الفهرس 
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Abstract
Aim: This study aims to evaluate the wear behavior and compare the retention between one of the most common used stud attachments “Ball” and a new one “Novaloc” for implanted supported mandibular over denture
Methodology: Two epoxy resin models represented completely edentulous patients were
duplicated from an educational cast and prepared to receive two implant analogues in the canine area. Two different attachment systems were used in this study: the first one was Ball attachment with its titanium patrix and metal housing with gold insert, the second one was Novaloc with its carbon-based coating patrix, PEEK matrix and insert. They were divided randomly into two groups:Ball group and Novaloc group. Two overdentures were fabricated for each group. The pick-up proceeded with the right female part for each attachment as the conventional methods. Robota simulator applied multiple cycles mimicking the insertion and removal of the overdentures at the baseline, 500 cycles, 1000 cycles, 1500 cycles and 2000 cycles. Digital microscope evaluated then the wear behavior of each attachment during these different cycles. Universal testing machine was used to measure the retention of each attachment at the same time intervals
Results: Comparison between mean difference of wear (wear changes) of both groups was performed by using independent t-test which revealed that group I (Novaloc) was significantly higher than group II (Ball) between baseline and 2000 cycles. Regarding retention, comparison between group I (Novaloc) & group II (Ball & socket) was performed by using independent t-test which revealed tha tretention of group I (Novaloc) was significantly lower (P<0.05) than group II (Ball & socket) at
baseline, 1000 cycles, 1500 cycles & 2000 cycles
Conclusion: The rate of wear was higher in Novaloc attachment which comprised PEEK Inserts within their components, than those of ball attachments with its gold precious alloy inserts. Regarding retention of both attachments, the Ball system had a significantly higher initial and final retention values compared to the Novaloc attachments.