The clinical effects of the use of mechanical vibration device in conjunction with orthopaedic appliance in correction of mandibular retrusion

60 subjects will be recruited for this study who will be randomly allocated, by an independent person, into 4 groups (two positive control groups and two experimental groups). The experimental groups are as follow: Group Vib-FA-Y: Patients at Cervical Vertebral Maturation of CS 3 and 4 will be treated with functional appliance with vibration device. Group Vib-FA-M: Patients at Cervical Vertebral Maturation of CS 5 will be treated with functional appliance with vibration device. All experimental subjects will be treated with a fixed functional appliance to minimise compliance issues. The functional appliance, composed of metal capping on the upper and lower first molars, is cemented onto the teeth. The lower jaw is postured forward by the telescopic arms that are attached to the metal cappings. The upper component of fixed functional appliance also included a palatal expander which is designed to widen the upper jaw. The functional appliance will be used for 9-12 months. The subjects in the experiment groups will also use the VPro5 C-shaped vibration device (Propel Orthodontics, Milpitas, USA) for 5 minutes a day. This vibration device operates at a frequency of 120 Hz and a magnitude of 50 grams. It is designed to use intra-orally by inserting the C-shape intra-oral attachment between the upper and lower teeth. Patients are instructed to bite on the attachment and the mechanical vibration will be delivered when the patients turn the devices on. The device will turn itself off after 5 minutes. No other fixed appliance, e.g. braces, will be provided during the functional appliance therapy. All clinical procedures and data analyses will be carried out by principal researcher who has at least 15 years of clinical orthodontic experience. The following outlines the face-to face appointment visits and clinical procedures of this research: Visit 1. Standard orthodontic records i.e. photographs, radiographs (cone beam computer tomography) and moulds of the upper and lower teeth will be taken. Visit 2. 4 to 8 small separating elastics will be placed between the back teeth to create spaces so to allow the metal capping be placed in the following visits. Visit 3. One week later, the metal cappings will be trialled for the right size and moulds of the upper and lower teeth will be taken. A wax bite which records the ideal lower jaw position will be taken. The metal cappings are then removed and the separating elastics will be replaced. Visit 4. Two weeks later, the metal cappings with the expander will be cemented to the teeth. The telescopic arms will be attached to the metal cappings using an allen key. This may vary with individual. The subject will be instructed on the use of the mechanical vibration device. This device needs to be used for 5 minutes a day throughout the whole treatment period. Visit 5. Six weeks later, review appointment and adjustment of the appliance may be done accordingly. At the review appointment, overjet, canine and molar relationships and patient soft tissue profile will be assessed. The patients will be instructed to perform the expansion using an expansion key once a day for 2-3 weeks depending on the amount of expansion needed. Visit 6-11. Review appointments 6 weekly. The appliance will be checked at each review appointment. At the review appointment, overjet, canine and molar relationships and patient soft tissue profile will be assessed. Visit 12+. The duration of the functional appliance therapy is 9-12 months depending on the obtainment of ideal canine and molar relationships and soft tissue profile. At the end of this phase of treatment, the function al appliance will be removed and the standard records will be taken i.e. photographs, radiographs (cone beam computer tomography) and moulds of the upper and lower teeth. The research procedures will be finished at this point.