Manufacturing Presentation

By the degradahon of hydrolysis of the ester bonds

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Unformatted text preview: asts which are present at the site of new bone formaHon that can produce minerals to calcify the collagen matrix to form the substrate for new bone; OsteointegraHon: The newly formed mineralized Hssue must be able to form an inHmate bonding with the implant material [40]; SCAFFOLDS cont’d BiocompaHbility: The lack of immunogenic response. The scaffold should be made of a material with appropriate rate of degradaHon in order to allow the surrounding Hssue eventually replace the scaffold [1]; The scaffold should be easily fabricated into various shapes and sizes [1]. Scaffold materials must be sterilizable in order to prevent infecHon. The scaffolds should possess minimum residues if chemicals are used to sterilize the samples. MATERIAL PROPERTIES FOR SCAFFOLDS If biodegradaHon is desired of implants, biocompaHble and biodegradable polymers can be used [9]. These polymers include poly(lacHc acid) (PLA) and poly(glycolic acid) (PGA) [9]. While selecHng a biodegradable polymer, apart from other required properHes, the degradaHon rate of the material is also very much important to see if it matches with the growth rate of the new Hssue [9,41]. PGA, PLA and their copolymers poly(lacHc acid- co- glycolic acid) (PLGA) are a family of linear aliphaHc polyesters, which are most frequently used in TE [9]. By the degradaHon of hydrolysis of the ester bonds, these polymers degrade [9]. MATERIAL PROPERTIES FOR SCAFFOLDS cont’d DegradaHon Process for the syntheHc polymers through ester hydrolysis [9]. R – COO – R’ + H2O - > [- COOH]R – COOH + HO – R’ Where - COOH represents carboxyl end group And - OH represents alcohol end group CalculaHon of degradaHon Hme [9]. Ln (Mn/Mno) = - k’t Where Mn = number average molecular weight at Hme t in Daltons (Da) Mno = iniHal number average molecular weight in Daltons (Da) k = rate constant t = degradaHon Hme MATERIAL PROPERTIES FOR SCAFFOLDS cont’d DegradaHon Process for the syntheHc polymers through ester hydrolysis [46]. POLYMER DEGRADATION DEGRADATION PRIMARY TISSUE METHOD TIME DEGRADATION ENGINEERING PRODUCT APPLICATIONS PGA ESTER HYDROLYSIS 1- 12 MONTHS GLYCOLIC ACID SKIN, CARTILAGE, BONE, ETC. PLA ESTER HYDROLYSIS 5- 60 MONTHS LACTIC ACID PLGA ESTER HYDROLYSIS 1- 12 MONTHS LACTIC ACID SKIN, AND GLYCOLIC CARTILAGE, ACID BONE, ETC. SKIN, CARTILAGE, BONE, ETC. RAPID PROTOTYPING TECHNOLOGIES Rapid Prototyping, also...
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This note was uploaded on 01/14/2014 for the course MECH 810 taught by Professor Various during the Fall '13 term at Queens University.

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