A randomized controlled pilot trial comparing peri-implant tissue health beneath CAD/CAM-milled PEEK versus cobalt-chromium telescopic crowns for mandibular overdentures

Abstract

PURPOSE: This pilot randomized clinical trial compared peri-implant tissue health around milled cobalt-chromium (CoCr) versus polyether ether ketone (PEEK) secondary telescopic crowns in implant-retained mandibular overdentures over 12 months. METHODS: Twelve completely edentulous patients received two implants each. After randomization, secondary crowns were fabricated from milled CoCr (n = 6 patients) or PEEK (n = 6 patients). Assessor-blinded outcome assessments such as marginal bone loss (MBL), probing depth (PD), and plaque index (PI) were performed at baseline, 6, 9, and 12 months post-loading. Statistical analysis used the patient as the unit of analysis. RESULTS: No statistically significant inter-group differences were found at any time point. At 12 months, mean MBL was 0.48 ± 0.15 mm for CoCr and 0.45 ± 0.16 mm for PEEK (p = 0.735). PD increased over time within groups but remained comparable between groups (CoCr: 2.58 ± 0.58 mm, PEEK: 2.33 ± 0.41 mm at 12 months; p = 0.411). PI scores also showed no significant inter-group differences (p > 0.05). CONCLUSIONS: Over 12 months, milled PEEK and CoCr secondary telescopic crowns demonstrated comparable peri-implant tissue health. PEEK presents a viable metal-free alternative for this application. These preliminary findings warrant confirmation in larger, long-term studies.