Written by Dr James Tran, principal dentist at Lumi Dental.
Sucking is one of the first things a baby learns to do, and a thumb or a dummy is a normal, healthy way for a young child to self-soothe. Most children give up the habit on their own with no lasting effect on their teeth. The picture only changes when the habit carries on past a certain age, because prolonged, forceful sucking can gradually reshape a growing mouth. This guide explains what thumb sucking and dummies do to developing teeth, when it starts to matter, and how to help your child ease off without a battle.
Key takeaways
- Thumb sucking and dummy use are normal in babies and toddlers, and most children stop on their own between about two and four.
- The habit tends to matter most if it continues strongly past age four, or once the permanent front teeth start to come through.
- Prolonged sucking can push the upper front teeth forward, create an open bite, and narrow the upper jaw.
- The earlier a child stops, the more likely any changes will settle as the mouth keeps growing.
- Gentle, positive strategies work far better than shaming, and your dentist can help if the habit is stubborn.
The one rule: it is about how long the habit lasts, not that it exists
The key idea for parents is that a sucking habit in a baby or young toddler is not something to worry about. It becomes a dental question only when it persists. Research shows the risk of a lasting bite problem climbs with age: relatively few children who stop by around age two show a bite change, while a majority who keep going well past four do. So the goal is not to stop a one-year-old, but to help a child move on from the habit before the permanent teeth and jaw growth start to lock in the changes.
How sucking affects the teeth and jaw
Constant pressure from a thumb or dummy, repeated over years, gently nudges teeth and bone into new positions. The common effects include:
- Protruding upper front teeth, tilted forward by the pressure of the thumb behind them.
- An anterior open bite, where the front teeth do not meet even when the back teeth are closed, leaving a gap the thumb used to fill.
- A posterior crossbite, where the upper back teeth sit inside the lower ones, often linked to a narrowed upper jaw.
- A high, narrow palate, shaped by the tongue sitting low and the cheeks pressing in during sucking.
How much change occurs depends on how often, how long, and how forcefully the child sucks. A child who sucks vigorously all night has more effect than one who rests a thumb in the mouth occasionally.
Thumb versus dummy
Parents often ask which is worse. Both can affect the bite in similar ways if used for too long. A dummy has one practical advantage: it is easier to take away than a thumb, because you control the object. So-called orthodontic dummy shapes are marketed as gentler on the teeth, but no dummy fully prevents bite changes if it is used heavily for years. The sensible approach with a dummy is to limit it to sleep and comfort from around age one, and to begin weaning it by two to three. A thumb requires a different plan, since it is always available, which is where the strategies below come in.
When to start helping your child stop
Most children need no intervention, as they drop the habit naturally. Start gently encouraging a stop if the habit is still strong as your child approaches age four, and act sooner if you already see the front teeth being pushed forward or an open bite forming. The arrival of the permanent front teeth, usually around age six, is the point at which lingering habits are most worth addressing, since those are the teeth that will stay.
Gentle ways to help
Pressure and punishment tend to backfire, because the habit is a comfort mechanism. These approaches work better:
- Use praise and rewards, such as a sticker chart for dummy-free or thumb-free days.
- Find the triggers. Tiredness, boredom, and anxiety often set off sucking, so address the underlying need with comfort or distraction.
- Offer a gentle reminder, agreed with your child, rather than a telling-off, especially for unconscious daytime sucking.
- Cover the thumb at night with a soft glove or a plaster as a reminder, once your child is on board with stopping.
- Involve your child. Older toddlers and preschoolers respond well to being part of the plan rather than having it imposed.
If the habit is entrenched and the bite is being affected, your dentist can help. Options include a simple reminder appliance fitted to discourage sucking, used only when other approaches have not worked. In many children, a bite that has been altered by sucking improves on its own once the habit stops, while the jaws are still growing. If changes remain, they can be addressed later with orthodontics, as covered in our guide to straightening crooked teeth.
Keeping an eye on things
Regular dental visits are the easiest way to catch any early bite change and get tailored advice for your child. A first visit around the first birthday and check-ups from there let your dentist track development, as explained in our guide to a child's first dental visit. For a sense of the wider timeline of tooth development, see when adult teeth come in.
Frequently asked questions
At what age should my child stop sucking their thumb?
Most children stop on their own between two and four. It is worth gently encouraging a stop if the habit is still strong by around age four, and particularly before the permanent front teeth come through at about six, since that is when lasting changes are most likely.
Will thumb sucking permanently damage my child's teeth?
Not usually, if the habit stops in time. Bite changes caused by sucking often improve on their own once the habit ends while the mouth is still growing. Changes are more likely to persist if the habit continues into the permanent teeth years.
Are orthodontic dummies better for the teeth?
They are shaped to reduce pressure on the teeth, but no dummy fully prevents bite changes if used heavily for years. Limiting dummy use and weaning by two to three matters more than the shape of the dummy.
How do I get my child to stop without a fight?
Focus on positive reinforcement, reward dummy-free or thumb-free days, and address the triggers like tiredness or anxiety. Reminders should be gentle and agreed with your child. If the habit is stubborn and affecting the bite, your dentist can advise on further help.
The takeaway
Thumb sucking and dummies are a normal part of early childhood and rarely cause lasting harm when the habit stops in good time. The thing to watch is a strong habit continuing past age four or into the permanent teeth. Gentle, positive encouragement usually does the job, and your dentist is there to help if it does not. To have your child's teeth and bite checked, the team at Lumi Dental in Melrose Park is happy to help. See our general dental care or current offers on the deals page. This article is general information and not a substitute for personal dental advice.
