Marginal Gap and Screw Loosening in CAD/CAM Materials for Implant-Supported Fixed Partial Dentures: An In Vitro Study

To assess and compare the marginal gap and screw loosening, and their relationship, in three-unit implantsupported fixed partial dentures (ISFPDs).

Fifty frameworks were fabricated from zirconia (Zir), cobalt-chromium (CoCr), titanium (Ti), polyetheretherketone (PEEK), and polyetherketoneketone (PEKK) (n = 10 each) using CAD/CAM technology on a standardized two-implant model. Vertical marginal discrepancies were measured using scanning electron microscopy at four points per framework/abutment interface. Screw loosening was assessed using a digital torque device. Data were analyzed using IBM SPSS software with a significance level of P < .05.

The marginal mean gap differed significantly between the groups across all four surfaces (P < .001). Overall, PEEK had the smallest marginal mean gap (67.22 ± 15.55 μm), followed by Ti (105.65 ± 30.52 μm), PEKK (106.80 ± 34.58 μm), and Zir (115.62 ± 22.02 μm), with CoCr showing the largest gap (176.87 ± 88.34 μm). In screw loosening tests, PEKK demonstrated the lowest values in both molar (0.44% ± 0.73%) and premolar (0.06% ± 1.40%) abutments, whereas PEEK showed the highest values in molar abutments (1.03% ± 1.21%) and CoCr showed the highest values in premolar abutments (2.15% ± 1.29%). No significant correlation was observed between the marginal gap and screw loosening (P > .05).

The findings of this study emphasize the critical role of material selection in the clinical performance of ISFPDs. PEEK offers superior marginal adaptation, potentially reducing microleakage, whereas PEKK enhances screw stability, minimizing prosthetic complications.