Skeletal Effects of Three Functional Appliances in Adolescents With Skeletal Class II Malocclusion: A Retrospective Comparative Study
This retrospective comparative study found that while Van Beek Activator, Twin-Block, and Angelalign A6 appliances produced comparable overall skeletal and soft tissue outcomes in adolescents with skeletal Class II malocclusion, the Twin-Block and Angelalign A6 achieved greater Wits appraisal improvement whereas the Van Beek Activator offered superior control of lower incisor proclination, supporting appliance selection based on specific treatment objectives.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
For many children, the lower jaw simply does not grow forward enough to meet the upper jaw, creating a bite where the top teeth sit too far ahead of the bottom ones. This condition, known as a skeletal Class II malocclusion, is one of the most common facial development issues seen in growing patients. While the jaw is still developing, orthodontists often use special devices called functional appliances to guide growth. These devices work by holding the lower jaw in a forward position, encouraging the jawbone to grow in that direction and eventually aligning the bite. The timing of this treatment is critical; it is most effective when a child is in the midst of their pubertal growth spurt, a period when the body is naturally primed for rapid skeletal change.
For decades, the standard tools for this job have been bulky, removable plastic and acrylic devices that patients must wear for many hours a day. However, recent advances in digital technology have introduced a new option: clear aligners designed not just to straighten teeth, but to also push the lower jaw forward. This innovation promises the same growth guidance as traditional devices but with the added benefits of being nearly invisible and more comfortable to wear. The question for clinicians and patients has been whether these sleek, modern aligners can truly match the bone-shaping power of the older, more established appliances, or if the traditional methods remain superior for changing the actual structure of the face.
A team of researchers at the Stomatological Hospital of Southern Medical University in Guangzhou, China, set out to answer this question by looking back at the treatment records of 126 adolescents. These patients, all between the ages of roughly nine and eleven, had been treated for their underdeveloped lower jaws using one of three different methods. The first group used a Van Beek Activator, a traditional device that covers the teeth and is worn alongside a headgear strap that pulls upward on the upper jaw. The second group used a Twin-Block appliance, another classic device consisting of two separate blocks that slide against each other to push the jaw forward. The third group used the Angelalign A6, a clear aligner system that incorporates special wings to hold the jaw forward while simultaneously moving the teeth into place.
The researchers carefully examined X-rays taken before treatment began and immediately after the active phase of treatment ended, which lasted between 12 and 18 months for everyone. To ensure a fair comparison, they accounted for differences in the children's ages, their stage of skeletal maturity, and their starting jaw positions. This statistical adjustment allowed them to isolate the true effect of each device, removing the noise of natural growth variations that might otherwise skew the results. They measured how much the jaw grew, how the teeth tilted, and how the soft tissues of the face changed.
The study found that all three approaches were effective. Every group showed significant improvement in the relationship between their upper and lower jaws, with the lower jaw moving forward and the bite becoming more balanced. When the researchers compared the three groups against each other, adjusting for the starting differences, the overall results were surprisingly similar. In terms of the total amount of skeletal change achieved, the clear aligners performed just as well as the traditional plastic appliances. The study suggests that the new digital option is a viable alternative for changing the shape of the face, not just the position of the teeth.
However, the devices did not act exactly the same way on the teeth. The researchers discovered a distinct difference in how the lower front teeth reacted to the force of the appliances. The Van Beek Activator group showed the best control over the lower incisors, meaning these teeth stayed more upright and did not tip forward as much as they did in the other groups. In contrast, the Twin-Block appliance and the Angelalign A6 allowed for slightly more forward tipping of the lower teeth as part of the correction process. While the clear aligners achieved the same skeletal correction as the Twin-Block, they offered a middle ground in terms of tooth movement, providing more control than the Twin-Block but less than the Van Beek Activator.
These findings suggest that there is no single "best" device for every patient. If a child's primary need is to maximize the forward growth of the jaw and the patient can tolerate wearing a bulky device for long periods, the Twin-Block remains a strong choice. If a patient has lower teeth that are already prone to tipping forward, or if the jawbone at the front is very thin, the Van Beek Activator might be the safer option to prevent the teeth from moving too far forward. For patients who value aesthetics and comfort, the Angelalign A6 offers a compelling alternative, delivering skeletal results comparable to the traditional methods while keeping the teeth aligned and the smile invisible during treatment.
The study also highlighted the importance of individualized care. Because the devices work through slightly different mechanical forces, the choice of appliance should depend on the specific characteristics of the patient's jaw and teeth, as well as their ability to comply with wearing instructions. While the clear aligners offer a modern, comfortable path to correcting a receding jaw, the traditional devices still hold specific advantages for certain clinical situations. Ultimately, the goal is to match the right tool to the right patient, ensuring that the treatment not only straightens the smile but also guides the face to develop in a healthy, balanced way.
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