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Yoshinori Tamazawa, Kohei Kimura
1991 Volume 35 Issue 5 Pages
855-862
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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The all porcelain post crown, which had been cemented as a substitute for the upper left canine of a patient at Tohoku University School of Dentistry, Department of Prosthodontics in 1970, fell off five years and six months after cementation.
Subsequent inspection of the post crown disclosed that the post which had been used was tapered and too short for the size of the tooth crown, and was directly subjected to bite force because the root cap of the post crown had been simply attached to the tooth substance. To avoid such imperfections, a metal core and porcelain jacket crown were applied. However, the porcelain jacket crown fell off together with the metal core while the patient was having a meal in May 1988, twelve years and four months after cementation. The abutment tooth was simultaneously broken and had to be extracted.
As described above, we followed the prognosis of a case for eighteen years starting from the primary treatment at the Department of Prosthodontics of Tohoku University, with particular attention to the latter twelve years and four months, during which time a porcelain jacket crown was in place.
Based on these observations, we report problems encountered in the case and possible countermeasures.
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Part 2. Occlusion at Lateral Movement on Working Side
Yoshihiro Tanaka
1991 Volume 35 Issue 5 Pages
863-877
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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The method and the subject of the studies in Part 2 were the same as in Part 1. And, the method of study used was the “Superposed rubber pattern method”.
The occlusions were examined at the positions of 1 mm, 2 mm and 3 mm lateral movements from the centric on the working side.
The results were as follows:
1. The rates of share were found by comparing the values of the five different dimensions in the intercuspal position with the values of each at the lateral movements mentioned above (100 is the base value of the intercuspal position). The average values were 107.3%, 133.0% and 158.1% at each positions, respectively, in the area of the intraocclusal distance over 2.0 mm. The average values were 160.8%, 175.3% and 139.3% at each positions, respectively, in the area of the from 2.0 mm to 1.0 mm. The average values were 107.9%, 65.0% and 42.6% at each positions, respectively, in the area of the from 1.0 mm to 0.5 mm. The average values were 42.4%, 21.0%, and 13.1% at each positions, respectively, in the area of the under 0.5 mm.
2. The average values were 4.23 mm
2, 1.88mm
2 and 0.99mm
2 at each positions, respectively, in the area of the under 0.05 mm.
3. The average values of intraocclusal cubic volume were 396.11 mm
3, 513.46 mm
3 and 596.55 mm
3 at each positions, respectively.
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Part 1. Principal Stress Analyses by the Three Dimensional Finite Element Method
Toshiya Ishikawa
1991 Volume 35 Issue 5 Pages
878-891
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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Recently, various dental implants have been applied to edentulous ridge to restore masticatory function. Because endosteal implants are directly contact with bone without periodontal membrane, and the shock of occlusal force is transmitted directly to peripheral bone. Especially, when lateral occlusal force effected to the implants, it is reported that the force will cause the resorption of the peripheral bone.
When screw shaped endosteal implants were implanted in the mandibular bone and applied a occlusal force, the principal stress were analized with the three dimentional finite element method, and the mechanical response was compared with that of a natural tooth.
The results were as followed.
In the case of natural tooth, periodontal membrane and cancellous bone were functioning as the shock absorber. On the other hand, cancellous bone functioned as the shock absorber at axial load and load 20° to long axis on buccal side in the case of implants. However there were few sites inducing large compressing stress at load 20°. There is a necessity of shock absorber that would not be originate bone resorption. At load 90°, large compressing stress were induced at whole mandibular bone. It is suggested this load was never effected on the implants.
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Yuji Ueda, Nobuhiro Yatsuzuka, Masaaki Sagara, Kazuhiro Tsuga, Shin-ic ...
1991 Volume 35 Issue 5 Pages
892-899
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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A new protocol for classifying of TM disorders was developed in order to classify the types of TM disorders followed by the criteria of Japanese Society for Temporomandibular Joint.
This protocol consists of following several characteristics.
1. It may be possible to shorten filling up time because of a filling up way of systematic procedure and selecting minimum items.
2. It may be possible to classify TM disorders quickly because an instruction for filling up and a table for classifying the type of TM disorders are attached.
3. It may be easy to evaluate the process of change of symptoms.
4. It attaches a table of examination for finding differential diagnosis of TM disorders.
5. It may be possible to fill up the results for various examinations of jaw function.
6. It may be possible to use the construction of data base for the protocol for TM disorders by Japanese Society of Stomatognathic Function.
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Hideki Hirose, Yoshimichi Gonda, Isumi Toda, Yoshikuni Ohta
1991 Volume 35 Issue 5 Pages
900-906
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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There have been few investigations on the microvascular architecture supplying the articular disk of the temporomandibular joint (TMJ). The present authors have attempted to examine detailed microvascular patterns utilizing the plastic injection method for preparing microvascular casts of the entire components of the TMJ in the Japanese monkey. Vascular supply for the disk was limited in the peripheral area of it, while not present in the center area of it, appearing as the so-called avascular area. Fine vascular networks were observed both in the superior and inferior synovial layers of the disk. From these networks, abundant capillary loops were diverged towards the center of the disk. Differences on the distribution feature and density of the vascular element were observed between both the above networks, in proportion to functional movements of the condyle.
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Patterns of Chewing Path during Mastication of Various Foods in Normal Subjects
Keiji Haga, Hiroshi Shiga, Yoshinori Kobayashi
1991 Volume 35 Issue 5 Pages
907-918
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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In order to investigate the effect which the consistency of the food has on the masticatory path, 78 normal subjects were asked to chew boiled fish paste, chewing gum, peanuts, and beef jerkey. The path pattern, the amount of opening, and the width of mastication were investigated using an automatic masticatory movement analyzing system, and the following results were obtained.
1. The two patterns, pattern I (smooth opening toward the working side, and convex closing) and pattern ifi (opening toward working side after initially toward non-working side and convex closing) constitute the majority of the patterns observed.
2. In the group which showed pattern I in chewing boiled fish paste, the most frequent case was pattern I in all other three food.
3. In the group which exhibited pattern III in chewing boiled fish paste, the majority cases showed pattern DI in all other three food also.
4. The amount of jaw opening and the width of mastication increased with the hardness of the food.
5. It is suggested that although the path of mastication varies as the type of food changes from soft to hard, the majority of the path pattern can be represented by patterns I and III in normal subjects. Also, though there are cases which relate pattern I to soft food and pattern III to hard food, basically the consistency of the food does not affect path patterns.
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Shinji Uchida, Reitaro Takahashi, Kazunori Nishiura, Harukazu Kanehira ...
1991 Volume 35 Issue 5 Pages
919-922
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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Six male subjects were studied to determine the effect on the EMG power spectra of shortening the inferior head of the lateral pterygoid muscle (ILPt) during isometric protrusive and lateral protrusive contraction at three different muscle lengths.
Among all muscle lengths, no significant difference in mean frequency of EMG power spectra was seen on either side of the ILPt during isometric protrusive contraction, or on the contralateral side of the ILPt during isometric lateral protrusive contraction. This result is similar to that for the digastric muscle during isometric under opening at various jaw positions, but differs from those for the temporalis and masseter muscles at during isometric clenching at various jaw positions.
It was speculated that this lack of significant mean frequency change at different muscle lengths is characteristic of the EMGs of jaw depressor muscles.
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Hidekazu Takahashi, Mitsuhiro Murakami, Takako Fujyu, Tadaharu Kawawa, ...
1991 Volume 35 Issue 5 Pages
923-930
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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The interest in the application of titanium and its alloys to dental prostheses is increasing since they possess good mechanical properties. However, fabrication of titanium prostheses, especially the casting procedure, has been very difficult because of its chemical reactivity at high temperatures. In our previous study, we could obtain a sound titanium casting using the calcia mold which is very stable for titanium. In this study, we investigated the calcia investments containing metal titanium powder to improve the casting accuracy. Setting and thermal expansion at 1, 000°C of the calcia investment with 8.8wt% titanium powder was 0.5% and 1.2%, respectively. The marginal opening and cement layer thickness between the die and the titanium cast crowns obtained from the calcia mold fired at 1, 000°C were found to be improved when the content titanium powder was 8.6wt% or 8.8wt%. The contamination of oxygen produced a hardened layer with a thickness of about 250μm under surface of titanium casting; nevertheless, it was possible to finish a glazing surface by the conventional polishing procedures.
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The Relationship between Oral Status and the Progress of Dementia at Senile Hospital
Kimie Okimoto, Koji Ieiri, Koichi Matsuo, Yoshihiro Terada
1991 Volume 35 Issue 5 Pages
931-943
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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In order to clarify the relationship between mastication and senility, 87 senior patients over 65 years old (78.5 on average) hospitalized in senile hospitals were studied on the progress of dementia, diseases, eye sight and hearing acuity generally, on DMF index, maximum biting force, height of rest of alveolar ridge, frequency of denture use, complaints about present denture and on the precence/absence of spouse, friends and hobbies psychogenicly.
The results were obtained as follows.
1. The most frequent disease at senile hospitals where many patients had been long hospitalized was disease of bones and joints such as osteoarthritis and osteoperosis. The second most one was disease of circulatory system, such as hypertension, cerbrovasucular disease and heart disese. 47% patients were diagnosed senilia.
2. The study showed that the progressed senility reduced the number of residual teeth, the use of denture and the maximum biting force.
3. Among psychological factors which seem to enhance the senility, the survival rate of spouses lowered as the senility of the patients progressed. The rate in the dementia group was about 1/3 of that in the normal group.
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Part 2. The Relations between the Arrangement of Posterior Teeth and the Border seal
Kiyoshi Takesako, Takayuki Nunoi, Hirofumi Kojima, Toshifumi Sakota, Y ...
1991 Volume 35 Issue 5 Pages
944-957
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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The atmospheric pressures under the maxillary complete dentures with and without the postdam, fabricated like a bite rim, were measured under the load application simulating six kinds of the tooth positions in the buccolingual diretion and three kinds of the food properties. The amount of atmospheric pressure and the period of keeping the border seal were evaluated in the relation to the conditions as described previously.
The following results were obtained.
1. The atmospheric pressure under the denture, comparing with the external one, became higher by the denture insertion and increased during the denture seating, and then decreased by the load application simulating the masticatory force, and at all became equal to the external one when the film of the saliva was destructed.
2. The position of posterior tooth in buccolingual direction, the presence of postdam and the food property had effects on the border seal of maxillary denture.
3. The tooth position arranged in more lingual site, addition of postdam, and smaller amount of load at the beginning of load application were useful for keeping the border seal.
4. Dynamics of atmospheric pressure under the denture base seems to be useful as an index of the denture stability.
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Part 1. Application of it to Oral Mucosa under Denture
Eiichi Nagaoka, Yuji Kamashita, Fukuharu Matsuzaki, Shuichi Inada, Nao ...
1991 Volume 35 Issue 5 Pages
958-967
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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In this study, application of the tissue reflectance spectrophotometry (TS-200) to the diagnosis of oral mucosa, was evaluated in the absorption intensity and the shape of the spectra of the gingiva of the rabbits. It is considered that the spectra obtained by TS-200 represent the hemoglobin absorbances and give information as to mucosal blood volume, average oxy- and deoxyhemoglobin equilibrium, and the tissue oxygen saturation. The measurements are given as value of H (hemoglobin concentration), value of A (oxyhemoglobin concentration), and value of F (O
2 saturation).
The measurements were taken under the conditions with and without the resin plate and furthermore with and without the holder of the sensor during measurement. The following results were obtained.
1. There were the differences between the measurements in a day and another day before the plate insertion and also under the conditions with and without the resin plate.
2. The difference between the measurements under the conditions with and without the resin plate was greater than the one between in two days before the plate insertion.
3. The tissue reflectance spectrophotometry could be applied freehand to the diagnosis of oral mucosa under the denture.
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Kazutoshi Kakimoto, Takeshi Kashiwamura, Hiroshi Matsuyama, Masako Shi ...
1991 Volume 35 Issue 5 Pages
968-976
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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Maxillary complete dentures were constructed with reinforcing polysulfon resin by the compression molding, reinforcing polycarbonate resin by the injection molding and polymethylmetacrylate resin.
The deformation from the each molding methods were observed in three dimension.
The results were comparatively discussed, and the following conclusions were obtained.
1. Both in the artifical teeth resion and mucosal surface of alveolar resion, the lateral shrinkage were distinctively observed in the conditions of reinforcing polysulfon resin and reinforcing polycarbonate resin. On the contrary, the even shrinkage and little distortion was observed in the condition of polymethylmetacrylate resin.
2. The lateral expansion of denture border in maxillary tuberosity resion were observed in the conditions of reinforcing polysulfon resin and polymethylmetacrylate resin, although the lateral shrinkage of that was observed in the condition of the reinforcing polycarbonate resin.
3. The midline of mucosal surface transitted anteriorly in the condition of reinforcing polysulfon resin and reinforcing polycarbonate resin.
4. In sagittal direction of the palatal midline, the deformation was the least in the condition of reinforcing polysulfon resin.
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Part 1. Suvey on Resin Denture Base Fracutres
Takayuki Ohtani, Yoshinobu Maeda, Kayoko Enomoto, Motofumi Sogo, Masat ...
1991 Volume 35 Issue 5 Pages
977-982
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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The objective of this study was to examine denture repair cases in terms of the design, material, usage and possible causes of defects. In this report, the relation between 237 denture base fracture cases treated at the student clinic in Osaka University from 1988 to 1990 and their fracture location were classified and analyzed.
Following results were obtained:
1. The number of denture base fractures in overall denture repair cases was decreased compared to our previous survey in 1985. One of the reason for the decrease might be the application of reinforcement method using adhesive resin and wrought clasp wire.
2. The most frequent fracture locations of resin denture base were found in the midline area in lower complete dentures, areas adjacent to abutment teeth in overdentures, areas adjacent clasps and other metal components of partial dentures.
3. Fractures in dentures with reinforcements were found in early stage after insertion. This result suggests that the adequate thickness of denture bases should be applied even with reinforcements to avoid fractures.
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Katsuhiko Sato
1991 Volume 35 Issue 5 Pages
983-996
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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The author has recently developed a new system, by which it is possible to investigate with the use of tow measuring device the effects of occlusal raising and head movement on the position of the tapping area. Using this system, I studied the position of the tapping points.
The results were as follows:
1. With the head inclination at 0 degrees, the distribution range of the tapping points when the occlusal raising is 1.5mm was 2-3 times larger than the distribution range when the occlusal raising was 0mm. This suggests that the system is useful for investigation of occlusal disharmony in the functional occlusal system. Also, in the high-accuracy measurement of mandibular position on the subjects with normal dentulous occlusion, it is necessary to select the process without the occlusal raising.
2. Tapping points were displaced in the same direction as the direction of head inclination.
3. The distribution range of the tapping points with the head in the horizontal basal position was the smallest. Therefore, when the maxillomandibular registration is to be taken, the head position must be provided.
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Seiichi Kano
1991 Volume 35 Issue 5 Pages
997-1006
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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This study was designed to examine the role of periodontal sensation in regulation of the masticatory movement in man. The periodontal sensation on the preferred chewing side was blocked by infiltration anesthesia induced at the upper and lower first molars. The subjects were requested to chew the chewing gums with three different hardness before and after anesthesia, and the masticatory movement and electromyographic activities were analyzed.
Only the maximal vertical and anteroposterior displacements were affected by anesthesia in the chewing test of all the three kinds of gum. However, other parameters of masticatory movement and chewing rhythm were only slightly affected by anesthesia. Whether statistically significant or not, the effect of anesthesia was more pronounced in chewing of soft and mediumhard gum. In chewing of hard gum, masticatory movement tended to be free from the effect of anesthesia. The muscle activity was diminished, although without a significant difference, by anesthesia. The ability of hardness discrimination was also not affected by anesthesia.
The above results suggested that in chewing of soft foods, the periodontal sensation plays an important role in regulation of the masticatory movement but in chewing of hard foods, the sensation of other tissues, e. g., muscle, is likely to be involved in regulation of the masticatory movement in man.
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Mitsuhiro Tamamoto, Kyoumi Nakamoto, Taizo Hamada, Shigeru Kametaka
1991 Volume 35 Issue 5 Pages
1007-1014
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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Candida albicans is known to cause denture stomatitis. In this study, the effects of four kinds of commercial denture cleansers (DC A, B, C and D) on C. albicans were evaluated under the various conditions. Yeast-lytic enzymes were contained only in DC A. Proteases were contained in DC A, B and C, and alkaline-oxidants were contained in DC B, C and D.
Candida-lytic activity was demonstrated only in DC A from the results of the reduction of optical density of yeast suspension, the microscopical observation and the degradation of β-1, 3-glucan.
Strong fungicidal effects were found in DC B and C. The fungicidal effect in DC D was slightly lower than that in DC B and C, and the effect in DC A, which contained no oxidants, was the lowest. However, it was found that a small amount of
Candida cells was alive, even in the solution of DC B, C and A when the residual cleansers were removed and then inoculated on the culture plate.
Resin plates adhering
Candida cells were soaked in the cleansers, and then the remaining cells were counted under the microscope. The removal of the adhering cells by DC A, B and C were significantly greater than that by the control. But DC D did not show any significant differences from the control and the other cleansers.
DC A exhibited the highest protease activity at pH 7. At the own pH of cleansers, however, DC C exhibited higher activity than DC A. The protease activity in DC B was lower than that in DC A and C. DC D exhibited no protease activity, but it generated the largest quantity of hydrogen peroxide. No hydrogen peroxide was generated from DC A.
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Yoshiaki Yamada
1991 Volume 35 Issue 5 Pages
1015-1027
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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Deterioration of tissue conditioners (TC) was assessed using nine kinds of commercially available TC. The weight of each TC, internal porosity, surface roughness, contact angle, antibacterial properties and adherence of bacteria immersion in 37°C water as a simulative intraoral environment. The effect of a coating agent on prevention of deterioration was also studied.
The surface of TC was roughened by immersion in water for one week. The weight also underwent changes. The antibacterial properties were lost by immersion in water. Immersion in a chemical-soak cleaner caused roughening of the surface to almost the same degree as did immersion in water. Application of the coating agent on TC was effective for prevention of roughening of the surface and change in weight. It also inhibited adherence of Candida albicans. However, adherence of Streptococcus mutans and Bacteroides gingivalis was increased. Thus, adherence of bacteria was not always inhibited.
These results suggested the relatively early deterioration of TC and the necessity of avoiding the excessively prolonged use of TC even when coated with a coating agent.
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Part 6. Maxillary Edentulous Simulation Model
Shunichi Kurosaki, Masatoshi Shimizu, Yoshihiko Moriya, Masahiro Yoshi ...
1991 Volume 35 Issue 5 Pages
1028-1034
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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A considerable amount of research on construction of the complete denture has been reported, used the simulation model as the edentulous aleveolar ridge.
The simulation model is required the approximation to the edentulous alveolar ridge on its morphology and caracteristic. Especially, the soft tissue as an impression objectives can be displaced under pressure so that the impression method has influenced on contour variations of the master cast. Therefore, pressure-displaceability is an important property.
In this study, the authors attempted to development the simulation model as the maxillary edentulous alveolar ridge and examined its efficiency.
The simulation model approximates to the maxillary edentulous alveolar ridge on its morphology. The model is presented, approximates to the pressure-displacement at the masticatory mucosa (alveolar ridge, palate) and lining mucosa. In the process of making impression, the model and any impression material is perfectly separated without the damage of the fine surfaces of the contacting parts and it never cause the electric leak during the study on bearing-stress of basal seat under the denture.
From the above results, the reliability of the model could be utilized as the maxillary edentulous alveolar ridge in order to study the impression method and the bearing-stress on basal seat under the denture.
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I-1. Application of Poly-Vinylidene Fluoride Film
Yasunobu Orii, Masatoshi Shimizu, Yoshihiko Moriya, Naoyuki Tsukakoshi ...
1991 Volume 35 Issue 5 Pages
1035-1044
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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In the study of stress bearing of basal seat under denture, there were various problems related to adjustment of the sensor to alveolar mucosa, especially when diaphragm pressure sensor was used. In order to both solve these problems and to develop the pressure measurment system in the oral cavity, the piezo film (poly-vinylidene fluoride film, PVDF) was investigated and some basic studies on its characteristics were made.
This PVDF is a thin film having piezo electricity. In this study, two experiments were conducted. In the first experiment, PVDF was placed between two flat metal plates. In the second one, PVDF was placed between two pieces of rubber mucosa of the same thickness. In both cases, the relation between vertical static load and output voltage was investigated under various conditions.
The results were following:
When the area of PVDF was thicker and larger, the output voltage per unit load become higher.
The voltage became higher when the rubber mucosa was thicker and the resin plate thinner.
In both experiments, more than 0.99 of correlation coefficient was obtained.
From the above results, it was suggested that PVDF could be utilized as pressure sensor to measure functional pressure and stress bearing of basal seat under denture.
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Shinji Satou
1991 Volume 35 Issue 5 Pages
1045-1052
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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The Articulation Quint proposed by R. Hanau has been used as a guiding principle of artificial teeth arrangement for providing complete dentures with full balanced occlusion. The quantitative relationship among its five factors, has yet to be clarified, however. Under full balanced occlusion, any facet of a given tooth has the same inclination as the gliding movement of its opposing member, suggesting that tooth movement is a main parameter for describing the afore-mentioned relations. We thus introduced an equation describing protrusive movement of the articulator, and then investigated the direction of this movement on the articulator, yielding the following results: 1) the direction of the movement changes in proportion to the horizontal position of the tooth; 2) vertical changes in tooth position have little influence on movement direction. From these results, we derived a linear equation approximately describing the functional relationship among the five factors involved in the Articulation Quint, which can be considered to be a quantitative expression of Thielemann's formula.
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Part 1. Dissolved Elements of Adlloy-OH in Saline and their Cytotoxic Effects
Sakari Hikage, Hiroki Ohno, Kunihiko Sakaguchi, Yoshibumi Iizuka
1991 Volume 35 Issue 5 Pages
1053-1059
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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Cytotoxicity of gallium-tin alloy (Adlloy-OH) was investigated using HeLa S 3 cells in vitro.
Five g of Adlloy-OH were immersed in 50ml of saline. The saline solution with Adlloy-OH incubated for 8 days at 37°C. The amount of gallium and tin dissolved in the solution was measured by a Atomic Absorption Spectrophotometer. The amount of tin in the solution was below the detectable limit. The detected corrosion rates of gallium in the solution was 6ng/mg alloy/day.
For cytoxicity study, the solution contained gallium was diluted in Eagle's minimum essential medium. The dilutions were added to cell suspension. The cells were cultured for 7 days in a incubator at 37°C. After cultuvation, cell number was determined using a Coulter Counter.
The cell survival of the 20-fold dilution, in which the concentration of gallium was 0.24μg/ml, was 94.1% of control cell number after 7 days of cultivation. The cell survivals of the 200-fold dilution and the 2000-fold dilution were 96.2 and 98.3% of control cell number. Moreover, the cells showed no change morphologically as well as untreated control. Those results suggested that Adlloy-OH had a slightly toxic effect on the HeLa cells.
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Influences of Postures on Maximum Exertable Forces and Consecutive Forces
Tohru Mitani, Teruta Maeda, Reitaro Takahashi, Kazunori Nishiura, Hiro ...
1991 Volume 35 Issue 5 Pages
1060-1064
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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Eight operators (four males and four females) were tested for maximum exertable manual forces (MFs) and six male operators for the variations of consecutive manual forces (CFs) of 2 kgf during 3 minutes without monitoring them. Both forces were exerted on the simulation model with bilateral hands in six different postures of prosthetic practices.
The results were as follows:
1. Significant differences on MFs were found between sexes (p<0.05), between sides (p<0.005) and between postures (p<0.001).
2. Significant factors on CFs were side (p<0.005), posture (p<0.001), time (p<0.001) and the side×time interaction (p<0.025).
3. These findings indicated that the optimum posture for force application on maxilla was seating behind the model with index and middle fingers, and the one on mandible was standing in front of the model and on the right side with thumb fingers.
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Harukazu Kanehira, Teruta Maeda, Akira Kawano, Iwao Takuma, Naoya Iked ...
1991 Volume 35 Issue 5 Pages
1065-1069
Published: October 01, 1991
Released on J-STAGE: August 10, 2010
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The purpose of this study was to investigate factors influencing mandibular position sense with four different jaw openings (5, 10, 15 and 20 mm from intercuspal position), Eight subjects memorized the reference positions with monitoring their spatial vertical jaw positions using a Mandibular Kinesiograph (M.K.G., K-5), Immidiately after memorizing one of those positions, they were required one of loaded conditions that were C1; clenching in I.C.P., C2; light teeth contact in I.C.P., C3; closing superior to memorized position (descending approach), C4: opening inferior to memorized position (ascending approach), C5; maximum widely open. Afterward, they were required the memorized position without monitoring again. Vertical distances from I.C.P. at lower incisal teeth were recorded by MKG and statistically analyzed.
The results were as followed:
1. Perceived mandibular positions in the descending approach (C1, C2, C3) were become significantly higher than in the ascending approach (C4, C5) on 10 to 20 mm reference positions (10 mm: P<0.05, 15 mm: P<0.01, 20 mm: P<0.01). On 5 mm reference position, however, it was no significant.
2. On 5 mm reference position, variance of data was significantly lower than the others (P<0.01).
3. In maximum open (C5) of five conditions, variance of data was significantly greater than the others (P<0.01).
4. It was suggested that mandibular position sense was affected by mandibular spatical vertical position and that the muscle spindle plays an important role in neuronal mechanism of controlling mandibular position.
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