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Simona CavaluProfessor
Preclinical Sciences Department
Faculty of Medicine and Pharmaceutics
University of Oradea
ROMANIA
Motivation Development of an optimal interface between bone
and orthopedic or dental implant.
Determining whether a newly developed implantmaterial confirms to the requirements ofbiocompatibility, mechanical stability and safety.
The use of animal models is an essential step in testingorthopedic and dental implants prior to clinical usein humans.
Results from in vitro studies (cells culture) can bedifficult to extrapolate to the in vivo situations.
Factors for consideration when choosing an animal model
Implant design and surface texture
Animal selection: macrostructure, microstructure, bone composition, bone remodeling - similarities when comparing to the human bone
Costs to aquire and care for animals
Availability, acceptability to society
Tolerance to captivity and ease of housing.
International standard (ISO 10993-6) and Animal Protection Act.
Materials to be tested in this study Dense Al2O3-YSZ composites prepared by Spark Plasma Sintering
High performance biocomposite that combines the excellent material properties of alumina in terms of chemical stability and low wear and of zirconia with its superior mechanical strength and fracture toughness.
Alumina/zirconia ceramics were successfully used in total hip/knee arthroplasty in the last decades as alternative to metal devices.
For dental application: root canal posts, orthodontic brackets, implant abutments and all- ceramic restaurations.
Al2O3/ ZrO2 have been considered as bioinertceramics since they cannot induce apatite formation in SBF. They do however support bone cell attachment, proliferation and differentiation.
A. Gonzalez, 2010, Osteoblasts on bioceramic, Copyright Univ. of
Aberdeen
Materials characterization by SEM, XRD, FTIR, mechanical tests
Effect of CeO2 addition on densification and microstructure of Al2O3–YSZ composites, I. Akin, E. Yilmaz, F. Sahin, O.Yucel, G.Goller, Ceramics International 37 (2011) 3273–3280.
Correlation between structural properties and in vivo biocompatibility of alumina/zirconia bioceramics, S. Cavalu & all, Key Eng. Mater. 493-494 (2012) 1-6.
XRD and FTIR investigation of zirconia-taughenedalumina composites, V. Simon, S. Cavalu, I. Akin, O. Yucel, G. Goller, Studia UBB Physica, LVI, 1(2011)67-72.
SEM details of Al2O3 and Al2O3-YSZ composites (G. Göller & all, Istanbul Technical University)
Granules with irregular shape - small animal model protocol
Small animal model: Wistar rat
Collagen film
Collagen membrane
• S. Cavalu & all, In vitro study of collagen coating by electrodeposition on acrylic bone cement, Digest J. Nanomater. Biostruct (2011 ) 1, 89-97.• S. Cavalu & all, Bioactivity and antimicrobial properties of PMMA/Ag2O bone cement collagen coated, Digest J. Nanomater. Biostruct (2011 ) 2, 779-790.• S. Cavalu & all, Improving the bioactivity and biocompatibility of acrylic bone cement by collagen coating, Key Eng. Mater (2012) 493-494, 391-396.
Monitoring the osseointegration process at different time intervals (3, 6 weeks). Radiographic images
Post surgery fracture failure may occur
SEM images of the sheared implant surfaces
3 weeks after surgery
Ca/P= 1.60
6 weeks after surgery
Haversian canal detailsCa/P= 1.80
Histological images to detect any immunological or inflammatory responses
osteoblasts
A network of woven bony trabecular architecture with cellular infiltration was observed (H&E stain)
Bone marrow cells
SEM and Histological analysis revealed:
Fibrinous and collagenous matrix with three-dimensional interconnected porous structure after first 3 weeks.
Distinct gaps between the implant and the bone were observed in a few locations.
After 6 weeks, the matrix around the surface implanted area appeared more densely, well covered and integrated into a mixture of mineralized tissue, osteoidand dense matrix.
From the EDAX spectra, calcium/phosphate ratio is an indicative of the surface implant coverage for a successful osseointegration, varying from 1.7 (after 3 weeks) to 1.8 (after 6 weeks).
No clinical signs of inflammation or mobility were present. Newly
formed bone surrounded the implant surfaces, and many osteoblasts secreting osteoid matrix were observed.
Rabbit model The most commonly used model for medical research
(aprox. 35% of the musculoskeletal research studies –Al.Pearce, Eur Cells Mater 13 ,2007).
Histologically, rabbit long bones have a very differentmicrostructure from humans.
In comparison with other species, the rabbit has fasterskeletal change and bone turnover (significantintracortical, Haversian remodelling). This make itdifficult to extrapolate results from studies performed inrabbits onto the likely human clinical response.
Machined alumina/zirconia ceramics -cylindrical shape, suitable for rabbit model
Biomedical coatings
Alumina/zirconia ceramics are bioinert materials: once placed in the natural tissue, it has a minimal interaction with the surrounding tissue, generally a fibrous capsule might form around the implants.
Surface properties control the amount and quality of cells adhered on the implant and consequently, the tissue growth. Surface treatment techniques: sandblasting, acid-etched, organic (protein) or inorganic (Ca/P) coating.
Protein (fibrinogen) coating on alumina/zirconia ceramics
Rabbit model: surgical procedure
Radiographic images at 6 weeks
Histology: implant- bone marrow cells interaction
Histology: implant- host bone interaction
Goldner’s Trichrome stain
SEM/EDX bone-implant interface
Ca/P= 1.62
Ca/P= 1.77
Histological and SEM observations The presence of young, compact lamellar bone and
osteocytes near the implant surface indicated goodbiocompatibility, and certainly the presence of theimplant did not disturb the processes of bone formationat the interface.
Slight vascular congestion in contact with the bonemarrow, but no giant cells
Microstructure details (including Haversian canals) ofbone and bone marrow tissue and elemental compositionat the interface indicated Ca/P =1.62 - 1.77
Conclusions No animal species fulfils all of the requirements of an ideal
model, but an understanding of the differences in bonearchitecture and remodeling may assist in the selection of asuitable model for a defined research question.
Organic (proteic) film as surface conditioning might be analternative approach to induce the bioactivity and improvethe biocompatibility of dense bioceramics designed to
load bearing bone replacement (hip joint, dental abutments)and to optimize the biological response for specificapplications of biomedical implants.
The team:* Prof. dr. Viorica Simon and dr. Oana PontaBabes-Bolyai University, Faculty of Physics & Institute of Interdisciplinary Research in Bio-Nano-Sciences, Cluj-Napoca, Romania.
*Prof. dr. Gultekin Goller and assist. prof. Ipek Akin, Istanbul Technical University, Materials Science Department.
*Assist. prof. Cristian Ratiu , assist dr. Silviu Vlad and dr. Ioan Oswald University of Oradea, Faculty of Medicine and Pharmaceutics, Oradea, Romania.
Romania-Turkey Bilateral Cooperation 2011-2012 and CNCS-UEFISCDI project PNII-ID-PCE 2011-3-0441 contract nr. 237/2011 .
Wild rabbit in red wine sauce