Effectiveness of deciduous molar anchorage for rapid maxillary expansion: a systematic review and meta-analysis

Objectives: To evaluate dentoskeletal effectiveness of deciduous molar anchorage in rapid maxillary expansion (RME) during mixed dentition. Materials and methods: A comprehensive search was conducted across PubMed, MEDLINE, Scopus, and Cochrane Library databases from January 2000 to March 2025, adhering to PRISMA guidelines. Included studies comprised randomized controlled trials (RCTs) and non-RCTs assessing RME anchored to deciduous molars in patients with mixed dentition. Risk of bias (ROB) was assessed using ROB2 for RCTs and ROBINS-I for non-RCTs. Data were synthesized using a random-effects meta-analysis, focusing on dental and skeletal expansion. Results: Seventeen studies (six RCTs, 11 retrospective) met the inclusion criteria. A meta-analysis of 12 studies demonstrated significant transverse changes in all evaluated areas: deciduous canines (4.27 mm), deciduous molars (5.51 mm), permanent molars (3.93 mm), and skeletal expansion (2.59 mm). Notably, dental expansion significantly exceeded skeletal expansion. Subgroup analyses comparing Haas and Hyrax expanders revealed no statistically significant differences in dentoskeletal expansion outcomes. However, heterogeneity across studies ranged from moderate to high. ROB assessments indicated moderate risk in all RCTs, whereas non-RCTs ranged from low to serious risk. Funnel plot inspection revealed no substantial asymmetry, suggesting a low likelihood of publication bias. Conclusions: This meta-analysis confirms that deciduous molar anchorage in RME significantly increases dentoskeletal transverse dimensions. No significant differences emerged between appliance designs (Haas vs Hyrax). Despite consistent expansion effectiveness, variability in study design and ROB must be considered when interpreting these results.