The goal of this clinical trial is to compare the effectiveness of a protraction facemask and upper partial fixed appliance in correcting anterior crossbite in growing children with class III malocclusion. It will also learn about the patients perceptions of these treatments. The main questions it aims to answer are:

i. What is the rate of success in achieving anterior crossbite correction with the protraction facemask and upper partial fixed appliance? ii. Are there any significant differences in the dental, skeletal and soft tissue outcomes between the two treatment groups? iii. What are the patient's perceptions associated with each treatment modality received.

iv. What is the incidence of adverse effects or complications and breakages associated with each treatment modality?

Participants will be randomly assigned to one of two groups: 1) protraction facemask; or 2) upper partial fixed appliance. After investigators decide which group participants will be in, investigators will take some standard records for the study before starting the treatment. These records include:

1. Making moulds of their teeth to create study models
2. Taking a side-view X-ray of their head (called a lateral cephalometric radiograph)

Additionally, the participant will need to fill out a quick 5-minute survey called the Child Perceptions Questionnaire 8-10 (CPQ8-10). It has 25 short questions. The participant will do this survey at four different times: 1) before starting the treatment; 2) 3 months into the treatment; 3) 6 months into the treatment; and 4) after the treatment is done.

Investigators will set up appointments for the treatment based on the type assigned. Once the treatment starts, investigators will see the participant every six weeks until it is finished.

If the participant gets a protraction facemask, investigators will put a fixed expander appliance in the mouth at the palate. Investigators will teach them how to activate the appliance once a day for seven days. Afterwards, the participant will use the protraction facemask with elastics connecting the appliance in the mouth and the protraction facemask. The participant must wear it for 14 hours a day, at night.

If the participants gets an upper fixed partial appliance, investigators will bond upper fixed appliances in the mouth.

Investigators will teach the child how to clean the appliance and their mouth to avoid any potential problems or side effects during the treatment.

1. Orthodontic assessment, consent and records taking All eligible patients identified at the Faculty of Dentistry, Universiti Malaya, will be scheduled for an orthodontic assessment during the research sessions. An explanation regarding the research objectives, interventions, randomization for treatment and details on protocols of each interventions will be given to the patient as written in the patient's information sheet. Patient will be reminded that they have to receive whatever treatment allocated to them with an open heart once they consented. Once patient agreed, further assessment will be done. If patient or parents not agree, their name will be put under waiting list for orthodontic treatment in this faculty. Following the extraoral and intraoral assessment, patient's parents or carer will have to sign a consent form. Then, study model impressions will be made using alginate Kromopan Type I Lascod, and bite registration will be done using modeling wax. Intraoral and extraoral photographs will be captured using a Canon EOS RP DSLR camera. Subsequently, appointments for dental panoramic tomography and lateral cephalometric radiography will be arranged at the X-ray Department, Faculty of Dentistry, Universiti Malaya.

2. Lateral cephalometric analysis In this study, Webceph Software Version 1.5.0 will be used for digital cephalometric analysis to assess skeletal and soft tissue of the patient. Soft copies of lateral cephalometric radiographs will be coded or named randomly by an individual assistant then uploaded to Webceph, and landmarks for skeletal and soft tissue analysis will be verified before conducting the analysis. All patients with ANB value equal to and less than 0 will be included in this study.

3. Interventions allocation All eligible patients will be randomized to determine their intervention as explained in 3.5.1. Further planning for their next appointment will be done as listed below

   1. Intervention 1 - Protraction facemask Overjet, overbite, canine and molar relationship will be measured from the study model and recorded in a data collection form. Then, appointment will be given for impression taking to construct the Rapid Maxillary Expansion (RME).
   2. Intervention 2 - Upper partial fixed appliance Overjet, overbite, canine and molar relationship will be measured from the study model and recorded in a data collection form. Then, an appointment for separators insertion will be arranged a week before appointment for the band and bond up procedures.

4. Treatment phase Before undergoing either intervention, all patients will need to complete the CPQ8-10. The instructions, as outlined on the front page of the questionnaire (see Appendix D and E), will be explained to the patients. They will be encouraged to reach out to the researcher (NFS) for clarification if any of the questions are unclear. This step will be repeated and patient has to fill in the same questionnaire every 3 months after treatment started.

   • T0 - before start treatment
   • 3 months after started treatment
   • 6 months after started treatment
   • 9 months after started treatment

5. Intervention 1 - PFM (protraction facemask) Patients assigned to intervention 1 will utilize the Petit protraction facemask from Dentamedik Sdn Bhd, in conjunction with a rapid maxillary expansion (RME). This facemask consists of a forehead pad and chin pad linked by a sturdy steel support rod. The RME will be affixed in the patient's mouth one week before activating the facemask, allowing the patient to adapt to the appliance. The design and components of the RME will adhere to standardized specifications An extraoral elastic band (Ormco Zoo Pack Elastics will be attached from the hook of the rapid maxillary expansion (RME) to the facemask rod, applying a forward force to the maxilla and ensuring the elastic crosses to prevent interference with the lips. The force vector is intended to pass through the maxilla center of resistance, and the point of force application should be distal to the lateral incisors, positioned in the canine-premolar area (Petit, 1983). The force position and direction should be inclined at an angle ranging from 20° to 30° to the occlusal plane (Petit, 1983). Patients will receive guidance to wear the Petit protraction facemask and elastics for 14-16 hours daily or as close to 24 hours as feasible (McNamara, 1987). The elastic force will be incrementally increased following the staggered approach proposed by Mandall in 2010.

6. Intervention 2 - UPFA

Upper partial fixed appliance / 2 by 4 appliance (refer figure 3.7) will be used in this study by using bracket set (119-142 Unitek™ Gemini Bracket MBT™ U/L 5x5 0T-Cuspid 3Hk) with molar bands (3M™ Victory Series™ First Molar Bands) or buccal tubes (3M™ Victory Series™ Superior Fit Buccal Tubes) and upper nickel titanium archwires (3M™ Unitek™ Nitinol Heat-activated Archwire) and upper stainless steel archwires (3M™ Unitek™ Permachrome Standard Archwire) . The archwire sequence are listed below:

1. 016 nickel titanium archwire

   • To start with 014 nickel titanium as first archwire in a severely rotated cases

2. 018 stainless steel archwire A metal/plastic tubing will be used to protect the soft nickel titanium archwire and a niti push coil will be used on stainless steel archwire to jump the bite. A bite riser will be cemented (self-cured Glass Ionomer Orthodontic cement, GC Fuji Ortho) on lower posterior teeth to disengage the occlusion to allow anterior crossbite correction.

7. Follow up review Patients will be reviewed every six weeks until anterior crossbite is corrected. Post-treatment records will be taken, and the appliance will be debonded. No retainers will be given as positive overjet with incisal overlap is considered stable.

Inclusion Criteria:

1. Age group between 7 to 10 years
2. Three or four incisors in crossbite
3. Positive overbite
4. Class III skeletal with ANB equal to or less than 0 or retrusive maxilla
5. Amount of crowding equal to or less than 4 mm
6. Good oral hygiene

Exclusion Criteria:

1. Cleft lip and palate and/or craniofacial syndrome
2. Patients with syndromes or medical condition
3. Subjects involved in any other orthodontic trials
4. A maxilla-mandibular planes angle greater than 35 degree
5. Previous history of TMJ signs or symptoms
6. Lack of consent

1. Protection of Patient Privacy: Ensuring the confidentiality of participants is a fundamental ethical obligation. Sharing identifiable information may risk the exposure of sensitive personal health data, which could lead to privacy breaches.
2. Informed Consent Considerations: Participants in our study have provided informed consent with assurances that their personal and medical information will remain confidential and will not be shared beyond the scope of the study. Sharing identifiable patient data without explicit consent would violate this agreement.
3. Minimizing Risks: Disclosing patient identification increases the potential risk of re-identification, even if other data elements are anonymized. To minimize any risk of harm to participants, we have opted not to share patient-specific identifiers.