When the lower front teeth bite ahead of the upper front teeth, biting through food can be difficult, and the appearance of the lips and jawline in profile can be a concern. Treatment of Class III malocclusion aims not only to correct this reversed bite, but also to restore a functional bite and create a natural profile.
01 Does an Adult Underbite Always Require Surgery?
“I was told that an underbite requires surgery or tooth extractions.” This is something we often hear from patients with Class III malocclusion. In this condition, the lower jaw or lower dental arch lies relatively far forward, causing the front teeth to bite in reverse.
Class III malocclusion can involve not only tooth position, but also differences in the size and position of the upper and lower jaws. When the jaw discrepancy is large and tooth movement alone cannot adequately improve the bite, jaw surgery may be considered.
However, not every Class III case requires surgery. In some cases, widening a narrow upper jaw and moving the lower dental arch backward can improve the bite without jaw surgery or premolar extractions.
This case concerns a woman in her twenties who wanted treatment without surgery. We expanded the upper jaw, moved the lower dental arch backward, and finished the bite with Invisalign in a non-surgical, non-extraction treatment approach.
02 Before Treatment
A detailed examination showed a Class III molar relationship on both sides, with the lower dental arch positioned forward and the front teeth in an anterior crossbite. The lower front teeth were 2.5 mm ahead of the upper front teeth. There was also a 2 mm vertical gap between them, indicating an accompanying anterior open bite with no contact between the front teeth.
The upper jaw was also narrow, and the widths of the upper and lower dental arches did not match well. Because the patient did not want surgery, we planned treatment around improvements that could be achieved within the limits of tooth movement and the supporting bone.
Treatment plan: Widening the upper jaw and moving the lower dental arch backward
We first used MARPE, an expansion appliance that widens the upper jaw by anchoring miniscrews in the palate. In adults whose growth has finished, conventional expanders do not readily separate the upper jawbone. MARPE can help by transmitting force directly to the bone.
A study of adults in their early twenties also reported skeletal expansion with separation of the midpalatal suture in approximately 73% of patients treated with MARPE.[1]
During expansion, a facemask was used to pull the upper jaw forward. Bite blocks covering the chewing surfaces of the molars were also fitted to help prevent molar extrusion from increasing the gap between the front teeth during treatment.
Moving the lower dental arch backward requires space behind the molars. To create this space, all four wisdom teeth (#18, 28, 38, and 48) were removed.
Two orthodontic miniscrews were placed in the supporting bone near the lower molars and used as anchorage to move the entire lower dental arch backward. Studies of miniscrew-assisted lower-arch distalization have reported both backward movement of the lower molars and retraction of the lower lip.[2]
Extraction of lower premolars was considered at the beginning of treatment. However, sufficient backward movement was achieved using the miniscrews, allowing treatment to proceed without those extractions.
03 Two Treatment Phases over About Two and a Half Years
Treatment ran from April 28, 2022, to October 21, 2024, for approximately two and a half years. We first addressed the overall arch relationship through upper-jaw expansion and lower-arch distalization, then used Invisalign to refine the contact between the front teeth and molars.
Phase 1: Upper-jaw expansion and lower-arch distalization (April 2022–February 2023)
- April 2022: MARPE, facemask, and bite blocks fitted
- June 2022: Upper-jaw expansion completed
- July 2022: Fixed appliances fitted to the lower teeth; two miniscrews placed and distalization started
- February 2023: MARPE and the lower fixed appliances removed
Phase 2: Finishing the bite with Invisalign (March 2023–October 2024)
- First Invisalign series (March 2023): 30 upper stages and 46 lower stages
- Second Invisalign series (September 2023): 21 stages for both arches
- Third Invisalign series (March 2024): 13 stages for both arches
During the Invisalign phase, Class III elastics continued to apply force to move the lower arch backward. These were alternated with vertical elastics to bring the upper and lower teeth into contact. By comparing the planned movements with the actual tooth response, we refined areas that needed further adjustment through two additional aligner series.
04 Results: The Reversed Front Bite Was Corrected
Before treatment, the lower front teeth were 2.5 mm ahead of the upper front teeth. After treatment, this improved to a normal relationship with the upper front teeth approximately 1.5 mm ahead of the lower front teeth. The 2 mm vertical gap was also closed, with the upper front teeth overlapping the lower front teeth by approximately 1.5 mm.
Upper-jaw expansion brought the widths of the two arches into better harmony, while backward movement of the lower arch improved the molar relationship. Treatment without premolar extractions preserved the arch width and restored the ability to bite through food with the front teeth.
05 Retention after Treatment
After Class III treatment, it is important to keep checking whether the front teeth maintain their bite. Forward movement of the lower teeth or extrusion of the molars can affect the bite.
At the end of treatment, fixed retainers were bonded to the inner surfaces of the upper and lower teeth from canine to canine. Vivera removable retainers were also prescribed.
The teeth and bite have since been monitored at regular check-ups. The front-tooth contact and molar relationship have remained satisfactory to date.
06 Accurate Diagnosis Can Make Non-Surgical Underbite Treatment Possible
Class III malocclusion does not always require surgery. It is important to assess the width and position of the upper jaw, the amount of supporting bone available for backward movement of the lower arch, and the range of improvement that tooth movement can achieve.
In this case, upper-jaw expansion with MARPE, miniscrew-assisted lower-arch distalization, and Invisalign finishing improved the anterior crossbite and overall bite without jaw surgery or premolar extractions.
The same approach cannot be used for every Class III case. Surgery may be more appropriate when the jaw discrepancy is large. However, when a precise diagnosis establishes the limits of achievable correction, non-surgical orthodontics can be a treatment option worth considering.
Photograph dates: April 8, 2022–October 21, 2024
※ Results in this case may differ according to an individual’s skeletal form, tooth and periodontal condition, and adherence to wearing the appliances and elastics. Treatment methods should be determined through a detailed examination and diagnosis by an orthodontic specialist.
References
- [1] Ryu S, Choi EHA, Liu J, Choi SH, Yu HS, Cha JY. Comparison of skeletal and dentoalveolar effects of tooth-and-bone-borne and bone-borne miniscrew-assisted rapid palatal expansion in young adults. Korean J Orthod. 2026;56(1):11-20. doi:10.4041/kjod25.055.
This study analyzed 34 adults with a mean age of approximately 22 years. Both types of MARPE produced skeletal expansion with separation of the midpalatal suture in approximately 73% of patients.
- [2] Setvaji NR, Sundari S. Evaluation of treatment effects of en masse mandibular arch distalization using skeletal temporary anchorage devices: a systematic review. Cureus. 2024;16(10):e71171. doi:10.7759/cureus.71171.
This systematic review analyzed seven studies on backward movement of the entire lower dental arch using miniscrews or miniplates. All studies reported backward movement of the lower molars and retraction of the lower lip.
