This study investigates the reliability of palatal rugae-based identification following maxillary expansion procedures, including Miniscrew-Assisted Rapid Palatal Expansion (MARPE) and Surgically Assisted Rapid Maxillary Expansion (SARME). Because maxillary expansion alters the morphology of the palatal vault and the spatial relationship of the palatal rugae, conventional global alignment of the anterior palate may not provide stable post-treatment identification. The study evaluates a novel three-dimensional analysis approach based on separately segmented and independently aligned palatal ruga patches, with emphasis on preserving local morphological characteristics rather than global palatal configuration. Within-subject deviations before and after treatment will be compared with between-subject deviations to determine whether individual-specific ruga morphology remains distinguishable after expansion. Machine learning-based classification models using four independently aligned ruga patches will be developed to differentiate genuine matches from impostor comparisons. The primary analysis focuses on surgical expansion groups (MARPE and SARME) to assess whether pre-expansion scans can still be matched to post-expansion scans of the same individual. Secondary analyses will compare the performance of the ruga patch model with conventional anterior palate alignment and will simulate a mixed forensic database containing both treated and untreated individuals. The findings may provide evidence for the forensic applicability of palatal rugae identification after orthopedic and surgically assisted maxillary expansion procedures.

Inclusion Criteria:

• transverse maxillary deficiency requiring 5-8 mm of expansion
• indication for either non-surgical miniscrew-assisted palatal expansion or surgically assisted miniscrew-assisted palatal expansion
• availability of complete pre- and post-treatment intraoral scans
• good general health
• permanent dentition

Exclusion Criteria:

• Previous maxillary expansion treatment
• Craniofacial syndromes or cleft lip/palate
• Severe periodontal disease
• Active oral infection
• Systemic conditions affecting bone metabolism
• Pregnancy or breastfeeding
• Inability to comply with study procedures or follow-up visits

De-identified individual participant data will be shared upon reasonable request after publication of the primary results. Requests will be reviewed by the study investigators and data will be provided in accordance with institutional and ethical regulations.

De-identified individual participant data and the study protocol will be available after publication of the primary results and will remain available for 5 years.

Access to de-identified individual participant data and supporting documents will be provided to qualified researchers upon reasonable request. Requests will be reviewed by the study investigators and data will be shared in accordance with institutional policies and ethical approvals.