Has anyone tried [[http://www.ebay.co.uk/itm/121154094332?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649 this whitening gel?]] I have used the lower strength before which is fantastic but now I want the higher strength because I need to whiten them quickly for an upcoming do. I want to know if it will cause high sensitivity.