Thumb Sucking

Thumb Sucking

Thumb or finger sucking is common in children and some will even have started in the womb before they were born. Parents can be reassured, however, that it does not damage most children’s teeth. A small number of children do change the position of their teeth, and a few of them change not only their teeth but also the shape of the bone supporting the upper teeth, and can even bend their fingers.

For teeth to move, the duration of the habit is relevant which means the thumb sucking habit needs to be of long duration each day to have any effect.

It is best if the digit sucking habit ceases before the permanent teeth come through at 7 years of age, but the habit can be very difficult to break, and, rarely, some patients still suck their fingers as adults. For orthodontic treatment to be successful there needs to be a willingness on the part of the child to stop the habit. The force of the thumb can be stronger than the action of the brace and there have been cases where no progress has been made until it was revealed that the habit was continuing. So starting treatment as a way to stop the habit may not be a good idea.

It is important to know that teeth are never ‘set’ and are free to move throughout our lifetime. Teeth need to be able to do this in order to adapt to any changes that occur e.g. if we wear down the biting surfaces of our back teeth, they erupt to fill the gap created to prevent our chins from becoming closer to our nose and the face shortening. Teeth know when they are at the correct height for our chewing muscles to work efficiently. At birth, a baby has no teeth, and when they come through, they erupt until they meet the opposing teeth to produce a biting position. Teeth, therefore, erupt until they meet another tooth and stop growing, but they may meet a finger or thumb instead. In this case, the teeth will have stopped short and there will be a gap between the front teeth, known as an open bite.

Our teeth are positioned where they are by the muscles of the face pressing on them. It takes very little pressure to move teeth and the muscles of the lips and cheek on the outside are balanced by the tongue muscles on the inside. Introduce a thumb or finger into the equation and the balance will change, and so will the position of the teeth. The good news is that if the digit sucking habit ceases, the equation is restored, and the effects of the habit can go into reverse allowing the teeth to spontaneously align. No treatment may be required.

When we swallow it is necessary to close off the front of the mouth. It is not possible for you to swallow with your mouth open. Normally this means placing the lips together with the tongue behind the front teeth. With a digit in the way however, the swallowing pattern is altered and severe cases can have a big influence on the teeth. The upper teeth will lean forwards and the bone around the teeth can be distorted, the lower teeth will lean inwards, there will be an open bite as already mentioned, and the cheek teeth will be constricted making the upper back teeth bite inside the lower teeth which is the wrong way round. Dentists call this a ‘crossbite’. With a thumb in the mouth, the tongue is held down away from the upper teeth and no longer able to control the shape of the upper set. The cheek muscles are therefore unopposed and mould the cheek teeth inwards to produce the crossbite and a narrow upper jaw. The situation is unlikely to spontaneously correct since sometimes when the habit stops, the tongue takes over to plug the gap left by the thumb. The tongue moves forwards to meet the lower lip and the open bite is maintained. Treatment will be required to correct it. If left untreated, speech will be affected with the tongue evident at the front of the mouth causing lisping.

Patients can be reluctant to divulge their habit and it helps if we can raise the issue to break the ice. We can usually spot a thumb sucker when they arrive into the surgery but sometimes we are wrong and there is no history of digit sucking as some of the above mentioned dental characteristics can occur naturally.

We have discussed the problems that a digit sucking habit causes. There are, however, things that it does not cause. The most common orthodontic problem in our practice, and indeed in Western Europe, is dental crowding. It is due to a mismatch between the size of the individual teeth and the size of the jaws to accommodate them. Digit sucking does not cause crowding because in this latter situation there is a shortage of space for the teeth even before they have erupted so they will not be straight. Some parents, therefore, come to the practice thinking that their child has made their teeth crooked by thumb sucking when it was due to crowding and the thumb has at best only slightly modified the problem.

Gentle encouragement is the best approach to deter a digit sucking habit and it is unwise to make it a big issue in the family. The child will stop when they are ready.