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2004Volume 48Issue 3 Pages
331-333
Published: June 10, 2004
Released on J-STAGE: August 10, 2010
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Nobuo Ishihata
2004Volume 48Issue 3 Pages
334-342
Published: June 10, 2004
Released on J-STAGE: August 10, 2010
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[in Japanese]
2004Volume 48Issue 3 Pages
343
Published: June 10, 2004
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From the Past to the Future
Tooru Nagasawa
2004Volume 48Issue 3 Pages
344-353
Published: June 10, 2004
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Overdentures have been produced as prostheses, and will continue to be produced and used in the future. Generally, clinicians design dental prostheses, and which design is better cannot be known until the outcome is evaluated after several years. Overdentures have merits and demerits, which should be considered when designing overdentures. The necessity of retainers in overdentures varies among cases. Retainers are unnecessary in cases of maxillary overdentures in patients with sufficient alveolar ridge, whereas retainers are necessary when patients request roofless dentures due to discomfort in the palatal area. Magnetic attachments have replaced stud attachments that had been frequently used for overdentures. Magnetic attachments have their own advantages as mentioned already. In recent years, implant techniques have been improved and implantation has been applied to patients of a wide range of ages. A combined use of magnetic attachments with implants is prevalent. In particular, if implants can be inserted in the edentulous mandibular bone in patients with poor alveolar ridge conditions, it will be advantageous to the patients. Furthermore, if implant dentures can be retained by magnetic attachments, it will be best. In the future, overdentures with a combined use of implants and magnetic attachments will be widely used.
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Eiichi Nagaoka
2004Volume 48Issue 3 Pages
354-371
Published: June 10, 2004
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Purpose: An overdenture is a kind of removable partial denture that utilizes remaining natural teeth as abutment teeth. Therefore, it is important to control forces affecting the abutment teeth and the edentulous ridge in the application of overdentures. This paper discusses the methods of treating the abutment teeth.
Study Selection: In force control, it is important to protect the periodontal tissues and edentulous ridges from the forces transmitted by the teeth and the dentures. The periodontal tissues can reduce the harmful lateral force acting on the abutment teeth by lowering the point onwhich the force acts, and the edentulous ridges affected by bone resorption require load reduction bymaking the abutment teeth support the denture. The point of force action is lowered by reducing thecoronal length of the abutment in overdenture application. However, improvement of the crown-root ratio alone cannot lessen the lateral force. Focusing on these principles in overdenture application and methods of treating the abutment, clinical cases and the results of studies associated with these cases are presented.
Results: Improvement of the crown-root ratio, which is useful to reduce the lateral force, is not always effective and may make it more difficult to control the force in those cases having an inclining tooth or a tooth with a curved root.
Conclusions: To control the force using methods appropriate to the status of the abutment teeth, thorough examination and accurate diagnosis for the selection of abutment teethare required.
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What Is Solved and What Isn't
Akira Manabe
2004Volume 48Issue 3 Pages
372-383
Published: June 10, 2004
Released on J-STAGE: August 10, 2010
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The advantages of overdenture treatment, which is mainly used for patients withonly a few remaining teeth, are that it improves the crown root ratio and easily corrects the occlusal plane. However, there are some disadvantages, which are related to leaving roots of natural teeth andcoverage of the entire occlusal surface of the root. Although the life of the abutment roots will be prolonged, it is difficult to make an accurate estimate of the prognosis of the remaining teeth. Based on clinical experience, the author suggests the following solutions: 1. For loosening of root caps, use adhesive resin cement. 2. For fracture of dentures, make an adequate design of the reinforcement. 3. For caries and periodontal disease, use an automatic toothbrush and perform professional mechanical tooth cleaning (PMTC). However, there are many overdentures with questionable design for the life of abutment roots, so it is important to distinguish definitive prostheses from transitional overdentures. Malhabits and occlusal forces of patients will have some effects on the prognosis of the remaining teeth. Further studies are required to control the forces and prognosis of the abutment roots.
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Jiro Araki, Takumi Ogawa, Yuhko Shigeta, Yuhko Hitomi, Shinya Hirai, S ...
2004Volume 48Issue 3 Pages
384-393
Published: June 10, 2004
Released on J-STAGE: August 10, 2010
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Purpose: This study investigated morphological changes to occlusal facets and contact areas over a 30-year period in one subject.
Methods: Occlusal facets and contact areas at intercuspal and eccentric mandibular positions were recorded using a silicone impression material (Bite checker, GC) when the patient was 25, 39 and 55 years old.
Results: The number of occlusal facets and contact areas in the intercuspal position increased with age, particularly at the molars. Contact areas in the most retruded contact position were predominantly found at the second molar in all stages. The number of contact areas in the protrusive movements decreased with age at the anterior teeth and the premolars, but increased at the molars.
The number of working-side contact areas in the lateral movement to the right side did not indicate any obvious tendencies with age, but the corresponding number in the lateral movement to the left side increased gradually. Conversely, the number of balancing-side contact areas at the molars in 1-2 mm lateral positions from the intercuspal position on the both sides increased with age and was substantially larger than on the working-side.
Conclusions: Morphological changes to occlusal facets over a 30-year period in the subject were cosiderably extensive at the molars, and in particular, contact areas in the intercuspal position had an influence on the occlusal facets.
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Yuji Tsubota, Nao Fukagawa, Yasushi Nishimura, Eriko Ando, Koh Hashimo ...
2004Volume 48Issue 3 Pages
394-403
Published: June 10, 2004
Released on J-STAGE: August 10, 2010
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Purpose: A survey was performed in 2001 in order to grasp the actual condition regarding methods and materials of foundation restorations. The results of 3 surveys in 1977, 1986, and 1993 were compared.
Materials and Methods: All abutment teeth and core buildup that were treated by foundation restoration at Tsurumi University Dental Clinic Prosthodontics Treatment Room were set as the survey target from February to April 2001. The survey items were patients, abutment teeth, and data of core buildup.
Results: Core buildups of 311 teeth of 225 patients were examined. In all abutment teeth, there were 5% of vital teeth and 95% of non-vital teeth. There were many abutment teeth with little remaining tooth structure. Regarding type of core buildup, cast metal core buildups were chosen by 61% and composite resin core buildups were chosen by 39%. In composite resin core buildups, the indirect method was performed in 70% and the direct method was performed in 30%. As for luting cement, adhesive resin cement was chosen by 71% at the time of cast metal core buildup. Sand blast process ing was performed before setting in 83% at the time of cast metal core buildup. And at the time of use, 97% used an adhesive metal primer for the adhesive resin cement.
Conclusions: Compared with the results of the 3 previous reports, this survey showed that many composite resin core buildups and adhesive resin cement of adhesive material were chosen. Reliable dentin adhesion can be used for dislodgement or root fracture.
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Minoru Kawaguchi, Yutaka Takahashi, Koji Miyazaki
2004Volume 48Issue 3 Pages
404-412
Published: June 10, 2004
Released on J-STAGE: August 10, 2010
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Purpose: The amount of leached plasticizers (phthalate esters) for commercially-available tissue conditioners immersed in various immersion media (distilled water, 5% and 10% ethanol) was measured to investigate the leaching and intake behavior.
Methods: Six disk-shaped specimens were immersed in each immersion medium for 14 days. Leached phthalate esters in each immersion medium were measured by high-performance liquid chromatography at days 1, 3, 5, 7, and 14. From the leaching behavior of phthalate esters in each immersion medium, the effect of these media on the amount of leached phthalate ester was investigated.
Results: For three kinds of phthalate ester (dibutyl phthalate: DBP, butyl phthalyl butyl glycolate: BPBG, butyl benzyl phthalate: BBP), immersion in the ethanol aqueous solution increased the amount of leached phthalate esters. The total amount of leached phthalate esters in 10% ethanol aqueous solution was approximately 1.7-2.3 times higher than that in distilled water. Leaching of phthalate esters increased with longer immersion duration for up to 14 days. The chemical structure of these phthalate esters significantly affected their leaching behavior. Phthalate ester, BBP, containing a hydrophobic aromatic ring in the backbone, showed a lower amount of leaching than the others.
Conclusions: The leaching behavior of phthalate esters for tissue conditioner was dependent on the chemical structure, and the solubility of immersion medium with phthalate esters.
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Influence of Cervical Margin Forms on the Metal Coping Formation
Hisaka Shiratsuchi, Futoshi Komine, Hiroyasu Koizumi, Toru Muramatsu, ...
2004Volume 48Issue 3 Pages
413-422
Published: June 10, 2004
Released on J-STAGE: August 10, 2010
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Purpose: This study evaluated the influence of different cervical margin forms onthe adaptation and the thickness of the electroformed metal coping.
Methods: Master and replicated dies were fabricated from three steel dies that were prepared for a full-baked type metal-ceramic restoration of a maxillary central incisor. Three cervical margin forms were used: shoulder, round shoulder and deep chamfer preparation (S type, RS type, DC type). Metal copings were electroformed to an identical thickness at a corresponding place in the electroplating bath. After trimming the margin, the marginal discrepancy was measured at four points (a, b, c, d) each 90 degrees from the labial center of the metal coping on the master die. All specimens were embedded in acrylic resin and sectioned. The internal gap and the thickness of metal coping were measured at six points (A: labial marginal area, B: labial line angle of chamfer or shoulder, C, D: labial, lingual axial surface 1.0 mm from the abutment margin, E: ingual line angle of chamfer or shoulder, F: lingual marginal area). A laser microscope was used for the measurement and each group had five specimens. The measured values were analyzed statistically using the Kruskal-Wallis test and Bonferroni Correction. A significance level of p<0.05 was used for all comparisons.
Results: Regarding the marginal discrepancy at all measured points, the S type exhibited significantly poor values as compared with the DC·RS type. The internal gap of the S type was significantly poorer than that at A, B or F. The thickness of the S type was significantly thinner than that at B and E. The mean thickness of the S type was 51.2μm at B, 56.3μm at E.
Conclusions: This study confirmed that the cervical margin form influenced the metal coping formation manufactured using electroforming.
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Mitsutoshi Narita, Koh-ichi Kuremoto, Hiroshi Inoue
2004Volume 48Issue 3 Pages
423-432
Published: June 10, 2004
Released on J-STAGE: August 10, 2010
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Purpose: We previously reported that the mandibular motion occurs within antero-posterior and lateral ranges of about 40μm during intercuspation. This study investigated the influence of tooth clenching and muscle fatigue on mandibular position and fluctuation.
Methods: The mandibular position was measured in 11 subjects with natural dentition. We performed the experiments under three conditions: a) subjects occluded their teeth without clenching in the intercuspal position for more than 30 seconds as a control; b) subjects clenched in the intercuspal position for more than 30 seconds (tooth clenching); c) subjects occluded without clenching in the intercuspal position for more than 30 seconds immediately after condition b (muscle fatigue). The experiments were repeated three times and we measured the antero-posterior and lateral displacements of mandibular position and antero-posterior and lateral ranges of mandibular fluctuation in each condition. Data obtained were analyzed using ANOVA [variable factors: individuals (n=11), conditions (n=3), repetitions (n=3)].
Results: The mandible was significantly displaced more anteriorly and laterally while clencing and during muscle fatigue than that under the control condition. The antero-posterior range of mandibular fluctuation was significantly larger while clenching and during muscle fatigue than that under the control condition. However, the lateral range of mandibular fluctuation did not show any significant difference among the three conditions.
Conclusions: These results indicate that the condition of jaw-closing muscles, tooth displacement and periodontal sensation caused by tooth clenching have significant effects on mandibular displacement and fluctuation. However, the condition of intercuspation and deformation of the mandible have little effect on mandibular displacement and fluctuation.
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Keisuke Nishigawa, Toyoko Satsuma, Shuji Shigemoto, Eiichi Bando, Masa ...
2004Volume 48Issue 3 Pages
433-440
Published: June 10, 2004
Released on J-STAGE: August 10, 2010
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Purpose: The objective of this research was to develop a new method to create a functional occlusal surface that requires least intra-oral occlusal adjustment. A new six-degree-of-freedom articulator consisting of a jaw tracking device and six-axis micro-positioning stage was used for this purpose.
Methods: A young female patient who planned to have a full veneer crown restoration on the upper left first molar was used as the subject. Jaw movement of the subject was recorded with the sixdegree-of-freedom jaw tracking device (BS-3) and reproduction of the recorded jaw movement data was performed with a HEXAPOD six-axis parallel kinematics robot.
Results: Working cast models were mounted on the six-degree-of-freedom articulator. An occlusal table with FGP wax was attached on the abutment tooth of the working model and jaw movement reproductions were performed to create a functionally generated path on the occlusal table. Some of the jaw movement data exhibited deeper biting jaw positions than the maximum inter-cupal position. Slight deformation of dentition during functional jaw movement seemed to cause these jaw positions. The occlusal table with functionally generated occlusal surface was used for taking the wax pattern of the full veneer crown. In this subject, intra-oral occlusal adjustment was not necessary for setting the finished full veneer crown.
Conclusions: A six-degree-of-freedom articulator that reproduces jaw movement with a working cast model was used to fabricate a full veneer crown on the upper left first molar of a patient.Reproductions of the patient's jaw movements were performed to create the functionally generated occlusal surface of the full veneer crown. This new technique was successfully used to create a dental prosthesis that required least intra-oral occlusal adjustment.
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A Review of Literature: Käyser's Shortened Dental Arch Concept
Taro Kanno, Hideaki Hirooka, Kohei Kimura
2004Volume 48Issue 3 Pages
441-456
Published: June 10, 2004
Released on J-STAGE: August 10, 2010
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Purpose: There has been no systematic clinical study of the scientific evidence of replacing missing teeth. We suggest that the number of teeth being replaced should not only be decided from morphologic and dynamic viewpoints, but also from a diverse viewpoint.
Study Selection: To prove the suggestion, a series of research of Kayser (Netherlands) advocating the Shortened Dental Arch (SDA) Concept is reviewed.
Results: Kayser et al. reported that there were no significant clinical differences between a SDA of 3-5 occlusal units (one molar unit is considered to be equivalent to two occlusal units) and a complete dental arch in the migration of teeth, masticatory ability, TMD, periodontal support, and oral comfort. Therefore, it was proposed that the anterior and premolar regions should always get the best quality care throughout life. In long-term longitudinal clinical studies, the SDA group indicated minor changes of the criteria on occlusal stability, however, the occlusal relationship remained stable in the evaluation period. As a result, the studies suggested that the changes were adaptation leading to a new equilibrium and SDA did not result in occlusal collapse.
Conclusions: From this review of literature, it was revealed that the SDA Concept might be a dental therapy validated by the scientific evidence. Consequently, a strategy to reduce complex restorative treatment in the molar area may be accepted.
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Tsukasa Watanabe
2004Volume 48Issue 3 Pages
457-460
Published: June 10, 2004
Released on J-STAGE: August 10, 2010
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Patient: Since the retention of existing dentures had decreased, the patient visited the clinic for fabrication of new dentures. The existing denture lacked retention with advanced flabby-gum tissue in maxilla and severally absorbed mandible.
Discussion: In order to control subsidence of denture by occlusal force, especially with flabby-gum tissue, it is important to concentrate occlusal force on the stable membrane supporting area to avoid vertical and horizontal dislodgement of dentures.
Conclusion: As a result of appropriate distribution of occlusal force by considering impression taking, inter-occlusal record and tooth arrangement, stability and satisfaction with the new dentures were obtained.
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Taira Kobayashi
2004Volume 48Issue 3 Pages
461-464
Published: June 10, 2004
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Patient: The object of the case is to allow continuing use thought repairing using the magnetic attachment to the Kounus applied prosthesis caused retentive failure with a lapse of 10 years after insertion for excellent use of another 3 years.
Discussion: As patients probably recognize the long-term use of the prosthesis as a bodily organ, it is more frequent that they hope its continuing use. However, it is not easy to repair the Kounus prosthesis since its retentive force was lost.
Conclusion: It is considered that application of the magnetic attachment is of great value as a technique possible to repair and there by using this prosthesis continuously.
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Mikako Tanaka
2004Volume 48Issue 3 Pages
465-468
Published: June 10, 2004
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Patient: The patient was a 16-year-old female patient with bilateral cleft lip and palate (Bi-CLP), and three upper incisors congenitally missing.Her maxilla was remarkably underdeveloped, and the alveolar ridge of the cleft region was in a collapsed state.
Discussion: Before orthodontic treatment, it was considered impossible to adapt a fixed bridge for this patient, but the patient desired fixed-bridge treatment nevertheless. The prosthodontist suggested the necessity of initial orthodontic and surgical treatment (bone graft and tooth transplantation onto the residual cleft ridge), in preparation for subsequent fixed-bridge treatment. The graft and transplantation were successfully performed, a fixed bridge was adapted to the patient's new intraoral environment, and she was satisfied with the esthetic and functional results of the treatment.
Conclusion: This study shows that prosthodontic advice at an early stage in diagnosis can be significant in adequately treating CLP patients.
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Tsutomu Kudo
2004Volume 48Issue 3 Pages
469-470
Published: June 10, 2004
Released on J-STAGE: August 10, 2010
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Hajime Shirai
2004Volume 48Issue 3 Pages
471-472
Published: June 10, 2004
Released on J-STAGE: August 10, 2010
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2004Volume 48Issue 3 Pages
473-474
Published: 2004
Released on J-STAGE: November 26, 2010
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