The Accuracy of Implant Placement Dependent on the Sleeve Height

Objectives: The aim of this in vitro study was to evaluate the effect of guided sleeve height on the precision and reproducibility of static, computer-assisted implant surgery (sCAIS).
Methods: The pre- and post-operative implant positions of a total of n = 60 implants placed accordingly to a sCAIS protocol were recorded and compared. Implants were placed in identical replicas produced from a CBCT of a partially edentulous patient case. Surgical guides were planned with different sleeve heights of 2, 4, or 6 mm distance to the implant (coded as group H2, H4, and H6), respectively. Each n=20 Straumann Bone Level Guided implants were placed fully-guided in each group. The achieved implant position was digitized using a lab scanner (with an accuracy of 8ym) and compared with the planned position. Trueness (planned vs. actual position) and precision (difference among implants) were determined. The 3D-offset at the base of the implant (RMS between virtual pre-operative planning and post-operative STL-file) was defined as primary outcome parameter. The means, standard deviation, and 95%-confidence intervals were analyzed statistically with one-way ANOVA (trueness) or Scheffe’s procedure (precision).
Results: The differences (as 3D-offsets) between the planned and actual implant position (trueness) were at the implant base 0.22 ± 0.07 mm (H2), 0.45 ± 0.15 mm (H4), and 0.44 ± 0.15 mm (H6), respectively. The values for the sleeve heights of H4 and H6 were statistically different from H2 (p < 0.05). The differences (3D-offsets) among implants (precision) were 0.08 ± 0.07 mm (H2), 0.21 ± 0.15 mm (H4), and 0.20 ± 0.15 mm (H6), respectively. The H2 values were again significantly lower than for H4 and H6 (p < 0.05).

Conclusions: The static, computer-assisted implant surgery delivers predictable outcomes. The closer the sleeve to the implant position, the higher the accuracy of the method.