<prompt> Among the following varnish Which of the following has flouride concentration less than duraphat but having equivalent efficacy:DuraflourCarexFlour protector.None of the above.  <response>: Flouride varnish was first developed in Europe by Schimdt. They maintain the fluoride ions in intimate contact with enamel for longer periods. The two commonly used varnishes are Duraphat: It is the first flouride varnish and contains 22600 ppm fluoride as NaF in a neutral colophonium base NaF varnish containing 2.26 fluoride in organic lacquerFluor Protector Fluoride concentration is about 7000 ppm or 0.70Carex: Contains a lower fluoride concentration than Duraphat--1.8 fluoride and has efficacy equivalent to that of Duraphat.Duraflour - 22.6 mgml.Contains NaF in alcoholic suspension of natural resins with xylitol as sweetening agent.Cavity shield: 5 NaF in resinous base. 