It is completely normal and healthy for your baby or young child to suck on a thumb, finger, or pacifier. Children usually give up sucking habits on their own by the time they are 4 to 5 years old. If they stop the habit at this age, the shape of the jaw is usually not affected and the teeth grow in normally. Children who continue sucking on a pacifier, finger, or thumb when their permanent adult teeth start to come in are more likely to have bite problems. Sucking can cause: – The top front teeth to slant out – The bottom front teeth to tilt in – The upper and lower jaws to be misaligned – The roof of the mouth to be narrowed – The need for braces Treatment: Your doctor may decide to construct an appliance to discourage thumb sucking.