Subjects A total of 150 consecutive patients were recruited from a private orthodontic clinic in Riyadh, Saudi Arabia. Participants were quasi-randomly allocated to intervention (test) and control groups based on odd and even birth dates and followed until the end of treatment (2 years). Both baseline and final data analysis included 51 participants in the test group (68% of those originally allocated to intervention; 41 females, mean age 16.2 years) and 49 participants in the control group (65% of those originally allocated to control; 32 females, mean age 16.9 years). Key Exposure/Study Factor Intervention: Modified toothbrushing technique brushing teeth after breakfast and before bedtime with toothbrush and fluoride toothpaste for 2 minutes after spreading the toothpaste on the tooth surfaces and rinsing after brushing with toothpaste slurry for 30 seconds. At follow-up, 43% of the participants in the test group were considered to have very good compliance (reported compliance to 3 to 5 out of 5 instructions received) and the remaining were considered to have good compliance (reported compliance to 1 or 2 of the instructions received). Control: Routine oral hygiene instructionsbrushing teeth after breakfast and before bedtime with toothbrush and fluoridated toothpaste and rinsing after brushing with fluoridated mouthwash. At follow-up, compliance was poor: 86% used only fluoridated toothpaste, 8% infrequently used fluoride mouthwash, and 6% used neither fluoridated toothpaste nor fluoride mouthwash. Main Outcome Measure Primary outcome-incidence of decayed and filled surfaces (DFS) based on clinical and radiographic examinations using the World Health Organization (WHO) criteria. Secondary outcomesplaque index using Silness and Loe criteria. Main Results The DFS incidence was 0.6 (SD = 2.1) for the test group and 3.5 (SD = 4.7) for the control group (P>.001). Prevented fraction was 83%. Plaque index at follow-up was 9.0 (SD = 8.0) for the test group and 11.6 (SD = 10) for the control group (P>05). Conclusions The authors concluded that, compared with routine oral hygiene instructions with fluoride toothpaste, the use of a modified fluoride toothbrushing technique significantly reduced the incidence of new carious lesions in orthodontic patients. © 2011 Elsevier Inc. All rights reserved.