Abstract
Purpose: To evaluate the change in the retention of novel metallic and non-metallic combinations for
double-crown-retained mandibular overdentures on implants.
Methods: Cylindrical bases were used to insert four implants arranged in an arch, with 10 mm inter-
implant spacing anteriorly, and 35 mm posteriorly. Five groups ( n = 8 each) of different materials combi-
nations were tested for retention: zirconia abutments/PEEK framework (ZP), PEEK abutments/PEEK frame-
work (PP), titanium abutments/PEEK framework (TP), titanium abutments/CoCr framework (TC), and ti-
tanium abutments/gold copings/cobalt-chromium framework as the control group (TG). The abutment
retention height was 4 mm with 1 ° convergence angle. The retention was measured in a wet condition
using a chewing simulator initially, and then at 10 0, 20 0, 50 0, 1,0 0 0, 2,0 0 0, 3,0 0 0, 5,0 0 0, 8,0 0 0, and
10,0 0 0 insertion/separation cycles, which simulates the removing and inserting of an overdenture three
times daily for 10 years of function.
Results: The initial median retention of all groups ranged from 10.0 to 33.3 N. After 10,0 0 0 inser-
tion/separation cycles, the median retention ranged from 10.3 to 35.0 N. The change in the retention
after 10,0 0 0 cycles was not statistically significant within groups ZP and TG. For groups PP and TP, there
was a slight increase in retention with partial significance. The retention of group TC showed fluctuation
with a partially significant decrease in retention.
Conclusions: The use of novel metallic and non-metallic combinations in the construction of double-
crown-retained mandibular overdentures on implants resulted in acceptable levels of retention and might
be recommended for clinical application.
