The study assessed 25 participants, who were asked to brush their teeth first, then use dental floss to clean the spaces between their teeth (brush-floss). In the second phase the same group was asked to floss first, then brush their teeth (floss-brush). Researchers discovered that the ammount of dental plaque between the teeth and on the mouth was significantly reduced using the floss-brush approach.
Plaque and bacteria in it, are the primary casue of periodontal disease, an inflammatory conditions which occurs when bacteria accumulate blowe the gumline, destroying the attachment of the tooth to the bone and gum. The researchers contend that as flossing first loosens bacteria and plaque between the teeth and from under the gum, brushing afterward further clears bacteria from the mouth.