Influence of chewing force on salivary stress markers as indicator of mental stress

Immediate and residual effects of functional chewing gum on sustained attention and mood

Objectives: Chewing gum has been shown to improve aspects of cognition and mood with sustained attention being particularly receptive to the effects of chewing. Chewing gum may also be a useful vehicle for administering functional ingredients. The herbal extract Rhodiola rosea and certain B-vitamins have previously been shown to improve aspects of cognition and subjective state, but their combined effects have not been studied to date.Methods: The current randomised, placebo-controlled, double-blind, balanced crossover study compared the effects of a functional gum containing Rhodiola rosea and B-vitamins to flavour-matched regular chewing gum and a flavour-matched placebo. Thirty-six healthy young participants completed measures of attention and mood at baseline, during chewing, and 1-h after chewing.Results: Chewing both functional and regular gum was shown to reduce errors on a digit vigilance task compared to placebo irrespective of whether measured during or after chewing. There were no benefits to adding functional ingredients to the gum.Discussion: Future chewing research should consider different formats of placebo. Sex differences in response to chewing and the impact of rate and intensity of chewing should also be explored.Trial registration: ClinicalTrials.gov identifier: NCT05544500.

High masticatory ability attenuates psychosocial stress: A cross-sectional study

Mastication interventions have previously been shown to alleviate acute stress. However, the relationship between masticatory performance and stress response among individuals remains unclear. This study aimed to examine the relationship between masticatory ability and stress response in young women by measuring the autonomic nerve function and salivary α-amylase activity during psychosocial stress. Eighty women (aged 20.0 ± 1.9 years) were divided into either a low or high masticatory performance group, and the Trier Social Stress Test was conducted. Moreover, the autonomic function was measured at rest, immediately before stress, immediately after stress, and 10 min after stress. The salivary α-amylase activity was also measured at rest, 5 min after stress, and 15 min after stress. The visual analog scale (VAS) was used for subjective stress evaluation. There was a significant increase in the autonomic balance of both groups immediately before stress loading, but whilst the high masticatory ability group showed a return to resting-state levels after stress loading, the low masticatory ability group showed elevated levels after stress loading. Salivary α-amylase activity significantly increased 5 min after stress loading in the low, but not high, masticatory ability group. Furthermore, the VAS scores for tension and confusion after stress were significantly higher in the low masticatory ability group than in the high masticatory ability group. Our findings suggest that high masticatory performance may contribute to alleviating psychosocial stress. This is the first study to clarify the relationship between habitual masticatory performance and psychosocial stress suppression in young women.

Stress Reduction Effects during Block-Tapping Task of Jaw in Healthy Participants: Functional Near-Infrared Spectroscopy (fNIRS) Measurements of Prefrontal Cortex Activity

The purpose of this study was to explore the influence of simple jaw opening and closing task of chewing movements on the activities of the prefrontal cortex (PFC) from the viewpoint of stress reduction. We measured cerebral blood flow (CBF) in the PFC during a block-tapping task of the jaw in healthy participants. Eleven young healthy individuals with normal dentition (7 males and 4 females, mean age 28.0 ± 3.7 years) volunteered for this study. CBF was measured using a wearable, functional near-infrared spectroscopy device. Measurements were taken using the central incisors and first molars at interocclusal distances of 5 and 10 mm. The participants were asked to bite a hard/soft block. CBF in all conditions showed limited variability or decreasing trend compared to resting state before the task. The main effect was observed for interocclusal distance (p = 0.008), and there were no significant differences for measurement area of the PFC, tooth type, and material type. An interaction was found between tooth type and material type. In conclusion, these results suggest that simple and rhythmical chewing motion has an effect of reducing CBF in the PFC and resting the PFC, which is an especially notable aspect of periodontal sensory information in the molar.

The Effects of Chewing Gum on Reducing Anxiety and Stress: A Meta-Analysis of Randomized Controlled Trials

There was currently no consensus on whether chewing gum should be widely instituted as a means to help reduce anxiety and stress. Chewing gum was also not included in guidelines for alleviating anxiety and stress. The purpose of this study was of two aspects: (1) to review the research progress of the relationship between gum chewing and anxiety and stress in recent years and (2) to make a meta-analysis of the effects of mastication on anxiety and stress. We conducted a meta-analysis of studies extracted from PubMed, the Cochrane Library, and Embase to identify randomized controlled trials (RCTs) evaluating the efficacy of chewing gum on anxiety, and stress was evaluated through screening, inclusion, data extraction, and quality assessment. The meta-analysis we performed was using Review Manager 5.3 software. We included a total of 8 RCTs, involving more than 400 adults over 18 years old. Compared with no chewing gum, chewing gum resulted in anxiety (MD = -0.26, 95% CI (-0.48, -0.04), p=0.02, I 2 = 11%), where the heterogeneity was low and statistically significant. While in stress (MD = -0.27, 95% CI (-0.79, -0.25), p=0.31, I 2 = 48%), the heterogeneity was high, and there was of no statistical significance. Based on current evidence, chewing gum is an inexpensive, well-tolerated, safe, and effective way to relieve anxiety and stress. To confirm the conclusion, we still need to conduct more randomized trials.

An efficient acute stress response in Chinese individuals with high interdependent self-construal

BACKGROUND AND OBJECTIVE

An efficient stress response comprises both quick reactivity and rapid recovery. Studies have found an enhanced stress response in Chinese people with high interdependent self-construal (ISC). ISC is a personality trait that is well-matched with Chinese collectivistic culture, and whether they exhibit an efficient stress response has not been exclusively examined.

DESIGN

We conducted a novel experiment to examine the stress response change rate in Chinese participants with varying levels of ISC，then performed a validation analysis against previous data to examine the reliability of current results.

METHODS

In our experiment, 84 healthy (42 high-ISC and 42 low-ISC), young, native Chinese were randomly assigned to either the Trier Social Stress Test (TSST), or the control condition. In the published study, 46 native Chinese participants (23 high-ISC and 23 low-ISC) had undergone the TSST. Data were collected throughout the two experiments.

RESULTS

Compared to low-ISC participants, cortisol and subjective stress levels in high-ISC participants peaked sooner and declined rapidly, suggesting quick stress reactivity and rapid recovery. This finding was supported by the previous study.

CONCLUSIONS

High-ISC individuals display an efficient stress response pattern, manifested by fast reactivity and rapid recovery, which may be adaptive in Chinese collectivistic culture.

Evaluation of Psychological Stress Marker in Partially Edentulous Indian Adults Restored with Fixed Dental Prosthesis - A Prospective Cohort Study

Background

Clinical studies have established mastication as a stress relaxation behavior in humans. Absence of teeth compromises mastication, increasing psychologic stress in individuals depicted by many physiologic changes in body. Quantitative level of psychologic stress bio-markers serve as indicators of underlying physical ailment. Lesser literatures are available in determining the role of alpha amylase stress bio marker in partially edentulous clinical situations.

Aim

The purpose of this clinical study was to evaluate the levels of salivary alpha-amylase (sAA) stress biomarker in partially edentulous subjects before and after restoration with fixed dental prosthesis.

Material and Methods

Forty partially edentulous patients with missing mandibular first molar were selected for this study. Two questionnaires, state trait anxiety inventory (STAI) and perceived stress scale (PSS) was used to evaluate stress and anxiety levels of participants. The recruited participants were treated with metal ceramic fixed dental prosthesis (FDP). A visual analog scale (VAS) was used to determine the patient satisfaction .Unstimulated salivary samples were collected preoperative, 3rd and 6th month post FDP placement. Level of sAA was estimated. Data obtained in the form of mean ± SD was subjected to statistical analysis using paired sample t-test (α=.05).

Results

The salivary alpha amylase level was highest with mean of 36.73 μM/min/mg ptn before restoration with FDP. In the third month after prosthesis placement, the enzyme values decreased to16.62 μM/min/mg ptn and least value of 8.58 μM/min/mg ptn was detected in sixth month (P < 0.05).

Conclusion

The salivary alpha amylase stress biomarker decreased after tooth replacement with FDP.

Association between Chewing Problems and Sleep among Japanese Adults

An association between physical illness and sleep has been suggested. Disordered chewing might be a physical factor that is associated with sleep issues. This cross-sectional study aimed to determine whether chewing problems are associated with sleep in Japanese adults. Sleep and chewing issues were evaluated in 6,025 community residents using a self-reported questionnaire. The prevalence of poor sleep quality and sleeping for <6 h/day (short duration) were 15.6% and 29.4%, respectively. Multivariate logistic regression analyses showed that prevalence of poor sleep quality was significantly associated with self-reported medical history (odds ratio (OR), 1.30; p < 0.001), self-reported symptoms (OR, 4.59; p < 0.001), chewing problems (OR, 1.65; p < 0.001), and poor glycemic control (OR, 1.43; p=0.035). The prevalence of short sleep duration was also significantly associated with female sex (OR, 1.23; p=0.001), self-reported symptoms (OR, 1.60; p < 0.001), chewing problems (OR, 1.30; p=0.001), and being overweight (OR, 1.41; p < 0.001). In conclusion, chewing problems were associated with poor sleep quality and short sleep duration among Japanese adults.

Interaction between stress, cytokines, and salivary cortisol in pregnant and non-pregnant women with gingivitis

OBJECTIVES

The aim of this study was to compare the effects of periodontal treatment on the inflammatory markers in gingival crevicular fluid and the concentration of salivary cortisol between non-pregnant and pregnant women with gingivitis.

MATERIALS AND METHODS

This study included 30 non-pregnant women (mean age 27.93 ± 6.61 years) and 30 pregnant women (mean age 28.93 ± 4.04 years). Each participant presented with the clinical symptoms of generalized, moderate-to-severe gingivitis. Saliva samples were collected by using the spitting method, and gingival crevicular fluid (GCF) samples were collected by using the intrasulcular method at baseline and after 3 weeks. Non-surgical periodontal treatment (NPT) comprising scaling and oral hygiene instruction was administered after sample collection. The interleukin-6 and interleukin-10 levels in GCF and salivary cortisol concentrations were determined with using enzyme-linked immunosorbent assay.

RESULTS

The pregnant women exhibited significantly deeper pockets (p < 0.05) and greater gingival inflammation (p < 0.05) than the non-pregnant women after periodontal therapy. Moreover, the levels of interleukin-6 in the GCF were significantly higher in the pregnant women compared to the non-pregnant women after periodontal therapy: 17.73 ± 9.82 pg per site and 8.08 ± 4.51 pg per site, respectively, p < 0.05. No differences in the levels of interleukin-10 were observed. The pregnant women also exhibited higher cortisol concentration in the saliva after periodontal therapy, compared to the non-pregnant women, while the levels of stress (as seen on the perceived stress scale-10) were similar in both groups.

CONCLUSIONS

Although non-surgical periodontal therapy may reduce the clinical parameters of gingivitis, increasing levels of stress in pregnancy may reduce the individual's response to it. However, further studies are necessary to substantiate these early findings.

CLINICAL RELEVANCE

Psychosocial stress may increase the risk of periodontal disease by altering the behavioral and immune responses of the individual. Therefore, the levels of stress should be taken into consideration in order to increase the efficacy of periodontal therapy in pregnant patients.

Effect of oral functional training on immunological abilities of older people: a case control study

Background

Oral functional ability decreases with age, and systemic immunological ability and quality of life can also deteriorate. Continuous moderate whole-body exercise for older people is known to improve oral functional and their immunological abilities. Here, we evaluated the effect of oral exercise as an alternative training method for highly older people who cannot perform whole-body exercises.

Methods

Unstimulated whole saliva samples had been collected for three times before training as baseline data and one time after 3 and 6 weeks of training each. Participants were instructed to conduct self-massage; their tongues were used to press their orbicularis oris muscle and buccinators, and instructed to perform bilateral massage of three major glands for facilitating saliva secretion. Medical histories, daily life habits and characteristics were also collected.

Results

Totally 30 participants (84.2 ± 8.5 years) were enrolled. In contrast to previous researches, increase in salivary Immunoglobulin A (IgA) after the training was not observed. Interestingly, hierarchical clustering analyses revealed clear individual variations as two prominent clusters and a strong positive correlation between stimulated saliva flow rate and IgA flow rate, regardless of the continuous oral functional exercise. Only body mass index (BMI) showed significant differences between the two groups (Z = 2.06, P = 0.039, Wilcoxon rank-sum test) among all collected parameters.

Conclusion

Oral functional training limitedly effects on salivary parameters of highly older people. On the other hand, BMI characterized salivary features more than any other parameters, such as the presence of diseases or medication use in these people. Trial registration: UMIN-CTR Clinical Trial UMIN000028394 on 27/July 2017, retrospectively registered.

Psychological stress-relieving effects of chewing - Relationship between masticatory function-related factors and stress-relieving effects

PURPOSE

The objective of the present study was to investigate the relationship between masticatory function-related factors (masticatory performance, occlusal contact area, maximum bite force, number of chewing strokes, and muscle activity) and the stress-relieving effects of chewing.

METHODS

A total of 28 healthy male subjects were instructed to rest or chew for 10min after 30min of stress loading with arithmetic calculations. Their stress state was assessed by measuring salivary cortisol levels. Saliva was collected at three time points: before stress loading, immediately after stress loading, and 10min after stress loading. Compared to resting, chewing produced a significantly greater reduction in the rate of change in salivary cortisol levels 10min after stress loading.

RESULTS

A negative correlation was observed between the rate of decrease in salivary cortisol levels and the number of chewing strokes. No significant correlation was observed between the rate of decrease in salivary cortisol levels and other measurement items.

CONCLUSION

In healthy dentulous people, the number of chewing strokes has been shown to be a masticatory function-related factor that affects stress relief from chewing, suggesting the possibility that more appropriate chewing would produce a greater effect psychological stress relief.

Masticatory performance alters stress relief effect of gum chewing

PURPOSE

We evaluated the effects of gum chewing on the response to psychological stress induced by a calculation task and investigated the relationship between this response and masticatory performance.

METHODS

Nineteen healthy adult volunteers without dental problems undertook the Uchida-Kraepelin (UK) test (30 min of reiterating additions of one-digit numbers). Before and immediately after the test, saliva samples were collected from the sublingual area of the participants. Three min after the UK test, the participants were made to chew flavorless gum for 3 min, and the final saliva samples were collected 10 min after the UK test. The experiment was performed without gum chewing on a different day. Masticatory performance was evaluated using color-changing chewing gum.

RESULTS

Salivary CgA levels at immediately and 10 min after the UK test were compared with and without gum chewing condition. Two-way repeated measures analysis of variance revealed significant interaction between gum chewing condition and changes in CgA levels during post 10 min UK test period. A significant correlation was found between changes in CgA levels and masticatory performance in all participants.

CONCLUSION

Our results indicate that gum chewing may relieve stress responses; however, high masticatory performance is required to achieve this effect.

Chew the Pain Away: Oral Habits to Cope with Pain and Stress and to Stimulate Cognition

The acute effects of chewing gum on cognitive performance, stress, and pain have been intensively studied in the last decade. The results have been contradicting, and replication studies proved challenging. Here, we review some of the recent findings of this topic and explore possible explanations for these discrepancies by incorporating knowledge derived from studies into oral habits and bruxism. Both stress and cerebral functional specialization (i.e., the involvement of specific brain structures in distinctive cognitive processes) are hypothesized to play a major role in the underlying physiological mechanisms of the diverse effects of chewing gum on cognition, stress, and pain.

Mastication as a Stress-Coping Behavior

Exposure to chronic stress induces various physical and mental effects that may ultimately lead to disease. Stress-related disease has become a global health problem. Mastication (chewing) is an effective behavior for coping with stress, likely due to the alterations chewing causes in the activity of the hypothalamic-pituitary-adrenal axis and autonomic nervous system. Mastication under stressful conditions attenuates stress-induced increases in plasma corticosterone and catecholamines, as well as the expression of stress-related substances, such as neurotrophic factors and nitric oxide. Further, chewing reduces stress-induced changes in central nervous system morphology, especially in the hippocampus and hypothalamus. In rodents, chewing or biting on wooden sticks during exposure to various stressors reduces stress-induced gastric ulcer formation and attenuates spatial cognitive dysfunction, anxiety-like behavior, and bone loss. In humans, some studies demonstrate that chewing gum during exposure to stress decreases plasma and salivary cortisol levels and reduces mental stress, although other studies report no such effect. Here, we discuss the neuronal mechanisms that underline the interactions between masticatory function and stress-coping behaviors in animals and humans.

Salivary mental stress proteins

Of the major diagnostic specimen types, saliva is one of the most easily collected. Many studies have focused on the evaluation of salivary proteins secreted by healthy people and patients with various diseases during responses to acute mental stress. In particular, such studies have focused on cortisol, α-amylase, chromogranin A (CgA), and immunoglobulin A (IgA) as salivary stress markers. Each of these salivary stress markers has its own strengths and weaknesses as well as data gaps related to many factors including collection technique. In this review, we summarize the critical knowledge of the positive and negative attributes and data gaps pertaining to each salivary stress marker.