This randomized controlled crossover trial conducted on 25 dental students. in the preliminary session each volunteer was given a toothbrush(Trisa, soft, Switzerland) and toothpaste(Pooneh, Iran) and Dental Floss( Mina, Iran)to use during the study, and they were instructed the proper techniques of brushing and flossing.The study was performed in two treatment sessions and a 48 hour washout period. They passed through the sessions in a randomized sequence. After prophylaxis with rubber cup, they were asked to discontinue all oral hygiene for 24 hour. At the first session , they flossed first followed by brushing (floss-brush group) and at the other session they used dental floss after brushing (brush-floss group) . At each session, before and after brushing and flossing , Dental plaque reduction was assessed using Rustogi Modified Navi Plaque Index. Interdental plaque was collected for measuring fluoride. Differences between the two groups were analyzed with mixed model test.

Inclusion Criteria:

• Dental students with 16 teeth in each jaw who had Normal salivary volume No active caries No medicine which could be affect salivary secretion No fluoride consumption in the last two weeks No Antibiotic consumption in the last 4 weeks

Exclusion Criteria:

• Any systemic diseases Periodontal diseases Crowding