Abstract: Purpose: Poly-ether-ether-ketone (PEEK) is a sole polymer material that has recently been introduced to dentistry; marginal gap is increased significantly after thermomechanical fatigue (TF) as well as cement dissolution and, lastly failure of restoration. The current research aimed to evaluate the marginal adaptation of two types of monolithic pressable crowns supported by different implant abutments after thermo-mechanical fatigue. Materials: Twenty – eight titanium dummy implants were implanted in epoxy resin blocks and allocated into two groups according to type of implant abutments (n=14): titanium implant abutments group (Ti) and ceramic-reinforced poly-ether-ether-ketone implant abutments group (PEEK). Each group was further subdivided into two subgroups according to type of crowns (n = 7): monolithic lithium disilicate "IPS e.max Press" crowns subgroup (EP) and monolithic ceramic reinforced poly-ether-ether-ketone (BioHPP Granulates) crowns subgroup (BG). All crowns were fabricated by means of the pressing technique. After surface treatments, adhesive cementation was performed for all crowns. The samples were subjected to thermomechanical fatigue (TF). Marginal adaptation was measured before and after thermomechanical fatigue by means of a digital stereomicroscope. Results: PEEK group recorded lower marginal gap mean values before and after thermomechanical fatigue (29.06±7.84µm) (39.70±12.00µm) respectively compared to Ti group (41.57±8.82µm) (51.02±12.53µm) respectively. (EP) recorded lower marginal gap mean values compared to (BG) before and after thermomechanical fatigue in both different implant abutments. Conclusions: For all tested materials, the marginal gap mean values documented in the current study were within the limits of clinically acceptable standards.

Ceramic-reinforced PEEK (BioHPP); IPS e.max Press; Margin adaptation; PEEK implant abutment; Titanium abutment; Thermomechanical fatigue.