The goal of this clinical trial is to determine whether two types of rapid maxillary expansion (RME) appliances produce different outcomes in children. RME is a treatment utilized to expand a narrow upper jaw. This study will include children aged 8 to 10 years who need upper jaw expansion during the mixed dentition period (when they have both temporary and permanent teeth).

The main questions this study aims to answer are:

• Do 3D-printed expansion appliances produce different skeletal and dental changes compared to conventionally fabricated appliances?
• Do children feel more comfortable with one type of appliance?
• Is there a difference in pain levels or oral hygiene between the two groups?

Researchers aimed to compare a conventionally fabricated expansion appliance manufactured in a dental laboratory with a 3D-printed expansion appliance produced digitally to determine whether the method of production affects treatment outcomes and patient comfort.

Participants:

• Being treated with one of the two expansion appliances (assigned randomly)
• Follow a standard activation protocol at home with parental guidance
• Attend regular clinic visits during expansion and retention phases
• Have dental photographs, X-rays, and digital scans taken before and after treatment
• Complete an oral health-related quality of life questionnaire
• Rate their pain using a pain scale
• Have their oral hygiene measured

Treatment effectiveness, amount of expansion, and patient comfort will be evaluated between the two groups. Additionally, the impact of digital appliance production on treatment outcomes and patient satisfaction will be investigated.

This prospective, parallel-group, randomized clinical trial aims to compare the skeletal, dentoalveolar, and patient-reported effects of conventionally fabricated and three-dimensional (3D) printed rapid maxillary expansion (RME) appliances in children with transverse maxillary deficiency during the mixed dentition period.

Participants aged 8-10 years who meet the predefined inclusion criteria and require rapid maxillary expansion as part of their orthodontic treatment will be enrolled.

The results are expected to contribute evidence-based guidance for orthodontists when selecting appliance fabrication methods, balancing biological effectiveness with patient comfort and quality-of-life considerations.

Findings from this study may also support future digital workflow integration strategies in pediatric orthodontic treatment planning.

Inclusion Criteria:

• Children aged between 7 and 11 years
• In the mixed dentition period
• Fully erupted permanent first molars
• Presence of primary canines and primary second molars suitable for use as anchorage units for at least 6 months
• Angle Class I or Class II molar relationship
• Presence of posterior crossbite and/or moderate maxillary transverse deficiency or moderate crowding
• Prepubertal growth stage corresponding to Cervical Vertebral Maturation Stage 1 (CVM1) or Stage 2 (CVM2)
• Receiving orthodontic treatment at the Başkent University Department of Orthodontics
• Parents or legal guardians willing to provide written informed consent

Exclusion Criteria:

• Previous orthodontic treatment
• Periodontal disease
• Enamel hypocalcification or significant calcium deficiency
• Root resorption
• Signs or symptoms of temporomandibular joint dysfunction
• Angle Class III molar relationship
• Craniofacial syndromes
• Cleft lip and/or palate
• Known allergy to acrylic materials or metal alloys
• Inability to maintain adequate oral hygiene during treatment
• Lack of cooperation during treatment
• Repeated appliance breakage or dislodgement (three or more times)

Individual participant data (IPD) will not be shared due to institutional policies, ethical committee regulations, and patient confidentiality considerations.

Due to the visible differences between the appliances, participants and treating clinicians cannot be blinded. However, all cephalometric and digital model measurements will be performed by an independent outcome assessor who is blinded to group allocation. Radiographic and digital files will be coded prior to analysis.