Your smile is unique, from the alignment of your teeth to the shape of your gum line. One feature that is often overlooked? Lower jaw width. A narrow lower jaw can inject a little extra character into a smile — but it can also cause oral and general health problems.
Palate expanders are the default treatment for narrow upper jaws, but are they effective on the lower jaw? We have all the details you need to understand lower jaw expansion.
Table of Contents
What Is a Palatal Expander?
When the upper jaw is narrow enough to cause bite, alignment, or breathing problems, you have to widen it. Typically, this requires palatal expanders. These appliances are customized for each patient and use pressure to expand the palate.
Also known as palate expanders and orthodontic expanders, these appliances have been around for nearly 200 years. Most often prescribed for children and teens whose jaws are still growing, orthodontists sometimes use them with adult patients, too.
How Do Palatal Expanders Work?
To understand how palate expanders work, you need to understand the anatomy of the upper jaw. At birth, we have 300 bones. By the time we’re fully grown adults, we have just 206. This is because some bones fuse together as we age. The upper jaw is just one spot where smaller individual bones fuse, becoming one larger bone.
At birth, the upper jaw has two maxillary bones, one on each side, connected by the intermaxillary suture — a fibrous joint made mostly of collagen. During the middle teen years, these three elements fuse and become one structure, called the maxilla.
Expanders function by placing pressure on the maxillary bones — typically via the back molars — widening the jaw. In most cases, orthodontic expanders have two halves connected by a jackscrew, which the patient or their parent needs to turn on a set schedule. Each turn widens the expander and, in turn, the jaw. Expanders function well on their own in children and young teens, but older teens and adults often require surgical intervention as well.
Skeletal vs. Dental Expansion
Palate expansion can take two forms: skeletal and dental. Skeletal expansion is an orthopedic correction that moves the upper jaw bones apart, which can seem like the teeth moved, too. But this is just because the teeth are anchored in the jawbones, where the actual movement takes place. Palatal expander treatment aims for skeletal expansion and succeeds primarily in children and younger teens. After the maxilla fuses, skeletal expansion often requires surgical intervention.
Dental expansion occurs when the teeth move within the jawbones, and the bones themselves may or may not move simultaneously. Palatal expanders typically achieve dental, but not skeletal, expansion in adults and older teens — unless they’re paired with some form of surgery. Unfortunately, there is a limit to how far dental expansion can go, since there is a fine line between good expansion and putting the teeth in an unhealthy position outside of the bone.
Can You Expand the Lower Jaw?
You might have noticed that all the info above relates to the upper jaw — but this article is about palate expanders for the bottom arch. So why the focus on the top jaw?
Because palate expanders are designed specifically for the upper jaw. Lower arches can achieve expansion, but it looks different than it does in the upper jaw.
How the Upper and Lower Jaw Differ
As explained above, the upper jaw has two maxillary bones and an intermaxillary suture, and these three parts fuse in adolescence to form the maxilla. That suture is what makes palatal expanders effective on the upper jaw. Even if yours fused many years ago, you can still feel this line on the top of your mouth if you run your tongue along it.
Like the upper jaw, the lower jaw starts out as multiple bones. However, it fuses within the first year of life, forming the solid mandible. The mandible still has two parts — the body and the ramus — but they’re firmly connected. There is no soft suture work with.
Why Skeletal Expansion Isn’t Possible in the Lower Jaw
The suture is the anatomical feature that makes upper jaw expansion possible without surgery. When the cartilage is still soft, an expander can stretch it and hold it in place until it fuses with the jawbones. Because the lower arch lacks this suture, palatal expanders can’t widen it the same way.
What Lower Jaw Expansion Accomplishes
Lower jaw expansion is strictly tooth movement unless aided by surgery — and even then, the expansion will likely come from the surgery itself, not an expander. An orthodontic expander can correct teeth that have tipped inward, or push them over the edge of the supporting bone (called flaring) as needed to address issues like crowding.
This is only considered safe and effective if you have sufficient bone and gum tissue. As a dental expansion, it’s more limited than skeletal expansion.
Alternatives to Lower Jaw Expanders
Because palatal expanders are considered limited in their effectiveness on the lower jaw, in most cases, alternative treatments will provide a better outcome. Some possibilities to discuss with your orthodontist include:
- Braces: Since expanders can only cause dental expansion in the lower arch, braces are often a superior alternative. Designed to move the teeth, they usually offer more comprehensive and controlled results while also addressing alignment issues.
- Space Maintainers: This option only works for children. Space maintainers hold spaces open after the baby teeth fall out, making more room for the adult teeth.
- Teeth Extraction: If altering the position of the teeth or holding space for them isn’t enough, extraction might be the best solution, creating room for the teeth to come into better alignment and eliminating impaction.
- Jaw Surgery: If skeletal expansion is essential, surgery is the only solution. The surgeon will make cuts directly into the jawbone, then forcibly expand it so it can heal strong and solid but wider than before.
- Lip Bumpers: These appliances are usually small thin wires that are covered in a plastic material. They create more space in the lower arch so the teeth can come into proper alignment.
- Sagittal Appliances: These tools move poorly positioned molars, which helps eliminate crowding and free impacted teeth without expanding the jaw itself.
Final Thoughts
Palatal expanders are made to widen the upper arch — not the lower one. While they can fit the bottom jaw, they will only achieve dental, not skeletal, expansion. So, they’re not always the right treatment for correcting conditions related to a narrow mandible.
You and your orthodontist might decide expanders are still the right choice, but it’s worth asking about the alternatives.
Frequently Asked Questions
How do orthodontic expanders widen the jaw?
They place pressure on the molars. On your upper palate, this can push the bones apart since the teeth are embedded in the jaw. On the lower jaw, expanders just push your teeth toward the edge of the gum line and potentially help tilt them in the right direction.
Why is lower jaw expansion difficult?
Upper palate expansion works because it isn’t one solid structure until the middle teen years, and even after that, surgery can manipulate the mid-palatal suture easily enough. The mandible fuses in infancy, and it doesn’t have a seam like the upper jaw. This means surgically implanted expanders won’t work the way they do after fusion in the upper jaw.
Can an expander still help with a narrow lower jaw?
It can’t adjust the jaw itself, but it can alter the placement of the teeth enough to help some people. However, consider alternative appliances and treatments that will deliver more comprehensive results first.
Does it take a long time to adjust to wearing a palatal expander?
In most cases, it takes 3–7 days to adjust eating and speaking habits to accommodate an expander. People typically adjust to expanders on the lower arch faster than ones on the upper arch, since they interfere less with tongue movement.
Should I expect my palate expander to hurt?
Genuine pain is a sign that something is wrong, but soreness and irritation are normal with pretty much all orthodontic appliances. This discomfort is most pronounced right after getting the expander, but can return briefly with each adjustment.
Will I need to avoid certain foods when I have a palate expander?
Hard and sticky foods can damage or dislodge palate expanders, which can lead to recession, so you’ll need to avoid them throughout treatment.
How long does palate expander treatment take?
It depends on numerous factors, from your age to how well you remember to adjust your expander. It can take as little as a few months to more than a year.
What results should I expect from palate expansion?
It depends on the corrections you need, which jaw you’re treating, your age, and how your body responds to treatment. Ask your orthodontist what you should expect prior to starting treatment.
What are the typical side effects of palate expanders?
- Jaw soreness
- Tooth soreness
- Sinus pressure
- Headaches
- Speech changes
- Increased saliva production
- A gap between the two front teeth
What do I do if I lose the key to turn my expander?
Talk to your dentist or orthodontist. They can give you a new one. If you lose it over the weekend, you should be fine to skip a day or two.
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