The ongoing coronavirus disease 2019 (COVID-19) pandemic is of global concern and has recently emerged in the US. In this paper, we construct a stochastic variant of the SEIR model to make a quasi-worst-case scenario prediction of the COVID-19 outbreak in the US West and East Coasts. The model is then fitted to current data and implemented using Runge-Kutta methods. Our computation results predict that the number of new cases would peak around mid-April and begin to abate by July, and that the number of cases of COVID-19 might be significantly mitigated by having greater numbers of functional testing kits available for screening. The model also showed how small changes in variables can make large differences in outcomes and highlights the importance of healthcare preparedness during pandemics.

Purpose of the study: The objective of this study was to investigate the flexural strengths of five commercially available tooth-coloured restorative materials -Alpha-Dent (composite resin, Dental Technologies Inc.), Solare Anterior (composite resin, GC), F2000 (polyacid-modified composite resin, 3M), Beautifil (giomer, Shofu) and Fuji II LC (resinmodified glass ionomer cement, GC] using the ISO 4049 specifications.Materials and Method: Ten specimens of (25±0.2)mm x (2±0.1)mm x (2±0.1)mm from each material were prepared at 22-23ºC using a customized metal mould. After light polymerization, the specimens were stored in distilled water at 37ºC for 24 hours. The specimens were subsequently blotted dry, measured and subjected to flexural testing using an Instron Universal Testing Machine with a crosshead speed of 0.5mm/min. The flexural strengths were calculated from the maximum load exerted on the specimens. Data were analysed using one way ANOVA and scheffe's post-hoc multiple comparison tests at a significance level of 0.05. Results:The results showed that the mean flexural strengths of Beautifil, Solare Anterior and Alpha-Dent were above 80 MPa and those of F2000 and Fuji II LC were below 80 MPa. The results of one-way ANOVA and Scheffe's post-host tests demonstrated that Beautifil had significantly higher mean flexural strength compared to Fuji II LC, F2000 and Alpha-Dent (P<0.05). Both Solare Anterior and Alpha-Dent showed significantly higher mean flexural strengths than Fuji II LC and F2000 (P<0.05). The mean flexural strengths between Beautifil and Solare Anterior, between Alpha-Dent and Solare Anterior and between F2000 and Fuji II LC were not significantly different.Conclusions: Under the experimental conditions, Beautifil (BF) showed significantly higher mean flexural strength compared to Fuji II LC (FL), F2000 (F2) and Alpha-Dent (AD) (BF>FL, F2, AD). The mean flexural strengths of Beautifil, Solare Anterior and Alpha-Dent were above the minimum requirement of ISO 4049 for occlusal fillings (80 MPa), therefore can be used in stressbearing areas. The mean flexural strengths of Fuji II LC and F2000 did not meet the minimum requirement of ISO 4049 for occlusal fillings, therefore should not be used in stress-bearing areas.

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