Purpose: The purpose of this study was to investigate the validity of the process of duplicating complete dentures using general digital devices through the following tests: cytotoxicity test of materials used, adhesion test of materials to a silicone impression material and a self-curing resin, and questionnaires to operators on duplicate dentures in clinical situations.

Methods: The cell viability of mouse fibroblast-like cells in acrylonitrile- butadiene-styrene (ABS) and polylactic acid (PLA) were evaluated as a cytotoxicity test. The tensile strength between the silicone impression material/self-curing resin and ABS/PLA specimen was measured as adhesive strength using a universal testing machine. Six practitioners who used duplicate PLA complete dentures in 7 patients were asked to evaluate the duplicate denture using the original questionnaire.

Results: The cytotoxicity test showed that the cell viabilities in ABS and PLA were similar to that in acrylic resin at the cell culture times of 24, 48 and 72 hours. The adhesion test showed that the adhesive strength between the ABS/PLA and silicone impression material was significantly lower than that between the conventional self-curing resin and silicone impression material. Although the adhesive strength between the PLA and self-curing resin was low, there was no significant difference between the ABS and self-curing resin. The results of the questionnaire showed that the duplicate denture made of PLA would be of similar value compared to the conventional duplicate denture made of acrylic resin.

Conclusions: The present study suggests that the duplicate complete dentures made by our proposed digital process are clinically effective.

Purpose: The aim of this study was to verify that sleep bruxism for outpatients can be assessed by using an ultraminiature wearable electromyogram (EMG) device, FLA-500-SD (FLA).

Methods: The subjects were ten outpatients who were diagnosed as sleep bruxers on the basis of clinical findings. Masseteric EMG data recorded by using the FLA during nocturnal sleep at home were analyzed. Bursts with maximum amplitude larger than 20% of maximum voluntary contraction (MVC) and duration longer than 0.25 s were selected as sleep bruxism bursts (SB-Bs).

Results: All subjects could operate the FLA. There was no significant difference between subjective assessment of sleep state of the measured night by means of visual analog scale (VAS) and that of usual nights. Recorded EMG baselines were stable. Distinct bursts including phasic bursts, tonic bursts and bursts with a low amplitude but considerably long duration were observed. The mean (± SD) number of SB-B per hour was 14.3±11.2 /h and the mean (± SD) duration of a SB-B was 2.28±0.92 sec. Individual data of these items analyzed for each subject were able to be compared with known standard data from previous studies.

Conclusions: It was demonstrated that the FLA can be easily set and operated by outpatients, that stable and clear EMG data can be recorded at the patient’s home without restraint, and that the degree of sleep bruxism can be assessed by analyzing data obtained by using the device.

Purpose: In this study, we investigated the fitness accuracy and retentive force of retainer fabrication using laser-sintering, and the possibility of its clinical application.

Methods: Laser-sintering with a dedicated Co-Cr alloy was used to examine the following two aspects: 1) the quantity of the most suitable undercut using cantilever examination, and 2) fitness accuracy and retentive force of retainer fabrication. We used a dedicated Co-Cr alloy, gold-silver-palladium alloy and a Co-Cr alloy as casting materials. Based on observations from the first experiment, tapered specimens which had a semicircular shape in vertical cross-section were used. In experiment two, a metal prototype was produced based on the average dimensions of the mandibular first molar and samples such as retainers which had been molded by computer generated designs. Fitness accuracy was measured through embedding and cutting. Retentive force was measured using the pulling test.

Results: The quantity of the most suitable undercut using laser-sintered retainer fabrication was 0.14 mm. The result by laser-sintered retainer fabrication was at the same level as casting with regard to both fitness accuracy and retentive force.

Conclusions: Laser-sintered retainer fabrication was comparable with casting, and its clinical application may be possible.

Patient: This report is of a 55-year-old female with swelling around the bilateral submandibular and mental foramen regions. A functional disorder with severe periodontitis and implantitis in the maxilla and mandible was diagnosed. The remaining lower teeth and dental implant could not be saved and were removed. As per the prosthodontic treatment, the mandible was treated by an implant overdenture with fixed bar attachment. The patient did not want her maxillary region to be treated because she initially had a subjective symptom only in the mandible. However, mandibular treatment was followed by a complete denture for the maxilla.

Discussion: The patient had anxiety about esthetic and functional disorders due to treatment. A preferential approach for mandibular treatment was eliminated because of this anxiety. Subsequently, the patient’s maxillary region was treated.

Conclusion: The patient had a good prognosis with the mandibular implant-supported overdenture and maxillary complete denture.

Patient: A 62-year-old woman visited our clinic complaining of swelling and occlusal pain at #5 (Universal system). The examination revealed a root fracture at #5 as well as multiple ill-fitting prosthesis throughout the mouth. Ill-fitting restorations were removed followed by the amelioration of occlusal vertical dimensions using provisional restoration. Final prosthesis after root canal and periodontal treatment was performed. Thereafter, she was satisfied with the treatment results.

Discussion: Improving periodontal tissue with crown lengthening and occlusal therapy using provisional restoration before placing final prostheses led to a good prognosis.

Conclusion: In order to keep the long-term stability of the treatment result, it is important to achieve periodontal tissue with high cleanability and control appropriate occlusion.

Patient: The patient was a 67-year-old woman whose chief complaint was a mastication disorder caused by poorly fitting dentures she had worn for 7 years. Both maxillary and mandibular residual ridges showed severe resorption. The dentures had inadequate distal extension and poor retention. Additionally, the existing dentures shifted the mandible forwards and pushed the mandibular incisors up to the maxillary incisors.

Discussion: Using Gothic arch tracing, new dentures were fabricated that corrected the horizontal maxillo-mandibular relationship. The patient appeared to have developed poor mastication habits while wearing the abnormal dentures. Her chief complaint of a mastication disorder was resolved by wearing the treatment denture.

Conclusion: Fabrication of new treatment dentures provided stability and a favorable outcome for the patient by using treatment dentures with Gothic arch tracing.

Patient: A 71-year-old male who underwent bilateral maxillectomy and mandibulectomy due to florid cement-osseous dysplasia was referred to our maxillofacial prosthetic clinic. Palatal side of tissue undercuts in the defect were planned to be engaged for gaining stability of the prosthesis. The magnetic attachments were used on the right side in which a hollow shape obturator was divided into two segments in order to engage the undercut in function and to remove from the mouth independently. The left side obturator was also fabricated into a hollow shape but united to the palatal base of the prosthesis. Assessments for masticatory function after installation of the prosthesis revealed favorable results and the patient was satisfied. Therefore, this dento-maxillary prosthesis with bilateral obturators was successful even though relatively complicated laboratory steps were required.

Case overview: We report a case of a 75-year-old male who was admitted to our Prosthodontics Department in December 2011 with a chief complaint of instability during mastication and speech of a maxillofacial prosthesis that was placed in 2009. The patient had maxillary edentulism with partial maxillary defects. We fabricated an alternative maxillofacial prosthesis retained by undercut regions, located anterior and posterior to the defect. The two-piece design enabled the anterior section to be inserted through the nasal aperture.

Discussion: Maxillary edentulism enabled the anterior section of the prosthesis to be inserted through the nasal aperture and be magnetically connected to the main prosthesis in the sinus cavity. Stability of the maxillofacial prosthesis was achieved through the use of large undercuts.

Conclusion: We successfully improved the patients’ masticatory and speech function by designing a stable maxillofacial prosthesis that made effective use of existing undercuts.

Patient: A 30-year-old woman visited the Department of Fixed Prosthodontics, Osaka University Dental Hospital seeking a second opinion on the treatment method of secondary dental caries that occurred on the maxillary right central incisor. It was considered that the ill-fitting facing metal crown included deep secondary caries reaching the subgingival region in the right central incisor. Periodontal surgery was carried out to obtain the symmetry of the left and right gingival margin and recover the normal biological function after orthodontic extrusion. The prosthetic treatment was finished with an all-ceramic crown using a zirconia frame.

Discussion: The esthetical problem of the maxillary right central incisor was improved by adjusting the morphology using provisional restoration and precisely reflecting the morphology in the prosthesis.

Conclusion: This report introduced the clinical case that esthetic problems of the secondary caries of the maxillary central incisor were improved by pre-prosthetic treatment and all-ceramic crown placement.