BIOACTIVE GLASS 13-93 FIBERS enon is caused by the stress distribution, which is a result of 4. Xynos ID, Hukkanen MJJ, Batten JJ, Buttery LD, Hench LL, density differences in the different layers of the fiber caused Polak JM. Bioglass 45S5 stimul turnover and by cooling. For thinner fibers, the cooling is more rapid than enhances bone formation in vitro d applications this may also cause the difference in 5. Hench LL Biomaterials: a forecast for the rength properties. In technical glass fiber manufacturing, the 998:19:1419-1423 ooling of the fibers is normally done by spraying water 6. Vita Finzi Zalman E, Locardi B, Gabbi C, Tranquilli Leali P. raight to the fiber when draining out from the nozzle, and Bioactive vitreous composition for bone implants, filaments nis further decreases the cooling time of thin fibers Another made therefrom and method. PCT Wo 91/12032. 1991 7. Brink M. Bioactive Glasses with a Large Working range. benefit of manufacturing technical grade glass fibers is the Doctoral Thesis. Turku, Finland: Abo Aka use of sizing agents to cover the formed fiber surface already within the fiber spinning process. The reported tensile 8. Brink M, Turunen T, Happonen R-P, Yli-Urpo A Com ength for technical sized E-glass fiber is-2 GPa or above tional dependence of bioactivity of glasses in the system Na,O for glass fibers with a diameter of -15 um. The reported K2O-Mgo-CaO-B2O3-P2Os-Sio med Mater Res 1997 37:114-121 Weibull modulus for technical E-glass fibers is -5.522.23 De 9. Brink M, Yli-Urpo S, Yli-Urpo A. The resorption of a bioactive Diego et al. have studied the tensile properties of 45S5 lass implanted into rat soft tissue. In the 5th World Biomate- MPa, with the Weibull modulus being between 3.0 and 3.5. 10. Brink M, Laine p otg K, Yli-Urpo A. Implantation of bio- Bioglass. The obtained tensile strength was at the level of 90 The tested fibers were thick, from 165 to 310 um.4 The ctive and inert glass fibres in rats-Soft tissue response and Weibull modulus for the manufactured bioactive glass 13-93 short term reactions of the glass. In: Sedel L, Rey C, editors fibers tested in this study is rather low, m= 2, which Bioceramics. New York: Elsevier Science: 1997. Vol 10, p 61-64 represents considerable uncertainty about the stress level at 11. Pirhonen E, Grandi G, Tormala P. Bioactive glass fibre/poly- which a fiber is likely to fail. As glass fibers are highly sensitive to abrasion and flaws drastically affect the strength 12. Pirhonen E, Moimas L, Haapanen J Porous bioactive 3-D glass properties, it would be beneficial to use sizing or coupling agents for bioactive glass fibers by sintering technique. Key Eng Mater 2003: 240-242: 237-240. 13. Kokubo T. Kushitani H. Sakka S. Kitsugi. Yamamuro T Solu- tions able to reproduce in vivo surface-structure changes in bioactive glass-ceramic A-w. J Biomed Mater Res 1990: 24 CONCLUSIONS 721-734 14. Hull D, Clyne Tw. An Introduction to Composite Materials, In this work, fiber manufacturing process for bioactive glass 15. Hench LL, Andersson 0. Bioactive glasses. In: Hench L,Wil- 13-93 was developed. Strong glass fibers with a diameter son j. editors. An Introduction to Bioceramics. S adjustable from 20 to 300 um were successfully manufac World Scientific Publishing: 1993 tured Bioactive glass 13-93 fibers with a diameter of -250 16. Izquierda-Barba I, Salinas A, Vallet-Regi M In vitro calcium um retained their flexural strength up to 3 weeks in SBF and phosphate layer formation on sol-gel glasses of the Cao-Sio system J Biomed Mater Res 1999: 47: 243-24 started to decrease in strength after that. However, there Is 17. Dunn RL, Cassper RA, Kelley BS. Biodegradable composites only minor strength loss within 7-40 weeks immersion in In the llth Annu Mtg Soc Biomater, San Diego, CA, Apri SBF. The flexural modulus started to decrease when the fibers 25-28,1985.p213 were immersed in SBE The change in mass when immersed 18. Lin TC. Totally absorbable fibre reinforced composite for in- in SBF was proportional to the surface area of the samples, termal fracture fixation devices. In the 12th Annu Mtg Soc rather than the total volume of the samples. As the degrada- Biomater, Minneapolis-St Paul, MN, May 29-June 1, 1986. p tion rate of the samples is determined by the diffusion of ions 19. Krebs S, Lin S, King R Characterization of HA and resorbable from the surface, the degradation of the material can be glass fibers reinforced PLLA screws In the 19th Annu Mtg Soc djusted by controlling the surface area/volume ratio and wall Biomater, April 28-May 2, Birmingham, AL, 1993. P 317 hickness of bioactive glass structures. Marcolongo M, Ducheyne P, Garino J, Schepers E. Bioactive glass fibre/composites bond to bone tissue. J Biomed Mater Res The authors thank mrs. tiina aaltonen for the technical assis- 1997:37:440-448 tance and Dr. Kari Kolppo for help with the compositional analysis. 21. Jarvela P. Properties of Glass Fibres and Their Applications in Porous Composites, Doctoral Thesis. Tampere, Finland: Tam- REFERENCES 22. Pardini LC, Manhani LGB. Infiuence of the testing gage length on the strength, Youngs modulus and Weibull modulus of 1. Hutmacher Dw. Scaffolds in tissue engineering bone and car- carbon fibres and glass fibres. Mater Res 2002: 5: 411-420 lage. Biomaterials 2000: 21: 2529-2543 23. Gurvich MR. Dibenedetto at. Pegoretti A. Evaluation of the 2. Bonassar LJ. Vacanti CA. Tissue engineering: The first decade statistical parameters of a Weibull distribution. J Mater Sci and beyond. J Cell Biochem Suppl 1998: 30/31: 297-303. 1997:32:3711-3716 3. Hench LL. Bioactive materials: The potential for tissue regen- 24. De Diego MA, Coleman NJ, Hench LL. Tensile eration. In the 24th Annu Mtg Soc biomater. San Diego, CA, bioactive fibres for tissue engineering applications. J Biomed 1998.p5l1-518 Mater Res B Appl Biomater 2000: 53: 199-203enon is caused by the stress distribution, which is a result of density differences in the different layers of the fiber caused by cooling. For thinner fibers, the cooling is more rapid than for thicker fibers, and this may also cause the difference in strength properties. In technical glass fiber manufacturing, the cooling of the fibers is normally done by spraying water straight to the fiber when draining out from the nozzle, and this further decreases the cooling time of thin fibers. Another benefit of manufacturing technical grade glass fibers is the use of sizing agents to cover the formed fiber surface already within the fiber spinning process. The reported tensile strength for technical sized E-glass fiber is
2 GPa or above for glass fibers with a diameter of
15
m. The reported Weibull modulus for technical E-glass fibers is
5.5.22,23 De Diego et al. have studied the tensile properties of 45S5 Bioglass®. The obtained tensile strength was at the level of 90 MPa, with the Weibull modulus being between 3.0 and 3.5. The tested fibers were thick, from 165 to 310
m.24 The Weibull modulus for the manufactured bioactive glass 13–93 fibers tested in this study is rather low, m  2, which represents considerable uncertainty about the stress level at which a fiber is likely to fail. As glass fibers are highly sensitive to abrasion and flaws drastically affect the strength properties, it would be beneficial to use sizing or coupling agents for bioactive glass fibers. CONCLUSIONS In this work, fiber manufacturing process for bioactive glass 13–93 was developed. Strong glass fibers with a diameter adjustable from 20 to 300
m were successfully manufac￾tured. Bioactive glass 13–93 fibers with a diameter of
250
m retained their flexural strength up to 3 weeks in SBF and started to decrease in strength after that. However, there is only minor strength loss within 7– 40 weeks immersion in SBF. The flexural modulus started to decrease when the fibers were immersed in SBF. The change in mass when immersed in SBF was proportional to the surface area of the samples, rather than the total volume of the samples. As the degrada￾tion rate of the samples is determined by the diffusion of ions from the surface, the degradation of the material can be adjusted by controlling the surface area/volume ratio and wall thickness of bioactive glass structures. The authors thank Mrs. Tiina Aaltonen for the technical assis￾tance and Dr. Kari Kolppo for help with the compositional analysis. REFERENCES 1. Hutmacher DW. Scaffolds in tissue engineering bone and car￾tilage. Biomaterials 2000;21:2529 –2543. 2. Bonassar LJ, Vacanti CA. Tissue engineering: The first decade and beyond. J Cell Biochem Suppl 1998;30/31:297–303. 3. Hench LL. Bioactive materials: The potential for tissue regen￾eration. In the 24th Annu Mtg Soc Biomater, San Diego, CA, 1998. p 511–518. 4. Xynos ID, Hukkanen MJJ, Batten JJ, Buttery LD, Hench LL, Polak JM. Bioglass 45S5 stimulates osteoblast turnover and enhances bone formation in vitro. Implications and applications for bone tissue engineering. Calcif Tissue Int 2000;67:321–329. 5. Hench LL. Biomaterials: A forecast for the future. Biomaterials 1998;19:1419 –1423. 6. Vita Finzi Zalman E, Locardi B, Gabbi C, Tranquilli Leali P. Bioactive vitreous composition for bone implants, filaments made therefrom and method. PCT WO 91/12032, 1991. 7. Brink M. Bioactive Glasses with a Large Working Range, Doctoral Thesis. Turku, Finland: Åbo Akademi University; 1997. 8. Brink M, Turunen T, Happonen R-P, Yli-Urpo A. Composi￾tional dependence of bioactivity of glasses in the system Na2O￾K2O-MgO-CaO-B2O3-P2O5-SiO2. J Biomed Mater Res 1997; 37:114 –121. 9. Brink M, Yli-Urpo S, Yli-Urpo A. The resorption of a bioactive glass implanted into rat soft tissue. In the 5th World Biomate￾rials Congress, Toronto, 1996. p 48. 10. Brink M, Laine P, Narva K, Yli-Urpo A. Implantation of bio￾active and inert glass fibres in rats—Soft tissue response and short term reactions of the glass.In: Sedel L, Rey C, editors. Bioceramics. New York: Elsevier Science; 1997. Vol 10, p 61– 64. 11. Pirhonen E, Grandi G, To¨ rma¨la¨ P. Bioactive glass fibre/poly￾lactide composite. Key Eng Mater 2001;192–195:725–728. 12. Pirhonen E, Moimas L, Haapanen J. Porous bioactive 3-D glass fibre scaffolds for tissue engineering applications manufactured by sintering technique. Key Eng Mater 2003;240 –242:237–240. 13. Kokubo T, Kushitani H, Sakka S, Kitsugi, Yamamuro T. Solu￾tions able to reproduce in vivo surface-structure changes in bioactive glass-ceramic A-W3 . J Biomed Mater Res 1990;24: 721–734. 14. Hull D, Clyne TW. An Introduction to Composite Materials, 2nd ed. Cambridge: Cambridge University Press; 1996. 15. Hench LL, Andersson O¨ . Bioactive glasses. In: Hench L, Wil￾son J, editors. An Introduction to Bioceramics. Singapore: World Scientific Publishing; 1993. 16. Izquierda-Barba I, Salinas AJ, Vallet-Regi M. In vitro calcium phosphate layer formation on sol-gel glasses of the CaO-SiO2 system. J Biomed Mater Res 1999;47:243–244. 17. Dunn RL, Cassper RA, Kelley BS. Biodegradable composites. In the 11th Annu Mtg Soc Biomater, San Diego, CA, April 25–28, 1985. p 213. 18. Lin TC. Totally absorbable fibre reinforced composite for in￾ternal fracture fixation devices. In the 12th Annu Mtg Soc Biomater, Minneapolis-St. Paul, MN, May 29 –June 1, 1986. p 166. 19. Krebs S, Lin S, King R. Characterization of HA and resorbable glass fibers reinforced PLLA screws. In the 19th Annu Mtg Soc Biomater, April 28 –May 2, Birmingham, AL, 1993. p 317. 20. Marcolongo M, Ducheyne P, Garino J, Schepers E. Bioactive glass fibre/composites bond to bone tissue. J Biomed Mater Res 1997;37:440 – 448. 21. Ja¨rvela¨ P. Properties of Glass Fibres and Their Applications in Porous Composites, Doctoral Thesis. Tampere, Finland: Tam￾pere University of Technology; 1983. 22. Pardini LC, Manhani LGB. Influence of the testing gage length on the strength, Young’s modulus and Weibull modulus of carbon fibres and glass fibres. Mater Res 2002;5:411– 420. 23. Gurvich MR, Dibenedetto AT, Pegoretti A. Evaluation of the statistical parameters of a Weibull distribution. J Mater Sci 1997;32:3711–3716. 24. De Diego MA, Coleman NJ, Hench LL. Tensile properties of bioactive fibres for tissue engineering applications. J Biomed Mater Res B Appl Biomater 2000;53:199 –203. BIOACTIVE GLASS 13–93 FIBERS 233