Dental students' knowledge about protective guidelines for clinical practice during the COVID-19 pandemic.

Objective: The coronavirus disease 2019 (COVID-19) originated in China, in December 2019, spread worldwide promptly and turned into an outbreak which caused an international public health concern. The novel coronavirus which is also called SARS-CoV-2 transmits predominantly by respiratory droplets and the spread pattern of this infection throughout the community became a big challenge encountering the dental profession. Recently several guidelines have been developed for dental clinicians to protect both patients and practitioners, agents this infection. The aim of this study was to estimate the knowledge of dental students about the content of protective guidelines for clinical practice during the COVID-19 pandemic. Methods: An online questionnaire was developed by a team of specialists which were the faculty member of Tehran University of Medical sciences according to the content of the protective guidelines of ADA for dental practice during the COVID-19 pandemic. The questionnaire was validated and its reliability was confirmed by retesting 10 samples after 2 weeks with a cronbach alpha of 0.9. The online questionnaire was sent to 4 dental schools in the city of Tehran and was fill out by 170 dental students. Results: The mean knowledge score for all 170 participants was 16.23 out of 32 (50.72%) with the maximum score of 24 (75.0%) and the minimum score of 1 (3.1%). There was a significant relationship between the gender of participants and their knowledge score (p = 0.032) in the way that male students had significantly higher score than females. Students with more advanced educational level achieved higher knowledge scores. (p = 0.038) However, there were no significant correlation between other variables and the students' knowledge score. (p > 0.05). Conclusion: Dental students had acceptable knowledge about the general protocols against corona virus in terms of hand hygiene, wearing face masks, surface sanitization and diagnostic symptoms of a patient susceptible to be infected by corona virus. However, mostly they were not aware of the details of the guideline's items which makes it crucial to add related content in the dental students' educational curriculum.

Comparison of microleakage and shear bond strength of ribbon and twisted wire retainers bonded on human mandibular incisors with two different types of adhesives with and without primer: An in-vitro study.

BACKGROUND AND OBJECTIVES: Shear bond strength and microleakage are the success factors of fixed retainers. Recently, primer-free composites were introduced to reduce chair time. The main objectives of this study were to compare the shear bond strength (SBS) and microleakage of GC Ortho ConnectTM Flow (OF) and TransbondTM XT (TXT) with two types of common retainer wires (0.0175-inch twisted wire and 0.028×.0.008-inch ribbon dead soft wire retainers). The secondary objectives of the study were to compare enamel-adhesive interface and wire-adhesive interface microleakages. MATERIALS AND METHODS: This in vitro study was conducted on 132 human mandibular incisors (96 for bond strength and 36 for microleakage). The teeth were randomly divided into four groups for use of ribbon and twisted wires with OF and TXT adhesives. The bond strength was measured by a universal testing machine. Microleakage was evaluated by the dye penetration test using 0.05% fuchsine. Data were analysed by two-way ANOVA (alpha=0.05). RESULTS: No significant difference was noted in bond strength among the four groups (P>0.05). However, the microleakage of OF was significantly higher than that of TXT at both the enamel-adhesive and wire-adhesive interfaces (P<0.001). The microleakage at the wire-adhesive and enamel-adhesive interface was not significantly different in groups 1 and 4 and was significant in group 2 and 3. CONCLUSION: Type of adhesive significantly affected the microleakage, and OF resulted in higher microleakage than TXT at both the enamel-adhesive and wire-adhesive interfaces. Type of wire had no significant effect on microleakage. Although OF showed comparable SBS to TXT, its higher microleakage may compromise its successful long-term clinical service.

Shear Bond Strength of Self-Adhesive Composite Containing TiO2 and SiO2 Nanoparticles with an Additional Etching Step for Orthodontic Brackets Bonding to Enamel.

INTRODUCTION: Recently, nanoparticles such as nano-TiO2 have been added to some dental materials for enhancing dental carries prevention due to their antibacterial activity. AIM: This study aimed to assess the shear bond strength of a self-adhesive composite containing TiO2 and SiO2 nanoparticles for orthodontic bracket bonding. MATERIALS AND METHODS: This in vitro, experimental study was done on 70 extracted human premolars divided into 7 groups. Six groups of Vertise Flow self-adhesive composite samples were prepared: without any nanoparticles, with 0.5% and 1% TiO2 nanoparticles, 0.5% and 1% SiO2 nanoparticles, and 1% mixture of TiO2 and SiO2 nanoparticles so that nano-hybrid composites were prepared. Metal brackets were bonded with these samples as well as Transbond XT as the control group. The shear bond strength of the brackets to enamel was measured using a universal testing machine. The adhesive remnant index (ARI) score was also determined by a stereomicroscope. Data were analyzed by one-way ANOVA, Tukey's test and Kruskal-Wallis test. RESULTS: The shear bond strength of the groups was significantly different (p=0.000). Pairwise comparisons revealed that the bond strength of Transbond XT group was significantly higher than others (p<0.05), followed by the 1% TiO2 group with significant differences with Vertise Flow and 0.5% TiO2 groups. The lowest value belonged to Vertise Flow with no nanoparticles. The ARI scores was different in the control group (p=0.000). CONCLUSIONS: Adding TiO2 and SiO2 nanoparticles to Vertise Flow self-adhesive composite not only did not adversely affect its shear bond strength, but also slightly increased it. Overall, the self-adhesive nano-hybrid composite containing TiO2 and/or SiO2 nanoparticles, following an additional etching step would be acceptable for bracket bonding and can be used clinically to benefit from the antimicrobial activity of these nanoparticles.

Comparative evaluation of force decay pattern in orthodontic active tiebacks exposed to five different mouth rinses: An in vitro Study.

Background. This study compared the force decay pattern of two different orthodontic active tiebacks (ATBs) exposed to five different commercially available mouth rinses. Methods. In this in vitro study, 90 transparent ATBs and 90 gray ATBs were divided into six groups; one was the control group, and the others were exposed to one of these mouth rinses twice a day for 60 seconds: Listerine, chlorhexidine, Orthokin, Persica, and fluoride. The initial force of each ATB was 250 g at a 24-mm extension. The force of ATBs was measured on days 1, 7, 14, and 28 using a digital gauge. Results. The highest percentage of force loss was observed between days 14 and 28 (P<0.05). At the end of the study, the Persica group exhibited the highest force degradation in both ATB types. In the transparent ATBs, it was followed by Orthokin, Listerine, fluoride, chlorhexidine, and control groups, respectively. In the gray ATBs, Orthokin, chlorhexidine, control, Listerine, and fluoride groups exhibited the highest force decay in descending order. In some groups, the differences between transparent and gray ATBs were significant. In the control group, the force of transparent ATB was significantly higher than gray ones on days 7 and 14 but not significantly after four weeks. Conclusion. ATBs' force degradation could be exacerbated by the use of some mouth rinses. There were some differences between force relaxation patterns of transparent and gray ATBs. The data could be beneficial in choosing appropriate O-rings for making ATBs.