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

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.