Marwa Essam EL Dein, Nagla M.H. Nassouhy And Hamdy Abo El Fotooh,

ABSTRACT
Aim Of The Study: To Compare The Retention Of Removable Partial Denture Clasps Made From Thermoplastic Resin Material (acetal And PEEK) And Cobalt Chromium Clasps Using The Universal Testing Machine. Methodology: An Acrylic Resin Model Of Kennedy Class III Was Fabricated To Receive Unilateral Partial Denture Frameworks With Aker Clasps. The Abutments Were Covered With Surveyed Crowns With 0.01 Inch Buccal And Lingual Undercuts. Twelve Partial Denture Frameworks Were Fabricated From Co-Cr, Acetal And PEEK , Four Frameworks Per Group. For Measuring Retention, Universal Testing Machine Was Used, The Vertical Pulling Force Was Applied At The Cross Head Of Speed 0.5 Mm/min Until Disengagement Of The Clasp Occur. The Results Will Be Recorded In Newton On A Computer Display And Printed Out.

Results: A Statistically Significant Difference Was Found Between Co-Cr, Acetal And PEEK Groups Where (p<0.001). A Statistically Significant Difference Was Found Between Co-Cr Group And Each Of Acetal And PEEK Groups Where (p<0.001) Respectively. While No Statistically Significant Difference Was Found Between Acetal And PEEK Groups Where (p=0.992).The Highest Mean Value Of Retention Was Found In Co-Cr Group Followed By PEEK Group, While The Lowest Mean Value Was Found In Acetal Group. Conclusion: Within The Limitations Of This Study, It Was Concluded That The Mean Retentive Force Required To Remove Thermoplastic Clasps (acetal And PEEK) Was Lower Than That Required For Co-Cr Clasps Of The Same Thickness And Engaging 0.01 Inch Undercut.