[Accuracy of dynamic navigation-assisted trephine method for bone harvesting]

To evaluate the positional accuracy of dynamic navigation-assisted trephine bone harvesting in the symphysis and external oblique ridge.

Ten standardized mandibular models were 3D-printed using polyetheretherketone (PEEK), mimicking natural mandibular mechanical properties. Pre-operative cone beam CT (CBCT) scans (70 kV, 70 mA, 0.25 mm×0.25 mm ×0.25 mm voxel) were acquired, and data were imported into dynamic navigation software (Dcarer, China). Two donor sites were designed in both the symphysis (≥15 mm from anterior teeth) and external oblique ridge (≥6 mm from molars), with 8 mm-diameter, 6 mm-deep cylindrical osteotomy tracts planned for each site.After calibrating the navigation system with 20 mm and 50 mm spherical burs, an 8 mm outer-diameter trephine prepared 40 tracts under real-time guidance. Post-operative CBCT scans were taken, and Mimics 20.0 software fitted actual tracts to standard cylinders. Superimposing actual and designed tracts via metal registration markers, we measured coronal/apical center point deviation, depth deviation, and axis angle deviation in order to compare site-specific accuracy.

Deviations of the dynamic navigation-assisted trephine method for bone harvesting was (1.91±0.69) mm at the coronal center point, (1.54±0.66) mm at the apical center point, (－0.83±0.77) mm at the depth of the apical center point and 3.02°±0.38° at the axis angle. The four deviations in symphysis and external oblique ridge were (1.32±0.36) mm and (2.50±0.35) mm at the coronal center point (P < 0.01), (1.06± 0.31) mm and (2.02±0.56) mm at the apical center point (P < 0.01), (－0.30±0.52) mm and (－1.38±0.57) mm at the depth of apical center point (P < 0.01), 3.03°± 0.38° and 3.00°± 0.39° at axis angle (P=0.80).

Within the limitations of this study, dynamic navigation-assisted trephine harvesting shows good accuracy. The symphysis exhibits higher accuracy than the external oblique ridge, possibly due to surface morphology and operability differences. These findings support its clinical potential, but future clinical studies are needed to validate results.