Fracture Strength of Implant Screw-Retained All-Ceramic Crowns with the Use of the Angulated Screw Channel: A Pilot Study.
Int J Periodontics Restorative Dent. 2020 Mar/Apr;40(2):245-252. doi: 10.11607/prd.3952.
Abstract
To
correct for angulation discrepancies in the maxilla, implant companies
have designed angulated screw channel (ASC) abutments. The design of
these abutments allows for the restorative screw channel to be placed up
to 25 degrees off the center axis of the implant. Minimal independent
research has been published to evaluate the fatigue resistance of this
implant-abutment connection. This study evaluated the fracture strength
of a newly designed zirconia crown with a 25-degree angulated screw
channel (n = 5) vs a straight channel (n = 5). Each specimen was
subjected to an off-axis compression load from an MTS cyclic loading
machine with a custom-designed indenter simulating a natural dentition.
All the 25-degree angulated screw channel specimens failed, with four of
the five (80%) catastrophically failing. Four of the five
straight-channel specimens failed, with two of the five (40%)
catastrophically failing. Results revealed the potential abutment
fracture from internal stresses at the screw-zirconia and
metallic-zirconia interfaces. Further research is needed to test the use
of all-ceramic crowns with the use of the angulated screw channel.
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