Condition category
Oral Health
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status
Not yet recruiting

Plain English Summary

Background and study aims
Prominent upper front teeth are associated with poor appearance, inadequate function and psychosocial problems (12.8% prevalence of bullying in adolescents). There is also double the risk of trauma to the teeth and this has been calculated at a global level to 235 million traumatic injuries to teeth.
Bite blocks are removable braces frequently used in treating prominent upper front teeth in adolescents. Whilst patients who wear removable biteblocks on a full-time basis in the presence of active growth inevitably show an excellent treatment result, those who do not wear them as required unfortunately are unsuccessful with treatment. The solution to the problem of compliance is to develop a fixed biteblock appliance that is effective and value for money. The compliance, comfort and speed of treatment with fixed bite block brace treatment remains to be tested.

The aim of our study is to investigate the speed of correction of the overjet (upper front teeth prominence) comparing the fixed and removable Twinblock appliance for correction of prominent upper front teeth, as well as the patient centred psychoscocial aspects of treatment and psychological impact of the associated soft tissue facial changes.

Who can participate?
Children aged 9 – 14 years

What does the study involve?
In this study the participant will either have the fixed or the removable Twinblock fitted to correct their bite. We will then measure how quickly teeth move and how long treatment takes. We are also interested in how jaws and muscles adapt with this brace. To investigate this we will take laser light scans of the teeth, 3D photographs of the face and ask participants to fill in short questionnaires to find out about their experience.

What are the possible benefits and risks of participating?
The outcomes of this study are clinically relevant with major dental health and financial benefits for the population and by investigating if a fixed version of an existing removable appliance can circumvent the issues with compliance and also speed up treatment, hence indirectly assessing cost effectiveness. The study could potentially maximise correction of the malocclusion during growth and negate the challenges of dental trauma and malocclusion associated psychsocial problems in adolescents.
The material used to make this brace has been shown to be safe and is standard laboratory clinical material. Sometimes during the course of brace treatment, participants can be faced with problems related to their treatment. This may require prompt treatment, resulting in unscheduled visits. Also, as the fixed twinblock is a new device, it may not work and if that is the case, the Orthodontist will remove the device and the participant will revert back to standard treatment (removable twinblock).

Where is the study run from?
NHS Tayside (UK)

When is the study starting and how long is it expected to run for?
September 2017 to June 2024

Who is funding the study?
British Orthodontic Society Foundation

Who is the main contact?
Gautham Sivamurthy,

Trial website

Contact information



Primary contact

Mr Gautham Sivamurthy


Contact details

School of Dentistry
University of Dundee
Park Place
United Kingdom
+44 (0)1382 381607



Additional contact

Mr Gautham Sivamurthy


Contact details

School of Dentistry
University of Dundee
Park Place
United Kingdom
+44 (0)1382 381607

Additional identifiers

EudraCT number

Nil known number

Nil known

Protocol/serial number

IRAS 276650

Study information

Scientific title

Fixed versus conventional removable Twinblock for overjet reduction in children – A randomised clinical trial to investigate the burden of care



Study hypothesis

There is no difference between the fixed and removable twinblocks in speed of overjet reduction and skeletal, dental and soft tissue contributions in correction.

Ethics approval

Approval to be submitted to East of Scotland Research Ethics Service in January 2021

Study design

Multicentre randomized clinical trial with two-arm parallel design

Primary study design


Secondary study design

Randomised parallel trial

Trial setting


Trial type


Patient information sheet

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


Functional treatment of Class II division 1 malocclusions


The study will have 2 parallel arms. One group will be treated with the removable twinblock appliance and the other group will be treated with fixed twinblock appliance. Following completion of the Twinblock treatment, all participants will continue treatment with fixed orthodontic appliance (train-track braces), which is standard treatment protocol following completion of twinblock treatment. Both groups will be followed up until end of treatment, which can vary for each patient depending on the severity of their initial dental condition. Usually, such clinical treatment varies between 18 - 24 months.
Randomisation will be stratified by gender, overjet measurement and site, using an on-line randomisation system which provides GCP compliant web-based randomisation to produce balanced randomisation allocation based on a minimisation with stratification algorithm.

Intervention type



Not Applicable

Drug names

Fixed Twinblock
Removable Twinblock

Primary outcome measure

Overjet correction measured by clinical measurement in millimetres at baseline, 3 months, 6 months, 9 months, end of twinblock treatment and end of fixed orthodontic treatment

Secondary outcome measures

1. Skeletal contributions to overjet correction by radiographic measurement (lateral cephalogram) at baseline, end of twinblock treatment and towards end of fixed orthodontic treatment
2. Dental contributions to overjet correction by 3D model measurements at baseline, end of twinblock treatment and end of fixed orthodontic treatment
3. Soft tissue contributions to overjet correction by 3D stereophotogrammetric measurements at baseline, end of twinblock treatment and end of fixed orthodontic treatment
4. Patients’ perception and experience by using three questionnaires to assess the perception of fixed orthodontic therapy before, during and after treatment

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Class II division 1 malocclusion
2. No history of active orthodontic treatment
3. Overjet > 6mm (IOTN 4a/5a)
4. Age 9 - 14 years
5. Child & parent/carer who are able to assent and consent, respectively

Participant type


Age group




Target number of participants


Participant exclusion criteria

1. Overjet <6mm
2. Mobile/loose deciduous teeth
3. Profound hypodontia affecting the incisor region (>1 missing tooth per quadrant)
4. Subjects taking growth hormone or endocrine disorders
5. Suspected or identifiable syndromes
6. Subjects with cleft lip and palate
7. Anterior open bite

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Ninewells Hospital and Medical School
NHS Tayside James Arrott Drive
United Kingdom

Sponsor information


University of Dundee

Sponsor details

TASC R&D office
Ninewells Hospital and Medical School
United Kingdom
+44 (0)1382 383877

Sponsor type




Funder type


Funder name

British Orthodontic Society Foundation

Alternative name(s)

British Orthodontic Society, The BOSF, BOSF

Funding Body Type

private sector organisation

Funding Body Subtype

Trusts, charities, foundations (both public and private)


United Kingdom

Results and Publications

Publication and dissemination plan

Peer reviewed journal publication and presentation at scientific meetings will be prepared to disseminate the data analysed at the end of Twinblock appliance treatment, in addition to using the final clinical trial report for publication in peer reviewed open access journals and presentation at scientific meetings.

IPD sharing statement:
All data generated or analysed during this study will be included in the subsequent results publication.

Intention to publish date


Participant level data


Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes

13/01/2021: Trial’s existence confirmed by British Orthodontic Society