The sucking reflex is present in all mammals, including the human infant. Many infants and young children suck their thumbs for comfort. This can have negative effects on dental development, however, including occlusion of primary and permanent teeth.
Why Babies Suck Their Thumbs
The sucking or "rooting" reflex is present at birth and aids in the search for food. Young infants often doze while sucking at a bottle, breast or pacifier. As they continue to grow, this becomes a source of comfort, quelling anxiety and providing relaxation throughout the day. The realization that a thumb can be used to repeat this calming motion is very common among babies.
When Comfort Poses Risks
Some children passively suck their thumbs, but others are more aggressive about doing so. Aggressive sucking and pressure from the thumb being within the mouth can affect the spacing of both primary and adult teeth, as well as change the shape of the roof the mouth.
Specific Effects on Teeth
Long-term thumb sucking causes a gap between the maxillary incisors, or front teeth. This is called an anterior open bite. When these teeth also project outward or upward, it is called proclination and protrusion. Thumb sucking also can cause the maxilla (the bone directly beneath the nose across the front of the jaw) to become displaced in the front, making it poke outward and cause changes to the upper lip. The molars can become displaced due to the abnormal spacing of the teeth, affecting the bite of the mouth. In extreme cases, the molars need to be removed.
Correction of Displaced Teeth
When thumb sucking ceases, teeth that were only mildly displaced often correct themselves. If primary teeth do not self-correct, they may be removed or left alone because they soon fall out to make room for the adult teeth. Extreme cases of occlusion, however, require braces, tooth removal or surgery to correct.
Determent of Thumb-Sucking Behavior
Children who suck their thumbs do not need to be reprimanded as soon as they start doing so. In moderation, thumb sucking is harmless. Because many children suck to calm themselves, finding and removing the stresses that cause thumb sucking may negate its need. If it becomes a long-term problem and causes oral distortion, active deterrent methods can be used, including bandaging the thumb, placing a sock over the arm, and asking a dentist for a bitter ointment to place on the thumb.
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