Short answer. Thumb sucking is normal in babies and toddlers and usually leaves no lasting change if it ends by about age 4. It becomes a dental problem when it continues as the adult front teeth come in, around age 6. By then a strong habit can push the upper front teeth forward, hold the front teeth apart so they do not meet, and narrow the upper jaw. Most changes improve if the habit stops early. A narrowed jaw and a bite that has adapted to it usually need orthodontic treatment.
By Rodrigo F. Viecilli, DDS, PhD, board-certified orthodontist at Limestone Hills Orthodontics in Austin, TX. Before opening the practice he spent five years treating children in pediatric orthodontic offices.
Thumb sucking by age: what is normal
| Age | What is normal | What to do |
|---|---|---|
| Birth to 2 | Sucking is a reflex and a way to self-soothe | Nothing |
| 2 to 4 | Most children give it up on their own | Praise the times the thumb is out. No pressure |
| 4 to 6 | A habit that remains is now learned comfort | Help the child stop before the adult front teeth arrive |
| 6 and older | Adult front teeth are coming in | Have the bite checked, and treat the habit as something to end now |
Three things decide whether a habit leaves a mark: how many hours a day, how many years, and how hard the child sucks. A thumb that rests in the mouth at bedtime does far less than one that is pulled on for hours.
What thumb sucking does to teeth and jaws
- Open bite. The front teeth do not meet when the back teeth are together, because the thumb sits between them while they come in. See open bite treatment.
- Front teeth that stick out. The thumb pushes the upper front teeth forward and the lower front teeth back, which increases the horizontal gap between them.
- A narrow upper jaw and crossbite. Cheek pressure during sucking squeezes the upper arch. The upper back teeth then bite inside the lower ones. See crossbite in children.
- Tongue thrust and a lisp. With a gap at the front, the tongue learns to push forward to seal it during swallowing and speech. See tongue thrust.
What the research shows
University of Iowa researchers followed 372 children from birth and examined their teeth at age 4 to 5. Children with long-lasting thumb, finger or pacifier habits had more changes in their bite and dental arches, and some of those changes, such as a crossbite and front teeth that stuck out, were still present well after the habit had stopped. The authors concluded that the usual advice on when to stop may come too late to prevent every effect, which is an argument for helping a child stop sooner, not later.
Will the teeth fix themselves?
| Change | If the habit stops before the adult front teeth come in | If it continues past that |
|---|---|---|
| Open bite | Often closes on its own over several months | Usually needs treatment, and the tongue habit that follows has to be addressed too |
| Front teeth that stick out | Often improves | Usually needs braces |
| Narrow upper jaw or crossbite | Rarely corrects on its own | Needs an expander |
Thumb or pacifier: which is worse for teeth?
Both can change the bite if the habit lasts. A pacifier is easier to end, because a parent can take it away. Pediatric dental guidance is to wean from the pacifier by about age 3. A thumb is always available, which is why thumb habits tend to last longer and do more.
How to help a child stop sucking a thumb
- Pick a calm stretch. Not the week of a move, a new sibling or the start of school.
- Explain why, simply. The new teeth need room to come in straight.
- Find the triggers. Tiredness, boredom, screens, the car seat, bedtime. Offer something for the hands at those times.
- Reward the thumb being out. A sticker chart with a small prize after a week and a bigger one after a month works better than any penalty.
- Use a reminder, with the child’s agreement. A bandage on the thumb, a sock over the hand at night or a fabric thumb guard. These are reminders, not punishments.
- Do not shame or scold. Stress feeds the habit.
- Bring in the dentist or orthodontist. Many children accept from a doctor what they resist from a parent.
Give a new approach about a month before judging it. Most habits end in stages: first during the day, then at night.
When a habit appliance helps
If a child of 6 or 7 wants to stop and cannot, an orthodontist can place a small fixed appliance behind the upper front teeth. It does not hurt. It takes away the seal that makes sucking satisfying, and most habits end within weeks. The appliance usually stays for several months so the habit does not return. When the upper jaw has narrowed, a palatal expander can widen it and block the thumb at the same time.
At Limestone Hills this is part of early treatment, which starts at $2,000, and children who do not need treatment yet are rechecked every 6 to 12 months at no charge. See children’s orthodontics and Phase 1 vs Phase 2.
When to see an orthodontist
- The habit is still going as the adult front teeth come in.
- The front teeth do not touch when your child bites down.
- The upper front teeth stick out, or the lower lip rests behind them.
- The upper back teeth bite inside the lower back teeth.
- Your child wants to stop and has not managed to.
These are also on the list of signs your child needs braces.
Common questions about thumb sucking and teeth
At what age should a child stop sucking their thumb?
Most children stop on their own between 2 and 4. The goal is for the habit to be over before the adult front teeth come in, which is around age 6. If it is still going at 4 or 5, it is time to start helping.
Can thumb sucking cause buck teeth?
Yes. A strong, lasting habit pushes the upper front teeth forward and the lower front teeth back. If the habit ends early the teeth often improve. If it lasts into the school years, braces are usually needed.
Does thumb sucking change the shape of the jaw or face?
It can narrow the upper jaw and change how the front of the mouth closes, so the lips may not meet at rest. It does not reshape the whole face. The jaw width can be corrected with an expander while a child is growing.
Is a pacifier better than a thumb for teeth?
Neither is better for the teeth, but a pacifier habit is easier to end because it can be taken away. Either one can change the bite if it lasts past the early years.
Can thumb sucking damage an adult’s teeth?
Yes. In adults the same forces move teeth, producing an open bite or front teeth that flare forward. The bite can be corrected with braces or aligners, and the result lasts only if the habit stops.
Limestone Hills Orthodontics sees children from age 7 at its office on RM 2222 in Northwest Austin. No referral is needed. Book a free orthodontic consultation or call (512) 720-6399.
Sources. Warren JJ, Bishara SE. Duration of nutritive and nonnutritive sucking behaviors and their effects on the dental arches in the primary dentition. Am J Orthod Dentofacial Orthop. 2002;121(4):347-356. doi:10.1067/mod.2002.121445. American Dental Association, Thumbsucking (mouthhealthy.org). American Academy of Pediatric Dentistry, guidance on pacifiers and oral habits (aapd.org). Fees from Limestone Hills Orthodontics, Austin, TX.
