Table 3 Scoring system for resistance-to-removal (RTR) and attached bone remnants (ABR)

1

Loose screw can be removed with forceps only

No bone detectable on implant

2

Little resistance (only tip of 2 fingers needed to hold screwdriver)

Traces of bone remnants on implant

3

Moderate resistance (screwdriver held in pinch grip)

Thin bone layer on implant (10–25 % of surface coated with bone)

4

Strong resistance (like 3 but more power needed)

Moderate bone layer on implant (25–50 % of surface coated with bone)

5

Bone fracture with screw partly covered by bone

Thick bone layer on implant (>50 % of surface coated with bone)