A crossbite is when some upper teeth bite inside the lower teeth instead of just outside them. It can affect the front teeth (anterior crossbite) or the back teeth on one or both sides (posterior crossbite). Back-teeth crossbites in children are often corrected with a palate expander; other cases are treated with braces or aligners.
What causes a crossbite
- A narrow upper jaw is the usual cause of a back-teeth crossbite. It can be inherited, and long-term thumb sucking, dummy use and mouth breathing are all linked with a narrower palate.
- An adult front tooth can come through behind the lower teeth, often because of crowding or a baby tooth that stayed too long.
- When the lower jaw outgrows the upper, several front teeth can end up in crossbite, which overlaps with an underbite.
Why it matters
Many children with a crossbite on one side slide the lower jaw sideways to make their teeth meet. Over years of growth, the jaw can adapt to that shifted position, and the bite and jaw may develop slightly lopsided. A front-tooth crossbite can chip the upper tooth's edge and push the lower tooth forward until the gum over it thins. In adults, crossbites can wear teeth unevenly. None of this is an emergency, but correction is much simpler while a child is still growing.
How we assess it
At your complimentary consultation, Dr Anand Srinivasa, our principal clinician, who has practised orthodontics for 26 years, takes records (photos, digital scans and X-rays where needed) and watches how the jaw closes, because a sideways slide changes the plan. He checks whether the narrowness is in the jaw or only in the teeth, then plans treatment digitally. You receive a written plan with the options, how long each commonly takes and the full cost. No referral is needed, and Saturday appointments and free parking make the visits easier to fit around school.
Treatment by age
- Children, about 7 to 11: for a back-teeth crossbite, a palate expander gently widens the upper jaw while its two halves are still joined by a growth seam. Turning commonly takes a few weeks, then the expander stays in for a few months while new bone fills in. A gap between the front teeth often appears during expansion, and that is expected. A single front tooth in crossbite is often corrected within a few months with a small appliance or partial braces. See early orthodontics.
- Teens: expansion can still work in younger teens, with Damon™ braces or Invisalign® to align the teeth, commonly over 12 to 24 months.
- Adults: once the seam has fused, an ordinary expander cannot reliably widen the jaw. Braces or aligners can correct many crossbites that involve one or two teeth. A large width difference in the jaw itself may need surgically assisted expansion, and for that Dr Anand would refer you to an oral and maxillofacial surgeon, because Align does not perform surgery. See adult orthodontics.
Keeping the result
A widened jaw needs holding while the bone settles, so the expander or a retainer stays in place for a while after the correction, and retainers continue after any braces or aligners. Our retainer guide explains how long and which type. The smile gallery includes upper arch expansion cases treated at Align. Individual results vary.
What it costs
An expander phase for a child is usually a smaller course than full braces. As a guide, comprehensive treatment in Sydney is commonly quoted at roughly $4,500 to $8,000 for metal braces and $6,000 to $9,000 for Invisalign. You get a written quote after an examination, with payment plans across treatment; see the Sydney braces cost guide.