Key messages
Non-surgical and surgical orthodontic treatments in childhood can improve the bite and jaw position. We do not know how long these effects last.
Future studies should be long enough to discover whether treating patients in childhood prevents the need for jaw surgery in adulthood.
What is 'underbite'?
Prominent lower front teeth ('underbite') can result from the upper jaw (maxilla) being too far back, lower jaw (mandible) too far forward, upper front teeth tipped back, lower front teeth tipped forward, or a combination. Underbite may result in teasing, eating difficulties and jaw joint problems.
How is it treated?
Orthodontic treatment for underbite involves braces fitted inside or outside the mouth and fixed to the teeth, or braces fitted around the head. The braces encourage the upper jaw and top teeth to move forwards and downwards, or restrict the growth of the bottom jaw, or both.
What did we want to find out?
This review, which updates the 2013 version, aimed to find out the effects of orthodontic treatment for underbite in children and adolescents.
What did we do?
We searched for studies that compared one type of brace for underbite to another type or no treatment. We summarised their results, and rated our confidence in the evidence, based on factors such as study methods and sizes.
What did we find?
We found 29 studies, involving 1169 children aged 5 to 13 years when treatment started. Most studies lasted between 5 and 18 months, and assessed outcomes at the end of treatment. Only one study assessed outcomes after the end of treatment. The studies used a wide variety of braces, including the following types.
Facemask: rests on the forehead and chin and is connected to the upper teeth by an expansion appliance – which widens the upper jaw to create more space or correct bite problems – with elastic bands placed by the wearer. The force causes the top teeth and jaw to move forward and downward.
Chin cup: rests on the chin with a strap around the back of the head to reduce forward growth of the lower jaw.
Orthodontic removable traction appliance (ORTA): expansion appliance is placed on the top teeth. Elastic bands, placed by the wearer, run from it to a clear, removable gumshield brace on the lower teeth. The force pulls the top teeth forwards and downwards and the bottom teeth back.
Reverse Twin Block with lip pads and expansion appliance: top and bottom removable braces with an expansion screw in the top brace, blocks of plastic over the side teeth, angled to hold the bottom jaw back, and plastic pads to hold the top lip away from the teeth.
Tandem traction bow appliance: attachments are fixed to top and bottom teeth. The top attachment has a hook on each side. A metal bar is placed in the lower attachment, which sits in front of the lower teeth. An elastic band is placed on each side to pull the top jaw forwards and bottom jaw backwards.
Surgical miniplates: metal plates, fixed to the bone with miniscrews, are placed under the gums during an operation. They have a visible hook from which elastic bands are placed by the wearer between the top and bottom jaws or to a facemask.
Main results
Combining studies, we found that non-surgical orthodontic treatments and surgical orthodontic treatment with miniplates can substantially improve the bite and the jaw relationship, immediately after treatment.
Only one study, which assessed facemask, looked at long-term effects of braces. Improvements in the bite and jaw position were seen after three years, but appeared to have been lost by six years. Nevertheless, orthodontists judged that children who had received facemask treatment were less likely to need jaw surgery in adulthood than those who did not have this treatment. More long-term studies are needed to find out how long orthodontic treatment benefits last.
We combined results from studies that compared facemask treatment to other treatments. This did not show the other interventions to be superior to the facemask, but there was a lot of variation in the data, so we cannot draw reliable conclusions.
There may be no advantage to securing facemasks with surgical miniplates, but the evidence is uncertain and further research is needed.
Using a facemask without an expansion appliance may work as well as with an expansion appliance. Alternating between expansion and constriction may be no different than expansion alone. However, the evidence for facemask variations is uncertain. More research is needed to determine the optimal facemask therapy.
What are the limitations of the evidence?
The studies were small and everyone involved knew what orthodontic treatment the children were receiving. Our confidence in the evidence ranged from very low to moderate. We know that non-surgical and surgical orthodontic treatments in childhood can treat underbite effectively, but how long this benefit lasts is uncertain. Whether one orthodontic treatment is more effective than another is also uncertain.
How up to date is this evidence?
The evidence is current to January 2023.
Moderate-certainty evidence showed that non-surgical orthodontic treatments (which included facemask, reverse Twin Block, orthodontic removable traction appliance, chin cup, tandem traction bow appliance and mandibular headgear) improved the bite and jaw relationship immediately post-treatment. Low-certainty evidence showed surgical orthodontic treatments were also effective.
One study measured longer-term outcomes and found that the benefit from facemask was reduced three years after treatment, and appeared to be lost by six years. However, participants receiving facemask treatment were judged by clinicians to be less likely to need jaw surgery in adulthood. We have low confidence in these findings and more studies are required to reach reliable conclusions.
Orthodontic treatment for Class III malocclusion can be invasive, expensive and time-consuming, so future trials should include measurement of adverse effects and patient satisfaction, and should last long enough to evaluate whether orthodontic treatment in childhood avoids the need for jaw surgery in adulthood.
Prominent lower front teeth (Class III malocclusion) may be due to jaw or tooth position or both. The upper jaw (maxilla) can be too far back or the lower jaw (mandible) too far forward; the upper front teeth (incisors) may be tipped back or the lower front teeth tipped forwards. Orthodontic treatment uses different types of braces (appliances) fitted inside or outside the mouth (or both) and fixed to the teeth. A facemask is the most commonly reported non-surgical intervention used to correct Class III malocclusion. The facemask rests on the forehead and chin, and is connected to the upper teeth via an expansion appliance (known as 'rapid maxillary expansion' (RME)). Using elastic bands placed by the wearer, a force is applied to the top teeth and jaw to pull them forwards and downward. Some orthodontic interventions involve a surgical component; these go through the gum into the bone (e.g. miniplates). In severe cases, or if orthodontic treatment is unsuccessful, people may need jaw (orthognathic) surgery as adults. This review updates one published in 2013.
To assess the effects of orthodontic treatment for prominent lower front teeth in children and adolescents.
An information specialist searched four bibliographic databases and two trial registries up to 16 January 2023. Review authors screened reference lists.
We looked for randomised controlled trials (RCTs) involving children and adolescents (16 years of age or under) randomised to receive orthodontic treatment to correct prominent lower front teeth (Class III malocclusion), or no (or delayed) treatment.
We used standard methodological procedures expected by Cochrane. Our primary outcome was overjet (i.e. prominence of the lower front teeth); our secondary outcomes included ANB (A point, nasion, B point) angle (which measures the relative position of the maxilla to the mandible).
We identified 29 RCTs that randomised 1169 children (1102 analysed). The children were five to 13 years old at the start of treatment. Most studies measured outcomes directly after treatment; only one study provided long-term follow-up. All studies were at high risk of bias as participant and personnel blinding was not possible.
Non-surgical orthodontic treatment versus untreated control
We found moderate-certainty evidence that non-surgical orthodontic treatments provided a substantial improvement in overjet (mean difference (MD) 5.03 mm, 95% confidence interval (CI) 3.81 to 6.25; 4 studies, 184 participants) and ANB (MD 3.05°, 95% CI 2.40 to 3.71; 8 studies, 345 participants), compared to an untreated control group, when measured immediately after treatment. There was high heterogeneity in the analyses, but the effects were consistently in favour of the orthodontic treatment groups rather than the untreated control groups (studies tested facemask (with or without RME), chin cup, orthodontic removable traction appliance, tandem traction bow appliance, reverse Twin Block with lip pads and RME, Reverse Forsus and mandibular headgear).
Longer-term outcomes were measured in only one study, which evaluated facemask. It presented low-certainty evidence that improvements in overjet and ANB were smaller at 3-year follow-up than just after treatment (overjet MD 2.5 mm, 95% CI 1.21 to 3.79; ANB MD 1.4°, 95% CI 0.43 to 2.37; 63 participants), and were not found at 6-year follow-up (overjet MD 1.30 mm, 95% CI -0.16 to 2.76; ANB MD 0.7°, 95% CI -0.74 to 2.14; 65 participants). In the same study, at the 6-year follow-up, clinicians made an assessment of whether surgical correction of participants' jaw position was likely to be needed in the future. A perceived need for surgical correction was observed more often in participants who had not received facemask treatment (odds ratio (OR) 3.34, 95% CI 1.21 to 9.24; 65 participants; low-certainty evidence).
Surgical orthodontic treatment versus untreated control
One study of 30 participants evaluated surgical miniplates, with facemask or Class III elastics, against no treatment, and found a substantial improvement in overjet (MD 7.96 mm, 95% CI 6.99 to 8.40) and ANB (MD 5.20°, 95% CI 4.48 to 5.92; 30 participants). However, the evidence was of low certainty, and there was no follow-up beyond the end of treatment.
Facemask versus another non-surgical orthodontic treatment
Eight studies compared facemask or modified facemask (with or without RME) to another non-surgical orthodontic treatment. Meta-analysis did not suggest that other treatments were superior; however, there was high heterogeneity, with mixed, uncertain findings (very low-certainty evidence).
Facemask versus surgically-anchored appliance
There may be no advantage of adding surgical anchorage to facemasks for ANB (MD -0.35, 95% CI -0.78 to 0.07; 4 studies, 143 participants; low-certainty evidence). The evidence for overjet was of very low certainty (MD -0.40 mm, 95% CI -1.30 to 0.50; 1 study, 43 participants).
Facemask variations
Adding RME to facemask treatment may have no additional benefit for ANB (MD -0.15°, 95% CI -0.94 to 0.64; 2 studies, 60 participants; low-certainty evidence). The evidence for overjet was of low certainty (MD 1.86 mm, 95% CI 0.39 to 3.33; 1 study, 31 participants).
There may be no benefit in terms of effect on ANB of alternating rapid maxillary expansion and constriction compared to using expansion alone (MD -0.46°, 95% CI -1.03 to 0.10; 4 studies, 131 participants; low-certainty evidence).