3D Changes Comparing the Crossbow Appliance and Later Full Fixed Brackets Against Simultaneous Use of Full Fixed Brackets Plus Forsus Springs Among Mild to Moderate Class II Malocclusion Cases: A Randomized Clinical Trial.

Class II malocclusion (mismatch between the upper and lower jaw in which the lower jaw appears to be smaller from a profile point of view) are common in the general population. Around 1/3 of the population have some degree of this skeletal/dental problem and it is one frequent reason why patients decide to undergo orthodontic treatment. Treatment alternatives will basically depend on the facial skeletal development of the patient and also on the magnitude of the skeletal/dental discrepancy.

For patients that are not yet fully skeletal mature, the treatment of mild to moderate Class II malocclusion involves a combination of a small skeletal growth modification effect and more significant dental movements. For skeletal mature individuals with a severe mismatch, the treatment usually involves jaw surgery to fully correct the malocclusion. For less severe cases orthodontic camouflage exclusively done by orthodontic movements is an option.

If the case is not severe enough to warrant a surgical approach there are several treatment alternatives. One of the most commonly used options is the use of orthodontic loaded springs that apply forces through brackets and arch wires bonded into the teeth so that the teeth will interrelate better.

A different alternative was proposed some years ago. The Xbow (spelled Crossbow) appliance differs from the above-proposed option in that no brackets are bonded or arch wires used. The orthodontic springs are applied to a metal framework cemented on some upper and lower teeth. Once the skeletal/dental problem is believed to have been significantly improved, fine tuning of the remaining dental problems is managed with brackets and arch wires. The theoretical advantage of such a design is that adverse effects, such as root resorption and decalcification from the long-term use of brackets and arch wires, are theoretically minimized as the brackets and arch wires have to be used for a shorter period of time.

Although there are some retrospective reports about the skeletal and dental effects of the Xbow appliance and only one prospective trial comparing the skeletal and dental changes to a non-treated growing sample; no randomized clinical trial has yet evaluated the changes compared to a current standard of care alternative which is the simultaneous use of loaded springs concurrent with brackets and arch wires.