Influence Of A Cobalt-chromium Metal Framework On Surface Roughness And Knoop Hardness Of Visible Light-polymerized Acrylic Resins

Although visible light-polymerized acrylic resins have been used in removable partial dentures, it is not clear whether the presence of a metal framework could interfere with their polymerization, by possibly reflecting the light and affecting important properties, such as roughness and hardness, which would consequently increase biofilm accumulation. The aim of this study was to compare the roughness and Knoop hardness of a visible light-polymerized acrylic resin and to compare these values to those of water-bath- and microwave-polymerized resins, in the presence of a metal framework. Thirty-six specimens measuring 30.0 x 4.0 ± 0.5 mm of a microwave- (Onda Cryl), a visible light- (Triad) and a water-bath-polymerized (Clássico) (control) acrylic resins containing a cobalt-chromium metal bar were prepared. After processing, specimens were ground with 360 to 1000-grit abrasive papers in a polishing machine, followed by polishing with cloths and 1-μm diamond particle suspension. Roughness was evaluated using a profilometer (Surfcorder SE 1700) and Knoop hardness (Kg/mm 2) was assayed using a microhardness tester (Shimadzu HMV 2000) at distances of 50, 100, 200, 400 and 800 μm from the metal bar. Roughness and Knoop hardness means were submitted to two-way ANOVA and compared by Tukey and Kruskal Wallis tests at a 5% significance level Statistically significant differences were found (p<0.05) for roughness and Knoop hardness, with light-polymerized resin presenting the highest values (Ra = 0.11 μm and hardness between 20.2 and 21.4 Kg/mm 2). Knoop values at different distances from the metal bar did not differ statistically (p>0.05). Within the limitations of this in vitro study, it was concluded that the presence of metal did not influence roughness and hardness values of any of the tested acrylic resins.143208212Anusavice, K.J., (2003) Philip's Science of Dental Materials. 11 th Ed., p. 96. , 11 St. Louis: Elsevier ScienceBollen, C.M.L., Lambrechts, P., Quirynen, M., Comparison of surface roughness of oral hard materials to the threshold surface roughness for bacterial plaque retention: A review of the literature (1997) Dent Mater, 13 (4), pp. 258-269Borchers, L., Tavassol, F., Tschernitschek, H., Surface quality achieved by polishing and by varnishing of temporary crown and fixed partial denture resins (1999) J Prosthet Dent, 82 (5), pp. 550-556Braun, K.O., Del Bel Cury, A.A., Cury, J.A., Use of microwave energy for processing acrylic resin near metal (1998) Braz Oral Res, 12 (2), pp. 173-180Curtis, D.A., Eggleston, T.L., Marshall, S.J., Watanabe, L.G., Shear bond strength of visible-light-cured resin relative to heat-cured resin (1989) Dental Mater, 5 (7), pp. 314-318De Clerck, J.P., Microwave polymerization of acrylic resins used in dental prosthesis (1987) J Prosthet Dent, 57 (5), pp. 650-658Khan, Z., Von Fraunhofer, J.A., Razavi, R., The staining characteristics, transverse strength, and microhardness of a visible light-cured denture base material (1987) J Prosthet Dent, 57 (3), pp. 384-386Levin, B., Sanders, J.L., Reitz, P.V., The use of microwave energy for processing acrylic resins (1989) J Prosthet Dent, 61 (3), pp. 381-383Ogle, R.E., Sorensen, S.E., Lewis, E.A., A new visible light-cured resin system applied to removable prosthodontics (1986) J Prosthet Dent, 56 (4), pp. 497-506Quirynen, M., Cml, B., Willems, G., Van Steenberghe, D., Comparison of surface characteristics of six commercially pure titanium abutments (1994) JOMI, 9 (1), pp. 71-76Reitz, P.V., Sanders, J.L., Levin, B., The curing of denture acrylic resins by microwave energy. Physical properties (1985) Quintessence Int, 6 (8), pp. 547-551Rodrigues Garcia, R.C.M., Souza Jr., J.A., Rached, R.N., Del Bel Cury, A.A., Effect of denture cleansers on the surface roughness and hardness of a microwave-cured acrylic resin and dental alloys (2004) J Prosthodont, 13 (3), pp. 1-6Rueggeberg, F.A., Goughman, W.F., Curtis Jr., J.W., Effect of light intensity and exposure duration on cure of resin composite (1994) Oper Dent, 19 (1), pp. 26-32Truong, V.T., Thomasz, F.G., Comparison of denture acrylic resins cured by boiling water and microwave energy (1988) Aust Dent J, 33 (3), pp. 201-204Ulusoy, M., Ulusoy, N., Aydin, A.K., An evaluation of polishing technique on surface roughness of acrylic rsins (1986) J Prosthetic Dent, 56 (1), pp. 107-11

Same data, different conclusions: Radical dispersion in empirical results when independent analysts operationalize and test the same hypothesis

In this crowdsourced initiative, independent analysts used the same dataset to test two hypotheses regarding the effects of scientists’ gender and professional status on verbosity during group meetings. Not only the analytic approach but also the operationalizations of key variables were left unconstrained and up to individual analysts. For instance, analysts could choose to operationalize status as job title, institutional ranking, citation counts, or some combination. To maximize transparency regarding the process by which analytic choices are made, the analysts used a platform we developed called DataExplained to justify both preferred and rejected analytic paths in real time. Analyses lacking sufficient detail, reproducible code, or with statistical errors were excluded, resulting in 29 analyses in the final sample. Researchers reported radically different analyses and dispersed empirical outcomes, in a number of cases obtaining significant effects in opposite directions for the same research question. A Boba multiverse analysis demonstrates that decisions about how to operationalize variables explain variability in outcomes above and beyond statistical choices (e.g., covariates). Subjective researcher decisions play a critical role in driving the reported empirical results, underscoring the need for open data, systematic robustness checks, and transparency regarding both analytic paths taken and not taken. Implications for organizations and leaders, whose decision making relies in part on scientific findings, consulting reports, and internal analyses by data scientists, are discussed

Study of the rare B-s(0) and B-0 decays into the pi(+) pi(-) mu(+) mu(-) final state

A search for the rare decays $B_s^0 \to \pi^+\pi^-\mu^+\mu^-$ and $B^0 \to \pi^+\pi^-\mu^+\mu^-$ is performed in a data set corresponding to an integrated luminosity of 3.0 fb$^{-1}$ collected by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5-1.3 GeV/$c^2$ and with muon pairs that do not originate from a resonance are considered. The first observation of the decay $B_s^0 \to \pi^+\pi^-\mu^+\mu^-$ and the first evidence of the decay $B^0 \to \pi^+\pi^-\mu^+\mu^-$ are obtained and the branching fractions, restricted to the dipion-mass range considered, are measured to be $\mathcal{B}(B_s^0 \to \pi^+\pi^-\mu^+\mu^-)=(8.6\pm 1.5\,({\rm stat}) \pm 0.7\,({\rm syst})\pm 0.7\,({\rm norm}))\times 10^{-8}$ and $\mathcal{B}(B^0 \to \pi^+\pi^-\mu^+\mu^-)=(2.11\pm 0.51\,({\rm stat}) \pm 0.15\,({\rm syst})\pm 0.16\,({\rm norm}) )\times 10^{-8}$, where the third uncertainty is due to the branching fraction of the decay $B^0\to J/\psi(\to \mu^+\mu^-)K^*(890)^0(\to K^+\pi^-)$, used as a normalisation.Comment: 21 pages, 3 figures, 2 Table