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This simulation study was conducted to evaluate the stresses
induced by Thermoflex framework in comparison to chrome cobalt
framework on the supporting structures of Kennedy class I removable
partial denture retained with extra-coronal, semi-precision attachments.
Acrylic mandibular model with the first and second premolars
bilaterally as abutment teeth was used for this study. This model
replicates the anatomic features of the teeth and their investing
The abutments were reduced to 1.5-2 mm off occlusal to provide
sufficient tooth reduction with 6 degree taper. The metal crowns with
the male part of the extra coronal attachment were fabricated according
to conventional casting techniques. Then the chrome-cobalt class I
RPD with the female part of the extra-coronal attachment was
constructed similarly. Thermoflex RPD was constructed with the same
design as chrome cobalt framework according to manufacturer
Two four channel strain meters were used to asses and record the
strains induced at the second premolars bilaterally. Strain gauges were
installed in a groove created distal to the sockets of the 2nd premolars.
A loading device was used to produce a standardized static load within
the physiologic limits of 100 N on the first molar area unilaterally.
Micro strains were recorded at each site of the strain gauges
during posterior unilateral loading with enough time between each load
to permit complete rebound of the resilient structures.
Inspection of the recorded micro strains of the result of this study
revealed that, stresses induced distal to the abutments (2nd premolars)
during unilateral loading when using thermoflex framework, with
extra-coronal attachments were significantly higher than when using
the metal framework retained with attachments.