Nihon Hotetsu Shika Gakkai Zasshi
Online ISSN : 1883-177X
Print ISSN : 0389-5386
ISSN-L : 0389-5386
Volume 40, Issue 1
Displaying 1-23 of 23 articles from this issue
  • Yoshinori Kobayashi, Toshihiko Matsumoto, Keiichi Ishigami, Toshihiro ...
    1996 Volume 40 Issue 1 Pages 1-23
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    In order to verify the relation between the body function and occlusion, the gravity function, electronystagmography, and auditory brainstem response of TMD patients, edentulous patients and healthy subjects with 500 μm thick experimental occlusal interference were analyzed, and it was confirmed that occlusal problems impede the auditory system, body's posture adjusting system and vestibule system. Further, when the relation between the occlusal contact and the bodily motor function were compared between healthy subjects and patients whose occlusion had been treated, it was confirmed that there was close relation between the two.Furthermore, from the analysis of human body phenomena of healthy subjects with 100 μm thick experimental occlusal interference, it was confirmed that occlusal problems induced bruxism or continuously aggravated the problem and eventually entailed TMD, as well as changed the function of the autonomic nervous system and provoked emotional stress and sleep disorders.
    From these results, it was verified that occlusal problems affected the function of the middle ear transmission system, equilibrium sense, auditory brainstem response, function of autonomic nervous system, emotion and sleep and that the occlusal function was closely related to the bodily motor function.
    Download PDF (13893K)
  • Keiichi Ishigami, Atsushi Chiba, Kenichi Ohki, Satoshi Yokota, Tomotak ...
    1996 Volume 40 Issue 1 Pages 24-28
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    The conventional high-strength tooth crown resins have problems in terms of attrition resistance and abrasion resistance. Conquest ®, which was developed to improve these problems, recently came onto the market and has been used in generalclinical practice. Therefore, Conquest® with Dental Color ® and Thermoresin LC II, commercially available conventional high strength resins, were compared in terms of the following basic physical properties: compressive strength, compressive yield strength, transverse strength, elastic modulus, transverse deflection, knoop hardness, and brush abrasion ratio.The transverse strength of Conquest® was about three-fold greater than that of Thermoresin LC II. Its elastic modulus was also about 3.6-fold greater than that of Thermoresin LC II. However, thetransverse deflection of Conquest ® was less than that of Dental Color ® or Thermoresin LC II. Its brush abrasion ratio was lower than that of the other two types of resin.
    Download PDF (799K)
  • Kyuichi Niikura, Daichi Arai, Yasuhiko Baba, Shinichi Ito, Toshiaki Ha ...
    1996 Volume 40 Issue 1 Pages 29-39
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    In recent years, engineering plastics have been used as materials for denture bases, which have been formed by the injection or compression molding method. The results of evalution of these dentures worn intraorally have been published.
    In this report, we focused on the method whereby polysulfone was preformed to ashape suiting denture base fabrication (Ube Industries Ltd.); polysulfone dentures, constructed by using a systematic method called UB Denture System, were placed in the mouths of 21 patients; and their clinical courses were followed. The findings of these observations are presented.
    Download PDF (10493K)
  • Observations of Extracted Implants and in vitro Bacterial Adherence Assay
    Tetsuo Ichikawa, Katsuhiko Hirota, Hideo Kanitani, Rudi Wigianto, Naek ...
    1996 Volume 40 Issue 1 Pages 40-45
    Published: February 01, 1996
    Released on J-STAGE: November 26, 2010
    JOURNAL FREE ACCESS
    Hydroxyapatite (HA) is a strong bonding bioactive implant material for “biointegration” of an apatite implant to bone. It is reported that the period of bone healing after HA implantation is shorter than that after titanium implantation, and the HA implant can be applied in case of low bone density. On the other hand, it is said that the marginal bone is absorbed rapidly when periimplantitis of HA occurs. There is little information about the interaction between the HA and oral bacteria in spite of the large number of studies that have been done on the implant-bone/cell interface. The purpose of this study was to clarifyperiimplantitis of HA implants from the standpoint of microbiology.
    Firstly, failure dHA implants (Apaceram®2-Piece Implant type S, Pentax), which were brought to our hospital, were used as samples and the surface of the implants were examined by a scanning electron microscope (SEM). The HA surface was rough and most plaque formations were located on the neck of the implant, and few were on the bottom of the implant. The plaque consisted of cocci and rods, including slight filamentous bacteria. Few spirochetes were observed.
    Secondly, the initial adherence of Streptococcus constellatus ATCC 27823T to dHA and titanium alloy (Ti) in vitro was investigated. Bacterial cells attached to dHA were about twiceas many as those attached to Ti. The adherence to saliva-treated (ST)-Ti was about 20% higher than that to nontreated (NT)-Ti. The adherence to ST-dHA was notdifferent from that to NT-dHA. As the duration for acid-treatment to HA reached about 20 sec, the adherence to HA increased rapidly, leveling off at 16%.
    Download PDF (4131K)
  • Hidenori Ohmichi
    1996 Volume 40 Issue 1 Pages 46-58
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    This study was conducted to estimate the biting force in the occluding phase during tapping movements in complete denture wearers.
    The calculation of the biting force during isometric contractions of masticatory muscles has been reported in relation to actual force and masticatory muscular activities. The system was developed to quantify masticatory muscular activities during the occluding phase using the mandibular kinesiograph (K 6- I Diagnostic System) and electromyograph (Polygraph).
    In this study, the subjects were ten complete denture wearers treated at Tsurumi University Dental Hospital. Scatter diagrams were obtainedfrom masticatory muscular activities and biting force in each subject using thissystem. Two curvilinear regression were calculated by the power curve and quadratic curve of the scatter diagram. These calculated values of the biting force were compared with conventional curvilinear regression test and known actual values.
    The results were as follows.
    1. The biting force could be extracted and quantified in the occluding phase during tapping movement. 2. By comparing with this calculation method with that of conventional curvilinear regression, theerrors in the value of biting force obtained by the power curve and the quadratic curve were significantly smaller than those obtained by conventional curvilinear regression (p>0.05).
    Download PDF (7046K)
  • Atsushi Ito, Seiichi Ohsawa, Shoji Kohno, Shingo Iwakata, Kazumasa Kat ...
    1996 Volume 40 Issue 1 Pages 59-64
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    The purpose of this study was to clarify the change of abutment teeth mobility by insertion of partial dentures for a short period.
    Twenty patients who received partial dentures at the Dental Clinic of Niigata University School of Dentistry, between August and November 1994, were selected.
    To evaluate changes in tooth mobility, the Periotest (PT) value of 49 abutment teeth within 3 months after initial insertion were measured and the following factors were analyzed.
    1. change in PT value of all abutment teeth
    2. change in PT value of upper abutment teeth
    3. change in PT value of lower abutment teeth
    4. the relationship between the type of edentulous space, the type of clasp and the amount of PT value change
    The results were as follows:
    1. PT value of all abutment teeth decreased after insertion of the dentures.
    2. PT value of upper abutment teeth showed no significant change within 3 months after initial insertion of the dentures.
    3. PT value of lower abutment teeth decreased from 2 weeks after insertion, and these decreases were clearly detected in free-end dentures.
    4. PT value of lower abutment teeth of free-end dentures decreased irrespective of the type of the clasp.
    Download PDF (1651K)
  • Toshihiko Yajima
    1996 Volume 40 Issue 1 Pages 65-76
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    This study was designed to examine the transmissible phase of an impulse throughthe proximal contact point of two neighboring teeth according to changes in the level of intimacy at the contact point.
    The experiment was carried out by a dynamic measurement of models, in which two natural teeth were fixed at three degrees of contact to simulate an increase in the periodontal ligament space or alveolar bone resorption, and the resulting data were analyzed by the fast Fouriertransformation method.
    The results were as follows
    1. As for the distribution of the spectrum of an impulse, which was caused on the two neighboring teeth and the power of the spectrum, the similarity of the vibrations that were picked up simultaneously on the tapped tooth and on its neighboring tooth was lessened as the intimacy of the contact point was decreased.
    2. The two teeth showed the same peak frequency at any level of intimacy of the contact point, and the peak frequency dropped as the intimacy was weakened until the teeth ceased tocontact each other.
    These data suggested that an impulse was transmitted by a tooth to its neighboring tooth through their proximal contact point and that its frequency was influenced by the level of intimacy at the proximal contact point.
    Download PDF (2325K)
  • Nobuhiro Okuya, Naoyuki Shinohara, Hirotada Kajihara, Akihiko Kadokawa ...
    1996 Volume 40 Issue 1 Pages 77-82
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    The effects of resin-bonded bridge design parameters (adhesive area, shape and metal frame thickness) on the bonding strength of the resin-bonded bridge were investigated by using the adhesion test when the resin-bonded bridge of the upper anteriors was designed as a prerequisite. The adhesion test was performed using a universal testing machine to test the bond strength and toughness of specimensmade with a metal frame bonded to an abutment metal mold.
    The results were as follows:
    1. Maximum bonding force (bf) increased as the metal frame thickness (tm) increased. The values of the maximum bonding force were 10-13 kgf for tm 0.5 mm, 34-46 kgf for tm 1.0 mm, and 68-84 kgf for tm=1.5 mm.
    2. Maximum bonding strength, in which bf was divided by the adhesive area, increased as the adhesive area increased.
    3. The durability of the resin-bonded bridge was discussed by comparing the toughness. The toughness increased as the metal frame thickness (tm) increased. The values of toughness were 4-13 kgf · mm for tm= 0.5 mm, 10-31 kgf · mm for tm= 1.0 mm, and 20-44 kgf · mm for tm =1.5mm.
    4. In order to increase the durability of the resin-bonded bridge, the proposed design conditions were the metal frame thickness (tm) should be as large as possible and the large adhesive area and/or additional groove and wing form among the design parameters should be especially effective.
    Download PDF (1224K)
  • Part 2. Setting Characteristics of Light-Curing Luting Materials
    Naoyuki Shinohara, Yoko Takamatsu, Noriko Kamimura, Akihiko Kadokawa, ...
    1996 Volume 40 Issue 1 Pages 83-89
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    On the assumption that porcelain laminate veneer crown had been bonded to the abutment tooth with the light-curing luting material, setting characteristics of four light-curing luting materials were evaluated for linear shrinkage from the start of exposing, water absorption, Vicker's hardness and compressive strength after exposing the materials to visible light.
    The results were as follows:
    1. The light-curing luting materials rapidly shrank as soon as exposed to light passing through a cover glass or a plate made of porcelain. When exposed to light through the laminate veneer plate, the shrinkage of materials was less thanthat of materials exposed to light through a cover glass. The result suggested that the curing process was delayed because of a shade effect of the laminate veneer plate.
    2. The compressive strength was shown to have a tendency to increase with the elapse of time. The compressive strength of luting materials storedin air at 37°C was larger than that of materials immersed in distilled waterat 37°C, and such a tendency was remarkable from 1 to 4 weeks after exposing.
    3. The values of Vicker's hardness of light-curing luting materials were almost the same from 1 to 4 weeks after exposing, and the hardness values of the materials in air at 37°C was larger than those of materials immersed in distilled water at 37°C.
    4. The amounts of water absorption (wt%) increased rapidly after the luting materials were immersed in distilled water at 37°C, but were hardly increased 8 weeks after exposing the materials to visible light.
    Download PDF (1363K)
  • Part 1. Fitness Accuracy and Surface Roughness
    Tadashi Onizuka, Kenichi Suenaga, Atsuo Nakashima, Noriko Kamimura, Ta ...
    1996 Volume 40 Issue 1 Pages 90-96
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    Sintered metal restorations, made from powder metallurgy developed by Degussa Co., Ltd., and conventional cast restorations were prepared by using a metal modelfor MOD inlay. A comparative study was carried out, and the results were as follows:
    1. As for surface roughness, no significant difference of Rz could be observed both on the polished surface and cavity floor. In the graphs of Rz on the cavity floor, the picture was rough for cast restorations and sink hole-like gas cavities were locally recognized on the surface of sintered metal restorations with a roughness of 3 μm on average. As the results of the corrosion test, roughness of the polished surface of both restorations rose and the increase was larger in cast restorations. Sintered restorations showed better corrosion resistance.
    2. The fitness test showed no significant difference in the margin, butthe fitness of sintered metal restorations was inferior to cast restorations on the inner surface.
    3. The surface hardness of sintered metal restorations was lower than the values indicated by the manufacturer.
    Based on these results, it was considered that powder metallurgy was not suitable for the preparationof a thick abutment tooth with sharp angles such as MOD.
    Download PDF (2952K)
  • Part 2. Quantizing for Spectral Analysis
    Kazuhiro Nagata, Satoshi Hatate
    1996 Volume 40 Issue 1 Pages 97-108
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    The method of quantitative frequency analysis for TMJ sounds was studied. Since the frequency analysis was strongly affected by some analyzing conditions, these conditions were studied.
    The subjects were divided into groups according to the pathological state and TMJ sound, and the analyzing conditions for differentiating the groups were selected.
    The results were as follows:
    1. It was necessary to apply over 6 kHz of sampling frequency to enhance the potential for differentiating TMJ sounds.
    2. There were no specific relationships between spectrum patterns, pathological states and TMJ sounds.
    3. A spectrum peak for TMJ sounds was present in the bass register, but frequency components tended to decrease with higher pitched sounds. Therefore, it is suggested that TMJ sounds should be evaluated with 2 parameters-(a) maximum frequency, and (b) FFT integrated value.
    4. As for optimal analyzing conditions, amplitude spectrum, unused window, and 3 mV cut off level should be combined.
    Download PDF (2798K)
  • Hiroto Shinoda, Kenji Warita, Tadaharu Kawawa, Daisuke Higuchi
    1996 Volume 40 Issue 1 Pages 109-116
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    The purpose of this study was to investigate the accuracy of interocclusal recording materials that reproduced intercuspation. Two types of stone casts for measuring were selected and mounted on the verticulator. One stone cast (Crown type) that was prepared for a single crownmaintained stable intercuspation. Another stone cast (Bridge type) that was prepared for a fixed partial denture could not maintain stable intercuspation. For interocclusal records, which were made from President Jet Bite, Exabite, Ramitec, Xanthano, Impression Paste and New Plastone between the upper and lower stone casts, the occlusal heights of the stone casts on the left molar of the abutment side, anterior teeth and right molar were measured using an IP-Checker. The President Jet Bite, Exabite and Ramitec elastic materials were studied to determine the influence of the recording extents.
    The results were as follows:
    1. The occlusal height of both stone casts was higher for the left molar and the anterior teeth than for the right molar.
    2. The occlusal height of the Bridge type was higher than the Crown type.
    3. The results suggest that interocclusal records made from addition type silicone impression materials have the best reproducibility of intercuspation and a smaller recording range has greater reproducibility of intercuspation.
    Download PDF (2273K)
  • Sakae Yasui, Takashi Nokubi, Kimie Nakamura, Tadashi Nagashima, Minoru ...
    1996 Volume 40 Issue 1 Pages 117-121
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    In order to determine the vertical dimension of occlusion utilizing the edentulous patient's perception of mandibular position, we have been developing a new method and apparatus. The aim of this study was to clarify how the position of occlusal support influence the perception of mandibular position of ten edentulous subjects when the constant method is used.
    The testing apparatus was composed of an upper occlusal rim, a lower base plate with three metallic cylinders and nine different height occlusal blocks at intervals of 1 mm. The subject was asked to indicate whether each height inserted 10 times at random was felt to be high, low, or comfortable. The upper and lower limens that elicited a response of high or low in 50 percent of the trials were calculated. The zone between these limens was the comfortable occlusal zone (COZ). In this study, the records of COZ were performed under the three following conditions ; A: one occlusal support at the incisal region, B: three occlusal supports at the incisal and bilateral first molar regions, and C: two occlusal supports at the molar regions.
    The COZ obtained in posterior contacts (C) was significantly higher in position (p<0.01) than those obtained in anterior contact (A, B). It was suggested that the position of occlusal support should be standardized when the perception of mandibular position is used to determine the vertical dimension in complete denture construction.
    Download PDF (1543K)
  • Yutaka Hosoda
    1996 Volume 40 Issue 1 Pages 122-132
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    Thirty-five patients with internal derangement of the temporomandibular joint who had unilateral anterior disc displacement without reduction were studied. The patients were classified according to the degree of disc displacement and the presence or absence of an abnormal disc configuration on magnetic resonance imaging (MRI). Arthroscopic examination of the upper joint compartment was also performed, and intra-articular changes on the disc surface, the articular surface of the temporal bone (load-bearing areas) and the synovial lining (a load-free area) were classified. The findings were compared with the corresponding mandibular tracking patterns to study the association between these factors. The results were as follows:
    1. There was no discernible relation between the mandibular tracking patterns and the disc conditions (degree of disc displacement and disc configuration on MRI).
    2. An analysis of the arthroscopic findings of the upper joint compartment and the corresponding mandibular tracking patterns revealed no distinct relation between the mandibular tracking patterns and morbid findings of the articular surface of the temporal bone and disc surface. However, there was a significantly increased incidence of decreased range of opening motion (p<0.05) and unstable maximum opening position (p<0.01) among patients with evidence of fibrous adhesion of the synovial wall, especially at the anterolateral portion of the upper joint compartment, and those with fibrosis of the synovial wall.
    Download PDF (2840K)
  • Influence to the Changes in the Powder Particle Size Distribution of Glass Ionomer Luting Cement on the Retention Force of Crowns
    Momoko Ohmae, Hideaki Shiono, Masataka Shibuya, Shinya Watanabe, Takay ...
    1996 Volume 40 Issue 1 Pages 133-140
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    When cementing a crown, the amount of final seating is affected by the film thickness of the dental cement. To decrease the film thickness of glass ionomer cement (GIC), a GIC powder (Shofu Hybond Glass ionomer CX) was milled and three experimental fine particle powders were produced. The purpose of this study was to investigate the physical properties of fine particle GICs (ISO-9917, compressive strength, setting time, film thickness) and retention force of the crown cemented. The powder was milled with Centrifugal Fluidized Milling Machine (CF-160 Ube Kousan Co.) to produce the particle size (CX-01: maximum particle size:∅6μm, CX-02: 8μm, CX-03: 12μm). The results were as follows: In specimen containing a large amount of fine particles (CX-01), the best seating of a crown was accomplished (total film thickness: 8.0μm), though both compressive strength and film thickness was reduced to some extent. On the other hand, there was no significant difference between the retention force of normal GIC and fine particle cement (CX-01, 02, 03). The setting time of CX-01, 02, 03 was slightly longer than that of normal GIC.
    Download PDF (3580K)
  • Takahiro Sato, Hiroyuki Miura, Shigeo Hasegawa
    1996 Volume 40 Issue 1 Pages 141-146
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    The marginal fit of twenty-nine collarless metal ceramic restorations was measured in vivo with the Margin-Checker Type I, by which both the marginal gap and the horizontal discrepancy can be measured intraorally. All collarless metal ceramic crowns were fabricated with the direct-lift technique when using porcelain material with visible light-cured resin carrier.
    Over 80% of single crowns showed marginal gaps of less than 80 micrometers. In comparison with conventional metal ceramic margins, however, collarless porcelain margins showed greater marginal gaps, especially in case of abutments for fixed partial denture.
    To investigate the marginal characteristics of collarless metal ceramic crowns, marginal seals were evaluated on facial and lingual surfaces of embedded and sectioned specimens with the SEM micrograph. The exhibited characteristics of porcelain margins were rounder edges and greater marginal gaps than conventional metal ceramic crowns. It was suggested to improve the method for making porcelain margins because of an increasing demand for dental restorations with high esthetic qualities
    Download PDF (3954K)
  • Evaluation by Using Fixed Partial Denture Model Having Mandibular Third Molar as Abutment Tooth
    Yoshito Minesaki, Jun Nakahara, Naoyuki Shinohara, Hiroyuki Minami, At ...
    1996 Volume 40 Issue 1 Pages 147-153
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    The laboratory fixed partial denture models, made from Ni-Cr alloy or Au-Ag-Pd alloy, were used to measure the retentive force of one retainer (full cast crown) luted on the abutment before and after thermal cycling and to evaluate the retentivity and durability of various luting materials.Three types of conventional luting materials and two adhesive resins, 4 META-MMA/TBB resin and phosphate ester composite resin, were used.
    The retentive forces with adhesive resin, glass ionomer, polycarboxylate and zinc phosphatecements were 57.3-74.0, 26.3-30.6, 17.9-20.2 and 11.3-19.5 kgf respectively after 24-hour immersion in 37°C water (thermal cycle 0). There was no significant difference in the retentive force between Ni-Cr and Au-Ag-Pd alloy in all luting materials except phosphate ester composite resin. The retentive force with 4 METAMMA/TBB resin was significantly decreased by the thermal cycle test up to 50, 000 cycles, while those with other luting materials were hardly affected by thermal cycling.
    Download PDF (3207K)
  • Takayuki Masuda, Hiroyuki Miura, Hitoshi Kato, Yuzuru Furuki, Shigeo H ...
    1996 Volume 40 Issue 1 Pages 154-159
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    Distortion caused by occlusal force in the maxillary molar area was measured by tooth displacement without occlusion and proximal contact in both frontal and horizontal planes.
    Displacement of the subject teeth in biting was determined by three-dimensional measurement of the physiological tooth displacement caused by the occlusal force of periodontal tissue in the maxillary molar area. The subject teeth were influenced slightly mesiodistally in the horizontal plane when the application site of the occlusal force was changed. On the other hand, they were almost constant in the frontal plane. This suggests that the movements of the basal part of the maxilla in the molar area were relatively constant with the occlusal force.
    The displacement of other subject teeth, which have only mesial proximal contact, was changed from that of the above mentioned teeth. Therefore, it is very important to reconstruct both occlusal and proximal contacts without disturbing tooth displacement caused by the distortion of periodontal tissue during function.
    Download PDF (3001K)
  • Yoshihisa Yamabe, Takahisa Nakashima, Hiroyuki Fujii
    1996 Volume 40 Issue 1 Pages 160-166
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    An epidemiological survey on tooth loss and prosthodontic treatment in 1, 518 industrial employees was performed. The results were as follows:
    1. The periodontal conditions became worse with increase of age, especially the severity of periodontitis increased in the 45 years or more age group (p<0.0001).
    2. The prevalence of periodontitis was about 70% in the group having 1-4 teeth loss, and the severity thereof progressed in the groups whose teeth loss was more than 10 (p<0.0001).
    3. The prevalence of advanced periodontitis was lower in the participants replaced all their edentulous areas with prosthesis than that in the participants who were not (p<0.0001), and mean numbers of decayed and mobile teeth were also lower in the former (p<0.0001).
    4. In order to retain a large number of teeth and to maintain good periodontal conditions in elderly subjects, it is suggested that
    1) by the first half of the forth decade or while tooth loss is less than 10, they must undergo complete dental treatment and be motivated for oral hygiene,
    2) edentulous area has to be replaced with a prosthesis, and
    3) the prosthesis could direct their attention to oral hygiene and motivate them to personal care.
    Download PDF (2006K)
  • Kosuke Kashiwagi
    1996 Volume 40 Issue 1 Pages 167-179
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    The purpose of this study was to investigate the differences in coordination patterns of elevator muscles during gum chewing on the preferred and nonpreferred sides (PRC and NPRC) using normalized electromyographic linear envelopes (EMG LEs). Experimental tasks were carried out utilizing two kinds of gum with different hardnesses and ten normal subjects. EMG LEs normalized with respect to EMG amplitude and stroke were generated from surface EMG signals of bilateral anterior temporal, posterior temporal and masseter muscles (WTa, NWTa, WTp, NWTp, WM and NWM) and incisal point movement of the mandible. Differences in coordination patterns of EMG LEs for masticatory muscles between PRC and NPRC on different gum hardnesses were evaluated by the cluster analysis.
    On the soft gum, there was a high phasic similarity between EMG LEs of WM and NWTa during NPRC. NWM had similar phasic characteristics for another muscle during NPRC. On the hard gum, differences in muscle coordination patterns between PRC and NPRC were basically the same as those for soft gum chewing. From the viewpoint of chewing difficulty, there was no change in coordination patterns among WTp, NWTp and NWM between soft and hard gum on PRC in comparison with that between PRC and NPRC on soft gum.
    Download PDF (2857K)
  • Strength for Clinical Use
    Kazuyoshi Hashimoto, Toshiyuki Abe, Yasuhito Takeuchi, Mikihito Mori, ...
    1996 Volume 40 Issue 1 Pages 180-184
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    Laboratory work becomes very simple when castable ceramics, OCC, is used compared with other ceramics. As for esthetic dentistry, OCC has the same translucency and index of refraction as human enamel, and it can express the natural color of teeth.
    When dental metal is used for building up a dowel-core in the treated tooth, the metal color shows through the outer crown made of OCC, though translucency is one of the merits of OCC. This causes the loss of the natural tooth color.
    We have developed a method for improving the color of OCC crowns as follows: To preserve the esthetics of the OCC crown, the crown is built onto a dowel-core of OCC which is cast over a prefabricated titanium post (Para Post Unity Titanium Post) for reinforcement.
    In this article, the strength of the dowel-core with OCC and titan metal under clinical situations was examined. The obtained result supported the findings that the OCC dowel-core with a titanium post can be used in the same way as dental metals in clinical cases.
    Download PDF (888K)
  • Tomomi Sakano
    1996 Volume 40 Issue 1 Pages 185-194
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    From the point of view that soldering of titanium with gold solder is necessary for its application to partial dentures, the purpose of this study was to establish a technique of dental soldering with 16 karat gold solder.
    Success or failure of titanium soldering depends on the level of oxidation control. Therefore, a technique for vacuum furnace soldering was introduced. The influences of the vacuum degree and holding time on the soldering strength were investigated separately, and the best condition for each was considered.
    The technique was compared with the conventional technique of infrared soldering in an atmosphere of argon gas, and the possibility of applying it in the dental clinic was considered.
    The results were as follows:
    1. The lowest vacuum degree for successful soldering was 7.5 ×10-3 torr and a soldering strength of about 37 kgf/mm2 was obtained.
    2. Holding is unnecessary, because the soldering strength tends to decrease with increase of holding time.
    3. Good soldering strength could not be obtained by the present infrared soldering technique because of insufficient oxidation control.
    Download PDF (2836K)
  • Ryota Seki
    1996 Volume 40 Issue 1 Pages 195-207
    Published: February 01, 1996
    Released on J-STAGE: August 10, 2010
    JOURNAL FREE ACCESS
    Since mastication depends on the physical properties of foods, it is very important to know how food texture is changed by chewing. In this study it was assessed how the change in food texture with duration of chewing affected masticatory function.
    Eleven normal subjects and 6 patients with masticatory muscle disorders were asked to chew a piece of gum and the texture (hardness, gumminess, cohesiveness and stickiness) was measured by a texturometer at 10, 20, 30, 60, 90, 120, 180 and 240 seconds. The normal subjects showed significantly less hardness and gumminess of gum at 10 seconds.
    Masticatory movements and EMG activity were analyzed during gum chewing in 12 normal subjects and 8 patients. Comparisons were made between the early stage of chewing, when the texture varied widely, and the late stage, when the texture had stabilized. In normal subjects, there was considerable variation in masticatory movement and EMG activity between strokes during the early stage. However, the cycle durations were relatively constant throughout chewing. In patients, the cycle durations were constant, and masticatory movement and EMG activity did not vary between the early and late stages. The results showed that although the output of the central pattern generator is influenced by sensory feedback in normal subjects, it is not influenced in patients.
    Download PDF (2867K)
feedback
Top