By the time they are 3 years old, most children will have 20 primary teeth. The most common cause of tooth decay in children is usually sugary drink.

Some of the tips to prevent tooth decay are:

• Put only plain water, formula, milk or breast milk in bottles.
  Juice and sweetened water can cause decay. 
  
• Avoid putting your child to bed with a bottle.
  Milk (even breast milk) can still cause decay. 
  
• Try not to share saliva with your baby by using
  the same spoon or licking a pacifier to clean it. 
  
• Tooth decay cavity causing bacteria can be passed from the mother to the baby. 
  
• Keep your baby's gums and teeth clean with gauze or washcloth. 
  
• You can start using a toothbrush when you see their teeth peeking through.