Randomization and blinding
BLIND
Patients who met the inclusion criteria were randomized in a 1:1:1:1 ratio by a permuted block randomization method to one of the following groups: (1) zinc sulfate, (2) polyherbal, (3) CHX, or (4) placebo. So, blocks of four were applied and six-digit random numbers were generated. Patients were assigned to each of study group based on Random Number Table. To keep the concealment, the allocation list was given to a third person not involvedin the study.To keep blinding, the mouthwashes were filled in identical bottles and coded by the principal investigator. Patients, radiation oncologist and investigator of clinical responses were all blind to the four arms of the study. When the weekly follow-up sessions were completed, the principal investigator decoded the random numbers of consumed bottles and assigned each to the proper arm.