The bacterial composition of oral samples has traditionally been determined by PCR amplicon sequencing of 16S rRNA genes. Recent amplicon sequence variant (ASV)-based analyses of 16S rRNA genes differ from that based on operational taxonomic unit (OTU) clustering in the way it deals with sequences having potential errors. However, little information is available on its application in oral microbiome studies. Here, we conducted ASV-based analysis of oral microbiome samples using QIIME 2. We investigated the optimal parameters for sequence denoising, using DADA2, and found the trimming of the first 20 nucleotides from 5′-end of both paired reads avoided excessive sequence loss during chimera removal. Truncating reads at positions 240–245 allowed the removal of low-quality sequences while maintaining sufficient length to merge matching paired ends. Taxonomic assignment, using the naïve Bayes classifier trained with the V3-V4 region of reference 16S rRNA sequences in the extended human oral microbiome database (eHOMD), resulted in bacterial compositions similar to those of OTU-based analyses. Contrary to OTU-based clustering, ASV-based analysis showed taxonomic abundance at the genus or species level to not differ significantly in tongue microbiomes, regardless of brushing. QIIME 2 can, therefore, be a standard pipeline for ASV-based analysis of oral microbiomes.

Background: Oral microbiota has been linked to both health and disease. Specifically, tongue-coating microbiota has been implicated in aspiration pneumonia and halitosis. Approaches altering one's oral microbiota have the potential to improve oral health and prevent diseases. Methods: Here, we designed a study that allows simultaneous monitoring of the salivary and tongue microbiomes during an intervention on the oral microbiota. We applied this study design to evaluate the effect of single-day use of oral care tablets on the oral microbiome of 10 healthy individuals. Tablets with or without actinidin, a protease that reduces biofilm formation in vitro, were tested. Results: Alpha diversity in the saliva was higher than that on the tongue without the intervention. The core operational taxonomic units (OTUs) common to both sites were identified. The salivary and tongue microbiomes of one individual tended to be more similar to one another than to those of other individuals. The tablets did not affect the alpha or beta diversity of the oral microbiome, nor the abundance of specific bacterial species. Conclusions: While the salivary and tongue microbiomes differ significantly in terms of bacterial composition, they show inter- rather than intra-individual diversity. A one-day usage of oral care tablets did not alter the salivary or tongue microbiomes of healthy adults. Whether the use of oral tablets for a longer period on healthy people or people with greater tongue coating accumulation shifts their oral microbiome needs to be investigated.

Background: Oral microbiota has been linked to both health and diseases. Specifically, tongue-coating microbiota has been implicated in aspiration pneumonia and halitosis. Approaches altering one's oral microbiota have the potential to improve oral health and prevent diseases. Methods: Here, we designed a study that allows simultaneous monitoring of the salivary and tongue microbiomes during an intervention on the oral microbiota. We applied this study design to evaluate the effect of single-day use of oral care tablets on the oral microbiome of 10 healthy individuals. Tablets with or without actinidin, a protease that reduces biofilm formation in vitro, were tested. Results: Alpha diversity of the tongue microbiome was significantly lower than that of the salivary microbiome, using both the number of observed amplicon sequence variants (254 ± 53 in saliva and 175 ± 37 in tongue; P = 8.9e-7, Kruskal–Wallis test) and Shannon index (6.0 ± 0.4 in saliva and 5.4 ± 0.3 in tongue; P = 2.0e-7, Kruskal–Wallis test). Fusobacterium periodonticum, Saccharibacteria sp. 352, Streptococcus oralis subsp. dentisani, Prevotella melaninogenica, Granulicatella adiacens, Campylobacter concisus, and Haemophilus parainfluenzae were the core operational taxonomic units (OTUs) common to both sites. The salivary and tongue microbiomes of one individual tended to be more similar to one another than to those of other individuals. The tablets did not affect the alpha or beta diversity of the oral microbiome, nor the abundance of specific bacterial species. Conclusions: While the salivary and tongue microbiomes differed significantly in terms of bacterial composition, they showed inter- rather than intra-individual diversity. A one-day usage of oral care tablets did not alter the salivary or tongue microbiomes of healthy adults. Whether the use of oral tablets for a longer period on healthy people or people with greater tongue coating accumulation shifts their oral microbiome needs to be investigated.

Introduction: The purpose of the present study was to clarify the relationships between the risk of malnutrition as a preliminary stage of malnutrition and overall and oral measurements for sarcopenia in older Japanese adults. Methods: Forty-five participants (79.7 ± 6.1 years) were included in the analysis. The nutrition status of the participants was assessed using the Mini Nutritional Assessment-Short Form (MNA-SF) and classified into two groups: normal and at risk of malnutrition. Overall measurements for sarcopenia in the present study were the skeletal muscle mass index, grip strength, and walking speed, while oral measurements were the cross-sectional area of the geniohyoid muscle, tongue pressure (TP), and oral diadochokinesis. Results: MNA-SF correlated with TP (r = 0.347, p = 0.019). We observed decreases of 5.7 kPa in TP and 3.9 kg/cm2 in BMI in the at risk of malnutrition group. A multiple regression analysis of parameters contributing to the risk of malnutrition identified TP as an independent variable (β = 0.913, p = 0.042). Conclusions: The present results demonstrate that the risk of malnutrition is associated with TP as an oral measurement for sarcopenia, but not overall measurements for sarcopenia. Therefore, low TP may be related with the risk of malnutrition.

AimAs the craniofacial morphology has major effects on the occurrence of obstructive sleep apnea (OSA) in Asians, factors contributing to the severity of OSA may differ depending on craniofacial characteristics. This study investigated factors affecting OSA severity in patients according to craniofacial morphological type.MethodsStudy participants comprised 227 men examined following a diagnosis of OSA between May 2017 and October 2021. We examined cephalometric X‐rays and results of polysomnography on presentation, and classified the craniofacial morphological type of the participant as “long face type” (Group L) for facial axis (Fx) angle <86° or as “short face type” (Group S) for Fx angle ≥86°. We conducted stepwise binomial logistic regression analysis with apnea‐hypopnea index (AHI) ≥ 15 events/h or AHI < 15 events/h as the dependent variable and age, body mass index (BMI), and the cephalometric parameters SNA, SNB, Fx, PNS‐P, MPT, MP‐H, SPAS, MAS, and IAS as independent variables.ResultsBMI and PNS‐P in Group S and BMI and MP‐H in Group L were identified as independent predictors of AHI ≥ 15 events/h.ConclusionsFactors affecting severity of OSA differ by craniofacial morphological type, with factors of obesity and hyoid bone position for long face‐type patients and obesity and soft palate length for short face‐type patients. Optimal treatment requires consideration of craniofacial morphology and establishment of treatment policies that take causative factors into account.