Children’s underbite growth correction, crowded teeth, Invisalign First, arch expansion, treatment period 2 years

Hello

I’ll explain pediatric orthodontic treatment in Apgujeong.

A small lower jaw, or underbite, has two patterns: maxillary overgrowth and mandibular undergrowth. In the former, a device called a headgear is used to suppress maxillary growth, and in the latter, mandibular undergrowth is improved by using orthopedic appliances such as an activator or twin block to encourage the lower jaw to grow forward.

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For either case, the most important thing in pediatric growth correction is timing.

If you start too early, the effect is minimal, and if you start too late, you miss the window.

The optimal time for growth treatment is the <peak growth period>.

That way, you can get the greatest effect in the shortest time.

I have previously written several posts about the MA (mandible advance) function used in Invisalign First pediatric orthodontics for underbite treatment or asymmetry treatment.

Especially if it coincides with a child’s peak growth period, you can get better results even with the same treatment duration. Today, I’ll look at a case of mandibular undergrowth underbite treatment using Invisalign First MA and write about the treatment process and results.

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This is an 8-year-old child who visited two years ago for orthodontic treatment.

They had just started losing their primary front teeth and their permanent front teeth were beginning to come in, but

the parents came in after being surprised that the front teeth were already coming in severely crowded.

They had already visited several other dental clinics, and each clinic gave different advice about when to start and what treatment method to use.

If there is too little space at this age, the teeth may erupt rotated, erupt toward the palate, or come in as crowded teeth like this child’s.

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There is also a lot of space shortage in the lower teeth.

Based on skeletal analysis, the diagnosis was underbite with mandibular undergrowth, and the treatment goals were:

• Resolve crowding through arch expansion
• Induce mandibular growth with the MA function

These two goals. A hand X-ray growth plate analysis showed that the peak growth period was just beginning, so the timing was very good. I recommended Invisalign First, and treatment began.

The treatment plan is divided into two stages: the first half, which focuses on arch expansion and resolving crowding, and the second half, which uses MA to induce mandibular growth.

The first-half appliance count was 23, with about 6 months expected

and the second half was the MA stage from step 24 to step 53.

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Severe crowding such as the canines should not be included in the appliance like this; it is better to move only the neighboring teeth to create space.

The goal is to guide them to naturally find their correct position as they come down.

This is the result after completing the first half of treatment over 6 months from June to November 2023.

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The front crowded tooth is coming down well into the space secured through arch expansion.

The arch widened through arch expansion

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The lower front teeth have also been aligned, and the lower canine is already coming up well into position.

Now we enter the MA stage, which begins the lower jaw growth in earnest.

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If you look at the blue arrow area,

The protruding wing-like parts on both sides of the appliance are the wings, and these parts guide the lower jaw into the correct position.

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As shown by the blue arrows in the photo, the upper and lower wings interlock and bite together, positioning the lower jaw forward, and if this overlaps with the peak growth period, it can also guide mandibular growth.

From November 2023 to July 2024, the MA stage was completed while wearing all the way through the final 53rd appliance.

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The midline is well aligned.

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Meanwhile, many of the remaining primary teeth have fallen out, and permanent teeth are coming in.

To allow the permanent teeth to erupt a little more, we took a 5-month break from July to December 2024.

The last appliance worn was kept only at night as a retainer.

A remake was made in December, and the second set of appliances totals 22.

In June 2025, treatment was finally completed.

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The midline is well aligned.

The bite will stabilize once the premolars come down a bit more.

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There are no remaining primary teeth, and the patient has entered a full permanent dentition.

It has reached a level where secondary orthodontic treatment may not be necessary later.

To maintain the good results for a long time, we carefully used both a wire-fixed retainer and a removable retainer.

The total treatment period was 2 years, and the break in the middle was 5 months.

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The root parallelism is good, and there is no root resorption.

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The measurement indicating underbite decreased from 6.4 to 4.7 compared to the beginning.

4.7 is within the normal range for this age group.

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Let’s overlay the skeletal changes over the two years.

The lower jaw grew forward significantly, and desirable growth occurred without lengthening the lower face.

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Beautiful smile line

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Beautiful smile line

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Resolution of the underbite

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The improvement in the jawline is noticeable.

I hope this post is helpful for those considering pediatric orthodontic treatment.