[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Purpose: The purpose of this study was to pursue fabrication of dental casts that could create crown restorations with highly reproducible occlusal contacts.
Methods: Twenty adult dentulous subjects, each with individual normal occlusion, were selected. To fabricate the dental casts, we performed three types of conventional impression methods and one dual-arch method. A full-mouth impression of the bimaxillary dentition was taken using stock trays with an alginate impression material in a conventional impression method 1. The maxilla using a custom tray and silicone impression material, and the mandible using a stock tray with an alginate impression material in a conventional impression method 2. The third type of conventional impression method used contrary impression material and trays of a conventional impression method 2. Dental casts were produced with each method and mounted on articulators using the cast method. The dual-arch impression method was taken using a plastic tray and silicone impression material, and an occlusal relationship was reproduced on the articulator. Occlusal records of intraoral and dental casts were then prepared using an occlusal contact silicone checker, and add-pictures were extracted from these records. We then collated the classifications of Nakao occlusal facets sufficiently with the occlusal surface of the maxillary dentition model, the occlusal record, and the add-pictures, and the occlusal contact regions were identified. We counted the number of reproducible and nonreproducible regions from the comparison of occlusal contact regions of intraoral and dental casts. The obtained data were compared among each impression method with a repeated one-way ANOVA and a Tukey's test.
Results: It was shown that the dual-arch impression method had larger values than conventional impression methods did in the reproducible regions and smaller values in the nonreproducible regions.
Conclusions: We found that the dual-arch impression method was useful for the fabrication of dental casts with highly reproducible occlusal contacts.

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Purpose: This study aimed to determine fracture toughness values of yttria-stabilized zirconia (Y-TZP), using the Single Edge V-notch Beam method (SEVNB) and the Indentation Fracture method (IF) to demonstrate a suitable measurement approach to fracture toughness values by examining measurement results.
Methods: Measurement with SEVNB was conducted using test specimens with the V-notch at two conditions of crosshead speed, 0.5, and 1.0 mm/min, according to International Organization for Standardization (ISO) 6872. A Vickers indenter was used for IF testing of specimens at 30 kgf of the load for 15 seconds, thus generating indentation and cracks to obtain measurements for calculating fracture toughness by use of a formula in Japanese Industrial Standards (JIS) R 1607. The multiple comparison was used to compare the fracture toughness values. The appearance of the fracture surface obtained in SEVNB and the indentation andcracks obtained in IF were observed using a Scanning Electron Microscope (SEM). X-ray Diffraction (XRD) was conducted for phase transformation of the fracture surface obtained inSEVNB.
Results: A significant difference was found in fracture toughness values between SEVNB and IF. SEVNB indicated higher fracture toughness values and a larger standard deviation than IF. In addition, SEVNB showed significantly higher fracture toughness values at 1.0 mm/min crosshead speed in comparison with 0.5 mm/min. SEM revealed that stable and unstable fractures were found in SEVNB, and indentation and cracks were clearly observed in IF. In the fracture surface obtained in SEVNB, a phase transformation resulting from bending stress was observed with XRD.
Conclusion: We suggest that IF is suitable for measurement of fracture toughness valuesof Y-TZP in comparison with SEVNB. Because the measurement approach of fracture toughness values of Y-TZP has a specific phase transformation feature, a development of new experimental conditions seems to be required for both SEVNB and IF.

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Purpose: To determine the criteria for the most efficient means of denture cleaning, we evaluated by means of in vitro assay the effects of current chemical and mechanical methods.
Methods: (1) Biofilms of Candida formed on denture-base resin pieces were immersed in denture cleansers or distilled water. Immersing or rinsing in water was repeated once a day for 5 days, and the test was repeated with denture cleanser. What remained was calibrated according to fluorescence levels in the medium supplemented with REDOX Indicator. (2) The effect was determined according to the roughness of the resin surface and the removal effectiveness of biofilms for the following experimental conditions: immersing in five kinds of denture cleansers, brushing with toothpaste, and brushing with denture paste.
Results: (1) The sterilization effect completely disappeared when the resin pieces were washed with only distilled water, even if denture cleanser had been used the previous day. A significant difference appeared in the amount of remaining Candida between the denture cleanser group and the control group (p < 0.05). (2) The surface roughness was increased further after brushing and increased even more after brushing with toothpaste because of the abrasives. In the removal effect of Candida biofilms, highly abrasive toothpaste produced significantly higher results than low abrasives, recognized not only with brushing, but the highest results were from denture cleanser.
Conclusions: Removal of denture plaque after cleaning with a brush having no toothpaste, the dentures should be immersed in a denture cleanser overnight every day.

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Patient: The patient, a 53-year-old female, presented with chief complaints of esthetics and masticatory impairment by unilateral distal-extension edentulous ridge. As a precise impression, FBI (functional bite and impression) was chosen. A CP Ti metal structure denture made using Secura Lock Attachment and milling technique was implemented.
Discussion: The patient was satisfied with the functional and esthetic requirements by application of the attachment and high rigidity of the structure. This prosthetic appliance contributed not only to functional recovery, but also to improvement in quality of life.
Conclusion: The harmonious occlusal form by FBI and application of the attachment were effective for the function and esthetics of removable prosthetic rehabilitation.

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Patient: A-34-year-old female presented with a chief complaint of masticatory impairment. After preprosthetic treatment, aesthetic and functional improvement by provisional restorations, the patient was fitted with composite resin-jacket crowns on the molars and all-ceramic crowns on the maxillary incisors.
Discussion: The composite resin prosthesis had become discolored and dull, but the all-ceramic crowns retained their original color because of the properties of the material. Periodontal surgery was performed in the maxillary left molar area to provide adequate axial height for preparation of the abutment teeth, enabling an adequate bridge to be constructed.
Conclusion: All-ceramic crowns have excellent esthetic and functional properties, resulting in patient satisfaction.

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Patient: A 74-year-old female complained of masticatory disturbance caused by oralmucosa pain beneath the dentures. The patient had no vertical stop or lower occlusal vertical dimension evident from facial appearance, and marked ridge resorption was confirmed. After previous treatment of periodontal tissue and prosthetic appliance, recovery of the occlusal function wasattained by aremovable partial denture based on a correct imbalance of the occlusal vertical dimension and the occlusal plane of in-use partial dentures.
Discussion: In this case, making an arrangement of denture rigidity and intercalary defect capsize accomplished an early improvement of masticatory function.
Conclusion: Concerning a case of lower occlusal vertical dimension and nonvertical stop occlusion, the recovery of function using a removable partial denture with appropriate previous treatment and denture planning is found to result in a good prognosis.

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Patient: A 54-year-old woman presented with a chief complaint of disorder of articulation caused by lingual–inclined mandibular anterior teeth, poor retention of complete denture in the maxilla, and esthetic problems. Her ailment had been diagnosed as skeletal mandibular prognathism before she presented. The position of the mandibular anterior teeth were set up accordingto esthetic and phonetic aspects, followed by setups of the positions of anterior maxillary teeth and occlusal plane. Porcelain-fused-to-metal fixed partial dentures were fabricated in the anterior and posterior areas in the mandible.
Discussion: This case required sufficient exploration, well-considered treatment planning and procedures with a treatment denture, and provisional restorations to enable rehabilitation from the complicated functional and esthetic problems.
Conclusion: According to the considered treatment planning, both the functions and theesthetics could be rehabilitated in an Eicher C2 patient with skeletal mandibular prognathism.

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Patient: A 73-year-old female patient who was undergoing marginal resection of the mandible for carcinoma and an abdominal full thickness skin graft complained of masticatory dysfunction with saburra in the mandibular recessed area. A mandibular denture for the defect was fabricated by using the tissue conditioner for molding the border and buccal flange of the denture.
Discussion: As a result of the attainment of close contacts between the buccal mucosa and buccal flange and the border of the denture base by using tissue conditioner, the saburra in the recessed area had disappeared and the masticatory function had improved.
Conclusion: With the lack of mobility of the skin graft, forming an appropriate shape of theflangeand border of the denture base achieved improvement of the masticatory function and favorable prognosis.

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Patient: The patient was a 57-year-old female with the chief complaint being masticatory disturbance by tooth movement, with severe periodontal disease. Besides periodontal treatments, the establishment of an occlusal support and correction of an occlusal plane were provided using the mandibular partial denture.
Discussion: After wearing the final prosthesis, the patient had been developing a relatively stable condition as a result of continual maintenance of the mandibular partial denture and periodontal conditions of residual teeth every two or three months.
Conclusion: Residual teeth of the patient with severe periodontal disease were saved by establishing the occlusal support with partial denture and continuing the periodontal maintenance.

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Patient: A 60-year-old male complained of reciprocal clicking on the bilateral temporomandibularjoint (TMJ) and masticatory disturbance. A treatment denture was fabricated for the missing mandibular right molars. This denture was inserted to improve occlusal vertical dimension and for protrusive repositioning of the mandibular position. After improving the main complaint and a follow-up, we planned occlusal reconstruction with fixed prostheses and removal denture for the final prosthetic treatment.
Discussion: The provided occlusal reconstruction could release masticatory disturbance with temporomandibular joint disk displacement. In this case, a modification of the mandibular position with a prosthetic appliance was effective treatment.
Conclusion: Occlusal reconstruction and bite rising were applied to the patient with reciprocal clicking of the TMJ. Although he made satisfactory progress, long time follow-up with periodic and prosthodontic examination will be required in the future.

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Patient: The patient, a 73-year-old male, complained of masticatory disturbance resulting from non-conformity of his lower removable partial dentures. To correct the esthetic appearance and the decreased occlusal diameter resulting from extensive loss of dentine, caused by significant tooth wear, we reconstructed the occlusion with prosthetic treatment.
Discussion: We used a provisional restoration to set a good mandibular position, and we achieved a favorable outcome because the prosthetic device was constructed after a long-term follow-up.
Conclusion: In the event of masticatory disturbance because of a substantial loss of dentine, a result of occlusal wear, it is essential to repair the morphology of the tooth crown and the occlusal diameter, the performing reversible functional checks before starting treatment.

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Patient: A 57-year-old woman visited our clinic complaining of difficulty in chewing because of a missing right maxillary molar and left mandibular molar teeth. She had little clearance especially in the right molar region because of a long-term absence of prosthodontic treatment after an extraction of teeth. A metal-based removable partial denture was delivered after making clearance by recounting opposite teeth without altering the vertical dimension.
Discussion: The denture insertion improved occlusal relationship and functional stability, and the subsequent periodontal health of the remaining teeth. Moreover, the use of a metal-based denture enabled us to minimize the patient's uncomfortable feeling.
Conclusion: Applying an unbreakable metal-based denture to partial edentulous regions with insufficient clearance resulted in a satisfactory therapeutic effect.

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Patient: A 49-year-old female was referred to us regarding esthetic dissatisfaction with the upper front teeth. The problem was a mastication difficulty resulting from missing bilateral molar teeth in the mandible and occlusal damage of the front teeth caused by a loss of occlusal support. The recovery of occlusal support by temporary prosthesis and anterior guidance was then reconstructed.
Discussion: The esthetic dissatisfaction was resolved using the bridge, and the periodontitis improved as a result of maintaining occlusal support. Treatment based on a problem-oriented system can provide esthetic and functional improvements and is useful to obtain a satisfactory prognosis.
Conclusion: After the establishment of occlusal support, utilizing provisional restoration to search an anterior guidance seemed to be one of the techniques available for a case of restruction including anterior guidance.

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Purpose: The diagnostic assessment of the level of difficulty in treating patients who need prosthodontic care is useful to establish a medicoeconomically efficient system with primary care dentists and prosthodontic specialists.
Methods: A multi-axis assessment protocol was established using the newly established treatment difficultyindices. The protocol contains Axis I: oral physiological conditions (e.g., teeth damage and/or missingteeth); Axis II: general health and sociological conditions (e.g., medical disorders); Axis III: oral health-related quality of life (OHRQOL; e.g., oral health impact profile: OHIP); and Axis IV: psychological health (e.g., mood, anxiety, somatoform disorders). A preliminary study on the test-retest consistency of the protocol was conducted to check the levels of reliability of the indices prior to a large-scale, multi-center cohort study on the validity of the protocol.
Results: The test-retest consistency in terms of the oral physiological condition (Axis I) after data reduction was 0.82 for patients with teeth problems, 0.73 for partially edentulous patients, and 0.78 for edentulous patients. The reliability for general health and sociological conditions (Axis II), OHRQOL (Axis III), and psychological health (Axis IV) were 0.88, 0.74, and 0.61, respectively. These values reflect either "sufficient agreement" or "excellent agreement" in accordance with the criteria established by Landis and Koch¹⁾.
Conclusions: This protocol is the first multi-axis assessment scheme introduced for prosthodontic treatment with sufficient reliability. This new system is therefore expected to have a significant impact on future dental diagnostic nomenclature systems.

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