[in Japanese]

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[in Japanese]

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[in Japanese]

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Purpose: To characterize the flexural properties of various commercial thermoplastic resins for non-clasp dentures.
Methods: Four different commercial thermoplastic resins for non-clasp dentures (polyamide resin: Lucitone FRS, polycarbonate resin: Reining, polyester resin: EstheShot, and acrylic resin: Acrytone) and thermally polymerized acrylic resin (Acron) as a control were used in this study. A three-point bending test of two types of test piece: one in the state as molded (drying type) and the other in the state as soaked in water for 30 days after molding (soaking type) was performed for plotting the stress-strain curve and calculating the flexural strength, flexural modulus, and 0.05% proof stress. Comparisons between the drying and soaking types in each resin as well as between different resins were performed based on the obtained data.
Results: The stress-strain curve revealed the brittleness of Acron as a control and the toughness of all thermoplastic resins for non-clasp dentures. The flexural strength of all but Reining was significantly lower than that of Acron. The flexural modulus of all of them was significantly lower than that of Acron. The 0.05% proof stress of EstheShot was significantly higher than that of the others. The flexural strength, flexural modulus, and 0.05% proof stress of Acrytone were significantly lower in the soaking type than in the drying type.
Conclusions: These results suggested that the flexural property of each material was dependent on the property of the resin to be used. Sufficient considerations are required with an understanding of the basic physical properties of the thermoplastic material to be used when selecting and designing non-clasp dentures.

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Purpose: The Japan Prosthodontic Society (a public interest incorporated association) proposed a new diagnostic nomenclature system method that is based on pathogenesis and etiology for providing adequate prosthodontic treatment to patients. This diagnostic nomenclature system is based on “factor” and “disability”, and assumes that a disability is caused by a factor. The aim of this study was to analyze the reliability and validity of several dentists’ diagnoses on mock patient charts.
Methods: The Clinical Guideline Committee of the Japan Prosthodontic Society made mock patient charts and decided the disease name with the new diagnosis system. Fifty evaluators (prosthodontic specialists and hospital residents) answered the disease name with the new diagnosis system. The reliability and validity of the diagnoses were analyzed.
Results: Krippendorff’s α, which evaluates the reliability, was 0.378 (prosthodontic specialists) and 0.401 (hospital residents). The value was 0.524 with the top 10 evaluators, and 0.628 with the top 2 evaluators. There was no difference between the prosthodontic specialists and hospital residents in the correct answer rate. The correct answer rate for common dental diseases was high and that for uncommon dental diseases was low. Moreover, there was no relation between the correct answer rate and answering time or years of experience.
Conclusion: The reliability of the answers among all evaluators was not high, but it was high among the evaluators who showed a high correct answer rate in this study. The correct answer rate for common dental diseases was high and that for uncommon dental diseases was low.

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Purpose: As one type of glass fiber reinforced resin composite, Estenia C&B EG fiber (EG) has superior fatigue resistance. However, with straight clasps, exfoliation of glass fibers and some cracks occurred after the constant displacement fatigue test. In this study, to prevent the exfoliation of glass fibers, the fatigue resistance of EG clasps strengthened with a surface coating (SC) was evaluated by thermal cycling testing and constant fatigue testing.
Methods: 24 teeth (500A, Nissin Inc.) were prepared to make GFRC clasps with SC. The EG/SC clasps were subjected to thermal cycling for 5,400 cycles to mimic 6 months of intraoral use. The constant displacement fatigue test was carried out with a constant deflection of 0.25 mm loaded on the EG/SC clasp for 1,800 cycles. After testing, the clasp surface was observed by an optical microscope.
Results: The result of the cyclic fatigue test after the thermal cycling revealed a microscopic crack. However, the loading which required a displacement undercut of 0.25 mm did not change.
Conclusions: A recall has been required within 3 months of applying the coating. After the 3-month recall, any clasps in which SC is observed to have cracked and fallen off should have the SC reapplied.

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Patients: A case of complete dentures for an edentulous patient who had problems due to the maxillomandibular residual ridge relationship is reported. In addition, a new method of artificial teeth arrangement with an emphasis on establishing unilateral balance during masticatory movement is introduced. At maxillomandibular registration, the unilateral balancing areas were recorded on record blocks. To examine the maxillomandibular residual ridge relationship, standardized digital pictures of the upper and lower casts were taken, and the occlusal map was composed using digital processing software¹⁾. In the teeth arrangement, the occlusal contact points were set in the overlap areas of the upper and lower unilateral balancing areas on the occlusal map. The patient was satisfied with the new complete dentures during masticatory movement, and the mastication ability was improved.
Discussion: The occlusal map correctly diagnosed the problems of this case. The occlusal map was informative for planning the prosthodontic treatment and artificial tooth arrangement. The new method of artificial teeth arrangement resulted in stable dentures during masticatory movement.
Conclusions: The occlusal map and the new method of artificial teeth arrangement described in this report are practical.

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Patient: The Patient was a 69-year-old edentulous female with the chief complaint of poor retention of a mandibular denture who desired new (metal-based) dentures. She wore dentures with a short base border and abraded artificial teeth. The occlusal vertical dimension had decreased and the mandibular position had deviated to the anterior. After the masticatory function and aesthetic problem had been improved by interim dentures that had appropriate mandibular dimensions and proper mandibular position, metal-based dentures were fabricated with reference to the interim dentures.
Discussion: It is suggested that appropriate vertical dimensions and mandibular position are important for denture stability.
Conclusion: As a result of using interim dentures for improving functional and aesthetic problems before preparing the final prosthesis, an excellent prognosis was obtained.

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Patient: An edentulous female complained of masticatory dysfunction. Flabby gums were observed from the anterior to premolar regions of the maxilla. The mandibular residual ridge was found to have severe bone resorption. Mandibular dentures swayed with oral habits. To construct new mandibular dentures, the positional arrangement of the artificial teeth and the shape of the polished surface were determined using the flange technique. An impression of the flabby gums was taken with the plaster impression technique.
Discussion: As a result of the flange technique and plaster impression, the instability problem was improved and the treatment period was shortened.
Conclusion: In this case, fabrication of new dentures by using the flange technique and plaster impression resulted in an excellent prognosis.

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Patient: The patient was a 44-year-old man, who was diagnosed with esthetic and masticatory dysfunction including collapse of occlusion caused by severe periodontal disease and a defective prosthetic for the residual teeth. The treatment involved extracting a large number of teeth and providing a denture prosthesis.
Discussion: I extracted a large number of teeth, provided immediate dentures and repaired denture components, and it was said that I was in full dentures form as upper lower jaw treatment denture. I performed denture base and occlusal adjustment, and the mucous membrane side was improved, and it was connected by the stage when the satisfaction about the denture was provided for a good result that I was able to start final denture preparation.
Conclusion: The treatment using dentures effectively improved the QOL of the patient by esthetic improvement and masticatory rehabilitation.

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Patient: A 73-year-old woman complained of articulation dysfunction when using complete dentures. The palatal form of the polished surface was uniform and transparent. A palatogram showed an articulation disorder without soft plate articulation. The case was diagnosed as nonconformity of the polished surface of complete dentures during articulation. The form of the palatal polished surface was determined using a palatogram in new dentures. After fabricating the new dentures, the functional and esthetic problems were improved.
Discussion: In this case, articulation disorder was improved by gaining conformity between the movement range of the tongue and the polished surface of the palatal form.
Conclusion: New dentures were fabricated using a palatogram for an edentulous patient with an articulation disorder. In this case, grasping the articulation disorder of the initial dentures and appropriate reconstruction resulted in a favorable prognosis.

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Patient: A 71-year-old woman visited our hospital with the chief complaint of masticatory dysfunction. It was found that non-fitting maxillary dentures, which had been made approximately ten years earlier, caused the dysfunction. Although the patient wanted dental implants as a treatment option, removable maxillary dentures appeared to be appropriate for this case to provide support for the lips. After the patient had experienced lip support with the trial dentures, she selected removable dentures as a treatment option.
Discussion: Often the lip support achieved by the denture base significantly affects the restoration of the natural facial appearance. In selecting patching-up methods, it is important to assess the effects of morphological alveolar ridge alterations on facial appearance
Conclusion: The use of trial dentures resulted in an excellent prognosis for the patient with the final prosthetic appliance and higher level of patient satisfaction.

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Patient: A 53-year-old female visited our dental clinic with the chief complaint of mobility of a bridge in the mandibular anterior tooth area. After extracting the abutment teeth of the bridge, two implants were placed in a 3-tooth continuous defect area with marked alveolar ridge resorption. Thereafter, a provisional restoration was performed, progress was observed, and custom abutments with artificial gingiva and ceramo-metal restorations were placed.
Discussion: Although esthetic recovery could be achieved by inserting superstructures with artificial gingiva without bone grafting in this case, we also plan to carefully perform plaque control and occlusal adjustment in the future.
Conclusion: This case suggested that in implant treatment cases involving tooth defects in the anterior area with marked bone resorption, the achievement of functional recovery through prosthodontic treatment without bone grafting is a useful choice.

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Patient: The patient was a 61-year-old male with the chief complaints of masticatory disorder induced by missing posterior teeth and esthetic disorder induced by reversed occlusion of anterior teeth. He had tenderness in the left-side masseter.
Discussion: In this case, occlusal reconstruction was done by using a stabilization splint which increased the vertical dimension of occlusion. This made it possible to improve the overjet of anterior teeth in crown restorations. Adequate rehabilitation using a splint enabled a smooth transition to insert a treatment and the placement of the final prostheses while keeping an appropriate vertical dimension of occlusion.
Conclusion: The masticatory and esthetic disorders were improved by achieving an appropriate vertical dimension of occlusion using a stabilization splint.

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Patient: A 50-year-old female patient presented with a chief complaint of masticatory problems by maladaptation of maxillary removable partial denture (RPD). She had severe periodontitis and her RPD was not stable during mastication. Also, she seemed to have parafunction. Following prosthetic treatment with RPD using the milling technique, she was satisfied with the function and esthetics.
Discussion: At 3 years and 7 months after treatment, the prognosis is good except for extraction of the upper right central incisor. It is suggested that the supporting ability of the denture was reinforced by the design with the concept of a rigid support, making the RPD resistant to strong bite force.
Conclusion: Concerning this case of Eichner classification B3, the removable partial denture using the milling technique based on the concept of a rigid support resulted in a good prognosis.

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Patient: The patient was a 22-year-old female who had lost her upper right central incisor in a bicycle accident. In view of esthetics and minimal intervention (MI), a resin-bonded fixed partial denture was placed after soft-tissue ridge augmentation surgery to improve her esthetic and functional problems.
Discussion: By a combination therapy of a resin-bonded fixed partial denture with an ovate pontic and ridge augmentation, the esthetic and functional problems were considerably improved. Moreover, the damage to adjacent intact teeth was minimal by using a resin-bonded fixed partial denture, suggesting that accidental tooth loss in a young patient should be treated based on the MI concept.
Conclusion: The combination of a resin-bonded fixed partial denture with an ovate pontic and soft-tissue ridge augmentation provided satisfactory long-term results in esthetics and oral functions for this patient.

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Patient: A 52-year-old female visited our hospital with a complaint of pain in the left temporomandibular joint (TMJ). Twelve or thirteen years earlier, she had worn a removable partial denture (RPD) after tooth extraction, but she had stopped using it because of discomfort. Examination revealed a deviation of the patient’s jaw position from the original intercuspal position. As the initial treatment of the patient, an RPD and an occlusal splint were used to correct the mandibular position. After her TMJ symptoms had improved, we re-evaluated the mandibular position and decided it required full-mouth occlusal reconstruction.
Discussion: Esstablishment of occlusal support with an RPD and the use of an occlusal splint to maintain proper mandibular position improved the symptoms of TMJ and masticatory muscle pain.
Conclusion: This patient with TMJ disorder caused by loss of occlusal support was successfully rehabilitated using an RPD and an occlusal splint, which restored the proper mandibular position.

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Patient: The patient was an 80-year-old male at the first visit. Chief complaints were pus discharge from the area of the mandibular right molars and maxillary left molars and difficulty in mastication with removable partial dentures on the mandibular left premolars and first molar. He was treated with fixed partial dentures (FPD) supported by implants in the concerned area. Masticatory ability and maximum occlusal force were measured to evaluate the masticatory functions. The measurements were completed before the implant treatment, at the time of the definitive prostheses delivery and at the 5-year follow-up visit.
Discussion: Masticatory ability and the maximum occlusal force with the definitive prostheses were improved from those in the preoperative state, and maintained at the 5-year follow-up visit. The results indicated that a good prognosis was obtained.
Conclusion: The masticatory functions of the patient were improved with the implant prostheses on the bilateral mandibular free-end missing areas.

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Patient: An 82-year-old edentulous woman with a complex configuration of bone defective cavity presented in our hospital. Her maxillary and mandibular dentures had poor retention and swayed. To construct dentures, precise impressions were taken with individual trays, and occlusal pressure impression was performed after a trial with wax dentures. Articulation training was also performed in parallel with denture construction.
Discussion: Functional denture shape was formed by taking precise impressions with individual trays and occlusal pressure impressions. Additionally, to perform articulation training in parallel with denture construction, disorders were improved at an early stage.
Conclusion: The retention of dentures was improved by using undercuts in the bone defective cavity for this edentulous patient with a complex configuration of maxillary defective cavity. The QOL of the patient was also improved by articulation training in parallel with denture construction.

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