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Biological and osseointegration capabilities of hierarchically (meso-/micro-/nano-scale) roughened zirconia

Authors Rezaei NM, Hasegawa M, Ishijima M, Nakhaei K, Okubo T, Taniyama T, Ghassemi A, Tahsili T, Park W, Hirota M, Ogawa T

Received 15 December 2017

Accepted for publication 28 March 2018

Published 8 June 2018 Volume 2018:13 Pages 3381—3395


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 3

Editor who approved publication: Dr Thomas Webster

Video abstract presented by Takahiro Ogawa.

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Naser Mohammadzadeh Rezaei, Masakazu Hasegawa, Manabu Ishijima, Kourosh Nakhaei, Takahisa Okubo, Takashi Taniyama, Amirreza Ghassemi, Tania Tahsili, Wonhee Park, Makoto Hirota, Takahiro Ogawa

Weintraub Center for Reconstructive Biotechnology, Division of Advanced Prosthodontics, UCLA School of Dentistry, Los Angeles, CA, USA

Purpose: Zirconia is a potential alternative to titanium for dental and orthopedic implants. Here we report the biological and bone integration capabilities of a new zirconia surface with distinct morphology at the meso-, micro-, and nano-scales.
Methods: Machine-smooth and roughened zirconia disks were prepared from yttria-stabilized tetragonal zirconia polycrystal (Y-TZP), with rough zirconia created by solid-state laser sculpting. Morphology of the surfaces was analyzed by three-dimensional imaging and profiling. Rat femur-derived bone marrow cells were cultured on zirconia disks. Zirconia implants were placed in rat femurs and the strength of osseointegration was evaluated by biomechanical push-in test.
Results: The rough zirconia surface was characterized by meso-scale (50 µm wide, 6–8 µm deep) grooves, micro-scale (1–10 µm wide, 0.1–3 µm deep) valleys, and nano-scale (10–400 nm wide, 10–300 nm high) nodules, whereas the machined surface was flat and uniform. The average roughness (Ra) of rough zirconia was five times greater than that of machined zirconia. The expression of bone-related genes such as collagen I, osteopontin, osteocalcin, and BMP-2 was 7–25 times upregulated in osteoblasts on rough zirconia at the early stage of culture. The number of attached cells and rate of proliferation were similar between machined and rough zirconia. The strength of osseointegration for rough zirconia was twice that of machined zirconia at weeks two and four of healing, with evidence of mineralized tissue persisting around rough zirconia implants as visualized by electron microscopy and elemental analysis.
Conclusion: This unique meso-/micro-/nano-scale rough zirconia showed a remarkable increase in osseointegration compared to machine-smooth zirconia associated with accelerated differentiation of osteoblasts. Cell attachment and proliferation were not compromised on rough zirconia unlike on rough titanium. This is the first report introducing a rough zirconia surface with distinct hierarchical morphology and providing an effective strategy to improve and develop zirconia implants.

Keywords: bone–implant integration, Y-TZP, hierarchical morphology, multi-scale rough, dental and orthopedic implant

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