Background <p>In the maxillary anterior region, differences in bone density along the drilling path can impact the accuracy of implant placement despite the use of a surgical guide. Hence, the aim of this in vitro study was to investigate the accuracy of implant placement using the over-preparation technique in different drilling environments in the maxillary anterior region.</p> Methods <p>Three experimental models (a, b, and c) were designed and fabricated to simulate the following drilling environments (<i>n</i> = 60 each): unhealed bone, less dense bone, and dense bone after tooth extraction. The models were subjected to implant cavity preparation and placement using the over-preparation technique (group OPT) and conventional surgical guide technique (group CGT). Differences between the actual positions and the planned positions of the implants were calculated.</p> Results <p>The deviations of the implants in the group OPT in Model a and Model b were significantly smaller than those in the group CGT (<i>P</i> &lt; 0.05). Among the group OPT, Model c presented with the smallest deviation, followed by Model b and Model a (<i>P</i> &lt; 0.05), and the CGT group showed the same trend.</p> Conclusions <p>In the maxillary anterior region, differences in bone density along the drilling path can adversely affect the accuracy of implant placement. These discrepancies can be significantly minimized using the over-preparation technique.</p>