Randomization and allocation concealment
The 24 subjects were randomly allocated into two groups by block-of-4 randomization. The computer-generated randomization list was created using Microsoft Excel (version 2210, Microsoft Corp., WA, USA). The allocation sequence was concealed in a sealed opaque envelope and kept with a research secretary until the participants finished the second assigned intervention. The allocation was blinded to the outcome assessor (C.M.) as the toothbrushes were given to the participants in a separate room by the secretary. At the end of the trial, the allocation was unveiled by the data analyst (P.C.) who was not involved in the clinical examination.