In 1982 the Health and Medical Service Law for the elderly was enacted. Until 1982 medical services for the elderly were provided free or charge in Japan, causing rising health expenditure on the elderly. One purpose of the law was to introduce partial cost-sharing and health services for the elderly, but dental health services were not included in the Law. The 8020 Movement was therefore initiated to include dental health within the health service of the Law. The“8020”goal is based on research which reported that it is possible to eat almost all kinds of food with 20 teeth. In 1989 the Committee for Adult Oral Health of the Ministry of Health was established and as an objective for on oral health campaign, the 8020 Movement was proposed. Since 1992, activities for the 8020 Movement by local governments have been supported by the Central Government, initiating the success of the 8020 Movement.

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The tooth conditions of Japanese people have improved year by year, and it may be possible to achieve 8020 in the near future. On the other hand, over 40% of people had experienced prosthodontic treatment including dentures and bridges between the age of 45-54, and about 80% between the age of 65-74. Therefore, the rate of people who have a prosthodontic crown in their mouth are thought to be higher even in the young population. Prosthodontic treatment is important for recovering from severe defect of caries or for controlling occlusal trauma derived from malocclusion. However, it is difficult to manage prosthetically treated teeth for a long time in the oral environment because their treatments have been done for those who still have the risk of missing teeth. In this report, the relationship between achieving 8020 and prosthodontic treatment is discussed with the results of a study on extraction causes and the risks of prosthetically treated teeth. The results showed that the main cause of extraction of prosthetically teeth was periodontal disease, that 74.1% of the prosthetically treated teeth were non-vital, and that the prevalence of root fracture was different between vital and non-vital. These findings suggested that the comparison of the cause of missing teeth, especially, the risk of missing prosthodontically treated teeth, should be discussed after the standardization of periodontal conditions.

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Purpose: In order to reveal the relationship between 8020 movement and prosthodontic treatments, a systematic review was conducted concerning the clinical questions of 1) whether the longevity of abutment teeth is extended by prosthodontic treatment, 2) whether prosthodontic treatment can help extend the longevity of remaining teeth.
Methods: In order to determine the survival rate of the crown and bridge, the prognosis of the abutment of crowns and bridges, the influence of removable partial denture and dental implant therapies on the survival of remaining teeth, and the survival rates of remaining teeth between when the teeth adjacent to missing teeth are treated prosthodontically and when not treated, a systematic review using computer online searches was conducted.
Results: The following results were obtained: 1) Troubles rapidly increase 13 years after the placement of crowns and bridges. One-third and one-half of crowns and bridges can lose their function in 15 and 20 years after placement, 2) Crowns and bridges can extend the longevity of their abutment teeth, and 3) Implants and bridges can help extend the longevity of the remaining teeth.
Conclusions: The clinical impacts of prosthodontic treatments on the 8020 movement cannot be neglected, since crowns and bridges and implant therapies can extend the longevities of abutment teeth and teeth adjacent to edentulous spaces treated by implant.

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The “8020” objective seems difficult to achieve, but at least 20 teeth are needed based on difficult cases of defective dentition. Our clinical experience shows that at least 18 teeth are needed to keep 4 occlusal supports. If the number of occlusal supports falls below 4, defective dentition may easily deteriorate to more clinically difficult cases. From our long-term experience, patients over 80 years old who still have 20 teeth usually have stabilized occlusal supports, while many cases who have partially lost their occlusal support do not achieve the 8020 goal. Prevention of partial defects of teeth for restoration of caries and active prosthesis for defects are important to achieve the 8020 goal. Furthermore, continuous follow-up and preventive support are important. If continuous clinical correspondence is possible, 8020 may be achievable in about 80% of all cases.

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Purpose: The aim of this study was to evaluate the combination of TAK-778-SR which was sustainedrelease microcapsules of a bone formation stimulant, TAK-778, and its carrier β-tricalcium phosphate (β-TCP) blocks (pore rates 60%, 75% respectively).The difference of their abilities in boneformation was evaluated histomorphologically by varying the following conditions: with or without TAK-778, pore ratio of carrier and embedding period.
Methods: Nine-week-old female SD rats were used. After removing the parietal bone from the head with a trephine bar, the defects were refilled by β-TCP blocks immersed with or without TAK-778 under the following conditions: saline solution, release microcapsules only, and release microcapsules with TAK-778 (TAK-778-SR).These rats were sacrificed after 5 and 10 weeks and their histological specimens were prepared.Morphological change was observed and the formation rates of each new bone were compared using an NIH imaging program.
Results: A significant amount of new bone was morphologically observed in all β-TCP samples that were treated with TAK-778-SR.A high rate of new bone formation was confirmed in the 10-week samples (pore rate 75%, with TAK-778-SR) with the NIH imaging.
Conclusions: 1.β-TCP and release microcapsules did not disturb the recovery process.2.Five-and 10-week samples (pore rate 60%) were absorbed marginally.3.Absorption was observed in the 5-week samples (pore rate 75%), and it was accelerated further at 10 weeks.4.An accelerating boneformation effect of TAK-778-SR was confirmed and β-TCP block was proved to be highly useful as a carriage material.

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Purpose: This study investigated the correlation between strength of sleep bruxism and dislodgement of dental restorations, by both using the facet index of occlusal splint for sleep bruxism and measuring the dislodgement rate of dental restorations.
Methods: Subjects consisted of 422patients with 3673 dental restorations (inlay, crown, jointed crowns, and bridge) referred to the hospital from 1976 to 2004 who were randomly selected from 912 patients. All patients wore an occlusal splint during sleep. Ink was placed on the occlusal part of the splint and the strength of sleep bruxism was evaluated by the wearing away of the ink and indentation on the splint (Ikeda's method). The subjects were classified into the following four groups according to the evaluation: B-0: no facet on the splint, B-1: slight facet with wearing of the ink but no indentation on the splint, B-2: slight indentation on the splint, and B-3: notable indentation on the splint, and then the dislodgement rate between the groups was compared. The mean evaluation time in each patient was 10.1years.
Results: The rate of patients with dislodgement was B-1: 12.7%, B-2: 35.1%, and B-3: 43.8%. The dislodgement rates of categorized restorations in groups B-1, B-2, and B-3 15years after the placement were, restorations: 9%, 18%, and 24%, inlay: 19%, 24%, and 32%, and crown: 5%, 12%, and 13%, respectively.
Conclusions: It is proved that the evaluation method using the facet index of occlusal splint for sleep bruxism is a reliable means of estimating how long the restoration will last. The results showed that sleep bruxism influences the dislodgement of restorations. To protect restorations, it might be effective to control the load from sleep bruxism.

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Purpose: The purpose of this study was to determine whether rotation and translation of the condyle were useful parameters for identifing causes of limitation of mouth opening in patients with temporomandibular disorders (TMD).
Methods: In 7 healthy volunteers and 55patients with TMD, rotation and translation of the condyle were measured using a 6degree-of-freedom jaw movement tracking device. Patients were divided into two groups: those who could open their mouth 40mm or greater, and those who could not open their mouth 40mm. In each group, the relationship of rotation and translation of the condyle to maximum mouth opening, condition of the articular disc, and pain was determined.
Results: Both correlations between maximum mouth opening and rotation and translation of the condyle were strong, especially the former correlation. There was no marked difference in the distribution of range of mouth opening, and rotation and translation of the condyle with respect to condition of the artticular disc. Muscle pain was associated with reduced mouth opening. Even in patients without limited mouth opening, their range of mouth opening was actually reduced when they had muscle pain. Among the patients with limited mouth opening, joint pain correlated to limited translation of the condyle. However, in patients with Wo-Wo condition of articular disc, their translation of the condyle was not limited even with joint pain, but it was limited with muscle pain.
Conclusions: Rotation of the condyle indicated strong correlation with muscle pain, and so is a useful parameter for estimating treatment methods by a surgical approach. On the other hand, translation of the condyle showed variations in correspondence with combinations of several factors such as opening limitation, condition of the articular disc, and pain.

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Purpose: Powder metallurgy is a metal processing technology.Porous titanium produced from powder is widely used.The method is applied to titanium, which is not easy to cast as it sinters under melting point. In prosthetic dentistry, powder metallurgy can be applied to high fusing metal that is biocompatible.In this study, we examined the mechanical characteristics of the Ti sheet produced by sintering and discussed its application to dental prosthesis manufacturing.
Methods: Ti sheets of 1-mm thickness, in which a binder was added to spherical Ti powder, were produced with the Doctor Blade Method. The sintering was carried out between 900-1150°Cat 6 temperatures.The sintered compact was evaluated by dimensional change rate, hardness test, bending strength, tensile strength and SEM observation.Another compact was sintered on the refractory cast.
Results: Mechanical strength significantly increased with sintering temperature.In addition, excellent mechanical strength was acquired by adding crushed powder and performing the de-binder process. In the sintering on the refractory cast, pre-baking for more than 100 minutes and sintering at over 1050°C was needed for practical application.
Conclusions: It thus seems possible to apply sintered titanium to dental prostheses.However, it will be necessary to examine the control of the shrinkage of the sintered compact in the future too.

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Purpose: The purpose of this study was to clarify the effect of holding condition with different prism length on the Notchless Triangular Prism (NTP) fracture toughness test and to define the prism length as a measuring condition.
Methods: Two kinds of NTP prism (ceramic and composite resin) were fabricated by CAD/CAM and each prism was adjusted to one of three lengths (8.0 mm, 12.0 mm, 16.0 mm).NTP was conducted for prism specimens made under six different conditions.The displacement of prism specimen holder gap (M) and maximum fracture load (Pmax) were recorded and then a fractogram of each prism was inspected by SEM.
Results: Inclined stable fracture propagation was observed on the fractogram of the 8.0-mm prism. Both Ad and Pmax of the 8.0-mm prism were significantly higher than those of the other lengths.
Conclusions: A prism length of at least 12.0 mm is needed for the NTP because the 8.0-mm prism did not have a sufficient holding condition. The fracture toughness of the ceramic (3.68±0.09 MPa·m^1/2) was significantly higher than that of the composite resin (2.38±0.20 MPa·m^1/2).

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Purpose: We surveyed youths and denture wearers to evaluate the feeling of oral dryness. In the denture wearers group, we evaluated the association between dentures and feeling of oral dryness.
Materials and Methods: The survey was performed in 100 denture wearers (mean age, 66.2±8.6 years) who visited our department from June to October 2003. A similar survey was performed in 50 youths (mean age, 25.6±2.4 years, 20-29 year-old group). The survey consisted of a questionnaire and oral and denture examination. The questionnaire asked about oral dryness symptoms, general condition and current medications. The oral and denture examination examined the condition of the remaining teeth, the kinds of prosthesis, materials of dentures and form of the denture base.
Results: A feeling of oral dryness was observed in 11 of the 20-29 year-old group (22%) and 48 denture wearers (48%), hence the incidence was significantly higher in the denture wearers group (p<0.01). No association was observed between the oral dryness symptoms and age, sex, general condition, current medications, or number of residual teeth. The kinds of prosthesis (no denture, partial denture, complete denture) and form of the denture base have no relationship with the feeling of oral dryness.
Conclusions: 48% of the denture wearers had the feeling of oral dryness, and the incidence was higher than in the 20-29 year-old group. However, no association was observed between the oral dryness symptoms and dentures. Further studies are necessary to evaluate factors associated with the development of the feeling of oral dryness.

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Purpose: We surveyed youths and denture wearers to evaluate the feeling of oral dryness.
Materials and Methods: The survey was performed in 100 denture wearers (mean age, 66.2 ± 8.6 years) who visited our department from June to October 2003. A similar survey was performed in 50 20-29 year-old persons (mean age, 25.6±2.4 years). Measurement of the height of the salivary moisture area, and detection of Candida were performed. We used Saliva Wet Tester for measuring the height of the salivary moisture area.
Results: The mean height of the salivary moisture area was significantly lower in the denture wearers group than in the 20-29 year-old group (p<0.05). No association was observed between the height of the salivary moisture area and general condition, current medications, number of residual teeth, or the denture base. In the denture wearers group, the height of the salivary moisture area was high in patients with bounded saddle dentures or unilateral distal extension dentures in either or both jaws but low in those with dentures covering the entire palatal and lingual mucosa in both the upper and lower jaws. However, the feeling of oral dryness was not always consistent with the height of the salivary moisture area. In the denture wearers group, the height of the salivary moisture area matched the low tendency of detection of Candida of 100 CFU or more in patients.
Conclusions: The mean height of the salivary moisture area was significantly lower in the denture wearers group than in the 20-29 year-old group. However, the feeling of oral dryness was not always consistent with the height of the salivary moisture area. Further study, including a mental factor, is necessary.

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Purpose: An oral moisture checking device is easy to use for the examination of oral dryness during clinical procedures. This study examined the usefulness of an oral moisture checking device.
Methods: The subjects in the examination of factors that influence the measured value of the oral moisture checking device were 16 sound adults (mean age 27.5). The subjects in the examination of measuring the moisture of sound adults were 32 adults (mean age 24.4). In the factors that influence the measured value of the device, the measuring pressure was examined by comparing the measured value with a trial stopper and without the stopper. The factor of sensor cover was examined by comparing the measured value before and after changing the sensor cover. The factor of device was examined by comparing the measured value using the two devices. The moisture of sound adults was measured at the lingual mucosa and buccal mucosa.
Results: The measured value with a trial stopper was lower by 0.2-0.3% than that without the stopper. The measured value differed before and after changing the sensor cover by 0.5-0.8%. The measured value was not different among devices. The mean value of the moisture of sound adults was 30.6±0.3% at the lingual mucosa, and 30.9±0.3% at the buccal mucosa.
Conclusions: The measurement errors of the oral moisture checking device were within 1% under the condition of proper measuring pressure. Additionally, the moisture of sound adults converged toward definite values. The results of this study suggested that the oral moisture checking device is useful for the examination of xerostomia.

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Patient: The alveolar bone and teeth for a patient involved in a traffic accident were prepared using removable partial dentures with I-C attachment.
Discussion: Because of using no clasp in the front teeth, sufficient supporting force of the dentures and no throbbing pain after insertion of the dentures, the patient was fully satisfied with the appearance and functional results of the treatment.
Conclusion: In a case of loss of front teeth, the patient was content with the smaller and esthetically excellent attachment instead of a clasp. Moreover, the patient is progressing favorably. It is considered that the I-C attachment was effective for this case.

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Patient: The patient (57-years-old female) suffered from severe chronic periodontitis in the maxillaryand mandibular molar regions. After extraction of these teeth, treatment dentures were immediatelyplaced in the maxilla and mandible to restore the occlusal-supporting area. Final denturetreatment was done by adjusting the provisional dentures according to the patient's concern. Goodprognosis was obtained during 9 years.
Discussion: To restore bilateral occlusal-supporting areas, treatment dentures reduced the loss ofremaining teeth.
Conclusion: Treatment dentures can stabilize the occlusal relationship immediately after loss ofocclusal-supporting area, and may also contribute the patient's acceptance of and satisfaction with thefinal prostheses.

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Patient: The patient was a 19-year-old man who visited the hospital with chief complaints of headache, stiffness of shoulders, and giddiness. The skull, mandible, and splint, and their relation withcervical vertebra, were considered, and new knowledge was acquired. Since the fulcrum of themovement axis at the time of opening and closing had shifted below the dens, it was diagnosed as TMD. Splint treatment was performed and the main symptoms had improved 3 months later.
Discussion: It is thought that the jawbone of the upper and lower sides of class II occlusion hadadapted to class III, and would cause various whole-body conditions.
Conclusion: Although the influence of the posture of cervical vertebra and the whole-body deformationof submaxilla is considered, there are many unknown points and further study is required.

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Patient: A 50-year-old female patient with minor maxillary defect was afflicted with an ipsilateraloroantral fistula. A unilaterally designed obturator was constructed for the patient. She was satisfiedwith the obturator because no leakage or seepage into the antrum occurred during mastication. Itwas also aesthetically acceptable due in particular to the small size of the denture. In this clinicalreport, treatment with the unilaterally designed obturator is discussed.
Discussion: The use of functional impression techniques during the trial denture stage registered theoptimal shape of the soft tissues while they were loaded under a variety of functional conditions. Thisacted to distribute the functional forces to the saddle area proportionally and prevented any leakageand seepage of food into the defect.
Conclusion: The unilaterally designed obturator prosthesis has served to restore masticatory functionas well as to obturate the maxillary defect.

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Patient: The patient had esthetically unacceptable maxillary anterior crowns. Provisional restorationsin consideration of the smile line were used for the maturation of periodontal tissues. Owing tofull regeneration of interdental papillae, small black triangles that existed in the gingival embrasuredisappeared six months after the luting of final restorations.
Discussion: We should not overlook the importance of physiological occlusion for the management ofhealthy periodontal tissues.
Conclusion: To creat a natural-looking esthetic prosthesis, the dentist should strive to creat an idealenvironment for the technician to fabricate functional and esthetic restorations.

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Patient: A fifty-two-year old female patient visited our dental hospital due to periodontal disease and aesthetic complaint by median diastema. A resin bonded retainer for the upper anterior teeth was placed after periodontal treatment and minor tooth movement. Median diastema and periodontal disease have not relapsed for these 6 years.
Discussion: Prosthetic treatment combined with minor tooth movement enabled the recovery of healthy periodontal tissue and reduction of the amount of tooth structure to be prepared. As a result, pulp treatment was not involved and desirable tooth contour was successfully achieved.
Conclusion: Prosthetic restoration by resin bonded retainer followed by periodontal treatment and minor tooth movement was useful to improve aesthetic problems and to recover and maintain healthy periodontal tissue in this case of a patient with periodontal disease and median diastema with deep bite.

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Patient: Implant treatment with sinus lift was conducted in a 53-year-old male patient who had bilateral edentulous posterior maxilla with a limited bone volume of the sinus floor. One year later, the mobility at the anterior teeth of the maxilla increased and then decreased due to occlusal adjustment. The left posterior teeth of the mandible were extracted due to severe periodontitis and two implants were placed.
Discussion: In this case, the patient was highly satisfied with the above treatment.When the eccentric movement is guided by natural teeth in implant oral rehabilitation, it is important for the long-term results to consider the change of the occlusal contact.
Conclusion: Implant treatment with bone augmentation is useful to obtain excellent clinical results in spite of the commensurate difficulties for the patient.

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Patient: A 60-year-old woman presented to the Clinic at Health Science University of Hokkaido on September, 1997. The patient's chief complaint was difficulty in chewing due to pain with tooth clenching of a fixed partial denture in the left mandible. This clinical report describes a treatment approach using implant-supported fixed prostheses by two dental implants after extraction of the abutment teeth.
Discussion: She tried to use the fabricated mandibular removable partial denture but disliked the lingual bar. After discussing a treatment plan using implant-supported fixed prostheses, a decision was made to place implants in the free-end partially edentulous mandible.
Conclusion: The patient was followed for 4 years with no surgical or prosthetic complications. It is suggested that a dental implant for prosthetic treatment may improve the quality of life of the patient.

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Patient: A 53-year-old female with root fracture of the second premolar in the right mandible underwent implant therapy. After extraction, the GBR (guided bone regeneration) technique was applied to the bone defect in June 2000. At 6 months after GBR, implants were placed in the augmented bone. The final prosthesis was restored in July 2001.
Discussion: The bone around the implants was evaluated by using X-ray CT images, before and after GBR, and three years after final restoration. The three images showed the same bone conditions around the implants.
Conclusion: It is important to evaluate bone condition around implants using X-ray CT. Bone defects can be augmented by the GBR technique, and the bone condition around the implants was stable after function.

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Patient: A 58 year-old female patient visited the clinic with chief complaint of chewing difficulty with her complete dentures. These dentures did not have a sufficient size of denture base and the resin teeth were completely ground down. Treatment dentures were inserted and the form was transferred to final dentures.
Discussion: The risk of re-treatment and adjustment after the denture insertion was reduced by using the treatment dentures. The Cochrane Library reported that there is no difference between complete dentures and implant supported over dentures in terms of patient satisfaction/chewing ability, provided the patient has an adequate mandibular ridge.
Conclusion: Treatment dentures are important to reduce the risk of re-treatment.

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