An underbite in a child means the lower front teeth sit in front of the upper front teeth when they bite. It can come from the teeth, the jaws or both. An orthodontist can usually tell which by about age seven, while there is still time to guide growth.
Parents often notice an underbite in photos, or when their child’s chin seems to jut forward. It is natural to wonder whether it will fix itself, whether it is serious and when treatment should start. Below, we explain what causes underbites in kids, why timing matters so much, what early treatment can involve and what you can expect at a first visit with Dr. R.
What Is an Underbite in a Child?
In a typical bite, the upper front teeth close slightly in front of the lower front teeth. In an underbite, that relationship is reversed. The lower teeth overlap the upper teeth, and the lower jaw can look prominent from the side. Our post on common orthodontic problems notes that underbites, like overbites, can cause difficulties with chewing, speech and jaw function.
Not every reversed bite is the same, and that is why an exam matters. Sometimes only one or two front teeth are tipped behind the lower teeth, which is often called an anterior crossbite. In other children, the whole lower jaw sits forward or the upper jaw is small. Both can look similar in the mirror, but they are treated differently.
What Causes an Underbite in Kids?
Most underbites have more than one contributing cause. Jaw size and growth patterns often run in families, so a parent or grandparent with a strong lower jaw is a useful clue. An upper jaw that is narrow or underdeveloped can let the lower teeth close in front. In some children, the lower jaw is simply growing more than the upper jaw.
Habits can play a part too. A tongue that rests low and pushes forward, long-term thumb sucking, or a pacifier used well into childhood can change how the teeth and jaws develop. Mouth breathing from chronic congestion can also influence how the jaws grow. Sometimes the cause is purely dental: a front tooth comes in behind its neighbor and gets locked behind the lower teeth.
A functional shift is another common pattern. The child can actually bite edge to edge, but the teeth hit early, so the lower jaw slides forward to close comfortably. That sliding jaw is one of the early warning signs we describe in our overview of two-phase orthodontic treatment, and it is a good reason to have your child checked.
| Type | What is going on | How it is often addressed |
|---|---|---|
| Dental (one or two teeth) | Upper front teeth tipped behind lower teeth | Moving the teeth with braces or an appliance |
| Functional shift | Teeth hit early, so the jaw slides forward | Removing the interference so the jaw closes naturally |
| Small upper jaw | Upper arch too narrow or short | Early expansion while the child is growing |
| Skeletal growth pattern | Lower jaw growing more than the upper jaw | Growth guidance in childhood, then reassessment as growth finishes |
Will a Child’s Underbite Correct Itself?
Usually not. A dental crossbite on one or two teeth can sometimes improve as the permanent teeth erupt, but a true jaw-based underbite does not tend to get better with growth. Because the lower jaw keeps growing into the teen years, a skeletal underbite can actually become more noticeable over time.
That is why waiting to see is not the same as watching with an orthodontist. Our post on early orthodontic treatment explains how an evaluation during the mixed-teeth years lets us catch problems while growth can still help, instead of working against it.
Why Is Early Treatment Important for Underbites?
Timing is the most important factor with underbites. The American Association of Orthodontists recommends that children see an orthodontist by about age seven. By then, Dr. R can see how the jaws are growing and how much room the permanent teeth will have, and with baby teeth still in place, there is time to use growth instead of fighting it.
If your child does need early care, it typically falls in phase one of a two-phase plan, roughly between seven and ten, when the focus is steering jaw growth and making space for adult teeth. A palatal expander is a common tool. At Vibrant Orthodontics, expanders are designed from an iTero digital scan and made with 3D printing and laser-sintered bands, for a precise fit with smooth edges. Our guide to palate expanders for kids explains how they work.
Phase one is followed by a rest period as the rest of the adult teeth erupt, and phase two uses full braces to straighten each tooth and perfect the bite. For an underbite, the payoff of starting early is that jaw differences get attention while the child is still growing, which can make the later stage simpler. Not every child with a reversed bite needs two phases, and Dr. R only suggests it when it will clearly help.
What Happens at Your Child’s First Visit?
The first appointment is a free consultation. Expect a relaxed conversation, a quick digital scan in place of messy impression putty, and a straight answer about whether your child needs anything now. Dr. R examines the teeth, jaws and facial structure and explains what she sees in plain language.
Often the right move is to monitor. Children who do not need treatment yet can join the Vibrant Kids Club, a complimentary program with free growth screenings, so Dr. R can keep an eye on the bite as it develops. If treatment makes sense now, you leave with a plan, a timeline and a review of simple monthly payment options, with no pressure to decide on the spot.
What Can Parents Watch for at Home?
You do not need any special tools to spot the early signs. Look at your child from the side while they bite their back teeth together: do the lower front teeth close in front of the upper ones? Watch whether the jaw slides forward or to one side as they close, and notice if chewing seems awkward or certain sounds are hard to make.
Habits are worth noting too. If your child still sucks a thumb or finger, breathes through the mouth much of the time, or snores, mention it at the visit. Chronic congestion is something to raise with your pediatrician as well. None of these signs means treatment is certain, but together they help Dr. R understand what is driving the bite and whether to act now or simply monitor.
Frequently Asked Questions
At what age should an underbite be treated?
It depends on the cause. Many jaw-related underbites respond most predictably to early treatment during the growth years, which is why the first check is recommended by about age seven.
Can braces fix an underbite?
Braces can fix many underbites, especially dental ones, and they finish the bite in phase two. Jaw-based underbites often need growth guidance first.
Is an underbite bad for my child’s health?
It can be. Underbites can make chewing and speaking harder, put uneven wear on teeth and affect jaw function, so an evaluation is worth it even if it does not bother your child.
Can an underbite be fixed in adults?
Often, yes. Dental underbites can be corrected with braces at any age. Once growth has finished, severe jaw-based underbites are harder to change with braces alone, and an orthodontist can explain what options make sense.
Book Your Child’s Free Underbite Check
Dr. Maryam Rezaie earned her DMD at the University of Florida and trained in orthodontics at Jacksonville University School of Orthodontics before opening Vibrant Orthodontics in Tallahassee in 2021. If you have noticed an underbite, request a free consultation or call or text (850) 385-8101.