The research of upgraded or new bioceramics is related to the crucial topic of the enhancement of life conditions.
The two ceramic materials in clinical use today as bearing surfaces are aluminium oxide and zirconium oxide.
So everybody is searching for the ideal bioceramic that combines the properties of both. Because of the extensively reported long term success in the orthopedic field (more than 20 years), it has been used in dentistry …….
In this context, we propose an evaluation of the structural properties and biocompatibility of new zirconia toughened alumina ceramics. The composition….. Materials were prepared in Biomaterials Research Center ITU by using spark plasma sintering.
FTIR and XRD…… SEM and EDAX for microstructure and morphology. Grain size and densification degree as a result of TiO2 adition to alumina zirconia matrix. The rat model has been accepted as a model for the effects of systemic disease on osseointegration. -SEM Histo
XRD spectra shows reflection lines occurring from crystallographic planes related to alpha alumina and tetragonal zirconia. The addition of TiO2 slightly modifies the relative intensities of the peaks.
-The FTIR spectrum is dominated by the absorption lines arising from alumina phase. The stretching vibration of Al-O bonds are related to the tetrahedral or octahedral groups. Stretching vibration of Zr- O bonds in tetragonal phase. -TiO2 addition to alumina/zirconia matrix is reflected in relative intensity of the 660/614 as a superposition of the characteristics bands in this range.
In order to perform in vivo tests, both materials were used as granular, irregular shaped, filling the defects created in in the femur of Wistar rats. The microstructure of the granules is presented, along with the EDAX spectrum for each sample.
As a surgical procedure, a critical size defect was made in the femur, using a dental drill, under constant irrigation of cold saline to avoid thermal necrosis and to remove the debris.
Upon filling the defects, a collagen thin film was placed on the top, and then muscle and skin were sutured in layers.
In order to monitor the osseointegration process in vivo, radiographic images were recorded at different time intervals after the surgical procedure.
The femur was harvested for SEM. The defects were microscopically evaluated with respect to filling of the defect with new bone. We can notice the contour/ the edge line of the implanted area and the details with different magnification. After 3 weeks, distinct gaps between the implanted area and the original bone were observed in a few locations. The defects are covered with a layer of soft tissue. A fibrinous and collagenous matrix extensively interdigitated in a three dimensional structure is observed. The details reveal that our material (grain) seems to be swallowed by the natural bone. Notice the Ca/P ratio in the EDAX spectrum=1.57
After 6 weeks, the matrix around the implant area appeared more densely, well covered and extensively integrated into a mixture of mineralized tissue , osteoids and dense matrix. It seems that TiO2 addition to alumina/zirconia matrix is favorable to the oseointegration process, as the aspect of the implanted area is more uniform. Notice the Ca/P ratio = 1.9
Up- image was taken from the original bone, unaffected by the surgical procedure. Below- image taken from the surface of the new bone covering the implanted area.
SEM images reveals that the materials are well integrated in the original bone
The XRD pattern of the harvested femur shows characteristic lines of the Al Zr and hydroxyapatite compared with the pattern of pure biocomposite and those of original bone unaffected by surgery.
No signs of inflammatory reaction such as necrosis or reddening suggesting implant rejection were found upon histological examination. The periosteal regions were completely closed with new blood capillaries around the implant site. Osteoblast- like cells are the evidence of new bone formation.
SIMONA CAVALU_Correlation between structural properties and in vivo biocompatibility of alumina/zirconia bioceramics
Correlation between structural properties and in vivo biocompatibility of alumina/zirconia bioceramics Simona Cavalu Professor Preclinical Sciences DepartmentFaculty of Medicine and Pharmaceutics University of Oradea ROMANIA
Motivation There is a continuous input from bioengineering for reaching a high level of comfort, improving reliability, finding new applications. This development is also a response to the growing number of patients afflicted with traumatic or non- traumatic conditions: the number of implants is continuously growing, due to the increase in persons suffering of arthritis and joint problems. As the average age of population grows, the need for medical devices to replace damaged or worn tissues increases. As patients have become more and more demanding regarding esthetic and biocompatibility aspects of their dental restorations
Motivation Al2O3 ZrO2 Excellent hardness and Was introduced to overcome wear properties. the limitations of alumina. Fracture toughness values When properly manufactured, are lower than those of zirconia has a higher strength, the metals used in but only 50% of alumina’s orthopedic surgery. hardness. Chemical and Unstable material. The hydrothermal stability. tetragonal phase tends to It is a brittle material, transform into the monoclinic phase. The addition of with low resistance to the stabilizing materials propagation of cracks. (Y2O3)during manufacture, can control the phase transformation of zirconia. Al2O3, ZrO2, TiO2 have been considered as bioinert ceramics since they cannot induce apatite formation in SBF. They do however support bone cell attachment, proliferation and differentiation.
The ideal ceramic is a high performance biocomposite that combinesthe excellent material properties of alumina in terms of chemicalstability and low wear and of zirconia with its superior mechanicalstrength and fracture toughness. Alumina/zirconia ceramics were successfully used in total hip/knee arthroplasty in the last decades. For dental application: root canal posts, orthodontic brackets, implant abutments and all- ceramic restaurations.
Goal An evaluation of the structural and biocompatibility properties of a new zirconia toughened alumina ceramics. The composition of proposed materials for this study: 90%Al2O3-10%ZrO2 and 90%Al2O3-10%ZrO2+5%TiO2 prepared by using modern processing technologies – spark plasma sintering.
Methods Investigation of the structural changes induced by TiO2 addition to Al2O3/ ZrO2 are made by FTIR spectroscopy and X- ray diffraction (XRD) analysis . Scanning Electron Microscopy (SEM) and EDX are used for microstructure and morphology investigation of the samples. In order to perform in vivo tests, the rat model has been applied for biocompatibility evaluation. The rat model has been accepted as a model for the effects of systemic disease on osseointegration. SEM micrographs are recorded on the rats femur along with the elemental composition of the sheared implant surfaces at different time intervals after the surgery. Histological examination of the connective tissue is performed to detect any immunological or inflammatory responses.
Results: XRD Spectroscopy XRD patterns of (a) 90Al2O3∙10ZrO2 and (b) 90Al2O3∙10ZrO2 + 5%TiO2 samples. 1200 Z A The TiO2 addition slightly A Z modifies the relative intensities 1000 of XRD peaks. Both samples A A show similar peak positions, 800 A Z A A the slight change of relative Z A A intensities of XRD peaks could be attributed T to weakIntensity (a.u.) Z A 600 Z A A Z (a) differences in size and shape of the crystals in these samples 400 A A A A A This result suggest that 200 Z A zirconia present in the T Z A composite is, therefore, 0 A (b) retained in the tetragonal form as alumina particles prevent 0 10 20 30 40 50 60 70 80 90 100 the tetragonal to monoclinic 2 theta (degrees) transformation by matrix constraint.
FTIR Spectroscopy: (a) 90Al2O3∙10ZrO2 and (b) 90Al2O3∙10ZrO2 + 5%TiO2 samples. The large bands around 1088 cm-1 are assigned to stretching vibration of Al–O–Al bonds. The Al-O stretching vibrations of 465 0.6 1088 tetrahedral AlO4 groups are 614 660 related with the bands in the 780 1168 region 900 – 750 cm-1 and 564 518 797 0.5 bands in 650 – 460 cm-1 regionIntensity (a.u.) (a) are associated with stretching modes of AlO6 octahedra. 0.4 The absorption bands at 518 to 564 cm-1 correspond to Zr-O vibrations in tetragonal ZrO2 0.3 phase. (b) Upon TiO2 addition to alumina- zirconia matrix, the relative 0.2 intensity of 660/614 cm-1 band 1200 1000 800 Wavenumber (cm ) -1 600 400 is considerably modified, as a superposition of the characteristics absorption bands occurs in this region.
SEM: Irregular shape of 90%Al2O3-10%ZrO2(a) and 90%Al2O3-10%ZrO2+5%TiO2 (b) granules and their corresponding microstructure (c, d)a) c)b) d)
Biocompatibility evaluation: Animal model (Wistar rats) Surgical procedure
Surgical procedure: filling the critical size defect created in the femurCollagen film
Monitoring the osseointegration process at different time intervals (3, 6 weeks). Radiographic images90Al2O3∙10ZrO290Al2O3∙10ZrO2 + 5%TiO2
SEM images of the sheared implant surfaces: 3 weeks 90Al2O3∙10ZrO290Al2O3∙10ZrO2 + 5%TiO2
SEM images of the sheared implant surfaces: 6 weeks 90Al2O3∙10ZrO290Al2O3∙10ZrO2 + 5%TiO2
SEM Analysis reveals: Fibrinous and collagenous matrix extensively interdigitated with the 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 extensively integrated into a mixture of mineralized tissue, osteoid and dense matrix. As revealed from the EDAX spectra, calcium/phosphate ratio is an indicative of the surface implant coverage for a successful osseointegration, varying from 1.5 (after 3 weeks) to 1.9 (after 6 weeks). The results suggest that TiO2 presence in the samples favor the osseointegration process.
XRD spectrum of the femoral bone 900 800 Z AlZr Biocomposite 700 A A Z Z A A A A A A T Z 600 500 Z Bone/AlZr I (a.u.) B Z Z A A A 400 A B A AZ 300 * 200 * Bone 100 0 0 20 40 60 80 100 2Θ (deg)
Histological images: The connective tissue was also examined to detect any immunological or inflammatory responses osteoblastsA network of woven bony trabecular architecture with cellular infiltrationwas observed
Conclusions Structural investigations of the proposed composites using XRD and FTIR spectroscopy confirms the stability of the microstructure upon TiO 2 addition to alumina/zirconia matrix. In vivo: both implanted materials in critical size defect of the femur were well integrated in the original bone defects and covered with a layer of soft tissue at 6 weeks after implantation, as demonstrated by SEM images. As revealed from the EDAX spectra, Ca/P ratio is an indicative of the surface implant coverage for a successful osseointegration, varying from 1.5 (after 3 weeks) to 1.9 (after 6 weeks). No signs of inflammatory reactions, such as necrosis or reddening suggesting implant rejection, were found upon histological examination.
The team: Prof. dr. Gultekin Goller and dr. Ipek Akin, Istanbul Technical University, Materials Science Department. Prof. dr. Viorica Simon and dr. Oana Ponta Babes-Bolyai University, Faculty of Physics & Institute of Interdisciplinary Research in Bio-Nano-Sciences, Cluj-Napoca, Romania. Assoc. prof. Cristian Ratiu and dr. Ioan Oswald University of Oradea, Faculty of Medicine and Pharmaceutics, Oradea, Romania. Romania-Turkey Bilateral Cooperation project 385/2010.