Theoreticals and experimentals researches concerning the assimilation of news biocompatibles materials using by RP technologies (Rapid Prototyping)

Transcription

1 Theoreticals and experimentals researches concerning the assimilation of news biocompatibles materials using by RP technologies (Rapid Prototyping) ing. BĂILĂ Diana Irinel, coordinator: Prof.dr.ing. BERCE Petru 1.Biomaterials with functional gradient used for the endobone personalized implants 1.1.Abstract The functionality of biomaterials must assure a good osteointegration of endobone implants used for the maxilo-facial and hip implants. Materials must present a gradient for porosity and one for composition (presents of a bioactive phase in titan matrix). The exterior porosity, in the contact zones with the bone tissue, favors the incipient cellular processes (the adhesion and attachment of osteoblastes, proliferation and cellular differentiation and nucleation of mineral bone). The pores must be open and with a specific surface more great. It s preferred the exterior intercommunicating porosity Titan powders On used titan powder for the probes. The diameters of pores in the zone of interface with the bone are determined for the new type of tissue who forms. If the pores are dimensions between 50 and 150µm, the cellular differentiation STEM favors the formation of osteoblastes. The optimal dimension is 150 µm. In the case when the contact zone is viable, the cells extend the contact surface greating. On create new focal points and determine a cellular attachment more stable. Number of attachment cells of surface great to the proliferation the viable cells by attraction the new cells. In the case when the dimension pores are little that 100µm, the bone become nonviable. It s difficult to form the haversien blood canals. In time, the bone necroses and the implant are mobilized between 2-5 years. The interior of implant what is not in contact with the tissues must have a sufficient mechanical resistance to assure the mechanical stability of implant in organism. The presence of calcium phosphates in the contact zone of implant with the zone favors the nucleation of the bone mineral. Fig.1.Probes of titan sinterised, the powder granulation >100 µm Fig.2.Probe of titan sinterised, the powder granulation>100µm, frontal surface(x50) Page 1

2 1.2.2.Composite Ti-hidroxyapathite On use a material of implant with bioactive comportment in the bone tissue, having a matrix of titan and hidroxiapathite particles. Because hidroxiapathite has faible mechanical properties, his presence must to be only in the exterior zone of implant who is in contact with the bone. On realize probes sinterised of titan with different fraction <63 µm and >100 µm. The powder was desiccated in ethyl ether and granulometric sort. On press the probes using pressions like 230, 300 and 350 MPa. The probes presses to 230 MPa are milled, don t present a good mechanical stability.(fig.1,2) The sinterisation process was realized in vid to The probes are warm to 1300 C, for 60 minutes, then are chill slow, in vid. At the temperature 800C, after the temperature of titan transformation α β (882 C), was realized a intermediary interval of 30 minutes. Fig.3.Lateral surface, granulation<100µm (x30) Fig.4.The fine longitudinal fissures 300MPa(x50) The probes what are compacted to pression of 300 MPa, in figure 3 don t present fissures. The probes what are compacted to pression great that 350 MPa, in figure 4 are presented fines fissures. When we greating the pression value, on remark the fissures becomes greats (fig.5,6), because are developed the remanent tensions cause of friction between powder-punch. For the maximal pression of compactation, appear longitudinal fissures and transversal fissures (fig.7,8). Fig.5.Transversal fissures (x30) Fig.6.Transversal fissures (x50) Page 2

3 Fig.7. Transversal and longitudinal fissures Fig.8.Transversal and longitudinal fissures The longitudinal fissures are grace of radial efforts cause of insufficient deformability of the fine powder to press. The transversal fissures are cause of intern frictions of powder in time of pression. The probes sinterised porosity of titan is 12,1%. The probes with a 100 µm granulation present great porosity, inclusive for a compactation of 350MPa. On obtain a medium porosity of 14.4% for 300 MPa and 14% for 350 MPa. On remark a direct correlation between the value of pores and the powders granulation used. On observe the powder granulation influence the sinterised piece porosity. For realize the probes with porosity gradient is necessary alimentation the matrix with different granulations of powder. On realize too, the compacts Ti-hidroxyapathite, for study the phenomen of interface in time of sinterisation. On use the hydrurated powder of titan, with great granulation more than 100 µm. The hidroxyapathite powder was obtain by technique sol-gel, than milled. Fig.9. Composite probes of Ti 5% HA On realize an admixture with 5%HA (massic procent), who was homogenized 30 minutes. On obtain compacts using the pressions of 400, 500, 600 MPa. (fig.9) The probes are sinterised in vid to The chill is slow, in vid, to the temperature of 20C. On remark a tendency of expansion in sinterisation time. Page 3

4 Fig.10. Composite Ti 5% HA, 400 MPa (SEM and EDX) (x50) Fig.11.Composite Ti-5%HA, 600MPa (SEM and EDX) (x50) On remark the interface diffusion by SEM and EDX microscopy between phosphates of calcium and titan matrix, in function of the compactation pression (fig.10, 11). To pression of MPa, the granules present a no modified forms. To 600 MPa, the ceramic phase is pound. If the pression grow the compactation of probes grow too. It s proved of diffusion acceleration because of deformation to titan mesh. The phenomen can be observed in EDX spectrogram. Interface Ti-HA is stable, grace of gradual pass by diffusion layer. The probes with 5% and 20%HA are sinterised completely, having a good mechanical stability. For the probes with 50 %HA, the mechanical resistance is not sufficient, because it s passed the titan capacity to mix the ceramic phase. 1.3.Conclusions For obtain implants with concentration gradient of hidroxyapathite and sufficient mechanical stability, is necessary a lent transition to a concentration to other concentration. For this, is necessary a special dispositive to admission of matrix or bunkers, in case of sinterisation SLS. Page 4

5 2.Biocompatibility of implants titan-hidroxyapathite 2.1.Abstract Using the Rapid Prototyping technics and the tomographe images, on obtain the 3D virtual models and by sinterisation on produces the real models. For an implants it s important that only the parts who is în contact with the bone must have hidroxyapathite, like bioactive phase with osteoconductive importance. The presence of bioactive phase permets realizations of new calcium phosphates. The surface analysis present the calcium phosphates growth, if the implants stay în SBF. The implants of Ti-HA have a better biocompatibility that anothers metallic implants. 2.2.Caractherisation of Ti-HA implants The powders Ti-HA are used in implantology, for fingers and for mandibular implants. (fig.1,2,3) On remark that only the parts în contact with the bone must be realized by hidroxyapathite like a bioactive phase with osteoconductive importance. The exteriour will have maximum 20% HA and this concentration is gradual lowered. It s not admit a decrease more great than 5%HA by a layer to another, because exist the risk to fissure between layers. Fig.12.Model 3D mandibular prothesis Fig.13. Models 3D phalangeal prothesis Fig.14. Artificial phalangeal implants Fig.15. Fracture in mandibular graft Page 5

6 The probes present a mixt structure, with a matrix of titan and dispersed ceramics particles, like in figure (4,6). EDX analysis of implant fragments present a splitting a part of initial hidroxyapathite, with the P and Ca diffusion în titan matrix.(fig.5,7,8) Fig.16. EDX Analysis, in mandibular graft Fig.17.Fracture in phalangeal graft Fig.18. EDX analysis in phalangeal graft, interior zone Page 6

7 Fig.19. EDX analysis in phalangeal graft, exteriour zone In figure 8 remarks a great concentration de hidroxyapathite and calcium phosphates. By comparation of elements cantity in control zone of artificial phalangeal implant observe the diffusion of Ca and P was more important, proportional for the exterior zones. By DRX analysis, remarks for a greater concentration of hidroxyapathite, after sinterisation present a structure with a greater cantity of calcium phosphates. (fig.9) Quantitative results Quantitative results Weight% Weight% Si P Ca Ti 0 Si P Ca Ti a. b. Fig.20. The cantitative results for the artificial phalangeal implant : a- zone with 10% HA initial; b- zona 20% HA initial On makes probes with constant concentration (5, 10, 15, 20% HA) to study the bioactivity în simulated organic fluid (SBF). On remark the presence of bioactive phase and realization of new calcium phosphates. (fig.10, 11,12) Page 7

8 Fig.21. Probe with 5%HA after 7 days in SBF Fig.22. Probe with 10%HA after 7 days in SBF EDX analysis of probes surface introduse în SBF present the calcium phosphates în great cantity.(fig.12) Fig.23.EDX analysis for the probes with 5%HA and with 10%HA after 7 days în SBF 2.3.Conclusions The rapport Ca/P is greater for the probes with 10%HA that for the probes with 5%HA. The rapport Ca/P grows after immersion, in SBF for 7 days for all types of probes. A maximum it s remark for the probes with 10%HA, where the rapport was growing very match. Bibliography 1) Berce P. si altii: -Fabricarea Rapidă a Prototipurilor- Editura Tehnică, Bucureşti 2000; 2) Ratner Buddy D. si altii- Biomaterials Science An introduction to materials in medicine Academic Press, 1996; Page 8