Ten-year longitudinal study on the state of dentition and subjective masticatory ability in community-dwelling elderly people

Association Between Masticatory Difficulty and Chronic Cough in a Korean Population

OBJECTIVE

Chronic cough, a common outpatient symptom, has various aetiologies, including upper airway cough syndrome, asthma, and gastroesophagoeal reflux. The potential link between dental issues and respiratory diseases has recently garnered attention. This study aims to investigate the association between masticatory difficulty and chronic cough using data from the 2011-2015 Korean National Health and Nutrition Examination Survey (KNHANES).

METHODS

Analysis included 9706 individuals from KNHANES. Participants self-reported masticatory function and chronic cough. Covariates included age, sex, underlying diseases, socioeconomic status, lifestyle factors, and laboratory markers. Binary logistic regression analysed odds ratios for chronic cough covariates. Multiple logistic regression assessed adjusted odds ratios for masticatory difficulty.

RESULTS

Masticatory difficulty prevalence was 32.2%, with chronic cough higher in this group (4.8%) than in the group without masticatory difficulty (3.0%). After adjusting for socioeconomic status, lifestyle factors, and laboratory markers, masticatory difficulty was significantly associated with greater chronic cough prevalence (odds ratio, 1.137; 95% confidence interval, 1.134-1.140).

CONCLUSIONS

Masticatory difficulty was linked with an elevated chronic cough risk in Korean healthy adults. Further research, including prospective studies and detailed investigations into gastroesophagoeal reflux disease and microbiological studies, is warranted to elucidate the impact of mastication on respiratory health. As masticatory difficulty may serve as a clinical indicator for chronic cough interdisciplinary collaboration between dental and respiratory health professionals can facilitate early intervention and enhance patient care.

Association Between Reduced Posterior Occlusal Contact and Alzheimer's Disease Onset in Older Japanese Adults: Results from the LIFE Study

BACKGROUND

An association between poor oral health and cognitive decline has been reported. Most of these studies have considered the number of teeth as a criterion, only a few studies have analyzed the relationship between occlusal status and Alzheimer's disease (AD).

OBJECTIVE

To elucidate whether posterior occlusal contact is associated with AD, focusing on the Eichner classification, among an older population aged 65 years or older in Japan.

METHODS

This study used monthly claims data of National Health Insurance in Japan from April 2017 to March 2020. The outcome was newly diagnosed AD defined according to ICD-10 code G30. The number of teeth was estimated by dental code data, and occlusal contact was divided into three categories, namely A, B, and C, according to the Eichner classification. Multivariate Cox proportional hazards models were used to analyze the association between a new diagnosis of AD and the Eichner classification.

RESULTS

A total of 22,687 participants were included, 560 of whom had newly diagnosed AD during a mean follow-up period of 12.2 months. The AD participants had a lower proportion of Eichner A and a higher proportion of Eichner C. After adjusting for covariates, hazard ratios (95% confidence intervals) with Eichner B and C were 1.34 (1.01-1.77) and 1.54 (1.03-2.30), respectively.

CONCLUSION

In older people aged≥65 years old, reduced posterior occlusal contact as well as tooth loss have an impact on AD. This study emphasizes the importance of paying attention to occlusal contacts to reduce the risk of AD.

Assessment and Improvement of Masticatory Performance in Frail Older People: A Narrative Review

According to the World Health Organization (WHO), the estimated number of older adults is around 962 million and is projected to increase to 2.1 billion by 2050. The oral frailty concept is associated with gradual oral function loss in relation to aging. There is a need to emphasize the improvement of oral function based on an evaluation of masticatory performance in patients with various oral conditions or systemic diseases and especially in the frail elderly. The present narrative review presents an overview of the current state of the assessment and improvement of masticatory performance in frail older people. To fully encompass oral frailty, oro-facial hypofunction, or oro-facial fitness, dental Patient Reported Outcomes (dPROs) should be included; nevertheless, there are limited evidence-based rehabilitation approaches. The concept of oral frailty, oro-facial hypofunction, or oro-facial fitness should involve dental Patient Reported Outcomes (dPROs), and in this sense, there are only a few evidence-based rehabilitation procedures to improve oro-facial hypofunction besides prosthodontics. It must be considered that reduced neuroplastic capacity in old individuals might preclude a positive outcome of these strategies that might need to be accompanied by functional training and nutritional counseling.

Periodontitis and peri-implantitis in elderly people experiencing institutional and hospital confinement

An increasing number of elderly people retain their natural teeth into old age and further, the prevalence of endosseous implants for supporting oral prosthesis is ever increasing. These teeth and implants now present a considerable challenge in terms of maintenance, especially when patients become dependent on care. Periodontal and peri-implant diseases are more prevalent in elderly than in younger age cohorts. There are distinct differences related to the inflammatory response between periodontal and peri-implant tissues, both in young and old age. The age-related reasons for the increase in periodontal infections may be related to poor oral hygiene because of a loss of dexterity or vision, but also to immunosenescence. This term describes the aging of the immune system and the decline of its effectiveness with age. Low-grade infections, like chronic periodontitis, may cause low-grade inflammation and subsequently increase the likelihood of developing chronic diseases. In return, treatment of periodontitis may improve general health, as demonstrated for diabetes. A second mechanism illustrating how poor oral health translates into systemic disease is the risk of developing aspiration pneumonia. The treatment options in old age should be evaluated with regard to the issues of general health and maintenance. Systematic periodontal maintenance therapy, as performed in younger age cohorts, may be difficult to implement in elderly people experiencing institutional or hospital confinement because of logistics, barriers related to patients and caregivers, or cost. The scale of periodontal disease in old age represents a public health issue.

Oral factors and adherence to Mediterranean diet in an older Greek population

PURPOSE

The aim of this study was to investigate the effect of oral factors on adherence to the Mediterranean diet in an older population METHODS: 130 persons over 60 years visiting Open Care Community Centers for Older People participated in this study. Oral interviews recorded demographic and sociomedical information, subjective oral complaints, and dental habits. Adherence to Mediterranean diet was assessed using the MDI_BNC4H index (range: 0-14). An oral examination was performed, and evaluation of the masticatory performance was carried out using a two-color chewing gum that was digitally analysed.

RESULTS

The mean age of the study participants was 73.9 ± 8.5 years. The score of adherence to the Mediterranean diet ranged from 3 to 9 (5.6 ± 1.4). 58 participants used removable prostheses, while 20 used a pair of complete dentures. Univariate analyses revealed that the parameters that negatively significantly, or marginally significantly, affected the level of adherence to the Mediterranean diet were lower masticatory performance (p = 0.050), larger number of drugs per day (p = 0.056), higher BMI (p = 0.043) and smoking (p = 0.053). The multivariable analysis revealed that lower adherence to the Mediterranean diet was significantly associated with higher BMI (p = 0.047) and lower masticatory performance (p = 0.050).

CONCLUSIONS

Increased masticatory performance was an independent predictor of better adherence to the Mediterranean diet in an older population.

Oral diadochokinesis and associated oro-facial function in young and old German mother-tongue speakers: A cross-sectional study

Objectives

The aims of this study were to compare oral diadochokinesis and to test associations with oro‐facial functional parameters in healthy young and old German speakers.

Background

Oral diadochokinesis is a key component in the concept of oro‐facial hypofunction and relates to tongue and lip motor function but may depend on the linguistic background.

Materials and methods

Healthy German speakers with a minimum of 20 teeth were recruited to form a young (<60 years) and an older group (≥60 years). Oral diadochokinesis was assessed as the number of repetitions/s for the monosyllables /pa/, /ta/ and /ka/ to evaluate movement capacity of the lip, the anterior region of the tongue and the posterior region of the tongue, respectively. Maximum voluntary lip force, maximum voluntary bite force, masticatory performance, maximum voluntary tongue pressure, xerostomia and swallowing function were assessed with validated instruments. Results are presented as median (IQR).

Results

Sixty participants formed the younger group (n = 35, 30.0 years [24.0‐49.0]) and the older group (n = 25, 64.0 years [62.0‐72.0]). Counts/s of /ta/ were different between age groups (younger group: 6.0 vs older group: 5.4) but not for syllables /pa/ (younger group: 6.0 vs older group: 5.8) and /ka/ (younger group: 5.6 vs older group: 5.0). The oral diadochokinesis with /pa/ was overall associated with maximum voluntary lip force; oral diadochokinesis performed with /ta/ was associated with tongue pressure, and oral diadochokinesis with /ka/ with swallowing function. Masticatory performance was not associated with oral diadochokinesis but with maximum voluntary bite force, xerostomia and with maximum voluntary tongue pressure.

Conclusions

The published thresholds for oral diadochokinesis should be reconsidered in non‐Japanese mother‐tongue speakers. However, they still play an important role in the overall concept of oro‐facial functional assessment.

A conceptual model of oro-facial health with an emphasis on function

The individual inclination to lead an autonomous life until death is associated with requirements that may be of physiological, psychosocial and environmental nature. We aim to describe a conceptual oro‐facial health model with an emphasis on oro‐facial function, taking the domains of quality of life and patient‐centred values into account. In the context of oro‐facial function, the requirements of life are met when the oro‐facial system is in a fit state. ‘Fitness of the oro‐facial system, that is oro‐facial health, is a state that is characterised by an absence of, or positive coping with physical disease, mental disease, pain and negative environmental and social factors. It will allow natural oro‐facial functions such as sensing, tasting, touching, biting, chewing, swallowing, speaking, yawning, kissing and facial expression’. In the presented conceptual model of oro‐facial health, it is postulated that each individual has present and future potentials related to biological prerequisites and resources that are developed by an individual through the course of life. These potentials form the oro‐facial functional capacity. When the individual potentials together do not meet the requirements of life anymore, dysfunction and disease result. The oro‐facial system is subject to physiological ageing processes, which will inevitably lead to a decrease in the oro‐facial functional capacity. Furthermore, comorbid medical conditions might hamper oro‐facial function and, alongside with the ageing process, may lead to a state of oral hypofunction. Currently, there is a lack of widespread, validated, easy‐to‐use instruments that help to distinguish between states of oro‐facial fitness as opposed to oral hypofunction. Clearly, research is needed to establish adequate, validated instruments alongside with functional rehabilitation procedures.

Risk Factors for Tooth Loss in Patients with ≥25 Remaining Teeth Undergoing Mid-Long-Term Maintenance: A Retrospective Study

Tooth loss represents a diffused pathologic condition affecting the worldwide population. Risk factors have been identified in both general features (smoking, diabetes, economic status) and local tooth-related factors (caries, periodontitis). In this retrospective study, we examined the data of 366 patients with a large number of remaining teeth (≥25) undergoing maintenance therapy in order to identify specific risk factors for tooth loss. The number of remaining teeth, number of non-vital teeth, and number of occlusal units were investigated for their correlation with tooth loss. The mean follow-up of patients was 9.2 years (range 5 to 14). Statistically significant risk factors for tooth loss were identified as number of remaining teeth at baseline (p = 0.05), number of occlusal units (p = 0.03), and number of non-vital teeth in posterior regions (p < 0.001). Multiple logistic regression showed that the number of occlusal units and number of non-vital teeth in the posterior regions were significantly associated with a greater risk of tooth loss (odds ratio 1.88 and 3.17, respectively). These results confirm that not only the number of remaining teeth, but also their vital or non-vital status and the distribution between the anterior and posterior regions influence the long-term survival.

Association between the dental occlusion and perceived ability to eat foods of Taiwanese older adults

Tooth loss is a common problem among older adults that affects masticatory function (MF) and food selection. Financial burden is a reason that some older adults in Taiwan with this condition forgo dental restoration. To identify the number of posterior occlusal support areas (POSAs) associated with MF. Large-scale cross-sectional study included 1100 community-dwelling participants of Taiwan aged ≥65 years. Participants completed dental examination and questionnaires through personal interviews. Masticatory performance was evaluated using a colour-changeable chewing gum. Masticatory ability was evaluated on the basis of how many of 14 common foods the participants were able to eat. Participants were grouped into 10 categories (A1-A3, B1-B4 and C1-C3) according to the Eichner index (EI) of posterior occlusal contacts. Multivariable regression models were used to analyse the association between the EI groups and MF. More than 80% of the participants with two or more POSAs (those in groups A1-B2) could easily eat various foods. Compared with those in groups A1-B2, those in groups in B3, B4, C1, C2 and C3 exhibited a significantly different masticatory performance (all P < .001) and significantly higher difficulty in eating fruits and vegetables. A dose-response effect between POSAs and perceived masticatory ability to eat fruits and vegetables was observed (P < .05 for both trends). Preservation of at least two POSAs is essential for MF. Older adults with tooth loss can undergo the restoration of two POSAs to improve MF and increase food intake.

Consensus on the terminologies and methodologies for masticatory assessment

A large number of methodological procedures and experimental conditions are reported to describe the masticatory process. However, similar terms are sometimes employed to describe different methodologies. Standardisation of terms is essential to allow comparisons among different studies. This article was aimed to provide a consensus concerning the terms, definitions and technical methods generally reported when evaluating masticatory function objectively and subjectively. The consensus is based on the results from discussions and consultations among world‐leading researchers in the related research areas. Advantages, limitations and relevance of each method are also discussed. The present consensus provides a revised framework of standardised terms to improve the consistent use of masticatory terminology and facilitate further investigations on masticatory function analysis. In addition, this article also outlines various methods used to evaluate the masticatory process and their advantages and disadvantages in order to help researchers to design their experiments.

Risk factors for abutment and implant fracture after loading

PURPOSE

Implant component fractures are one of the most serious complications in implant treatment. With a better understanding of the risk factors for fracture in the preoperative, surgery, superstructure, and post-loading phases of implant treatment, low-risk treatment could reduce implant component fractures, leading to a better prognosis. The aim of this study was to clarify the risk factors for abutment and implant fractures that occur after loading, and to perform a retrospective, approximately 10-year follow-up study to explore the risk factors in each treatment phase.

METHODS

Subjects were fitted with an implant prosthesis between January 2008 and December 2009. In total, 1,126 Ankylos implants in 430 patients were included for analysis. Binary logistic regression analysis was performed to extract factors related to non-fracture and fracture of the abutment or implant as a dependent variable.

RESULTS

Gender (OR = 3.466, 95% CI 1.296-9.268, P = 0.013), gonial angle (OR = 3.420, 95% CI 1.308-8.945, P = 0.012), and splinting status of the superstructure (OR = 4.456, 95% CI 1.861-10.669, P = 0.001) were identified as significant risk factors.

CONCLUSION

The risk of fracture is increased in males, especially those with a mandibular angle of less than 120° on panoramic radiographs, and those with a non-splinted superstructure.

Decrease in posterior occlusal support area can accelerate tooth loss: The Suita study

Purpose A decrease in posterior occlusal support is considered to increase the load on remaining teeth and thus accelerate tooth loss. Therefore, a follow-up study was carried out to perform a longitudinal analysis of the association between the posterior occlusal support region and tooth loss.Methods The participants of the study were 806 Suita Study participants who underwent physical health checkups both at baseline and at follow-up. The participants were classified into three groups by posterior occlusal support area (POSA) using the Eichner Index at baseline: Perfect POSA group, Eichner A; Decreased POSA group, Eichner B1-3; and Lost POSA group, Eichner B4 and Eichner C1-2. Participants were also classified into two groups according to whether they had tooth loss during the follow-up period. Tooth loss risk factors were investigated through the construction of logistic regression models with tooth loss as the dependent variable and posterior occlusal support, sex, age, periodontal disease, stimulated salivary flow rate, smoking habit, drinking habit, denture wearing, utilization of dental services, brushing habits, diabetes mellitus, osteoporosis and number of years of follow-up as independent variables.Results In the results of the logistic regression model, the adjusted odds ratio (95%CI) for tooth loss with the Perfect POSA group as the reference was 3.19 (1.98-5.14) for the Decreased POSA group and 4.57 (1.97-10.62) for the Lost POSA group.Conclusions This study showed that decreased POSA accelerated tooth loss in the general urban population.

Correlation between prognostic nutritional index and occlusal status in gastric cancer

OBJECTIVE

Systemic inflammatory responses in cancer patients are important factors for nutrition and prognosis. This study evaluates the association between tooth loss, occlusal status, and prognostic nutritional index (PNI).

METHODS

A total of 93 patients with gastric cancer were included. These parameters were investigated the following: stage, body mass index (BMI), total lymphocyte count, C-reactive protein (CRP), PNI, and albumin (ALB). Patients were divided into three groups by Eichner classification (group A had contact in four support zones; group B had in one to three zones or in anterior region; and group C had no contact). PNI assumed 40 or less undernutrition. Multiple regression analysis was performed (PNI, dependent variable; Eichner index, main independent variable), using four independent variables (sex, age, BMI, and CRP) as adjustment factors.

RESULTS

The mean ± SD PNI in groups A, B, and C was 43.0 ± 4.7, 41.7 ± 5.2, and 36.7 ± 7.7, respectively. A significant positive correlation was found between the number of teeth, both ALB, and PNI. ALB and PNI differed significantly between groups A and C (ALB, p = .0003; PNI, p = .005).

CONCLUSION

We recommend a preoperative dental evaluation for assessing the nutritional status of patients with gastric cancer.

Screening for masticatory disorders in older adults (SMDOA): An epidemiological tool

PURPOSE

Masticatory changes in the older adult population may cause nutritional impairment, so epidemiological studies are important to allow specific public health interventions. Thus, this study aims at constructing and validating an instrument for screening for masticatory disorders in older adults (SMDOA).

METHODS

Validation study. First step: validity evidence based on test content. Defining the construct and elaborating the questions by a panel of experts and evaluating the representativeness and relevance of the items in relation to the construct by a committee of 28 experts. Analysis was performed through the Content Validity Index for Items (CVI-I) and the Content Validity Index (CVI). Second stage: validity evidence based on response processes. The questionnaire was applied to 40 older adults (≥60 years) using the cognitive interview strategy. Quantitative and qualitative analysis of the responses was carried out. Third stage: validity evidence based on the internal structure. The instrument was applied to 295 older adult patients and a confirmatory factorial analysis was performed to fit the model.

RESULTS

The first version of SMDOA consisted of 16 issues related to chewing. The CVI and CVI-I were satisfactory, and only one question was excluded. The instrument with 15 questions was well evaluated by the older adults, only requiring minor adjustments to the morphosyntax. After the confirmatory factorial analysis, adjustments were made in its internal structure resulting in the 9-question model in two factors regarding function and masticatory perception.

CONCLUSIONS

The SMDOA presented good evidence of validity in its content, response processes and internal structure.

Food avoidance is associated with reduced dentitions and edentulousness

OBJECTIVES

To investigate associations between food avoidance and dental status, age, gender, and socio-economic status (SES).

MATERIALS AND METHODS

The Chinese sample comprised 1463 dentulous (≥ 1 tooth in each jaw) and 124 edentulous (in one or both jaws) participants aged ≥ 40 yrs. The Vietnamese sample comprised 2820 dentulous and 253 edentulous participants aged ≥ 20 yrs. Food avoidance due to chewing difficulties was scored for regionally common 4 soft and 4 hard foods. Dental status was classified according to the multi-level hierarchical dental functional classification system (HDFC) based on the number and location of teeth and posterior occlusal pairs. Associations were analyzed using multivariate logistic regression analyses.

RESULTS

For dentulous participants, the chance of avoiding foods was significantly larger with < 10 teeth in each jaw (OR = 2.26 (Chinese sample), respectively 1.74 (Vietnamese sample)), incomplete anterior region (OR = 1.78, respectively 1.84), "impaired" premolar region (OR = 2.22, respectively 1.71), or "impaired" molar region (OR = 2.46, respectively 1.84). Edentulous participants had twice the chance of avoiding foods (OR = 2.01 respectively 2.20). Avoiding foods was significantly associated with higher age. Participants of low SES (Chinese sample, OR = 1.93) and females (Vietnamese sample, OR = 1.27) had a larger chance of avoiding foods.

CONCLUSIONS

Avoiding foods was significantly associated with reduced dentitions, edentulousness, and higher age; low SES only in the Chinese and being female only in the Vietnamese sample.

CLINICAL RELEVANCE

Incomplete anterior regions, "impaired" premolar or molar regions, and especially edentulousness can be considered significant risk indicators for food avoidance.

The Eating Experience: Adaptive and Maladaptive Strategies of Older Adults with Tooth Loss

OBJECTIVE

To explore the eating experience and eating-related quality of life (ERQOL) of community-dwelling older adults with tooth loss.

METHOD

Nineteen older adults from the clinics of a northeast US dental school who met inclusion criteria (>65 y old, <20 teeth, and no dentures) composed the sample. For this mixed methods study, demographic characteristics, number and location of teeth, Mini Nutritional Assessment-Short Form score, and anthropometrics data were collected; semistructured interviews were conducted to collect in-depth information about the eating experience and ERQOL. Thematic analysis was completed with NVivo 12 software (QSR International).

RESULTS

Participants' mean age was 71.3 y (SD = 5.2); 52.6% (n = 10) were women; 63.2% (n = 12) were Black or African American. The mean Mini Nutritional Assessment-Short Form score of 12.1 was reflective of normal nutrition status; 31.6% (n = 6) of patients were at risk for malnutrition or were malnourished. Fifteen percent (n = 3) were fully edentulous; 84.2% (n = 16) had 1 to 19 teeth (mean = 10.8, SD = 6.5). The 2 overarching themes identified were adaptive and maladaptive behavioral responses to tooth loss. Adaptive strategies included modification in food preparation and cooking methods, food texture selection, meal timing, and approaches to chewing. Maladaptive behaviors included food avoidance and limiting eating and smiling in front of others. Psychosocial factors, including finances, limited food choices and ERQOL, whereas the support of family and friends enhanced ERQOL according to participants.

CONCLUSION

Older adults with tooth loss exhibit both adaptive and maladaptive behaviors that affect their eating experience, dietary intake, and ERQOL. While many expressed positive adaptive coping strategies, they also described maladaptive behaviors, including avoidance of healthy foods and limiting eating during social interactions, which may affect their nutritional status and overall health and well-being. Further research is needed to explore how duration and severity of tooth loss influence these behaviors and risk of malnutrition. Interprofessional approaches are needed to support positive adaptation and coping with tooth loss.

KNOWLEDGE TRANSFER STATEMENT

The results of this study can be used by health professionals treating patients with tooth loss in an effort to improve their eating experience and eating-related quality of life. The findings provide data to support further studies and the need for evidence-based guidelines and educational materials to meet the unique needs of older adults with tooth loss.

Factors Influencing the Changes in Masticatory Performance: The Suita Study

Introduction:

Although previous studies have identified various factors related to masticatory performance, which factors affect longitudinal changes in masticatory performance have not been clarified.

Objectives:

We aimed to clarify factors involved in changes to masticatory performance and construct models from factors related to masticatory performance in a longitudinal study of a general urban population in Japan.

Methods:

A total of 1,005 Japanese subjects (411 men, 594 women; mean age at baseline, 65.7 ± 7.7 years; mean follow-up period, 5.0 ± 0.9 years) were included in the Suita study. These subjects participated in dental checkups both at baseline (June 2008–December 2011) and at follow-up (June 2013–January 2017). The number of functional teeth and occlusal support areas was recorded and the latter assessed using the Eichner index. Subjects’ periodontal status was evaluated based on the Community Periodontal Index. Masticatory performance was determined using test gummy jelly. Factors affecting masticatory performance at follow-up and the degree of their effect were investigated by multiple linear regression analysis.

Results:

In multiple linear regression analysis with masticatory performance at follow-up as the dependent variable, baseline age, masticatory performance, number of functional teeth, and maximum bite force were significant independent variables. The results of multiple linear regression analyses by occlusal support at baseline identified only maximum bite force at baseline in subjects who were Eichner A and baseline age, masticatory performance, and number of functional teeth in subjects who were Eichner B as significant independent variables concerning masticatory performance at follow-up.

Conclusion:

Our study showed a relationship between longitudinal changes in masticatory performance and age, number of functional teeth, and maximum bite force and furthermore showed that the effects of these factors vary according to the residual number of occlusal support areas.

Knowledge Transfer Statement:

Patients and clinicians should recognize the importance of objective and quantitative assessment for chewing efficiency and understand that various factors are related to longitudinal changes in masticatory performance. The results of this study can provide basic data for preventing or improving the decline in masticatory performance for elderly people with varying numbers of occlusal support areas.

Relationship between status of dentition and incident functional disability in an elderly Japanese population: prospective cohort study of the Tsurugaya project

PURPOSE

The purpose of this study was to examine whether the status of dentition is associated with incident functional disability in elderly people.

METHODS

This prospective cohort study targeted community-dwelling Japanese adults of age ≥70 years (n=838). Participants were classified into the following four groups in accordance with Miyachi's Triangular Classification, which represents the status of dentition on the basis of numbers of remaining teeth and occlusal supports: Zone A, ≥10 occlusal supports; Zone B, 5-9 occlusal supports; Zone D, ≤4 occlusal supports and ≥11 remaining teeth and Zone C, ≤10 remaining teeth. Incident functional disability was defined by the first certification of long-term care insurance in Japan. Data regarding age, sex, body mass index, medical history, smoking, alcohol consumption, education, depressive symptoms, cognitive impairment, social support, history of fall, and subjective masticatory ability were collected.

RESULTS

During follow-up for 5185 person-years, 305 participants experienced functional disability. Considering the follow-up data of  ≥3 years from baseline, participants in Zones C (hazard ratio [HR], 1.98; 95 % confidence interval [CI], 1.26-3.11) and D (HR, 2.50; 95 %CI, 1.54-4.05) were found to be more likely to develop functional disability than those in Zone A (p for trend=0.002).

CONCLUSIONS

Status of dentition was associated with incident functional disability in an elderly Japanese population. The findings of this study suggest that maintenance of remaining teeth and retention of occlusal supports contribute to the prevention of functional disability.

Association of mastication and factors affecting masticatory function with obesity in adults: a systematic review

Background

A substantial number of adults suffer from obesity, that is caused by the risk factor, masticatory dysfunction. The association between mastication and obesity, however, is inconclusive. This systematic review aims to provide literature regarding the association between mastication and factors affecting masticatory function, and obesity in adults.

Methods

Four electronic databases (PubMed, EMBASE, Cochrane Library, and Web of Science) were used to search for publications that met the following criteria: published between 2007 and 2016, written in English, and assessed the associations between mastication and obesity among the population aged ≥18 years. The included publications were analyzed based on the study design, main conclusions, and strength of evidence identified by the two authors who screened all the abstracts and full-text articles and, abstracted data, and performed quality assessments by using a critical appraisal tool, the Critical Appraisal Skills Programme Cohort Studies Checklists.

Results

A total of 18 articles (16 cross-sectional, 1 cohort studies, and 1 randomized controlled trial [RCT]) met our inclusion criteria and were evaluated. Poorer mastication was associated with obesity in 12 out of 16 cross-sectional studies. One cohort study showed that the obesity group displayed higher tooth loss than the normal weight group. One RCT demonstrated that gum-chewing intervention for 8 weeks significantly decreased waist circumference.

Conclusions

Most studies revealed a positive association between mastication and obesity among adults. Nonetheless, most of them are cross-sectional studies, which are insufficient to demonstrate a causal relation. Further advancement requires RCT, especially an intervention of improvement of mastication and obesity needed to confirm this association.

Electronic supplementary material

The online version of this article (10.1186/s12903-018-0525-3) contains supplementary material, which is available to authorized users.