How Thumb Sucking and Dummies Affect Your Child's Teeth and Jaw
A Normal Habit With a Timeline
Thumb sucking and dummy use are among the most natural and instinctive behaviours in young children. The sucking reflex is present from before birth, and both thumbs and dummies satisfy this reflex in ways that comfort and settle young children effectively. For infants and toddlers, these habits are entirely normal and generally harmless.
The concern arises not with the habit itself but with how long it persists. The teeth and jaw are not static structures during childhood, they are actively developing, erupting, and being shaped by the forces acting on them. A habit that places sustained, repetitive pressure on the developing teeth and jaw does not stay harmless indefinitely. Beyond a certain age and beyond a certain frequency, thumb sucking and dummy use begin to redirect jaw and tooth development in ways that require orthodontic correction to address.
At Dr Gray Dentistry in Durban, Dr Gray is regularly asked by parents how concerned they should be about their child's thumb sucking or dummy habit. The answer depends significantly on the child's age, the frequency and intensity of the habit, and whether any dental or jaw changes are already visible.
What Thumb Sucking and Dummies Actually Do to the Mouth
To understand why these habits matter beyond a certain age, it helps to understand the mechanics of what is happening inside the mouth during sucking.
When a child sucks their thumb or a dummy, several forces act simultaneously on the developing teeth and jaw:
Outward pressure on the upper front teeth
The thumb or dummy sits between the upper and lower front teeth, pushing the upper front teeth forward and outward. Over time and with sufficient frequency, this forward pressure tips the upper front teeth in a forward direction, causing them to protrude beyond their normal position.
Inward pressure on the lower front teeth
Simultaneously, the lower front teeth are pushed inward and backward by the pressure of the thumb or dummy against them, creating a retroclined lower incisor pattern.
Prevention of normal eruption
The physical presence of the thumb or dummy between the teeth prevents the front teeth from erupting fully downward and upward to meet each other. Over time this creates a gap between the upper and lower front teeth that persists even when the mouth is closed — an anterior open bite.
Narrowing of the upper arch
During sucking, the cheeks are drawn inward and the buccinator muscles apply lateral pressure to the upper arch. At the same time, the tongue is displaced downward and forward rather than resting against the palate. The combination of increased lateral muscle pressure from outside and reduced tongue pressure from inside results in a narrowing of the upper arch — the same narrow palate pattern associated with mouth breathing and tongue tie discussed earlier in this series.
Changes to the bite relationship
The combination of protruding upper front teeth, retroclined lower front teeth, and a narrowed upper arch frequently produces a posterior crossbite alongside the anterior open bite, creating a complex bite presentation that requires more extensive orthodontic correction than either problem alone.
At What Age Does the Habit Become a Problem?
This is the most practically important question for parents, and the answer is nuanced.
Before age three
Thumb sucking and dummy use before the age of three rarely cause lasting dental or jaw changes. The primary teeth are present but the permanent teeth have not yet begun to erupt, and the developing jaw is responsive enough that minor habit-related changes tend to self-correct once the habit stops. There is no clinical urgency to eliminate the habit in children under three, though gentle encouragement to reduce frequency is always reasonable.
Between ages three and five
This is the transition period where the habit begins to matter more. The permanent front teeth are preparing to erupt, typically beginning around age six, and the jaw changes that have accumulated during sustained thumb sucking start to become more established. Ideally, the habit should be resolved before the permanent teeth begin erupting. A child who stops thumb sucking at age four gives the jaw and remaining primary teeth time to partially self-correct before the permanent teeth arrive.
After age five
Beyond age five, the habit is affecting a jaw that is increasingly ready to receive the permanent teeth. Changes that accumulate from this point onward are more likely to be carried forward into the permanent dentition rather than self-correcting. The urgency to address the habit increases significantly once the permanent front teeth begin erupting, typically between ages six and eight, because thumb sucking that continues after permanent teeth have erupted directly affects the permanent tooth positions and bite relationship.
After permanent teeth have erupted
A thumb sucking habit that persists after the permanent front teeth have erupted is creating ongoing orthodontic problems in teeth that will not be replaced. The open bite, proclination of the upper incisors, and narrowed arch that result at this stage require active orthodontic correction and will not self-resolve once the habit stops.
Dummies Versus Thumb Sucking: Is One Worse?
Parents often ask whether dummies or thumb sucking cause more dental damage. The general answer is that dummy use tends to cause less severe and more reversible dental changes than thumb sucking, for two reasons.
First, a dummy can be taken away. The parent has control over when and how frequently the habit occurs, and elimination of the habit can be planned and managed. A thumb is always available, which means the child has complete control over access and the habit can occur at any time, including throughout the night during sleep.
Second, the sucking mechanics differ slightly. Dummy use tends to produce a more symmetrical dental effect, while thumb sucking can produce more asymmetric changes depending on how the thumb is positioned. The intensity of the sucking force tends to be higher with thumb sucking.
That said, both habits produce significant dental and jaw changes when they persist beyond the appropriate age, and neither should be dismissed as harmless simply because one may be marginally less damaging than the other.
Signs That the Habit Has Already Affected the Teeth and Jaw
Parents who are concerned about their child's habit should look for the following signs that dental or jaw changes may already be present:
The upper front teeth protrude forward noticeably, giving the appearance that they stick out. A gap is visible between the upper and lower front teeth when the mouth is closed. The upper arch appears narrow and high when the child opens their mouth wide. The lower front teeth appear to slope backward. A crossbite is present where some upper back teeth bite inside the lower back teeth. The child has difficulty biting into food with their front teeth.
If any of these signs are present, an assessment at Dr Gray Dentistry is the appropriate next step — both to understand the extent of the changes and to discuss the most appropriate timing and approach for correction.
How to Help Your Child Stop
Breaking a thumb sucking or dummy habit requires a different approach at different ages.
For dummies
Because parents control access to dummies, elimination is more straightforward in principle, though it can still be emotionally challenging for both child and parent. The most effective approaches involve a clear, consistent transition rather than gradual reduction. Choosing a specific day to stop, involving the child in the decision where age-appropriate, and having a small reward or ritual to mark the occasion tends to be more effective than attempting to reduce use incrementally.
For thumb sucking
Thumb sucking is more challenging to address because the child has constant access and because the habit frequently occurs during sleep without any conscious awareness. Approaches that have evidence for effectiveness include:
Positive reinforcement for periods without thumb sucking, using a simple reward chart appropriate to the child's age. Identifying and addressing the triggers for thumb sucking, which is frequently stress, boredom, or fatigue, and providing alternative comfort strategies.
A habit appliance fitted by Dr Gray at Dr Gray Dentistry, such as a tongue gate or palatal crib, creates a physical barrier that makes thumb sucking ineffective and uncomfortable. This approach is particularly valuable for older children who have tried behavioural approaches without success, and it is highly effective at breaking the habit quickly. Most children stop within two to four weeks of having a habit appliance fitted, because the comfort derived from the sucking is eliminated by the appliance.
Can the Damage Be Reversed?
For children who stop the habit before the permanent teeth erupt, a significant degree of self-correction occurs naturally. The jaw is growing and responsive, and removing the habit-related force allows normal developmental forces to redirect growth in a more favourable direction. Some open bites partially close. Some arch width recovers. Not all changes reverse completely, but the extent of correction needed is considerably less than in a child who continues the habit into the permanent dentition.
For children whose habit has persisted into the permanent dentition, orthodontic correction is needed to address the established changes. The extent of correction required depends on the severity of the bite changes present. Mild to moderate open bites and arch narrowing respond well to orthodontic treatment. Severe skeletal changes involving the jaw structure itself may require a more complex approach. The earlier the habit is stopped and treatment is initiated, the simpler the correction.
Address Your Child's Habit at Dr Gray Dentistry, Durban
Whether your child is still young and you want to understand when the habit becomes a concern, or you have an older child whose habit has already produced noticeable dental changes, a thorough assessment with Dr Gray at Dr Gray Dentistry in Durban, South Africa gives you a clear picture of where things stand and what the most appropriate next step is.
Dr Gray assesses the dental and jaw effects of oral habits as part of every child's orthodontic evaluation, recommending habit appliances where indicated and planning any necessary orthodontic correction around the child's stage of dental development.
Book your child's assessment at Dr Gray Dentistry in Durban today.