The purpose of this study was to evaluate the effects of implant shape and bone preparation on the primary stability of the implants using resonance frequency analysis.

Sixty bovine rib blocks were used for soft and hard bone models. Each rib block received two types of dental implant fixtures; a straight-screw type and tapered-screw type. Final drilling was done at three different depths for each implant type; 1 mm under-preparation, standard preparation, and 1 mm over-preparation. Immediately after fixture insertion, the implant stability quotient (ISQ) was measured for each implant.

Regardless of the bone type, the ISQ values of the straight-screw type and tapered-screw type implants were not significantly different ( P > 0.05). Depth of bone preparation had no significant effect on the ISQ value of straight-screw type implants ( P > 0.05). For the tapered-screw type implants, under-preparation significantly increased the ISQ value ( P < 0.05), whereas overpreparation significantly decreased the ISQ value ( P < 0.05).

Within the limitations of this study, it is concluded that bone density seemed to have a prevailing effect over implant shape on primary stability. The primary stability of the tapered-screw type implants might be enhanced by delicate surgical techniques.