Relationships between chewing rate, occlusion, cephalometric anatomy, muscle activity, and masticatory performance

Association Between Dietary Variety and Masticatory Behaviors Measured Using Wearable Device Among Community-Dwelling Older Adults in Japan: A Multilevel Meal-by-Meal Analysis

Background: Consuming a variety of foods is believed to promote thorough chewing; however, it remains unclear whether individuals who consume various foods actually chew them thoroughly. Therefore, this study aimed to examine the association between dietary variety and masticatory behaviors, measured using wearable devices, among community-dwelling older adults. Methods: Participants were from the Itabashi Longitudinal Study of Aging, meeting the eligibility criteria, including the ability to exchange messages via smartphone or computer. Masticatory behaviors (number of chews, chewing duration, and speed) and meal photo data were objectively measured using an ear-worn bite sensor and its application for two or three meals per day for at least three days at home. The "modified Dietary Variety Score (m-DVS)" (range 0-10, with higher values indicating greater dietary variety) was calculated by registered dietitians. Generalized linear mixed models assessed the association between m-DVS as the exposure variable and masticatory behaviors as the outcome variable. Covariates included sociodemographic status, health behavior, health status, oral health, and oral function. Results: Five hundred and eighty-seven mealtime data entries from 63 participants were included in the analysis. The m-DVS was significantly positively associated with the number of chews (cycles, unstandardized regression coefficient = 116.5, 95% confidence interval [CI] = 85.2 to 147.8) and chewing duration (min, unstandardized regression coefficient = 1.7, 95% CI = 1.3 to 2.2). Conclusions: Consuming more varied food groups was associated with more chews and longer chewing duration among community-dwelling older adults, potentially promoting thorough chewing.

Alteration of Mastication Force via Intraoral Closed-loop Electrical Stimulation

Mastication plays an important role in effective food digestion and nutrient absorption. Therefore, regulating masticatory force in people with declining mastication function is significant for maintaining health and quality of life. In this study, we tested the effect of tactile augmentation on mastication force. To augment tactile feedback during mastication, we applied closed-loop electrical stimulation onto the mandibular vestibule using an intraoral tooth-borne electronic system. We hypothesized that closed-loop electrical stimulation, timed with mastication and applied to the nerves delivering tactile feedback to the brain, would evoke an increase in masticatory force. Experiments were completed using the intraoral system with six healthy human subjects who masticated soft and hard foods with and without stimulation during the experiment. Their mastication forces were recorded ten times per condition. The recorded mastication force profile showed that mastication force was higher with the harder food. Also, mastication force increased when electrical stimulation was applied, compared to the non-stimulated condition. These results support the hypothesis that tactile augmentation by intraoral closed-loop electrical stimulation will increase masticatory force. Other mastication parameters including period, spike width, and duty cycle are also changed by electrical stimulation. Further, stimulation left a strong aftereffect on these mastication parameters.

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.

Influence of the radius of Monson's sphere and excursive occlusal contacts on masticatory function of dentate subjects

OBJECTIVE

To determine the influence of the radius of Monson's sphere, the number of posterior laterotrusive, mediotrusive, and protrusive contacts, and the chewing rate on food comminution.

DESIGN

Sixty healthy dentate subjects, aged 21.22 ± 2.30 years, were selected. The three-dimensional coordinates of the cusp tips of the lower canine, premolar, and molar teeth were identified from the subjects' digital models. Monson's sphere was designed using the simplex method for function minimisation by adjusting the coordinates on its surface. The contacts were verified using 12 µm metal strips in jaw excursions at 0.5, 1.0, 2.0, and 3.0 mm. The masticatory performance and efficiency, swallowing threshold, and chewing rate were assessed through particle size fractionation. Data were analysed with multiple linear regression (α = 0.05).

RESULTS

The sphere's radius, laterotrusive and protrusive contacts at 0.5 mm, and chewing rate were found to be negative predictor variables for masticatory performance until 20 chewing cycles (R2 = 0.429). For 40 cycles, the radius and total contacts (0.5 mm) were also explanatory factors (R2 = 0.223). Only the radius (R2 = 0.176) and the chewing rate (R2 = 0.082) were found to be significant for 60 cycles and swallowing threshold, respectively. Masticatory efficiency was influenced by masticatory performance until 40 and 60 cycles, as well as the radius and total contacts at 2.0 and 3.0 mm (R2 = 0.958).

CONCLUSION

A larger radius of Monson's sphere and a greater number of posterior excursive contacts were found to be related to better masticatory function.

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).

Uptight responses between clenching and forearm raising with factors of visual feedback and maintenance effort in healthy young women: An experimental study on factorial design

BACKGROUND

To achieve different central preset force levels requires various fine-tuning efforts and may elicit different uptight responses. The mandibular lever system has a distinct regularity in the fine-tuning function of the upper limbs. The purpose of the present study was to detect whether the uptight responses elicited from motivating clenching differ from those induced by motivating forearm raising at different force levels.

METHODS

Twenty-five healthy females were enrolled in this study. The target was low, medium, and maximum force levels with or without visual feedback and/or maintenance effort. Surface electromyographic (SEMG) activity was recorded from the bilateral anterior temporalis and masseter or left biceps brachii muscle (BicL), and the T-Scan III System synchronously recorded the sensitive force values. The uptight responses and task difficulties were recorded for occlusal and left forearm lifting tasks using a unique visual analogue scale.

RESULTS

The highest uptight response value was achieved at a low clenching force level with visual feedback requiring no maintenance effort but at a maximum forearm-raising force level with visual feedback and maintenance effort. The SEMG activities of both jaw-closing muscles and BicL were associated with the central preset force level (P < 0.001). However, the maintenance effort only increased the jaw-closing muscles' SEMG activity at the maximal force level (P < 0.001).

CONCLUSIONS

Clenching at the central preset lower force level with visual feedback is prone to elicit a higher degree of uptight response. The constant need for a low-intensity bite can have a negative effect on an individual's mood.

Masticatory performance is influenced by masticatory muscle activity balance and the cumulative occlusal contact area

OBJECTIVE

To investigate the influence of masticatory muscle activity balance, occlusal contact area balance and the area of occlusal contact on masticatory performance in healthy dentate adults.

DESIGN

This cross-sectional study included ninety-three healthy subjects with complete dentition. Surface electromyography (sEMG) was used to record bilateral anterior temporalis activity and masseter muscle activity during maximum voluntary clenching and while chewing a test food. Seven levels of area of occlusal contact and near contact (ACNC) were registered and calculated cumulatively. The percentage overlapping coefficients were calculated for both muscle groups at maximum voluntary clenching and chewing and all levels of ACNC. Masticatory performance was measured by determining the median particle size of frankfurter sausage after 15 chewing cycles. Pearson's correlation and stepwise multiple linear regression analyses were used to assess the correlations between variables and the influence of the variables on masticatory performance, respectively, at the 0.05 level of significance.

RESULTS

Muscle balance during clenching and chewing, all near contact levels of cumulative ACNC and ACNC balance correlated negatively with median particle size (P <  0.05). The model based on stepwise multiple linear regression analysis showed muscle balance during clenching and cumulative ACNC at < 250 μm influenced median particle size.

CONCLUSION

Masticatory muscle activity balance during maximum voluntary clenching and the cumulative amount of near contact area were associated with masticatory performance, suggesting the amount of occlusal contact area-as well the balance of masticatory muscle activity-play a role in masticatory performance.

Increase in masseter muscle activity by newly fabricated complete dentures improved brain function

PURPOSE

To reveal effects of improvement of masseter muscle activity on brain function in elderly people wearing complete dentures.

METHODS

Subjects were 14 edentulous patients with a chief complaint of the inconvenience of their complete dentures. The surface electromyographic (EMG) activity of the masseter muscles was measured. Brain activities were analyzed with functional magnetic resonance imaging (fMRI), employing chewing gum as the task program. Cognitive functions were evaluated with Trail Making Test Part A (TMT-A), Rey Auditory Verbal Learning Test (RAVLT) and Rey-Osterrieth Complex Figure Test (R-OCFT). Those evaluations were performed in which subjects wore their old dentures (OD) or newly fabricated dentures (ND).

RESULTS

We compared ND condition with OD condition. The masseter muscle activity significantly increased in ND condition (p < 0.05, Wilcoxon signed rank test). The brain activity increased significantly in the superior frontal gyrus, precentral gyrus, putamen, inferior parietal lobule, cerebellum, inferior frontal lobe, and middle frontal gyrus under the ND condition than under the OD condition (p < 0.01, uncorrected, cluster size > 10 voxels). Results of TMT-A, RAVLT, and R-OCFT were also significantly improved (p < 0.05, Wilcoxon signed rank test).

CONCLUSIONS

In the edentulous elderly, the brain activity was increased following the improvement of the masseter muscle activity. Consequently, it is possible that the improvement of the masseter muscle activity might influ ence on the attention, verbal skills, and visual memory.

Relation of dietary preference to masticatory movement and masticatory exercises in Japanese children

OBJECTIVE

Modern Japanese children have decreased masticatory function, which can be explained by the dietary change to soft foods. In earlier studies involving children with mixed dentition, masticatory exercises were shown to improve masticatory function and modify dental arch growth. Grinding type of mastication with a wide path reportedly increases lateral growth of the dental arch. This study aimed to assess the relationship between masticatory movements and dietary preference, and how masticatory exercises affected masticatory movement during Hellman's dental stages IIA to IIC (period of first molar eruption).

DESIGN

In 64 Japanese pre-school children, we measured masticatory movements with foods of five different levels of hardness and investigated the dietary preference for hard foods through a questionnaire. Participants were also required to perform masticatory exercises. Masticatory movements and dietary preference for hard foods were assessed at the start (T1), conclusion (T2), and after six months of exercises (T3). Participants were allocated to Wide and Narrow groups at T1 based on their masticatory path width.

RESULTS

Baguettes and bananas resulted in the widest and narrowest masticatory paths, respectively, at T1. Results of questionnaire indicated that those eating hard foods had a broad grinding type of masticatory path. Masticatory exercises significantly widened the masticatory path in the Narrow group demonstrating that masticatory exercises help children learn to chew with grinding strokes. Moreover, the masticatory path remained stable on assessment at T3 (six-month follow-up).

CONCLUSIONS

Masticatory exercises are effective in children who are unable to grind hard foods, affecting their dietary preferences.

Individuality of masticatory performance and of masticatory muscle temporal parameters

OBJECTIVE

Mammalian mastication serves to improve intra-oral food reduction. Insufficient food reduction creates potential swallowing problems, whereas over-reduction may accelerate tooth wear and increase feeding time. Either extreme has consequences. The study's objectives were: (1) to study the relationship between food reduction, number of chews in a sequence, and chewing rate, (2) to study how controlling the number of chews and chewing rate variability affects food reduction, and (3) to assess how dentoskeletal morphological and electromyographical (EMG) characteristics impact food reduction.

DESIGN

Twenty-three healthy, fully-dentate adults chewed a standardized test food under three conditions: (1) no control, (2) number of chews controlled, and (3) number of chews and chewing rate controlled. EMG activity was sampled from masseter and temporalis muscles bilaterally. Demographic, occlusal contact area in maximum intercuspation, and cephalometric data were obtained.

RESULTS

In uncontrolled conditions, food reduction and bout duration varied more than expected across subjects. Subjects with poor reduction under controlled conditions were those with poor reduction under uncontrolled conditions. Only occlusal contact area correlated with chewing performance under uncontrolled conditions. Chewing cycle duration, EMG burst duration, and EMG peak onset latency increased when the number of chews was restricted. EMG amplitude, a surrogate for bite force, increased in tasks controlling the number of chews and chewing rate. Chewing rate variability was difficult to diminish below individual-specific levels.

CONCLUSIONS

Results: provided evidence that bite force, chewing rate, chewing performance and chewing bout duration reflected individual preferences. Future work will determine whether similar findings occur among other mammals.