Mixtures For Forming Porous Constructs

Abstract

Provided are methods comprising at least one metal powder with an extractable material and a composition comprising a polyol, a hydrophilic polymer, or both in order to form a mixture in which the metal powder and the extractable material assume respective positions. The composition functions as a homogenizing agent that allows the mixture to remain well-mixed for extended periods of time under ambient conditions. Also provided are green bodies and porous constructs, including implants, that are made in accordance with the disclosed methods. The green bodies and porous constructs have a substantially uniform porosity that is at least partially attributable to the ability of the composition to maintain the metal powder and the extractable material in their respective positions prior to sintering.

1 . A method comprising combining at least one metal powder with an extractable material and a composition comprising a polyol, a hydrophilic polymer, or both, thereby forming a mixture in which said metal powder and said extractable material assume respective positions. 
   
   
       2 . The method according to  claim 1  wherein a subcombination of said metal powder and said extractable material is formed prior to combining said metal powder and said extractable material with said composition. 
   
   
       3 . The method according to  claim 2  wherein said subcombination comprises metal powder in an amount that is about 5 percent by volume to about 45 percent by volume of said subcombination. 
   
   
       4 . The method according to  claim 2  wherein said subcombination is formed as a substantially homogeneous blend of said metal powder and said extractable material. 
   
   
       5 . The method according to  claim 1  further comprising subjecting said mixture to one or more of blending, shaking, and stirring. 
   
   
       6 . The method according to  claim 1  wherein said composition comprises a polyol in an amount that constitutes about 10 percent by volume to about 70 percent by volume of said composition. 
   
   
       7 . The method according to  claim 1  wherein said polyol is glycerol, sorbitol, mannitol, xylitol, inositol, polyol sucrose, lactitol, maltitol, ethylene glycol, propane-1,2-diol, propane-1,3-diol, butane-1,4-diol, butane-1,3-diol, butane-2,3-diol, butene-1,4-diol, butine-1,4-diol, pentane-1,5-diol, an isomeric pentanediol, pentenediol, or pentinediol, hexane-1,6-diol or an isomeric hexanediol, hexenediol or hexinediol, heptane-1,7-diol, an isomeric heptanediol, heptenediol or heptinediol, octane-1,8-diol, an isomeric octanediol, octenediol, or octinediol, trimethylol propane, pentaerythritol, or any combination thereof. 
   
   
       8 . The method according to  claim 1  wherein said polyol is glycerol. 
   
   
       9 . The method according to  claim 1  wherein said composition comprises a hydrophilic polymer in an amount that constitutes no more than about 5 percent by volume of said composition. 
   
   
       10 . The method according to  claim 1  wherein said hydrophilic polymer is a polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, a sodium salt of polyacrylic acid, a sodium salt of carboxyl methyl cellulose, a sodium salt of alginic acid, a sodium salt of hyaluronic acid, polyether polyol, polyether polyol modified with hydrophilic vinyl monomer, polytetramethylene polyol, or any combination thereof. 
   
   
       11 . The method according to  claim 1  wherein said metal powder comprises titanium, a titanium alloy, a cobalt-chromium alloy, aluminum, molybdenum, tantalum, magnesium, niobium, zirconium, stainless steel, nickel, tungsten, or any combination thereof. 
   
   
       12 . The method according to  claim 1  wherein said extractable material comprises ammonium bicarbonate, urea, biuret, melamine, ammonium carbonate, naphthalene, sodium bicarbonate, sodium chloride, ammonium chloride, calcium chloride, magnesium chloride, aluminum chloride, potassium chloride, nickel chloride, zinc chloride, ammonium bicarbonate, sodium hydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, potassium hydrogen phosphate, potassium hydrogen phosphite, potassium phosphate, magnesium sulfate, potassium sulfate, alkaline earth metal halides, crystalline carbohydrates, polyvinyl alcohol, polyethylene oxide, polypropylene wax, sodium carboxymethyl cellulose, or any combination thereof. 
   
   
       13 . The method according to  claim 1  further comprising:
 shaping said mixture into a shaped object; and,   compacting said shaped object to form a green body.   
   
   
       14 . A green body prepared in accordance with the method of  claim 13 . 
   
   
       15 . The method according to  claim 13  further comprising processing said green body. 
   
   
       16 . The method according to  claim 13  further comprising heating said green body for a time and under conditions effective to evaporate at least some of said extractable material yet substantially maintain said metal powder in its position in said green body. 
   
   
       17 . The method according to  claim 13  further comprising exposing said green body to a solvent in which said extractable material is soluble. 
   
   
       18 . The method according to  claim 17  wherein said extractable material is soluble in an aqueous solvent, an organic solvent, or both. 
   
   
       19 . The method according to  claim 17  wherein said green body is immersed in said solvent. 
   
   
       20 . The method according to  claim 17  wherein said composition is soluble in said solvent. 
   
   
       21 . The method according to  claim 17  wherein the green body has a total porosity of about 50% to about 95%. 
   
   
       22 . The method according to  claim 21  wherein the green body has a substantially uniform porosity. 
   
   
       23 . The method according to  claim 22  wherein the porosity of said green body varies by a standard deviation of less than about 3. 
   
   
       24 . The method according to  claim 22  wherein the porosity of said green body varies by a standard deviation of less than about 2. 
   
   
       25 . The method according to  claim 16  further comprising sintering said green body. 
   
   
       26 . An implant made in accordance with the method of  claim 25 . 
   
   
       27 . A mixture made in accordance with the method of  claim 1 .