Factors Influencing the Localization of Mandibular Third Molars in Twins.

PURPOSE: The aim of the present study was to evaluate the genetic and environmental factors influencing the localization of mandibular third molars by analyzing the panoramic radiographs of twins. We examined the mandibular third molars of Japanese monozygotic (MZ) and dizygotic (DZ) twins recruited by the Osaka University Center for Twin Research. MATERIALS AND METHODS: The present study included 49 pairs (98 participants) of MZ twins and 11 pairs (22 participants) of DZ twins. Using panoramic radiography, we evaluated the degree of eruption of mandibular third molars according to the height of the alveolus bone and the third molar space/crown width ratio. Using co-twin control analysis and a generalized linear mixed model, we evaluated the effects of various factors, including gender, age, body height, number of teeth, length of the lower dental arch, existence of a second molar, bruxism, and previous orthodontic therapy. RESULTS: Body height, third molar space/crown width ratio, and length of the mandibular dental arch were related to the degree of mandibular third molar eruption and were strongly influenced by genetic factors rather than common or unique environmental factors. CONCLUSIONS: The degree of third molar eruption was more similar among MZ twins than among DZ twins; therefore, genetic factors can be expected to have more significant influence than will environmental factors. These results can help identify the trend of third molar eruption from a young age, allowing us to advise the early extraction of mandibular third molars for patients with a short stature, narrow retromolar space, or short mandibular dental arch. In addition, if the genes that influence the degree of eruption were identified, we would be better equipped to predict an individual's risk of impaction, and indications for extraction might change.

Association of handgrip strength with various oral functions in 82- to 84-year-old community-dwelling Japanese.

OBJECTIVE: The purpose of this study was to elucidate the associations between muscle strength and several oral functions in a large cohort of community-dwelling, 82- to 84-year-old community-dwelling Japanese people. BACKGROUND DATA DISCUSSING THE PRESENT STATUS OF THE FIELD: Several studies have examined the relationships between physical performance and oral functions. However, no studies have investigated the associations of muscle strength with various objectively evaluated oral functional parameters in a large cohort of very old adults. MATERIALS AND METHODS: This study included 809 community-dwelling Japanese people (407 men and 402 women) aged 82-84 years. The oral functions examined were the maximal occlusal force, masticatory performance, stimulated salivary flow rate, repetitive saliva-swallowing test (RSST) score, tongue pressure and mouth-opening distance. Handgrip strength was measured, and its correlations with oral functions were assessed. Multiple linear and logistic regression analyses were performed to investigate the relationships between oral functions and handgrip strength. RESULTS: Multivariate analysis revealed that handgrip strength was correlated with not only the maximal occlusal force, masticatory performance and tongue pressure but also the RSST score and mouth-opening distance after adjustment for sex, number of teeth, use of removable denture, periodontal condition, instrumental activities of daily living, body mass index. When we examine the elderly people whose handgrip strength is declining, we should predict that their various oral functions may be declining. CONCLUSION: Handgrip strength was related to various oral functions after adjustment for the number of teeth in this population of community-dwelling 82- to 84-year-old Japanese.

Association between salivary flow rate and depressive symptoms with adjustment for genetic and family environmental factors in Japanese twin study.

OBJECTIVES: The association between salivary flow rate (SFR) and depressive symptoms have been inconclusive. The present study aimed to investigate the association between SFR and depressive symptoms with and without adjustment for genetic and family environmental factors. MATERIALS AND METHODS: We conducted a cross-sectional study using twins and measured SFR and depressive symptoms as the outcome and explanatory variables, respectively. We also performed three-step regression analyses by first analysing the association between SFR and depressive symptoms without adjustment for genetic and family environmental factors (individual-level analyses). We then performed between-within analyses using monozygotic (MZ) and same-sex dizygotic (DZ) twin pairs, and finally using only MZ twin pairs. These between-within analyses estimated the coefficients adjusted for genetic and family environmental factors. Furthermore, differences in the associations between individual-level and between-within suggest confounding by genetic and family environmental factors. RESULTS: We conducted 448 twins aged ≥20 years. In individual-level analyses in males and between-within analyses using MZ and same-sex DZ male twin pairs, SFR associated with depressive symptoms. In between-within analyses using only MZ male twin pairs, SFR did not associate with depressive symptoms. In females, SFR did not associate with depressive symptoms in both individual-level and between-within analyses. CONCLUSIONS: The present study revealed that the association between SFR and depressive symptoms was affected by common genetic factors in males. CLINICAL RELEVANCE: Understanding this association between SFR and depressive symptoms with adjustment for genetic and family environmental factors could lead to an important consideration for the prevention and treatment of hyposalivation.

Investigation of oral opportunistic pathogens in independent living elderly Japanese.

OBJECTIVE: Pneumonia is reported to be associated with high morbidity in elderly and compromised individuals, with poor oral health demonstrated to be a significant risk factor for pneumonia. Several opportunistic pathogens, such as Streptococcus pneumoniae, Klebsiella pneumoniae, Escherichia coli and Staphylococcus aureus, have been detected in patients with pneumonia. We investigated the prevalence of opportunistic pathogens in the oral cavity of healthy independent living Japanese elderly subjects and analysed factors related to harbouring those pathogens. MATERIALS AND METHODS: We studied 265 subjects, each of whom received a dental examination, during which specimens were collected with a tongue swab and examined for the presence of 10 oral opportunistic pathogens using single or multiple selective media. Furthermore, the presence of occult blood in saliva was examined using test paper strips. RESULTS: Oral opportunistic pathogens were detected in 13.6% of the subjects. Those positive for occult blood in saliva had a significantly higher rate of harbouring the pathogens (p < 0.05). In addition, age was a significant factor for the presence of pathogenic microbes in the oral cavity (p = 0.033). CONCLUSION: Positive findings of occult blood in saliva and older age are suggested to be significant factors for harbouring opportunistic pathogens in the oral cavity.

Clinically acceptable restorations may be a hotbed for cariogenic microbes.

OBJECTIVE: The aim of this study was to investigate the cross-sectional association of dental restorations with salivary cariogenic pathogens among the elderly to establish effective parameters of caries risk for this population. MATERIALS AND METHODS: Stimulated whole saliva was collected from 289 community-dwelling older adults (66.2 ± 3.9 years old) who had 20 or more teeth. Salivary levels of three cariogenic bacteria (Streptococcus mutans, Streptococcus sobrinus and lactobacilli) were estimated using quantitative polymerase chain reaction (real-time PCR) method. RESULTS: The mean number of residual teeth was 26.4, and restored teeth with crowns, inlays and composite resin were 7.35, 3.88 and 0.68, respectively. The number of crowns correlated positively with salivary S. mutans, S. sobrinus and lactobacilli. Multiple linear regression analyses showed that the number of restored teeth with crowns was independently associated with salivary S. mutans, S. sobrinus and lactobacilli after controlling for age, gender, number of residual teeth and salivary flow rate. Salivary flow rate was independently associated with salivary S. mutans and lactobacilli. CONCLUSION: The number of crowns had an association with salivary levels of cariogenic bacteria, suggesting that this parameter may be a caries risk indicator for the elderly population.

Impact of occlusal force on decline in body mass index among older Japanese adults: Finding from the SONIC study.

OBJECTIVES: To determine any independent influence of occlusal force and of number of natural teeth on decline in body mass index (BMI) among older Japanese adults. DESIGN: Longitudinal study over a 3- to 6-year period. SETTING: Urban and rural area in Japan. PARTICIPANTS: Independently living Japanese adults aged 69-71 years and 79-81 years at baseline. This analysis excluded participants who were defined as underweight at baseline. MEASUREMENTS: Information was collected on age, gender, occlusal force, the number of teeth, BMI, socioeconomic factors, medical history, the number of daily prescription medications, cognitive function, depressive symptoms, hand grip strength, and physical function. Maximal occlusal force was measured with a pressure-sensitive sheet. Nutritional status was assessed using BMI, and participants with BMI <21.5 were defined as underweight. Then, they were divided into two groups: a "BMI declined" group who were defined as underweight at either 3- or 6-year follow-up survey, and a "BMI maintained" group who were not defined as underweight at both follow-up surveys. Logistic generalized estimating equation (GEE) models were used to assess the effect of occlusal force and the number of teeth at baseline on decline in BMI over 3 or 6 years, after adjusting for possible covariates associated with nutritional status. RESULTS: The final analysis included 704 participants. Eighty-six (12.2%) participants were classified into the BMI declined group. Logistic GEE models showed that the number of teeth was not significantly associated with decline in BMI. However, occlusal force was significantly associated with decline in BMI (odds ratio = 0.90, 95% confidence interval = 0.83-0.97) after adjusting for covariates. CONCLUSION: Participants with lower occlusal force were more likely to be in the BMI less than 21.5 kg/m2 . The findings suggest that to prevent decline in oral function is important to maintain nutritional status.

Relationship between oral stereognostic ability and dietary intake in older Japanese adults with complete dentures.

PURPOSE: Oral stereognostic ability (OSA) is a useful indicator of oral perception to recognize food characteristics during mastication. Previous studies have shown associations between dietary intake and oral health status, such as taste perception. However, the effect of oral sensory ability on dietary intake is unclear. The purpose of this study was to investigate the association between oral sensory ability and dietary intake in older Japanese complete denture wearers. METHODS: This cross-sectional study included 164 participants aged 69-71 or 79-81years old, wearing both maxillary and mandibular complete dentures. OSA test was used to evaluate oral tactile perception. Diet during the preceding month was assessed using a self-administered diet history questionnaire. Multivariable linear regression analysis was conducted to assess the association between OSA score and food and nutrient intake after adjusting for age, sex, socioeconomic factors, and occlusal force. RESULTS: The bivariate analysis showed that OSA score was significantly and positively correlated with intake of green and yellow vegetables and negatively correlated with intake of cereals among examined foods. OSA score was also positively correlated with intake of vitamins A, B2, and C and α-tocopherol (as a substitute for vitamin E) among examined nutrients. After adjusting for age, sex, socioeconomic factors, and occlusal force, OSA score remained significantly associated with intake of green and yellow vegetables and α-tocopherol. CONCLUSIONS: OSA was significantly associated with intake of green and yellow vegetables in older complete denture wearers.

Occlusal force is correlated with cognitive function directly as well as indirectly via food intake in community-dwelling older Japanese: From the SONIC study.

BACKGROUND: Growing evidence suggests that oral health may be an important factor associated with cognitive function in aged populations. However, many previous studies on this topic used insensitive oral indicators or did not include certain essential covariates. Thus, we examined the association between occlusal force and cognitive function in a large sample of older adults, controlling for dietary intake, vascular risk factors, inflammatory biomarkers, depression, and genetic factors. METHODS: In this cross-sectional study of older community-dwelling Japanese adults, we examined data collected from 994 persons aged 70 years and 968 persons aged 80 years. Cognitive function was measured using the Japanese version of the Montreal Cognitive Assessment (MoCA-J). Oral status and function were evaluated according to the number of remaining teeth, periodontal pocket depth, and maximal occlusal force. Associations between MoCA-J scores and occlusal force were investigated via bivariate and multivariate analyses. RESULTS: Education level, financial status, depression score, and intake of green and yellow vegetables, as well as number of teeth and occlusal force, were significantly correlated with MoCA-J scores in both age groups. Among individuals aged 80 years, CRP and periodontal status were weakly but significantly associated with MoCA-J score. After controlling for all significant variables via bivariate analyses, the correlation between maximal occlusal force and cognitive function persisted. A path analysis confirmed the hypothesis that cognitive function is associated with occlusal force directly as well as indirectly via food intake. CONCLUSIONS: After controlling for possible factors, maximal occlusal force was positively associated with cognitive function directly as well as indirectly through dietary intake.

Does case severity make a difference to clinical improvement following complete denture treatment?

PURPOSE: The aim of this study was to investigate the effect of case severity on clinical outcomes when fabricating new complete dentures. MATERIALS AND METHODS: Participants were separated into severe and moderate groups using the index of case difficulty for edentulous patients developed by the Japan Prosthodontic Society. Before and after treatment, self-assessed masticatory ability and oral health-related quality of life (OHRQoL) were examined, and the authors compared them according to case severity using the Mann-Whitney U test. To compare findings before and after treatment, the authors used the Wilcoxon signed rank test. RESULTS: In the severe group, both scores were significantly improved after treatment (P < .01). However, in the moderate group, there was no significant difference in self-assessed masticatory ability as measured by the food acceptance score before and after treatment (P = .11). Before treatment, OHRQoL as measured by the Oral Health Impact Profile score was significantly higher in the severe group than in the moderate group (P < .01). However, after treatment, there was no significant difference between the two groups (P = .92). CONCLUSIONS: The authors concluded that case severity makes a difference in the edentulous patient's OHRQoL and self-assessed masticatory ability during complete denture treatment. Evaluating case severity with the index before treatment is a useful tool for patients and clinicians to predict clinical outcomes.

Examination of the Relationship between Oral Health and Arterial Sclerosis without Genetic Confounding through the Study of Older Japanese Twins.

OBJECTIVE: Although researchers have recently demonstrated a relationship between oral health and arterial sclerosis, the genetic contribution to this relationship has been ignored even though genetic factors are expected to have some effect on various diseases. The aim of this study was to evaluate oral health as a significant risk factor related to arterial sclerosis after eliminating genetic confounding through study of older Japanese twins. SUBJECTS AND METHODS: Medical and dental surveys were conducted individually for 106 Japanese twin pairs over the age of 50 years. Maximal carotid intima-media thickness (IMT-Cmax) was measured as a surrogate marker of arterial sclerosis. IMT-Cmax > 1.0 mm was diagnosed as arterial sclerosis. All of the twins were examined for the number of remaining teeth, masticatory performance, and periodontal status. We evaluated each measurement related with IMT-Cmax and arterial sclerosis using generalized estimating equations analysis adjusted for potential risk factors. For non-smoking monozygotic twins, a regression analysis using a "between within" model was conducted to evaluate the relationship between IMT-Cmax and the number of teeth as the environmental factor controlling genetic and familial confounding. RESULTS: We examined 91 monozygotic and 15 dizygotic twin pairs (males: 42, females: 64) with a mean (± standard deviation) age of 67.4 ± 10.0 years. Out of all of the oral health-related measurements collected, only the number of teeth was significantly related to arterial sclerosis (odds ratio: 0.72, 95% confidence interval: 0.52-0.99 per five teeth). Regression analysis showed a significant association between the IMT-Cmax and the number of teeth as an environmental factor (p = 0.037). CONCLUSIONS: Analysis of monozygotic twins older than 50 years of age showed that having fewer teeth could be a significant environmental factor related to arterial sclerosis, even after controlling for genetic and familial confounding.

Association of personality traits with oral health-related quality of life independently of objective oral health status: a study of community-dwelling elderly Japanese.

OBJECTIVES: Oral health-related quality of life (OHRQoL) is being increasingly used in epidemiologic studies of dentistry. However, patient-reported OHRQoL does not always coincide with clinical measures. Previous studies have shown a relationship between OHRQoL and personality, but did not concomitantly investigate oral function. We aimed to examine the association among personality traits, oral function, and OHRQoL using a large sample of community-dwelling Japanese elderly. METHODS: The participants (n = 938; age, 69-71 years) were drawn from a complete enumeration of an urban area and a rural area of both the Tokyo metropolitan area and Hyogo Prefecture. The self-perceived impact of OHRQoL was measured using the Geriatric Oral Health Assessment Index (GOHAI). The oral status and socioeconomic characteristics were recorded in each participant, and personality traits (neuroticism, extraversion, openness to experience, agreeableness, and conscientiousness) were assessed with the NEO-five-factor inventory. Multiple linear regression analysis was performed to examine the relationships between OHRQoL and other factors, with p < 0.05 considered to be statistically significant. RESULTS: Neuroticism was negatively associated with the GOHAI score in bivariate analyses (Spearman rank-order correlation coefficient (rs )= -0.20), whereas extraversion was positively associated (rs = 0.17). In the regression analyses, neuroticism (standardized partial regression coefficient (ß) = -0.179) and extraversion (ß=0.094) were significantly associated with the GOHAI scores independently of the number of teeth, maximal occlusal force, and financial status. CONCLUSIONS: Personality traits are associated with OHRQoL independently of objective measures of oral health status in community-dwelling elderly Japanese. CLINICAL SIGNIFICANCE: This study showed personality traits are associated with OHRQoL independently of dental status and oral function in old Japanese people. As elderly patients undergo increasingly complex dental treatments, there is a need to evaluate patient personality traits prior to dental treatment and predict patient expectations and responses to planned treatment. This is advantageous in determining the most appropriate therapy.

Replacement of a mandibular implant-fixed prosthesis with an implant-supported overdenture to improve maintenance and care.

PATIENTS: A 69-year-old woman presented to the Osaka University Dental Hospital. She had two chief complaints, (a) food accumulation under the lower teeth and (b) poor maxillary denture retention while eating. On clinical examination the patient presented with a maxillary complete denture and fixed mandibular implant prosthesis. For preventing food accumulation under the fixed implant prosthesis and to keep the maxillary denture stable by providing posterior occlusal contact for bilaterally balanced occlusion, the use of a mandibular implant-supported overdenture with self-adjusting magnetic attachments provided a prosthetic solution for this patient. After provided the new dentures, the patient was pleased and was comfortable with the aesthetic, stability and retention of the dentures. There were no discernable clinical or radiographic changes after 1 year of use. DISCUSSION: To prevent food accumulation beneath the fixed implant prosthesis and maintain the stability of the maxillary denture by providing posterior occlusal contact for bilaterally balanced occlusion, a mandibular implant-retained overdenture with magnetic attachments was used to provide a prosthetic solution for this patient. CONCLUSION: In this clinical case, an implant-fixed prosthesis in the edentulous mandibular region was replaced into an implant-supported overdenture with considerations for (a) preventing the food accumulation beneath the lower prosthesis, (b) achieving the proper occlusion in the posterior part for maxillary denture stability and (c) ease of maintenance and care for the prostheses.

Overeruption of teeth opposing removable partial dentures: a preliminary study.

One of the purposes of prosthodontic treatment is to prevent overeruption of opposing teeth, but there is currently minimal literature describing the efficacy of removable partial dentures (RPDs) in performing this function. This study investigated overeruption following RPD treatment. The study participants were 33 patients treated with RPDs, and overeruption was evaluated by comparing the surface computeraided design data of dental casts made at two different time points-before and after RPD treatment. Overeruption was observed in 38.1% of teeth opposed by the RPD, which was much less than the proportion of teeth that overerupted when not opposed by the RPD.

Influence of xerostomia on oral health-related quality of life in the elderly: a 5-year longitudinal study.

OBJECTIVE: Xerostomia and tooth loss are major oral health problems in the elderly. The aim of this longitudinal study was to characterize the influence of xerostomia on oral health-related quality of life (OHRQoL) among elderly Japanese people. STUDY DESIGN: A total of 99 community-dwelling, independently living individuals aged 60 years and older were interviewed and underwent dental examination at baseline and at a 5-year follow-up. The Oral Health Impact Profile-14 and the Xerostomia Inventory were used to assess OHRQoL and xerostomia severity, respectively. RESULTS: Participants whose xerostomia worsened over the 5-year period had a significantly poorer follow-up OHRQoL. Linear regression models showed that tooth loss and worsening xerostomia were significant predictors of poorer follow-up OHRQoL. CONCLUSIONS: Tooth loss and worsening xerostomia result in poorer OHRQoL among older Japanese people.

Masticatory performance in older subjects with varying degrees of tooth loss.

OBJECTIVES: The purpose of this study was to establish the factors influencing the masticatory performance of older subjects with varying degrees of tooth loss and associated numbers of posterior occlusal contacts. METHODS: The subjects consisted of 1274 independently living people aged 60 years and over. Individuals with partially or fully edentulous arches without a denture replacement or those having any symptoms related to an oral problem were excluded from the study participants. Masticatory performance, maximal occlusal force and stimulated whole saliva were measured. Subjects were grouped into three categories by posterior occlusal contact, according to the Eichner Index. Group A had contacts in four support zones; group B had one to three zones of contact or contact in the anterior region only; and group C had no support zones at all, although a few teeth could still remain. RESULTS: The masticatory performance in groups B and C was found to be 81% and 50% of that of group A, respectively. The multiple linear regression analysis showed that in all the groups, occlusal force was significantly associated with masticatory performance. In groups A and B, the number of residual teeth was significantly associated with masticatory performance, whereas in group C, it had no significant relationship with masticatory performance. Salivary flow rate had a significant correlation with masticatory performance only in group C. CONCLUSIONS: Declines in occlusal contact, occlusal force and salivary flow appear to be associated with reduction of masticatory performance in older adults. However, the crucial factors for masticatory performance varied, depending on the phase of occlusal collapse.

Comparison of GOHAI and OHIP-14 measures in relation to objective values of oral function in elderly Japanese.

OBJECTIVES: The aims of this study were to assess the correlations between the Geriatric Oral Health Assessment Index (GOHAI) and the Oral Health Impact Profile-14 (OHIP-14) and to examine which survey is more sensitive to objectively measured oral function in the Japanese elderly. METHODS: The subjects were 290 community-dwelling, cognitively healthy, and independently living people over the age of 60 years (mean: 66.3 years). Measures included the GOHAI and OHIP-14 questionnaires, as well as self-rating of general and oral health, dry mouth, number of residual teeth, and objective values of occlusal force, masticatory performance, and salivary flow rate. Bivariate and linear regression analyses were used to identify which of these variables predicted GOHAI and OHIP-14 scores. RESULTS: Spearman's correlation coefficient between the GOHAI and OHIP-14 scores was 0.728 (P < 0.001), although the OHIP-14 showed a greater number of 0 scores, suggesting a greater floor effect. At the bivariate level, self-rating of general and oral health, dry mouth, number of residual teeth, occlusal force, and masticatory performance were associated with GOHAI and OHIP-14 scores. Multiple linear regression analyses showed that after controlling for the other significant variables, both the occlusal force (standardized regression coefficient [ß] = -0.164, P = 0.004) and masticatory performance (ß = -0.125, P = 0.019) had significant associations with the GOHAI score, whereas this association was not found with the OHIP score. CONCLUSIONS: Although the GOHAI and OHIP-14 had a strong correlation, the GOHAI was more sensitive to the objective values of oral functions among independently living elderly persons in Japan.

Incidence and association of root fractures after prosthetic treatment.

PURPOSE: Common reasons for tooth extractions include periodontal disease, dental caries and root fracture. The purpose of this study was to investigate the association of tooth loss after prosthetic treatment, particularly incidences due to root fracture, which occur frequently and are difficult to prevent. METHODS: Data were collected from consecutively selected medical records of patients taken over 3 years after their initial visit to Osaka University Dental Hospital. Collected data included (1) age and gender, (2) number of teeth at the initial visit and number of extracted teeth, (3) reasons for extraction, (4) restored with or without a post and (5) abutment of removable partial dentures (RPDs). A Chi-squared test was applied among the reasons for extraction, whether the tooth was restored with a post or not and clasped or not. A logistic regression analysis was used to determine the associations of root fracture with the patient data. RESULTS: This study included 101 patients (296 extracted teeth). The reasons for extraction included periodontal disease (64.6%), caries (25.3%) and root fracture (10.1%). The percentage of root fracture was significantly higher for female than male, for restored teeth with posts than without posts and for abutment of RPDs than for non-abutment teeth. Logistic regressions showed that root fractures were significantly associated with gender and abutments. CONCLUSION: The most frequently stated reasons for tooth extraction after prosthetic treatment were periodontal disease and dental caries, followed by root fracture. Root fractures were significantly associated with gender and abutment teeth of RPDs.

Association of masticatory performance with age, gender, number of teeth, occlusal force and salivary flow in Japanese older adults: is ageing a risk factor for masticatory dysfunction?

OBJECTIVE: In general, ageing is a risk factor for sensory and motor deterioration, with the rate of decline varying amongst individuals. Concerning masticatory function, missing teeth along with oral disease seem to accelerate the dysfunction. Here, we aimed to confirm whether masticatory dysfunction by ageing is inevitable. This study investigated the effect of age, gender, number of natural teeth, occlusal force and salivary flow on the masticatory performance in a large sample of elderly adults. DESIGN: The study sample consisted of 1288 independently living people aged 60-84 years. Masticatory performance was determined by the comminuted particles of test food. Bilateral maximal occlusal force in the intercuspal position was measured with pressure sensitive sheets. Stimulated whole saliva was collected. RESULTS: Masticatory performance was significantly correlated to age, number of residual teeth, occlusal force and stimulated salivary flow rate by Pearson's correlation test. The multiple linear regression analysis showed that, with other variables controlled, masticatory performance was significantly associated with the number of residual teeth (ß=0.456, P<0.001), occlusal force (ß=0.244, P<0.001) and stimulated salivary flow rate (ß=0.069, P=0.003). Age was not related to masticatory performance (ß=-0.007, P=0.753). CONCLUSIONS: Declines in the number of residual teeth, occlusal force and salivary flow were associated with a reduction of masticatory performance in older adults. If tooth loss is not considered as an attribute of physiological ageing, then ageing by itself may not be a risk factor for masticatory dysfunction.

Shortening the xerostomia inventory.

OBJECTIVES: The aim of this study was to determine the validity and properties of the Summated Xerostomia Inventory-Dutch Version in samples from Australia, The Netherlands, Japan, and New Zealand. STUDY DESIGN: Six cross-sectional samples of older people from The Netherlands (n = 50), Australia (n = 637; n = 245), Japan (n = 401), and New Zealand (n = 167; n = 86) were enrolled. Data were analyzed by using the Summated Xerostomia Inventory-Dutch Version. RESULTS: All datasets revealed a single extracted factor which explained about one-half of the variance, with Cronbach alpha values ≥0.70. When mean scale scores were plotted against a "gold-standard" xerostomia question, statistically significant gradients were observed, with the highest score seen in those who always had dry mouth, and the lowest in those who never had it. CONCLUSIONS: The Summated Xerostomia Inventory-Dutch Version is valid for measuring xerostomia symptoms in clinical and epidemiologic research.