الفهرس 
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Abstract
Summary
Replacing the missing teeth with implant-supported fixed dental
prostheses became the standard of care in dental medicine in the past few
decades. Failure of posterior implant-retained fixed partial denture is
commonly associated with high occlusal overload.
The aim of this in vitro study was to evaluate the stress distribution
in implant supported screw-retained fixed partial posterior bridge,
constructed from CAD/CAM Polyetheretherketone and Zirconia. A resin
working model was constructed and two implants were placed parallel to
each other using a surgical guide at the position of the mandibular second
premolar and second molar. Ten 3 units implant supported screw-retained
fixed partial posterior bridges were manufactured by the CAD/CAM
technique; PEEK (group A) and zirconia (group B), 5 in each group. The
CAD/CAM bridges were cemented to their abutments using the DTK
adhesive, then screwed to the implants. Eight strain gauge sensors were
attached at the cervical region around each implant at four sides (mesially,
distally, buccally, lingually). The microstrains of each strain gauge were
measured and analyzed separately for each implant supported screwretained fixed partial bridge. The strain measurement were recorded in
microstrain (με) unit from the multi-channel strain-meter during load
application by a universal testing machine. Each bridge was subjected to
300 N of force that was applied at the mid pontic region where the
employed cross-head speed was 1 mm/min.
The results of the microstrains showed a statistically significant
difference between both groups at each location of measurement. group
A (PEEK) showed the highest levels of mean microstrains at all locations
of the strain gauge sensors (mesially, distally, buccally, linugally around
each implant) than group B (Zirconia).
Summary
66
The mean microstrains (με) produced mesially to the second
premolar by the PEEK fixed partial dentures (4274.4 ± 70.63) was higher
than that produced by the zirconia (1340.2 ± 34.40) with statistical
significant difference (p <0.001). The mean microstrains (με) produced
distally to the second premolar by the PEEK (8187.4 ± 89.88) was higher
than that produced by the zirconia (1797.6 ± 65.19) with statistical
significant difference (p <0.001). The mean microstrains (με) produced
buccally to the second premolar by the PEEK (1696.0 ± 58.34) was higher
than that produced by the zirconia (771.2 ± 12.64) with statistical
significant difference (p <0.001). The mean microstrains (με) produced
lingually to the second premolar by the PEEK (3768.6 ± 51.63) was higher
than that produced by the zirconia (1032.4 ± 19.86) with statistical
significant difference (p <0.001).
The mean microstrains (με) produced mesially to the second molar
by the PEEK (7917.6 ± 112.0) was higher than that produced by the
zirconia (2715.6 ± 84.33) with statistical significant difference (p <0.001).
The mean microstrains (με) produced distally to the second molar by the
PEEK (3710.4 ± 40.60) was higher than that produced by the zirconia
(1989.0 ± 50.19) with statistical significant difference (p <0.001). The
mean microstrains (με) produced buccally to the second molar by the
PEEK (2315.0 ± 47.13) was higher than that produced by the zirconia
(744.0 ± 32.12) with statistical significant difference (p <0.001). The mean
microstrains (με) produced lingually to the second molar by the PEEK
(1271.0 ± 14.85) was higher than that produced by the zirconia (430.0 ±
12.23) with statistical significant difference (p <0.001).
According to the results of the current study, the hypothesis was
rejected due to the overload bending moments generated by loading
resilient superstructure materials.