Purpose: The purpose of this article is to review the studies related to dentures published by the members of the Japan Prosthodontic Society.
Study selection: A total of 6 original articles published in the Journal of Japan Prosthodontic Society were selected. All articles were related to prosthodontic dentures and published in volume 49 of the journal in 2005.
Results: The research project covered oral comfort, oral dryness in denture wearers, care management, and oral condition.
Conclusion: This report is to advocate the pursuit of comfort in oral function for dentures and the importance of masticatory function to the health care of people.

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Purpose: The aim of this study was to clarity the effectiveness of abdominal breathing in reducing or inhibiting non-sleep bruxism.
Methods: Twenty-five subjects (18 men and 7 women) were asked to perform maximal voluntary clenching 3 times, silent reading for 10 min in a relaxed state, and silent reading for 10 min after performing abdominal breathing. Simultaneously, the masseter muscle activity was measured by means of electromyography (EMG), and the blood flow at the fingertip was recorded by means of a laser flowmeter device to indicate sympathetic activity.
Results: Ten subjects exhibited non-sleep bruxism; bruxism events disappeared in 8 of them, and their frequency decreased in the remaining 2 subjects during silent reading after performing the abdominal breathing. Measurements of the blood flow revealed a significant difference between the existing state before the abdominal breathing procedure compared to that after the procedure (P<0.01).
Conclusion: During the 10 min of silent reading following the abdominal breathing disappearance or reduction of bruxism events was observed; thus, we suggest that the abdominal breathing can influence the occurrence of non-sleep bruxism. Moreover, after the abdominal breathing, increased blood flow at the fingertip was observed indicating a reduction in the sympathetic activity.

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Purpose: To avoid early fatigue fracture of occlusal rests, the optimum heat treatment condition was sought.
Methods: Each specimen consisted of an occlusal rest (thickness, 0.8 mm), vertical minor connector, and denture base connector. The specimens were conventionally cast, steam cleaned, and finally pickled in a cleaning solution. The heat treatment conditions were classified as as-cast, manufacturer’s instruction, and 800°C solution treatment. Twenty-six specimens were prepared for each of the 3 groups.
 A fatigue testing machine was designed so that the occlusal rest component could be deflected by displacing the denture base connector downward. A displacement of 0.46 mm was predetermined from the load-deflection relationship of the specimens. Cyclic load was applied at a frequency of 500 cycles/min until occlusal rest failures occurred or the preset limit of 2 million cycles was reached. Subsequently, Rockwell hardness was tested on the base surface. The results were statistically analyzed.
Results: All the specimens fractured within the preset limit. The heat treatments significantly influenced the fatigue resistance (P<0.003). A significant difference (P<0.05) was detected between the 800°C solution treatment and manufacturer’s instruction groups. The heat treatments significantly influenced the hardness (P<0.001). A significant difference (P<0.05) was observed between the as-cast and manufacturer’s instruction groups and between the 800°C solution treatment and manufacturer’s instruction groups.
Conclusion: The 800°C solution treatment was most favorable for the improvement of fatigue resistance. The heat treatment based on the manufacture’s instruction increased mostly the hardness; however, it was unsuitable for improving the fatigue resistance.

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Purpose: The purpose of this study was to establish the application criteria for ultrasonic therapy in temporomandibular disorders.
Methods: By using the continuous sampling method, 20 patients were selected from among the patients in whom ultrasonic therapy was indicated by the attending dentist. Prior to ultrasonic therapy, each patient was examined for the presence or absence of 4 symptoms, namely, spontaneous pain and tenderness in the masseter muscle, pain upon jaw opening, and tenderness in the temporomandibular joint. The degree of discomfort experienced by the patients was measured on the Visual Analog Scale (VAS).
 Ultrasonic therapy was administered on the bilateral temporomandibular joints and masseter regions 3 times at 5-day intervals. The patients reported the VAS values again at 5 days after the third session of ultrasound irradiation.
 All patients were divided into two groups—responders and nonresponders. Patients who showed a decrease in the VAS values following the therapy were considered as responders, whereas those who did not show a decrease were considered as nonresponders. The relationship between the presence or absence of any favorable therapeutic response and each pretreatment symptom was statistically assessed using Fisher’s exact test. Intergroup comparison of pretreatment VAS values was performed using Welch’s t test.
Results: Therapeutic responses were observed in 16 patients. Analysis of the data revealed that none of the pretreatment symptomatological factors were significantly related to the presence or absence of a clinical response to ultrasonic therapy, although there was a tendency for higher pretreatment VAS values in the nonresponders than in the responders.
Conclusion: The results indicate that a response to ultrasonic therapy cannot be predicted based on the assessment of the abovementioned 4 symptoms and the degree of discomfort.

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Purpose: Little is known about the connection between the Nobel Direct (ND; Nobel Biocare, Sweden) abutment head and the denture base when ND is used for an overdenture. This study evaluated the retentive force of several retainers for ND-retained overdentures.
Methods: The bodies of two sizes of ND [3.0-mm dia. (ND3.0); 4.3-mm dia. (ND4.3)] were embedded in a brass patrix frame (10×10×25 mm) by using autopolymerized polymethyl methacrylate (PMMA; Unifast II, GC Corp.). Four sizes of O-rings [O3 (1.6-mm dia.), O4 (1.9-mm dia.), O5 (2.8-mm dia.), O6 (3.8-mm dia.)], ND healing caps (HC; Nobel Biocare), and protection caps (PC; Straumann) were prepared for attachment matrixs. O3 to O6, ND, and PC were placed at the ND3.0 and ND4.3 abutment heads, respectively. As a control, the PMMA resin (RE) was directly used to connect the abutment head to the denture base resin without retainers. For ND4.3, the entire and upper-half of the abutment head was covered with the above materials to compare the different contact areas between the patrix and matrix. The connected patrix and matrix frames were mounted on a screw-driven mechanical testing machine (Model UTM II, Toyo Boldwin, Japan). The retention of double retainers (20-mm apart) were also measured with the angles of two ND4.3 abutment heads of 0, 6, and 12 degrees. The retentive force (n=5, N) obtained at a crosshead speed of 40 mm/min was analyzed by analysis of variance (ANOVA)/Scheffé’s test (α=0.05).
Results: The retentive force of ND3.0 and ND4.3 was significantly the greatest when O3 and PC, respectively, (P<0.05) were used. For ND3.0, the retentive force of O4, RE, and HC was one-third of that of O3. For ND4.3, the retentive force of RE and O5 was two-thirds of that of PC and that of O6 was one-third of the retentive force of PC. The retentive force of full contact was approximately two times greater than that of the upper-half contact. The angle of the two NDs did not affect the retentive force (P>0.05).
Conclusion: When the medium-sized O-ring, PMMA, and HC were used, an appropriate retentive force was obtained for the ND implant-retained overdentures.

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Purpose: The aim of this study was to investigate the factors that may influence the results of measurements of oral mucosal moisture using the new oral moisture checking device, especially in relation to the operator and the sensor cover.
Methods: Oral mucosal moisture was measured using a new oral moisture checking device (Mucus^®). To determine the influence of the operator on the measured values by the oral moisture checking device, 5 operators measured the oral mucosal moisture in 12 subjects. The differences were analyzed using the Friedman test. To determine the influence of the sensor cover, one operator measured the oral mucosal moisture in 12 subjects using two sensor covers. The differences were analyzed by Wilcoxon’s signed-rank test.
Results: The result of the Friedman test revealed the absence of any significant influence of the operator on the measured values of oral mucosal moisture by the oral moisture checking device. The results of the Wilcoxon’s signed-rank test revealed that the measured values of oral mucosal moisture by the measuring device differed by about 1.6 % between the two sensor covers (P<0.01).
Conclusion: The results of this study suggest that oral mucosal moisture can be measured using the new oral moisture checking device without any inter-operator error. However, there is some possibility of the measured values differing depending on the sensor cover used.

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Purpose: This study was performed to clarify the possibility of bone regeneration with a cell-hybridized artificial bone by evaluating bone formation in the beagle dog femur.
Methods: Bone marrow stromal cells (BMSCs) /interconnected porous hydroxyapatite (IP-CHA) composites as a cell-hybridized artificial bone were made by the injection of the BMSCs solution into IP-CHA. The distribution of BMSCs in IP-CHA was examined by scanning electron microscopy. Two BMSCs/IP-CHA composites (the BMSCs of one composite were labeled fluorescence) were placed into each of two bone sockets (φ3.7 mm×7 mm) prepared in the right femur of the beagle dog. After 4 weeks of surgery, new bone formation in the socket was examined by light microscopy and fluorescence microscopy.
Results: SEM showed well distribution of the injected BMSCs in the pores of IP-CHA. At 4 weeks, new bone formation was detected at the cortical areas of the composites, and injected BMSCs were identified in the new bone area of the interconnected pores.
Conclusion: The limited results of this study may suggest that BMSCs/IP-CHA composites as cell-hybridized artificial bone is a possible candidate for bone regeneration.

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Purpose: The clinical decision to use abutments for overdentures in cases with loss of tooth structure has not been fully assessed in relation to the periodontal condition. The aim of this study was to investigate the stresses around overdenture abutments with and without crown restoration for various bone heights.
Methods: Three-dimensional finite element models of the mandibular right first and second premolars, a periodontal ligament, and one of five alveolar bone models of different heights were constructed. The crown-to-root ratios at the second premolar were 0.86 (Model A), 1.05 (Model B), 1.28 (Model C), 1.56 (Model D), and 1.96 (Model E). The second premolar root was also modeled without crown restoration. A single oblique load of 80 N at a 30-degree angle distal from the vertical axis was directed at the center of the occlusal or root surface of the second premolar.
Results: The maximum stresses were observed at the distal cervical regions for all models. These increased as the crown-to-root ratio increased. The highest maximum stress in the cortical bone (35.8 MPa) was observed in Model E with crown restoration. In the regions near the overdenture abutments, the maximum stresses in the bone and the periodontal ligament were 33.9% to 61.7% lower than those observed near the crown restorations.
Conclusion: The use of the premolar as an overdenture abutment in cases with loss of tooth structure can effectively sustain the stress in the periodontal tissues, particularly under conditions of reduced bone height.

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Purpose: This study used a speech recognition system to investigate the intelligibility of the /∫/ sound, which is based on the palatal contour of complete dentures.
Methods: Six subjects with an edentulous maxilla participated in the study. The experimental dentures were made of self-curing acrylic resin and four curvatures (0, 2, 4, 6 mm) of the palatal contour were evaluated. A speech recognition program automatically converted the phonetic signals into phonetic segment labels. Labels that correctly recognized the /∫/ sound were defined, and the distribution of the correct labels was analyzed in relation to the palatal contour. Palatograms were also recorded to assess tongue movement.
Results: Repeated-measures one-way analysis of variance revealed a significant effect of the curvature of the palatal contour on the appearance ratio of the correct [∫i] labels (F=53.1, P<0.05). Tukey’s multiple comparisons revealed a significant difference between 0 mm and 2 mm (P<0.001), 0 mm and 4 mm (P<0.001), 2 mm and 6 mm (P<0.001), and 4 mm and 6 mm (P<0.001). Based on the appearance ratios of the [çi] labels, the 0 mm curvature of the palatal contour was rated as yielding the highest intelligibility (P<0.01), and based on those of the [t∫i] and [d ?? i] labels, the 6 mm curvature was rated as yielding the intelligibility (P<0.01 for both). When tongue movement was assessed from the palatograms, tongue contact was found to be similar to that in the typical palatogram for each recognized syllable.
Conclusion: The curvature of the palatal contour affects the pronunciation of the /∫/ sound, and the appropriate curvature of the palatal contour in complete dentures for correct pronunciation of this sound is 2 to 4 mm.

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Purpose: The aim of this study is to present a new procedure in dental practice to prevent aspiration or ingestion of restorations; this procedure is economical and applicable to many kinds of indirect restoration materials.
Methods: The jig comprises three rings in a line and bends at a right angle at the central ring. It is made of autopolymerizing acrylic resin that is molded with a self-made elastic mold. A 30-cm length of dental floss is tied to the ring at one side. The ring at the other side is glued with cyanoacrylate onto the non-occlusal surface of the restoration. If the ring does not properly fit the surface, a small amount of autopolymerizing resin may be brushed on it before gluing.
Results: After ensuring that the jig is fixed firm enough, the operators can try-in, adjust, and retrieve the restoration without concerns regarding aspiration/ingestion. After cementation, the jig can easily be removed from the restoration by using scalers.
Conclusion: This procedure allows us to decrease the risk of aspiration and ingestion of restorations in daily dental practice.

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