An Umbrella Review of Meta-Analyses on Transcrestal Sinus Floor Elevation: Methodological Quality, Primary-Study Overlap, and Interpretive Boundaries

Background/Objectives: Transcrestal sinus floor elevation (TSFE) includes several surgical approaches that differ in access, instruments, and force delivery. Existing meta-analyses often combine these approaches. This umbrella review examined methodological quality, primary-study overlap, and the limits of clinical interpretation across three decisions: short implants versus sinus floor elevation, transcrestal versus lateral access, and technique choice within transcrestal elevation. Methods: Following the Cochrane Handbook and PRISMA 2020 reporting standards, eligible meta-analyses on TSFE published between 2015 and April 2026 were identified through a three-phase systematic search across PubMed, EMBASE, Cochrane CENTRAL, Web of Science, and Scopus. Methodological quality was assessed using AMSTAR 2 with verbatim per-item evidence; primary-study overlap was quantified using the Corrected Covered Area. Results: Thirty meta-analyses met the inclusion criteria. AMSTAR 2 confidence was MODERATE in nine reviews, LOW in 11, and CRITICALLY LOW in 10; none was rated HIGH. Pool-level Corrected Covered Area was 0.92%, while cluster-level overlap reached 10.90% in the graftless osteotome cluster. Implant survival was generally high across the reviewed comparisons. Data on membrane perforation, benign paroxysmal positional vertigo (BPPV), and patient-reported outcomes were less complete and were reported inconsistently. Within the limited technique-specific evidence, BPPV was reported mainly with osteotome-based procedures, including one case among 24 patients (4.17%) in the osteotome group reported by Cobo-Vázquez et al. Conclusions: The available meta-analytic evidence supports high implant survival across the main treatment options, but it does not support a simple ranking of techniques. Clinical interpretation should follow the decision being made: whether sinus elevation is needed, whether transcrestal or lateral access is appropriate, and which transcrestal technique fits the case. Signals for BPPV and other complications with osteotome-based procedures are suggestive, but event reporting is sparse and certainty is limited. Biomechanical explanations should therefore be treated as clinical context rather than as causal findings of this umbrella review.