Abstract
Introduction: The objective of this study in vitro was to evaluate the retentive forces of PEEK and Co-Cr alloy clasps by the insertion and removal test simulating 10 years use. Material and Methods: 16 PEEK clasps and 16 Co-Cr clasps were fabricated for 32 third molars with similar dimensions. Each clasp assembly was subjected to an insertion /removal test on its abutment molar with a Test Universal Machine (Instron® 4465, Instron Co. Ltd, Norwwod, MA) to analyze with Newton the retention force. To analyze the retention over the course of insertion/removal test, retention was measured every 1500 cycles. With a total of 15000 cycles, which represents the insertion / removal of the clasp for 10 years, estimating that the patient would do four full cycles a day. Results: Co-Cr clasps showed higher retention (mean 13,63 Nw) than PEEK clasps (mean 8,04 Nw). All clasps exhibited an increase in retentive force during the first period of cycling followed by continuous decrease. Were obtained significant differences between retention forces of each material groups (p<0.001). Conclusions: We can use PEEK clasps for removable prostheses. Retention forces of PEEK clasps were clinically acceptable, but inferior retention forces of Co-Cr clasps. They are needed in vivo studies to contrast the results.
Highlights
The objective of this study in vitro was to evaluate the retentive forces of PEEK and Co-Cr alloy clasps by the insertion and removal test simulating 10 years use
Student test for independent data will be used to evaluate the differences between the removal and insertion forces according to clasp materials after the aging process
Based on the data obtained in the present investigation, the retention forces of the PEEK clasps show values clearly inferior to those of Co-Cr alloy, clearly valid for their clinical use
Summary
The objective of this study in vitro was to evaluate the retentive forces of PEEK and Co-Cr alloy clasps by the insertion and removal test simulating 10 years use. Retention forces of PEEK clasps were clinically acceptable, but inferior retention forces of Co-Cr clasps They are needed in vivo studies to contrast the results. Different materials have been used to make clasps for removal prostheses, from cobalt-chromium, titanium and gold [9]. In order for the clasps to be retentive they must be flexible and retain the prostheses satisfactorily [12,13,15] They do not have to transmit excess stress to the abutment tooth. Previous studies have shown that clasps made of more elastic materials present better resistance to loss of retention [3,1,29]
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