Purpose: Thermal shrinkage of mouthguard sheet material influenced the thickness after forming. The aim of this study was to investigate the elongation and thickness of mouthguard sheets in relation to the thermal shrinkage of the mouthguard sheet material.
Methods: Cross stripes (10 × 10 mm) were printed on mouthguard sheets. The length in the anteroposterior and bilateral direction was measured using vernier calipers, and the thickness of each cross stripe area was measured using a measuring device. The plaster cast was trimmed to the height of 20 mm at the upper central incisor and 15 mm at the upper first molar. The sheets were heated until they sagged 15 mm from the baseline. Two positions of the sheet were compared: the sheet became parallel (condition A) or vertical (condition B) direction to the thermal shrinkage of the mouthguard sheet material toward the cast. The difference in the ratio of change of the elongation and thickness between two conditions was analyzed by paired t-test and Wilcoxon signed-rank test. Additionally, the relationship between the elongation and thickness of the sheets was investigated by regression analysis.
Results: The elongation in the part of the sheet fitted to the anterior teeth and posterior teeth of condition A was smaller than that of condition B. The thickness in the part of the sheet fitted to the palate and posterior teeth of condition A was smaller than that of condition B. The relationship between the elongation and thickness of mouthguard sheets was modeled by a quadratic equation.
Conclusion: This study suggests that the thickness of the part of the sheet fitted to the palate and posterior teeth, which was parallel in direction to the thermal shrinkage of the mouthguard sheet material toward the plaster cast, was thinner than that of the vertical direction.

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Purpose: For an appropriate diagnosis of removable dentures, it is important to assess the biomechemical characteristics of the denture-supporting tissues.
The relationship between the thickness and elasticity of the denture supporting tissue was examined separately with an ultrasonic thickness gauge and a tactile sensor. However, separate measurements were difficult to apply clinically. In an effort to assess the viscoelasticity of the oral mucosa, the usefulness of a newly developed simultaneous measuring system of load and thickness was evaluated. This study outlines the establishment of a simultaneous measurement method for load and change of the mucosa thickness.
Methods: An ultrasonic thickness gauge (25 DL.PLUS., OLYMPUS NDT JAPAN INC.) of 90° probe and 45° probe with a strain gauge attached on the handle, enables measurement of the thickness and load simultaneously. Measurement conditions were a maximum load of 3.0 N with a measurement time of 15 sec. For the simulated oral mucosa, soft denture liners (Supersoft., TOKUYAMA DENTAL) with a thickness of 3.0 mm and the palate mucosa of a dentate individual, were used.
Results: Calculated elasticity of the 45° probe was as good as the 90° probe. For the palate mucosa, calculated elasticity can be assessed by the 45° probe.
Conclusion: The usefulness of this new system with the 45° probe was revealed and the possibility of assessing the viscoelasticity of the oral mucosa was suggested by measuring the load and thickness simultaneously.

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Purpose: Humans show laterality with a main chewing side showing a high frequency of use in the stomatognathic system. However, there have been few suggestions for prosthetic treatment in consideration of the chewing side. The present study therefore compared mandibular movement between chewing on the main chewing side and on the non-main chewing side, and also by age group and food texture. The objective was to obtain suggestions for prosthetic treatment.
Methods: The subjects comprised 30 people with dentulous jaws. Evaluation of the main chewing side was performed on the side showing the higher frequency of 20 strokes after initiation of chewing. For measurement of mandibular movement during chewing, a jaw movement-measuring device with six degrees of freedom was used. Study items were chewing on the main chewing side and chewing on the non-main chewing side using beef jerky and gummy jellies, a type of candy. The jaw-closing angle of the lower incisors, length of condylar trajectory during activity of the jaw-closing muscles and maximum velocity of condylar movement were compared. Comparisons were also made by age group and by test foods.
Results: With chewing on the main chewing side, the jaw-closing angle of the lower incisors was greater, length of condylar trajectory on the balancing side tended to be longer and maximum velocity of condylar movement tended to be greater than on the non-main chewing side. These tendencies were more marked in middle-aged subjects. No differences were found among test foods.
Conclusion: Chewing on the main chewing side showed a marked tendency to be the grinding type, and the difference by age was assumed to be more marked because of occlusal wear centered on the main chewing side. Clinically, bilaterally symmetric prostheses are not necessarily optimal and it is suggested that prosthodontic treatment should consider functional morphology.

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Purpose: For the colorimetric evaluation of ceramic blocks for CAD
CAM, we analyzed the color space of natural teeth, and colorimetrically compared natural teeth with ceramic blocks.
Methods: We measured the color of healthy maxillary central incisors of 200 males and females and ceramic blocks for CAD
CAM fabrication of all-ceramic crowns using a colorimeter for dental use (Crystaleye Spectrophotometer®). Using blocks, which are cut into the crown contour and polished, samples (1.5 mm in thickness) were prepared and placed on background samples, and color was measured. Colorimetric data of natural teeth were analyzed and compared with those of ceramic blocks.
Result: Concerning the color space of natural teeth, a decrease in L*, increases in a* and b*, and an associated increase in C* with age were observed. Concerning the color space of ceramic blocks, the percentage of ceramic samples showing a color difference from natural teeth ≤ 3.0 decreased with age.
Conclusion: Natural teeth showed a decrease in brightness and increases in red and yellow with age. With age, discrepancy in the color space between ceramic blocks for CAD
CAM and natural teeth was observed. To improve this discrepancy and obtain a color space close to that of natural teeth, blocks located in color spaces that are less bright and redder than those of existing ceramic blocks are necessary.

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Patient: A 58-year-old woman visited our hospital with the chief complaints of masticatory disturbance and disharmony of jaw movement due to partial dental defects in the upper and lower jaws. Closed bite of the frontal teeth and a lack of denture space on the left side were observed.
Discussion: Left posterosuperior mandibular and anterior shifts of the left articular disk were present on X-ray and MRI, for which prosthetic treatment with bite-raising was necessary. Since it was difficult to determine the final jaw position at the time of treatment initiation, additional examinations were performed during treatment to assess the jaw position. Treatment dentures were attached, and the jaw was guided to an adequate position by occlusal adjustment. No particular problem occurred during follow-up for more than 4 years.
Conclusion: Attachment of treatment dentures and guidance of jaw position improved masticatory and jaw movement disturbances.

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Patient: The patient was a 62-year-old female who had partial edentulous spaces on maxilla with chronic periodontitis. Resin-bonded fixed partial dentures were installed for these edentulous spaces to recover functional disorders.
Discussion: A resin-bonded fixed partial denture was bonded for a missing maxillary right first premolar. After 3 years, the bonded metal retainer on the maxillary right canine became debonded. There was no trouble in this abutment tooth because of the minimum intervention, so it was restored again using the same method with some modification. Another resin-bonded fixed partial denture was installed for a missing maxillary left second premolar and first molar and the mobility teeth were also fixed with this prosthesis. No prosthetic or periodontal complication was observed for a further 3 years after replacement.
Conclusion: The resin-bonded fixed partial denture technique in this case of chronic periodontitis with mobility teeth provided satisfactory long-term functional results for this patient.

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Patient: The patient was a 71-year-old female who complained of esthetic disturbance. Further examination revealed trismus and an erroneous horizontal and vertical maxillomandibular relationship. Therefore, treatment of the maxillomandibular relationship using an occlusal splint was given priority over other treatments.
Discussion: The initial prosthodontic treatment by shortening the dental arch was difficult because it was not possible to maintain an appropriate maxillomandibular relationship. However, the final prosthodontic treatment using a fixed partial denture establishing a proper occlusal plane and anterior guidance, together with a removable partial denture with sufficient support and bracing, restored the esthetic appearance and function, and maintained a good condition for three years.
Conclusion: This case report suggests that for esthetic restoration, it is necessary to have a proper maxillomandibular relationship and anterior guidance based on an accurate diagnosis.

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Patient: The patient was a 45-year-old female who complained of the discomfort of a removable maxillary partial denture. To solve her chief complaint, an implant-supported fixed partial denture was selected for her maxillary partial edentulousness.
Discussion: The chief complaint was improved by replacing the removable partial denture with the implant prosthesis. The results of a questionnaire showed that this patient was satisfied with the treatment for the maxillary partial edentulousness. During the recall period of 3 years and 6 months after the final restoration, progressive inflammation of the implant body or fracture of the superstructure body have not been found.
Conclusion: Implant prosthesis is useful for overcoming the discomfort of an unsatisfactory removable partial denture.

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Patient: A 57-year-old female complained of mastication disorders and dissatisfaction with dental esthetics. Occlusion collapse due to a defective prosthesis and partial anodontia, a decrease in occlusal vertical dimension, and unequal occlusal plane levels was diagnosis, Occlusal reconstruction was performed on the patient. The prosthesis was completed with a cone crown telescope in the maxilla and anchored with an implant in the mandible, and the patient had a good clinical prognosis for 7 years.
Discussion: A cone crown telescope denture in the maxilla is expected to impart a secondary immobilizing effect by providing rigid support and distribution of the occlusal force by integrating the occlusal plane into a single unit. Additionally, an implant in the mandible enables fixation of the prosthesis.
Conclusion: Oral reconstruction provided a long-term stable oral environment which applied with cone crown telescope and implant in a patient with occlusion collapse.

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Patient: A 60-year-old woman with a bilateral distal-extension edentulous ridge and heavy periodontitis with severe tooth mobility and deep periodontal pockets visited this clinic with masticatory problems. The patient strongly requested an implant prosthesis and maintenance of the oral function and aesthetics during the treatment period. For this purpose, a fixed free-end saddle-bridge appliance was modified as a temporary prosthesis (modified FESB) to treat the periodontitis and to protect the implant from harmful force. The modified FESB was used until fabricating a superstructure. Six months later. implant treatment was performed, and successful therapeutic results were obtained.
Discussion: Application of the FESB maintained the desired esthetics and oral function with the resultant intended treatment effect.
Conclusion: This case shown that application of modified FESB in implant treatment was effective for improving the predictability of implant treatment as wells as the patient's quality of life.

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Patient: The patient was a 60-year-old male with a chief complaint of chewing difficulty. The diagnosis was masticatory dysfunction caused by loss of mandibular molars. Final restoration was made with a fixed prosthesis incorporating a dental implant.
Discussion: In cases with free-end missing, occlusal reconstraction using a dental implant enables complicated oral situations to be improved functionally and esthetically. After 5 years of use, the final restoration and dental implant were in satisfactory condition.
Conclusion: By comparing the electromyogram of masseter muscles before and during treatment with provisional restoration, improvement of the masticatory dysfunction was confirmed. Therefore functional diagnosis is useful for prosthetic treatment.

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Patient: The patient was a 61-year-old male with severe periodontal disease that caused the loss of his molars and intercuspal position. He received initial periodontal treatment, followed by occlusal reconstruction with temporary treatment dentures. After the periodontal disease was cured by periodontal surgery, a definitive prosthesis was provided.
Discussion: Although the patient had not yet lost all of his teeth, radiographic findings at the first dental examination indicated that it would be difficult to save the remaining teeth. Seven years have now passed after completion of the final prosthetics. In this case, it was important to reconstruct the vertical dimension by dentures, provide a splint for the remaining teeth with a fixed prosthesis and perform continuous maintenance after treatment.
Conclusion: This case showed that teeth with severe periodontal disease could be maintained over the long-term using a suitable periodontal prosthesis.

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Patient: The patient was a 57-year-old female who presented with chief complaints of esthetic and masticatory impairment. The patient had masticatory disorders and anterior cross-bite I due to infraocclusion. An occlusal splint was used to confirm the bite rising. After occlusal stability had been confirmed, porcelain fused metal crowns were fitted as permanent prostheses.
Discussion: The removal occlusal splint for bite rising was easily adjustable and the existing restorations could be removed. Predictable prosthetic treatment with occlusal reconstruction could be performed by using the removal splint and provisional restorations for approximately two years.
Conclusion: The removal occlusal splint was effective for increasing the occlusal vertical dimension.

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Patient: A 33-year-old male patient, who sought treatment for a tooth fracture on the upper-central incisor at the sub-alveolar bone level, was referred to our clinic. The tooth was extruded by minor tooth movement and was finally treated by fusing porcelain to a metal crown with a metal core.
Discussion: The treated tooth showed a good course after insertion of the final restoration. This may have been due to reinforcing the biologic width by tooth extrusion.
Conclusion: Tooth extrusion should be included as a treatment option for root fracture below the sub-alveolar bone level, although the crown-root ratio would be increased. This report verified that tooth extrusion is an effective treatment, provided that an appropriate investigation of all possibilities, such as compensation of tooth strength, is performed.

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