Background and objectives : Beneath titanium and zirconia recently also polyetheretherketone (PEEK) has been promoted as suitable implant material especially in orthopedics. Although highly biocompatible, these PEEK-based materials do not show the same osteoconductive properties as conventional implant surfaces like e.g. titanium. Therefore, it was the aim of this pilot study in sheep to analyze the osseointegrative properties of coated and uncoated PEEK implant surfaces after 2 and 12 weeks.

Materials and methods : Three groups of materials were tested: uncoated carbon-fiber reinforced PEEK (CFR-PEEK) as reference, titanium-coated CFR-PEEK (Ti-coating), and titanium/hydroxyapatite double-coated CFR-PEEK (Ti/HA-coating). In n = 6 sheep 54 implants (length = 10 mm) were placed in the right and left part of the pelvis ( n = 3 implants per surface group per animal). After 2 and 12 weeks n = 3 implants per group were examined histologically (bone-to-implant-contact, BIC) and n = 6 implants per group were tested by a pull-out test. Additionally, a histomorphometrical and fluorescent microscopic analysis was performed.

Results : All implants could be placed without complications and with good primary stability. There was no mechanical attrition of the coating. Pull-out values at 12 weeks showed significant ( p < 0.05) increased retention for Ti-coating (max. 1351 N) and Ti/HA-coating (max. 1535 N) in comparison to reference (max. 68 N). In case of Ti/HA-coating, the implant-to-bone-bonding after 12 weeks was stronger than the mechanical resistance of the bulk material. Thus in 5 out of 6 cases the CFR-PEEK material broke. In case of Ti-coating only one implant broke. In all groups a steady increase from 2 to 12 week could be detected. Preliminary microradiographic and histologic results confirmed an improved bone-to-implant contact for coated PEEK vs uncoated PEEK.

Conclusions : In comparison to uncoated PEEK, surface coating with titanium or titanium/hydroxyapatite revealed highly favorable biomechanical and biological characteristics. Thus an application in oral reconstructive surgery could be considered.