Regular tooth brushing is important to remove plaque and food debris, and most importantly for distributing the fluoridated toothpaste.
Chestnutt IG, Schafer F, Jacobson AP, Stephen KW. The influence of tooth brushing frequency and post-brushing rinsing on caries experience in a caries clinical trial. Community Dentistry & Oral Epidemiology. 1998;26(6):406-11.
Wright JT, Hanson N, Ristic H et al. Fluoride toothpaste efficacy and safety in children younger than 6 years: A systematic review. JADA. 2014. 145(2): 182-189.