Multiband Metasurface-Based Absorber for Applications in X, Ku and K Bands

A slotted-circle patch metasurface that can efficiently absorb electromagnetic (EM) waves in three different bands is proposed. Simulation results show that the proposed structure can absorb signals in three different bands, namely at 8.10 GHz, 15.39 GHz and 19.7 GHz with absorption peaks of 99.8%, 99.7% and 99.8%, respectively. The 2-mm thick absorber is electrically thin, corresponding to λ/18 at its lowest operating frequency. The absorber can be used in many applications such as anechoic chambers, scattering control, photodetectors, microbolometers and solar cells

Effect Of Whitening Dentifrices On The Superficial Roughness Of Esthetic Restorative Materials

Purpose: The purpose of this study was to investigate the surface roughness (Ra) of different esthetic restorative materials following simulated toothbrushing using different whitening dentifrices. Materials and Methods: Cylinders of Esthet-X (Dentsply Caulk, Milford, DE, USA), Durafil VS (Heraeus Kulzer, Wehrheim, Germany), and Vitremer (3M ESPE, St. Paul, MN, USA) were made using molds (4 mm in diameter for 2 mm in height). The superficial roughness was evaluated using a profilometer (Ra) with a cutoff length of 0.25 mm and a speed of 0.1 mm/s. The specimens (N = 13) were submitted to 7,500 brushing cycles using five different toothpastes: (1) Crest Regular (control; Procter & Gamble): silica abrasive (C); (2) Crest Extra Whitening (Procter & Gamble, Cincinnati, OH, USA): bicarbonate + calcium pyrophosphate (CE); (3) Dental Care A & H (Arm & Hammer, Camilla, GA, USA): bicarbonate (DC); (4) Rembrandt Plus Whitening (Oral B Laboratories, Belmont, CA, USA): carbamide peroxide + alumina/silica (RP); and (5) experimental: hydrogen peroxide + calcium carbonate (EX). Results: The data were analyzed by analysis of variance and Tukey's test (α = .05) for each restorative material, and the results [difference between final and initial roughness: Ra(F) - Ra(I) in μm] were as follows: Esthet-X: EX = 0.15 + 0.07a; RP = 0.29 + 0.16a; CE = 0.96 + 0.33b; C = 1.03 + 0.29b; DC = 1.48 + 0.37b; Durafil VS: RP = 0.09 + 0.07a; EX = 0.55 + 0.23abc; C = 0.96 + 0.26bc; CE = 1.03 + 0.33cd; DC = 1.09 + 0.37 d; and Vitremer: EX = 0.10 + 0.08a; RP = 0.26 + 0.19 a; CE = 0.94 + 0.27b; DC = 1.13 + 0.46bc; C = 1.50 + 0.32C (different letters mean differences among groups). Conclusion: It was verified that the dentifrices containing carbamide or hydrogen peroxide along with alumina + silica and calcium carbonate, respectively (groups 4 and 5), produced minor changes in Ra when compared with the control group and with those dentifrices containing bicarbonate (groups 2 and 3). ©2006 Blackwell Publishing, Inc.182102108Kleber, C.J., Putt, M.S., Nelson, B.J., In vitro tooth whitening by a sodium bicarbonate/peroxide dentifrice (1998) J Clin Dent, 9, pp. 16-21Kleber, C.J., Moore, M.H., Nelson, B.J., Laboratory assessment of tooth whitening by-sodium bicarbonate dentifrices (1998) J Clin Dent, 9, pp. 72-75Koertge, T.E., Brooks, C.N., Sarbin, A.G., A longitudinal comparison of tooth whitening resulting from dentifrice use (1998) J Clin Dent, 9, pp. 67-71Imfeld, T., Comparison of the mechanical effects of a toothbrush and standard abrasive on human and bovine dentine in vitro (2001) J Clin Dent, 2, pp. 92-106Legier-Vargas, K., Mundorff-Shrestha, S.A., Featherstone, J.D., Gwinner, L.M., Effects of sodium bicarbonate dentifrices on the levels of cariogenic bacteria in human saliva (1995) Caries Res, 29, pp. 143-147Yiu, C.K., Wei, S.H., Clinical efficacy of dentifrices in the control of calculus, plaque, and gingivitis (1993) Quintessence Int, 24, pp. 181-188De Boer, P., Duinkerke, A.S., Arenos, J., Influence of tooth paste particle size and tooth brush stiffness on dentine abrasion in vitro (1985) Caries Res, 19, pp. 232-239Pfarrer, A.M., White, D.J., Anticaries profile qualification of an improved whitening dentifrice (2001) J Clin Dent, 12, pp. 30-33Camargo, I.M., Saiki, M., Vasconcellos, M.B., Avila, D.M., Abrasiveness evaluation of silica and calcium carbonate used in the production of dentifrices (2001) J Cosmet Sci, 52, pp. 163-167Joniot, S.B., Gregoire, G.L., Auther, A.M., Roques, Y.M., Three-dimensional optical profilometry analysis of surface states obtained after finishing sequences for three composite resins (2000) Oper Dent, 25, pp. 311-315Paolantonio, M., D'Ercole, S., Perinetti, G., Clinical and microbiological effects of different restorative materials on the periodontal tissues adjacent to subgingival class V restorations (2004) J Clin Periodontol, 31, pp. 200-207Murray, I.D., Mccabe, J.F., Storere, R., Abrasivity of denture cleaning pastes in vitro (1986) Br Dent J, 161, pp. 137-141Hondrum, S.O., Fernandez Jr., R., Contouring, finishing, and polishing Class 5 restorative materials (1997) Oper Dent, 22, pp. 30-36Yap, A.U., Lye, K.W., Sau, C.W., Surface characteristics of tooth-colored restoratives polished utilizing different polishing systems (1997) Oper Dent, 22, pp. 260-265Claydon, N.C., Moran, J., Bosma, M.L., Clinical study to compare the effectiveness of a test whitening toothpaste with a commercial whitening toothpaste at inhibiting dental stain (2004) J Clin Periodontol, 31, pp. 1088-1091Neme, A.L., Frazier, K.B., Roeder, L.B., Debner, T.L., Effect of prophylactic polishing protocols on the surface roughness of esthetic restorative materials (2002) Oper Dent, 27, pp. 50-58De Menezes, M., Turssi, C.P., Hara, A.T., Abrasion of eroded root dentine brushed with different toothpastes (2004) Clin Oral Invest, 8, pp. 151-155Worschech, C.C., Rodrigues, J.A., Martins, L.R., Ambrosano, G.M., In vitro evaluation of human dental enamel surface roughness bleached with 35% carbamide peroxide and submitted to abrasive dentifrice brushing (2003) Pesqui Odontol Bras, 17, pp. 342-348Cho, L.R., Yi, Y.J., Heo, S.J., Effect of tooth brushing and thermal cycling on a surface change of ceromers finished with different methods (2002) J Oral Rehabil, 29, pp. 816-822Johannsen, G., Redmalm, G., Ryden, H., Surface changes on dental materials. The influence of two different dentifrices on surface roughness measured by laser reflexion and profilometer techniques (1989) Swed Dent J, 13, pp. 267-276Turssi, C.P., De Magalhaes, C.S., Serra, M.C., Rodrigues Jr., A.L., Surface roughness assessment of resin-based materials during brushing preceded by pH-cycling simulations (2001) Oper Dent, 26, pp. 576-584Wattanapayungkul, P., Yap, A.U., Chooi, K.W., The effect of home bleaching agents on the surface roughness of tooth-colored restoratives with time (2004) Oper Dent, 29, pp. 398-403Turker, S.B., Biskin, T., Effect of three bleaching agents on the surface properties of three different esthetic restorative materials (2003) J Prosthet Dent, 89, pp. 466-473Bailey, S.J., Swift Jr., E.J., Effects of home bleaching products on composite resins (1992) Quintessence Int, 23, pp. 489-49