The relationships between mastication and cognitive function: A systematic review and meta-analysis.

Masticatory function such as chewing is expected to modify human cognitive function, and/or the possibility of improving cognitive function is also predicted. This systematic review investigated whether masticatory function affects cognitive function for older/young adults. Full articles written in English from January 2000 to April 2022 were collected using PubMed and Cochrane Library. Target outcomes were cognitive function test scores, cognitive processing speed (reaction time), and masticatory function. For each research question, two independent reviewers conducted the search and screening, data extraction, quality assessment, and risk of bias assessment. The reviewers resolved any disagreements by discussion. From 226 articles retrieved, 20 were included in this review. Older adults with lower scores on the cognitive function test had lower masticatory performance, lower chewing ability, chewing difficulty, and decreased number of teeth. An increased risk of cognitive impairment was found in older adults with masticatory dysfunction. For young adults, gum chewing significantly reduced the processing speed of cognitive tasks compared to no gum chewing. Although most of the evidence included had a low level of evidence and a high risk of bias because of the research designs, the results still suggest that mastication may be a factor in improving cognitive function.

The impact of residual ridge morphology on the masticatory performance of complete denture wearers.

Statement of the problem: Morphology of the residual ridge (RR) is expected to influence the masticatory performance (MP) of complete denture (CD) patients, but considerable details of this relationship are unknown. Purpose: We aimed to investigate the association between the objective MP and RR morphology of CD wearers and other contributory factors affecting their MP. Materials and methods: Sixty-five patients with well-fitting upper and lower CDs with no complaints of pain were enrolled. The objective MP was measured using test gummy jelly and a fully automated measuring device. The RR form was divided into U-type, V-type, I-intermediate, and F-Flat, then combinations of upper and lower RR forms (combined RR) were classified. The height was measured using CD's denture basal surface replicas, while occlusal contact of CDs was assessed using a tooth contact analysis system. The relationship between surveyed factors and MP was evaluated using Spearman's rank correlation, Kruskal-Wallis test, generalized linear regression, and analysis of covariance. Results: Participants with F-F and V-F combined RR forms had the lowest MP, while those with U-U and U-I forms had the highest MP, regardless of RR height. Participants with low RR height had the lowest MP, and those with high RR height had the highest MP, regardless of RR form. The analysis of covariance revealed that mandibular RR height, combined RR forms, and total occlusal contact area significantly affected the MP. Conclusions: Our findings confirmed that the mandibular RR height, RR form combinations, and occlusal contact influence the MP of CD wearers.ClinicalImplications:The MP of CD wearers varied, depending on the height and form of the RR, as well as the occlusal contact area of the CDs. The results of this manuscript show that the morphology of the denture bearing area and the occlusion of the CDs are essential factors in predicting the treatment outcome of CD wearers. This allows the clinician to fabricate a complete denture with the denture basal surfaces adjusted and occlusion provided according to the patient. CD patients can be educated on how to chew to improve MP based on their own RR morphology.

Effect of mandibular bilateral distal extension denture design on masticatory performance.

PURPOSE: Removable partial dentures have a wide range of applications as missing tooth prostheses, and the denture design can be quite diverse. However, the factors affecting masticatory function remain unclear. We investigated the effect of denture design, especially the use of indirect retainers and major connectors, on masticatory function in patients with mandibular bilateral distal extension dentures. METHODS: Fifty-three patients with mandibular Kennedy Class I and Eichner classification B occlusal support were included in this study. Masticatory performance (MP) was assessed using gummy jelly. For the dentures, the type of major connector (bar or apron), presence or absence of indirect retainers, number of rests, and number of artificial teeth were evaluated. The number of functional teeth and occlusal support, Eichner classification, maxillary denture usage, mandibular residual ridge height, and duration of denture use were also evaluated. The factors influencing on the MP were evaluated using the Mann-Whitney U test, Spearman's correlation coefficient, and logistic regression analysis. RESULTS: MP was significantly higher when the major connector was bar-type or when there was an indirect retainer than with an apron-type or no indirect retainer. MP was positively correlated with the number of functional teeth, occlusal support, and number of rests. Logistic regression analysis revealed that the number of functional teeth and the presence or absence of an indirect retainer were factors that significantly influenced the MP. CONCLUSIONS: An indirect retainer setting is useful for achieving good masticatory performance in mandibular bilateral distal extension dentures.

Factors Affecting Masticatory Satisfaction in Patients with Removable Partial Dentures.

(1) Background: The degree of satisfaction with dental treatment varies among patients, and the discrepancy may exist between the patient's subjective evaluation and the objective assessment. Further, the optimal methods for increasing patient satisfaction with mastication remain unclear. This study aimed to identify factors affecting masticatory satisfaction in patients with removable partial dentures. (2) Methods: A total of 132 participants (71.0 ± 9.0 years) were included. Masticatory satisfaction was assessed on a visual analog scale. An oral health survey was conducted to assess the number of functional teeth, missing tooth classification: Kennedy classification, occlusal support: Eichner classification, and removable partial dentures wearing jaw. Objective masticatory performance was assessed using gummy jelly, while subjective masticatory ability was assessed using food acceptance status and oral health-related quality of life. The associations of these factors with masticatory satisfaction were assessed. (3) Results: Masticatory satisfaction among removable partial denture wearers was not significantly associated with gender, age, denture wearing jaw, Kennedy classification, and occlusal support. The degree of masticatory satisfaction was significantly greater with higher levels of masticatory function: masticatory performance, food acceptance score, and OHIP-14 score. The OHIP-14 score was the only significant explanatory variable for masticatory satisfaction in the multiple regression analysis; the strongest associations were with the "psychological discomfort" and "physical disability" subscales (p = 0.02 and p = 0.005, respectively). (4) Conclusions: Masticatory satisfaction among removable partial denture wearers was strongly associated with oral health-related quality of life, in which the ability to eat meals comfortably with removable partial dentures is the most important determinant of masticatory satisfaction.

Higher Masticatory Performance and Higher Number of Chewing Strokes Increase Retronasal Aroma.

Mastication is a physiological process whereby food is comminuted and mixed with saliva to form a swallowable bolus; it is also the initial process for retronasal aroma that is released from foods to receptors in the nose. However, the influence of mastication state on retronasal aroma is poorly understood. The purpose of this study was to investigate the relationship between aroma concentration and factors related to mastication state. The study design was an analytical observational study. Twelve male volunteers (age, 26.5 ± 2.7 years) were recruited and divided into five and seven participants in the low and high masticatory performance groups, respectively. The stimulated salivary flow rate was measured while participants chewed paraffin wax. First, an odor sensor was placed in the nostril, and the aroma concentration was measured over time as participants chewed an orange-flavored gummy jelly standardized for masticatory performance assessment until swallowing; chewing strokes were counted to determine swallowing thresholds. Next, participants were instructed to chew the gummy jelly for a certain number of strokes (i.e., 50 or 100% of swallowing thresholds, as well as 30 strokes) and expectorate the jelly without swallowing. The surface area of comminuted jelly at 30 chewing strokes was defined as masticatory performance. Maximum and slope of aroma concentration, surface area, number of chewing strokes, and stimulated salivary flow rate were compared between low and high masticatory performance groups. Statistical significance was set at α = 0.05. At 30 chewing strokes, the maximum aroma concentration and the slope were significantly greater in the high masticatory performance group than in the low masticatory performance group. There was a positive correlation between the maximum aroma concentration and the number of chewing strokes with aroma release in both groups. No significant correlation was found between the maximum aroma concentration and the stimulated salivary flow rate. However, multiple regression analysis (with aroma concentration as a dependent variable) showed that the increase in surface area, the number of chewing strokes, and the stimulated salivary flow rate were significant explanatory variables. The results suggested that retronasal aroma was influenced by mastication state and salivary flow rate during chewing.

Can masticatory performance be predicted by using food acceptance questionnaire in elderly patients with removable dentures?

BACKGROUND: Although a food acceptance questionnaire is useful for subjective masticatory function assessments, its characteristics and limitations when applied to patients with removable dentures have been unclear. We therefore assessed the relationship between the subjective and objective masticatory function and explored whether or not a decreased masticatory function could be evaluated by food acceptance questionnaire. METHODS: One hundred and nineteen patients >60 years old with removable partial and/or complete dentures participated. Food acceptance score (FAS) was calculated by using Sato's questionnaire with 20 food items. Masticatory performance (MP) was assessed by a visual scoring method using a test gummy jelly (UHA Mikakuto). Simple/multiple regression analyses were performed to explain the objective masticatory function. The cut-off value of FAS was determined to predict a decreased masticatory function by sensitivity, specificity and receiver operating characteristics curve. RESULTS: No significant gender differences in MP or FAS were noted. Although both MP and FAS increased with the number of functional teeth, FAS was not significantly affected by age. The number of functional teeth, FAS and age had significant correlations with MP, with the number of functional teeth showing the strongest correlation. Multiple linear regression analyses identified the FAS as a significant explanatory variable for MP, and 70 was the optimal cut-off value for detecting a decreased masticatory function (MP score ≤ 2) in the diagnosis of 'oral hypofunction'. CONCLUSIONS: Using FAS to assess the MP was deemed appropriate, and a score of 70 was the optimal cut-off value for detecting a decreased masticatory function.

Factors Influencing Changes in Masticatory Performance as a Result of Wearing Removable Partial Dentures in Patients with Partially Edentulous Arches.

PURPOSE: To measure masticatory performance (MP) in partially edentulous patients when wearing removable partial dentures (RPDs) versus when not wearing RPDs, and to identify factors that could enable clinical evaluations related to differences in MP. MATERIALS AND METHODS: This study consisted of 87 partially edentulous patients (57 females, 30 males; mean age, 69.41 ± 8.85 years) categorized as Eichner classification B who habitually wore RPDs. MP was evaluated while wearing versus while not wearing RPDs using test gummy jellies. The participants were categorized into four groups by the presence of occlusal contacts in one to three of the molar and premolar regions (occlusal support), or in the anterior region only, according to the Eichner index (B1-B4). The participants were also categorized according to the jaw on which the RPDs were worn and the Kennedy classification, and evaluated in regard to changes in MP resulting from wearing RPDs. Additionally, the rate of change in MP (MP-rv) was calculated for each participant using MP when not wearing RPDs as a reference, and factors affecting MP-rv were evaluated using single or multiple regression analysis and the Kruskal-Wallis test with multiple comparisons. RESULTS: Significant increases in MP-rv were observed for all participants and for those with occlusal support in two (p = 0.006) and three regions (p = 0.019); however, no significant differences were observed when wearing and not wearing RPDs in participants with (p = 0.090) and those without occlusal support in one region (p = 0.474). With respect to the jaw on which the RPDs were worn, only maxillary or both maxillary/mandibular RPDs tended to have higher MP-rvs than did only mandibular jaws. The results of the multiple regression analysis showed that Kennedy Class I edentulous arches were a factor in increasing MP-rv (standard partial regression coefficient = 0.46, p < 0.05). CONCLUSION: According to the results of this study, among various factors on the degree of improvement in masticatory performance by wearing RPDs, bilateral missing posterior teeth might be a predictor for achieving clinical improvement.

The impact of a newly constructed removable denture on the objective and subjective masticatory function.

Purpose This study investigated the impact of the renewal of a removable prosthesis on the masticatory function by subjective and objective measures and its variation among the types of occlusal support.Methods Seventy-eight patients who received newly fabricated removable denture patients participated in this study. For the objective assessment, masticatory performance was measured using test gummy jelly. For the subjective assessment, standardized questionnaires about food acceptability and the oral health-related quality of life (OHRQoL) were used. Pre- and post-insertion assessments were performed for each subject. Subjects were divided into three groups according to their posterior occlusion: with posterior occlusion (w/PO), without posterior occlusion (w/o PO) and edentulous. Wilcoxon's signed rank test was used to compare the pre- and post-treatment measurements of each assessment. The analysis of covariance and a multiple comparison were used to assess the effect of new dentures and differences due to occlusal support.Results The masticatory performance, OHRQoL and food acceptability following prosthodontic treatment were significantly improved by new denture insertion. The masticatory performance among groups varied to a relative degree. The rate of masticatory performance improvement for edentulous subjects was twice that in w/PO subjects. The OHRQoL was significantly lower in the w/o PO and edentulous groups with old denture than patients w/PO. The food acceptability improved most markedly in the edentulous group.Conclusions The improvement in the masticatory performance by new denture insertion varied among types of occlusal support. Re-establishing the occlusal support of edentulous patients may help restore their OHRQoL and improve food acceptability.

Masticatory performance analysis using photographic image of gummy jelly.

PURPOSE: Masticatory performance can be measured through elution of glucose or beta-carotene from comminuted gummy jelly. However, these methods require special devices. Additionally, occasional/unintentional swallowing or inadequate collection of comminuted particles of gummy jelly in the oral cavity may cause measurement errors. Therefore, we devised a new photographic method to estimate the increase in surface area and weight of comminuted gummy jelly. This study aimed to verify the accuracy of this method. METHODS: Initially, fifty images depicting the comminuted pieces in a special box were prepared. Then, the increase in surface area was measured using a fully-automated method, and the weight was measured. The size and angle of each image were adjusted based on markers located at the four corners of the box. From these photographic images, the area, perimeter, color average, color deviation, side area, and amount of surface roughness for each particle was calculated, and multiple regression analysis was performed to estimate the surface area and weight. The relationship between the estimated values and the values measured with the fully-automated device and by weight were analyzed. RESULTS: The intra-class correlation coefficient between the estimated value and the value from the fully-automated method was r = 0.956. This high correlation was also obtained under different photographic conditions. Furthermore, for determining whether 80% or less gummy jelly was collected, the sensitivity was 100% and the specificity was 91%. CONCLUSIONS: The newly developed photographic method is valuable because it is accessible and may assist in achieving reliable evaluation of masticatory performance.

Coordination of tongue pressure production, hyoid movement, and suprahyoid muscle activity during squeezing of gels.

OBJECTIVE: The aim of this study was to evaluate tongue movement and its biomechanical effects during squeezing, one of the oral strategies for processing soft foods, by tongue pressure sensors, videofluorography, and surface electromyography. DESIGN: Fifteen healthy men (mean age, 31.0 ± 4.1 years) without dysphagia were recruited. A 0.1-mm-thick pressure sensor sheet with five measuring points, videofluorography, and surface electromyography were used for synchronous measurements of tongue pressure, hyoid movement, and suprahyoid muscles activity, respectively, while squeezing 5 mL of gels. Amplitude, duration, area, and their sequential order during initial squeezing were analyzed. Differences in hyoid position at the onset, peak, and offset of hyoid movement were also analyzed. RESULTS: At the beginning of initial squeezing, tongue pressure at the middle area of the hard palate, hyoid movement, and suprahyoid muscle activity appeared simultaneously, followed by tongue pressure at the anterior area and then at the posterior area. When the hyoid was in an elevated position, the amplitude of suprahyoid muscle activity and tongue pressure peaked. At the end of initial squeezing, the hyoid position at the offset of hyoid excursion was superior to that at the onset. All evaluation items of tongue pressure, hyoid movement, and suprahyoid muscle activity were modulated according to the texture of gels. CONCLUSIONS: During initial squeezing, tongue pressure, hyoid movement, and suprahyoid muscle activity were coordinated while being modulated by the food texture. At the end of initial squeezing, the hyoid was maintained in an elevated position, which might be beneficial for subsequent squeezing.

Evaluation of hyoid movement during swallowing using a bend sensor.

BACKGROUND: Movement of the hyoid and laryngeal complex is critical for preventing aspiration, as well as smooth bolus passage through the pharynx. We have developed a non-invasive system for measuring laryngeal movement during swallowing with a bend sensor and have already reported the time coordination between the signal waveform from the sensor and hyoid movement. OBJECTIVE: The aim of this study was to clarify the quantitative association between the output value of the sensor and hyoid movement during swallowing. METHODS: A small bend sensor was fixed on the skin surface along the midline of the neck of 13 healthy men (mean age, 30.8 ± 4.5 years). Laryngeal and hyoid movements during swallowing of 5 mL of water were recorded synchronously by the bend sensor and videofluorography. The relationship between the bend sensor output value (LM value) and hyoid position (x- and y-axis displacements) by videofluorography from the onset to the offset of the signal waveform was analysed for all tasks and for each task using Pearson's correlation coefficients. RESULTS: There was a positive correlation between the LM value and hyoid position for all tasks (x-axis displacement: r = .647, y-axis displacement: r = .233). In particular, there was a moderate to high correlation between the LM value and x-axis displacement for each task (.453 ≤ r ≤ .934). CONCLUSION: The LM value can be a quantitative parameter of anterior hyoid movement during swallowing that might be associated with bolus flow and upper oesophageal sphincter opening.