Abstract
PURPOSE:
To
compare the clinical outcome (in particular of marginal peri-implant
bone level changes) between immediately loaded straight implants which
had definitive abutments placed at implant placement and never removed
versus implants which had no intermediate abutments.
MATERIALS AND METHODS:
Thirty-two
edentulous patients had one of their jaws rehabilitated with a
provisional screw-retained resin reinforced cross-arch fixed prosthesis
supported by four immediately loaded implants: two central straight
implants and two either tilted or straight distal implants. The two
central straight implants were randomly allocated in two equal groups to
receive or not an intermediate abutment (Multi-Unit Abutment, MUA)
according to a parallel group design. To be immediately loaded implants
had to be inserted with a minimum torque of 30 Ncm, which was achieved
by all implants. After 4 months, definitive screw-retained metal-ceramic
prostheses were delivered and patients were followed-up to 5 years
after loading. Prostheses were removed every 8 months to facilitate
professionally delivered maintenance. Outcome measures were prosthesis
and implant failures, complications, peri-implant marginal bone level
changes and bleeding on probing (BoP).
RESULTS:
Five-years
after loading one patient dropped out from each group. No implant or
prosthetic failure occurred. Three patients of the abutment group versus
one of the no-abutment group were affected by complications (risk
difference = 0.125; 95% CI: -0.13 to 0.37; Fisher exact test, P =
0.600). At 5 years, both groups lost marginal bone in a statistically
significant way (0.32 ± 0.40 mm for patients of the abutment group and
0.35 ± 0.29 mm for patients of the no-abutment group), with no
difference in bone loss between groups at patient levels (difference =
0.03 mm; 95% CI: -0.23 to 0.29 mm; P = 0.809). At 5 years, BoP was
significantly higher in the no-abutment group than in the abutment group
(difference between medians = 25%; 95% CI: 12.5% to 25%; P < 0.001).
By considering only the average of the two central study implants per
patient with and without intermediate abutments, there were no
differences in bone loss (difference: -0.05 mm; 95% CI: -0.41 to 0.31
mm; P = 0.763), while marginal bleeding was significantly higher in the
no-abutment group (difference between medians = 25%; 95% CI: 0% to 50%; P
= 0.004).
CONCLUSIONS:
The present results suggest that
intermediate abutments may not be needed at immediately loaded
cross-arch screw-retained prostheses, unless there is the necessity to
correct implant angulation.
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