Zygomatic implants, either alone or in combination with dental implant placement, have emerged as a viable surgical option for elderly patients with severe bone atrophy for occlusal restoration. This study aims to examine the biomechanical impact of the three-dimensional contact area between zygomatic implants and bone on biomechanics under different surgical methods.

Using Cone Beam Computed Tomography (CBCT) images from 10 patients with severe bone atrophy, we reconstructed 3D maxillary bone models and created corresponding 3D zygomatic implant models. Two distinct surgical methods (extramaxillary or intrasinus approaches) were employed based on the position and angle of the zygomatic implant for each patient. The 3D bone-to-implant contact percentage (BIC%) was calculated, and finite element analysis with nonlinear contact was conducted to assess the relationship between 3D BIC% and surrounding bone stress for both surgical methods.

The 3D BIC% of extramaxillary approach (57.63 %) and intrasinus approach (56.49 %) for total bone (including cortical and cancellous bone) was similar (P = 0.425) in zygomatic implant surgery. In contrast, the intrasinus method exhibited higher 3D BIC% in cortical bone contact (28.08 %) compared to the extramaxillary approach (21.92 %) (P = 0.011). The correlation between 3D BIC% and high bone stress was stronger in the intrasinus approach, likely due to increased contact area in cortical bone.

The intrasinus approach led to lower bone stress and a more robust correlation between bone stress and 3D BIC%, particularly in cortical bone contact. Importantly, the coverage area of cortical bone surrounding the zygomatic implant significantly influenced biomechanical performance of the zygomatic implants.