Activity patterns of the masticatory muscles during maximum clenchin at the intercuspal position depend upon occlusal factors such as the number of teeth and premature tooth contacts. Naeije (1989) stated that imbalance of activity patterns, so-called asymmetry index, during submaximal clenching in intercuspal positions can be used to evaluate abnormality of the occlusal contact. However, its physiological mechanism is unknown.
The aim of this study was to investigate the physiological mechanism effecting the masticatory muscle activity by using experimental occlusal interference during brief maximum clenching in the intercuspal position.
Six dental students were selected as subjects with normal occlusion without any symptomatic CMD. Electromyograms from the bilateral masseter and bilateral anterior and posterior temporalis muscles were used.
In addition, two other aspects, occlusal surface contact and mandibular position deviation during brief maximum clenching, were studied.
The experiment was carried out during eleven sessions over a period of 14 days.A gold inlay, containing artificial occlusal interference, was attached for 7 days temporarily. The sessions included immediately after applying occlusal interference, the interference period, and removal of the interference, and subsequent observation of interference effects was carried out.
The following effects were observed: 1) after one and two days following occlusal interference attachment, the temporal EMG pattern was altered significantly, 2) after three days following occlusal interference attachment through removal of the interference, normal patterns of EMG activity gradually recovered and 3) the masseter muscle activity did not significantly effect any changes.
The results indicate that both biomechanical and physiological factors are interdependent in normalizing the mechanism.

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A leaf gauge is a device that can be used to correct the mandibular position. However, a rationale for the treatment of abnormal muscle activities by the use of the leaf gauge is unclear.
The aim of this study was to investigate a rationale for the physiological effect of deprogramming of abnormal jaw masticatory muscle activity after creation of this abnormal activity by the use of experimental occlusal interference during brief maximum clenching in the intercuspal position.
Six normally dentate dental students were selected as the subjects. Surface electromyograms from the bilateral masseter, bilateral anterior and posterior temporalis muscles were used.
In addition, two other aspects, occlusal surface contact and mandibular position deviation during brief maximum clenching, were studied.
Four eleven-session experiments were carried out for a period of 14 days each. The sessions included before and after application of an occlusal interference, the interference period and removal of the interference, and subsequent observation of interference effects was carried out.
The leaf gauge was used during each session with four distinct conditions, which were two leaf gauge thicknesses of 4 mm and 16 mm for each experiment and application of eachleaf gauge for 15 and 10-minute periods.
It was found that separation of posterior teeth occurred one or two days after interference, the application of a leaf gauge in an attempt to correct the imposed abnormality of muscle balance. In addition, it was found that the mandibular position was repositioned the horizontally. The occlusal contact point surface has become larger in order to become normal.
Two factors contributing to the reprogramming of muscle activities were found to be the thickness of the leaf gauge and the length of time of application.

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We studied the effects of the size of colloidal silica in a mixing liquid for phosphatebonded thermal expansion inhibited investment on the surface properties and the reaction layers of pure titanium crowns.
1. Cast crowns were easiest to separate from their molds when 40% large colloidal silica particles were used.
2. The surface roughness of a crown when using large colloidal silica particles was observed half as much as that when using small colloidal silica particles.
3. The surface hardness of crowns showed lower values when large colloidal silica particles were used than when small colloidal silica particles were used.
4. The surface roughness of investment mold showed lower values when large colloidal silica particles were used than when small colloidal silica particles were used.
5. Elemental analysis revealed that there was a Ti-poor reaction layers which contained O, P and Si in the surface of the crown.
Additionally, this analysis showed that the lowest concentration of Si and P was in the surface of crown when 40% large colloidal silica particles were used. These results indicate that the surface properties and the reaction layer of pure titanium crowns made by the titanium casting procedure using phosphate-bonded investment when large colloidal silica particles were used were better than those of small particles.

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The purpose of this histopathological study was to investigate the pulpal reaction to New Panavia (TPN-S) in adult dogs at the intervals of 3, 30 and 90 days after filling.The results were as follows:
TPN-S induced a slight pulpal change, and no reparative dentin was formed on the primary dentin in each experimental case.There was no significant difference in the pulpal response between TPN-S and the zinc oxide-eugenol cement (positive control).Contrarily, the silicate cement (negative control) induced relatively intense damage to the pulp, especially in the 90-day postoperative cases.
No bacterial penetration was observed in the experimental series of TPN-S and the zinc oxideeugenol cement, but bacterial invasion did occur in a few cases of silicate cement 90 days after preparation.
The results of this study suggested that TPN-S showed a very weak reaction to dental pulp.

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Powder-Liquid VLC reline resin REBARON LC has several outstanding features: excellent initial fluidity, minimal deformation during removal, easy manipulation, etc.
The purpose of this study was to investigate the effect on the adhesive strength of REBARON LC to the denture base resin by two different experiments.
Experiment 1: Adhesive strength of five hard direct reline resins to a denture base resin (ACRON) tested in tension and shearing tests.
Experiment 2: Adhesive strength of REBARON LC to five denture base resins tested in tension test.
The following results were obtained:
1. The adhesive strength of five hard direct reline resins showed a similar tendency in both tension and shearing tests.
2. In the adhesive strength of five hard direct reline resins to denture base resin, the adhesive strength of Rebaron was the highest and Koo Liner was the lowest. There were no significant differences among TOKUSO REBASE, TRIAD and REBARON LC.
3. From the observations by SEM, REBARON LC adhered uniformly to denture base resin but TRIAD showed a bonding layer between reline resin and denture base resin.
4. In the adhesive strength of REBARON LC to five denture base resins, the adhesive strength to Palapress was the highest, followed by META-DENT, ACRON MC, ACRON and TRIAD.

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Masticatory muscles perform two functions during clenching, as generating a bite force and maintaining a jaw position. The relationship between these two functions may be changed by the differences of the stability level of the mandibular position and the degree of the bite force.
Therefore, we recorded muscle activities of masseter and anterior temporal muscles on seven healthy male subjects during MVC and 30% MVC in three different stability of mandibular position. A metal frame of central bearing type which was fited in a mouth caused variation of the stability level of the mandibular position.“Activity index” and “asymmetry index” were studied, and the results were as follows:
1. Activity index in MVC was larger than in 30%MVC.
2. Asymmetry index of temporal muscle changed with a stability level of mandibular position in 30% MVC. Temporal muscle could prevent a sliding of the mandibule. This tendency was notfound in MVC.
3. Asymmetry index of the masseter muscle did not change with a different stability levels of mandibular position or degrees of bite force.
In conclusion, the temporal muscle functions as a jaw positioner more than a force generator at a low clenching level. At a high clenching level, the temporal muscle increases its function as a force generator. The masseter muscle functions as a force generator more than a jaw positioner in every degree of clenching.

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To elucidate the relationship between tongue motor behavior and masticatory function, the motor skills of tongue and masticatory efficiencies of 30 young dentate, 10 old dentate and 20 complete denture wearers, whose dentures were developed by the author using the same methods and materials, were tested.The motor skill of the tongue was evaluated by using an ultrasound system and physiologic signal unit connected to a heart sound microphon to select a series of sound signals, and the masticatory function was evaluated by a sieving method using the particle size distribution of masticated peanuts.
The results were as follows:
1.The tongue motor skill was decreased in the old group as compared with the young group statistically (p>0.01).
2.The masticatory efficiency in the old dentate group was decreased as compared with the young dentate group statistically (p>0.01).
3.There was no statistical correlation coefficiency between age and masticatory efficiency in the old dentate group at a 0.05 level.
4.The correlation coefficiency was 0.60 between age and masticatory efficiency in the complete denture wearers group, which was statistically significant at a 0.01 level.
5.There was no statistical correlation coefficiency between tongue motor skill and masticatory efficiency in young and old dentate groups at a 0.05 level.
6.The correlation coefficiency was 0.75 between tongue motor skill and masticatory efficiency in the complete denture wearer group, which was statistically significant at a 0.01 level.

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The purpose of this study was to observe the effects of Candida albicans on the morphology of subepithelial blood vessels in the denture bearing mucosa of the palate.Denture stomatitis was experimentally produced on the palate of Japanese rabbits to observe the morphological changes of the capillaries caused by C. albicans. Furthermore, with the aid of a modified oral biomicroscope, histopathological and microbiological changes of the palatal mucosa were also observed, and the results were as follows:
1.The morphological characteristics of the capillaries appeared quite complex due to stimulation by C.albicans, and it was found to remain the same even after C. albicans were removed.
2.The degree of inflammation was found to progressively worsen after further stimulation by C. albicans, and sudden changes in the morphological shapes of the capillaries were also observed.

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The purpose of this study was to measure the improvement of the adhesive strength between resins and Ag-Pd-Cu-Au surface-treatment alloy by the flame spraying method.
The shear bond strength of Ag-Pd-Cu-Au alloy was increased when a flame spraying treatment was applied to its surface. We compared the use of retention beads with that ofthe resin materials by using the spraying method.
Superior bond strength spraying materials were sought, and analysis was carriedout.
The results were as follows:
1. The most suitable spraying distance was between 15 cm and 25 cm.
2. The adhesive strength of Ni-Cr-Al-Mo spraying materials had the highest value among the marketed spraying materials.
3. In several trial cases Al powder was added to the Co-Cr alloy powder fused with Ag-Pd-Cu-Au alloy, becoming an improved spraying material with increased adhesive strength.
4. The most suitable quantity of Al powder for dental adhesive Co-Cr alloy powder was 30 wt%.
5. Examination of the Co-Cr (30 Al included) powder sprayed surface showed that Al (45 wt%) was the most frequently applied material.
6. The retention beads had a mechanical retention only. However, Co-Cr (30 Al included) powder by flame spraying treatment was judged to be a good chemical adhesive.

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The pressure sensitive foil “Prescale”(Fuji Photo Film Co., Ltd.) shows coloration depending on pressure when loaded. Occlusal force measurement using conventional “Dental Prescale 30 H” had failed due to its limited range of pressure measurement. Recently a new type of foil, “Dental Prescale 50 H”, was designed for measuring the wide range of occlusal pressure (5-420 MPa). The purpose of this study was to evaluate its reliability for occlusal force measurement. Experiments were carried out both on a normal dentate female (19 yrs.) and on her casts. The casts were mounted on a calibrating device at the centric occlusion. The load was applied to each of the lower teeth via the opposing upper teeth. The applied load was 10 to 100 N at premolars and 50 to 400 N at molars. The linear relationship was observed between the applied and the measured load irrespective of the teeth (r = 0.989). The calculated occlusal force during maximum voluntary clenching of the subject was 8 to 60 N at premolars and 63 to 330 N at molars. These results indicate that the “Dental Prescale 50 H” had a sufficient range for measuring the occlusal force at the tooth arch during clenching.

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In this study, we used a standardized video recording system to observe the teeth and gingiva which were exposed to view during functional lip movements. These observations are thought to offer valuable information for selecting appropriate types and designs of crowns. For this study, 116 volunteers were chosen, and the following results were obtained.(1) The labiocervical margin design of the upper anterior crowns is of significant importance because most people expose the gingival tissues.(2) The labiocervical margin design of the upper premolar and the lower anterior crowns should be selected for each patient because some people expose the gingival tissues thereof.(3) The lower premolars should be restored with a full veneer type restoration. A metal collar for the labiocervial margin form would be acceptable because few people expose the gingival tissues thereof.

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The object of this study was analyze mathematically the effect of condylar inclination of the nonworking-side condyle path on the tooth path.
Conclusions of the calculation are;
1. Error of the tooth path was proportinate to and smaller than that of condylar inclination of the nonworking-side condyle path.
2. The relation of errors between condylar inclination of the nonworking-side condyle path and tooth path was hardly affected, even when the direction of condyle movement and the inclination of the sagittal incisal path was altered.
3. Amount of error of the nonworking-side molar path was generally equivalent to a half amount of the condylar inclination of the nonworking-side condyle path, while that of the workingside molar path was a sixth thereof.

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With the aim of evaluating training and improving the ability to distinguish colors necessary for developing an esthetical prosthetic appliance, 20 dental students of our university were subjected to color discrimination tests to evaluate their ability, and the following results were obtained.
1. The ability to distinguish red, yellow, green and purple colors was judged to be fair in 19 (95%) students and excellent in one (5%) student.
2. When the results were analyzed by sex, males showed the highest ability for distinguishing red colors, followed by green, yellow and purple colors; the ability to distinguish purple colors was particularly low. In females, the corresponding order was red, green, purple and yellow, and their ability to distinguish red colors was at the same level as that for green colors, and their ability to distinguish purple colors was at the same level as that for yellow colors.
3. In all subjects, the ability to distinguish red and green colors was relatively high, while that for yellow and purple colors was relatively low.

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The purpose of this study was to investigate whether prolonged irradiation, post-curing and surface hardening treatment effectively control the alteration of the color tone of visible light-cured crown and bridge resins.
Three commercially available resins were used in this study. The resins were prepared under five conditions; namely, irradiated for standard time, irradiated for three times the standard time, post-curing (100°C for 15 minutes) after irradiated, and surface hardening treatment after irradiated. The resins were immersed in distilled water of 37°C for 12 weeks.
The color tones of the resins were determined colorimetrically by referring to the L*a*b* color chart, and the difference Δ Eab*in color tone was calculated in units of NBS.
The prolongation of irradiation had no effect on preservation of the original color tone. The post-curing and surface hardening treatment effected all resins; the surface hardening treatment had the greater effect.

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The aim of this study was to investigate the radiopacity of composite core materials.
Radiopacity of composite core materials, filling materials and base cements were measured by densitometer. The elemental analysis of fillers were made by using an electron probe microanalyzer, and the filler substances were identified by a powder X-ray diffractometer.
Radiopacity of composite core materials, except for some resin materials, showed low radiopacity. Silicate glass or crystal silica was found in all fillers. Zr or Yb was identified in some fillers, and Ba ions were detected in the glass fillers. Composite resin core material including Zr showed the highest radiopacity.
These results suggest that the filler including Zr ion would be preferable for increasing the radiopacity of composite resin.

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In the fabrication of wrought wire clasps, the electric resistance soldering procedure was adopted to conect clasp arms to rests.This procedure surpasses in mechanical properties of clasp arms and strength of soldered parts as compared with other soldering procedures.The purpose of this study was to investigate the influence of heating duration by using this procedure.
Two kinds of specimens, circular arm type and straight arm type, were prepared.A clasp arm was soldered to a piece cast with Co-Cr alloy. The heating duration was set to 0, 2, 4, 6, 8 and 10 seconds.Distances between clasp tips, load required for 0.1mm deflection of clasp arms, permanent deformation after 0.5mm deflection thereof and tensile strength of soldered parts were measured.
The results were as follows:
1.As the heating duration increased, the distance between clasp tips increased.
2.Load required for 0.1mm deflection showed almost the same value in every heating duration.
3.Permanent deformation showed the lowest value at a duration of 4 seconds (1.73V).
4.Tensile strength showed a constant value (63-69kgf) regardless of the heating duration.
These results indicated that the heating duration should be within 4 seconds to obtain the best mechanical properties and to avoid deformation of clasp arms.

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n order to investigate the effect of the occlusal form on the lateral force transmitted to a tooth during mastication, the buccolingual forces were measured as the moment occurring around the center of tooth rotation.The four following types of occlusal form were adopted: the basic form (type B), the form in which the outer half of the functional cusp was partially eliminated (type OF), and the forms in which the buccal or lingual cusp was totally eliminated from the type B (type FC or type NC).These types had no occlusal contact at the intercuspal position and lateral excursion.Buccal and lingual moments were measured by load cells which were contained in a bridge at the missing lower first molar.
The results obtained were as follows:
1.The buccal moment was observed more frequently than the lingual moment.
2.The interocclusal space, at which the moments occurred, decreased according to the progress of mastication.And the moments were observed near the intercuspal position.
3.Differences were observed in the frequency and the intenstiy of the moments among subjective foods.
4.The lingual moment was larger and the buccal moment was smaller in the type OF than in the type B.
5.The buccal moment was smaller in the type FC than in the type B.However, little difference was observed between the lingual moments of these two types.

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The retainer with a framework is an important device for excellent function of the removable partial denture.However, prosthetic appliance fracture primarily occurs at the terminal abutment-cantilever junction.
In this study, combinations of five structural designs (double structure consisting of six columns, or four columns, T-shapes, trusses and rectangular columns) and three retainer designs (full coverage, 4/5 coverage and mesiodistal rest) were subjected to the statical bending test. The fracture resistance of these frameworks were evaluated to measure maximum stiffness, yield load and strain of the retainer.
The obtained results were as follows:
1.Maximum stiffness of the double structure consisting of six columns, trusses and T-shapes was approximately 10 times greater than that of rectangular columns.
2. Ultimate strength of double structure consisting of six columns was the greatest, followed by that of four columns, trusses and T-shapes.
3.Fracture resistance of full coverage and 4/5 coverage was about 4 times greater than that of mesiodistal rest.
4.When 20 kgf load was applied, the strain of the marginal and occlusal regions tended to increase according to the strength of the framework, whereas that of the proximal region decreased.

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Vowel sounds spoken by patients having maxillary defects were compared and evaluated with a digital signal processor that was capable of automatically recognizing the formant frequencies of Japanese vowels before and after wearing a maxillary prosthesis.
The automatic recognition rate for formant frequencies for this system was 91.6%, and immediate recordings and analyses of sound waveforms were recorded on floppy discs.
Results showed that a sexual difference of formant frequency existed among normal subjects, but no age difference for those over 20 years of age was shown. Patients having maxillary defects showed the vowel sounds for /i/, /u/, and /e/ to be located mostly outside the normal equiprobability ellipsoid. The F 1 value for patients having maxillary defects tended to increase slightly for /i/ and increase as well as decrease for /e/. Vowel sounds /a/, /u/, and /o/ remained within the normal range. On the otherhand, the F 2 value tended to increase for /a/, /u/ and /o/, and decrease for /i/and /e/ for patients having maxillary defects.
In conclusion, compared to H 1 type maxillary defects, H 3 and H 4 type showed most vowel sounds to be located outside the normal equiprobability ellipsoid. However, the vowel sounds were found to be within the normal range when the patients wore their dentures.

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