Thumb-sucking is a normal habit in a child’s life – all babies suck their fingers or like to suck on the pacifier, but most of them grow out of the habit by the age of 3.
Finger-sucking starts affecting the child’s teeth if the habit persists after the age of 3. The sucking itself affects the direction in which the teeth grow, while the pressure of the thumb or of the finger on the lower denture can also deform the teeth, preventing them from erupting properly, pushing them forward, causing them to grow unevenly or to overlap. Finger sucking can negatively affect the development of the jaws as well, leading to an open bite, which means that the upper and lower teeth don’t meet correctly when the child bites.
Thumb-sucking being harmful if it goes on after the age by which most temporary teeth have erupted, parents need to discourage the habit by means of gentle persuasion. The best way to get your child to stop is by explaining to the kid about the harm that is being done to his or her teeth and rewarding the kid with an activity he or she likes. You can also try to creatively distract the child in situations that would normally prompt thumb-sucking.