Thirty-eight subjects diagnosed with BMS according to the International Association for the Study of Pain guidelines were randomized to either placebo ( 5 % sodium carboxymethylcellulose , 0.15 % methyl paraben , and 10 % glycerol in distilled water qsp 100 g ) or treatment ( urea 10 % ) to be applied to the oral cavity 3-4 times per day for 3 months .