Influence of diamondlike carbon-coated screws on the implant-abutment interface

To evaluate the implant-abutment interface area and the abutment screw loosening value when diamondlike carbon (DLC)-coated or titanium screws were used before and after cyclic loading.

Thirty-six implants were divided into four groups according to the type of connection (external hexagon [EH] or internal hexagon [IH]) and the type of abutment screw (with [EHD/IHD] or without [EHT/IHT] DLC coating). The implants were placed in epoxy resin-glass fiber composite, and crowns cast in a metal alloy were screwed to the implants. The implant-abutment interface was measured before (VG1) and after (VG2) cyclic loading. The removal torque values were recorded.

In groups with titanium screws, there was an increase in the implant-abutment interface area from VG1 to VG2, whereas in groups with DLC-coated screws, the interface area was reduced (EHT = 4.49%, IHT = 24.32%, EHD = -1.05%, IHD = -9.95%). In the IHT group only, the implant-abutment interface area showed a statistically significant difference between VG1 and VG2. The Pearson correlation indicated no significant differences among the studied factors, where r = -0.11 for EHT, 0.14 for EHD, 0.07 for IHT, and 0.43 for IHD.

The implant-abutment interface areas in groups with an EH connection were larger than those in groups with an IH connection, regardless of the type of screws used. The screw loosening values decreased in all groups after cyclic loading. No correlation between the implant-abutment interface area and the screw loosening value was seen.