Comparison of zirconia and titanium implants after a short healing period. A pilot study in minipigs

Insertion of a zirconia implant, applying a ratchet.

Measurement of the relative bone-volume density within the grooves (yellow) compared with the region of reference (RoRef; red).

Non-submerged zirconia implant. Polarized light image of the crestal soft–hard tissue junction. A tight structural compound between connective tissue and the implant neck is visible. The fibres are oriented perpendicular to the implant surface, but when approaching the surface, the orientation changes to parallel. The crestal bone appears rounded with a minor interposition of connective tissue between the zirconia surface and the crestal bone. Peri-implant sulcular fibres are oriented parallel to the implant axis (Masson–Goldner stain, magnification 10×).

Submerged zirconia implant. Polarized light image at the transition zone between peri-implant connective tissue and bone. The periosteal fibres extend into the bone. Apical of the crestal bone region, this parallel fibre orientation remains identical and the fibres are in direct contact with the surface. At the implant–bone interface, fibres emerge from the periosteum and progress into the peri-implant connective tissue (Masson–Goldner stain, magnification 10×).

(a) Zirconia implant, submerged (left). At the crestal implant area, a tightly surface-adapted connective tissue is present. No crestal bone resorption can be found. Bordering the connective tissue zone, bone lamellae extend to the apical region and form a close BIC. No intervening connective tissue can be found (Masson–Goldner stain, magnification 4×). (b) Zirconia implant, non-submerged (right). Along the polished implant neck region, a proliferation of connective tissue can be observed. At the connective tissue implant surface interface, an empty zone without any structures represents an artifact and is due to the fixation process. The tight structural connection of the soft tissue to the implant surface is visualized by remnants of connective tissue at the implant surface. The threads show direct contact to the host bone in the crestal region. Owing to the geometry of the drill, distance osteogenesis is present around the implant body (Masson–Goldner stain, magnification 4×).

Submerged zirconia implant, upper third. Both contact and distance osteogenesis are visible. Osteoid zones that represent the youngest areas of bone formation directly border the implant threads. A direction of bone growth from the host bone to the implant body can be concluded (Masson–Goldner stain, magnification 10×).

Titanium implant, submerged. In the crestal region, a cuff-like adaptation of peri-implant connective tissue is present. This extends to the rough implant neck surface. This is bordered by direct BIC. The middle and lower third of the implant show signs of osteoneogenesis by immature lamellar bone (Masson–Goldner stain, magnification 4×).