The FL showed significantly less anatomic drift for all weights except 0.39 N*s ( P < 0.01). The average clinical displacement of the FL was 0.07 mm, and of the FF was 1.02 mm ( P < 0.0009). Linear regression analysis of anatomic drift as a function of the procedure duration revealed a positive correlation for the FF (y = 0.61x), but not for the FL (y = 0.02x). Conclusions The bone anchored FL is significantly more stable than the friction fit FF.