BACKGROUND: The existing augmented reality (AR) dental implant surgery navigation system usually uses markers to complete image guidance. However, markers often affect dentists' operations and make patients uncomfortable. METHODS: To solve the problems caused by markers, this paper proposes an effective marker-less image guidance method. After initialisation is completed by contour matching, the corresponding relationship is obtained by matching the feature points between the current frame and the preloaded initial frame. The camera pose is estimated by solving the Perspective-n-Point problem. RESULTS: The registration error of AR images is 0.731 ± 0.144 mm. The planting errors are 1.174 ± 0.241 mm at the neck, 1.433 ± 0.389 mm at the apex and 5.566 ± 2.102° for the angle. The maximum error and standard deviation meet the clinical requirements. CONCLUSIONS: We demonstrate that the proposed method can accurately guide dentists to perform dental implant surgery.