Age suitable for children's toothbrush
After all the teeth have erupted, after two years old, when the baby's upper and lower teeth are all erupted, you can use a small soft toothbrush to brush up and down the teeth. At this time, the mother should intentionally start training her baby to brush her teeth, let the baby develop a good habit of brushing his teeth after three meals and before going to bed, and gargle at any time after eating snacks.
https://www.samemater.com/toothbrush/child-toothbrush/toothbrush-for-teeth-training.html