Effect of shelf-storage temperature on degree of conversion and microhardness of composite restorative materials.

BACKGROUND: The pre-cure temperature is considered an important parameter that affects the polymerization kinetics and the properties of composite restoration. As dissension exists about the effect of storing composite restorative materials in refrigerator, this study aimed to assess the effect of shelf-storage temperature on degree of conversion (DC) and microhardness of three composite restorative materials with different matrix systems. METHODS: Three commercially-available composite restorative materials were used in this study; an Ormocer-based composite (Admira Fusion, Voco GmbH), a nanoceramic composite, (Ceram.X SphereTEC One, Dentsply Sirona GmbH), and a nanohybrid composite (Tetric N-Ceram, Ivoclar Vivadent AG). Regarding DC and microhardness tests, 60 disc-shaped composite specimens for each test were randomly divided into 3 groups (n = 20) according to the restorative material used. Each group was divided into 2 subgroups (n = 10) according to the composite storage temperature; stored at room temperature or stored in the refrigerator at 4°-5 °C. DC was evaluated using a Fourier-transform infrared spectrometer coupled to an attenuated total reflectance accessory. Microhardness was evaluated using micro-Vickers hardness tester under a load of 50 g with a dwell time of 10 s. The results were analyzed by ANOVA, post-hoc LSD, and independent t-tests at a significance level of p < 0.05. RESULTS: Regarding DC test all groups showed statistically significant differences at both storage temperature. The Ormocer-based composite had the highest mean values. There was a statistically significant difference between all room-stored groups and their corresponding groups stored at refrigerator (p < 0.05). For microhardness test, all groups exhibited also statistically significant differences at both storage temperatures with the Ormocer-based composite having the highest mean values. A statistically significant difference between both room-stored and refrigerator-stored groups has been observed also (p < 0.05). CONCLUSIONS: Refrigeration of resin-composite might have a deleterious effect on DC and microhardness of the tested composite restorative materials with different matrix systems. Moreover, the differences in the formulations of composite matrix have a potential impact on DC and microhardness.

Changes in Oral Health Policies and Guidelines During the COVID-19 Pandemic.

The aim of this study was to describe the changes in oral health policies and guidelines in response to the Coronavirus disease 2019 (COVID-19) pandemic in different countries and regions around the world. Information on oral health policies and guidelines from 9 countries (Canada, China including Hong Kong, Egypt, India, Japan, New Zealand, Nigeria, Switzerland, and Thailand) were summarized, and sources of the information were mostly the national or regional health authorities and/or dental council/associations. The changes made to the oral health guidelines depended on the severity of the COVID-19 pandemic. This included suspension of non-emergency dental care services at the peak of the COVID-19 outbreak, and easing the restrictions on non-essential and elective dental care when the pandemic became under control. The COVID-19 risk mitigation strategies include strict adherence to infection control practices (use of hand sanitizers, facemask and maintaining social distancing), reducing the amount of aerosol production in the dental setting, and managing the quality of air in the dental treatment rooms by reducing the use of air conditioners and improving air exchange. The COVID-19 pandemic has shown a major impact on dental practice. Dental professionals are trying to adapt to the new norms, while the medium to long-term impact of COVID-19 on dentistry needs further investigation.

Effect of chemomechanical caries removal on bonding of self-etching adhesives to caries-affected dentin.

PURPOSE: To evaluate the effect of enzyme-based (Papacárie) and sodium-hypochlorite-based (Carisolv) chemomechanical caries removal methods on bonding of self-etching adhesives to caries-affected dentin, in comparison to the standard rotary-instrument caries removal method. MATERIALS AND METHODS: Seventy-eight carious permanent molars exhibiting frank cavitation into dentin were used. Forty-eight teeth were randomly divided into three groups, according to the caries excavation methods: (i) Papacárie, (ii) Carisolv and (iii) a round steel bur. After caries removal, each group was subdivided into two groups for two-step (Clearfil SE Bond) or one-step (Clearfil S3 Bond) self-etching adhesive application and resin composite buildups. Bonded specimens were sectioned into beams for microtensile bond strength testing. Bond strength data were analyzed using three-way ANOVA and Tukey's test. For interfacial nanoleakage evaluation using a field-emission scanning electron microscope, caries was similarly removed from the remaining thirty carious molars, bonding was performed as for bond strength testing, and the teeth were sectioned. RESULTS: RESULTS of three-way ANOVA revealed that bond strength was significantly affected by "adhesive" (p<0.001) and "dentin" (p<0.001), but not "caries excavation methods" (p>0.05). The bond strength of the two-step self-etching adhesive was significantly higher than that of the one-step self-etching adhesive (p<0.001). Conversely, the bond strength of self-etching adhesives to sound dentin was significantly higher than to residual caries-affected dentin (p<0.001). Greater silver penetration was observed in the bonded interfaces of residual caries-affected dentin and in interfaces bonded with the one-step self-etching adhesive vs those bonded with the two-step self-etching adhesive. CONCLUSION: Chemomechanical caries removal did not affect the bonding of self-etching adhesives to caries-affected dentin as compared to caries excavation with rotary instruments.