Purpose: This study aimed to define the relationship between satisfaction of wearing denture and three factors (“easy to chew”, “retention in chewing”, “absence of pain”), as well as the missing teeth pattern with Miyachi classification, the chewing ability.
Methods: A total of 256 subjects (born in 1927) living in Niigata city, Japan who had answered a questionnaire survey in 2007 on the relationship between oral health and health status were selected for this study. Satisfaction with dentures and three factors (“easy to chew”, “retention in chewing”, and “absence of pain”) were evaluated with the VAS score. This study also investigated grouping the pattern of missing teeth based on the Miyachi classification. In addition, a questionnaire was conducted to investigate whether the elderly people could chew around 15 different food items or not.
Result: It was clearly shown that satisfaction with dentures was correlated with the three points of chewing easily, stability, and pain-free among elderly people. However, none of the three points showed a far stronger correlation than the others. The results also showed that there was no relation between the missing teeth pattern classified with the Miyachi classification and satisfaction with dentures. The results of the questionnaire revealed that the number of food items taken by the elderly people was significantly lower in the group not satisfied with dentures than the other groups (Excellent, good, poorly satisfaction group).
Conclusion: It was confirmed that chewing easily, stability and pain-free enhance satisfaction with dentures. However, satisfaction with dentures was not ascribed to the pattern of missing teeth; accordingly, we consider that we can keep elderly people satisfied by fabricating good dentures and performing appropriate adjustments regardless of difficult patterns of missing teeth.

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Purpose: Purpose: The purpose of this study was to determine the potential role of oxidative stress in generating cytotoxicity of self-curing polymethyl methacrylate (PMMA) dental resin to oral mucosal cells and to understand its cellular mechanism.
Methods: Rat palatal gingival tissue-derived oral mucosal cells were seeded on self-curing PMMA-based dental resin or on a culture-grade polystyrene dish. A cell viability test and detection of apoptotic biochemistry markers using a flow cytometer, total concentration of glutathione (GSH) colorimetry, and fluorescent quantification of intracellular reactive oxygen (ROS) were performed at 24 hours after seeding.
Result: Only 0.2% of the oral mucosal cells were viable on the PMMA dental resin 24 hours after seeding compared with 85% or more on polystyrene. The cells on the PMMA resin exhibited strong positiveness of molecular markers indicative of cell membrane breakdown and apoptosis. Moreover, substantial elevation of intracellular ROS elevation and a decrease of total GSH concentration were found in the cells on the PMMA resin.
Conclusion: Considerable cell death characterized by a large increase of active caspases and cell membrane collapse was induced in palatal tissue-derived oral mucosal cells seeded on auto-polymerized PMMA-based dental resin. It was suggested that oxidative stress contributed to the cell death. These results help to clarify the mechanism underlying the cytotoxicity of PMMA-based dental resin to oral mucosal cells.

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Purpose: The sense of taste is conventionally evaluated by putting some taste solutions into the mouth and then investigating the taste perception threshold. However, there have been few studies examining the spread of taste in the mouth in terms of masticatory process. The purpose of this study was to develop a new gustatory test depending upon a quantitative evaluation of the spread of taste by counting the number of chewing strokes needed to recognize the taste at designated areas of the mouth.
Methods: Forty-three subjects without missing teeth (19 females and 24 males, mean age: 30.0 years) were selected for this study. Newly designed sample foods made from 3% agarose containing 2% or 5% sucrose were prepared. The subjects were instructed to chew the sample foods and the number of chewing strokes was counted until they recognized sweetness at either a small area or the whole area of their tongues.
Results: Female subjects required fewer chewing strokes to perceive taste than male subjects for the 5% sucrose sample food. The number of chewing strokes increased as the taste spread on the tongue, and the number decreased with higher concentration of the sample.
Conclusion: The findings suggested that counting the number of chewing strokes to recognize the spreading of taste would be useful as a new gustatory test to clarify the sensation of taste.

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Purpose: The effect of a mouthguard (MG) on the temporomandibular joint remains unclear. In this study, we aimed to clarify how differences in the occlusal MG support affect condylar displacement during clenching, by determining and examining the condylar displacement during maximal voluntary clenching (MVC) for three different kinds of occlusal support.
Methods: The study consisted of ten healthy adults (mean age:27 years) with healthy natural dentition. Three different kinds of occlusal MG support were prepared (Type 77 provided occlusal contact for all teeth, from the anterior teeth to the second molar; Type 66 provided occlusal contact up to the first molar; and Type 47 provided only posterior occlusal contact). Condylar displacement during MVC was determined by the Win Jaw system® (ultrasonic motion analyzer) for the intercuspal position (ICP) and while wearing the three kinds of MG support.
Results: Compared to ICP, the extent of condylar displacement during MVC was significantly greater for superior displacement of Type 77 and Type 66.Furthermore, compared to ICP data, anteroposterior displacement was significantly greater for Type 66,and was significantly greater for Type 66 and Type 47, compared to Type 77.
Conclusion: It was also found that loss of anterior or posterior occlusal support decreased anteroposterior stability. There was significant individual variation in the distance and direction of condylar displacement under each occlusal support condition. This study could not identify which occlusal support condition was better.

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Purpose: Mouthguards are intended to provide protection from stomatognathic injury during sports. The aim of this study was to investigate the thickness of mouthguard sheets after the vacuum forming process in relation to the color of the mouthguard sheet material.
Methods: Cross stripes (10×10 mm) were printed on to the mouthguard sheets. We measured the thickness of each cross stripe area using a measuring-device®. The color of the mouthguard sheet material was white (MG-W) or purple (MG-P). A cast was made by taking an impression of a maxillary dental model using silicone rubber replicate impression paste, and then gypsum was poured onto the impression. The plaster cast was trimmed to the height of 20 mm at the incisal edge of the upper central incisor and 15 mm at the medial buccal cusp of the upper first molar. The sheets were heated until they sagged down 15 mm (condition A), 30 mm (condition B), and 45 mm (condition C) from the baseline. The difference in the ratio of changes in the thickness of two mouthguard sheet materials was analyzed using the paired t-test and the Wilcoxon signed-rank test.
Results: The results indicated that all parts of the sheet mounted on the cast decreased in thickness. The ratio of changes of the thickness in the part of the sheet fitted to the anterior teeth and palate on MG-W was greater than that of MG-P under the three heating conditions (p<0.01). In addition, the thickness of the part of the sheet fitted to the posterior teeth on MG-W was greater than that of MG-P under condition A (p<0.01).
Conclusion: The results of this study suggested that the thickness of the mouthguard sheet after forming was affected by the color of the sheet material under the same heating conditions.

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Purpose: Despite their superior physical properties, problems such as breakage have been reported with castable ceramics. The present study investigated the effects of several reinforcement techniques, including the use of bonding materials and porcelain, on the strength of Olympus castable ceramics (OCC) fabricated by electroforming.
Methods: A total of 24 test samples were created, including six 3×4×24 mm samples of each of the following four types: 1) OCC attached to a gold frame (GF) by electroforming (GO); 2) OCC with a porcelain bonding material (GBO), 3) and porcelain (GBPO); 4) and OCC only (O). Reinforcement effects were assessed using a three-point bending test. Additionally, maxillary left central incisor samples were created and subjected to compression testing under the optimum conditions.
Results: The results of the three-point bending test indicated that the average bending strength of GO was significantly higher than that of O, GBO, and GBPO (p<0.05). There were no marked differences among O, GBO, and GBPO. The results of compression testing indicated that the compressive strength of GO crowns was significantly higher than that of OCC crowns (p<0.01).
Conclusion: While bonding material and porcelain did not effectively reinforce OCC, the results of compression testing performed on GO crowns suggested that gold coping by electroforming could serve to reinforce the strength of OCC.

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Patient: A 27-year-old female had undergone partial mandibulectomy under the diagnosis of mucoepidermoid carcinoma. The temporary denture was placed after 17days postoperatively. After the forearm flap became stable, the final denture with hand-made artificial porcelain teeth fabricated and frozen muddy porcelain method (P-C•P•F) was inserted. The patient was followed for 8 years with no complications.
Discussion: Both pre-surgical impression and P-C•P•F method contributed to the recovery of appearance and function in the early post-operative stage. This method allows the preoperative state of dentition to be precisely reproduced.
Conclusion: This report suggests usefulness of P-C•P•F method applied in the maxillofacial prosthetic patients who lost a lot of teeth by tumor resection.

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Patient: The patient was a 47-year-old female who complained of difficulty of mastication and esthetic disturbance with molar defects and anterior teeth crowding. She underwent occlusal reconstruction with dental implant for right side maxillary and left side mandibular molar defects and orthodontic treatment for anterior teeth.
Discussion: Provisional metal superstructures for dental implants were effective to keep stable occlusion during orthodontic treatment and worked as the anchorage source for active treatment of anterior teeth crowding. The trouble free metal provisional restoration was also practical to adjust occlusal position before and after the orthodontic treatment.
Conclusion: The occlusal reconstruction with orthodontic treatment requires long tern treatment period. In such cases, reliable provisional metal restoration is the most suitable to obtain satisfactory outcome.

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Patient: The patient was a 65-year-old male, suffering from chronic pain in the head-neck-back region. The pain was initiated by placement of bite-raising prosthetic restorations in his lower bilateral molar area at some dental clinic. After removal of the prosthetic restorations, provisional restorations with decreased vertical dimension were inserted. The intercuspal position of the provisional restorations was established at the position with the anterior teeth in contact together on his habitual open-close trajectory. After few month observation of the pain reduction the final prosthetic restorations replaced the provisional restoration.
Discussion: During 4-year follow up period, he has not complained any exaggeration of the chronic pain. Thus, the previous prosthetic restorations with increased vertical dimension might induce the symptoms in his head-neck-back region.
Conclusion: It was suggested that chronic pain in the head-neck-back region could sometimes be related to iatrogenic malocclusion produced by intraoral prosthetic restorations.

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