Aims: Immediate loading has become a predictable option for treatment, while one of the main requirements for its implementation is obtaining appropriate primary stability in implants. With that aim, conical implants are commercially available, since, according to specialized literature, they provide greater stability. One of the methods to measure implant stability which has evolved to further stages is resonance frequency analysis (RFA). In the present paper we attempt to evaluate the influence of the cortical bone on the primary stability of two implants of similar diameter and length. Study design: 15 fresh cow ribs were selected and six different implant beds were prepared in each. These preparations corresponded to two different implant systems: A Swiss Plus from Zimmer Dental® and an Mk IV from Nobel Biocare®. Two drilling protocols were used for soft bone, hard bone and bone without cortical. After preparing the beds, the implants were placed and implant primary stability was measured with the Osstell® mentor. Results: Higher ISQ (Implant Stability Quotient) values were observed for both implant systems when the cortical bone is maintained than when it is eliminated, the difference being statistically significant in the case of Mk IV implants. Conclusions: The results from this study show the importance of preserving cortical bone during drilling in order to obtain greater primary stability.