Digit Sucking
Digit sucking is a habit that occurs in infants. Children usually give up digit sucking by the age of four. If the child continues past the age when their permanent teeth start to erupt, they may develop crooked teeth and a malformed roof of their mouth. This results from the frequency, duration, intensity, and position of the digit in the child’s mouth. This can also affect the position of the upper and lower jaw and can also affect speech.
Suggestions to break the habit:
Wait till the time is right (low stress).
Motivate your child (show examples of what could happen to their teeth and fingers/thumbs).
Use a reward system (small incentives will encourage your child to stick with it).