A total of 30 patients are planned to be included in the study during the first half of 2025, who will apply to the clinic. In our clinical routine, approximately 30% of RME patients are treated using the MARPE method. The patients will be randomly assigned to two different groups. The first group will be referred to the Pediatric Endocrinology outpatient clinic at NEU Faculty of Medicine for vitamin D level measurements at the beginning of the treatment. The second group will proceed with treatment as usual, without vitamin D measurement. At the end of the treatment, vitamin D levels of all patients in both groups will be measured.

This randomized clinical trial aims to evaluate the potential impact of serum vitamin D levels on the outcomes of Miniscrew-Assisted Rapid Palatal Expansion (MARPE) treatment in young adults aged 15-18 years. A total of 30 patients presenting with maxillary transverse deficiency will be recruited during the first half of 2025. Patients will be randomly allocated to two groups. The intervention group will undergo vitamin D level assessment at the beginning of treatment and receive supplementation if found deficient, while the control group will proceed without initial vitamin D evaluation.

Serum 25-hydroxyvitamin D [25(OH)D] levels will be measured at T1 and T2 timepoints. Intraoral scans will be performed using an Itero device to assess changes in intercanine and intermolar widths, and the data will be analyzed using the ORTHOCAD software. Pain levels will be recorded by the patients using a Visual Analog Scale (VAS) on specified days during the expansion phase. This study intends to determine whether baseline vitamin D status and subsequent supplementation can improve the biological response and clinical efficiency of MARPE treatment.

Inclusion Criteria:

• Patients diagnosed with Class I malocclusion
• Presence of maxillary transverse deficiency
• Adolescents aged between 15 and 18 years
• No systemic diseases, cleft lip/palate, or speech disorders
• No history of prior orthodontic treatment
• Willingness to undergo serum vitamin D testing
• Voluntary participation in the study with signed informed consent
• Good oral hygiene status

Exclusion Criteria:

• Patients with systemic diseases
• Patients who smoke
• Patients with poor oral hygiene
• Patients with cooperation or compliance issues
• Patients with intellectual disabilities
• Patients with unmonitored or insufficient pre-treatment vitamin D levels, including:
• Those who had insufficient vitamin D levels before treatment, were started on supplementation by the endocrinology department, but still had insufficient levels at the T2 measurement
• Those who were not tested before treatment but were found to have sufficient vitamin D levels only at T2

Data will be shared in a de-identified format with other researchers, upon request, for further scientific investigation. The data sharing process will adhere to ethical guidelines and privacy laws to ensure participant confidentiality and security. All shared data will be anonymized, and no personally identifiable information will be included.

Individual participant data (IPD) and supporting information will be available for sharing starting from February 20, 2025, and will remain accessible until November 25, 2025. During this time, researchers can request access to de-identified data for further scientific investigations.