Condition category
Oral Health
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting

Plain English Summary

Background and study aims
Orthodontic treatment with fixed braces is used to improve the appearance, position and function of crooked or abnormally arranged teeth. Fixed braces are made up of brackets that are glued to each tooth and linked with wires. Conventional (non-self-ligating) brackets use an elastic module to hold the wire in place, whereas self-ligating brackets do not. The aim of this study is to compare the results of these two types of orthodontic bracket, looking at changes in the width of the lower tooth arch.

Who can participate?
Patients aged between 11 and 21 who require fixed braces.

What does the study involve?
Participants are randomly allocated into one of the two groups. Each group is treated with braces with a different bracket system, either self-ligating brackets or non-self-ligating brackets. A questionnaire is used to assess patient pain and anxiety, and any appliance breakages are recorded.

What are the possible benefits and risks of participating?
Not provided at time of registration

Where is the study run from?
Queen Alexandra Hospital (UK)

When is the study starting and how long is it expected to run for?
December 2011 to December 2013

Who is funding the study?
Investigator initiated and funded

Who is the main contact?
Dr Becky Walker

Trial website

Contact information



Primary contact

Dr Becky Walker


Contact details

Orthodontic Department
Queen Alexandra Hospital
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

A comparison of mandibular archwidth changes using two different bracket systems: a randomised controlled clinical trial


Study hypothesis

Null hypothesis:
There is no significant difference in archform changes between self-ligating brackets and non-self ligating brackets using super elastic nickel titanium archwires

Ethics approval

NRES Committee South Central - Oxford A, 12/10/2011, ref: 11/SC/0421

Study design

Randomised controlled trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting

GP practices

Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet


Orthodontics – mandibular archform


Patients will be randomised into one of the two arms of study. Each arm of study will use a different bracket system, either:
1. Self-ligating brackets (Damon Q)
2. Non self-ligating brackets

Treatment will then proceed with both bracket systems using the same archwire sequence:
1. 0.014 inch round NiTi archwire
2. 0.014x 0.025 inch Damon Copper NiTi archwire
3. 0.018x 0.025 inch Damon Copper NiTi archwire

Intervention type



Not Applicable

Drug names

Primary outcome measure

Mandibular archwidth changes
1. Alginate impressions for study models of the maxillary and mandibular arches will be taken at:
T0: Before placement of fixed appliances, at the start of treatment.
T1: Removal of 0.014 inch round NiTi archwire and placement of 0.014 x 0.025 inch NiTi archwire
T2: Removal of 0.014 x 0.025 inch NiTi archwire and placement of 0.018 x 0.025 inch NiTi archwire
T3: Removal of 0.018 x 0.025 inch NiTi archwire and placement of next archwire
These study models will be used to measure mandibular archwidth between the 2 groups at T0, T1, T2, and T3 measured at 4 places across arch (c-c, p1-p1, p2-p2, m-m).

2. Arch width measurements (from study models)
c-c: Intercanine width: distance between the mandibular canine tips or between the central fossae on the surfaces in case of worn cusps
p1-p1: First inter premolar width: distance between the central fossae on the occlusal surfaces of the maxillary first premolars
p2-p2: Second inter premolar width: distance between the central fossae on occlusal surfaces of the maxillary second premolars
m-m: Intermolar width: distance between the mesial ends of the central fissures on the occlusal surfaces of the maxillary first molars

Measurement for the inter arch distances will be measured in mm using fine-pointed digital callipers. The measurements will be approximated to the first decimal place.

All measurements will be carried out by a single investigator to avoid inter-operator error. Intra-operator reliability will be assessed by repeating measurements on 10 study casts 2 weeks apart and carrying out an error analysis.

Secondary outcome measures

1. Pain perception will be recorded using a pain questionnaire, to be completed by patients following each archwire change at:
1.1. 2 hrs
1.2. 6 hrs
1.3. Bedtime on day of appointment
1.4. When they wake up the day after their appointment
1.5. When they wake up 2 days after their appointment
1.6. When they wake up 3 days after their appointment
2. Anxiety experienced will be recorded using an anxiety questionnaire, to be completed by participant at end of appointment
3. Any appliance breakages during treatment will be recorded

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Aged between 11 and 21 years of age
2. In the permanent dentition
3. Requiring upper and lower fixed appliances
4. Receiving treatment in the lower arch on a non-extraction basis
5. With mild lower arch crowding
6. All malocclusions

Participant type


Age group




Target number of participants

The target total recruitment of participants for the trial is 86 patients

Participant exclusion criteria

1. Impacted teeth in the lower arch
2. Hypodontia in the lower arch
3. Extractions in the lower arch

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Queen Alexandra Hospital
United Kingdom

Sponsor information


Queen Alexandra Hospital (UK)

Sponsor details

c/o Mrs Kate Greenwood
Research and Development
Gloucester House
United Kingdom

Sponsor type

Hospital/treatment centre



Funder type


Funder name

Investigator initiated and funded

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes

28/02/2018: No publications found, verifying study status with principal investigator. 21/01/2016: Plain English summary added