Immediate or Early vs. Delayed Loading Protocols for Two-Implant Mandibular Overdentures in Edentulous Population: A...

Edentulous patients often receive mandibular overdentures retained by dental implants; however, the optimal loading protocol (immediate/early vs. delayed loading) for minimizing marginal bone loss (MBL) remains uncertain. This systematic review and meta-analysis aimed to compare MBL between immediate or early loading protocols and delayed loading protocols in two-implant mandibular overdentures.

This study was conducted in accordance with PRISMA guidelines. Randomized controlled trials (RCTs) comparing immediate and/or early loading with delayed loading in fully edentulous patients rehabilitated with two-implant mandibular overdentures were included. Non-randomized studies, studies involving partial edentulism, and those with insufficient sample sizes were excluded. A comprehensive search was performed in PubMed, Scopus, Embase, Web of Science, Cochrane Library, and ClinicalTrials.gov from January 1990 to April 2025. Risk of bias was assessed using the Cochrane RoB 2 tool. Data were synthesized using a random-effects meta-analysis, with subgroup analyses performed according to implant type, attachment system, and surface characteristics.

Twenty-two randomized controlled trials involving 580 patients (296 immediate/early loading; 284 delayed loading) and 1186 implants were included in the systematic review. Of these, 13 studies provided sufficient quantitative data for inclusion in the meta-analysis. Pooled analysis demonstrated that immediate/early loading was associated with significantly lower marginal bone loss compared with delayed loading (WMD = -0.13 mm; 95% CI: -0.23 to -0.03; p = 0.04). However, this difference was small and likely not clinically meaningful and may fall within the range of radiographic measurement variability. Subgroup analysis showed that early loading was associated with greater reduction in MBL compared with delayed loading (WMD = -0.24 mm; 95% CI: -0.44 to -0.05), whereas immediate loading alone showed no significant difference. Bone-level implants and Locator attachments were associated with more favorable outcomes, while effects of surface treatment were inconsistent. Substantial heterogeneity was observed across studies, and the certainty of evidence (GRADE) was low to moderate due to risk of bias, inconsistency, and potential publication bias.

Immediate and early loading protocols demonstrate similar clinical performance to delayed loading in terms of marginal bone preservation. Although a small statistically significant difference was observed, the effect size is unlikely to be clinically meaningful. The certainty of evidence is limited, and findings should be interpreted with caution due to heterogeneity and risk of bias across included studies.