Subjecting pure titanium and Ti-6A1-4V alloy to firing under various conditions, the extent of dissolution of their constituent elements was measured using ICP.
1. Even with variation of firing conditions, no remarkable differences were observed in the amount of titanium, aluminium and vanadium element dissolved in each solution in which the metals were immersed.
2. Upon immersion in NaCl solution, human saliva, lactic acid solution or hydrochloric acid, the extent of dissolution of titanium and vanadium element increased in that order. The extent of dissolved of aluminium element increased upon immersion in NaCl solution, lactic acid solution, hydrochloric acid or human saliva, in that order.
3. Although the extent of dissolution of titanium element was small, that observed for vanadium element which are believed to be cytotoxic was comparatively larger.
4. The extent of dissolution of aluminium and vanadium element were greater than that of titanium.

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With the view of elucidating the influence of the stress associated with impression taking on circulatory responses, 9 normal young subjects, 3 patients with gagging reflex, 4 normal aged subjects and 4 hypertensives were measured for blood pressure and pulse using automatic sphygmomanometer. The following results were obtained:
1. Resting blood pressure and pulse were highest and most for hypertensives and patients with gagging reflex, respectively.
2. The fluctuation of circulatory responses in normal young subjects tended to be less influenced by the stimulation of impression taking.
3. The blood pressure of patients with gagging reflex tended to increase remarkably upon taking maxillary impression, but to return to the resting value following impression taking.
4. Circulatory responses of normal aged subjects showed not only great timecourses but also individual differences. Some of them showed remarkable decreases in systolic pressure.
5. The fluctuation of circulatory responses in hypertensives under the control of hypotensive drugs tended to be smaller than that in normal aged subjects.

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Tensile bonding strength to acrylic resin of the tissue conditioning materials were evaluated, at immersed period in distilled water (37°C) of 1 hour, 6 hours, 1 day, 3 days, 2 weeks and 1 month from the start of mix of tissue conditioning materials. In addition, these materials were evaluated at 360, 800, 1, 600 and 2, 600 times in thermal cycle test (4°C to 37°C). The samples of three acrylic tissue conditioning materials were prepared, and a silicone relining material was used as a control.
Ultimate tensile bonding strength of acrylic tissue conditioning materials increased in accordance with a increase of immersed period for 1 hour to 3 days, and its strengths also increased in thermal for 360 to 1, 600. Ultimate tensile bonding strength of silicone material did not change after immersed period of 6 hours and thermal cycles of 800. The tensile stress of acrylic tissue conditioning materials immersed in distilled water was larger than the values obtained for 3 days to 1 month, compared with those for 1 hour to 1 day. The tensile stress of silicone relining material did not change after immersed period of 6 hours and with a increase of thermal cycle.

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Effect of denture removal during night time on histopathological changes in denture supporting tissues was investigated. Experimental denture base was applied to molar region of the hard palate of Wistar rat, and continuous pressure was exerted to the denture supporting tissues through the denture base. The experimental denture was removed during night time from the palate of the denture removal group, whereas the denture was worn continuously day and night in the denture wearing group. The palatal tissue was examined histopathologically up to 7 days after the insertion of the denture.
In the denture wearing group, bone resorption and decrease of the thickness of epithelial tissue and connective tissue were observed. These tissue changes came out early and severe with increasing the continuous pressure. Whereas no remarkable tissue change was observed in the denture removal group throughout the experimental period. From these results, it was revealed that the half a day loading of mechanical continuous pressure to the denture supporting tissues would not cause bone resorption, and was suggested that denture removal during night time was effective for the preservation of denture supporting tissues.

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The adhesiveness between the porcelain and the etched enamel was studied under the various conditions. The porcelain surface was treated with Laminabond porcelain primer or Clapearl bonding agent, then adhered to the etched enamel mediated with Laminabond composite paste or Clapearl DC. The resin thickness was 150 or 400 μm, and the irradiation time was 120s or 240s. The shear bond strengths were measured after one day immersion in 37°C water and after10, 000 thermocycles between 4°C and 60°C.
When resin thickness was 150 μm, the little decrease of the bond strengths after thermocycles was observed. While in the case of 400 μm resin thickness, the high and durable adhesion between the masking porcelain and the etched enamel was obtained with the use of Clapearl bonding agent and Clapearl DC, or with 240 s photo irradiation.
The polymerization of the cemented resin was an important role in the adhesionbetween the porcelain and the etched enamel.

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For evaluation of stomatognathic function it is of great importance to investigate the spatial relationship between the mandibular condyle and the temporal-bone articular fossa (condylar position). The purpose of this study is to analyze the condylar position quantitatively not only at intercuspation but also during jaw movements. A three-dimensional reconstruction of the temporo mandibular joint (TMJ) is made by the corrected lateral tomography, which is coupled with the jaw movement data recorded by a jaw tracking device (MM-JI): and then the condylar movements with six degrees of freedom are described on the graphic terminal.
I examined changes of the bony joint spaces in 8 subjects (16 TMJs) at intercuspation and during sagittal and lateral border moN'rements. The results are as follows:
1. An analysis of the relationship between the position of the condyle and that of the kinematic condylar point (KCP) showed that 1) in case the KCP is located anterosuperior or superior to the condyle, the posterosuperior or the posterior portion of the condyle approaches the eminentia or the fossa in the maximal opening and the hinge movement during the sagittal border movement; and 2) in case the KCP is located medial to the condyle, the posterior portion of the working-side condyle approaches the fossa during the lateral movement.
2. The condylar position at intercuspation had influences on that during jaw movements.

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The purpose of this study is to investigate the irradiation-induced color changes of visible light-cured crown and bridge resins and influence of storing conditions on the color changes of resins.
Tristimulus colorimeter was used for color measurment. Disc specimens mearsuring 5.0 mm in diameter and 1. 5 mm in thickness were prepared with enamel, dentin and cervical color paste of each resin. At first, the color changes immediately after irradiation were measured. Then the specimens were stored in 3TC-controlled distilled water or in air. The color at 3 days, and 1, 2, 3 and 4 weeks after irradiation were measured and compared with the color at immediately after irradiation. Color changes were expressed as L*, a* and b* uniform color space (CIE 1976 L* a* b*color difference formula) and total color difference value (ΔEab*, N BS unit) were calculated.
ΔEab* value of each resin between before and immediately after irradiation was large and the difference was assessed as “noticeable” or “much”. This change was attributable mainly to increase in L* and decrease in b*.
With lapse of time, the resins stored in air underwent slight changes in color. By storing in distilled water, L* and b* were decreased and ΔEab* was assessed as “noticeable” or “much”

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This investigation was made on successive changes of the microvascular architecture of the disk of the temporomandibular joint, produced an experimental malocclusion by the following procedures: All upper posterior teeth were extracted and occlusal surfaces of all lower posterior teeth were cut down in the Japanese monkey. These animals were sacrificed on 4, 8, 16 and 24 weeks, respectively. Acryl plastic was injected via the common carotid arteries utilizing the plastic injection method (Ohta et al., 1990) to prepare microcasts around the TMJ. The injected materials coated with gold were employed for scanning electron microscopy. In a beginning period after the above procedures, the distribution density of blood capillaries has decreased in the posterior portion of the disk but increased somewhat in the anterior portion. These changes have gradually returned to the normal aspect in the later period. It can be said that the occurrence of a posterosuperior compression by a posterior dislocation of the condyle in the beginning period may be followed by the gradual and accommodative restoration of the disk tissue.

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The examination of the laxity of the temporomandibular joint (TMJ) region provides valuable diagnostic findings concerning the functional and pathological changes of the soft tissues of the TMJ. The purpose of this study was non-invasively to estimate the biomechanical properties of the human TMJ region. The biomechanical properties, damper: c, spring: k and mass: m, were analyzed for 28 normal subjects using an automatic system composed of a device for measuring mechanical mobility of the joint and a data analysis unit with a microcomputer.
As the results, following findings were obtained:
1. Using this method, the mechanical properties of the TMJ region could be to estimated noninvasively.
2. The mechanical properties in males were significantly greater than those in females (p<0.05).
3. The coefficient of variation in the mechanical properties of the TMJ varied about 5% both over one day and over one week.
4. Values of c and k were significantly correlated with the range of active and passive mouth openings, protrusive and retrusive movements, and end-feel distance (p<0.05).
5. Parameters of c and k were significantly correlated with the degree of overbite and the ratio of overjet to overbite (p<0.05).

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We investigated functional roles of the superior and inferior heads of the human lateral pterygoid muscle (SUP. LPT and INF. LPT, respectively). In 6 subjects EMG activities were recorded from the both heads of the lateral pterygoid muscle and other masticatory muscles. The movements of the incisor and condyle points and biting force were measured. Three-dimensional structure of the temporomandibular joint (TMJ) was examined in 12 cadavers. The findings are summarized as follows.
(1) Articular disk can rotate around the condyle backward, but not forward, on the axis of the lateral and medial poles of the condyle to which the articular disk is tightly attached.(2) The SUP. LPT was active primarily in the jaw closing phase and the INF. LPT in the jaw opening phase during chewing. The SUP. LPT and INF. LPT showed reciprocal EMG activities in various basic jaw movements.(3) The SUP. LPT showed the stretch reflex but the INF. LPT did not.(4) The SUP. LPT muscle activity increased rapidly at a lower biting force level, whereas the relationship between the biting force and the activity of the masseter and temporalis muscles changed in a manner quite different from that in SUP. LPT.(5) The SUP. LPT maintains a considerable activity level at the rest position and increases its activity during swallowing, chewing and clenching of the teeth.

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We investigated functional roles of the superior and inferior heads of the human lateral pterygoid muscle (SUP. LPT and INF. LPT, respectively). In 6 subjects EMG activities were recorded from the both heads of the lateral pterygoid muscle and other masticatory muscles. The movements of the incisor and condyle points were measured. In stepwise jaw opening and closing movements, the activity of the SUP. LPT was in inverse proportion to the extent of jaw opening. When the jaw performed hinge-like movement without anterior displacement of the condyle, the relationship between the SUP. LPT activity and the extent of jaw opening became linear, in both opening and closing phases. This indicates that the SUP. LPT activity is well correlated with the rotational angle of the mandible, whereas the activity of INF. LPT is proportional to the extent of anterio-posterior displacement of the condyle. The working range of the SUP. LPT was between 0 and 3 mm in anterio-posterior condyle displacement, in all different types of jaw movemnt in the same subject. The INF. LPT started to be active at 3 mm anterior to the posterior-most position. There was no overlap in their working range between the SUP. LPT and INF. LPT, indicating that they act as antagonist.

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The purpose of this study was to investigate the fundamental property and time coordination of the superior head (SLpt) and inferior head (ILpt) of the human lateral pterygoid muscle.
EMGs were recorded and analysed during mastication, together with the condylar and incisal movements in five subjects with normal jaw function. EMG recordings were taken at SLpt, ILpt, the anterior belly of the digastric muscle (Da), the posterior part of the temporal muscle (Tp) and the masseter muscle (Mm).
SLpt appears to have two phasic functions. In the first phase it controls the position and speed of the disk and condyle as it returns posteriorly to centric position. In the second phase, it functions mainly during the final closing phase on the working side to direct the orientation of masticatory forces toward the articular eminence in response to increases in these forces. These functions are completed by the supplementary activity of ILpt.

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I electromyographically elucidated the reflexes of the inferior head of the human lateral pterygoid muscle (Lpt) and compared them with those of the masseter muscle (Mm) and the anterior belley of the digastric muscle (Da). On 5 male subjects, simultaneous unilateral recordings were obtained for each muscle during electric stimulation and mechanical tappings of the chin.
The electric stimulation elicited the inhibitory response in Lpt and Mm during clenching in intercuspal position, while the inhibitory responses could not be observed in Lpt and Da during maintaining active jaw opening position. On the other hand, the mechanical tappings to the chin elicited the excitatory responses in Lpt and Mm. The latency of these responses were not significant difference apt: 8.9±1.9 msec, Mm: 8.7±1.0 msec).
These findings suggest that there is intricate reflex by which the human lateral pterygoid responds to external stimulation for various conditions of voluntary muscle contraction, and that this muscle has a monosynaptic reflex arc originating in its proprioceptive receptors.

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In part 1, we have reported the reduction of thickness in forming and the deformation under static loading in 10 kinds of the sheet type and 4 kinds of the molding type mouthguard materials. In this paper the shock absorptive ability of their materials were investigated by drop-ball test. The steel ball (64.2 g in weight and 25.0 mm in diameter) was dropped on the materials on the steel table from 200 mm height. Shock wave was picked up by an accelerometer and the magnitude of the shock waves were measured by FFT analyzer.
The results were as follows:
1. In the sheet type materials, the thick group showed higher shock absorptive abilities thanthe thin group.
2. In the molding type materials, thick specimen showed higher shock absorptive abilities in each materials. Molteno soft showed the highest and Molteno hard and Elastomer showed the lowest shock absorptive abilities in each thicknesses.
3. With the results of thickness and deformation in part 1, it is suggested that the thin group in the sheet type and less than 3.0 mm of Molteno soft, less than 2.0 mm of Molteno regular, less than 1.0 mm of Molteno hard and Elastomer in the molding type are not suitable for custom-made mouthguar material

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Occlusal diagnosis should be included not only static but also dynamic informations from a patient during function in stomatognathic system. Chewing movements were evaluated on the pathway in areas of intercuspal position utilizing the Sirognathograph Analyzing System II to establish a clinical assessment. Functional directions were objectively studied during opening-closing movements through a newly developed soft ware program which made possible to analyze them in three dimensional planes. Twenty dentate subjects were selected at random from students and staff of Kanagawa Dental College who had no history of stomatognathic dysfunction. Classification of grinding patterns were performed in mastication of a piece of chewing gum for all subjects to obtain an objective assessment of functional directions in chewing movements.
As a result, a newly developed analyzing program contribute to classify the grinding patterns in chewing movements. Application of regression line made also possible to evaluate linear directions. A study of a total 1, 200 chewing cycles and grinding patterns in both sides of all subjects showed that B-W, W-W, N-W patterns were more frequently occured. Average path angles and their standard deviations in chewing movements contribute to a clinical assessment for functional diagnosis.

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The role of saliva and Fibronectin (FN) in the adherence Candida albicans to acrylic resin plate surfaces in vitro were investigated. Precorting Candida albicans with FN reduced adhesion to precorting acrylic resin plates with FN, while precorting Candida albicans with Phosphate-bufferd saline increased adhesion to precorting acrylic resin plates with FN. Precorting resin plates were a significant factor which influenced adhesion of Candida albicans to the resin plate surfaces.
This study suggests that saliva and components of saliva like as FN may play an important role in adhesion of Candida albicans to the acrylic resin surfaces. In order to removedenture plaque, it is an important approach that denture peliclle is removed.

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Recently, the growth of bone induced by electricity has aroused much interest. Applying electrical stimulation to the bone from outside the body produced callus formation. This study is to investigate possibility for dental application of piezoelectric film (Vinylidene Fluoride-Trifluoroethylene copolymers; VDF/TrFE film) as electrical stimulation for the bone repair. The generated electricity of it and electrical Impedance around VDF/TrFE film were meansured in the rat's femur, and calculated the micro-current. The electrode of VDF/Tr FE film was implanted over femur of 5 Wistar strain male rats, and the generated electricity was meansured during activated muscle such as walking or running. On the other hand, applying alternating current to the implanted electrode, the electrical impedance was analyzed by Lissajous figure method and calculated within about 10-100 Hz in frequency. Obtained results as follows:
1. The generated electricity during function were between +1, 531--1, 612 mV.
2. The electrical impedance around the electrods was 9.2-42.9 KΩ between 10-100 Hz in frequency.
3. The micro-current around the film was 3×10^-3 μA during function. From these results, it was suggested that VDF/Tr FE film could be applied to the bone repair as a power unit of electrical stimulator.

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In order to investigate the effect of malocclusion on mandibular movements during speech, the envelope of the mandibular movements during speech were analyzed in 10 normal subjects and 60 subjects with malocclusion. Results were summerized as follows:
1. The most superior point of the envelope was located in the normal occlusion side in the unilateral posteiror malocclusion, and was located inferiorly in the deep overbite and anterior crossbite.
2. The most posterior point and the most inferior point were located posteriorly in the anterior crossbite, and were located superiorly in the edge-to-edge bite.
3. The most anterior point was located anteriorly in the anterior openbite, and was located postero-superiorly in the edge-to-edge bite, and was located postero-inferiorly in the anterior cross-bite.
4. The antero-posterior width and the superio-inferior height were not affected by any malocclusions.
5. The speech envelope was guided by the protrusive path in the normal occlusion and the malocclusion in the posterior teeth, and was guided by both the protrusive and the lateral paths in the deep overbite. The speech envelope was not guided by any paths in the edge-to-edge bite, anterior openbite and anterior crossbite.
It can be concluded that the mandibular movements during speech are characteristically affected by malocclusion.

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The wearers of either a maxillary or a mandibular single denture, which thereby opposes natural dentition, may have even greater problems clinically and neurophysiologically than do those who wear complete dentures or those with natural dentition. This study proposed to investigate how the complex interplay between exteroceptors and proprioceptors is affected by the control of feedback mechanism during mastication in the wearers of either a maxillary or a mandibular single denture. The subjects selected included six well-functioning wearers of a maxillary (G1) and a mandibular single denture (G2). Surface EMGs of bilateral masseter and posterior temporal muscles were recorded simultaneously with the use of the Sirognathograph (SGG) during the mastication of three different types of test foods, chewed on the habitual side. Data were statistically computed by means of analysis of variance.
The results were as follows:
1. The basal seat area in G1 was approximately 1.6 to 1.7 times as large as G2. However, there were no significant differences between G1 and G2 in muscle activity of maximal clench.
2. In the SGG, significant differences between the chewing of hard and soft foods were shown in G2. The occluding phase time and the maximum lateral component of the chewing orbit decreased during the mastication of hard foods.
3. Significant differences between G1 and G2 were seen in the EMG. GI showed a longer the burst duration outlasting tooth contact and greater values in the integrated EMG than G2, especially during the mastication of hard foods.
4. All of the CV values in the EMG parameters were significantly greater in G2 than in Gl. The above results show that different types of feedback might influence the masticatory movement in the wearers of either a maxillary or mandibular single denture. It appears that thereis characteristic feedback behavior in the mandibular single denture, in that, the sensory input from both the denture supporting mucosa and the mechanoreceptors act to control the inhibition of muscle activities.

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This study was designed to investigate the effect of piezoelectric film as irregular current source on the bone regeneration in rats. An electrical current with irregularitis in both amplitude and frequency produced by a sheet of piezoelectric film was used. The subjects included sixty Wistar-strain male rats with an average age of 13 to 15 weeks, which were then randomly divided into 3 test groups. Under general anaesthesia, a hole of 2.0 mm in diameter was drilled in the right femoral diaphysis of each rat in all three groups. In the control group, the hole remained uncovered. In Group A, non-poling VDF/TrFE film (10×5 mm) covered over the hole. In Group B, the hole was covered by piezoelectric film (poling VDF/TrFE film, 10×5 mm), which generated a maximum average voltage of+1, 531-1, 612 mV when the rat moved freely. Time sequence of observation were 1st, 2nd, 3rd and 4th week with Tetracycline and Calcein bone labelling. Microscopic histopathological observations were made under three conditions: noumal light and fluorecent light, and contact microradiograph.
The results were as follows:
1. During first week, the outline of femur had been rapidly repaired to normal in Group A, yet by the later stage the mineralization of the bone in Group A was delayed more than the control group.
2. In Group B, however by the first week, it was observed that the outline of femur had not only been repaired fastest, but the bone had also mineralized more rapidly than the other two groups.
3. By the early stage, cancellous bone and osteoid formation were observed under VDF/TrFE film in Group. B, whereas in the other groups there was a delay in the formation of cancellous bone.
From the above results, it appeared that piezoelectric film behaved nearly as same as the SGP current, and effected bone formation. It can be stated that the poling VDF/TrFE film accelerated new bone formation both gualitatively and quantitatively, and that this film might serve as an effective method for the dental implants as well as it might also be applied for periodontal and/or surgical bone defect.

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Mandibular movements as a whole have not been sufficiently investigated, due to the great difficulty of recording them. In order to clarify those features in three-dimensions, we measured 62 cases whose ages ranged from 20 to 79, and whose dentitions were either complete or nearly so, and whose intercuspal positions were firm. Part 1 of this study revealed the differrent types of sagittal movements seen among various age groups. We then investigated lateral excursions, gaining the following results: 1) no statistical difference could be found in the movement direction at incisor, canine or first molar either on the working or non-working sides, among any of the age groups studied; 2) the inclination of the condylar path tended to lessen with advancing age; 3) the sagittal inclination of the second molar path on the non-working side tended to be gentler in subjects 60 years and older than in younger subjects, which would reflect the previous result, and 4) there was no statistical difference in path-length of the working-side condyle among the various age groups. These results showed that the posterior guidance on the non-working side tended to change with age, even in subjects with nearly-complete dentition, probably due to the morphological changes of the temporomandibular joint.

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We have developed structural designs of three dimensional framework from a usual metal plate.
The framework consisting of double structure was representative of the structural designs, with the intention of improved mechanical strength and durability.
The purpose of this study was to investigate the effect of different structural designs on torsion strength by statical bending test, and to compare torsion stiffness of extension base removable partial denture by loading test on the simulation model.
The results obtained were as follows:
1. Torsion strength of the double structure was approximately 10 times that of skeleton types, and torsion stiffness was about 3 times.
2. When torsion moment was applied, principal strain of the skeleton types increased remarkably, but the double structure did not show significant change.
3. Distal displacement of the double structure increased approximately 20 μm by changing the loading point, but skeleton types increased 80-100 μm.

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