Taste-related sensations in old age.

The sense of taste is important as it allows for assessment of nutritional value, safety and quality of foods as well as for food enjoyment and quality of life. Several factors are suggested to be associated with taste sensitivity, and higher prevalence of taste disorder has been reported among older adults. This review focused on the reported causes and correlates of taste decline in older adults, with the aim to consolidating existing evidence and identifying gaps and limitations. Using a scoping review methodology, we sought relevant literature from the last 20 years. Search terms included taste, gustatory sense, older adults and geriatric. Considered research was limited to reports that involved research participants over 60 years old, papers written in English, and manuscripts published after 1995. We have consolidated available evidences on the influences on taste-related sensations among international cohorts of older adults. Influences can be reflected under the topics of physiological changes in the sensory organs, physiological and behavioural variables related to taste sensation. This review identified three areas of historic and current research endeavour related to studies of taste sensation in older subjects: physiological changes in the sensory organs, factors related to the ageing of the individual and behavioural variables affecting taste-related sensation. Key limitations and gaps in the current literature include notable lack of consideration of potential confounding, mediating and moderating effects, while future research is indicated in the areas of measuring the quality of health and life. As global population ageing accelerates in the coming decades, maintaining taste sensations and sensitivity in older adults will be a key measure to ensuring quality of health and life.

Dietary Intake Is Associated with Occlusal Force Rather Than Number of Teeth in 80-y-Old Japanese.

There has been a growing interest in the association between the number of teeth and dietary intake in older populations. However, people around the age of 80 y have frequently lost most of their teeth, and dental prostheses replacing the missing teeth play an important role in masticatory function. Therefore, masticatory function cannot be evaluated by the number of teeth alone. The occlusal force of the complete dental arches is an index of masticatory function, reflecting not only the number of teeth, but the effect of removable dentures. The purpose of this cross-sectional study was to determine the relative importance of the number of teeth and occlusal force in association with dietary intake in 80-y-old Japanese people. This study included 760 community-dwelling Japanese people aged 79 y to 81 y. The authors measured bilateral maximal occlusal force in the intercuspal position using pressure-sensitive sheets. Removable denture wearers kept their dentures in place during the measurements. Energy-adjusted food groups and nutrient intake during the preceding month were assessed by a brief self-administered diet history questionnaire. The authors assessed linear trends in food and nutrient intake in relation to the number of teeth and occlusal force after adjusting for gender and socioeconomic status (education level, financial status, family structure, resident area and BMI). P values of < 0.05 were considered to be statistically significant. The authors found that the number of teeth was not associated with the energy-adjusted intake of any food group examined. In contrast, a decline in occlusal force was significantly associated with a lower intake of vegetables, fish and shellfish, protein, polyunsaturated fatty acids, dietary fiber and most vitamins and minerals ( P for trend < 0.05). We conclude that food and nutrient intake was more closely associated with occlusal force than the number of teeth in community-dwelling Japanese people aged 79 y to 81 y. Knowledge Transfer Statement: This cross-sectional study of older Japanese people showed that, after controlling for considerable covariates, occlusal force rather than the number of teeth is positively associated with energy-adjusted intake of vegetables, fish and shellfish, protein, polyunsaturated fatty acids, dietary fiber and most of vitamins and minerals. This means that reduced occlusal force may unconsciously lead older people toward a habitual unhealthy dietary intake. Older people have frequently lost most of their teeth and require prosthetics to restore masticatory function. Bilateral occlusal force is therefore a better measure of masticatory function than the number of remaining teeth. Our findings suggest that prosthetic rehabilitation is a significant factor in the prevention and management of chronic diseases and frailty through better dietary intake in older populations.

Longitudinal study of factors affecting taste sense decline in old-old individuals.

The sense of taste plays a pivotal role for personal assessment of the nutritional value, safety and quality of foods. Although it is commonly recognised that taste sensitivity decreases with age, alterations in that sensitivity over time in an old-old population have not been previously reported. Furthermore, no known studies utilised comprehensive variables regarding taste changes and related factors for assessments. Here, we report novel findings from a 3-year longitudinal study model aimed to elucidate taste sensitivity decline and its related factors in old-old individuals. We utilised 621 subjects aged 79-81 years who participated in the Septuagenarians, Octogenarians, Nonagenarians Investigation with Centenarians Study for baseline assessments performed in 2011 and 2012, and then conducted follow-up assessments 3 years later in 328 of those. Assessment of general health, an oral examination and determination of taste sensitivity were performed for each. We also evaluated cognitive function using Montreal Cognitive Assessment findings, then excluded from analysis those with a score lower than 20 in order to secure the validity and reliability of the subjects' answers. Contributing variables were selected using univariate analysis, then analysed with multivariate logistic regression analysis. We found that males showed significantly greater declines in taste sensitivity for sweet and sour tastes than females. Additionally, subjects with lower cognitive scores showed a significantly greater taste decrease for salty in multivariate analysis. In conclusion, our longitudinal study revealed that gender and cognitive status are major factors affecting taste sensitivity in geriatric individuals.

Factors related to taste sensitivity in elderly: cross-sectional findings from SONIC study.

The sense of taste is important, as it allows for assessment of nutritional value, as well as safety and quality of foods, with several factors suggested to be associated with taste sensitivity. However, comprehensive variables regarding taste and related factors have not been utilised in previous studies for assessments of sensitivity. In the present study, we performed cross-sectional analyses of taste sensitivity and related factors in geriatric individuals who participated in the SONIC Study. We analysed 2 groups divided by age, 69-71 years (young-old, n = 687) and 79-81 years (old-old, n = 621), and performed a general health assessment, an oral examination and determination of taste sensitivity. Contributing variables were selected by univariate analysis and then subjected to multivariate logistic regression analysis. In both groups, females showed significantly better sensitivity for bitter and sour tastes. Additionally, higher cognitive scores for subjects with a fine taste for salty were commonly seen in both groups, while smoking, drinking, hypertension, number of teeth, stimulated salivary flow salt intake and years of education were also shown to be associated with taste sensitivity. We found gender and cognitive status to be major factors affecting taste sensitivity in geriatric individuals.

Taste detection ability of elderly nursing home residents.

Due to the rapid rise of aged populations throughout the world, it is essential to elucidate the cause of taste dysfunction, because it may reduce appetite, leading to inadequate dietary intake. We aimed to compare taste detection ability between dependently and independently living geriatric individuals of nearly the same age with oral status. Forty-three elderly individuals considered to be cognitively eligible and residing in nursing homes in Japan were enrolled (n = 43, 82·3 ± 8·5 years) and were compared with an independently living elderly group (n = 949, 79·9 ± 0·8 years), aiming to compare taste detection ability between dependently and independently living elders of nearly the same age. Information regarding comorbidity and medication was obtained as general health status, and oral status including number of present teeth, denture usage and maximal occlusal force was also noted. In the dependently living group, 69·4%, 14·3%, 16·3% and 8·2% of participants could detect sweet, sour, salty and bitter tastes, respectively, which was significantly lower than the independently living group for each taste (97·9%, 70·8%, 89·6% and 43·8% for sweet, sour, salty and bitter tastes, respectively). The multivariate logistic regression analysis revealed that residing in nursing homes was associated with reduced sensitivity for four different tastes. The diseases and the situation of dependent elders were more likely the cause of the decreased taste sensitivity.

Association of Occlusal Force with Cognition in Independent Older Japanese People.

Recent longitudinal studies have shown the influence of multiple tooth loss on cognitive impairment, and earlier studies suggested that periodontal disease was related to cognitive decline. Tooth loss is associated with reduced masticatory function, which may affect stimulation of the central nervous system and dietary intake. Although some studies have reported a relationship between chewing ability and cognitive function, no studies have examined this area in terms of objective oral function. The aim of this study was to examine the association of occlusal force with cognitive decline in the preclinical stage among older people with higher-level functional capacity. This cross-sectional study for community-dwelling older people living in urban and rural areas in Japan examined 994 persons in the 70-y group (age range, 69-71 y) and 968 persons in the 80-y group (age range, 79-81 y). Retention of higher-level competence was defined according to the Tokyo Metropolitan Institute of Gerontology Index of Competence. Cognitive function was measured with the Japanese version of the Montreal Cognitive Assessment (MoCA-J). Oral status and function were assessed by the number of remaining teeth, periodontal pocket depth, and maximal occlusal force. Associations between the MoCA-J score and occlusal force were examined by bivariate and multivariate analysis. Approximately one-half of the participants retained higher-level functional capacity and were included in the analysis. Multiple regression analysis showed that occlusal force was significantly related to cognitive function after controlling for possible predictors including age, sex, socioeconomic status, medical condition, and handgrip strength. The number of remaining teeth and periodontal pocket depth were not significantly associated with cognitive function. Among community-dwelling older people with retained competence, maximal occlusal force was positively associated with their cognitive function. These results suggest that oral function might be a predictor for preclinical cognitive decline. Knowledge Transfer Statement: Multiple regression analysis showed that occlusal force was significantly related to cognition after controlling for possible predictors including handgrip strength as an indicator of general muscle strength, suggesting the independence of oral function. The number of remaining teeth did not have this association. The majority of older people have lost teeth and have received prosthodontic treatment, and their occlusal force is determined not only by the number of remaining teeth but also by prosthetic rehabilitation. These results can be used by clinicians focusing on prevention of tooth loss among the entire population, as well as to encourage partially edentulous and fully edentulous patients to restore their oral function with prostheses in order to eliminate a possible risk factor for cognitive impairment.

A field survey of the partially edentate elderly: Investigation of factors related to the usage rate of removable partial dentures.

Although the shortened dental arch (SDA) concept has been known to all over the world, acceptance of the SDA concept as an oral health standard can be questionable from the patients' point of view, even if it is biologically reasonable. Furthermore, because the health insurance system covers removable partial dentures (RPDs) for all citizens in Japan, SDA patients seem to prefer to receive prosthetic treatment to replace the missing teeth. However, there were few field surveys to investigate the usage rate of RPDs in Japan. The purpose of this study was to determine the usage rate of RPDs in older Japanese subjects and to investigate the factors related to the usage of RPDs. Partially edentate participants (n = 390) were included in this study. Oral examinations were conducted to record several indices. The Cochran-Armitage trend test was used to evaluate the relationship between the number of missing teeth and the usage rate of RPDs. Chi-squared tests and logistic regression analysis were conducted to evaluate the factors related to the usage rate of RPDs. Usage of RPDs had a significantly positive association with the number of missing distal extension teeth and bilaterally missing teeth. The usage rate of RPDs increased as the number of missing distal extension teeth increased (P for trend < 0·001). The conclusion of this study was that participants with missing distal extension teeth had higher usage rates of RPDs than other participants, and the usage rate increased as the number of missing distal extension teeth increased.

The Impact of the Crown-Root Ratio on Survival of Abutment Teeth for Dentures.

Crown-root ratio (CRR) is commonly recorded when planning prosthodontic procedures. However, there is a lack of longitudinal clinical data evaluating the association between CRR and tooth survival. The aim of this longitudinal practice-based study was to assess the impact of CRR on the survival of abutment teeth for removable partial dentures (RPDs). Data were collected from 147 patients provided with RPDs at a dental hospital in Japan. In total, 236 clasp-retained RPDs and 856 abutment teeth were analyzed. Survival of abutment teeth was assessed using Kaplan-Meier methods and Cox's proportional hazard (PH) regression. The Cox PH regression was used to assess the prognostic significance of initial CRR value with adjustments for clinically relevant factors, including age, sex, frequency of periodontal maintenance programs, occlusal support area, type of abutment tooth, status of endodontic treatment, and probing pocket depth. Abutment teeth were divided into 1 of 5 risk groups according to CRR: A (≤0.75), B (0.76-1.00), C (1.01-1.25), D (1.26-1.50) and E (≥1.51). The 7-year survival rate was 89.1% for group A, 85.9% for group B, 86.5% for group C, 76.9% for group D, and 46.7% for group E. The survival curves of groups A, B, and C were illustrated to be quite similar and favorable. The multivariable analysis treating CRR as a continuous variable allowed estimation of the hazard ratio at any specific CRR value. When CRR = 0.80 was set as a reference, the estimated hazard ratio was 0.58 for CRR = 0.50 (95% confidence interval [CI], 0.36-0.91), 1.13 for CRR = 1.00 (95% CI, 0.93-1.37), 1.35 for CRR = 1.25 (95% CI, 1.02-1.80), 1.53 for CRR = 1.50 (95% CI, 1.15-2.08), or 1.95 for CRR = 2.00 (95% CI, 1.44-2.65). These practice-based longitudinal data provide information to improve the evidence-based prognosis of teeth in providing prosthodontic procedures.

Influence of genetic and environmental factors on oral diseases and function in aged twins.

This study was conducted to quantify the genetic and environmental contributions to oral disease and function in twins. Participants were middle-aged and old twins, 116 monozygotic and 16 dizygotic pairs whose mean age was 66·1 ± 10·3 (SD) years. Number of teeth, percentage of decayed, filled and missing teeth and periodontal status were recorded as indicators of oral disease. The widths of upper and lower dental arch served as indicators of morphological figures. Furthermore, stimulated salivary flow rate, occlusal force and masticatory performance were measured as indicators of oral function. Univariate genetic analysis with monozygotic and dizygotic twin pairs was conducted to detect the fittest structural equation model of each outcome. Both number of teeth and periodontal status fitted the model composed of common environmental factor and unique environmental factor. Decayed, filled and missing teeth, morphological figures and measurements of oral function fitted the model composed of additive genetic factor and unique environmental factor. The model fitting of each measurement suggested that periodontal disease was mainly affected by environmental factors, while morphological figures and oral functions were influenced by both genetic and environmental factors.

Association of periodontal status with occlusal force and food acceptability in 70-year-old adults: from SONIC Study.

This cross-sectional study aimed to investigate the association of periodontal status with occlusal force and food acceptability. We hypothesised that mastication deteriorated with reduced periodontal support, even when posterior occlusal contacts with natural teeth were maintained and the patients remained clinically asymptomatic. Participants were 482 independently living 69-71-year-olds, classified as Eichner's group A, having no mobile teeth and no periodontal symptoms. The periodontal probing depth (PPD) and restoration status of each tooth were examined. Occlusal force in the intercuspal position was measured with pressure-sensitive films. Food acceptability was evaluated from the difficulty experienced in chewing apples, grilled beef, and hard rice crackers. Multivariate regression analysis was performed to investigate the association of periodontal status with occlusal force and food acceptability. A P-value of <0.05 was considered statistically significant. Multiple linear regression analysis showed that occlusal force had significant negative associations with maximal PPD (standardised partial regression coefficient (ß) = -0.121) after controlling for gender, handgrip strength, number of teeth, and percentage of restored teeth. Approximately 15% of participants were included in the compromised food acceptability group. Logistic regression analyses showed that compromised food acceptability was significantly associated with PPD, after controlling for gender, number of teeth, and percentage of restored teeth. Periodontal probing depth (PPD) was significantly correlated with occlusal force and self-rated food acceptability after controlling for the possible confounding factors in septuagenarians, even those with complete posterior occlusal contacts and no tooth mobility.

Mouthguard and sports drinks on tooth surface pH.

The influence of sports drinks and mouthguards on the pH level of tooth surface was examined. A custom-made mouthguard was fabricated for each subject. The pH level was measured by electric pH meter with sensitivity of 0.01 up to 30 min. Sports drinks (pH=3.75) containing 9.4% sugar were used in this study. Measurements were performed on a cohort of 23 female subjects without a mouthguard (control), wearing a mouthguard only (MG), wearing a mouthguard after 30 ml sports drink intake (SD+MG), wearing a mouthguard during a 5-min jogging exercise (MG+EX) and wearing a mouthguard during jogging after sports drink intake (SD+MG+EX). For 7 male subjects, the same measurements were performed while a sports drink was taken over the mouthguard (MG+SD, MD+EX+SD). MG showed statistically higher pH level than control (p<0.05). SD+MG exhibited a significant decrease in pH level, and SD+MG+EX exhibited even below the critical level of pH 5.5 in some subjects. When sports drinks were taken over the mouthguard, no significant differences in pH level were observed among the different conditions.Within the limitations of this study, it was suggested that wearing a mouthguard during exercise is in itself not a possible risk factor for dental caries, while wearing a mouthguard after consuming sports drinks is.

Determinants of change in oral health-related quality of life over 7 years among older Japanese.

Because there are more elderly people than ever before and because they are living for longer periods of time, it is essential to understand the determinants of healthy ageing. This study examined changes in oral health-related quality of life (OHRQoL) among Japanese elderly over a 7-year period. A sample of independently living individuals (aged 60+ years) underwent a questionnaire and dental examination at baseline and 7 years afterwards. The Geriatric Oral Health Assessment Index (GOHAI) was used to assess the impact of oral conditions. Occlusal force and salivary flow were also assessed. Of the 411 participants assessed at baseline, 130 (31·6%) accepted to participate after 7 years. There were no significant differences between those lost to follow-up and those assessed at 7 years, except that a higher proportion of the latter rated their baseline general health as good. Among the latter, the overall mean GOHAI score did not change significantly (11·8 at baseline and 11·1 at follow-up; P = 0·16). However, after controlling for age, gender and baseline GOHAI score, participants who had lost teeth or experienced a decline in occlusal force after 7 years had higher follow-up GOHAI scores (indicating poorer OHRQoL). Unfavourable changes in clinical oral status over time are reflected in poorer self-rated oral health.

Influence of hypertension on pH of saliva in older adults.

BACKGROUND: Hypertension and/or antihypertensive medication reportedly induce dry mouth; however, an immediate relationship between salivary flow and hypertension has not been elucidated. OBJECTIVES: The purpose of the present study was to examine the association of hypertension and antihypertensive medication with salivary flow rate and pH in older adults. SUBJECTS: Subjects were independently living volunteers aged 60-78 years taking no medication (n = 138) or only antihypertensive medication (n = 27). Unstimulated saliva and stimulated saliva by the mastication method were collected, and salivary pH was measured. Hypertension was defined as systolic blood pressure of ≥ 140 mmHg and/or diastolic blood pressure of ≥ 90 mmHg. RESULTS: There was no significant correlation between either hypertension or intake of antihypertensive medication and unstimulated or stimulated salivary flow rate. However, multiple regression analysis showed that hypertension was significantly associated with pH of unstimulated saliva after controlling for other variables (ß = -0.270, P = 0.003). CONCLUSION: Hypertension regardless of antihypertensive medication was related to a lower pH of unstimulated saliva. Blood pressure might be a required consideration for maintenance of oral health in older individuals.

Subjective values of different treatments for missing molars in older Japanese.

The purpose of this study was to determine how elderly Japanese people subjectively value treatment options for missing molars. Subjects were 528 independently community-dwelling elderly people. They were presented with photographs and descriptions of the process and expected outcomes of five possible treatment options: cantilever fixed dental prosthesis (FDP); resin or metal removable partial denture prosthesis (RPDP); implant-supported fixed prosthesis; and no replacement (shortened dental arch: SDA) for missing lower bilateral first and second molars. The participants filled in the questionnaire on subjective importance for treatment and indicated on a visual analogue scale how they valued the treatment (utility value: UV). Values were analysed by Mann-Whitney U-tests and multiple logistic regression analyses. Overall, the UVs for the FDP and the metal RPDP were the highest, and the UV for the SDA was the lowest. With respect to subjective importance, 'chewing ability' and 'no pain during function' were significantly selected more frequently. Multiple logistic regression analyses showed that the UV for the resin RPDP had significant positive associations with denture wearers and low treatment cost, whereas the implant had significant negative associations with denture wearers and older age. The SDA had significant positive associations with men and low treatment cost and a negative association with appearance. In conclusion, these elderly Japanese preferred cantilever FDPs and metal RPDPs to implants and 'no replacement.' It suggests that the SDA as an oral health goal can be questionable from the patients' point of view, even if it is biologically correct.

Prevalence of torus palatinus among a group of Japanese elderly.

The purpose of this study was to examine the prevalence of torus palatinus (TP) among Japanese elderly and to identify the factors associated with the formation of TP. The subjects were adults aged over 60, who lived independently in the community and attended lectures once a week at the Senior Citizens' College in Osaka prefecture during 2007 and 2008. A total of 664 subjects, including 294 men and 370 women, were examined, and the mean age was 66·5±4·2 (s.d.). After informed consent was obtained, participants responded to a questionnaire and underwent clinical examination consisting of dental status, temporomandibular symptoms and occlusal force. There were 113 (17·0%) subjects with TP. The prevalence of TP was more frequent in women than in men (24·6% versus 7·5%, P<0·01). Moreover, there was a significant relationship between the presence of TP and the presence of Torus mandibularis (13·3% versus 25·9%). There was no significant relationship between the prevalence of TP and other factors; diurnal and nocturnal bruxism, occlusal force, occlusal support and temporomandibular diseases symptom. Logistic regression analysis, in which adjustment was made for age and occlusal force, revealed a significant relationship between the presence of TP and gender and the presence of torus mandibularis (TM) (P<0·001 OR=3·43, 95%CI=2·00-5·86; P<0·001, OR=2·63, 95%CI=1·64-4·24, respectively). This study suggests that genetic factors play a more significant role than factors related oromaxillofacial function in the aetiology of TP.

Measuring masticatory performance using a new device and ß-carotene in test gummy jelly.

Objective methods for evaluating masticatory performance are invaluable for quantitative comparisons between various dental treatments as well as diagnosing masticatory disorder. The purpose of this study was to develop an accurate method for automatically measuring masticatory performance using a new measuring device consisting of light-emitting diodes and a photodiode and test gummy jelly. First, the relationship between six known ß-carotene concentrations in aqueous solution and the voltage values exhibited on a photodiode was investigated. Mean voltage obtained by red light incident on the photodiode indicated a significantly high correlation (r=0·999 in a cubic function, P<0·01) with ß-carotene concentration in the aqueous solution. Second, to establish the optimal measuring conditions for evaluating masticatory performance, factors influencing mean voltage were investigated, such as water temperature and times for rinsing the gummy jelly and dissolving ß-carotene from the jelly. A stable mean voltage was obtained by measuring under the following conditions: rinsing water temperature, 35°C; rinsing time, 30s; water dissolving temperature, 35°C; dissolving time, 10s. Finally, the relationship between seven surface area values of divided gummy jelly and ß-carotene concentrations dissolved from the divided jellies was investigated. The increase in surface area of divided test gummy jelly particles was accurately calculated (r=0·992, P<0·001) from mean voltage on the photodiode to change with ß-carotene concentration dissolved from the jelly surface. This new method using test gummy jelly and an automatic measuring device appears useful for precisely evaluating masticatory performance.

Patterns of missing occlusal units and oral health-related quality of life in SDA patients.

The aim of this study was to explore the relationship between patterns of missing occlusal units (OUs) and oral health-related quality of life (OHRQoL) in subjects with the shortened dental arches (SDAs). Subjects with SDAs were recruited consecutively for 1 month from six university-based prosthodontic clinics. In total, 115 SDA subjects participated (mean age, 58.5 +/- 10.0 years; 71% female). The location and number of missing teeth were examined and the number of missing OUs was calculated. To evaluate OHRQoL, the Japanese version of the Oral Health Impact Profile (OHIP-J) was administered and the summary score of OHIP-J was calculated. The SDA subjects were categorized depending upon the anterior-posterior lengths of the missing or remaining OUs. Regression analyses were performed to investigate the OHIP-J differences between groups of subjects with various anterior-posterior SDA lengths. The analyses revealed that subjects who only lost the second molar contact exhibited significantly better OHRQoL than those who lost more teeth [coefficient: 11.1, 95% confidence interval (CI): 2.8-19.2, P = 0.02]. Furthermore a statistically significant group difference was observed between the groups with and without the first molar occlusal contact (coefficient: 12.8, 95% CI: 1.4 to 24.1, P = 0.03). In conclusion, although our results are of exploratory nature and need validation, patterns of missing OUs are likely to be related to the OHRQoL impairment in SDA subjects with the presence of first molar contact having a particularly important role.

Association of symptomless TMJ sounds with occlusal force and masticatory performance in older adults.

This study investigated associations between temporomandibular joint (TMJ) sounds and occlusal force or masticatory performance stratified by posterior occlusal supports in older Japanese adults. The subjects consisted of 1646 independently living people over 60 years. Masticatory performance, occlusal force, TMJ sounds and maximal mouth opening were examined. Posterior occlusal supports were classified by the Eichner Index. The prevalence of TMJ sounds was 27.7%, limitation of mouth opening (< 40 mm) was 7.9% and TMJ pain was only 1.5%. In the Eichner C group, TMJ sounds were significantly associated with lower occlusal force (OR = 3.20, P = 0.046) and lower masticatory performance (OR = 3.18, P = 0.041) after controlling for gender and age. These associations were not found in the Eichner A and B groups. Within the limitations of this study, the presence of TMJ sounds, even if they were symptomless, was associated with impairment of masticatory function in older adults with reduced occlusal support.

Effect of reinforcement on overdenture strain.

Because the abutment becomes the fulcrum, and the denture base over the coping is usually thin, the overdenture is susceptible to fracture. We hypothesized that rational reinforcement can reduce strain and prevent deformation and fracture of the overdenture. We investigated the effect of reinforcement on overdenture strain around the copings and at a midline. A mandibular edentulous model with a 2-mm-thick artificial mucosa and abutment teeth installed bilaterally in the canine position was produced. The coping had a dome-shaped upper surface with a height of 6 mm. On the lingual polished surface, strain gauges were attached at the canine position and at the midline. A vertical load of 49 N was applied on the occlusal surface. Among several kinds of reinforcements, the cast metal reinforcement that covers both the midline and the coping top significantly reduced the strain on the overdenture. It is suggested that this simple reinforcement is effective in preventing deformation and fracture of the overdenture.

Factors associated with taste dissatisfaction in the elderly.

The purpose of this study was to investigate taste sensation in the elderly, and to determine relationships between subjective dissatisfaction with taste ability and factors such as age, gender and oral status among independently living elderly individuals. Participants were older adults (mean age, 66.0 +/- 4.2 years; 321 men and 319 women) voluntarily attending a Senior Citizen Educational Program supported by local government in 2003 and 2004. The questionnaire included self-assessed items on general health, dry mouth, chewing satisfaction and taste satisfaction. Respondents underwent investigation of salivary flow rate, dental status and gustatory testing using the filter-paper disc method for sweet, salty, sour and bitter. Chi-squared tests showed that the factors associated with dissatisfaction with taste ability were older age, dissatisfaction with chewing, dry mouth during eating and wearing dentures covering the entire hard palate. The sensation for each taste was not significantly related to taste satisfaction by chi-squared test. Multiple logistic regression analysis showed that dry mouth during eating, dentures covering the entire hard palate, dissatisfaction with chewing and discriminatory threshold for the sour taste were associated with dissatisfaction with taste ability. We found a significant association between subjective taste dissatisfaction and certain oral factors; hence, when patients complain about diminished taste, dentists must assess oral status as well as taste sensation.