Abstract
PURPOSE:
To
evaluate the outcome of three (fixed-on-3 = Fo3) vs four (fixed-on-4 =
Fo4) implants immediately restored with metal-resin screw-retained
cross-arch prostheses in fully edentulous jaws.
MATERIALS AND METHODS:
Forty-eight
edentulous or to be rendered edentulous patients were randomised in six
centres (eight patients per centre) to the Fo3 group (24 patients: 12
maxillae and 12 mandibles) and to the Fo4 group (24 patients: 12
maxillae and 12 mandibles) according to a parallel group design. To be
immediately loaded, implants had to be inserted with a minimum torque of
40 Ncm. Outcome measures were prosthesis and implant failures,
complications and peri-implant marginal bone level changes evaluated up
to 1 year post-loading.
RESULTS:
One maxillary prosthesis
per group was delayed loaded because implants could not be placed with a
torque of at least 40 Ncm. Ten patients in the Fo3 group and four in
the Fo4 group had implants placed flapless. One year after loading no
drop out occurred. One patient of the Fo3 group lost three implants vs
three patients of the Fo4 group who lost four implants, the difference
being no statistically significant (risk difference = -0.08; 95% CI:
-0.27 to 0.10; Fisher's exact test P = 0.609). One mandibular Fo3 and
one maxillary Fo4 prosthesis failed. Six Fo3 patients were affected by
complications vs three Fo4 patients (risk difference = 0.12; 95% CI:
-0.10 to 0.34; Fisher's exact test; P = 0.461). Both groups lost
marginal bone in a statistically significant way (0.22 ± 0.20 mm for Fo3
patients and 0.40 ± 0.21 mm for Fo4 patients), with Fo3 group showing
less marginal peri-implant bone loss than Fo4 group (estimate of the
difference = -0.18 (standard error: 0.06) mm; 95% CI: -0.30 to -0.06; P =
0.005). There were no differences in clinical outcomes between the six
operators.
CONCLUSIONS:
These preliminary results suggest
that immediately loaded cross-arch prostheses of both jaws can be
supported by only three dental implants at least up to 1 year
post-loading, though longer follow-ups are definitively needed.
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