In each patient for whom premolar extractions were planned ( n = 22 ) , 1 premolar was randomly chosen as the experimental tooth for the application of the fluoride delivery system ( Opal Seal ; Ultradent Products , South Jordan , Utah ) , and the contralateral tooth was assigned as the control to receive the standard treatment ( Transbond XT ; 3M Unitek , Monrovia , Calif ) .