To investigate changes in alveolar crestal bone levels adjacent to dental implants prior to and after functional loading, dental radiographs of 103 implants from consecutively treated patients were taken at four time-points: immediately after surgical insertion, at 3-6 months after surgery, at 12 months, and at 24 months after surgery. A computer-assisted method was used to measure the percent of bone change (%BC) relative to the shoulder-apex length of the implants at mesial and distal sites. Differences in the mean rates of %BC between the pre-loading period (3-6 months post-surgery) and the post-loading periods PLP1 and PLP2 (6-12 months and 12-24 months post-surgery, respectively) were evaluated. Rates of % BC during PRE, PLP1, and PLP2 were also determined for locations (maxilla or mandible) and types (screw or press-fit). Significantly higher rates of % bone loss per month were found for all implants during PRE compared with PLP1 and PLP2, and during PLP1 compared with PLP2. During PRE, maxillary implants had a significantly higher rate of bone loss compared with mandibular implants. During PLP1, mandibular implants showed some further loss, whereas maxillary implants exhibited a small but significant gain. No significant difference was found during PLP2. Bone loss adjacent to press-fit implants was significantly higher than that adjacent to the screw type during PRE, while no difference was found during the post-loading periods.