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.
Keywords: reduced-diameter implant, immediate loading, conventional loading, loading protocol, implant-retained overdenture