Retention Comparison of Milled Cobalt Chromium and Polyetheretherketone Secondary Telescopic Crowns in Implant-Retained Mandibular Overdentures: A Randomized Clinical Trial

This study aimed to compare the retention of cobalt-chromium and polyetheretherketone secondary telescopic crowns in implant-retained mandibular overdentures. Twelve patients were selected for the study, each received 2 implants in the canine region bilaterally to retain a mandibular overdenture with milled telescopic crowns. The primary crowns with 2° occlusal taper were fabricated using milled titanium abutments. Later, the patients were randomly divided into 2 groups: the cobalt-chromium group, where the secondary crowns were fabricated from milled cobalt-chromium alloy, and the polyetheretherketone group, where secondary crowns were constructed from milled polyetheretherketone. Retention was evaluated at the relative geometric center at baseline (zero months), 6, 9, and 12 months postprosthetic loading using a force meter gauge. The mean of 5 retention force readings was recorded in Newtons for each patient at follow-up visits, and the data were subject to statistical analysis. At baseline, after 6, 9, and 12 months, the CoCr group showed statistically significantly lower mean retention value than the PEEK group. A statistically significant decrease in retention forces within both groups was observed after 12 months postprosthetic loading. The present study suggested that milled cobalt-chromium and polyetheretherketone secondary telescopic crowns in combination with titanium primary conical crowns may provide an acceptable treatment option for completely edentulous patients regarding retentive force. The milled polyetheretherketone secondary telescopic crowns may offer higher retentive force compared to milled cobalt-chromium ones in clinical performance. To prefer one of these materials over the other needs more extensive research.