Evaluation of Retention of Two Implants Retained Mandibular Complete Overdenture with Telescopic Attachments of Different Biocompatible Materials

Aim: The objective of this investigation was to assess and compare the retentionof two implants that maintained complete mandibular overdentures with telescopicattachments made entirely of zirconia (ZrO2), entirely of polyether-ether-ketone(PEEK), and ZrO2-PEEK ,Subjects and methods: Three acrylic edentulous mandibularoverdenture models were separated into three main groups based on their telescopingattachment systems: group ZZ was made up entirely of ZrO2; PP group was madeentirely of PEEK; and ZP group was made up entirely of ZrO2 (primary crown)-PEEK(secondary crown). The acrylic models were scanned with a laboratory scanner to gaina three‐dimensional (3D) virtual image and the primary crowns were CAD designedto ensure a similar insertion route and then milled from ZrO2 and PEEK blanks. Eachprimary crown was then scanned separately and the secondary crown was created withmechanical projections and then milled. After that, mandibular acrylic overdenture witha metal framework and the metallic lingual bar were fabricated. For measuring theretention forces of each telescopic crown type, a universal testing machine (UTM) wasutilized to employ 400, 600, 1200, 1500, and 1800 cycles of removal and insertion tothe metal bar during the retention test. Results: The outcomes revealed that the ZZgroup possessed significantly greater mean retentive forces followed by PP and thenthe ZP group. However, the retentive forces decreased respectively with an increasein the number of cycles. Conclusion: Despite the loss of retention over time, PEEKremains suitable for use as a secondary telescopic crown in substitution of zirconia orPEEK main crowns