Purpose: This study aimed to measure the marginal discrepancy at the buccal, mesial, and distal sides along the marginal edge of all-ceramic crowns fabricated using the DENTAL Cadim CAD/CAM system and to examine the effect of a post-milling heat treatment for staining on the marginal fit of the all-ceramic crowns.
Methods: An 18-8 stainless steel abutment tooth with a height of 5 mm and an occlusal convergence angle of 8° was used as a mold. A cylindrical pattern model was fabricated using a brush stacking method with an autopolymerizing resin. Three-dimensional geometric measurement of the pattern model was performed using a spherical ruby scanning probe. Subsequently, five all-ceramic crowns were milled from Cadim block CE by using the DENTAL Cadim CAD/CAM system. Surface roughness (R_a and R_max) of the occlusal surface and vertical distances between the marginal edge and the mold before and after the post-milling heat treatment were measured using a profilometer and an X-Y coordinate reading microscope, respectively.
Results: The Ra and Rmax significantly decreased after the heat treatment. The vertical distance at the mesial and distal sides of the crowns was approximately 10 μm before and after the heat treatment. This distance at the buccal side was significantly greater (17.1 μm) than that at the mesial and distal sides before heating, and it significantly increased to 22.0 μm after heating.
Conclusion: The all-ceramic crowns milled from Cadim block CE by using the DENTAL Cadim CAD/CAM system showed a clinically acceptable marginal fit. We also observed that the fitting accuracy differed significantly among the three sides of the crown. The change in the marginal fit after the post-milling heat treatment was of a clinically acceptable value.

抄録全体を表示

Purpose: The stage at which bone formation was influenced by a static magnetic field (SMF) remains to be elucidated. The purpose of this study was to investigate the initial and long-term effects of moderate-intensity SMF on mouse osteoblastic cells (MC3T3-E1).
Methods: MC3T3-E1 osteoblastic cell cultures were exposed to SMF (250 mT, Nd-Fe-B disc magnet). The long-term effect of this exposure was evaluated by measuring mineralized nodule formation. Osteoblastic cell proliferation was assessed using a colorimetric proliferation assay (WST-8); differentiation was evaluated by measuring alkaline phosphatase (ALP) activity; and noncollagenous gene expression was evaluated using real-time PCR to determine the initial and early responses.
Results: After a month of continuous SMF exposure, mineralized nodule formation increased significantly. The initial proliferative activity decreased and was not related to apoptotic changes. ALP activity and the gene expression levels of secreted phosphoprotein 1 (SPP1), integrin binding sialoprotein, and bone gla protein were not influenced by the SMF exposure.
Conclusion: Moderate-intensity (250 mT) SMF exposure increased mineralized nodule formation in mouse osteoblastic MC3T3-E1 cells. However, gene expression related to decreased cell proliferation and unaltered cell differentiation and bone matrix did not correlate with the long-term effects observed following SMF exposure. The mechanism by which SMF exposure influences osteoblast mineralization remains unknown.

抄録全体を表示

Purpose: This study aims to examine the reliability, validity, and preference of an original faces scale (original FS) for mood assessment.
Methods: The original FS was evaluated by comparing it with a modified faces scale developed by Lorish and Maisiak (modified L&M FS) and the 100-mm visual analog scale (VAS) in mail survey mood assessments. The subjects were Japanese elderly patients with dentures (age range: 52-81 years; mean age: 68.8 years). We included 32 subjects for reliability and validity analyses, and 34 for analysis of scale preference. The test-retest reliability of the scales was determined by calculating the correlation between two assessments obtained at one-week intervals; the concurrent validity of the original FS, by calculating its correlation with VAS and the modified L&M FS. The scale preference was assessed by asking the subjects to determine which scale was easiest/most difficult to assess. The chi-square test was used to determine statistical differences between the three scales.
Results: All scales revealed a good test-retest reliability; further, the original FS demonstrated the highest Spearman’s rank correlation coefficient (r=0.76). The concurrent validity, measured by the correlation between the original FS and VAS (r=0.70, P<0.01) and the modified L&M FS (r=0.90, P<0.01), was also established. A majority of the subjects preferred the original FS to the other scales.
Conclusion: The original FS is an effective nonverbal method for conveniently assessing the mood of patients with dentures with respect to prosthetic treatment.

抄録全体を表示

Purpose: The Oral Health Impact Profile (OHIP) is one of the most widely used instruments to measure oral health-related quality of life (OHRQoL). The aim of this study was to evaluate the reliability and validity of a Japanese short version of the Oral Health Impact Profile (OHIP-JP16) for prostheses.
Methods: Data were collected by means of self-administered questionnaires from July 2004-November 2005 at 4 dental offices located in Japan. The questionnaires consisted of self-perceived oral health status, need for treatment, and the OHIP-JP16 score. The total target sample consisted of 137 patients, of which 125 patients answered all the 16 items in the questionnaires. The reliability was assessed in terms of internal consistency and reproducibility.
Results: Cronbach’s alpha of the OHIP-JP16 subscales ranged from 0.43 to 0.93. The reproducibility of test-retest reliability was analyzed (n=12). The test-retest reliability was measured by the intra-class correlation coefficient (ICC) and kappa index. The ICC ranged from 0.69-0.92 and kappa index ranged from 0.12-0.67. The internal consistency and reproducibility demonstrated quite a good reliability. Discriminative validity was examined by comparing total scores among groups according to the following parameters: number of teeth (more than 24 and less than 23), Eichner index (A, B, and C group), denture wearing (with and without dentures), and self-perceived oral health (good and poor). The patients who had more than 24 teeth, were in group A of the Eichner index, those without dentures, and having good oral health had better OHIP-JP16 total scores (P<0.05).
Conclusion: As a result of having examined for behaviormetrics study, OHIP-JP16 showed good measurement properties and might be appropriate for use in the clinical settings.

抄録全体を表示

Purpose: Attachments are widely used for the fixation, retention, and stabilization of prostheses. This study assessed the retentive forces of 3 types of attachments for root-retained overdentures.
Methods: The patrices of “O” ring plastic pattern anchor (OPA) attachments (No. 2; Inoue Attachments), magnetic attachments (MAs; 3513, Neomax), and coping telescopes (CTs) were cast with an Ag-Au-Pd alloy (Castwell, GC). For the OPA and MA, the “O” ring and magnet were fixed on the post anchor and keeper, respectively, by using autopolymerized polymethyl methacrylate (PMMA) resin (Unifast II, GC). For the CT, autopolymerized PMMA was used to connect the patrix coping and matrix framework. The retentive force (n=5, N) was measured at a crosshead speed of 20 mm/min as the maximum load when the connected patrix and matrix of either single or double retainers (30-mm apart) were separated under both dry and wet conditions. The results were analyzed using ANOVA/Tukey’s HSD test (α=0.05).
Results: In the case of a single retainer, the retentive force of the CT was significantly greater than those of the MA and OPA (P<0.05). However, the coefficient of variation of the CT was also greater. In the case of double retainers, the retentive forces of all the attachments were approximately twice the forces of single retainers.
Conclusion: Although the CT exhibited the greatest retention, the retentive force of each CT specimen varied widely. Consistent retentive values were obtained for the OPA and MAs because ready-made patterns of these attachments were used.

抄録全体を表示

Purpose: This study aims to investigate the relationship between masticatory function and dysphagia in patients with myotonic dystrophy (MyD).
Methods: Eighteen MyD patients with an average age of 54.1 years (SD, 5.7 years) were enrolled as subjects of this study. They were divided into 2 groups: a non-dysphagia group (12 patients) that consumed ordinary rice along with an ordinary supplementary diet and a dysphagia group (6 patients) that consumed semisolid rice along with a chopped supplementary diet. The maximum bite force, activity in the temporal and masseter muscles during 1 chewing cycle, number of food items that were considered as easy to chew, and occlusal contact area were investigated, and the proportion of patients with anterior open bite was analyzed. The results obtained were compared between the groups.
Results: The maximum bite force in the dysphagia group was statistically much smaller than that in the non-dysphagia group (P=0.024). On the other hand, the masticatory muscle activity in the dysphagia group was statistically much greater than that in the non-dysphagia group (P=0.048). The proportion of patients with anterior open bite in the dysphagia group was higher than that in the non-dysphagia group.
Conclusion: These results suggest that the bite force and anterior open bite might influence dysphagia in MyD patients; however, this remains a speculation. It is necessary to consider masticatory disturbances in MyD patients with dysphagia.

抄録全体を表示

Purpose: We conducted an in vivo evaluation of the marginal and internal gaps of 3-unit all-ceramic fixed partial dentures (FPDs) with zirconia frameworks by using black and white silicone materials. These FPDs were fabricated using a computer-aided design/computer aided machining (CAD/CAM) system (Cercon Smart Ceramic).
Methods: Forty-two abutments of 21 Cercon FPDs were examined before the final cementation. Silicone materials obtained from each FPD were sectioned buccolingually and mesiodistally, and the thickness of the silicone layer was measured under a microscope.
Results: The mean marginal gaps of the mesial and distal abutments were 83.3 and 90.6 μm, respectively. No difference was observed between the corresponding measurement points on the mesial and distal abutments with regard to the gap size.
Conclusion: The mean marginal gap between the abutments and the retainers of the 3-unit zirconia FPDs fabricated using the Cercon system was 86.9 μm, which is a clinically acceptable value.

抄録全体を表示

Purpose: The objective of this study was to clarify the effect of mechanical loading on the trabecular structure of peri-implant bone and determine its correlation with the implant stability quotient (ISQ) value.
Methods: This study used 3 immunologically mature male dogs. Three months after bilateral extraction of the mandibular premolars of the dogs, 4 implants were placed in these sites for each dog. After 3 months to allow healing of the implant sites, superstructures were prepared on the right side (loaded side). The implants on the left side were covered with mucosa (non-loaded side). The ISQ values of all implants were measured 3 months after placing the superstructures; subsequently, the animals were sacrificed. After the mandible was excised and fixed, micro-CT images were acquired and three-dimensional analysis, performed.
Results: The means and S.D. of the ISQ value for the 12 implants were 69.6±6.2 and 62.9±13.8 for the loaded and non-loaded sides, respectively. No significant difference was noted between the 2 sides. Mean and S.D. of bone volume fraction (BV/TV) were 13.0±6.6 and 9.3±3.8; trabecular thickness (Tb.Th), 97.7±27.7 µm and 91.0 ± 24.0 µm; and trabecular number (Tb.N), 1.24±0.30/mm and 0.99±0.20/mm for the loaded and non-loaded sides, respectively. BV/TV and Tb.N values were higher for the loaded side.
Conclusion: Morphological changes occurred in response to functional loading. However, lamellar bone was observed around the implants on both sides. These findings revealed that changes in the bone structure due to functional loading of implants had negligible or no effect on the ISQ value.

抄録全体を表示

Purpose: The purpose of this experiment was to clarify whether the amount of saliva secreted during the chewing gummy jelly affected the assessment of masticatory performance.
Methods: Twenty healthy subjects were asked to chew 2 g of gummy jelly for 10, 15, and 20 seconds and the amounts of glucose extraction and saliva secretion were measured. The changes in both glucose extraction and saliva from 10 to 20 seconds were investigated. Next, the amount of glucose extraction excluding the effect of saliva (extraction B) was divided by the amount of glucose extraction measured (extraction A), and the results for the two chewing times were compared.
Results: The amount of glucose extraction increased proportionally as the chewing time progressed and the change was significant. Although the amount of saliva secretion increased as the chewing time progressed, the change differed from the proportional change in glucose extraction. The amount of saliva secretion was extensive for the first 10 seconds and increased about 0.1 ml every 5 seconds. The ratio of the extraction B to extraction A was between 1.03 and 1.05, and there was a significant difference between each pair of chewing times.
Conclusion: From these results it was concluded that the amount of saliva secretion increased during chewing of gummy jelly and affected the assessment of masticatory performance, and this effect was less than 5 % for chewing of up to 20 seconds.

抄録全体を表示

Patients: Case 1, a 28-year-old male with malocclusion (molar open bite) associated with temporomandibular arthrosis. After splint therapy, a metallic splint made of cap clasps for the lower molars of both sides was prepared for this patient. Case 2 was a 58-year-old male in whom adequate denture space was not available when preparing a partial denture, because of a deep overbite. This case was treated by bite raising, with cap clasps serving as the retainer. Case 3 was a 48-year-old woman in whom the dental arch size differed between the maxilla and mandible and with malocclusion of the left molars. In this case, treatment with an ordinary clasp denture was difficult. After insertion of an immediate denture using a Starbuck splint, a metal base denture combined with cap clasps was applied.
Discussion: The greatest advantage of a cap clasp lies in that it does not necessitate preparation of the tooth and allows the existing crown and bridge to be utilized as an abutment tooth. Retainers made using cap clasps are expected to be useful when bite raising is attempted, because of their high supporting ability and retentive force. They also offer promise as a means of reversible and permanent treatment of temporomandibular arthrosis.
Conclusion: Dentures and metallic splints prepared with a cap clasp serving as a retainer fit well into the oral cavity of patients, provide excellent occlusal support, and are retained for long periods of time.

抄録全体を表示