Objective: Effective control of dental plaque by daily brushing is critical for the prevention and treatment of periodontal disease. Recently, not only manual toothbrushes but also many types of sonic powered toothbrush have been developed.

 Materials and Method: The aim of this study was to investigate the dental plaque removal effect and safety of SOLADEY RHYTHM 2 (Shiken Co., Ltd.), which has more solar panels than the conventional types already developed by Shiken Co., Ltd., to reinforce the effect of the titanium dioxide electrode.

 Results: SOLADEY RHYTHM 2 has a high oral hygiene effect regardless of the kind of tooth and surface, and a high rate of dental plaque removal at interproximal or cervical surfaces in particular was observed.

 Conclusion: It is suggested that the sonic powered toothbrush with titanium dioxide electrode and solar panels has high dental plaque removal efficacy, and is effective for plaque control for preventing dental caries and periodontal disease.

 Purpose: In composite resin restoration, universal adhesives have become popular due to their broad applicability in various clinical situations. The clinical success of adhesive systems depends not only on material-related but also on operator-related factors. The purpose of this study was to evaluate the dentin bond strength of two adhesive systems performed by operators with or without clinical experience.

 Methods: Two types of adhesive system, a two-step self-etch adhesive, Clearfil Mega Bond 2 (MB2), and a 1-bottle universal adhesive, Clearfil Universal Bond Quick (UBQ), were used in this study. The operators were five undergraduate dental students with no clinical experience at all (undergraduates) and five dentists with extensive experience in adhesive dentistry (mean experience of 7.4 years) (professionals). Forty bovine dentin surfaces were prepared with #600-grit SiC paper under running water. MB2 or UBQ was applied to the dentin surfaces and light-cured according to the manufacturer’s instructions, followed by 2-mm composite buildups by each operator. The specimens were sectioned and subjected to a microtensile bond strength (μTBS) test after being stored in water for 24 h. The data were statistically analyzed by two-way ANOVA and t-test (p=0.05). Weibull analysis was also performed on the μTBS data.

 Results: The mean μTBSs in MPa/Weibull modulus value were MB2-undergraduate: 33.7/3.6, MB2-professionals: 36.7/4.2, UBQ-undergraduate: 26.0/2.0, and UBQ-professionals: 28.1/2.6. Two-way ANOVA revealed that “adhesive system” influenced μTBS (p<0.05), while “operator” did not (p>0.05). The Weibull modulus of each group was significantly different (p<0.05).

 Conclusion: MB2 is superior to UBQ in terms of dentin bond strength and bonding reliability. The practitioner’s clinical experience does not affect the dentin bond strengths of both MB2 and UBQ. Professionals attained superior bonding reliability of both MB2 and UBQ compared with undergraduates.

 Purpose: The purpose of this study was to determine the influence of a tooth conditioner containing phosphoric acid ester monomer on the bond performance of a resin-based luting cement to saliva contaminated surfaces based on shear bond strength (SBS) tests and surface free energy (SFE) measurements.

 Materials and Methods: Three conditioners for saliva contaminated tooth surfaces were used: Katana Cleaner (KC, Kuraray Noritake Dental), Ultra-Etch (UE, Ultradent Products), and Multi Etchant (ME, Yamakin). Panavia V5 (Kuraray Noritake Dental) was used as a resin-based luting agent. Bovine enamel and dentin surfaces were ground with SiC papers, ending at #320 grit. For saliva contaminated tooth surfaces, 10 μl of human saliva was applied to the ground surface. Uncontaminated tooth surfaces were set as a control group. The saliva contaminated specimens were divided into four groups, treated with the different conditioners described above (KC, UE, and ME group) or without any treatment (SC group). A stainless-steel metal ring was placed over the bonding area, and the luting agent was condensed into the ring and light irradiated. The assembled specimens were stored in 37°C water for 24 h. Half of the specimens in each group were subjected to thermal cycling (TC) 10,000 times between 5 and 55°C, with a dwell time of 30 s. The other half of the specimens in each group formed a baseline group. SBS tests were conducted after each storage condition. For SFE determinations, specimens were prepared as for the SBS tests. The contact angles of three test liquids that have known SFE parameters were measured using a contact angle meter. In addition, SEM observations were performed of surfaces treated with the three different conditioners after saliva contamination.

 Results: In the baseline groups, although the SC groups showed a significantly lower SBS value than the control groups in both enamel and dentin, the conditioner treated groups showed higher SBS values than the SC groups. In the TC groups, UE showed a significantly higher enamel SBS than the other groups, but KC showed a significantly higher dentin SBS than the other groups. Although the SC groups showed significantly lower SFEs than the control groups in both enamel and dentin, the SFEs after conditioner treatment were material dependent.

 Conclusion: After salival contamination of tooth surfaces, the conditioners tested might be useful in enhancing the bond performance of the resin-based luting cement due to modification of the contaminated tooth surfaces. The SFEs of treated surfaces differed with different conditioners depending on their conditioning mechanisms.

 Purpose: Prevention of SARS-CoV-2 infection is crucial for overcoming the COVID-19 epidemic. Therefore, it is necessary to take new precautionary measures in addition to disinfecting hands and wearing personal protective equipment (PPE). One of the candidates for prevention is the use of catechins, particularly epigallocatechin-3-Ο-gallate (EGCG). It has been reported that EGCG selectively binds to the spike protein of SARS-CoV-2 by the molecular docking method, which may inhibit the binding of the spike protein to angiotensin converting enzyme-2 (ACE2). The purpose of this study was to investigate whether each of EGCG alone, a mixture of four kinds of catechins, or green tea effectively inhibited the binding of the SARS-CoV-2 spike protein to ACE2.

 Materials and Methods: Catechins in different states (EGCG, four types of mixed catechins, powdered green tea) were used in this study. The effects of EGCG solution (EGCG) and four kinds of mixed catechins solution (4 KC) were examined at three different concentrations (1, 10 and 100 mg/ml), and two types of green tea solution, Ⅰ (PWA) and Ⅱ (PWB), at two different concentrations (1 and 10 mg/ml) were adopted. A screening kit for SARS-CoV-2 spike protein inhibition was used and the reaction was developed with a tetramethylbenzidine (TMB) substrate. Thereafter, the coloring reaction was photographed and inhibitory level was measured by ELISA.

 Results and Discussion: The inhibitory effect of ACE2 binding to SARS-CoV-2 spike protein was the strongest at high concentration in each solution, and the inhibitory effect decreased in proportion to the decrease of concentration. The percentages of inhibitory effect ranged from 12 to 89% for EGCG, from 11 to 88% for 4 KC, from 10 to 47% for PWA, and from 11 to 47% for PWB. In the present study, it was found that four kinds of catechins mixed solution and green tea solution inhibited binding of the spike protein to ACE2 the same as the EGCG solution, and that the inhibitory effect of each solution depended on the concentration.

 Conclusion: This study showed that not only EGCG, but also the mixture of four kinds of catechins and the powdered green tea effectively inhibited the binding of SARS-CoV-2 spike protein depending on the concentration. Catechins are expected to serve as a new way to prevent SARS-CoV-2 infection.