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Part II. Infulence of Rebase, Reline, Occlusion and Rigidity of Maxillary Denture
Yoshinobu Maeda, Sadami Tsutsumi, Masatoshi Okada, Shigeru Idoji, Taka ...
1991 Volume 35 Issue 2 Pages
211-216
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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Occlusal force distribution is considered to be one of the major factors for bone resorption underneath denture base. We developed the program for simulating this process utilizing a two dimensional finite element model and an optimization program. In this report, influence of rigidity of denture base, loading condition, rebase and reline and on bone resorption were examined and following results were obtained.
1. Rigidity of the denture structure had much influence on bone resorption. Denture base with high rigidity caused less resorption compared to the one with low rigidity.
2. Area and amount of bone resorption were closely related to the loading location and direction. Least amount of resorption was found when the load applied vertically at the palatal side.
3. Rebase and reline procedure without altering occlusion could result in further resorption.
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Casting Accuracy
Tetsuji Takeuchi
1991 Volume 35 Issue 2 Pages
217-230
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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The objective of this study was to clarify the casting accuracy of the upper and lower metal frame made by using three kinds of investments.
The results obtained were summarized as follows.
1. The difference between the master casts and the frameworks showed that both phosphatebonded investments with chromium-cobalt alloy, and plaster investments with nickel-chromium alloy were better than the other two: i. e., plaster investment with silver-palladium-gold alloy, and ethyl silicate investment with chromium-cobalt alloy.
2. Dimensional changes in each part of the metal frames showed that metal frames with either phosphate-bonded investments or with ethyl silicate investments produced shrinkage.
3. All four kinds of metal alloy showed shrinkage when made using ethyl silicate investment.
4. The following two experiments were carried out in order to reduce shrinkage. The first experiment was done by using casting ring liners. The result showed that the shrinkage was greater compared to using phosphate-bonded investments.
5. The second one was done by using gypsum impressed and expanded. This experiment showed that the percentage of shrinkage of metal frames using gypsum was almost the same as that of using phosphate-bonded investments.
This method may prove to be the most effective in solving the shrinkage problem.
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Yoshinobu Maeda, Takao Mori, Isao Emura, Masatoshi Okada, Takashi Noku ...
1991 Volume 35 Issue 2 Pages
231-235
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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To measure the occusal force three dimensionally on the tooth surface with the minimum jaw separation, we developed a miniature three dimensional transducer system utilizing force sensitive resin material and the computer program and tested its reliability.
The transducer has 10.0mm diameter with 0.3mm thickness and a cone shape metal loading tip was attached on its top (3.0mm in height). Loads applied at the loading tip which could distributed through the metal cone to the sensing surface which is divided into four equal segments. By calculating the force distribution ratio among four segments, the vector of the load could be determined.
1. Each section of the sensing surface showed fairly linear relation between load and output up to 5kg, so the sensor as a whole was capable for up to around 20kg force measurements.
2. With the A/D and the computer program, the direction and amount of the applied force was calculated and visualized on the display.
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Akira Niihara
1991 Volume 35 Issue 2 Pages
236-246
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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Recently, Bis-GMA-Tri-EDMA based composite resins have been widly used as a restoration material for tooth. However, it has been pointed out that the mechanical properties of these resins, such as elastic modulus and frictional wear, are obviously inferior to those of metal materials. Therefore, the author examined the relationship between the amount of residual monomer, which deteriorates the mechanical property of the cured material, and the frictional wear of its material.
All specimen were immersed into distilled water (37°C) for a constant period after polymerization, according to the experimental conditions, and each measurement was also carried out in water at a temperature of 23±0.5°C. The amount of residual monomer in the cured resins decreased markedly with a time after the polymerization manipulation and attained the minimum value of the residual monomer at a week after that.
On the other hand, the surface hardness of cured resins increased considerably as the time proceeds, and an adequate negative correlation was estimated between the amount of residual monomer and surface hardness of the cured resin (r=-0.96). In addition, a significant correlation was also estimated between the amount of residual monomer and the magnitude of the frictional wear loss of the cured resin (γ=0.87). It was seen that the frictional wear loss diminished significantly according to the decrease of residual monomer and to the increase of filler content to the resin.
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Part 2. The Relationship between Mandibular Fossa and Condyle on Mandibular Movement
Yasuhiko Sakai
1991 Volume 35 Issue 2 Pages
247-255
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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Structural study of the temporomandibular joint is a key issue in prosthodontics because the T. M. J. is the most important element of mandibular movement. As three-dimensional investigation is needed in this field, I recently developed a personal computer system that can form three-dimensional images of the T. M. J.. The use of three-dimensional images created by the computer system is effective to research the shape of the T. M. J. and mandibular movements. Using this system, I studied the relationship between mandibular fossa and condyle on mandibular movement.
The results are as follows:
When the condyle movement traces the curve of the frontal wall in the middle of the fossa, the condyle approaches the wall more closely at its inner part than at its outer part.
Three-dimensional images of the T. M. J. can be reconstructed from successive sections of a T. M. J. of a dry skull and by the addition of movement data, mandibular movement can be simulated.
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Minoru Takeshita, Hiroyuki Shimazutsu, Hiroshi Ishida, Mitsuhiro Tamam ...
1991 Volume 35 Issue 2 Pages
256-261
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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The Hygojet
TM System (Dürr Dental GmbH & Co. KG, Germany) is the fast and safe cleaning and disinfection system for impression materials of all types in dental practices. The dimensional change and the surface roughness of five kinds of impression materials, that is, AROMA FINE and HI-TECHNICOL alginate impression materials, SURGIDENT hydrocolloid impression material, and XANTOPREN and EXAFLEX silicone rubber impression materials, following the treatment with this system were evaluated. The results were as follows.
1. No significant reduction was observed on the dimensional change of all kinds of impression materials.
2. No significant effect was observed on the surface roughness of all kinds of impression materials.
The results of this study indicated that Hygojet
TM System had no adverse effect on the dimensional change and the surface roughness of the impression materials of all types tested.
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The Amount of Movement from the Application of a Constant Force
Hiroyuki Waga, Kazutoshi Furukawa, Katsu Sato, Riichiro Sato, Satoshi ...
1991 Volume 35 Issue 2 Pages
262-268
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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In order to verify what effects bridges have on abutment teeth movement during mastication, we first measured the movements of each abutment tooth separately and compared those results to when they were used as bridge abutments.
The results were as follows;
1. When a constant force was applied to the individual abutment teeth, a buccolingual movement was recorded. However, this movement was drastically reduced when used as bridge abutments. No particular movement was recorded in the vertical direction.
2. Compared to the individual abutment teeth, the bridge abutments showed a reduction in the buccolingual and vertical movements when biting down on some test food products.
3. The level of reduction in the amount of movement varied depending upon the person.
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Cleaning of Denture at Home and Outside Home
Yoshinobu Maeda, Naoya Seya, Shigeru Idoji, Masatoshi Okada, Takashi N ...
1991 Volume 35 Issue 2 Pages
269-274
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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Denture wearers have different problems from non-denture wearers in terms of maintaining oral health.
In this study, we attempted to find out specific difficulties of denture wearers with questionnaires about social life problems as well as oral hygiene problems. Our results indicate that about the half of the patients we surveyed remembered the instruction for denture cleaning methods. Most of the denture wearers considered the cleaning of denture was essential to maintain their oral health, though methods they employed showed a great deal of difference.
Also denture wearers cared much about for other people's attention and felt much difficulties in cleaning their dentures when they were not at home.
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Naoya Seya, Yoshinobu Maeda, Shigeru Idoji, Masatoshi Okada, Takashi N ...
1991 Volume 35 Issue 2 Pages
275-280
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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The purpose of this study was to find out opinions of non-denture wearers (NDW) regarding images of denture wearers (DW).
1. Elder NDW could recognize dentures better than younger NDW.
2. Main reasons for the recognizing dentures were, artificial teeth arrangements, color of denture base and clasps.
3. NDW concerned mainly for DW's behavior such as removing dentures in person, leaving dentures on tables and so on.
4. NDW did not pay much attention for DW in public places and also approved the importance of denture cleanings.
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I. Analysis of Craniofacial Forms
Koji Takeuchi, Toshimitsu Iinuma, Yoshihiko Moriya, Kan Hasegawa, Kura ...
1991 Volume 35 Issue 2 Pages
281-289
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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While jaw functions as cooperative work of the jaw muscles and the nervous system appear in craniofacial regions, the forms of their appearance are said to vary according to the differences in craniofacial forms in which the jaw functions appear. Hitherto, a number of reports have been published on relationships between jaw functions including bite force and facial forms, but none of them clearly reports on morphological classification methods in examining the relationship between jaw functions and facial forms. So, in this study, the authors analyzed the craniofacial regions as fields in which the jaw functions appear and conducted their grouping according to morphological and functional differences, using cephalometric photographs. As the first step, the authors attempted to establish, and examined, indices for different groups, the indices that most clearly indicate on the cephalometric photographs the morphological differences in the craniofacial regions. As a result, it was found that SN-MP on the cephalometric photographs are the most effective as indices showing the morphological characteristics of the craniofacial regions.
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Part 1. Denture Plaque Score
Shigeru Idoji, Takao Mori, Yoshinobu Maeda, Masatoshi Okada, Takashi N ...
1991 Volume 35 Issue 2 Pages
290-292
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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This article describes the newly designed denture plaque score (DPS) for demonstrating the amount and the location of denture plaque accumulation. We examined the reproducibilityand reliability of the DPS, by testing inter and intra operator statistical differences.As the result, our newly designed DPS has been proven to have statistically significant reproducibilityand reliability as well as to have a great deal of potential for clinical application.
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Shin Ito
1991 Volume 35 Issue 2 Pages
293-305
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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Effect on the masseter muscle activity was studied electromyographically and kinesiographically comparing hard and soft occlusal splint wearers during tapping movement.
Five subjects having normal occlusion were used in this study. Surface EMGs of the masseter muscle were recorded before and immediately after wearingeither hard or soft splints, 3 days and 7 days after wearing splints, and 7 days after removal ofsplints. And then those data were analyzed.
The results were as follows:
1. In the maximum opening distance during tapping movement, hard splints showed lesschanges over time, whereas it increased in soft splints.
2. In the EMG time parameters, influential changes were observed in soft splints.
3. CV values of the EMG time parameters tended to increase after wearing soft splintscompared to hard splints.
4. Integrated potential of the EMG decreased somewhat over time after wearing hardsplints, but increased markedly immediately after wearing soft splints.
5. CV values of the integrated potential of the EMG showed remarkable increase in softsplints compared to hard splints.
The above results revealed that compared to hard splints, soft splints exhibited influentialchanges of the masseter muscle activity by increasing its muscle activity.
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Part 3. The Collarless Resin Veneered Crowns
Hiroshi Shimizu
1991 Volume 35 Issue 2 Pages
306-315
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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The collarless porcelain veneer crown has been advocated in several reports and is actually in use recently. However, this sort of technique has not yet been applied to the resinveneered prosthesis.
The present study was planned as a way to investigate the possibility of the collarless resinveneered crown. Thus, the influence of the differences in shape of metal frameworks, the effectivenessof hardening heat treatment and adhesive luting agents, and the properties of veneeringresins were examined by measuring the strain on the cervical part of the crowns caused by staticpressure.
The results of the investigation are as follows:
1. In the experiment using metal frameworks without veneering resin, the differences inshape did not exert any influence and the thick underlying metal was better than the thin one.
2. In the experiment using test pieces of resin veneered crown, the influence of differencesin shape was negligible.
3. The hardening heat treatment was not effective within the range of elastic transformation.
4. The strain on crowns veneered with CESEAD had a magnitude smaller than the strain onthose veneered with New-METACOLAR L.
5. The strain on resins of veneered crowns had a magnitude larger than the strain on metalframeworks with the same shape.
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The Effect of Mechanical Stimulation to the Denture Supporting Mucosa on Masticatory Muscle Activity
Yoshiki Endo
1991 Volume 35 Issue 2 Pages
316-330
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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The mechanisms of controling mastication in complete denture wearers who have lost the natural tooth proprioception are poorly defined as yet. In the present study, the contributionof sensory inputs from denture supporting mucosa to regulate the masticatory movementwas examined electromyographycally. In experimental dentures, a metal half hemisphere (0.5 mmdiam.) was attached on the premolar region of the mucosal surface of the habitual chewing sideof either upper or lower denture as mechanical stimulation (innoxious). Surface EMGs of bilateralmasseter (Mm) and posterior temporal (Tp) muscles were recorded simultaneously with Sirognathograph (SGG) during mastication of two types of test foods on the habitual side. The data was statistically computed by means of analysis of variance.
The results were as follows:
1. In EMG burst duration after occlusal contact, in SGG occluding phase time ratio andmaximum opening distance showed different reactions between soft and tough foods wearingexperimental denture and marked difference in lower experimental denture.
2. Integrated potential of the EMG increased wearing experimental denture and the grindingmotion exaggerated because of an increased integrated potential of balancing side Tp in lowerexperimental denture.
3. CV values of EMG time paramreters and integrated potential increased wearing experimentaldenture and markedly increased in lower experimental denture.
From these results, it was suggested that the mechanoreceptors in the denture supportingmucosa might play an important role in the control of sensory feedback on masticatory function ofthe complete denture wearers.
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Part 2. Wear Resistance of Posterior Artificial Teeth against Metal
Yoshinori Satoh, Eiichi Nagai, Kengo Maejima, Masao Morikawa, Kenji Oh ...
1991 Volume 35 Issue 2 Pages
331-338
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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Hight-strength denture teeth (hereafter referred to as HS teeth) were developed to improve hardness and wear resistance of the conventional plastic denture teeth, while retainingtheir feature of easy occlusal adjustment.
The objective of this study was to evaluate abrasive wear resistance of HS posteriorteeth. We conducted the two-body abrasive wear test and measured teeth wear depth usingeight types of posterior artificial teeth as one body, measured metal wear volume using Pd-Au-Agalloy plates as another one body.
The result of the two-body abrasion wear test revealed that the HS teeth have 4.7timesgrater abrasive wear resistance than conventinal plastic teeth, 0.7times grater than porcelaintooth, 8.3times grater than metal tooth. It was also found out that metal wear contact with HSteeth is smallest abrasion wear volume compare with another metal wear.
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Histopathological and Cellular Physiological Study
Noriaki Orikasa, Haruka Kusakari, Tomoyuki Kawase, Akitoshi Suzuki
1991 Volume 35 Issue 2 Pages
339-350
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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The purpose of the present study is to evaluate the effects of low power laser on bone formation.
In the
in vivo study, artificial bone defects in the mandible of the dogs were used to investigatethe effect of laser irradiation on the process of healing. The number of cellular elements inbone marrow, including osteoclasts in Howship's lacnae, increased on the laser-irradiation side at3 days after the operation. At 7 days, the mass of newly formed bone around the defect on thelaser-irradiation side was apparently more than that on the control side. In the later days, however, there were no differences between the two groups.
In the
in vitrostudy, osteoblastic cells (UMR 106) were used to investigate the effect of laserirradiation on their function. Laser irradiation increased DNA synthesis in the cells at a logarithmicphase without effect on their morphology. To exert this stimulatory effect, more than 3min/day laser irradiation was necessary in the presence of more than 5%(v/v) FCS. In both PTHand PGE
2-treated cells, however, laser irradiation had no significant effect on DNA synthesis. Inaddition, laser irradiation increased alkaline phosphatase activity (per protein).
These findings suggest that low power laser may stimulate the osteoblast-mediated boneformation.
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Comparison of Bio-active and Bio-inert Materials
Hiroyuki Yamada, Haruka Kusakari, Shigemitsu Yoshida
1991 Volume 35 Issue 2 Pages
351-365
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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Bone formation and microvascular changes after implantation of bio-active (glassceramic) and bio-inert (alumina-ceramic) materials were studied chronologically by LM, TEMand SEM of corrosion casts.
The results were summarized as follows:
1. In the early stage, bone formation was observed directly on the glass-ceramic and densevascular network was found on the interface of the implant. In case of the alumina-ceramic, however, coarse vascular network was found among the newly-formed bone trabeculae.
2. At 4 weeks, the bone on the glass-ceramic became to connect with the surrounding bone.In case of the alumina-ceramic, two types of areas were observed; one was active bone formationarea and the other was active bone resorption area. Therefore, after 4 weeks was thought to be animportant stage which would influence the condition of the surface of the implant.
3. At 8 weeks, bone was formed on most part of the glass-ceramic. Multinucleated giantcells (MNGCs) having ruffled border were recognized in the area where bone was not formed. These MNGCs were thought to relate the bone remodelling on the surface of the implants. Onthe other hand, alumina-ceramic was covered with bone or fibrous tissue, and no active boneremodelling was observed.
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II. The Three-dimensional Bite Force Measurement Sytem
Toshimitsu Iinuma, Nobuhito Gionhaku, Yoshihiko Moriya, Koji Takeuchi, ...
1991 Volume 35 Issue 2 Pages
366-380
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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The purpose of this study was to explicate the mechanism of jaw movement and itscontrol system, using bite force and EMG of the masticate muscles with a view to examine theresult as an effective means of treatment. A new system of taking three-dimensional bite forcewas developed, which can take the value and direction of bite force. The description and evaluationof the new system and the result of the load test are presented.
The results were as follows:
1. The vertical and lateral direction (60 degree on occlusal plane) load tests revealed thatthe precision of the three-dimensional bite force measurement system was fully established.
2. When using this system, it is necessary to use the jig for fixing the maxillary andmandibular clutches.
3. Using an oscilloscope as the bite force feedback device was useful to instruct the level ofbite force.
4. This system is very effective to measure the value and direction of bite force.
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A Trial of Bone Quality Analysis with DIP Method
Minoru Ueda, Yoshihiro Sawaki, Masao Ito, Iwai Tohnai, Hideki Mizutani ...
1991 Volume 35 Issue 2 Pages
381-389
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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Seven patients were reconstructed their occlusion with osseointegrated implant (Branemark System) in Department of Oral Surgery, Nagoya University Hospital. Three cases ofpatients have been analysed for their mandibular bone quality with Digital Image Processing (DIP) method preoperatively. Results obtained were as follows:
1. Seven patients who had an extreme difficulty in wearing conventional removal dentureswere treated in this study. The subjects consisted of 3 males and 4 females, and their agesranged from 46 to 66 years.The lesion was an edentulous mandible in 3 cases, an edentulous maxilla in one case andpartially edentulous in 3 cases.
2. Twenty one fixtures in maxilla and 23 fixtures in mandible, totally 44 fixtures wereinstalled in 7 cases.One fixture in mandible and one in maxilla failed to osseointegrate, giving the fixture survivalrate of 95.2% in mandible and 95.7% in maxilla.
3. Three edentulous mandibular patients received the bone quality analysis (DIP method) using occlusal film preoperatively. Results of bone density were 2.98, 1.98, 3.10Almm in eachcase.Case 2 who had the lowest bone density failed one fixture to osseointegrate.
4. DIP method was very useful as a bone quality measuring method. Because it could beeasily carried out to analyse the jaw bone quality for dental implant without any variation offilm conditions.
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Akira Kawano, Masayoshi Okuda, Masatsugu Okada, Hiroshi Nishizaki, Har ...
1991 Volume 35 Issue 2 Pages
390-394
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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Eight healthy male subjects were asked to unilateral gum chewing continuously for 30min and other five subjects were asked to periodic clenching to the signals monitored on theoscilloscope for the same time. The signals were consisted of the three kinds of durations (500ms, 1s, 2s) and interval of 500ms. The force of clenching was as same as chewing. Surface EMG was picked up from a masseter muscle on the side of chewing.
No significant changes were shown in EMG activity and mean frequency during gum chewingthrough the experiments. On periodic clenching, EMG activity strikingly decreaced in 5minand mean frequency was down significantly in 30min, of which tendency was clearer in long timedurations. These findings suggested that the fatigue was not appeared in gum chewing for 30min and it was appeared for a long time in periodic clenching as compared with gum chewing.
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Hideo Kanaya, Masahiro Aida, Yoshizumi Murata, Tohru Hayakawa, Kozo Ho ...
1991 Volume 35 Issue 2 Pages
395-401
Published: April 01, 1991
Released on J-STAGE: August 10, 2010
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The effectiveness of Laminabond Porcelain Primer on the porcelain adhesion was investigated in this study. The lamina Bond Porcelain Primer was newly commercial availablesilane coupling agent which is one bottle type.
The porcelain surface was polished with # 1, 000 paper and treated with Lamina Bond Porcelain Primer for 30 seconds. As composite resin, Lamina Bond Composite Resin or Esthelay Cementwere used. The shear bond strengths between composite resin and porcelain, and thosebetween enamel and porcelain mediated by the composite resin were measured after one dayimmersion in 37°C water or thermocycles between 4°C and 60°C.
While without Porcelain Primer treatment, the bond strengths between composite resin andporcelain were as low as about 50 kgf/cm
2, with Primer treatment the bond strengths increased toabout 150 kgf/cm
2. After thermal cycling tests, the bond strengths of Lamina Bond Composite Resin to the primed porcelain remarkably decreased, but those of Esthelay Cement did not.
There were no decrease of the bond strengths between enamel and Primer treated porcelainmediated by the composite resin after thermal cycling tests.
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