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[in Japanese], [in Japanese]
2003 Volume 47 Issue 2 Pages
243
Published: April 10, 2003
Released on J-STAGE: August 10, 2010
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Takao Kawasaki, Yoshiyuki Takayama
2003 Volume 47 Issue 2 Pages
244-252
Published: April 10, 2003
Released on J-STAGE: August 10, 2010
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It is well known that endodontically treated teeth are easily broken. However, countermeasures have not been established, and there are cases where the resin core is recommended or the reinforcement of the root canal by the cast core is recommended.
Purpose: This paper examines therapies for protecting endodontically treated teeth.
Study selection: We selected in vitro studies from 1997 to 2002 and in vivo studies. We used threedimensional finite element analysis to analyze the force distribution in posts and cores. For the analysis, we prepared three types of Young's modulus of periodontal ligament, anterior tooth and premolar.
Results: There was little equivalence with the organism in most research. The reports, however, suggested that the fracture strength of the whole system decreases with increasing elasticity of the post. A comparison of the resin core and cast metal core did not show which was the more useful.
Conclusions: Although there have been few papers describing opinions based on scientific reasoning, the following conclusions were drawn. 1. There is no basis for claiming whether a metal or resin core is excellent. 2. Selected application is not required in a cast core or resin core, because there is no difference at the Young's modulus between a cast post and prefabricated metal post. 3. A tapered cast post and core may cause tooth fracture. The bulk of dentin is important for the strength of endodontically treated teeth.
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Ikumi Shiozawa
2003 Volume 47 Issue 2 Pages
253-260
Published: April 10, 2003
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Post-and-core restorations are applied when non-vital teeth are restored with crowns or bridges. The post-and-core restoration systems are divided into two methods, cast core and resin core. However, there is no clinical standard for selecting the cast core or the resin core, and a different method is sometimes chosen even when the same case is restored. In this paper, the features, selection standard and proper use of the cast core and the resin core were considered. The author thought that there is no problem in using the cast core for most cases, because it is excellent in intensity, conformity, and reliability. Moreover, troubles originating in post-and-core restoration were examined. It was clarified that the ratio of the clinical crown part (which includes the post part which has a large taper in the wearing direction of the post) and the clinical post part (which is the remaining post part) affected dislodgement of the post-and-core restoration. Key words post-and-core restoration, casting core, resin core, dislodgement of post-and-core
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Shunji Fukushima
2003 Volume 47 Issue 2 Pages
261-271
Published: April 10, 2003
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In daily practice, both cast cores and composite resin cores are used as core materials, though the latter may be with or without a prefabricated metal post. The composite resin core material has been improved and now has the ability to adhere not only to enamel but also to dentin. In addition, the metal post does not reinforce a tooth and therefore can be used only when it is essential for retaining a core. In this sense, it is not important whether the metal is cast or prefabricated. Question 1 (Q1) from the editor is whether there are special cases for cast cores or composite resin cores and Question 2 (Q2) is, if yes, to cite some instances for both cores. My answer to Q1 is yes, in cases where metal posts are not necessary, because such cases can be restored with composite resin only. On the other hand, if the cases necessitate posts, it is difficult to distinguish one from the other, at least in mechanical terms. However, such distinction is possible in clinical terms, because there are several merits of prefabricated metal post and composite resin cores, including reduction of time and cost. These are my answers to Q2. Question 3 ask me to express my opinion regarding clinical ways for preventing troubles such as dislodgement of post and cores and root fracture. Therefore, I propose several guidelines for classifying tooth factors and other factors.
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Yuki Saitoh
2003 Volume 47 Issue 2 Pages
272-281
Published: April 10, 2003
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Purpose: Absorption of the alveolar bone following the loss of teeth causes high absorption and reduction of the edentulous ridge hinders the recovery of stomatognathic function such as masticatory function, pronunciation and esthetics, and has a considerable influence on the maintenance and stability of the denture base after prosthesis. Therefore, control of absorption or reconstruction of alveolar bones after the loss of teeth is an important issue for the recovery of stomatognathic function. We made a hybrid body of hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP) granulation and polyelectrolyte complex (PEC)(HAP-PEC, β-TCP-PEC hybrid body) and carried out an experimental study using adult dogs in order to prevent diffusion and leakage of biomaterials by using PEC and to develop bone paste for early bone reconstruction.
Methods: After making osseous defects in the mandibular bone of adult dogs, we filled the osseous defects with HAP-PEC, β-TCP-PEC hybrid bodies, and compared and examined them in two, four and six weeks, based on roentgenographic and histological findings.
Results: In the roentgenographic finding, diffusion or leakage of granulation was not observed in these hybrid bodies. In the histological finding, an increase in the formation of bone regeneration in each hybrid body was observed at two, four and six weeks, compared with the control, and increase was greater. At six weeks, the osseous defects had nearly recovered to the original form. An absorption image of granulation was also observed in the β-TCP-PEC hybrid bodies in the six-week cases.
Conclusions: It was suggested that the HAP-PEC, β-TCP-PEC hybrid body is extremely effective for the reconstruction of jaw bone.
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Satsuki Yamamoto, Hiroshi Inoue
2003 Volume 47 Issue 2 Pages
282-291
Published: April 10, 2003
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Purpose: We measured dopamine release from the prefrontal cortex of rats with occlusal interferences in order to clarify the relation between the occlusal interferences and psychiatric stress. Changes in the activity of the dopaminergic neuron system of the prefrontal cortex have been found to be an index of stress responses involved in anxiety and so on. Since it is difficult to measure anxiety in animal experiments, we used benzodiazepine (diazepam) in this experiment to determine whether increased dopamine release was caused by psychiatric stress.
Methods: Dopamine release was measured using microdialysis in three experiments. In each experiment, the control group comprised 6 rats and the occlusal interference group comprised 6 rats. The level of dopamine release was measured for each experiment: We measured it before and after feeding pellets in experiment 1. Diazepam was intraperitoneally administered before the rats were fed pellets in experiment 2. Physiological saline was given to the rats before they were fed pellets in experiment 3.
Results: Experiment 1: In the occlusal interference group only, the amount of dopamine release significantly increased after feeding. Experiment 2: The amount of dopamine release did not significantly increase in either group. Experiment 3: In the occlusal interference group only, the amount of dopamine release significantly increased after feeding.
Conclusions: The amount of dopamine release increased by occlusal interference i the rats that had been fed. Diazepam suppressed this increase, but physiological saline did not. These results proved statistically that occlusal interferences related to psychiatric stress involving anxiety.
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Satoshi Ino, Minoru Toyoda, Tadashi Niiya, Toshihiko Tamura, Takeshi S ...
2003 Volume 47 Issue 2 Pages
292-300
Published: April 10, 2003
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Purpose: This study investigated the effect of silica coating (Rocatec
®-System, ESPE) on the bonding strength of veneering composite resin to dental alloys.
Methods: Four kinds of alloy (Pt-Au, Co-Cr, Au-Ag-Pd, and pure titanium, size: 10×15×2 mm) were ground (# 600), and divided into three groups: alumina sandblasted group (Rocatec ®-Pre, SB), alumina sandblasted and adhesive primed group (Metal Primer II, GC, MP), and silica coated group (Rocatec
®-Plus, RP). Specimens for all groups were analyzed with SEM images (JSM-6301 F, Nihon Denshi) and the density of Si element with EPMA (EPMA 8705, Shimadzu). The shear bond strengths of composite resins (Solidex
®, Shofu) to alloys of ten specimens each were measured (Cross head speed: 1.0 mm/min). Failure loads were examined by one-factor ANOVA (Post-hoc test: Scheffé's F, α=0.05).
Results: From the images and EPMA evaluation, the silica layer was recognized on all alloys and remained intact after ultrasonic cleaning. MP and RP showed significantly higher shear bond strengths than SB for every alloy. In the case of Pt-Au, RP showed significantly higher strengths than MP. However, in the case of Co-Cr, Au-Ag-Pd and titanium, there was no significant difference between MP and RP.
Conclusions: According to the results of this study, Rocatec
®-System forms a firm silica layer and improves the surface for bonding of dental alloys.
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Tatsuya Hikosaka, Norihiko Mizutani, Yoshinobu Tanaka, Kazumoto Hoshia ...
2003 Volume 47 Issue 2 Pages
301-310
Published: April 10, 2003
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Purpose: Titanium and titanium alloys offer excellent biocompatibility and are widely used for prostheses and implant materials. However, usage in the oral cavity subjects the alloys to a very corrosive environment. In this experiment, the corrosion resistance of Ti-29 Nb-13 Ta-4.6 Zr alloy, which was recently developed, was comparatively evaluated with existing materials.
Method: Three kinds of alloy were used as plate specimens, Ti, Ti-6 Al-4 V alloy and Ti-29 Nb-13 Ta-4.6 Zr alloy. As test solutions both 0.9% Na Cl and 0.1 mol/l Na F solution were used. Each test piece was soaked for 3, 7 and 14 days. The color difference (ΔE) was analyzed using a Colorimeter, and the rest potential and anodic polarization curve were measured. Surface analysis of the samples was carried out using a scanning electron microscope and X-ray diffraction equipment.
Results and Conclusions: In the 0.1 mol/l Na F solution, the color difference after immersion of the Ti-29 Nb-13 Ta-4.6 Zr alloy for 14 days showed a large value 17.7, but no significant difference was recognized with Ti. The natural electrode potential of Ti-6 Al-4 V alloy was the lowest. The increase of the current density near 1.5 V of the Ti-29 Nb-13 Ta-4.6 Zr alloy was slight for the anodic polarization curve. The value of the current density showed the lowest among the three kinds of alloy at 5 V. From the above result, it is suggested that the Ti-29 Nb-13 Ta-4.6 Zr alloy showed better corrosion resistance than either Ti or Ti-6 Al-4 V alloy in the fluorine solution.
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Norio Ohnuma, Tomoyuki Ohnuma, Miwa Maruya, Kimio Shimizu, Setsuo Arai ...
2003 Volume 47 Issue 2 Pages
311-315
Published: April 10, 2003
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Purpose: This study investigated the effects of wearing a laminate mouth guard on static balance with the eyes closed.
Methods: The subjects were eleven males with healthy complete dentition. Body sway in the upright posture with the eyes closed was determined by using the High-Reso Mat System under two conditions: 1) a position of slight occlusal contact when wearing a laminate mouth guard, and 2) the intercuspal position when not wearing a laminate mouth guard. The standard deviation of lateral components (X-S.D.) and that of anterior-posterior components (Y-S.D.), and the migration distance of center of gravity were measured. Differences between the two conditions were statistically analyzed by using Wilcoxon signed ranks test.
Results: The respective median and interquartile of X-S. D., Y-S. D. and migration distance of center of gravity were 0.19 (0.13) cm, 0.12 (0.10) cm and 9.54 (3.90) cm when wearing the mouth guard, and were 0.19 (0.11) cm, 0.11 (0.11) cm and 10.19 (4.68) cm when not wearing the mouth guard. Statistical test revealed no significant difference between these two conditions for any of the measurement items.
Conclusions: From these results, wearing a laminate mouth guard did not have a significant influence on static balance with the eyes closed.
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Yu Ogawa
2003 Volume 47 Issue 2 Pages
316-325
Published: April 10, 2003
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Purpose: To establish the electromyogram (EMG) biofeedback threshold for a patient with masticatory muscle pain under a natural environment, various thresholds that differentiate the parafunctional activities from functional ones were determined.
Methods: Thirty-four healthy, natural-dentition subjects (18 males, 16 females; mean age, 26.6± 2.7 years old), having no temporomandibular disorder symptoms, were recruited for this study. By means of a newly developed one-channel portable EMG recording device, surface EMG from the unilateral temporal muscle was recorded for 5 hours, under a natural environment. At the beginning and the end of the recording period, EMGs of functional activities (gum chewing and rice cracker consumption), and parafunctional ones (clenching at 10, 30, 50% of maximum bite force; MBF), were recorded. Bite force was regulated by visual feedback from the indicator of a bite force meter. Various combinations of EMG activity (10, 20, 30% of maximum voluntary contraction in RMS value) and EMG duration (1-9s) were determined for recorded EMGs of functional and parafunctional mandibular movements.
Results: The thresholds set at the beginning of the recording were applicable even at the end of the recording under clenching at 10, 30 and 50% MBF, to differentiate from the functional activities in 25 (73.5%), 30 (90.9%), and 30 (90.9%) subjects, respectively.
Conclusions: The results of this study support the rationale of utilizing EMG activity together with a certain period of duration as a threshold for biofeedback training for the patient having clenching behavior.
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Initial and 3-year Subsequent Recording Comparison
Shin Sato, Masanori Fujisawa, Takuya Suzuki, Kiyotaka Kanemura, Akiko ...
2003 Volume 47 Issue 2 Pages
326-334
Published: April 10, 2003
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Purpose: To ascertain the reproducibility and reliability of mandibular movement as one of the parameters reflecting mandibular functions, mandibular movements were recorded at different time points over three years for the same subjects.
Methods: For twenty-seven healthy volunteers (20 males and 7 females, average age 20.4±2.4 years old) without past or current history of temporomandibular disorder (TMD), border mandibular movement and habitual open-close jaw movements were recorded with a six-degree-of-freedom jaw tracking device. Three years later, identical movements that the subjects had initially been instructed to perform were recorded again for the same subjects, and the translational distance at the incisal and condylar points were compared.
Results: Neither the distance parameters of protrusive and lateral excursion nor open-close movement showed any statistically significant difference between the initial and subsequent records (paired t-test). Although five subjects eventually revealed TMD symptoms during the three-year-period, there was no distinctive parameter that predicted the symptoms from the initial data.
Conclusions: Since mandibular movement is thought to be a reliable parameter in non-TMD subjects, mandibular movement recording has been confirmed to be of use to evaluate the functional changes. However, it is difficult to predict possible changes in mandibular function from mandibular movement analysis alone.
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Shuichiro Yamashita, Takanao Kirihara, Yoshimasa Igarashi, Minoru Ai
2003 Volume 47 Issue 2 Pages
335-342
Published: April 10, 2003
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Purpose: This study investigated the locations of occlusal tooth contacts at the mandibular retruded contact position and discusses their meaning for the stomatognathic system.
Materials and Methods: Two hundred and eighty-three healthy subjects without symptoms of temporomandibular disorders were selected for this study. One expert operator guided their mandibles backward and checked tooth contacts at this position using thin articulating papers. Occlusal side, frequency of contact on each examined tooth, and number of occluded teeth were evaluated.
Results: 1. The ratio of the number of subjects between bilateral contacts and unilateral contacts was approximately six to four. 2. Tooth contacts on the first premolar and the second molar were frequently observed. 3. The number of occluded teeth was less than two in 80 percent of subjects. 4. The number of subjects classified as the incisor and canine group, the premolar group, and the molar group accounted for more than 70 percent of the total. In the combined group, there was a bilateral contact pattern between the premolars on the one side and the molars on the other side.
Conclusions: It was revealed that the first premolar and the second molar were key teeth as guides for posterior excursion of the mandible. These occlusal sites were clearly specific in the dental arch, and pairing of occlusal sites showed a simple diagonal line even in the bilaterally combined group.
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For Patients Having No Complaint in Temporomandibular Joint
Yasuko Takayama, Norio Takishin, Toshio Hosoi, Masao Yuasa, Kaoru Koba ...
2003 Volume 47 Issue 2 Pages
343-352
Published: April 10, 2003
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Purpose: Using panorama radiographic findings taken for observing the teeth and periodontal tissue for patients having no complaint in temporomandibular joint, the prevalence of bone changes in the condyle was investigated to evaluate the relationship between bone changes in the condyle and age, gender, types of dentition, and occlusal support.
Materials and Methods: The subjects were 970 referred patients aged over 25 years, whose panorama radiographic findings were taken between December 1999 and March 2000 at the Department of Oral Radiology, Tsurumi University Dental Hospital. With regard to the bone changes in the condyle, erosion, osteophyte, and deformity were evaluated. The relationship between bone changes in the condyle and age, gender, types of dentition, and occlusal support (according to Eichner classification) were also evaluated.
Results: Bone changes were noted in 113 (11.6%) of the 970 patients, showing a significantly higher prevalence in females than in males (females 14.4%, males 7.8%). In females, the prevalence of bone changes showed no significant differences in age, types of dentition, and occlusal support. In males, the prevalence of bone changes showed increases according to decreases in occusal support and over 65 years. With regard to the findings of bone changes in the condyle, deformity was most frequently observed. Deformity and erosion were more prevalent in younger groups, and osteophyte was more common in older groups.
Conclusions: Bone changes in the condyle were confirmed in 11.6% of patients, and the influence of gender on the bone changes was highest among the examined factors.
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Akihiko Saika, Tetsuo Ichikawa, Yoritoki Tomotake, Hideo Kanitani, Sei ...
2003 Volume 47 Issue 2 Pages
353-360
Published: April 10, 2003
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Purpose: Misfit of superstructure-supported osseointegrated implants causes adverse stress in the prosthesis, components, and surrounding bone. A passive fit of the implant-supported prosthesis is essential for successful long-term osseointegration. Various clinical methods for evaluating the fit of implant-supported prostheses have been suggested. However, the methods have little scientific evidence to determine the acceptable fit. The present study evaluated the misfit of implant-supported prostheses by measuring the rotational angle/tightening torque in screwing the prosthesis on master models.
Materials and Methods: Twenty-four implant-supported prostheses (3 single standing, 20 fixed partial, 1 full bridge) of fourteen patients were evaluated using a custom-made rotational angle/ tightening torque measuring apparatus on the master models. The influence of the order of tightening and unit number on the value was also evaluated.
Results: The mean of the rotational angle/tightening torque was 2.6 (SD: 0.6) degree/Ncm in all prostheses. The value was significantly higher than that in the abutment screw as a control. The order of tightening and unit number did not significantly affect the values.
Conclusions: The results suggest that measurements of rotational angle/tightening torque be useful for evaluating the fit of implant-supported prostheses. Misfit of the prostheses was below the level of acceptable fit.
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Yoshifumi Miura
2003 Volume 47 Issue 2 Pages
361-362
Published: April 10, 2003
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Koji Kobayashi
2003 Volume 47 Issue 2 Pages
363-364
Published: April 10, 2003
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Naoki Sakurai
2003 Volume 47 Issue 2 Pages
365-366
Published: April 10, 2003
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Masahiro Suzuki
2003 Volume 47 Issue 2 Pages
367-368
Published: April 10, 2003
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Yoko Murata
2003 Volume 47 Issue 2 Pages
369-370
Published: April 10, 2003
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Masataka Hama
2003 Volume 47 Issue 2 Pages
371-372
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Kenji Tsubota
2003 Volume 47 Issue 2 Pages
373-374
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Fujio Suzuki
2003 Volume 47 Issue 2 Pages
375-376
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Akihiro Kuroiwa
2003 Volume 47 Issue 2 Pages
377-378
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Seiichi Kita
2003 Volume 47 Issue 2 Pages
379-380
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Hidenori Sajima
2003 Volume 47 Issue 2 Pages
381-382
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Seiya Tanaka
2003 Volume 47 Issue 2 Pages
383-384
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Koji Kamada
2003 Volume 47 Issue 2 Pages
385-386
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Kohyoh Soeno
2003 Volume 47 Issue 2 Pages
387-388
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Yohsuke Taira
2003 Volume 47 Issue 2 Pages
389-390
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Tsutomu Daian
2003 Volume 47 Issue 2 Pages
391-392
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[in Japanese], David A. Felton, [in Japanese], [in Japanese], [in Japa ...
2003 Volume 47 Issue 2 Pages
393-413
Published: April 10, 2003
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