An experienced dental hygienist can complete a complete full mouth fluoride varnish application in about one minute. Treatment time variables include: patient acceptance (squirminess) and type of applicator brush or delivery system used. The viscosity of the varnish material can also affect the application time. In most all cases though, it’s only a minute or two in the worstAn experienced dental hygienist can complete a complete full mouth fluoride varnish application in about one minute. Treatment time variables include: patient acceptance (squirminess) and type of applicator brush or delivery system used. The viscosity of the varnish material can also affect the application time. In most all cases though, it’s only a minute or two in the worst case. case.