic lesions of the jaw was evaluated in relation to the X-ray findings and pathological diagnosis. In 89 cases the cystic lesions were as follows: 21 radicular cysts, 11 dentigerous cysts, 18 primordial cysts, 16 odontogenic keratocysts, 2 calcifying odontogenic cysts, 8 so-called fissural cysts and 13 ameloblastomas. These lesions were examined by endoscopy, double contrast X-ray examination and punch biopsy.
A strong correlation was observed between the endoscopic findings of the colour and capillaries of the cyst wall and the histopathological findings of the inflammatory changes and the patterns of the capillaries beneath the epithelium. Definite pathological diagnosis was obtained by punch biopsy in 71.2 percent. This percentage was a little lower than that obtained with the surgical specimens.
These results suggest that endoscopy, double contrast X-ray examination and punch biopsy are useful methods for the differential diagnosis of the cystic lesions of the jaw.

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The object of the present study was to establish a method of numerical expression for radiographic findings. It was attempted to digitize the shape of the lesions in the radiographs of two oral diseases, dentigerous cysts and ameloblastomas. The lesion of the dentigerous cyst is radiographically characterized by a unilocular and smooth margin and, in contrast, the lesion of the ameloblastoma by a multilocular and scalloping margin. The outlines of the lesions in the pantomograms were digitaized by an image analyzer using the opening method and expressed by the particle indices. The following results were obtained. First, the particle indices of the typical cases of dentigerous cysts ranged from 0.0 to 0.3. Second, the indices of the typical cases of ameloblastoma ranged from 1.0 to 4.0. Third, the indices ranged from 0.0 to 0.3 for the cases of ameloblastoma of which radiographs show oval-shaped or circular lesions. Thus, a correlation was satisfactory between the particle indices and the radiographic findings of the lesions. The results suggest that the particle index is clinically useful as a numerical expression of the shape of the lesion in the radiograph.

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The distribution of certain basement membrane (BM) components was examined using indirect immunofluorescence and autoradiography during the facial development in rat embryos. At the onset of the nasal placode, fibronectin, laminin, type IV collagen and BM proteoglycan were found to be present especially at the epithelial-mesenchymal interface (BM) of the nasal placode, although the BM of the presumptive nasal placode was stained and labeled weakly in earlier stages. In later stages when the nasal processes had been formed, the strongly stained and labeled area of those four BM components was limited to the BM in the apical parts of the nasal processes.
The incorporation of³H-thymidine was also examined to clarify the relation between the mesenchymal cell proliferation and the changes in the distribution of the BM components during the invagination of the nasal placode and the development of the nasal processes. Many labeled cells were detected in the region of condensed mesenchymal cells beneath the nasal placode. At the advanced stages, labeled cells were much more decreased in the basal area of the invaginating nasal pit compared to the apical regions of the nasal processes.
The changes, which were observed in the distribution pattern of the BM components and in the rate of the mesenchymal cell proliferation during the facial development, appear to be closely associated with the regulation of the morphogenetic change in tissue form.

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Fifteen occlusal supporting patterns were obtained from the variation of four occlusal metal stops set up on the mandibular bilateral first premolars and the second molars. Displacements of the mandible during maximal clenching was measured using the non-contact two-dimensional sensors in all of the supporting patterns. The masticatory muscle activity was recorded simultaneously by means of bipolar surface electrodes on five subjects. The posterior tilt of the mandible was found in the case of four stops and three stops not set up on the unilateral premolar. The non-supporting side of the mandible shifted superiorly in the case of three stops not set up on the unilateral molar and two stops set up unilaterally. As two stops set up on the bilateral premolars were present, the posterior tilt of the mandible was found. However, the mandible hardly tilted in the case of two stops set up on the bilateral molars. The anterior tilt of the mandible was recognized in the case of one stop set up on the unilateral molar. It was found that, depending on the subject, the non-supporting side shifted superiorly in the case of one stop set up on the unilateral premolar. As the number of the occlusal stops decreased, the total EMG activity of the anterior temporal and masseter muscles on both sides became reduced.

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A quantitative analysis of electromyographic activity from the masticatory muscles was performed when the position of working-side guidance was altered. Without increasing the vertical dimension of the natural dentition, artificial steep occlusal guidances made of Ni-Cr alloy and methacrylic resin were at random overlaid on the maxillary canines, second premolars and second molars. While a mandibular lateral excursion with occlusion of voluntary medium force was carried out on each of the guidances, the EMG activity in the superficial masseter and posterior temporal muscles was recorded bilaterally by means of bipolar surface electrodes.
During the excursion on the second molar, both the EMG activity and total EMG activity of all muscles tested were greater than on the canine. According to the ratio of each muscle activity to the total EMG activity, the working-side muscles were responsible for the results, and depending on the case, the masseter muscles showed more activity than the temporal muscles and vice versa. These phenomena appeared especially in the closing phase.

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We developed 4-META (4-methacryloxyethyltrimellitate anhydride) as an adhesive monomer. Then we prepared an adhesive heat-curing denture base resin using 4-META. In order to develop a more easily and widely usable system we prepared an adhesive self-curing denture base resin. It consists of 4-META containing bonding liner, MMA as a liquid component and PMMA as a powder component. It has good adhesion to the various dental metals. The tensile adhesive strength of this new resin system is 100-150 kg/cm²to the sandbrasted metals such as Co-Cr alloy, Sus 304 and silver alloys even after 1, 000-time thermal cycling test. The tensile adhesive strength to the Co-Cr alloy is also 130 kg/cm²after the 180-day water immersion test. The bonding test of the flat plate, which is a resin-adhered Sus 304 plate, shows reinforcement effect of this resin system even after the 300-time thermal cycling test. Therefore it is expected to be very useful when we prepare a new metal denture or when we repair a broken denture.

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Characteristics of the motor units recorded from the orbicularis oris muscle in 7 subjects were studied during voluntary closure of the lips. The activity of the single motor unit of the orbicularis oris inferior muscle were recorded with bipolar silver ball electrodes improved for this study and the force generated by the lip-closure was simultaneously recorded with a high sensitive sensor. The results obtained were as follows : (1) The contraction time of the motor unit, which was measured by the spike-triggered averaging method, varied from 9 to 59 ms. About 98% of the motor units studied had a contraction time of less than 55 ms, which would be classified as a fast twitch motor unit. (2) The motor unit which had a larger twitch tension tended to have a longer contraction time than that of the small-twitch tensioning units. Increasing the force gradually, a few motor units were recruited orderly and the firing rate of each separate unit increased progressively. These findings suggest that the control of the muscle force caused by the lip-closure might depend on the rate moduration of motor units rather than on the orderly recruitment fashion of the motor unit. (3) The motor units tended to be highly f atigable, as judged by both the spike amplitude and the duration during continuous lip-closing.

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The purpose of this study was to examine the relationship between the composition and the viscoelastic properties of temporary soft lining materials. The viscoelastic properties were evaluated by the creep characteristics using the Voigt 4-element model.
The findings were as follows:
1. The molecular weight of the powder (PEMA) had a significant effect on the retarded elasticity (E₂, η₂) and the viscous flow (η₃) . These 3 moduli showed a positive correlation with the molecular weight. But, the molecular weight had little effect on the instantaneous elasticity (E₁) . The higher the molecular weight was, the greater was the increasing tendency of the value of η₃with the ageing time.
2. The particle size of the powder affected only the instantaneous elasticity (E₁) . This modulus showed a negative correlation with the particle size.
3. The difference in the plasticizer in the liquid had a significant effect on all moduli. The values of the material using BPBG were larger than those of the material using BB.
4. The amount of the plasticizer in the liquid had a significant effect on all moduli. However, the amount of the plasticizer did not affect the changes in the values with the ageing time.
5. The amount of ethanol in the liquid affected the values of all moduli at 8 hours after mixing. The material with a large amount of ethanol showed low values. The material with a large amount of ethanol showed a higher increasing tendency in the values with the ageing time.

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What kind of a role does the snout sensory input play in the feeding activity in animals? In order to obtain the neuroanatomical information on this question, the following study was conducted on 21 dd mice including 3 young mice, 14 young Wistar rats and 6 adult Japanese shrew moles.
The animals were subjected to unilateral and bilateral infraorbital nerve transection. Transganglionic degeneration was studied by the Nauta method and electron microscopy which included non-HRP and HRP application to the neck muscles.
Transganglionic degeneration was found in every experimental case. In the mouse, it spread from the brain stem to the upper part of the thoracic spinal cord. At the obex level, transganglionically degenerated fibers appeared dorsal to the cuneate nucleus on each side and then descended to the posterior funiculi of the cervical spinal cord. The degenerated fibers entered the posterior and anterior horns at each segment and reached as far as the level of the first thoracic spinal cord. Synaptic boutons of the transganglionically degenerated axons terminated in the motor nerve cells. In the rat, the degeneration pattern resembled that of the mouse in the brain stem but not at the spinal cord level.
Under electron microscopy, in the three species of animals, at the various levels of the cervical spinal cord, transganglionically degenerated axons and axo-dendritic and axo-axonic synapses were discovered in the posterior horn and besides these two synapse types the axo-somatic synapses were also found bilaterally in the anterior horn.

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Color observation plays an important role in the diagnosis of lesions of the oral mucosa. But the diagnosis of color change without any yardstick would allow only subjective evaluation. Therefore, standard color chips for the oral mucosa were devised after the Munsell color system. Normal oral mucosa, leukoplakia and carcinoma were examined by visual color matching, applying these color chips.
The color of the normal oral mucosa ranged from 5 R to 7.5 YR in hue, from 3.5 to 6 in value and from 2 to 6 in chroma.
As for leukoplakia, the color distribution was from 10 P to 5 Y in hue, 3 to 9 in value and 1 to 10 in chroma. The color of the leukoplakia was contrasted with its histopathological findings. The greater the thickness of the epithelium was and the rougher the surface was, the greater was the value of the white patches, the lesions being bright white. In the cases with redness, epithelial atrophy, ulceration and dilatation or proliferation of the blood vessels were observed. Leukoplakia, which showed mild epithelial dysplasia, had bright white patches. But in the cases of severe epithelial dysplasia, the value of the color was decreased, and the lesions appeared rather grayish. Red patches with high chroma were always found in these cases.
The color of the oral carcinoma ranged from 10 RP to 5 Y in hue, 3 to 8 in value and 1 to 12 in chroma. Compared with the normal mucosa, the range of the color distribution was considerably broader in leukoplakia and carcinoma.

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Recording the mandibular movement of young children has been one of the difficult work in pedodontics. This is mainly because the recording equipment used so far are too much of a burden on the children to provide sufficient cooperation which the researchers require. A specially designed pedodontic mandibular movement recorder (PMMR) is presented in this paper, which three-dimensionally detects the position detectors fixed perpendicular to the sagittal and frontal planes. The PMMR has the following advantages: 1) The light position detector used is small, light in weight and of high accuracy. 2) By means of simple adaptors the light position detector can be fixed stereotaxically to the skull with little change, which may be caused by the movement of the children's head during the jaw movement. Thus, the data obtained by the PMMR are highly reproducible and easily normalized. 3) Because of the small size and light weight, the PMMR does not restrain the subjects' head movement during the measurement and makes the children cooperative by decreasing the burden on them both physically and mentally.
At the same time, it makes it easier for the clinician to examine the mandibular movement of the children at chair-side. These advantages demonstrate the PMMR as an equipment suitable for recording the various types of mandibular movement in the young children, including the border movement and the masticatory movement.

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The relationship between the depth estimation on the radiogram and the actual depth of the carious penetration was studied in the subsurface proximal carious lesions. Extracted human premolars with 54 subsurface lesions were radiographed with Kodak Ultraspeed (DF 57) . The radiolucency caused by the caries was examined and the mesio-distal depth of the recognized radiolucency was measured with the aid of a magnifying lens (magnification, 10: 1) . The teeth were embedded in epoxy resin after the bucco-lingual width of the lesions was measured and macrophotographs of the continuously reduced surface were prepared to measure the actual mesio-distal depth of the lesions. On the radiograms 76% of the enamel caries and 90% of the dentin caries were recognized. The estimation of the depth on the radiogram was found to be less than the actual depth. It is concluded that the radiographic diagnosis of the caries is not reliable when the actual depth of the lesion is less than 0.5 mm and that the closer to the dentino-enamel junction the caries is located the greater is the underestimation.

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The stability of the complete denture during mastication and deglutition are known to depend on the occlusion. Presently, bilateral balanced occlusion is believed to be one of the ideal types of occlusion for the complete denture. However, there have been some criticisms against it, based on the discrepancy found between the occlusion on an articulator and actual occlusal contacts during the oral function.
In this study, occlusal contacts during mastication were studied in order to re-clarify which type of occlusion is the best for complete dentures.
Three patients were asked to wear an upper complete denture and a lower bilateral distal exten-sion partial denture, constructed specially to suit for the experimental design. This allowed the occlusal patterns to be exchanged the molar region into bilateral balanced occlusion, lingualized occlusion and disclusion. Occlusal contacts both on the chewing side and on the nonchewing side in the premolar and molar region were studied.
The results are as follows;
1. The initial occlusal contacts occurred approximately at the same time in the bilateral balanced occlusion and in the lingualized occlusion, but occurred earlier than in the disclusion.
2. The occlusal contacts, occurred in the following order : molar region of the nonchewing side, the premolar region of the nonchewing side, the premolar region of the chewing side and the molar region of the chewing side.
3. From these results, we could expect dentures to be depressed on the chewing side and be elevated on the nonchewing side. Also rotational movements of dentures around the masticatory center will be created.
In order to avoid these movements we believe that distal balancing contact is necessary for the occlusion of complete denture.

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The enzyme-linked immunoadsorbent assay (ELISA) is as specific and sensitive as the radioimmunoassay without the radioactive materials. The author developed the ELISA method for the determination of the bovine amelogenin over the range of 5500 ng, using the rabbit antibody against the protein. It was found that the antibody cross-reacted with the bovine enamelin only weakly and also with the porcine, murine and rat enamel proteins. The proteins in the other tissues or fluids did not cross-react with the antibody.
Utilizing this ELISA procedure, the increase and decrease in the amount of enamel protein were determined during the process of the development of the murine molar germs.

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For safe dental amalgams selenium-incorporated amalgams were developed and evaluated for cytotoxicity, mutagenicity and micronucleus-inducibility by comparing with the conventional amalgam.
(1) A conventional silver-tin spherical alloy or alloy containing 0.05, 0.1 and 0.2wt% of selenium was triturated with mercury and formed into pieces of 3.2 mm in diameter and 1.8mm in thickness. Fourteen to 24 pieces were immersed in Eagle's minimum essential medium for 72 hours. The amalgam-immersed medium was mixed with the same volume of culture medium, supplemented with 10% calf serum, to which the Chinese hamster V79 cells were exposed for 24 hours. Almost all of the cells were seriously damaged by the conventional amalgam. All of the selenium-incorporated amalgams allowed a favorable proliferation of the cells without deterioration.
(2) In the mutagenicity test the mixtures of the amalgam-immersed medium (5 to 19 pieces/ml) and the fourfold volume of the culture medium were administered to the cells for 3 hours. The mutation frequency of the cultures treated with the conventional amalgam was sixfold to sixteenfold higher than the control. That of the cultures treated with the selenium-incorporated amalgam (selenium, 0.1wt%) was significantly lower than that of the cultures treated with the conventional amalgam.
(3) The frequency of micronucleus formation in the bone marrow erythrocytes of the mice administered with the conventional amalgam at 9.50 and 12.5mg/kg body weight was respectively 3.90±0.85 and 11.5±1.29‰, showing a significant increase over the control of 2.88±0.48‰. The frequency in the mice administered with the selenium-incorporated amalgam (selenium, 0.1wt%) at 12.5mg/kg body weight was 3.75±1.19‰, showing no significant increase over the control.
(4) By the simultaneous administration of the conventional amalgam and Na₂SeO₃·5H₂O respectively at 12.5 and 7.1mg/kg body weight, the frequency of the micronucleus formation was decreased markedly to 5.50±1.47‰. Selenite counteracted the conventional amalgam in regared to the micronucleus formation.
It was clarified that the selenium-incorporated amalgams could be used as safe amalgams in which neither the cytotoxicity nor the micronucleus-inducibility was observed and mutagenicity was reduced in comparison with the conventional amalgam.

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In order to obtain neuroanatomical evidences as to how the interception of the sensory input affects the masticatory system, the unilateral or bilateral transection of the infraorbital nerve was made on the Japanese shrew-moles and rats. The animals were sacrificed postoperatively for electron microscopy at intervals of 14 to 450 days. The masseter and temporal muscles, trigeminal ganglion with the proximal and distal stumps and the brain stem with the upper cervical cord segments were examined electron microscopically.
The results obtained are summarized as follows:
1. The preganglionic and postganglionic parts of the trigeminal nerve showed definitely degenerated changes, that is, the degenerated fibers disappeared completely in the former but the majority of the degenerated fibers were retained as debris in the latter. The ganglion cells underwent typical chromatolysis with lipidosis.
2. In the trigeminal spinal tract nucleus, many of the transganglionically degenerated synapses were in contact with the degenerated dendrites of the secondary neurons. There were also degenerated sencondary neuron soma (lipidosis) .
3. The alpha motor end-plates and muscle spindles of the masticatory muscles showed definitely degenerated features.
From the results obtained it can be emphasized that the snout sensory input plays a great role in the performance of the masticatory activities in the animals.

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One hundred cases of materials for operation, diagnosed as Squamous cell carcinoma of the mandibular gingiva, were examined for bone invasion. According to the mode of the bone invasion, all of the cases were histologically classified into two groups : 1) invasive type (20%) and 2) expansive type (80%) . The invasive type of carcinomas were found to have a diffuse irregular margin, while the expansive type of carcinomas had a well-defined borderline.
The pathological changes during bone resorption were compared in both types of carcinomas. Histologically, in the invasive type of carcinomas, a large number of Howship's lacunae in the resorption phase were observed. In the expansive type of carcinomas, Howship's lacunae in the formation phase, with reversal lines, were relatively marked. Scanning electron microscopic observation of the invasive type of carcinomas revealed a marked destruction of the bone surface, with Howship's lacunae in the resorption phase and in the expansive type of carcinomas a smooth bone surface, with Howship's lacunae in the formation phase, was observed. Radiologically, the invasive type of carcinomas showed an irregular margin with a moth-eaten-like appearance, while the expansive type of carcinomas showed a smooth margin.
These results suggested that the invasive type of carcinomas had a higher tendency to grow rapidly and aggressively compared with the expansive type of carcinomas.

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