Associations of general health conditions with masticatory performance and maximum bite force in older adults: A systematic review of cross-sectional studies

The Mechanical Properties of Orthodontic Aligners of Clear Aligner After Intraoral Use in Different Time Periods

OBJECTIVE

Although the technique of orthodontic aligners has risen in popularity, their mechanical properties have not been thoroughly investigated. The aim of this study was to evaluate the mechanical properties of the orthodontic aligners Clear Aligner after intraoral use for 7, 10 and 14 days, and to compare them with as-received aligners (0 days). It was also sought to examine the properties of the unprocessed raw material (polyethylene glycol terephthalate) used to manufacture these aligners.

MATERIALS/METHODS

Thirty-two aligners by four patients were evaluated and studied at 0, 7, 10, 14 days of use. Each aligner was divided into three segments (two posterior and one anterior), which resulted in 96 samples. Also, 16 samples of unprocessed material were studied. For all samples, elastic modulus, ultimate tensile stress (UTS) and yield stress were calculated by conducting tensile testing. Additionally, material hardness was tested. The two-tailed Mann-Whitney test was performed, having set the level of significance at p = 0.05.

RESULTS

Analysis of the measurements indicated a statistically significant decrease in elastic modulus between days 0 and 14 of use, of UTS between days 0 and 7, 7 and 10, and of yield stress between days 0 and 7. For hardness, in every period, posterior segments demonstrated significantly higher values than anterior segments. All properties of the unprocessed material were statistically significantly higher than the processed samples.

CONCLUSIONS

The unprocessed material presented significant differences in every property tested in comparison to the processed aligners. The processed material showed further deterioration over time during use. The present study provides evidence that thermoforming and ageing affect the mechanical properties of the aligners.

Masticatory function and cognition in older adults: A population-based study

STATEMENT OF PROBLEM

The relationship between masticatory function based on paired teeth-functional tooth units (FTUs) and cognition has yet to be evaluated and reported in a nationally representative sample.

PURPOSE

The purpose of this population-based study was to investigate the association between masticatory function measured by FTUs and cognition in individuals aged 60 and older using data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014.

MATERIAL AND METHODS

Data from NHANES 2011-2014 were used. The number of FTUs was defined as pairs of opposing natural and artificial teeth in the posterior region. Cognitive function was assessed using the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) test, the Animal Fluency Test (AFT), and the Digit Symbol Substitution Test (DSST). Weighted multivariable linear regression and subgroup analyses were conducted to assess the association between FTUs and cognitive performance. Sensitivity tests were conducted on functional dentition and the presence of FTUs.

RESULTS

The regression models revealed a significant positive association between FTUs and cognitive performance among AFT, DSST, and global cognition. Individuals with higher FTU scores demonstrated better performance in verbal fluency, processing speed, sustained attention, working memory, and global cognition.

CONCLUSIONS

A significant and independent association was demonstrated between masticatory function as measured by FTUs and cognitive function in adults aged 60 and older.

Association Between Undernutrition and the Number of Molar Occlusions in Older Persons Requiring Care in Long-Term Care Insurance Facilities

Background/Objectives: Undernutrition increases the mortality risk in older persons requiring long-term care; further, it is associated with oral functions such as swallowing and chewing. Moreover, occlusion affects oral function and is crucially involved in nutritional intake. The present study aimed to examine the association between the number of molar occlusions and undernutrition according to body mass index (BMI) in older persons requiring long-term care. Methods: Japanese older persons requiring long-term care were categorized based on BMI (<20 kg/m2 vs. 20 kg/m2). We examined the association between undernutrition and the number of molar occlusions (one in each of the left and right premolars and molars, for a total of four). Results: Among 893 included participants, 440 (49.3%) had BMI < 20 kg/m2 and 453 (50.7%) had BMI > 20 kg/m2. Binomial logistic regression analysis revealed that BMI < 20 kg/m2 was significantly associated with increased number of molar occlusions (odds ratio: 0.52-0.70, 95% CI: 0.28-1.00). This indicated that a decrease in the number of molar occlusions was associated with malnutrition as determined through BMI in older persons requiring long-term care and residing in long-term care insurance facilities in Japan. Conclusions: Our findings suggest that maintaining occlusal support may help maintain nutritional status in older persons requiring long-term care.

Association of physical function with masticatory ability and masticatory habits: a cohort study

BACKGROUND

Few studies have evaluated masticatory ability and habits in relation to physical function. This study aimed to investigate the association of physical function with both masticatory ability and masticatory habits.

METHODS

In this cohort study, we followed up with 146 community-dwelling older adults aged 65-84 years for 1 year. Physical function domain scores on the Kihon Checklist were used to assess physical function. Masticatory ability was examined using objective measurements and self-administered questionnaires. Data on masticatory habits were obtained using self-administered questionnaires. The Mann-Whitney U test was used to analyze the association between masticatory ability and masticatory habits as exposures; logistic regression analysis was used to analyze the effect of exposure on the outcome.

RESULTS

A relationship was found between objective and subjective masticatory ability; however, no relationship was found between objective masticatory ability and masticatory habits. Furthermore, subjective masticatory ability and masticatory habits appeared to influence physical function 1 year later (odds ratio [OR]: 6.00, 95% confidence interval [CI]: 1.44-25.05; OR: 6.49, 95% CI: 2.45-17.22).

CONCLUSION

Masticatory ability and habits may be associated with a decline in physical function after 1 year in community-dwelling older adults. To maintain the physical function of these individuals, early intervention that addresses not only masticatory ability but also masticatory habits is necessary.

A Comparison of Oral Function in Older In- and Outpatients: An Observational Study

(1) Background: Insufficient data exist regarding oral function among older adults in Europe. Therefore, we aimed to assess and compare oral function between older in- and outpatients and identify predictors of low masticatory performance. (2) Methods: Patients were consecutively recruited from the outpatient center (n = 31) and the inpatient geriatric department (n = 31) at a tertiary University Hospital in Switzerland in 2023. Assessments on oral function included the total number of intraoral eruptive teeth, number of supporting zones with dentures, maximal bite force (Dental Prescale II, Fuji Film Corp., Tokyo, Japan), and masticatory performance (Hue-Check Gum©, University of Bern, Bern, Switzerland) using a visual (SA1-SA5) and a digital (SD_Hue) scale. The visual and digital assessment of masticatory performance showed a strong correlation (Kendall tau = 0.83). Low masticatory performance was defined as SA-Grade 1-2 (vs. SA3-SA5 as reference). In a multivariate model adjusting for age, sex, and clinical setting, we investigated associations of maximal bite force, few eruptive teeth, and few supporting zones with low masticatory performance. (3) Results: Mean age was 81.9 (standard deviation (sd) 5.2) years, and 62.9% were female. Overall, maximal bite force was 247 N (sd 261). A total of 39 patients (63.9%) had a low masticatory performance, 62.9% a low maximal bite force, and 50% a low number of eruptive teeth (<10). Masticatory performance, number of eruptive teeth, and maximal bite force did not significantly differ between in- and outpatients. The number of supporting zones was significantly higher in outpatients compared to inpatients (median 4, interquartile range (IQR) 4-4; vs. 4, IQR 2-4; p = 0.03). In the multivariate model, maximal bite force and a low number of eruptive teeth were independently associated with low masticatory performance (adjusted odds ratio 7.4 (95% CI, 1.8-30.4; p < 0.01), and OR 7.8 (95% CI, 1.7-36.4; p < 0.01), respectively). (4) Conclusions: Impaired oral function is highly prevalent in both European older in- and outpatients to a similar degree. The association of low masticatory performance with maximal bite force and with a low number of eruptive teeth may indicate that a basic screening should include either of these parameters to identify impaired oral function.

The predictive value of masticatory function for adverse health outcomes in older adults: a systematic review

Masticatory function is associated with a variety of health outcomes. The aim of this systematic review is to clarify the predictive value of masticatory function for adverse health outcomes, such as frailty, sarcopenia and malnutrition, in older adults. An online literature search covered articles published in English or Dutch in three databases (PubMed, Embase and CINAHL, last searched November 4th 2022). Inclusion criteria were: an observational study design, focus on adults aged ≥65 years and evaluation of the association between masticatory function and health outcomes. Reviews and articles published before the year 2000 were excluded. Methodological quality and risk of bias were assessed using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies of the U.S. National Institutes of Health. Study population demographics, methods for assessing masticatory function, and the association between masticatory function and adverse health outcomes were extracted. From the 34 included studies, 5 studies had a prospective design, 2 had a retrospective design, and the other 27 studies had cross-sectional design. The majority of the studies were conducted in Japan (74%, n = 26). Twenty studies (59%) used one indicator for masticatory function, the other 41% used two (n = 9) or more (n = 5) indicators. Masticatory function was most frequently assessed with the maximum occlusal force (MOF) (79%, n = 27). The identified health outcomes were clustered into 6 categories: physical parameters and sarcopenia, history of falling, nutritional status, frailty, cognitive function and mortality. Despite the complex and multidimensional character of both masticatory function and most identified adverse health outcomes, some significant associations were reported. Prospective studies showed that reduced masticatory function in older adults is associated with incidence of frailty and frailty progression, cognitive decline and all-cause mortality. Regarding the other identified adverse health outcomes, i.e., physical measures and sarcopenia, history of falling and nutritional status, only cross-sectional studies were available and results were less concordant. As all prospective studies showed that reduced masticatory function in older adults is associated with adverse health outcomes, prevention of decline of masticatory function by adequate oral care may contribute to healthy ageing.

Factors Related to Masticatory Rhythm in Patients with Oral Tumors

Background: Older adults who have undergone surgery for oral tumors are at increased risk of impaired masticatory rhythm. This study investigated the correlations between masticatory rhythm, objective masticatory performance, and subjective masticatory performance as well as factors related to masticatory rhythm. Methods: The participants were 44 adults (24 men, 20 women; age range 42~90 years old) who had undergone maxillectomy, mandibulectomy, or glossectomy and were rehabilitated with a maxillofacial prosthesis. The number of functional contact teeth pairs was confirmed by intraoral examination. Chewing rate, cycle duration, coefficient of variation (CV) for cycle duration (reflecting the stability of masticatory rhythm), and mixing ability were measured simultaneously using a mastication movement rhythm tracking device during gum chewing. Maximum occlusal force was measured using the dental prescale system. Patients' perception of chewing ability was rated using a questionnaire. Results: The Spearman's rank correlation test revealed that mixing ability, patient-rated masticatory scores, cycle duration, CV for cycle duration, and maximum occlusal force showed significant correlations with chewing rate. Multiple linear regression analysis identified mixing ability and the CV for cycle duration as significant predictors of masticatory rhythm. Conclusions: Factors associated with a faster chewing rate were higher mixing ability and masticatory scores, greater maximum occlusal force, shorter cycle duration, and smaller CV for cycle duration. Stable masticatory rhythm and mixing ability are significant predictors of chewing rate. Poor masticatory performance and unstable masticatory rhythm can result in slower chewing and thus a higher risk of inadequate dietary intake.

Effect of artificial eccentric occlusal interferences on masticatory performance: A randomised double-blind clinical trial

BACKGROUND

Occlusal interferences lead to changes in mandibular kinematics to compensate and improve function. However, the effects of different types of eccentric disturbance on the comminution capacity are not known.

OBJECTIVE

To determine the immediate effect of eccentric occlusal interferences on masticatory performance.

METHODS

This crossover clinical trial included 12 healthy dentate subjects aged 25.2 ± 3.3 years who were randomly submitted to seven types of occlusal interference: unilateral and bilateral laterotrusive and mediotrusive, protrusive, dummy and control (no interference). The interference forms were planned in a semi-adjustable articulator, fabricated with composite resin and adhered to the mandibular first molars such that subjects' maximum intercuspation was maintained. Masticatory performance and the chewing rate during 20 cycles were evaluated during subjects' comminution of silicone test food under one interference condition per test day; the multiple sieve method was applied to the comminuted particles. The interference was removed upon test completion, and a 1-week washout period was applied between tests.

RESULTS

Comminuted median particle sizes were larger under unilateral (4.94 ± 0.41 mm) and bilateral (4.81 ± 0.49 mm) laterotrusive, bilateral mediotrusive (4.65 ± 0.50 mm) and protrusive (4.83 ± 0.54 mm) interferences (p < .05) than under the control (4.01 ± 0.52 mm) and dummy (4.18 ± 0.58 mm) conditions (p < .05). Only unilateral and bilateral laterotrusive interferences narrowed the comminuted particle size dispersion (p < .05). The chewing rate did not differ among conditions (p = .1944).

CONCLUSION

Artificial eccentric interferences had an immediate adverse effect on masticatory performance by resulting in larger comminuted particles.

CLINICAL TRIAL REGISTRATION

Brazilian Registry of Clinical Trials (RBR-8g5zfg8).