Nutrients Associated with Sleep Bruxism.

BACKGROUND: The purpose of the present research was to identify nutrients related to sleep bruxism and to establish a hypothesis regarding the relationship between sleep bruxism and nutrients. METHODS: We recruited 143 Japanese university students in 2021 and assigned them to sleep bruxism (n = 58) and non-sleep bruxism groups (n = 85), using an identical single-channel wearable electromyography device. To investigate nutrient intakes, participants answered a food frequency questionnaire based on food groups. We assessed differences in nutrient intakes between the sleep bruxism and non-sleep bruxism groups. RESULTS: Logistic regression modeling showed that sleep bruxism tended to be associated with dietary fiber (odds ratio, 0.91; 95% confidence interval, 0.83-1.00; p = 0.059). In addition, a subgroup analysis selecting students in the top and bottom quartiles of dietary fiber intake showed that students with sleep bruxism had a significantly lower dietary fiber intake (10.4 ± 4.6 g) than those without sleep bruxism (13.4 ± 6.1 g; p = 0.022). CONCLUSION: The present research showed that dietary fiber intake may be related to sleep bruxism. Therefore, we hypothesized that dietary fiber would improve sleep bruxism in young adults.

Ingenuity in performing replica permutation: How to order the state labels for improving sampling efficiency.

In the replica-permutation method, an advanced version of the replica-exchange method, all combinations of replicas and parameters are considered for parameter permutation, and a list of all the combinations is prepared. Here, we report that the temperature transition probability depends on how the list is created, especially in replica permutation with solute tempering (RPST). We found that the transition probabilities decrease at large replica indices when the combinations are sequentially assigned to the state labels as in the originally proposed list. To solve this problem, we propose to modify the list by randomly assigning the combinations to the state labels. We performed molecular dynamics simulations of amyloid-ß(16-22) peptides using RPST with the "randomly assigned" list (RPST-RA) and RPST with the "sequentially assigned" list (RPST-SA). The results show the decreases in the transition probabilities in RPST-SA are eliminated, and the sampling efficiency is improved in RPST-RA.

Inhibition of amyloid-ß(16-22) aggregation by polyphenols using replica permutation with solute tempering molecular dynamics simulation.

Aggregates of amyloid-ß (Aß) peptides are thought to cause Alzheimer's disease. Polyphenolic compounds are known to inhibit Aß aggregation. We applied replica permutation with solute tempering (RPST) to the system of Aß fragments, Aß(16-22), and polyphenols to elucidate the mechanism of inhibition of Aß aggregation. The RPST molecular dynamics simulations were performed for two polyphenols, myricetin (MYC) and rosmarinic acid (ROA). Two Aß fragments were distant, and the number of residues forming the intermolecular ß-sheet was reduced in the presence of MYC and ROA compared with that in the absence of polyphenols. MYC was found to interact with glutamic acid and phenylalanine of Aß fragments. These interactions induce helix structure formation of Aß fragments, making it difficult to form ß-sheet. ROA interacted with glutamic acid and lysine, which reduced the hydrophilic interaction between Aß fragments. These results indicate that these polyphenols inhibit the aggregation of Aß fragments with different mechanisms.

The Impact of Oral Health Behaviors, Health Belief Model, and Absolute Risk Aversion on the Willingness of Japanese University Students to Undergo Regular Dental Check-Ups: A Cross-Sectional Study.

Oral health behaviors, risk aversion, and the health belief model are associated with health behaviors. However, there have been few studies that investigated the association between these factors and the willingness to undergo regular dental check-ups. The purpose of this cross-sectional study was to investigate the associations between the willingness of Japanese university students to undergo regular dental check-ups and oral health behaviors, the health belief model, and absolute risk aversion. An analysis was conducted with the cooperation of questionnaire respondents (n = 748) who underwent dental check-ups at Okayama University. The students answered questionnaires on oral health behaviors, the health belief model, absolute risk aversion, and willingness to undergo regular dental check-ups. The logistic regression analysis showed significant positive associations (p < 0.05) between oral health behaviors (use of the inter-dental brush and the dental floss) and the health belief model with the willingness to undergo regular dental check-ups. However, there was no significant association with absolute risk aversion (p > 0.05). These results suggest that willingness to undergo regular dental check-ups was associated with oral health behaviors and the health belief model, but not with absolute risk aversion.

Features of the oral microbiome in Japanese elderly people with 20 or more teeth and a non-severe periodontal condition during periodontal maintenance treatment: A cross-sectional study.

Introduction: The aim of the present study was to characterize the profile and diversity of the oral microbiome of a periodontally non-severe group with ≥20 teeth in comparison with a severe periodontitis group of elderly Japanese people. Methods: A total of 50 patients who had ≥20 teeth and aged ≥60 years were recruited, and 34 participants (13 non-severe participants) were analyzed. After oral rinse (saliva after rinsing) sample collection, the V3-V4 regions of the 16S rRNA gene were sequenced to investigate microbiome composition, alpha diversity (Shannon index, Simpson index, richness, and evenness), and beta diversity using principal coordinate analysis (PCoA) based on weighted and unweighted UniFrac distances. A linear discriminant analysis effect size was calculated to identify bacterial species in the periodontally non-severe group. Results: The periodontally non-severe group showed lower alpha diversity than that of the severe periodontitis group (p <0.05); however, the beta diversities were not significantly different. A higher relative abundance of four bacterial species (Prevotella nanceiensis, Gemella sanguinis, Fusobacterium periodonticum, and Haemophilus parainfluenzae) was observed in the non-severe group than that in the severe periodontitis group. Conclusion: The oral microbiome in elderly Japanese people with ≥20 teeth and a non-severe periodontal condition was characterized by low alpha diversity and the presence of four bacterial species.

Trends in Self-Rated Oral Health and Its Associations with Oral Health Status and Oral Health Behaviors in Japanese University Students: A Cross-Sectional Study from 2011 to 2019.

Self-rated oral health (SROH) is a valid, comprehensive indicator of oral health status. The purpose of this cross-sectional study was to analyze how oral health behaviors and clinical oral status were associated with SROH and how they had changed over the course of nine years in Japanese university students. Data were obtained from 17,996 students who underwent oral examinations and completed self-questionnaires from 2011 to 2019. Oral status was assessed using the decayed and filled teeth scores, bleeding on probing (BOP), probing pocket depth, the Oral Hygiene Index-Simplified (OHI-S), oral health behaviors, and related factors. SROH improved from 2011 to 2019. The logistic regression model showed that university students who were female and had a high daily frequency of tooth brushing, no BOP, no decayed teeth, no filled teeth, and a low OHI-S score and were significantly more likely to report very good, good, or fair SROH. An interaction effect was observed between survey year and regular dental check-ups (year × regular dental check-ups). The improvement trend in SROH might be associated with changes in oral health behaviors and oral health status.

Maternal Gut Microbiome Decelerates Fetal Endochondral Bone Formation by Inducing Inflammatory Reaction.

To investigate the effect of the maternal gut microbiome on fetal endochondral bone formation, fetuses at embryonic day 18 were obtained from germ-free (GF) and specific-pathogen-free (SPF) pregnant mothers. Skeletal preparation of the fetuses' whole bodies did not show significant morphological alterations; however, micro-CT analysis of the tibiae showed a lower bone volume fraction in the SPF tibia. Primary cultured chondrocytes from fetal SPF rib cages showed a lower cell proliferation and lower accumulation of the extracellular matrix. RNA-sequencing analysis showed the induction of inflammation-associated genes such as the interleukin (IL) 17 receptor, IL 6, and immune-response genes in SPF chondrocytes. These data indicate that the maternal gut microbiome in SPF mice affects fetal embryonic endochondral ossification, possibly by changing the expression of genes related to inflammation and the immune response in fetal cartilage. The gut microbiome may modify endochondral ossification in the fetal chondrocytes passing through the placenta.

Replica permutation with solute tempering for molecular dynamics simulation and its application to the dimerization of amyloid-ß fragments.

We propose the replica permutation with solute tempering (RPST) by combining the replica-permutation method (RPM) and the replica exchange with solute tempering (REST). Temperature permutations are performed among more than two replicas in RPM, whereas temperature exchanges are performed between two replicas in the replica-exchange method (REM). The temperature transition in RPM occurs more efficiently than in REM. In REST, only the temperatures of the solute region, the solute temperatures, are exchanged to reduce the number of replicas compared to REM. Therefore, RPST is expected to be an improved method taking advantage of these methods. For comparison, we applied RPST, REST, RPM, and REM to two amyloid-ß(16-22) peptides in explicit water. We calculated the transition ratio and the number of tunneling events in the temperature space and the number of dimerization events of amyloid-ß(16-22) peptides. The results indicate that, in RPST, the number of replicas necessary for frequent random walks in the temperature and conformational spaces is reduced compared to the other three methods. In addition, we focused on the dimerization process of amyloid-ß(16-22) peptides. The RPST simulation with a relatively small number of replicas shows that the two amyloid-ß(16-22) peptides form the intermolecular antiparallel ß-bridges due to the hydrophilic side-chain contact between Lys and Glu and hydrophobic side-chain contact between Leu, Val, and Phe, which stabilizes the dimer of the peptides.

siRNA Seed Region Is Divided into Two Functionally Different Domains in RNA Interference in Response to 2'-OMe Modifications.

In RNA interference (RNAi), small interfering RNA (siRNA) functions to suppress the expression of its target mRNA with perfect sequence complementarity. In a mechanism different from above, siRNA also suppresses unintended mRNAs with partial sequence complementarities, mainly to the siRNA seed region (nucleotides 2-8). This mechanism is largely utilized by microRNAs (miRNAs) and results in siRNA-mediated off-target effects. Thus, the siRNA seed region is considered to be involved in both RNAi and off-target effects. In this study, we revealed that the impact of 2'-O-methyl (2'-OMe) modification is different according to the nucleotide positions. The 2'-OMe modifications of nucleotides 2-5 inhibited off-target effects without affecting on-target RNAi activities. In contrast, 2'-OMe modifications of nucleotides 6-8 increased both RNAi and off-target activities. The computational simulation revealed that the structural change induced by 2'-OMe modifications interrupts base pairing between siRNA and target/off-target mRNAs at nucleotides 2-5 but enhances at nucleotides 6-8. Thus, our results suggest that siRNA seed region consists of two functionally different domains in response to 2'-OMe modifications: nucleotides 2-5 are essential for avoiding off-target effects, and nucleotides 6-8 are involved in the enhancement of both RNAi and off-target activities.

Parafunctional masseter muscle activity during waking is related to periodontitis progression: A pilot prospective cohort study.

AIM: The purpose of this pilot prospective cohort study was to investigate the effects of parafunctional masseter muscle activity on periodontitis progression among patients receiving supporting periodontal therapy (SPT). MATERIALS AND METHODS: We collected data of patients treated at Okayama University Hospital from August 2014 to September 2018. The progression group was defined as patients with ≥2 teeth demonstrating a longitudinal loss of proximal attachment of ≥3 mm during the 3-year study period and/or at least one tooth extraction due to periodontitis progression. Surface electromyography of masseter muscles at baseline was continuously recorded while patients were awake and asleep. RESULTS: We analysed 48 patients (36 females) aged 66.8 ± 9.1 years (mean ± SD). The rate of parafunctional masseter muscle activity during waking hours and sleeping hours at baseline was 60.4% and 52.1%, respectively. Cox's proportional hazards regression model showed that the incidence of periodontitis progression was significantly associated with number of teeth present (p = 0.001) and parafunctional masseter muscle activity during waking hours (p = 0.041). CONCLUSION: Our results suggest that parafunctional masseter muscle activity during waking hours is a risk factor for periodontitis progression among patients receiving SPT.

Living with Family Is Directly Associated with Regular Dental Checkup and Indirectly Associated with Gingival Status among Japanese University Students: A 3-Year Cohort Study.

Although some studies showed that lifestyle was associated with oral health behavior, few studies investigated the association between household type and oral health behavior. The aim of this prospective cohort study was to investigate the association between household type, oral health behavior, and periodontal status among Japanese university students. Data were obtained from 377 students who received oral examinations and self-questionnaires in 2016 and 2019. We assessed periodontal status using the percentage of bleeding on probing (%BOP), probing pocket depth, oral hygiene status, oral health behaviors, and related factors. We used structural equation modeling to determine the association between household type, oral health behaviors, gingivitis, and periodontitis. At follow-up, 252 students did not live with their families. The mean ± standard deviation of %BOP was 35.5 ± 24.7 at baseline and 32.1 ± 25.3 at follow-up. In the final model, students living with their families were significantly more likely to receive regular dental checkup than those living alone. Regular checkup affected the decrease in calculus. The decrease in calculus affected the decrease in %BOP over 3 years. Living with family was directly associated with regular dental checkups and indirectly contributed to gingival status among Japanese university students.

Association between Household Exposure to Secondhand Smoke and Dental Caries among Japanese Young Adults: A Cross-Sectional Study.

The long-term effects of secondhand smoke (SHS) on dental caries among Japanese young adults remain unclear. The purpose of this cross-sectional study was to evaluate whether household exposure to SHS is associated with dental caries in permanent dentition among Japanese young adults. The study sample included 1905 first-year university students (age range: 18-19 years) who answered a questionnaire and participated in oral examinations. The degree of household exposure to SHS was categorized into four levels according to the SHS duration: no experience (-), past, current SHS < 10 years, and current SHS ≥ 10 years. Dental caries are expressed as the total number of decayed, missing, and filled teeth (DMFT) score. The relationships between SHS and dental caries were determined by logistic regression analysis. DMFT scores (median (25th percentile, 75th percentile)) were significantly higher in the current SHS ≥ 10 years (median: 1.0 (0.0, 3.0)) than in the SHS-(median: 0.0 (0.0, 2.0)); p = 0.001). DMFT ≥ 1 was significantly associated with SHS ≥ 10 years (adjusted odds ratio: 1.50, 95% confidence interval: 1.20-1.87, p < 0.001). Long-term exposure to SHS (≥10 years) was associated with dental caries in permanent dentition among Japanese young adults.

Relationship between oral hygiene knowledge, source of oral hygiene knowledge and oral hygiene behavior in Japanese university students: A prospective cohort study.

The aim of this prospective cohort study was to examine whether oral hygiene knowledge, and the source of that knowledge, affect oral hygiene behavior in university students in Japan. An oral exam and questionnaire survey developed to evaluate oral hygiene knowledge, the source of that knowledge, and oral hygiene behavior, such as the frequency of tooth brushing and regular dental checkups and the use of dental floss, was conducted on university student volunteers. In total, 310 students with poor tooth brushing behavior (frequency of tooth brushing per day [≤ once]), 1,963 who did not use dental floss, and 1,882 who did not receive regular dental checkup during the past year were selected. Among these students, 50, 364, and 343 in each respective category were analyzed in over the 3-year study period (follow-up rates: 16.1%, 18.5%, and 18.2%, respectively). The odds ratios (ORs) and 95% confidence intervals (CIs) for oral hygiene behavior were calculated based on oral hygiene knowledge and the source of that knowledge using logistic regression models. The results showed that dental clinics were the most common (> 50%) source of oral hygiene knowledge, and that a more frequent use of dental floss was significantly associated with dental clinics being a source of oral hygiene knowledge (OR, 4.11; 95%CI, 1.871-9.029; p < 0.001). In addition, a significant association was seen between dental clinics being a source of oral hygiene knowledge and more frequent regular dental checkups (OR, 13.626; 95%CI, 5.971-31.095; p < 0.001). These findings suggest the existence of a relationship between dental clinics being the most common source of oral hygiene knowledge and improved oral hygiene behavior in Japanese university students.

Caries Increment and Salivary Microbiome during University Life: A Prospective Cohort Study.

The purpose of this 3-year prospective cohort study was to explore the relationship between an increase in dental caries and oral microbiome among Japanese university students. We analyzed 487 students who volunteered to receive oral examinations and answer baseline (2013) and follow-up (2016) questionnaires. Of these students, salivary samples were randomly collected from 55 students at follow-up and analyzed using next-generation sequencing. Students were divided into two groups: increased group (Δdecayed, missing, and filled teeth (ΔDMFT) score increased during the 3-year period) and non-increased group (ΔDMFT did not increase). Thirteen phyla, 21 classes, 32 orders, 48 families, 72 genera, and 156 species were identified. Microbial diversity in the increased group (n = 14) was similar to that in the non-increased group (n = 41). Relative abundances of the family Prevotellaceae (p = 0.007) and genera Alloprevotella (p = 0.007) and Dialister (p = 0.039) were enriched in the increased group compared with the non-increased group. Some bacterial taxonomic clades were differentially present between the two groups. These results may contribute to the development of new dental caries prevention strategies, including the development of detection kits and enlightenment activities for these bacteria.

Association between Sleep Quality and Duration and Periodontal Disease among University Students: A Cross-Sectional Study.

The purpose of this cross-sectional study was to investigate the association between sleep quality and duration, and periodontal disease among a group of young Japanese university students. First-year students (n = 1934) at Okayama University who voluntarily underwent oral health examinations were included in the analysis. Sleep quality and duration were assessed by the Japanese version of the Pittsburgh Sleep Quality Index. Dentists examined Oral Hygiene Index-Simplified (OHI-S), probing pocket depth (PPD), and percentage of sites with bleeding on probing (BOP). Periodontal disease was defined as presence of PPD ≥ 4 mm and BOP ≥ 30%. Overall, 283 (14.6%) students had periodontal disease. Poor sleep quality was observed among 372 (19.2%) students. Mean (± standard deviation) sleep duration was 7.1 ± 1.1 (hours/night). In the logistic regression analysis, periodontal disease was significantly associated with OHI-S (odds ratio [OR]: 2.30, 95% confident interval [CI]: 1.83-2.90; p < 0.001), but not sleep quality (OR: 1.09, 95% CI: 0.79-1.53; p = 0.577) or sleep duration (OR: 0.98, CI: 0.87-1.10; p = 0.717). In conclusion, sleep quality and duration were not associated with periodontal disease among this group of young Japanese university students.

Relationship of Salivary Microbiome with the Worsening of the Periodontal Health Status in Young Adults: A 3-Year Cohort Study.

The purpose of this prospective cohort study was to investigate the influence of the salivary microbiome on the worsening of the periodontal health status among Japanese young adults. We assessed the data of systemically healthy and non-smoking young (18-22 years) university students (n = 457) from Okayama University at baseline (2013) and follow-up (2016). The worsening group was defined based on an increase in the percentage of bleeding on probing (%BOP) or an increase in probing pocket depth (PPD) from <4 mm to ≥4 mm. Unstimulated saliva samples were randomly collected from 69 students for microbiome analysis at follow-up. The salivary microbiome was assessed through 16S rRNA metagenomic sequencing. The type of community in the salivary microbiome clustered by statistical analysis and diversity was not significantly associated with the worsening of the periodontal health status in cases of increasing %BOP and PPD (p > 0.05). The prevalence of some species was significantly higher in the worsening group than in the non-worsening group (p < 0.05) in both cases. The worsening of the periodontal health status was associated with some species, but not the type of community and diversity in the salivary microbiome among Japanese young adults.

Associations between sleep bruxism, sleep quality, and exposure to secondhand smoke in Japanese young adults: a cross-sectional study.

OBJECTIVE: Sleep bruxism, a major sleep disorder that causes serious harm to oral health, is considered a multifactorial disease. Sleep bruxism can be induced by smoking, which also adversely affects sleep quality. The objective of present study was to clarify the associations between sleep bruxism, sleep quality, and exposure to secondhand smoke (SHS). METHODS: To assess the prevalence of sleep bruxism, sleep quality, and SHS exposure, we conducted oral examinations and self-report questionnaires on university students in Japan. Sleep bruxism and quality were screened using the Japanese version of the Pittsburgh Sleep Quality Index (PSQI) and the third edition of the International Classification of Sleep Disorders (ICSD-3). The inclusion criteria were adults aged between 18 and 19 years, non-smokers and non-alcohol drinkers. The exclusion criteria was failing to complete the questionnaire in full. RESULTS: We analyzed a total of 1781 Japanese young adults. Young adult females who had been exposed to SHS had worse sleep quality (p = 0.019) than those who had not. Young adult female with worse sleep quality showed a higher prevalence of sleep bruxism (p = 0.034) than those with better sleep quality. Using structural equation modeling, direct associations were identified between SHS exposure and poor sleep quality (standardized coefficients, 0.153; p = 0.008) and between sleep bruxism and poor sleep quality (standardized coefficients, 0.187; p = 0.022) in young adult females. However, no association was found among young adult males. CONCLUSION: SHS exposure is indirectly associated with sleep bruxism through poor sleep quality in Japanese young adult females.

Association between intensive health guidance focusing on eating quickly and metabolic syndrome in Japanese middle-aged citizens.

PURPOSE: The purpose of this intervention study was to investigate whether intensive health guidance focusing on eating quickly can prevent metabolic syndrome (MetS) more effectively than standard routine guidance in Japanese citizens living in rural areas. METHODS: This controlled, non-randomized, intervention study analyzed 141 participants with MetS at baseline. Participants in the intervention group received health guidance focusing on eating quickly and standard health guidance about MetS in accordance with the guidelines of the Ministry of Health, Labour and Welfare in Japan, whereas participants in the control group received only standard health guidance about MetS. The primary study outcome was the prevalence of MetS at a 1-year follow-up. RESULTS: At 1-year follow-up, the prevalence of MetS in the intervention group was significantly lower than that in the control group (p = 0.003). The decreases in body weight, body mass index, waist circumference and triglycerides from baseline to 1 year were significantly greater in the intervention group than in the control group (p < 0.05). CONCLUSION: Intensive health guidance focusing on eating quickly is more effective for improving MetS than standard Japanese health guidance alone. LEVEL OF EVIDENCE: Level II, Evidence obtained from well-designed controlled trials without randomization. TRIAL REGISTRY NAME, REGISTRATION IDENTIFICATION NUMBER, AND URL FOR THE REGISTRY: UMIN, UMIN000030600, http://www.umin.ac.jp/ctr/index-j.htm.

Awareness of Clenching and Underweight are Risk Factors for Onset of Crowding in Young Adults: A Prospective 3-Year Cohort Study.

Bruxism is a parafunctional activity that can seriously affect quality of life. Although bruxism induces many problems in the oral and maxillofacial area, whether it contributes to the onset of malocclusion remains unclear. The purpose of this prospective cohort study was to investigate the association between the onset of malocclusion and awareness of clenching during the daytime in young adults. Among 1,092 Okayama University students who underwent normal occlusion at baseline, we analysed 238 who had undergone a dental examination and had complete data after 3 years (2013⁻2016). We also performed subgroup analysis to focus on the association between awake bruxism and the onset of crowding (n = 216). Odds ratios (ORs) were calculated using multivariate logistic regression analyses. The incidences of malocclusion and crowding were 53.8% and 44.5%, respectively. In multivariate logistic regression, awareness of clenching was a risk factor for crowding (OR: 3.63; 95% confidence interval [CI]: 1.08⁻12.17). Moreover, underweight (body mass index < 18.5 kg/m²) was related to the onset of malocclusion (OR: 2.34; 95%CI: 1.11⁻4.92) and crowding (OR: 2.52, 95%CI: 1.25⁻5.76). These results suggest that awareness of clenching during the daytime and underweight are risk factors for the onset of crowding in young adults.