Evaluating the accuracy of a novel marker-free registration technique for dynamic computer-assisted implant surgery: An in vitro study.

Objectives: To propose a novel marker-free cusp-and-surface registration (CSR) technique for dynamic computer-assisted implant surgery (dCAIS) and to evaluate its accuracy in vitro.

Methods: Forty implants were inserted into twenty 3D-printed models designed to simulate maxillary anterior partial edentulism, using a dynamic navigation system that employed either the CSR or cusp registration (CR) technique. The CR group employed six reference points on six teeth adjacent to the edentulous ridge as reference structures. The CSR group required only four reference teeth, one reference point per tooth, and four to five reference surfaces. The evaluation included linear and angular deviations between the planned and actual implant locations. The registration times for CSR and CR were documented and analyzed. Group comparisons were conducted using the independent sample t-test or the Mann-Whitney U test.

Results: The CSR group yielded average entry, apex, and axis deviations of 0.51 ± 0.23 mm, 0.59 (0.45-0.71) mm, and 2.22 ± 0.65°, while the corresponding deviations of the CR group were 0.55 ± 0.31 mm, 0.60 (0.46-0.82) mm, and 1.80 ± 0.79°, respectively (P > 0.05). No significant differences between the groups were observed in angular or linear deviations, except for the apex mesio-distal deviation. The CSR group showed a considerable reduction in apex mesio-distal deviation relative to the CR group [0.17 (0.10-0.23) vs. 0.31 (0.19-0.41) mm; P = 0.006]. Registration duration differed significantly between groups, with an average length of 3.48 ± 0.77 min for the CR group and 4.60 ± 0.65 min for the CSR group (P < 0.05).

Conclusion: The CSR method, using four reference teeth, provides in vitro accuracy comparable to that of the CR technique, which employs six reference teeth, thus decreasing the required number of remaining reference teeth for effective registration.

Clinical Significance: Considering the limitations of this in vitro study, the CSR strategy provides accuracy comparable to the more conventional marker-free registration approach while reducing the number of remaining reference teeth needed. The CSR method shows promise as an effective registration technique in dCAIS, potentially expanding the scope of marker-free registration.