Authorship：Lead author  

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Language：English   Publishing type：Research paper (scientific journal)  

Antimicrobial mouthwash improves supragingival biofilm control when used in conjunction with mechanical removal as part of an oral hygiene routine. Mouthwash is intended to suppress bacterial adhesion during biofilm formation processes and is not aimed at mature biofilms. The most common evidence-based effects of mouthwash on the subgingival biofilm include the inhibition of biofilm accumulation and its anti-gingivitis property, followed by its cariostatic activities. There has been no significant change in the strength of the evidence over the last decade. A strategy for biofilm control that relies on the elimination of bacteria may cause a variety of side effects. The exposure of mature oral biofilms to mouthwash is associated with several possible adverse reactions, such as the emergence of resistant strains, the effects of the residual structure, enhanced pathogenicity following retarded penetration, and ecological changes to the microbiota. These concerns require further elucidation. This review aims to reconfirm the intended effects of mouthwash on oral biofilm control by summarizing systematic reviews from the last decade and to discuss the limitations of mouthwash and potential adverse reactions to its use. In the future, the strategy for oral biofilm control may shift to reducing the biofilm by detaching it or modulating its quality, rather than eliminating it, to preserve the benefits of the normal resident oral microflora.

DOI： 10.3390/antibiotics11060727

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI  

The coronavirus disease pandemic has afforded dental professionals an opportunity to reconsider infection control during treatment. We investigated the efficacy of combining extraoral high-volume evacuators (eHVEs) with preprocedural mouth rinsing in reducing aerosol contamination by ultrasonic scalers. A double-masked, two-group, crossover randomized clinical trial was conducted over eight weeks. A total of 10 healthy subjects were divided into two groups; they received 0.5% povidone-iodine (PI), essential oil (EO), or water as preprocedural rinse. Aerosols produced during ultrasonic scaling were collected from the chest area (PC), dentist's mask, dentist's chest area (DC), bracket table, and assistant's area. Bacterial contamination was assessed using colony counting and adenosine triphosphate assays. With the eHVE 10 cm away from the mouth, bacterial contamination by aerosols was negligible. With the eHVE 20 cm away, more dental aerosols containing bacteria were detected at the DC and PC. Mouth rinsing decreased viable bacterial count by 31-38% (PI) and 22-33% (EO), compared with no rinsing. The eHVE prevents bacterial contamination when close to the patient's mouth. Preprocedural mouth rinsing can reduce bacterial contamination where the eHVE is positioned away from the mouth, depending on the procedure. Combining an eHVE with preprocedural mouth rinsing can reduce bacterial contamination in dental offices.

DOI： 10.3390/ijerph19106048

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PORTFOLIO  

Silver diamine fluoride (SDF) has been long studied in laboratories, and its clinical effectiveness in the treatment and prevention of root caries has been reported. In the present study, we assessed the microbiological effects of SDF on dental biofilms grown on demineralized dentin in situ. Specifically, demineralized bovine root dentin slabs used as biofilm substrates were treated with 38% SDF, and the biofilms formed after this treatment were analyzed via real-time PCR, DEAD/LIVE cell staining, and SEM. Next, the viable cell count was determined, and microbial profiles were compared using 16S rRNA gene sequencing. Untreated slabs were used as controls. We observed significant decreases in viable cell counts (p < 0.05), number of biofilm-forming cells (p < 0.01), biofilm thickness (p < 0.01), and high proportion of dead cells with SDF treatment (p < 0.01). The microcolonies in the SDF-treated biofilms showed less complexity, and only a limited number of genera were differentially abundant between the groups. Microbial diversity index comparisons showed no significant differences between the groups with respect to treatments days (p = 0.362). Thus, SDF negatively influenced dental biofilm growth on demineralized root dentin in situ; however, its antimicrobial action did not target a specific oral taxon.

DOI： 10.1038/s41598-022-11477-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI  

We performed a comprehensive microbiome analysis of root caries lesions using 22 teeth extracted from patients with severe periodontitis. The carious lesions were mechanically collected and cryo-pulverized following tooth extraction. Differences in the microbiome were compared between independent lesions at the supragingival site (SG) and lesions extending beyond the gingival margin (GCB). DNA was extracted and the microbiome was characterized on the basis of the V3-V4 hypervariable region of the 16S rRNA gene using paired-end sequencing on an Illumina MiSeq device. The microbiota in root caries lesions showed compositionally distinct microbiota depending on the location. The most abundant OTUs in the SG group were Streptococcus (26.0%), Actinomyces (10.6%), and Prevotella (7.6%). GCB presented Prevotella (11.1%) as the most abundant genus, followed by Fusobacterium (9.6%) and Actinomyces (8.7%). The SG group showed a lack of uniformity in microbiota compared with the GCB group. The bacterial profiles of GCB varied considerably among patients, including periodontal pathogens such as Porphyromonas, Selenomonas, Filifactor, Peptococcus, and Tannerella. Periodontal pathogens inhabit root caries lesions that extend beyond the gingival margin. This study provides a new perspective for elucidating the microbial etiology of root caries.

DOI： 10.3390/microorganisms9112349

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI  

This study aimed to evaluate the anticariogenic biofilm activity of a novel zinc-containing glass ionomer cement, Caredyne Restore (CR), using a flow-cell system that reproduces Stephan responses. Streptococcus mutans biofilms were cultured on either CR or hydroxyapatite (HA) discs mounted on a modified Robbins device. The media were allowed to flow at a speed of 2 mL/min for 24 h while exposed to an acidic buffer twice for 30 min to mimic dietary uptake. Acid exposure enhanced biofilm inhibition in the CR group, which showed 2.6 log CFU/mm2 in viable cells and a 2 log copies/mL reduction in total cells compared to the untreated group after 24 h of incubation, suggesting enhanced anticariogenic activity due to the release of fluoride and zinc ions. However, there was no difference in the number of viable and total cells between the two experimental groups after 24 h of incubation in the absence of an acidic environment. The anticariogenic biofilm activity of CR occurs in acidic oral environments, for example in the transient pH drop following dietary uptake. CR restorations are recommended in patients at high risk of caries due to hyposalivation, difficulty brushing, and frequent sugar intake.

DOI： 10.3390/antibiotics10080977

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Oral biofilms are associated with caries, periodontal diseases, and systemic diseases. Generally, antimicrobial therapy is used as the first line of treatment for infectious diseases; however, bacteria in biofilms eventually develop antibiotic resistance. This study aimed to apply our in situ biofilm model to verify whether an arginine preparation is useful for plaque control. Ten healthy subjects who did not show signs of caries, gingivitis, or periodontitis were recruited. The dental biofilms from the subjects were obtained using our oral device before and after gargling with arginine solution for 4 weeks. We found that 8% arginine solution significantly increased the concentration of ammonium ions (NH4+) in vitro and in vivo in saliva (p &lt; 0.05) and decreased the proportions of the genera Atopobium and Catonella in vivo. However, the viable count was unaffected by the mouthwash. Further, oral populations of the genera Streptococcus and Neisseria tended to increase with the use of arginine. Therefore, we concluded that using an 8% arginine solution decreased the NH4+ concentration in the oral cavity without affecting the number of viable bacteria, and that the diversity of oral bacterial flora changed. We suggest that arginine might help prevent mature biofilm formation.

DOI： 10.3390/pharmacy9010018

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PORTFOLIO  

Dental biofilm present on the tooth surface is associated with oral diseases, such as dental caries and periodontal disease. Because bacterial numbers rapidly increase in saliva during sleep, oral care before sleeping is recommended for the prevention of chronic oral diseases. However, temporal circadian changes in the quantity and quality of dental biofilms are poorly understood. This study aimed to investigate the impacts of sleeping on dental biofilm amounts and compositions by using an in situ model. The use of this in situ model enabled us to investigate dental biofilm formed in the oral cavity and to perform a quantitative analysis. Subjects began wearing oral splints in the morning or before sleeping, and biofilm samples were collected at 8, 16, and 24 h after the subjects began wearing oral splints; these samples were then used in various experiments. No significant changes in the numbers of biofilm-forming bacteria were caused by sleep. However, the relative abundances of genera related to periodontitis (i.e., Fusobacterium and Prevotella) increased after awakening. In conclusion, the numbers of biofilm-forming bacteria were not affected by sleep, and the abundances of obligate anaerobes increased after sleep. This research may aid in defining efficacious preventive oral care.

DOI： 10.1038/s41598-020-80541-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

Dysbiosis of the oral microbiome is associated with diseases such as periodontitis and dental caries. Because the bacterial counts in saliva increase markedly during sleep, it is broadly accepted that the mouth should be cleaned before sleep to help prevent these diseases. However, this practice does not consider oral biofilms, including the dental biofilm. This study aimed to investigate sleep-related changes in the microbiome of oral biofilms by using 16S rRNA gene sequence analysis. Two experimental schedules-post-sleep and pre-sleep biofilm collection-were applied to 10 healthy subjects. Subjects had their teeth and oral mucosa professionally cleaned 7 days and 24 h before sample collection. Samples were collected from several locations in the oral cavity: the buccal mucosa, hard palate, tongue dorsum, gingival mucosa, tooth surface, and saliva. Prevotella and Corynebacterium had higher relative abundance on awakening than before sleep in all locations of the oral cavity, whereas fluctuations in Rothia levels differed depending on location. The microbiome in different locations in the oral cavity is affected by sleep, and changes in the microbiome composition depend on characteristics of the surfaces on which oral biofilms form.

DOI： 10.1371/journal.pone.0259850

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Language：Japanese   Publisher：The Japanese Society of Conservative Dentistry  

<p> Purpose: Nickel-titanium (NiTi) rotary files are becoming more popular and an important part of the equipment for root canal treatment. The superelasticity and shape memory of the instruments have improved the shaping procedures in root canal preparation, making it easier and faster. In this study, we assessed the educational effectiveness of J- and S-shaped root canal preparation with FKG Race in dental students' hands-on practical classes.</p><p> Methods: Fifty-six third-year students in the School of Dentistry, Osaka University performed J- and S-shaped root canal preparation in transparent epoxy resin blocks with FKG Race twice each. After penetration with a #15 K-file, root canal length was measured. Cervical preflaring and glide path preparation were performed with PreRace and #15 K-file, respectively. Then, the working length was determined by subtracting 1 mm from the root canal length. Root canal preparation was performed with Race (#30/6%, #30/4%, #25/4%, and #20/4%) in order and the final preparation was carried out with #30/6%. In order to evaluate the quality of root canal preparation, we photographed the epoxy resin blocks before and after the instrumentation by micro-computed tomography and measured the root canal width perpendicular to the long axis of the root canal at 1, 2, 3, 4, 5, and 6 mm from the root apex. The increase in root canal width and the time for preparation were compared between the students and specialists certified by the Japanese Society of Conservative Dentistry.</p><p> Results: In the J-shaped root canal preparation by the students for the first time, 62.5% of the students had apical perforation and 5.4% had ledge formation. In the second-time preparation of the J-shaped root canal, 30.4% of the students had apical perforation, 3.6% had separated files, and 3.6% had ledge formation. In the S-shaped root canal preparation by the students for the first time, 23.2% of the students had apical perforation and 7.1% had separated file. In the second-time preparation of the S-shaped root canal, separated file occurred in 7.1%. In terms of speed of root canal preparation, the second try at S-shaped preparation by the students was significantly faster than the first try. The distances between pre- and post-instrumentation at the different levels showed no significant differences among the first and second trials by the students and specialists.</p><p> Conclusion: In the practice of curved-root canal preparation using NiTi files, students can quickly and accurately achieve successful preparation even for difficult S-shaped root canals, especially by paying attention when preparing a root apex.</p>

DOI： 10.11471/shikahozon.62.263

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Language：Japanese   Publisher：The Japanese Society of Conservative Dentistry  

<p> Purpose: Nickel-titanium (NiTi) files are becoming more popular for root canal treatments, since they have the clear advantage of maintaining the original shape of curved root canals because of their low elastic modulus and flexibility. The present study assessed the educational effectiveness of preparing curved root canals with FKG RaCe in dental students' hands-on practical classes.</p><p> Methods: A total of 49 third-year students in the School of Dentistry, Osaka University performed root canal preparation of J-shaped canals in transparent epoxy resin blocks with FKG RaCe twice. After measuring the length of root canals with a #15 K file, cervical preflaring was performed with a preRaCe and glide path preparation was performed with a #15 K file. Working length was determined by subtracting 1 mm from the root canal length and root canal preparation was performed with RaCe (#30/6%, #30/4%, #25/4%, and #20/4%). For evaluating the quality of root canal preparation, digital images of the epoxy resin blocks before and after the instrumentation were captured by micro-computed tomography. Using image analysis software, the images of pre- and post-instrumentation were superimposed and the distances between pre- and post-instrumentation were measured on both the inner and outer sides. Measuring levels were set at 1, 2, 3, 5, 7 and 10 mm from the root apex and the distances were compared between the outcomes by the students and by specialists accredited by the Japanese Society of Conservative Dentistry.</p><p> Results: In 49 root canals instrumented by the students for the first time, 28 apical perforations, one separated file, and one apical blockage were observed. In 49 root canals instrumented by the students for the second time, five apical perforations and one apical blockage were observed. The distances between pre- and post-instrumentation at the different levels and working time showed no significant differences among the first and second trials by the students and specialists.</p><p> Conclusion: In hands-on training of root canal preparation for dental students, successful root canal preparation was achieved by instructing students to pay attention especially when preparing a root apex.</p>

DOI： 10.11471/shikahozon.60.255

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

We previously characterized RNA polymerase II-associated protein 3 (RPAP3) as a cell death enhancer. Here we report the identification and characterization of splicing isoform of RPAP3, isoform 1 and 2. We investigated the interaction between RPAP3 and PIH1 domain containing protein 1 (PIH1D1), and found that RPAP3 isoform 1, but not isoform 2, interacted with PIH1D1. Furthermore, knockdown of RPAP3 isoform 1 by small interfering RNA down-regulated PIH1D1 protein level without affecting PIH1D1 mRNA. RPAP3 isoform 2 potentiated doxorubicin-induced cell death in human breast cancer T-47 cells although isoform 1 showed no effect. These results suggest that R2TP complex is composed of RPAP3 isoform 1 for its stabilization, and that RPAP3 isoform 2 may have a dominant negative effect on the survival potency of R2TP complex.

DOI： 10.1016/j.bbrc.2012.11.017

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

J-GLOBAL

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J-GLOBAL

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Language：Japanese   Publisher：日本歯内療法学会  

J-GLOBAL

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Language：Japanese  

J-GLOBAL

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Language：Japanese   Publisher：(NPO)日本歯周病学会  

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J-GLOBAL

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J-GLOBAL

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Language：Japanese   Publisher：(公社)日本薬理学会  

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