Does thumb-sucking affect permanent teeth growth?

Yes, if it continues past age 4 it can affect tooth alignment. The force of sucking can 1) push the upper front teeth forward, 2) create an open bite in which the upper and lower front teeth do not meet, and 3) narrow the upper jaw. Sucking before age 3 is natural behavior and usually stops on its own, so you can watch and wait rather than forcing it to stop. However, if it continues past ages 4 to 5, or the front teeth already look out of line, a habit-breaking appliance and other help are available, so please have a pediatric dental consultation.