It is well-accepted that dental treatment and care can promote oral health-related quality of life (QOL) in general. However, there is still not enough evidence that dental care can improve general healthrelated QOL. Recently, some clinical evidence and basic science data are starting to support the view that dental medicine, e. g., oral functional rehabilitation and control of chronic subclinical inflammation in the periodontal tissues, can promote general health, especially of the aged population. These evidences can be summarized and subcategorized into the following three concepts: 1) oral care lowers the risk of pneumonia in institutionalized elderly, 2) appropriate periodontal treatment reduces the risk of developing and worsening metabolic syndrome, containing type 2 diabetes and coronary heart disease, 3) appropriate oral functional rehabilitation with conventional prosthodontic treatments can improve physiological and immunological activity in elderly persons. The recognition of these contributions of dental medicine has resulted in two new movements: 1) an intensive campaign to prevent dental caries and periodontal disease in order to keep original teeth intact throughout life (8020 movement), and 2) a paradigm shift in dental clinical decision-making to contribute toward keeping and improving general health by oral infection control and oral functional rehabilitation (Japan Health Promotion in the 21^st century). This article reviews the relationship between dental medicine and general health and discusses the future direction of prosthodontics to contribute to general health amid rapid population aging in Japan.

View full abstract

Purpose: Recently, much attention has been paid to the involvement of sub-clinical inflammation in the pathogenesis of coronary heart disease as well as type 2 diabetes. Chronic periodontitis is one such sub-clinical inflammation. The close relationship between periodontal inflammation and type 2 diabetes as well as coronary heart disease is summarized.
Study selection: The relations were discussed based on two studies, one on the effect of periodontal treatment on the metabolic control of diabetes, the other on the association between the degree of periodontal disease and carotid atherosclerosis.
Results: Periodontal treatment appeared to have a beneficial effect on the metabolic control of diabetes. Additionally, periodontal disease seemed to be associated with carotid atherosclerosis.
Conclusions: Appropriate periodontal treatment reduces the risk of developing and worsening metabolic syndrome. Thus, it is important to establish effective treatment strategies based on the evidence accumulated so far.

View full abstract

An association between mortality and dental status has been reported in several studies. These studies indicate that subjects with adequate dental status, defined as at least 16 teeth or at least 20 teeth, have a lower relative risk of mortality compared with those with fewer teeth or denture users. However, there is an obvious important confounding socio-economic factor. It may be impossible to demonstrate definitively whether the risk of death is directly related to tooth loss or whether such a risk is an indirect outcome of common underlying factors such as lifestyle. A more important issue for 21 st century dentistry, however, is whether dental treatment can decrease the risk of mortality among elderly people. While more elderly persons are retaining their own teeth, tooth loss remains a serious problem faced by the elderly in developed countries. To evaluate the influence of dental occlusion, with or without the use of dentures, on mortality in community-dwelling elderly persons, we conducted an 8-year cohort study at Kure city in Japan. 1, 030 randomly selected healthy independent elderly aged 65 or over took part in this study. Subjects were classified into three groups according to the presence or absence of maxillo-mandibular tooth contacts. Subjects with no maxillomandibular tooth contacts were further subdivided into those with and without dentures. Data on mortality were obtained from Kure City Council in September 2003. Cox regression models were used in analyzing the risk of death with gender and age as covariates. The results showed individuals whose teeth had contact in at least the bilateral premolar regions at baseline had 0.78 times (95% CI: 0.60-0.99) lower risk of death during the succeeding 8 years than those who had no occlusion. Among those who had no occlusion with their own teeth, the risk of mortality among denture non-users was 1.52 times (95% CI: 1.25-1.83) higher than the risk of denture users. These results support the view that, in the elderly, poor dental occlusion is associated with an increased risk of mortality and that the use of dentures is associated with a decreased risk of mortality.

View full abstract

With dental practice for the elderly, we have been working to identify a relationship between oral functions/environments and general conditions.As a result, we have recognized the important role of dental treatment for the elderly in aging society.Taking food by mouth may influence life maintenance and life-style as well as the cause of death.In the elderly, who are more likely to have reduced oral functions, oral maintenance may influence their health and general conditions.However, scientific and subjective studies have just been started.An EBM approach is needed in order to scientifically prove the relationship between oral and general conditions and evaluation criteria are required. Accumulation of evidence-based data, which is directly beneficial to patients, may provide vocational and technical education as well as lead to the preparation of educational guidelines and clinical path. In addition, such data would assist evaluating and standardizing medical behaviors, which would result in ensuring medical quality and providing good medical treatment. From these points of view, the present study focused on the significance of dental treatment. In the study, evaluation criteria of oral conditions in the aged were prepared to identify the relationship between masticatory function and general conditions in the elderly with various oral conditions.

View full abstract

Patient: The patient was a 58-year old female suffering from broken all-ceramic crown on the lower right 1st molar.The patient was treated using a new Procera^® AllCeram Crown restoration.The clinical and technical procedures were carried out according to the manufacturer's recommendations. Although the esthetic and functional properties were excellent, adaptability to the abutment was not accurate.Therefore, we evaluated the suitability of Procera^® AllCeram Crown for the abutment in question.
Results and Discussion: 1. When the Procera^® AllCeram Crown was tried on the abutment, it was found that there was a 100μm space between the crown and the abutment. 2. Because of this space the crown was slightly loose. 3. The fit of the crown was not as good as that of a full cast crown. 4. Because of this space, it may be necessary to apply some devices to seat the crown on the abutment during a try-in and an occlusal equilibration or dies during the technical procedure.
Conclusions: By using the new Procera^® AllCeram Crown an esthetic restoration may be manufactured on the posterior tooth area without any reservations at this stage. Reducing the cement space from 100μm to 50μm will improve the clinical and technical results.

View full abstract

Patient: A 63-year-old woman who had complaints with maxillary and mandibular complete dentures resulting in masticatory deficiency was referred to our hospital in March 2002.The patient was classified as class IV with the American College of Prosthodontists' classification system. The existing dentures were marked as 30/100 with the assessment system of Sato et al. The horizontal jaw relation was extremely unstable with various tapping points. The patient was under the impression that her oral condition was the major cause of dissatisfaction with her dentures. The condition was diagnosed as masticatory deficiency caused by unstable jaw relation and denture maladjustment. A prosthetic and psychosomatic approach was planned, i. e. treatment dentures, remedy for unsuitable horizontal jaw relation, and receptive dialogue and attention to be a hearer, and remedy for denture maladjustment.Nineteen control adjustments were counted from the first visit and the final dentures were delivered in April 2003.Two months after the delivery, the patient became positive toward taking meals and significant improvement was observed in the patient's subjective assessment of aftermeal impressions.
Discussion: Long-term instability of horizontal mandibular position caused by inadequate dentures had induced self-hatred of a punctual and honest patient who was convinced that her oral condition was the reason for denture maladjustment. Appropriate prosthetic therapy and receptive correspondence and assurance resulted in remission of the symptoms.
Conclusion: In addition to appropriate prosthetic and psychosomatic therapy approach, the effectiveness of post-meal impression for assessing improvement of symptoms was shown to be important.

View full abstract

Purpose: Various prosthetic dentistry treatments are indispensable for patients who have a malfunction of mastication. In these circumstances, the objective assessment of mastication is very important for not only evaluating the treatment but also selecting diagnosis and treatment. The purpose of the current study is to design a simple assessment of mastication with colored gummy jelly, and to investigate the effectiveness of this method in comparison with Manly's sieving method and to discuss the development of this method (such as the possibility of visual assessment).
Methods: Thirteen subjects who had no malfunction of mastication chewed the colored gummy jelly and the absorbance of the residual coloring matter after mastication was measured to assess their mastication in comparison with Manly's sieving method. Moreover, the absorbance of 5 gradations of color in test colored aqueous solutions was presumed with 9 gradations of color samples that were made as guidelines.
Results: The higher the masticatory count was, the larger the values of mastication in both the sieving method and colored gummy jelly method were. The rate of increase decreased according to the increase of masticatory count in the sieving method, while the value of mastication in the colored gummy jelly method was proportional to the masticatory count. The value of mastication in the sieving method was proportional to the logarithm of absorbance. Regarding visual assessment, error and deviation were small when the absorbance of colored aqueous solution was less than 0.5.
Conclusions: The value of mastication in the sieving method was proportional to the logarithm of absorbance. The colored gummy jelly method was as effective as Manly's sieving method when the masticatory count was less than 20 times. Moreover, it is supposed that masticatory efficiency can be determined by using this assessment.

View full abstract

Purpose: This study investigated the effects of the removal direction of the impression on the accuracy of working casts for implants with the transfer system.
Methods: A master model was fabricated from a single standing ITI implant with a solid abutment. Working casts were fabricated using two methods, the conventional method and the transfer system with an impression cap and a shoulder analog. The impression was removed at 0°, 10° and 15° toward the long axis of a master model. An improved dental stone was poured into the impression. The master model and the working casts were measured with a profile projector and distortions were analyzed with 2-way ANOVA.
Results: Removal direction of the impression significantly influenced the height of the implant die and the upper position of the abutment, but did not influence other characteristics. The height of the implant die and the upper distortion of the upper position of the abutment decreased with an increase of the removal angle. The method of fabricating the model significantly affected the widths of the head and shoulder, the height of the implant die and the shoulder position. The widths of the head and shoulder, and the height of the implant die with the transfer method were significantly narrower and greater than those with the conventional method, respectively. The shoulder position with the conventional method distorted upwards; however, that with the transfer method distorted downwards. The interactions between the removal angle and the fabrication method were not significant.
Conclusions: When the removal angle of the impression was less than 15°, the accuracy of the working cast with the transfer system was acceptable for clinical use.

View full abstract

Purpose: This study was designed in order to apply maximal clenching force for the evaluation of prosthodontic treatments.The study examined the relationship between maximal clenching force and masseter muscle thickness in removable denture wearers who had lost many teeth.
Methods: Twenty-four denture wearers (age 52-85 yrs) were divided into two groups, a partial denture group (RPD group, n=12) and a complete denture group (CD group, n=12) according to the presence of occlusal contacts in remaining teeth.Twelve normal dentates (23-30 yrs) also participated as a control group.Maximal clenching force was measured using the Dental Prescale System and thickness of masseter muscle during relaxation was measured by ultrasonography.The relationship between maximal clenching force and masseter muscle thickness was investigated by means of simple regression analysis, and the slope and intercept of regression lines were compared by ANCOVA among the three groups.
Results: Significant positive correlations were found between maximal clenching force andmuscle thickness in all groups (r=0.71-0.93).The slope did not significantly differ, but the intercept showed a significant difference among the three groups, and the biggest intercept was found in the control group, while the smallest was in the CD group.
Conclusions: This study suggested that it was possible to indicate the standard of maximal clenching force by measuring masseter muscle thickness, and maximal clenching force could be an effective parameter for the evaluation of prosthodontic treatments.

View full abstract

Purpose: Our goal was to determine the relationship between the masticatory ability and brain function by objectively evaluating the cognitive information processing from a comparison of groups with different maximum occlusal pressures.
Methods: The subjects were divided into groups by using a criterion of maximum occlusal pressure, which is one of the indices for masticatory ability.The oddball paradigm was used with a circle as a rare stimulus and a triangle and square as frequent stimuli.As the subjects performed the task of discriminating each figure, P 300 latency, P 300 amplitude, reaction time (RT), and reaction time standard deviation (RTSD) were recorded.The variables were P 300 latency, P 300 amplitude, RT, RTSD, maximum occlusal pressure, and age.For each group, we performed principal component analysis on these variables to reduce data dimensionality and examined aspects of information processing.
Results: 1. There was a significant difference between the high and low occlusal pressure groups when comparing their P 300 latency (Cz) values. 2. From the principal component analysis performed at each stage for both groups, the high occlusal pressure group yielded a cumulative contribution rate of 81.1% and the low occlusal pressure group 82.7% with data reduction into first through fourth principal components for both groups. 3. From the comparison between the high occlusal and low occlusal pressure groups, there was a difference in extraction tendency of the high occlusal pressure group's fourth principal component and the low occlusal pressure group's third and fourth principal components.
Conclusions: There were differences in the tendency of event-related potential extraction and principal component extraction based on the principal component analysis of the high and low occlusal pressure groups.These differences indicate the possibility that differences in masticatory ability affect cognitive information processing.

View full abstract

Purpose: This study evaluated the effect of reinforcing materials on the mechanical strength of acrylic resin denture base (polymethylmethacrylate; PMMA). Three reinforcing materials were embedded in the heat-cure acrylic resin: polyethylene fiber-PMMA composite, glass fiber-PMMA, and strengthener-PMMA hybrid composite. The flexural strength test and dye penetration test were applied to each reinforced specimen.
Methods: Rectangular test specimens were modified by incorporating additional reinforcing materials: untreated polyethylene fibers, glass fibers, and strengthener. The same size of acrylic specimen without any reinforcing material was selected as a control. The flexural strength test was executed with Auto Graph AG-5000 (Shimadzu) after storing the specimens in water at 37°C for two weeks. The dye penetration test of the specimens was evaluated by measuring with a Profile Projector PJ 311 (Mitutoyo) after storing them in a 3% aqueous solution of basic fuchsin dye for 72 hours.
Results and Conclusions: The results suggested that reinforcing materials enhanced the flexural strength of PMMA, while the use of additional fiber reinforcement made of polyethylene or glass fibers in the test specimens did not affect the flexural strength. The additional reinforcing materials of the test specimen did affect the flexural strength.

View full abstract

Purpose: Excessive stress in the dentin is thought to be a cause of root fracture. This study evaluatec the effect of a remaining coronal tooth structure and luting cement on the stress distributions in dentir of abutment teeth restored with a post-and-core.
Methods: Stress distributions in the dentin of maxillary central incisors restored with a post-and-core and a porcelain fused-to-metal crown were analyzed by the 3-dimensional finite element method. The studied factors were the existence of the coronal tooth structure remaining in the abutment tooth restored with post-and-core, and the properties of cement luting the post-and-core, i.e., the MMA resin cement and a cement whose Young's modulus was modified to be 1.00 MPa.
Results: On the model using the resin cement, both models of the abutment tooth with and without remaining coronal tooth structure showed buccolingually symmetric distributions of von Mises stress in their root. On the other hand, for the model using the modulus-modified cement the model without remaining coronal tooth structure showed a more asymmetric stress distribution than the model with remaining coronal tooth structure. Additionally, the resin cement layer luting the post-and-core to the abutment tooth without remaining coronal tooth structure showed more intensive tensile stress vertical to the cement-dentin interface than the one for the coronal tooth structure abutment tooth with remaining coronal tooth structure.
Conclusions: The data suggest that the remaining coronal tooth structure and the properties of the luting cement in the abutment tooth had some effects on the stress distributions in root dentin.

View full abstract

Patients: A sixty-one-year-old male patient with an acquired maxillary defect underwent maxil-lofacial rehabilitation. The interim obturator prosthesis was inserted at 5 weeks after the maxil-lectomy, and then the definitive obturator prosthesis was delivered at 8 months after the surgery.
Discussion: The treatment outcome of this patient was evaluated with objective functional tests and a questionnaire on subjective satisfaction. The results of assessments suggested that wearing the definitive obturator prosthesis improved the patient's speech and chewing abilities.
Conclusion: It is very important to evaluate the treatment outcome using objective functional assess-ments along with subjective ones the maxillofacial rehabilitation. Additionally, it is suggested that comprehensive medical service in cooperation with other specialists and co-medical staffs is necessary to improve the quality of life of the patient.

View full abstract