EFFECT OF MODIFIED COPING DESIGN ON FRACTURE RESISTANCE OF ZIRCONIA CROWN

Aim of the study: To determine the effect of modified coping designs on the fracture resistance of zirconia crowns.
Materials and methods:Extracted human maxillary first premolar teeth were prepared to receive all-ceramic zirconia crown. Teeth were divided into two main groups according to the coping design. Group (Ι) (n=7) with Conventional zirconia coping extends to the finish line of the preparation. Group (ΙΙ) (n=7) with cut-back zirconia coping 2 mm short from the finish line buccally. All specimens were veneered by the traditional hand-layering technique. Crowns were cemented by self-adhesive resin cement. Then, subjected to artificial aging; thermal cycling and cyclic loading before they were loaded in a universal testing machine for fracture resistance. Data were analyzed with Student's t-test.
  Results:There was no significant difference in the mean fracture load values between conventional (477.71 ±28.13 N) and cut-back coping designs (473.29 ±35.22 N).
Conclusion:Modifications in coping design didn't improve the fracture resistance of zirconia crowns.