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

This study is ongoing, but not recruiting participants.
Information provided by (Responsible Party):
Carlos Flores-Mir, University of Alberta, Graduate Orthodontic Program Identifier:
First received: February 7, 2012
Last updated: May 3, 2017
Last verified: May 2017

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
Malocclusion, Angle Class II Device: Brackets plus Forsus springs Device: Xbow plus full brackets

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single (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 Carlos Flores-Mir, University of Alberta, Graduate Orthodontic Program:

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

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

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

Enrollment: 54
Study Start Date: October 2012
Estimated Study Completion Date: December 2019
Estimated Primary Completion Date: December 2017 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Active Comparator: Full brackets plus Forsus springs
Standard of care - Class II springs used after le el and alignment.
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 - First use the Xbow appliance and then full brackets after Class II occlusion has been corrected.
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   (Child)
Sexes Eligible for Study:   All
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
Edmonton, Alberta, Canada, T6G 1C9
Sponsors and Collaborators
University of Alberta, Graduate Orthodontic Program
Principal Investigator: Carlos Flores Mir, DDS, FRCD(O) University of Alberta
  More Information

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: May 3, 2017
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: No

Keywords provided by Carlos Flores-Mir, University of Alberta, Graduate Orthodontic Program:
Malocclusion, Angle Class II

Additional relevant MeSH terms:
Malocclusion, Angle Class II
Tooth Diseases
Stomatognathic Diseases processed this record on September 21, 2017