PROBLEM TO BE SOLVED: To provide a high-quality drilling system of a dental implant, when performing an implant operation, capable of cutting only the cortical bone and accurately forming an appropriate implant cavity by a single drilling by low-speed rotation without irrigation.SOLUTION: The drilling system comprises a countersink drill A including a contra-angle shaft 1, a trunk part 3, and a cortical bone cutting blade 5, and a guide part 7. The rod-like contra-angle shaft 1 includes a connecting part 1a at the upper end i, and the trunk part 3 at the lower side j. The cortical bone cutting blade 5 with cutting parts 6 capable of cutting the hard cortical bone C is formed on the lower end k of the trunk part 3 at prescribed height H. The guide body 7 is formed at the lower part m of the cortical bone cutting blade 5. The cortical bone C located at the prescribed depth H from the bone apex F can be cut by the rotation of the cortical bone cutting blade 5.
