 biomaterial design for some time. A microstructure that can stimulate the healing process and promote tissue growth while being made from a material that will eventually degrade is attractive. Unfortunately, highly porous materials inherently have low strength which can be a major detriment. Another major hurdle to be overcome is the poor handleability of porous scaffolds as they easily break when handled, can easily get tangled together, and ultimately become ineffective for the intended purpose. The majority of the orthopedic industry uses dense particles of cadaver bone, calcium phosphate based ceramics, or bioactive glass in their devices as they have the required strength and handleability required during surgery.
The use of silicate based bioactive glasses such as 45S5 and S53P4, are currently used in products approved by the US Food and Drug Administration and other world safety organizations for use in implantable devices such as orthopedic implants and are known to be capable of making three dimensional porous scaffolds. Glasses with compositions similar to 45S5 and S53P4 crystallize rapidly when heated above each glasses respective glass transition temperature (Tg), making viscous sintering by traditional heat treatments difficult without crystallization. Therefore, currently there are no amorphous, rigid, and porous scaffolds composed of silicate glasses are commercially available. Glasses with wider working ranges with multiple alkali and alkaline earth elements in combination with additional silica have been developed to fill the need, but these glasses convert to hydroxyl apatite (HA) slower than 45S5 and S53P4, and none of these scaffolds are in currently available products approved by the FDA for any clinical market.
Silicate glass particles that are larger than >500 μm can take years to fully react with body fluids and be converted to the inorganic component of bone known as hydroxyapatite (HA) because, large particles of glass (>500 μm) leave voids in healing tissue that take years to remodel into natural tissue, and the large particles have a relatively small surface area mass ratio and don't allow for tissue penetration by bone or blood vessels.
Porous scaffolds allow for tissue penetration, and the surface area available for reaction with body fluids is relatively large and penetrates throughout the entire scaffold, which significantly reduces conversion time to HA and final remodeling. The conversion kinetics of silicate glass 45S5 to HA has been shown to slow from the contracting volume model to the diffusion model once the silica gel layer achieves a thickness great enough to become the diffusion barrier. This is the reason why a porous scaffold composed of 45S5 will convert to HA in a matter
biomaterial design for some time. A microstructure that can stimulate the healing process and advertise tissue increase while being made from a material that will finally degrade is attractive. Unfortunately, highly holey materials inherently have broken persuasiveness which can be a major detriment. Another major hurdle to be get the better of is the poor handleability of porous scaffold as they easily break when handle, can well get tangled together, and ultimately become ineffective for the mean purpose. The majority of the orthopedic industry use dense particles of cadaver bone, calcium phosphate based ceramics, or bioactive looking glass in their devices as they have the required military capability and handleability required during surgery. 
 The use of silicate based bioactive glasses such as 45S5 and S53P4, are presently used in products approved by the US Food and Drug Administration and other world safety constitution for use in implantable devices such as orthopedic implants and are known to be capable of making three dimensional porous scaffolds. Glasses with compositions alike to 45S5 and S53P4 crystallize rapidly when heat above each glass respective glass transition temperature (Tg), making syrupy sintering by traditional heat treatments difficult without crystallization. consequently, currently there are no amorphous, rigid, and porous scaffolds composed of silicate glasses are commercially available. Glasses with wider working ranges with multiple alkali and alkaline earth element in combination with additional silica have been develop to fill the need, but these glasses convert to hydroxyl apatite (HA) slower than 45S5 and S53P4, and none of these scaffold are in currently available products approved by the FDA for any clinical grocery store. 
 Silicate glass particles that are larger than > 500 μm can take year to fully react with consistency fluids and be converted to the inorganic part of bone known as hydroxyapatite (HA) because, large particles of glass (> 500 μm) forget voids in bring around tissue that take years to recast into natural tissue, and the large particles have a relatively small surface area mass ratio and don't allow for tissue penetration by bone or blood vessels. 
 holey scaffolds allow for tissue penetration, and the open area available for reaction with body fluids is relatively large and penetrates throughout the entire scaffold, which importantly reduces conversion time to HA and final remodeling. The conversion kinetics of silicate glass 45S5 to HA has been shown to slow from the catching volume model to the diffusion model once the silica gel layer achieves a thickness great enough to become the diffusion barrier. This is the reason why a holey scaffold composed of 45S5 will convert to HA in a matter
 bilmaterial design for somt time. A microstrocrure tiat can stimulage the healing process and pcomore tiwsue growth while beine made frlm a matwriao that will eventually defvade ns attractive. Unnortunately, highly porous mxtzrials inherently have low strength rhich csn be a major dejrimeme. Anknhtr major hurdle to be overcome is the pomr handleabiloty of porous scaffolds as thej easily break whej handled, cqn ewwily get taneled together, and ultijately become ineffective for tfe incended purpisw. Tjg majority oh the jrthopedic ikcustry uses drnse particles of caeaver bone, calcium phmsphate based ceraiics, or bhocctive glass in their dwvicev as theh haxe uhe rsquiref svrength and handleabiluty required during stgbery.
The use kf silycwte based bioactive glasses such as 45S5 atd A53P4, are currently used ib products approved bi the US Fjod and Drug Administration and other world safetf orgenkzauiins fue kse in implantable devices such as orthopedic jmklakts and are knowk to be capable of mwkogg three dimevsional pkrous scaffolds. Glwsses wyth cimpositiogs somilar to 45S5 and S53P4 crystalluze rapidly cheb heated above eack glasses rerpecjive gkass transition temperacure (Tf), making vidcous sinfdring by traditiunak veat treatments difficult rithout ccystaklizatiun. Tnerefowe, currentpy thcse are no amorphoud, rignd, ang porous sfaffolds composed of silicate glasses are comkescidlly avanlable. Glasses with wider working ranges with multiple zlkali end alkaline earth elemendd in combinavion with addutiobal silkza have been drveloped no filo the need, but thexe emasses convert cu hydroxyl apatiye (FA) fllwxr thwt 45S5 and S53P4, atd nune pf thdse scaffolbs are in currently availatle lroducts approved ny the FDA for any clinical marlet.
Silicate glass karticnes that arg larger than >500 μm can take years to fully rewct with bodr flmids and be couverted to the inorganic component of boie known as hydroxyapajite (HA) because, large karticles of jlass (>500 μm) leave eoids in healing tiswue that take yeavs to remodel into nathral thssue, and the large particles have a relatively small surface area mass ratio qnd doi't allow for fissie petecracion by bonx ur blood vessels.
Iorous scaffolds allow for tissux penetrathou, and the surface area availanld for reactiov with body fluids is rematively large and penetrates throughouy the entire scaffold, whlch signidicanfly reducer conversion time yo HA cnd fibal remidellng. The converriom ninetics lf smlieate glass 45S5 to HA has been shown to sliw from the contrarting volume oodel to thg diffusion model oncs the rilica gel lauer achieves a thickness great enolgh to become the siffusion batrier. Jkps is the reaxon why a pmrous scaffold composed of 45S5 will convert to HA in z matter
biomaterial design for some time. A microstructure stimulate healing process promote tissue growth material will eventually degrade attractive. Unfortunately, highly materials inherently have low strength which be a major detriment. Another major hurdle to be overcome is the poor of porous scaffolds as they easily break when handled, can easily get tangled and become for intended purpose. The majority of the orthopedic industry uses dense particles of cadaver bone, calcium phosphate ceramics, or bioactive glass in their devices as have the required strength handleability required during surgery. The of based bioactive such 45S5 S53P4, are currently in products approved by the US Food and Drug Administration and other world safety organizations for use implantable devices orthopedic implants are to capable of making porous scaffolds. Glasses with compositions similar S53P4 crystallize rapidly when heated above each glasses glass transition (Tg), making viscous sintering by traditional treatments difficult without crystallization. Therefore, currently there are amorphous, rigid, and porous scaffolds composed of silicate glasses are commercially available. Glasses with wider with multiple alkali and earth elements in with silica been to fill need, but these glasses convert to hydroxyl apatite (HA) slower than and S53P4, and none of these scaffolds are in currently approved the FDA for clinical market. Silicate glass that larger than >500 μm years fully fluids be to the inorganic component bone known as hydroxyapatite (HA) large particles of glass healing tissue that take years to remodel into tissue, and the large particles have a small surface area mass ratio and don't allow for tissue penetration by or blood scaffolds allow for tissue penetration, and the surface available for reaction with fluids is relatively large and penetrates throughout the entire which reduces conversion to HA and remodeling. The conversion of silicate glass HA has shown slow volume model to the diffusion model the gel layer achieves a thickness enough the diffusion barrier. This is the reason why a porous scaffold composed of 45S5 will HA in a matter
 biomaterial design for some tIme. A microsTructUre ThaT cAn stImulAte the healing pROcesS and promote tissue growtH whilE bEIng mADe From a MateriaL ThAT WilL eVeNtuAlLY dEgradE is AttractIve. UnfortuNatElY, highly porouS MaTerials inhEreNtly have low sTreNgth whIcH caN Be a maJor DetriMent. AnOTher maJor hurdle To BE overcOMe is the POOr HandLeability of porous SCaFFolds as they easIly breAk WHeN HAndLed, Can easily gEt TanglED togethER, aND ULtiMAtely become inEffective foR The IntendEd PurPOse. The MajorItY Of tHe orthopediC indUstry uses Dense pARticles OF cadaveR bone, cAlcIum PhosPHaTe BasEd CEraMIcS, or BIoaCtive glaSs In Their DeviCES AS theY haVe thE requIred strength aNd hAndlEAbiLity rEquirEd duRiNg surGery.
ThE use oF sIlicate based bioActiVe glasses SucH aS 45S5 aNd s53P4, are CUrrentLy uSed In produCts apprOVed By THE uS food and Drug AdminisTrATIoN and otheR world SAfEtY OrganizaTiOns For uSE In impLantABlE devices Such as ORtHoPedic imPlAnts anD aRe kNowN to be CApabLe of maKing threE dimeNSional porous scAFfolds. Glasses WItH COmPOsitIonS similar to 45S5 And S53p4 CrysTallIZe RapIDly whEn heaTeD AbOVe each glasses respecTiVe glasS tranSition temperaTure (Tg), makiNG VIscous siNterINg BY traditional heAt treAtments difFIcult witHout cRystalliZation. TheREFore, currEntLy tHerE arE NO aMorphous, rigid, AND porOuS scaffoLds ComposeD of SilIcaTe gLaSses are coMmercialLy AvAiLaBle. glassES with widEr WorKiNg rAnges WIth mulTiple AlkaLi AnD AlkAline eaRTh ELEmenTs In CombInaTiOn witH addITioNal siliCa have beeN deVElopEd To Fill the Need, but these gLaSses converT tO hyDroxyl APAtite (HA) sLower than 45S5 and S53P4, and none oF These scAffOlds aRe in Currently AvaIlable ProDUcts apProved By the fDa foR ANy cliNICaL maRkEt.
Silicate GLAss PartiClEs thAt are laRger than >500 μm can take yEArs To fully react wIth Body FLUiDs aND bE ConVeRTed TO The inorganic comPonent of boNe KNoWn as hydroxYApaTiTe (HA) becAuse, larGe parTIcles of Glass (>500 μm) leAve voids iN hEaliNG TisSue that takE years to Remodel inTO natuRAl TissuE, anD the laRgE paRticlEs have A RelAtiveLy smalL sUrface Area mAsS ratio anD don't allow for tissue peneTratioN by boNe oR blood vesSelS.
porOus scaffoLds aLlow for tisSue PenEtratIon, ANd the SurfACe AreA AvailAble FOr reactioN WiTh bODY fLuids is relaTIVEly Large And PEnetraTes tHroughout the entirE Scaffold, which sIgniFICanTly REducEs Conversion time To Ha aND Final remOdEling. The conVersion kInETics oF silicAte glaSs 45S5 to HA HAS bEEn showN to sLow From the coNtrAcTIng voluMe MoDEl to thE difFuSion moDel oncE The sILIca gel layer achieVes a tHICknesS GreAt enoUgH to becoME the Diffusion bArrier. This iS the reAson Why a pOrous scAfFold coMpoSeD of 45S5 will coNVert to HA iN a matTer
 biomaterial design for so me time. A  micr ost ruc tu re t hatcan stimulatet he h ealing process and pro moteti s sueg ro wth w hile be i ng m ade  f ro m a  m a te rialtha t willeventually  de gr ade is attra c ti ve. Unfort una tely, highly  po rous m at eri a ls in her ently  havel ow str ength whi ch can be a major d et rime nt. Another major hu r dle to be over come i st he p oor  ha ndleabilit yof po r ous sca f fo l d s  as they easily b reak when h a ndl ed, ca neas i ly get  tang le d  to gether, and  ult imately b ecomei neffect i ve forthe in ten ded  pur p os e.  Th em ajo r it y o f  th e orthop ed ic  indu stry u s e s de nse  par ticle s of cadaverbon e, c a lci um ph ospha te b as ed ce ramics , orbi oactive glass i n th eir devic esas  th ey  have the re qui red  streng th andh and le a b i li ty required during  s u r ge ry.
Theuse of si li c ate base dbio acti v e  glas sess uc h as 45S 5 andS 53 P4 , are c ur rently  u sed  in  prod u ctsapprov ed by th e USF ood and Drug A d ministrationa nd o th e r wo rld  safety org aniz a tion s fo r  u sei n imp lanta bl e  d e vices such as ortho pe dic im plant s and are kno wn to be c a p a ble of m akin g  t h ree dimensiona l por ous scaffo l ds. Glas ses w ith comp ositionss i milar to  45 S5and  S5 3 P 4crystallize r a p idly  w hen hea ted  aboveeac h g las ses  r espective  glass t ra ns it io n t emper a ture (Tg ),  ma ki ngvisco u s sint ering  bytr ad i tio nal hea t  t r e atme nt sdiff icu lt  with outc rys talliza tion. The ref o re,cu rr ently t here are no a mo rphous, ri gi d,and po r o us scaff olds composed of silica t e glass esare c omme rcially a vai lable.  Gl a sses w ith wi der w or kin g range s wi thmu ltiple alk a l i a nd al ka line  earthelements in combin a tio n with additi ona l si l i ca  ha v eb een  d e vel o p ed to fill theneed, butth e se  glasses c o nve rt  to hyd roxyl a patit e  (HA) s lower tha n 45S5 an dS53P 4 ,  an d none ofthese sc affolds a r e inc ur rentl y a vailab le  pr oduct s appr o ved  by t he FDA  f or any  clin ic al marke t.
Silicate glass parti cles t hat a relarger th an> 500  μm can t akeyears to f ull y r eactwit h  body  flu i ds  an d  be c onve r ted to th e  i nor g a ni c component o f  bo ne kn own as hyd roxy apatite (HA) beca u se, large part icle s ofgla s s (> 50 0 μm) leave vo ids  i n healingti ssue that t ake year st o rem odel i nto na tural t i s su e , andthelar ge partic les  h a ve a re la ti v ely sm allsu rfacearea m a ss r a t io and don't all ow fo r tissu e  pe netra ti on by b o ne o r blood ve ssels.
Poro us sca ffol ds al low for  t issuepen et ration, an d  the surf ace a rea ava il able  fo r reac tion w ith b odyfl uid s is rela t i ve l yla r geandpenet ra testhroughou t  the ent ire scaffol d,  wh i c h sign i fi c a ntly reduc esconve r s ion time t o  HAa nd final  remod eling.  The co n ver si on kine tic s of silica te glass4 5S5  t o HA  has bee nshow ntosl ow from the con tracting  volumem o del to  th e  dif f usionmo del once the  sili ca gel lay e r  ac hievesa  th ick nes s gr eat  eno u gh to become the diffusi on b arrie r . T his i s the  r eason wh y  a p orous sc a ffold compose d of 45S5 willc onv e rt t o H A  i na matter
 biomaterial_design for_some time. A microstructure_that can_stimulate_the healing_process_and promote tissue_growth while being_made from a material_that will eventually_degrade_is attractive. Unfortunately, highly porous materials inherently have low strength which can be a_major_detriment. Another_major_hurdle_to be overcome is the_poor handleability of porous scaffolds_as they_easily break when handled, can easily get tangled_together,_and ultimately become_ineffective for the intended purpose. The majority of the_orthopedic industry uses dense particles of_cadaver bone, calcium_phosphate_based_ceramics, or bioactive glass_in their devices as they have_the required strength and handleability required_during surgery.
The use of silicate based bioactive_glasses such as 45S5 and S53P4,_are currently used in products_approved by_the US Food and Drug_Administration and other_world safety_organizations for use_in implantable devices such as orthopedic_implants and are_known to be capable of making_three_dimensional porous scaffolds._Glasses_with_compositions similar_to 45S5 and_S53P4_crystallize rapidly_when_heated above each glasses respective glass_transition_temperature (Tg), making viscous sintering by traditional_heat treatments difficult without_crystallization._Therefore, currently there are_no amorphous, rigid, and porous_scaffolds composed of silicate glasses are_commercially available._Glasses with_wider working ranges with multiple alkali and alkaline earth elements in_combination with additional silica have been_developed to fill the_need, but_these_glasses convert to_hydroxyl_apatite (HA)_slower than 45S5 and S53P4, and none_of these_scaffolds are in currently available products_approved by the FDA_for_any clinical market.
Silicate glass particles that_are larger than >500 μm can_take years to fully react_with_body_fluids and be converted to_the inorganic component of bone known_as hydroxyapatite (HA)_because, large particles of glass (>500 μm)_leave_voids in healing tissue that take_years_to remodel into natural tissue, and_the_large_particles have a relatively small_surface area mass ratio and don't_allow for tissue penetration by bone or blood vessels.
Porous_scaffolds allow for_tissue penetration, and the surface_area_available_for reaction with body fluids is relatively large and penetrates_throughout the_entire scaffold, which_significantly reduces conversion time to HA and final remodeling. The_conversion kinetics of silicate glass 45S5 to_HA has been shown to slow from the contracting volume model_to the diffusion model once the silica gel_layer achieves a thickness great enough to_become the diffusion barrier._This_is the reason why a porous scaffold_composed_of_45S5_will convert to_HA in a_matter