Crossbow Versus Forsus Springs in Mild to Moderate Class II Malocclusion Cases

This study is currently recruiting participants. (see Contacts and Locations)
Verified December 2014 by University of Alberta, Graduate Orthodontic Program
Information provided by (Responsible Party):
Carlos Flores-Mir, University of Alberta, Graduate Orthodontic Program Identifier:
First received: February 7, 2012
Last updated: December 23, 2014
Last verified: December 2014

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.

Condition Intervention Phase
Malocclusion, Angle Class II
Device: Brackets plus Forsus springs
Device: Xbow plus full brackets
Phase 4

Study Type: Interventional
Study Design: Allocation: Randomized
Endpoint Classification: Safety/Efficacy Study
Intervention Model: Parallel Assignment
Masking: Single Blind (Outcomes Assessor)
Primary Purpose: Treatment
Official Title: 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.

Further study details as provided by University of Alberta, Graduate Orthodontic Program:

Primary Outcome Measures:
  • Facial soft tissue, dental and skeletal changes [ Time Frame: 24 months ] [ Designated as safety issue: Yes ]
    Outcomes to be measured from Computer Beam Computer Tomography data and dental casts.

Secondary Outcome Measures:
  • Root resorption [ Time Frame: 24 months ] [ Designated as safety issue: Yes ]
    Evaluation of the magnitude of external root resorption as quantified/qualified from the CBCT data.

  • Enamel decalcification [ Time Frame: 24 months ] [ Designated as safety issue: Yes ]
    Enamel decalcification as clinically determined by observing and touching the enamel surfaces of teeth.

Estimated Enrollment: 50
Study Start Date: October 2012
Estimated Study Completion Date: June 2017
Estimated Primary Completion Date: June 2017 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Active Comparator: Full brakets plus Forsus springs
Standard of care.
Device: Brackets plus Forsus springs
Full brackets and after completion of level and alignment insertion of Class II correctors (Forsus spring devices).
Other Name: Forsus™ Fatigue Resistant Device
Experimental: Xbow plus full brackets
Alternative treatment
Device: Xbow plus full brackets
Xbow appliance to be inserted first. After anteroposterior changes have been completed full brackets will be bonded and occlusion fine tuned
Other Name: Xbow Class II corrector

  Show Detailed Description


Ages Eligible for Study:   11 Years to 15 Years
Genders Eligible for Study:   Both
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Participants will be of either gender between 11 and 15 years-of-age.
  • They will have mild to moderate Class II division 1 malocclusions.
  • Late mixed dentition or early permanent dentition.

Exclusion Criteria:

  • Severe vertical growth tendency or syndromic cases.
  • Craniofacial growth completed.
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its identifier: NCT01530516

Canada, Alberta
Edmonton Clinic Recruiting
Edmonton, Alberta, Canada, T6G 1C9
Contact: Susan Helwig   
Principal Investigator: Carlos Flores-Mir, DSc         
Sponsors and Collaborators
University of Alberta, Graduate Orthodontic Program
Principal Investigator: Carlos Flores Mir, DDS, FRCD(O) University of Alberta
  More Information

No publications provided

Responsible Party: Carlos Flores-Mir, Professor and Division Head of Orthodontics, University of Alberta, Graduate Orthodontic Program Identifier: NCT01530516     History of Changes
Other Study ID Numbers: Pro00021423 
Study First Received: February 7, 2012
Last Updated: December 23, 2014
Health Authority: Canada: Health Canada

Keywords provided by University of Alberta, Graduate Orthodontic Program:
Malocclusion, Angle Class II

Additional relevant MeSH terms:
Malocclusion, Angle Class II
Stomatognathic Diseases
Tooth Diseases processed this record on February 08, 2016