As a parent, you are concerned about a number of issues related to your child's health, including their teeth. One of the most common is thumb-sucking.
While thumb sucking has lately been a concern, it is normal and should not be considered harmful in infants and very young children. You can also help your child to stop thumb sucking via https://www.amazon.co.uk/Age-2-7-Stop-Thumb-Sucking/dp/B00VQU2DZS.
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Babies and toddlers feel comfortable or safe when they suck their thumbs, which resembles infant feeding.
As soon as their main teeth begin to grow, their swallowing pattern changes, and they touch the roof of the mouth of the tongue just behind the front teeth as they swallow.
For most children, thumb sucking begins to decrease as the way their swallow pattern changes. However, some children continue this habit for longer even after their permanent teeth come out.
When they suck on the thumb, the tongue continues to be between the front teeth, which over time can affect their development. This can lead to an "open bite", where the lower and upper teeth don't meet properly.
For this reason, dentists usually recommend that children stop thumb sucking until they are 3 years old (18-24 months to stop using a pacifier).
The best way is positive support- providing suitable rewards from time to time for appropriate behavior: for example, praising them as a "big" boy or girl when they have gone through a certain amount of time without sucking their thumb or pacifier.
Habits like thumb-sucking in young children need to be remembered: they are not really a problem unless they last too long.