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Trial registered on ANZCTR


Registration number
Help: Registration number
ACTRN12626001151325
Ethics application status
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Approved
Date submitted
Help: Date submitted
28/01/2025
Date registered
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16/09/2026
Date last updated
Help: Date last updated
16/09/2026
Date data sharing statement initially provided
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16/09/2026
Type of registration
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Retrospectively registered

Titles & IDs
Public title
Effects of orthodontic treatment of a small lower jaw in adolescents using Invisalign treatment with Mandibular Advancement with Occlusal Blocks (MA-OB), compared to historical data of a Twin-block orthodontic appliance
Scientific title
Evaluation of efficacy of Align Technology’s Invisalign treatment with Mandibular Advancement with Occlusal Blocks (MA-OB), compared to historical data of a traditional functional appliance, Twin-block, for the treatment of Class II malocclusion in adolescents
Additional trial identifiers [1] 313822 0
Nil known
Universal Trial Number (UTN)
Trial acronym
Related trial records

Health condition
Health condition(s) studied:
Orthodontic Malocclusion 336463 0
Dental overjet 336464 0
Small lower jaw 336465 0
Dental health 336466 0
Condition category
Condition code
Oral and Gastrointestinal 332981 332981 0 0
Normal oral and gastrointestinal development and function

Intervention/exposure
Study type
Interventional
Description of the intervention or exposure
The investigation aims to evaluate the dental and skeletal effects of a clear functional appliance, Invisalign MA-OB, and compare it with historical datasets of a traditional functional appliance (Twin-block) and matched untreated controls (Bolton Brush Growth study legacy).
This is a three-arm study:
Group 1: Experimental group, using the Invisalign MA-OB orthodontic appliance for 25 study participants.
Group 2: Active control group, using historical dataset of a previous clinical trial on the twin-block appliance.
Group 3: Untreated control group derived from the Bolton Brush growth studies.

Collection of records: the following records will be collected at the start and end of the functional treatment phase (equal to or more than 9 months of treatment duration).
a) Intra- and extra-oral photographs
b) Dental impressions (digital image scanning)
c) CBCT radiograph image
d) 3D image face scanning
During the 9-month treatment with the Invisalign MA-OB orthodontic appliance, the initial visit for treatment is 2-weeks post-enrolment, then participants will receive regular orthodontic treatment appointments in 6-weekly intervals. The initial treatment visit is 60-minutes and subsequent visits are 30-minutes.

Patient referrals will be accessed via the Patient Demand & Waitlist Unit at Sydney Dental Hospital (SDH). Further, the participants who satisfy the selection criteria will be contacted via letters to discuss potential participation. They will be provided with additional information and their interest in participation confirmed when they attend a research eligibility screening appointment.

All the interventions which participants will undergo in the study are the standard of orthodontic treatment care in the Orthodontics Department of The Sydney Dental Hospital, Sydney Local Health District (SLHD), NSW. There are no additional procedures which will be carried out solely for research purposes.

Patients will undergo the following processes:
Physical examination: All participants will be assessed for Edward H. Angle’s definition for permanent first molar inter-arch relationship, canine relationship, and overjet and overbite. This assessment is a part of routine orthodontic examination carried out for the orthodontic diagnosis, which also aids in treatment planning. 30 minutes is the duration of procedure and will be carried out by participating patient's treating clinician.
Clinical photographs: Both intra-oral photographs and extraoral photographs are taken at baseline (before treatment) and repeated at every appointment. This is also a routine record-keeping method that not only allows visualization of treatment planning but also, enables the clinician to monitor subsequent changes after orthodontic therapy. 30 minutes is the duration of procedure and will be carried out by participating patients treating clinician.
Dental impressions and bite-registration: The procedure involves making upper and lower teeth moulds and bite registration with a digital scanner. This procedure is routinely done for functional appliance fabrication. 30 minutes is the duration of procedure and will be carried out by participating patients treating clinician.

3D image face scanning: A non-invasive three-dimensional image capturing modality (Bellus3D ARC7 system). This procedure is carried out in 3D for facial scanning in orthodontics for diagnosis and treatment planning. 30 minutes is the duration of procedure and will be carried out by participating patients treating clinician.

Cone-beam computed tomography (CBCT) radiograph image: A low-dose CBCT image will be taken twice – Image 1 will be captured at pre-treatment stage, and Image 2 will be captured at the end of post-functional phase of orthodontic treatment (at or more than 9 months from pre-treatment stage). A low dose CBCT image scans are performed for orthodontic purposes using a large FoV with reduced parameters (400 µm, 2 to 4 mA and low dose protocols). The parameters mentioned are not only acceptable for visualization of large anatomical structures. (Baumann, Bornstein et al. 2022) but also, are very low in dosage which is comparable to the combined imaging dosage of orthopantomography, lateral cephalogram, and two bite-wing radiographs. Values of 4 mA seem to be a sufficient exposure parameter to depict the most relevant anatomical structures of the jaws with acceptable image quality. (Baumann, Bornstein et al. 2022, Ihlis, Kadesjö et al. 2022, Lynds, Kadesjö et al. 2022). These recommendations are according (Ludlow, Timothy et al. 2015) to the ALARA (as low as reasonably achievable) principle and has been modified to the ALADA or ALADAIP principle, which means ‘as low as diagnostically acceptable being indication-orientated and patient-specific’. (Ludlow, Timothy et al. 2015, Oenning, Jacobs et al. 2018). 30 minutes is the duration of procedure and will be carried out by an Expert Radiographer at the Department of Oral Medicine and Radiology of Sydney Dental Hospital.

Device Description:
The Invisalign Mandibular Advancement appliance (MA-OB) is designed with inclined planes in the posterior region of the upper and lower aligners, and are designed to have a similar effect as a traditional Twin Block (TB) appliance. The position, size and shape of the blocks cause the mandible to protrude forward when the patient is biting down in occlusion.

The procedure for the fabrication of the appliances is through using the participants' aforementioned initial records (scans, photographs, and radiograph x-rays). From these, Invisalign will fabricate custom sequential aligners with the mandibular advancement blocks included in the design. Participants will be instructed to wear the clear functional appliance for minimum 22 hours per day, only to be removed when eating, and cleaning the aligners and their teeth (all of which is standard protocol for Orthodontic clear aligner and appliance wear). They will be instructed to change to the next aligner in the sequence every fortnight, with them attending in-person 30 minute review appointments with clinical photographs taken every six weeks for a minimum of 9 months (as is standard protocol for Class II Functional Appliance Orthodontic treatment). All appointments will take place at Sydney Dental Hospital - Orthodontics Department, and all appointments will be carried out by the Orthodontist Principal Investigator and/or a Dental Officer - Orthodontic Registrar employed by SLHD NSW Health.
Intervention code [1] 330410 0
Treatment: Devices
Description of the comparator or control
Active control group (Group 2): Historical dataset on the use of a traditional functional appliance, the twin-block, on adolescents with Class II malocclusion. This data is derived from a previous clinical trial by the University of Sydney at the Sydney Dental Hospital. (Unpublished thesis - August 2002 link ; https://ses.library.usyd.edu.au/handle/2123/4411?show=full )
Untreated control group (Group 3): Historical dataset which is matched to the experimental group in age and gender. The data will be derived from the Bolton Brush growth studies, which is a collection of longitudinal growth study lateral cephalograms during 1926 to 1959.
Lateral cephalometric tracings and analyses will be derived from age and gender matched samples to the pre-treatment and post-treatment lateral cephalograms of the Invisalign MA-OB participants.
Control group
Historical

Outcomes
Primary outcome [1] 340519 0
Dental changes of maxillary and mandibular teeth and overall changes in the occlusion. This will be assessed as a composite outcome
Timepoint [1] 340519 0
Baseline, and at the end of nine months of treatment
Primary outcome [2] 346879 0
Skeletal changes of maxillary bone proper, mandibular growth changes, intermaxillary bone changes and overall changes in the occlusion. This will be assessed as a composite outcome
Timepoint [2] 346879 0
Baseline, and at the end of nine months of treatment
Secondary outcome [1] 444325 0
User experience with the appliance using a patient questionnaire.
Timepoint [1] 444325 0
At the end of the functional treatment phase (equal to or more than 9 months)
Secondary outcome [2] 444326 0
Ease of use for clinicians
Timepoint [2] 444326 0
Duration of appliance treatment (from first appointment to end of functional phase, which is equal to or more than 9 months)

Eligibility
Key inclusion criteria
1. Angle Class II division 1 malocclusion
2. ANB angle greater than or equal to 4.5° (The ANB angle measures the relative anteroposterior position between the maxilla and mandible. In normal individuals, the ANB angle is 2° ± 2°)
3. Overjet greater than or equal to 5 mm (The overjet is the extent of horizontal (anteroposterior) overlap of the maxillary central incisors over the mandibular central incisors (normal amount of overlap is between 2 and 4mm)
4. Mild-moderate crowding (1-4 mm, 4-7 mm respectively including the curve of Spee)
5. Active pubertal growth (Cervical maturation stage up to CS 3-4.)
6. Can speak and read English to provide informed consent
Minimum age
10 Years
Maximum age
15 Years
Sex
Both males and females
Healthy volunteers
No
Key exclusion criteria
1. Syndromic individuals (including cleft lip and palate)
2. Crossbite, severe crowding, hypodontia.
3. Temporomandibular joint disorder signs and symptoms
4. Previous Orthodontic treatment
5. Unable to speak or read English to provide informed consent

Study design
Purpose of the study
Treatment
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?



Intervention assignment
Other
Other design features
The study contains 3 arms: one single prospective intervention arm, and two historical data control groups.
- Intervention group (Group 1): prospective use of the Invisalign Mandibular Advancement appliance (MA-OB) for Class II malocclusion in adolescents
- Active control group (Group 2): Historical dataset on the use of a traditional functional appliance, the twin-block, on adolescents with Class II malocclusion. This data is derived from a previous clinical trial by the University of Sydney at the Sydney Dental Hospital.
- Untreated control group (Group 3): Historical dataset which is matched to the experimental group in age and gender. The data will be derived from the Bolton Brush growth studies, which is a collection of longitudinal growth study lateral cephalograms during 1926 to 1959.
Phase
Not Applicable
Type of endpoint/s
Efficacy
Statistical methods / analysis
The sample size was calculated based on previously conducted studies. The biostatistician confirmed the study power and sample size required and advised to detect a -4mm change in overjet, 11 patients per group is required. This is based on pre-treatment overjet of 8.12mm (SD 3.1) for a type one error alpha of less than or equal to 0.05, and power 0.80.
Additionally, sample size was also calculated based on the Mandibular unit length pre-treatment SD of 4.18mm. To detect a 2mm increase, 70 samples per group would be needed. To detect a 3mm increase, 32 samples per group would be needed for 80% power.
Based on previous studies, a sample size calculation showed that a total of 69 subjects with 23 patients per group (19 per group with 20% attrition rate) were needed to detect an increase in mandibular length of 2.0 mm to achieve 80% of power with estimates changes in mandibular length (Franchi, Baccetti et al. 2000, Martina, Di Stefano et al. 2020). The intervention group will be selected based on the inclusion and exclusion criteria from Sydney Dental Hospital’s Department of Orthodontics.

Recruitment
Recruitment status
Active, not recruiting
Date of first participant enrolment
Anticipated
Actual
7/04/2026
Date of last participant enrolment
Anticipated
Actual
14/07/2026
Date of last data collection
Anticipated
30/09/2027
Actual
Sample size
Target
25
Accrual to date
Final
25
Recruitment in Australia
Recruitment state(s)
NSW
Recruitment hospital [1] 27555 0
Sydney Dental Hospital - Surry Hills
Recruitment postcode(s) [1] 43669 0
2010 - Surry Hills

Funding & Sponsors
Funding source category [1] 318290 0
Commercial sector/Industry
Name [1] 318290 0
Align Technology
Country [1] 318290 0
Australia
Primary sponsor type
University
Name
University of Sydney
Address
Country
Australia
Secondary sponsor category [1] 320675 0
None
Name [1] 320675 0
Address [1] 320675 0
Country [1] 320675 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 316931 0
Sydney Local Health District Ethics Review Committee (RPAH Zone)
Ethics committee address [1] 316931 0
Ethics committee country [1] 316931 0
Australia
Date submitted for ethics approval [1] 316931 0
23/09/2024
Approval date [1] 316931 0
13/02/2025
Ethics approval number [1] 316931 0

Summary
Brief summary
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 139462 0
Dr Narayan Gandedkar
Address 139462 0
Sydney Dental Hospital, 2 Chalmers St, Surry Hills NSW 2010
Country 139462 0
Australia
Phone 139462 0
+61 477100977
Fax 139462 0
Email 139462 0
[email protected]
Contact person for public queries
Name 139463 0
Narayan Gandedkar
Address 139463 0
Sydney Dental Hospital, 2 Chalmers St, Surry Hills NSW 2010
Country 139463 0
Australia
Phone 139463 0
+61 477100977
Fax 139463 0
Email 139463 0
[email protected]
Contact person for scientific queries
Name 139464 0
Narayan Gandedkar
Address 139464 0
Sydney Dental Hospital, 2 Chalmers St, Surry Hills NSW 2010
Country 139464 0
Australia
Phone 139464 0
+61 477100977
Fax 139464 0
Email 139464 0
[email protected]

Data sharing statement
Will the study consider sharing individual participant data?
No
No IPD sharing reason/comment: Patient data privacy



What supporting documents are/will be available?

No Supporting Document Provided


Results publications and other study-related documents

Documents added manually
No documents have been uploaded by study researchers.

Documents added automatically
No additional documents have been identified.