Evaluation of the cumulative effect of photodynamic therapy and local fluoride on the microhardness and topography of demineralized enamel and cementum surfaces.

Background: The present study aimed to determine the cumulative effect of two photodynamic therapy methods with methylene blue and indocyanine green and two topical fluoride therapy methods with fluoride varnish and silver diamine fluoride alone and in combination on the microhardness and topography of demineralized enamel and cementum surfaces. Materials and methods: Seventy-two sound human teeth were selected, and their buccal and lingual surfaces were assigned to two main groups of enamel and cementum using simple randomization. The initial surface hardness (SH) of the enamel and cementum in each sample was determined using a micro-Vickers hardness tester using a 200-g force in 10 s. Then artificial caries was induced by immersion in a demineralizing/remineralizing solution (i.e., each tooth provided two samples, one on the buccal aspect and the other on the lingual aspect). Each enamel/cementum main group was divided into two subgroups using simple randomization based on the local fluoride type (fluoride varnish and silver diamine fluoride) and the type of the photosensitizer agent (methylene blue and indocyanine green). Finally, 16 groups were achieved (n = 9). The final surface hardness of the enamel and cementum samples was determined as described above. Finally, the sample surfaces were prepared for the surface topography evaluation under a scanning electron microscope. The baseline microhardness was compared between the 16 study groups in the first step using one-way ANOVA. Then, three-way ANOVA was used to evaluate the effect of fluoride, laser, and surface (enamel and cementum) on microhardness. Results: All the groups exhibited decreased microhardness due to the induction of artificial caries. In both main groups of enamel and cementum, the lowest decrease in microhardness was recorded with combined photodynamic therapy and methylene blue photosensitizer material and fluoride varnish (15.1 % for cementum and 16.7 % for enamel), and the highest decrease in microhardness was recorded in the methylene blue group (35.7 % for cementum and 34.9 % for enamel). Conclusion: The combination of photodynamic therapy with the photosensitizer substance methylene blue or indocyanine green together with fluoride varnish or silver diamine fluoride is effective on the remineralization of demineralized enamel and cementum. Although there is no difference between the combination of photodynamic therapy with fluoride varnish compared to fluoride varnish alone, both of these treatments are more effective than using photodynamic therapy alone.

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.

Effect of Pre-heating on Microtensile Bond Strength of Composite Resin to Dentin.

OBJECTIVE: Direct composite resin restorations are widely used and the impact of different storage temperatures on composites is not well understood. The purpose of this study was to evaluate the microtensile bond strength of composite to dentin after different pre-curing temperatures. MATERIALS AND METHODS: Occlusal surfaces of 44 human molars were ground with diamond burs under water coolant and polished with 600 grit silicon carbide papers to obtain flat dentin surfaces. The dentin was etched with 37% phosphoric acid and bonded with Adper Single Bond 2 according to the manufacturer's instructions. The specimens were randomly divided into two groups (n=22) according to the composite resin applied: FiltekP60 and Filtek Z250. Each group included three subgroups of composite resin pre-curing temperatures (4°C, 23°C and 37°C). Composite resins were applied to the dentin surfaces in a plastic mold (8mm in diameter and 4mm in length) incrementally and cured. Twenty-two composite-to-dentin hour-glass sticks with one mm(2) cross-sectional area per group were prepared. Microtensile bond strength measurements were made using a universal testing machine at a crosshead speed of one mm/min. For statistical analysis, t-test, one-way and two-way ANOVA were used. The level of significance was set at P<0.05. RESULTS: Filtek P60 pre-heated at 37ºC had significantly higher microtensile bond strength than Filtek Z250 under the same condition. The microtensile bond strengths were not significantly different at 4ºC, 23ºC and 37ºC subgroups of each composite resin group. CONCLUSION: Filtek P60 and Filtek Z250 did not have significantly different microtensile bond strengths at 4ºC and 23ºC but Filtek P60 had significantly higher microtensile bond strength at 37 ºC. Composite and temperature interactions had significant effects on the bond strength.

Comparing the Disinfecting Efficacies of Micro 10, Deconex, Alprocid and Microzid AF on the Microorganisms on Radiographic Equipments.

BACKGROUND AND AIMS: The exposure and processing of dental radiographs are not routinely associated with the spatter of blood or saliva; however, infection control is still an issue resulting from contaminated equipment, supplies, film packets or cassettes. This study aimed at comparing the efficacy of four commercially available disinfectants on microorganisms present on the equipment of radiology department. MATERIALS AND METHODS: Samples from twelve sites of the radiology department were collected using a sterile swab smeared with normal saline, which was then dipped in a test tube. Experimental surfaces were then disinfected by the spray-wipe-spray method using one of Micro 10, Deconex, Alprocid or Microzid AF disinfectants, followed by resampling. The samples were subsequently cultured on blood agar and EMB plates and the colonies were counted. Isolates were identified by biochemical tests. For statistical analysis, Wilcoxon signed ranks test, Kruskal-Wallis, Chi-square and Fisher exact tests were used. RESULTS: Staphylococcus aureus and coagulase-negative staphylococci had the highest and Lactobacillus spp. had the lowest prevalence before disinfection. There were significant differences between the cfu/mL of bacteria before and after disinfection with any of the four disinfectant solutions. There was a significant difference between efficacy of Deconex and Alprocid (P = 0.014), Deconex and Microzid AF (P = 0.001), and Deconex and Micro 10 (P = 0.001). CONCLUSION: According to the results, Deconex has the highest disinfectant efficacy compared to other solutions.