Immediate Versus Non-immediate Loading Protocols for Reduced-diameter Implants Supporting Overdentures: A Systematic Review and Meta-analysis

OBJECTIVE:This systematic review aimed to compare the influence of immediate and non-immediate loading protocols on overdentures retained by reduced-diameter implants(≦3.5mm). METHODS:Electronic databases, including MEDLINE (via PubMed), Embase and the Cochrane Central Register of Controlled Trials were searched for randomized controlled trials (RCTs) comparing clinical outcomes of immediately and nonimmediately loaded reduced-diameter implants supported overdentures. The risk of bias within and across the studies and the certainty of evidence were assessed by RoB 2.0 and GRADE, respectively. Sensitivity analysis was performed by eliminating studies at high risk of bias, and repeating the data synthesis employing the randomeffect model. Subgroup analyses were conducted based on the implant diameter and the length of follow-up. RESULTS:Six RCTs with 255 patients were included in this systematic review. The meta-analyses found similar implant survival rates between immediate and nonimmediate loaded implants in mini implant (RR=0.98; 95% CI=0.95, 1.01; p=0.12) and narrow implant subgroups (RR=0.99, 95% CI=0.94, 1.03, p =0.56), as well as in short-term (RR=0.98, 95% CI=0.97, 1.00, p =0.11) and long-term (RR=0.97, 95% CI=0.93, 1.01, p =0.09) follow-up subgroups. Additionally, marginal bone loss (MBL) showed no statistically significant difference between the loading protocols in the subgroup of long-term follow-up (MD=0.03; 95%CI=-0.16, 0.23; p=0.74). Three RCTs investigating peri-implant parameters found relatively higher modified plaque index and probing depth in reduced-diameter implant under immediate loading. CONCLUSION:Compared with non-immediate loading, the immediately loading protocol can achieve comparable survival rates and MBL in reduced-diameter implant retained overdentures.