Thumb Sucking and Pacifiers: When Do They Affect Teeth?

Thumb sucking and pacifiers usually don't harm a child's teeth when the habit fades by preschool age. Problems mainly show up when sucking continues as the permanent front teeth get ready to come in, or when it's especially forceful. If your toddler is still attached to a thumb or pacifier, you probably have more time than you think.

This guide explains how sucking habits affect the teeth, the ages that matter most, how pacifiers compare with thumbs, and gentle ways to help your child stop. You can also browse all of our dental services for the rest of your family.

Is Thumb Sucking Normal for Babies and Toddlers?

Yes. Thumb sucking is a natural reflex, and the American Dental Association (ADA) says sucking on thumbs, fingers, or pacifiers helps babies feel secure and happy. Young children often suck to soothe themselves and fall asleep, so a toddler with a thumb habit isn't a cause for alarm on its own.

Sucking starts before birth, and for many babies it's one of the first ways they calm down. Pacifiers serve the same purpose. Researchers call these "non-nutritive sucking habits," meaning sucking for comfort rather than for feeding.

Most children grow out of it without any help. The ADA notes children usually stop sucking between ages two and four, or by the time the permanent front teeth are ready to come in. That timing is the key to the whole question.

So in the baby and toddler years, comfort comes first. There's no need to fight a habit that's doing its job and is likely to fade on its own.

That doesn't mean ignoring it completely. Mention the habit at your child's checkups, even in the toddler years. Your dentist can look at the baby teeth and the shape of the palate and tell you whether anything is changing. According to the ADA, regular dental visits can catch 80% of oral health issues before they become serious. Most of the time, you'll simply hear that everything looks fine for now.

When Do Thumb Sucking and Pacifiers Start to Affect Teeth?

Thumb sucking and pacifiers start to affect teeth mainly when the habit continues past about age three or four, and especially once permanent teeth arrive. The ADA says sucking after the permanent teeth come in can change how the mouth grows, how the teeth line up, and the shape of the roof of the mouth.

Changes can begin a little earlier in some kids. A 2016 study in The Angle Orthodontist followed 422 children in the French EDEN mother-child cohort and found that ongoing pacifier or thumb sucking at age 3 was a risk factor for both a back-tooth crossbite and an open bite in the baby teeth.

A larger look comes from the Iowa Fluoride Study. In a 2005 Pediatric Dentistry report by Warren and colleagues, 55% of 444 children examined in the mixed-teeth years had some kind of bite problem, and 30% had a back-tooth relationship called Class II. Open bites and crossbites were linked to sucking habits lasting 36 months or more. Pacifier habits of 24 to 47 months were tied to open bites, while thumb or finger habits mattered most when they lasted 60 months or longer.

The good news is that many changes in the baby teeth improve once the habit stops, especially if it stops before the adult front teeth erupt.

What Dental Problems Can Long-Term Sucking Cause?

Long-term sucking can cause an open bite, where the front teeth don't meet, upper front teeth that tip forward, a narrow upper jaw with a back-tooth crossbite, and changes to the roof of the mouth. These problems are more likely the longer and harder a child sucks.

Each of these comes from steady pressure. A thumb pushes the upper front teeth forward and the lower ones back. The cheek muscles squeeze the sides of the upper jaw during sucking, which can narrow it over time.

• Open bite: a gap between the upper and lower front teeth when the back teeth close.
• Protruding upper teeth: front teeth that tip outward, which also makes them easier to injure.
• Crossbite: upper back teeth that sit inside the lower ones because the upper jaw has narrowed.
• Palate changes: a higher, narrower roof of the mouth.
• Speech effects: some children with an open bite develop a lisp or tongue thrust.

How hard a child sucks matters as much as how long. The ADA explains that children who rest a thumb passively in the mouth are less likely to have trouble than those who suck vigorously. Some very aggressive thumb suckers can even change their baby teeth.

Listen for it at bedtime. A loud popping sound when the thumb comes out usually means strong suction.

Are Pacifiers Better or Worse Than Thumb Sucking?

Pacifiers affect the teeth in much the same way as thumbs and fingers, according to the ADA, but a pacifier habit is often easier to break. You can take a pacifier away, limit it to bedtime, or phase it out, while a thumb is always available.

Research does show some differences in the details. A 2016 meta-analysis in The Journal of the American Dental Association pooled 15 studies and found pacifier users had about 42% higher risk of a back-tooth crossbite than thumb suckers, based on 7 studies of 5,560 children. Thumb suckers, on the other hand, were more likely to have upper front teeth that stick out. In both groups, a longer habit meant a higher risk.

If your child uses a pacifier, a few habits help protect the teeth. Keep it clean, replace it when it's worn or cracked, and never dip it in sugar, honey, or juice. Sweet coatings feed the bacteria that cause decay in baby teeth.

That risk is real. According to the CDC, 20% of children ages 5 to 11 have at least one untreated decayed tooth. And the ADA notes tooth decay is the most common chronic disease in children, 5 times more common than asthma. A plain, clean pacifier keeps one easy source of sugar out of the picture.

And plan the exit early. Many families start limiting the pacifier to naps and bedtime around age two, then phase it out completely over a few weeks.

How Can You Help Your Child Stop Thumb Sucking?

Most children stop with patience, praise, and a few gentle reminders. The ADA suggests praising your child for not sucking, easing whatever is causing anxiety, and letting older kids help choose how they'll stop. Shaming or punishing a child usually backfires, because sucking is often a response to stress.

Try these steps, roughly in this order:

1. Notice the triggers. Many kids suck when tired, bored, or anxious. Offer a cuddle, a toy, or a new bedtime routine instead.
2. Praise the wins. A sticker chart for thumb-free days works well for preschoolers.
3. Involve your child. Ask an older child how they'd like to stop, and let them pick a reward.
4. Use gentle reminders. The ADA mentions a bandage on the thumb or a sock over the hand at night.
5. Ask your dentist for help. A dentist can explain to your child what the habit does to their teeth, which often carries more weight than a parent's reminder.

Expect slips. Habits tied to sleep are the hardest to break, so daytime success often comes first. Celebrate progress rather than perfection.

Timing helps too. Try not to start during a stressful stretch, like a new baby in the house, a move, or the first weeks of preschool. Kids lean on comfort habits harder when life feels unsettled. A calm, ordinary month gives your child the best chance to succeed.

When Should a Dentist Step In?

Talk with your dentist if your child is still sucking past about age three, if the habit continues as permanent teeth arrive, or if you notice the front teeth tipping forward or not meeting. The American Academy of Pediatric Dentistry (AAPD) says a mouth appliance may be recommended for thumb or finger sucking past age three.

Habit appliances are small, fixed devices that sit behind the upper front teeth and make sucking less satisfying. They don't hurt, but they do take a little getting used to. A 2015 Cochrane Review by Borrie and colleagues looked at six trials with 252 children and found that appliances made children about 6.5 times more likely to stop digit sucking in the short term than no treatment. Positive-reinforcement programs showed a similar effect, about 6.2 times. The authors rated the evidence as low quality, mainly because the trials were small.

You can read the 2015 Cochrane Review on stopping sucking habits for the full details. Most families never need an appliance. But it's a useful option for a school-age child who wants to stop and simply can't at night.

A habit that's already shaped the bite is also a good reason for an orthodontic check around age 7, when your dentist can see how the adult teeth and jaws are developing.

How Do We Help With Sucking Habits at Peterborough Family Dental?

We watch how your child's bite develops at every six-month visit, so we can tell you early whether a thumb or pacifier habit is affecting anything. Most of the time, the answer is "not yet," and we share tips to help your child stop on their own timeline.

If a habit is starting to reshape the bite, our children's interceptive dentistry includes gentle habit appliances that help kids break the habit kindly. We only recommend one when it genuinely helps, and we'll always explain why.

Sucking habits are one piece of a bigger picture. Our guide to your child's dental milestones by age shows what to expect from the first tooth to the teen years.

The most important thing to remember about thumb sucking and pacifiers is timing. A habit that fades before the adult front teeth arrive rarely leaves a mark, so stay patient, keep it positive, and let your dentist keep watch.

Results may vary. Please consult with your dentist at Peterborough Family Dental for personalized treatment recommendations.