Many babies and young children develop the habit of thumb sucking. It often helps them feel safe, calm down, or fall asleep. While occasional thumb sucking during the early years is generally no cause for concern, continuing the habit as the child grows older can affect the development and alignment of their teeth and jaw. 

Below, we will explain how thumb sucking affects the mouth and when parents should start helping their child break the habit.

Why Do Children Suck Their Thumbs? 

Sucking is a natural reflex that begins during infancy. Babies use sucking to feed and often to soothe themselves. As children grow, some continue sucking their thumbs because it helps them relax, handle stress, cope with unexpected changes, or settle down for sleep. Children may also turn to this habit when they are bored and experience minor discomfort, like teething. 

Many children naturally stop thumb sucking between ages two and four. If the habit continues beyond this period, particularly when the child sucks forcefully or frequently, it may begin to affect their teeth and mouth. 

Is Thumb Sucking Harmful to Teeth? 

Thumb sucking can cause harm, but the effects depend on several factors, such as how often your child sucks their thumb, how strongly they suck, and how long the habit continues.

The American Dental Association notes that children who simply rest their thumb in their mouth are less likely to experience dental problems than children who suck vigorously. However, prolonged or intense thumb sucking can place pressure on developing teeth and jaws.

Potential dental effects can include:

Protruding Upper Front Teeth — The upper teeth may begin to tip outward and forward, commonly referred to as an overbite. 

Open Bite — The upper and lower front teeth may fail to overlap or touch even when the back jaw is closed completely. 

Changes to the Roof of the Mouth — Prolonged sucking can influence the shape of the palate. It may become high and deeply indented.  

Bite and Alignment Problems — The way the upper and lower teeth come together may be affected. For example, your child could develop a posterior crossbite, where the upper back teeth bite inside the lower back teeth rather than outside them. 

Changes in Jaw Development — Persistent thumb sucking can cause changes in developing dental arches. The lower jaw could shift to one side, leading to permanent asymmetrical jaw development, or the pressure can narrow the upper jaw.

Children can also develop a speech impediment, have difficulty biting or chewing, or need future orthodontic treatment. 

Not every child who sucks their thumb will develop these problems. The frequency, duration, and intensity of the habit all play a role.

What Age Should a Child Stop Thumb Sucking? 

There isn’t a standard age where every child must stop. Many children quit on their own between ages two and four. However, if your child continues to suck their thumb past age three, you may want to discuss the habit with a dentist. 

The American Academy of Pediatrics notes that strong thumb or finger sucking beyond age four can affect the shape of the mouth and the alignment of the teeth. Fortunately, if the habit stops before the permanent front teeth come in, bite changes have a high chance of correctly themselves naturally. 

Should Parents Force a Child to Stop? 

Punishment, teasing, or harsh criticism can make it harder and more stressful to break a thumb-sucking habit. Instead of using force or pressure, focus on positive encouragement. 

Pay attention to when your child tends to suck their thumb. If they do it when they’re tired, bored, anxious, or upset, they may need another form of comfort. 

Consider: 

• Praising your child when they don’t suck their thumb
• Offering a favorite stuffed animal or blanket for comfort
• Keeping their hands occupied during common thumb-sucking times
• Using gentle reminders rather than criticism 
• Creating a reward system for reaching small milestones
• Talking with your child about why you want them to stop
• Covering their hand at night to help stop the unconscious reflex

You want your child to feel supported rather than embarrassed or in trouble.

The Bottom Line 

Thumb sucking is a normal behavior during infancy and early childhood, and many children naturally outgrow it. However, prolonged or vigorous thumb sucking can affect the alignment of your child’s teeth, their bite, and the development of their mouth.

If your child continues sucking their thumb beyond age three or you notice changes in their teeth or bite, talk with a pediatric dentist at Children’s Dentistry of Pocatello. With encouragement, patience, and professional guidance, most children can stop this habit and protect their smile.