You may use toothbrush (Oral B, Pigeon or other brands for children of this age) and toothpaste (Pigeon, Chicco or Firstteeth, these toothpaste can be swallowed). The toothbrush & toothpaste can be purchased from Department Stores like Wing On & Jusco.
Sing & play with bb. Always bring him along to see you brush your own teeth every morning & night so as to give him the concept of brushing teeth. It would help.