The single best way to remove harmful plaque (a thin, sticky film of bacteria) from your child's teeth and gums is to brush his teeth regularly and properly.
When to begin brushing your child's teeth
Brushing your child's teeth should begin at an early age, around 24 months, or as directed by your child's physician. Children will need help brushing their teeth until they are around the age of 7 to 8. Even before your child actually has teeth, it's important to perform mouth care.