Clinical Outcomes, Success/Failure Patterns, and Complications of Microscrew-Assisted Rapid Palatal Expansion in Post-Pubertal Transverse Maxillary Deficiency: A Scoping Review

Background/Objectives: A non-surgical orthodontic treatment strategy for transverse maxillary deficiencies, especially in late adolescents and young adults, is microscrew-assisted rapid palatal expansion (MARPE). The literature indicates several concerns regarding its long-term efficacy and potential complications. Recent studies have provided valuable insights into the MARPE technique, particularly focusing on its efficacy, potential complications, and treatment failures. The present scoping review aims to synthesize and critically appraise clinical evidence on MARPE in post-pubertal patients, with a specific focus on treatment outcomes, mechanisms of failure, and local and systemic adverse effects to inform risk–benefit assessment and clinical decision-making. Methods: A systematic search was conducted across four electronic databases (PubMed, EMBASE, Scopus, and Cochrane Library) to identify English-language clinical trials, observational studies, and systematic reviews published between January 2015 and December 2025. The search strategy employed controlled vocabulary (MeSH terms) and Boolean operators targeting MARPE, treatment failure, and adverse effects in patients aged ≥ 16 years. After title/abstract screening and full-text assessment using predetermined inclusion criteria, 15 studies (3 systematic reviews with meta-analysis, 2 umbrella reviews, 4 systematic/scoping reviews, 2 randomized controlled trials, and 4 observational studies) were selected for qualitative synthesis. Results: Fifteen studies were finally included, which demonstrated significant heterogeneity in methodological design, sample characteristics, outcome measurement protocols, and MARPE device specifications. Mean success rates of 92.5% for maxillary transverse expansion were reported, with mean expansion duration ranging between 20 and 126 days. Key adverse effects comprised dentoalveolar tipping (buccal inclination of maxillary molars and premolars), periodontal complications (buccal bone resorption of 0.6–0.9 mm, gingival recession, papilla recession in 18% of cases), root resorption, miniscrew loosening, midpalatine/circummaxillary sutures, and potential but minimally documented intracranial effects. Conclusions: MARPE appears to be a valid non-surgical option for selected post-pubertal patients, but its success depends on careful case selection and monitoring for dentoalveolar, periodontal, sutural, and rare intracranial adverse effects.