Bone neoformation at the distraction site following surgically assisted rapid maxillary expansion: a systematic...

Surgically assisted rapid maxillary expansion induces bone neoformation at the distraction site during the treatment of maxillary transverse deficiency. The aim of this systematic review was to investigate and summarize the effect of surgically assisted rapid maxillary expansion on bone neoformation at the midpalatal distraction site, with emphasis on bone maturation and morphology. A systematic search was performed across PubMed, SCOPUS, Web of Science, and the Cochrane Central Register of Controlled Trials up to June 2026. Selection criteria included randomized controlled trials, prospective and retrospective cohort studies, and case-control studies evaluating bone neoformation following surgically assisted rapid maxillary expansion using tooth- or bone-borne expanders. Eight studies, comprising one randomized controlled trial and seven cohorts involving 147 patients aged 15-59 years, were included. Bone density was evaluated via optical density or Hounsfield units across four regions along the midpalatal suture over follow-up periods of three to ten months. Results indicated that bone density reached its minimum at the start of the retention period, followed by a gradual increase; however, density generally failed to return to baseline values by the final follow-up. Risk of bias was rated as 'Good' for two studies and 'Fair' for six. In conclusion, bone density decreases across all maxillary regions following SARME and typically does not recover to baseline levels within ten months. Due to significant risk of bias and a lack of randomized trials, evidence remains insufficient to establish definitive clinical thresholds for skeletal stability or the initiation of tooth movement.