A natural bone cement--a laboratory novelty led to the development of revolutionary new biomaterials.Research on calcium phosphate chemistry at NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. led to the discovery of the worlds first self-hardening calcium phosphate cements (CPC (1) (Central Processing Complex) An IBM mainframe that has two or more central processors (CPs) that share memory. It is the collection of processors, memory and I/O subsystems manufactured with a single serial number, typically all contained in one cabinet. ) in 1987. Laboratory, animal, and clinical studies were conducted to develop CPC into clinically useful biomaterials. The combination of self-hardening capability and high biocompatibility biocompatibility
the quality of not having toxic or injurious effects on biological systems.
biocompatibility 1. The extent to which a foreign, usually implanted, material elicits an immune or other response in a recipient 2. makes CPC a unique material for repairing bone defects. Near perfect adaptation of the cement to the tissue surfaces in a defect, and a gradual resorption resorption /re·sorp·tion/ (re-sorp´shun)
1. the lysis and assimilation of a substance, as of bone.
n. followed by new bone formation are some of the other distinctive advantages of this biomaterial. In 1996 a CPC, consisting of tetracalcium phosphate and dicalcium phosphate anhydrous an·hy·drous
Without water, especially water of crystallization.
adj without water.
containing no water. , was approved by the Food and Drug Administration (FDA FDA
Food and Drug Administration
n.pr See Food and Drug Administration.
n.pr the abbreviation for the Food and Drug Administration. ) for repairing cranial cranial /cra·ni·al/ (-al)
1. pertaining to the cranium.
2. toward the head end of the body; a synonym of superior in humans and other bipeds.
adj. defects in humans, thus becoming the first material of its kind available for clinical use. This paper will review the course of the development, the physical and chemical properties, and clinical applications of CPC.
Key words: biomaterial; bone graft bone graft Orthopedic surgery Sterilized bony tissue, often of cadaveric origin, used to fill and/or 'sculpt' bone defects Indications Spinal fusion, revision of failed articular prostheses, filling traumatic or malignant bone defects, or periodontal defects. ; bone repair; dicalcium phosphate anhydrous; hydroxyapatite hydroxyapatite /hy·droxy·ap·a·tite/ (-ap´ah-tit) an inorganic calcium-containing constituent of bone matrix and teeth, imparting rigidity to these structures. ; self-setting calcium phosphate cement; tetracalcium phosphate.
In the early 1980s, Brown and Chow of the American Dental Association American Dental Association (ADA),
n.pr a nonprofit professional association whose membership is dental professionals in the United States. Its purpose is to assist its members in providing the highest professional and ethical care to the citizens of the Health Foundation Paffenbarger Research Center (ADAHF-PRC) at the National Institute of Standards and Technology National Institute of Standards and Technology, governmental agency within the U.S. Dept. of Commerce with the mission of "working with industry to develop and apply technology, measurements, and standards" in the national interest. (NIST) conducted studies on calcium phosphates aimed at developing remineralizing pastes to repair early dental carious car·i·ous
Having caries; decayed.
adj pertaining to caries or decay. lesions. Based on the solubility properties of calcium phosphates (1), they formulated mixtures containing tetracalcium phosphate (TTCP TTCP The Technical Cooperation Program (US DoD)
TTCP Technology Transfer Control Plan
TTCP Test Transmission Control Protocol
TTCP Test Training Certification Plan
TTCP Tailored Technical Criteria Profile
TTCP Test Tcp ), [Ca.sub.4][([PO.sub.4]).sub.2]O, and dicalcium phosphate anhydrous (DCPA DCPA Denver Center for the Performing Arts (Denver, CO, USA)
DCPA Defense Civil Preparedness Agency
DCPA Dicalcium Phosphate Anhydrous
DCPA Dallas Center for the Performing Arts ), [CaHPO.sub.4], or TTCP and dicalcium phosphate dihydrate. When mixed with water these mixtures would rapidly form hydroxyapatite (HA), [Ca.sub.5][([PO.sub.4]).sub.3]OH, which is the major component of tooth mineral, at body temperatures. It was observed that some of the pastes became a hardened mass when left in test tubes for a few hours. Thus, the PRC scientists inadvertently discovered a new type of self-hardening cement that consisted of only calcium phosphates and formed HA as the only product.
Since Brown and Chow reported the first CPCs in 1987 (2), many different combinations of calcium and phosphate-containing compounds have been investigated as potential CPC materials and the properties of the various cements were studied. A large number of publications on CPC have appeared in the last several years, which have been summarized in (3) and (4), reflecting a sharp increase in the interest in CPC research. This paper provides a brief review of the chemistry, properties and applications of the CPC based on TTCP + DCPA.
2. Chemistry of Setting Reaction of CPC
The setting reactions of CPC may be understood by analyzing the solubility of the individual cement components such as TTCP and DCPA. The solubility phase diagram showing the solubility curves of TTCP, DCPA and HA is given in Fig. 1. Each curve describes the solubility of a salt, expressed as the calcium concentration of the saturated solution as a function of pH. At a given pH, a salt whose isotherm isotherm, line drawn on a map of a particular region of the earth's surface connecting points of equal temperature; each point reflects one temperature reading or an average of several readings over a period of time. lies below that of another salt is less soluble (thermodynamically ther·mo·dy·nam·ic
1. Characteristic of or resulting from the conversion of heat into other forms of energy.
2. Of or relating to thermodynamics. more stable) than the other. The point where two isotherms cross is known as a singular point. The solution at the singular point is saturated with respect to both salts, which are equally stable at this solution composition. The fact that HA is the least soluble salt over a wide range of pH explains why the major mineral component of both normal hard tissues and pathological calcified Calcified
Hardened by calcium deposits.
Mentioned in: Heart Valve Repair deposits are impure im·pure
adj. im·pur·er, im·pur·est
1. Not pure or clean; contaminated.
2. Not purified by religious rite; unclean.
3. Immoral or sinful: impure thoughts. forms of HA. When the pH falls below approximately 4.2, DCPA becomes the least soluble. TTCP is the most soluble salt at pH below 9. The relativ e stability of these two salts is the major driving force for the setting reactions that occur in calcium phosphate cements. Generally, both TTCP and DCPA are considerably more soluble (less stable) than HA at pH above 4.2. As a result, a solution saturated with respect to TTCP (or DCPA) is supersaturated su·per·sat·u·rate
tr.v. su·per·sat·u·rat·ed, su·per·sat·u·rat·ing, su·per·sat·u·rates
1. To cause (a chemical solution) to be more highly concentrated than is normally possible under given conditions of temperature and with respect to HA. This would lead to HA precipitation and the major driving force for the CPC setting, which, in turn, would make the solution undersaturated Un`der`sat´u`ra`ted
a. 1. Not fully saturated; imperfectly saturated. with respect to TTCP and cause more TTCP to dissolve to re-attain saturation. Thus, it is the relative solubility of the various salts that provides the driving force for the setting reactions that occur in CPC.
In addition to being highly soluble in neutral and acid pHs, TTCP is the only calcium phosphate salt that has a Ca/P ratio higher than that of HA. Thus, it plays a special role as a cement component in that only TTCP can be combined with other calcium phosphate salts with lower Ca/P ratios such as DCPA to formulate a mixture that has the stoichiometry stoichiometry
Determination of the proportions (by weight or number of molecules) in which elements or compounds react with one another. The rules for determining stoichiometric relationships are based on the laws of conservation (see of HA. Formation of HA in such a mixture, given by Eq. (1), does not release acidic or basic by-products.
[Ca.sub.4][([PO.sub.4]).sub.2]O+[CaHPO.sub.4][right arrow][Ca.sub.5][([PO.sub.4]).sub.3]OH (1)
As long as both DCPA and TTCP are present in excess and the rates of dissolution of these two salts are greater than the rate of HA formation, the solution composition would remain near or at the singular point for these two salts (Fig. 1) and the conversion of DCPA and TTCP to HA would continue. Thus, the liquid phase of the cement would remain at a near constant pH and composition, allowing the HA formation to proceed at a steady rate (5). The singular point pH for the TTCP + DCPA is approximately 8. Thus, during the HA formation, the pH of the cement would only be slightly higher than the physiological pH, and this may contribute to the high biocompatibility observed for CPC.
Setting of the TTCP + DCPA cement with water as the liquid phase occurred in about 30 mm at 37[degrees]C, and the conversion of the starting materials to HA was almost completed in 4 h (5). During this period, the cement setting reaction proceeded at a near-constant rate, suggesting that the reaction rate was limited by factors that are unrelated to the amounts of the starting materials and the reaction products present in the system. Such factors could be, for example, the particle sizes of DCPA or TTCP.
3. CPC Materials
A CPC usually consists of a powder and a liquid phase. The powder phase is an equimolar e·qui·mo·lar
Having an equal number of moles. mixture of TTCP and DCPA or mass fractions of 0.729 of TTCP and 0.271 of DCPA. TTCP is prepared by heating a mixture of commercially available DCPA (#) (Baker Analytical Reagents, J. T. Baker Chemical Co., NJ, U.S.A.) and calcium carbonate calcium carbonate, CaCO3, white chemical compound that is the most common nonsiliceous mineral. It occurs in two crystal forms: calcite, which is hexagonal, and aragonite, which is rhombohedral. , [CaCO.sub.3], (J. T. Baker Chemical Co.) at 1500[degrees]C for 6 h in a furnace [Eq. (2)], followed by quenching quenching
Rapid cooling, as by immersion in oil or water, of a metal object from the high temperature at which it is shaped. Quenching is usually done to maintain mechanical properties that would be lost with slow cooling. at room temperature in a desiccator des·ic·cate
v. des·ic·cat·ed, des·ic·cat·ing, des·ic·cates
1. To dry out thoroughly.
2. To preserve (foods) by removing the moisture. See Synonyms at dry.
2[CaHPO.sub.4]+2[CaCO.sub.3][right arrow][Ca.sub.4][([PO.sub.4]).sub.2]O+[H.sub.2]O+2[CO.sub.2] [up arrow] (2)
Because the particle size of the cement ingredients plays an important role in the setting and final properties of the cement, TTCP is ground to a median particle size of approximately 17 [micro]m and commercial reagent grade DCPA is ground to a median particle size of about 1 [micro]m. It is proven essential to grind each solid component individually to the desired particle sizes (1). The two components are then thoroughly mixed and the resulting CPC powder is stored in a desiccator.
The liquid phase can be water, saline or other physiological fluids. A phosphate containing solution is used as the liquid for a shorter hardening time of 5 min (7). For applications requiring longer working times, a non-aqueous but water-miscible liquid such as glycerine glycerine
see glycerin. (8) or polyethylene glycol polyethylene glycol (PEG): see glycol. (9) can be used. Ready-to-use premixed CPC pastes are also prepared with these non-aqueous liquids (10). Because the cement setting reaction does not occur to a significant extent in these liquids, the cement would remain pliable for an indefinite period and harden after being placed in a defect and a sufficient amount of water from the surrounding tissues diffused into the paste. Addition of a jelling agent such as hydroxypropyl methlycellulose, carboxyl carboxyl /car·box·yl/ (kahr-bok´sil) the monovalent radical —COOH, occurring in those organic acids termed carboxylic acids.
n. methylcellulose methylcellulose /meth·yl·cel·lu·lose/ (-sel´ul-os) a methyl ester of cellulose; used as a bulk laxative and as a suspending agent for drugs and applied topically to the conjunctiva to protect and lubricate the cornea during certain , chitosan, etc., to the cement liquid can improve the washout washout
to disperse or empty by flooding with water or other solvent.
medullary solute washout
a syndrome in which the relative hyperosmolarity of the renal medulla is reduced due to an excessive loss of sodium and chloride from resistance of the cement paste before hardening occurs, allowing CPC to harden in standing water (11). Chitosan is also be used to prepare CPC materials that are less brittle and non-rig id (12, 13).
4. Physical and Chemical Properties of CPC
A CPC with a setting time of about 30 min with water and a compressive strength of 34 MPa was developed (5). Powder X-ray diffraction (Rigaku DMAX 2200, Rigaku/USA, MA) and microscopic examinations by scanning electron microscopy (JEOL JEOL Japan Electron Optics Laboratory JSM-5300, JEOL USA Inc., MA) indicated that the HA formed in CPC (Fig. 2) was in the form of very small rod-like crystals ([approximately equal to]0.O5 [micro]m x 0.5 [micro]m) (Fig. 3) that were similar in size to the HA crystallites in human tooth enamel. Continued research conducted by ADAHF-PRC scientists at NIST has resulted in many significant improvements in CPC. These improvements included a much shorter hardening time of 5 min (7) using a phosphate containing solution as the cement liquid, a considerably higher diametral tensile strength and compressive strength of 11.5 MPa and 66 MPa, respectively (14). Additional improvements included increased washout resistance, premixed CPC pastes and non-rigid CPC, as described above (10 to 13).
Solubility is an important property of CPC because it relates to the stability of the material under various application conditions. Fully cured CPC samples prepared from the TTCP + DCPA mixture contain essentially HA with a small amount of residual TTCP (Fig. 2) and have solubility properties similar to those of HA. CPC is nearly insoluble in water but is readily soluble under strong acidic conditions. In vivo, CPC is insoluble under normal physiological conditions because fluids such as saliva and blood are supersaturated with respect to HA. However, CPC dissolves under acidic conditions created by osteoclasts Osteoclasts
Bone cells that break down and remove bone tissue.
Mentioned in: Bone Grafting, Osteoporosis and other acid-producing cells.
5. In Vivo Characteristics of CPC
CPCs contain only calcium phosphates and form apatitic mineral as product upon setting at neutral pH. Consequently, they were found to be highly compatible with both hard and soft tissues. In numerous animal studies (15 to 24), CPCs have proven superior to currently available materials, due to their ability to harden at the application site. Applied as a paste, CPC closely adapts to bone surfaces even when examined at the microscopic level. Direct and close adherence of CPC to bone reduces the formation of intervening tissues at the bone-implant interface, facilitating the processes that lead to replacement of CPC by new bone.
In addition to high biocompatibility and self-hardening, the usefulness of CPC for repairing bone defects arises from its unique in vivo properties: gradual resorption and replacement by new bone formation with no loss in volume. Set CPC consists of tightly packed microcrystalline microcrystalline /mi·cro·crys·tal·line/ (-kris´tah-lin) made up of minute crystals.
made up of minute crystals. HA that has a large surface area. Because HA is formed in an aqueous environment and has a relatively low crystallinity (Fig. 2), it is similar to biological apatite apatite (ăp`ətīt), mineral, a phosphate of calcium containing chlorine or fluorine, or both, that is transparent to opaque in shades of green, brown, yellow, white, red, and purple. . These properties are believed to be responsible for CPC's in vivo resorption characteristics. This is in contrast to the ceramic HA materials, which are non-resorbable (25), or [beta]-tricalcium phosphate, [beta]-[Ca.sub.3][([PO.sub.4]).sub.2], which resorbs but is not always fully replaced by new bone formation (26).
6. Clinical Studies of CPC
The TTCP + DCPA cement, shown to be efficacious in animal studies, was evaluated in several medical centers for cranial defect repair as part of a U.S. FDA approved study in human subjects. From eleven neurotologic procedures completed in 1994, it appeared that the cement had potential to become a commonly used material in the management of cranial base and temporal bone defects following surgery (27). Suboccipital craniectomy cra·ni·ec·to·my
Surgical removal of a portion of the cranium.
craniectomy (krā·nē·ekˑ·t defects resulting from vestibular schwannoma removal were reconstructed by CPC (28). Within 2 years, re-establishment of cranial bone integrity was reported. Cranial base reconstruction with CPCs has been successful for translabyrinthine, middle cranial fossa The middle fossa, deeper than the anterior cranial fossa, is narrow in the middle, and wide at the sides of the skull.
It is bounded in front by the posterior margins of the small wings of the sphenoid, the anterior clinoid processes, and the ridge forming the anterior , and suboccipital craniectomy defects, as well as for extensive temporal bone fractures (29). The stability of the cement has been confirmed by serial radiographic radiographic (rā´dēōgraf´ik),
adj relating to the process of radiography, the finished product, or its use. analyses. Exposure to cerebrospinal fluid did not appear to alter its stability, and pre-existing infection appeared to be the only contraindication contraindication /con·tra·in·di·ca·tion/ (-in?di-ka´shun) any condition which renders a particular line of treatment improper or undesirable.
n. for its use. CPC app eared to be superior to acrylic implants for the reconstruction of full-thickness defects of the frontal sinus and frontofacial region by allowing implant osseointegration with improved biocompatibility (30). Weissman et al. (31) reported successful reconstruction or sealing of defects of the skull base and of facial bones with CPC in 24 patients.
In July 1996, a CPC consisting of TTCP + DCPA was approved by the Food and Drug Administration for repair of cranial defects in humans, thus becoming the first material of its kind available for clinical use. CPC has become a subject of great interest to many scientists and clinicians worldwide, and several additional CPC products are now commercially available. With continuing improvements in cement properties and understanding of material-tissue interactions under various clinical situations, different CPC formulations with properties optimized for specific clinical applications are being developed.
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
This investigation was supported, in part, by USPHS USPHS United States Public Health Service.
United States Public Health Service research Grant DE11789 to the ADAHF from the National Institutes of Dental and Craniofacial craniofacial /cra·nio·fa·cial/ (kra?ne-o-fa´sh'l) pertaining to the cranium and the face.
Of or involving both the cranium and the face. Research and is part of the dental research program conducted by the NIST in cooperation with ADAHF.
Accepted: August 22, 2001
Available online: http://www.nist.gov/jres
(#.) Certain commercial equipment, instruments, or materials arc identified in this paper to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology or the ADAHF, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose.
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(2.) W. E. Brown, and L. C. Chow, A new calcium phosphate, water-setting cement, in Cements Research Progress 1986, P. W. Brown, ed., American Ceramic Society The American Ceramic Society (ACerS) is a non-profit professional organization for the ceramics community, with a focus on scientific research, emerging technologies, and current applications in which ceramic materials are a key element. , Ohio (1987) pp. 352-379.
(3.) L. C. Chow, and S. Takagi, Calcium phosphate cements, in Cements Research Progress 1994, L. J. Struble, ed., American Ceramic Society, Ohio (1996) pp. 189-201.
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(7.) K. Ishikawa, S. Takagi, L. C. Chow, and Y. Ishikawa, Properties and mechanism of fast-setting calcium phosphate cements, J. Mater. Sci. Mater. Med. 6, 528-533 (1995).
(8.) A. Sugawara, L. C. Chow, S. Takagi, and H. Chohayeb, An in vitro evaluation of sealing ability of a calcium phosphate root canal sealer-filler, J. Endodont. 16(4), 162-165 (1990).
(9.) A. Sugawara, M. Nishiyama, L. C. Chow, and S. Takagi, A new biocompatible material: calcium phosphate cement--biomedical applications, Tokyo Shika Ishikai Zashi. 38, 348-354 (1990).
(10.) S. Takagi, A. Sugawara, S. Hirayama, and L. C. Chow, Premixed calcium phosphate cement pastes, Transactions of the Sixth World Biomaterials Congress. (2000) p. 19.
(11.) A. Cherng, S. Takagi, and L. C. Chow, Effects of hydroxypropyl methylcellulose and other gelling agents on the handling properties of calcium phosphate cement. J. Biomed. Mater. Res. 35, 273-277 (1997).
(12.) S. Takagi, L. C. Chow, S. Hirayama, and F. C. Eichmiller, Properties of a non-rigid resorbable calcium phosphate cement, Special Issue, abstract No. 373, J. Dent. Res. 78, 152 (1999).
(13.) H. H. K. Xu, 3. B. Quinn, S. Takagi, and L. C. Chow, Processing and properties of a non-rigid calcium phosphate cement, J. Dent. Res,, in press (2002).
(14.) L. C. Chow, S. Hirayama, S. Takagi, and E. Parry, Diametral tensile strength and compressive strength of a calcium phosphate cement: Effect of applied pressure, J. Biomed. Mater. Res. (Appl. Biomater.) 53, 511-517 (2000).
(15.) P. D. Costantino, C. D. Friedman, K. Jones, L. C. Chow, H. J. Pelzer, and G. A. Sisson, Hydroxyapatite cement. I. Basic chemistry and histologic properties, Arch. Otolaryngol. Head Neck Surg. 117, 379-384 (1991).
(16.) P. D. Costantino, C. D. Friedman, R. Jones, L. C. Chow, and G. A. Sisson, Experimental hydroxyapatite cement cranioplasty. Plast. Reconstr. Surg. 90, 174-191 (1992).
(17.) C. D. Friedman, P. D. Costantino, K. Jones, L. C. Chow, H. J. Pelzer, and G. A. Sisson, Hydroxyapatite cement. II. Obliteration A destruction; an eradication of written words.
Obliteration is a method of revoking a Will or a clause therein. Lines drawn through the signatures of witnesses to a will constitute an obliteration of the will even if the names are still decipherable. and reconstruction of the cat frontal sinus, Arch. Otolaryngol. Head Neck Surg. 117, 385-389 (1991).
(18.) Y C. Hong, J. T. Wang, C. Y. Hong, W. E. Brown, and L. C. Chow, The periapical tissue reaction to a calcium phosphate cement in the teeth of monkeys, J. Biomed. Mater. Res. 25, 485-498 (1991).
(19.) A. Sugawara, M. Nishiyama, K. Kusama, I. Moro, S. Nishimura, I. Kudo ku·do
n. pl. ku·dos
Usage Problem A praising remark; an accolade or compliment: "Children's book author Virginia Hamilton added another kudo to her prize-laden career" , L. C. Chow, and S. Takagi, Histological reactions of calcium phosphate cement, Dent. Mater. J. (Japan) 11, 11-16 (1992).
(20.) A. Sugawara, K. Kusama, S. Nishimura, M. Nishiyama, I. Moro, I. Kudo, S. Takagi, and L. C. Chow, Histopathological reactions to calcium phosphate cement for bone filling, J. Soc. Mater. Devices (Japan) 12, 691-698 (1993).
(21.) A. Sugawara, K. Kusama, S. Nishimura, M. Nishiyama, I. Moro, I. Hudo, L. C. Chow, and S. Takagi, Histopathological reaction of a calcium phosphate cement root canal filler, J. Hard Tissue Biol. 4, 1-7 (1995).
(22.) M. L. Shindo, P. D. Costantino, C. D. Friedman, and L. C. Chow, Facial skeletal augmentation using hydroxyapatite cement, Arch. Otolaryngol. Head Neck Surg. 119, 185-190 (1993).
(23.) K. Fujikawa, A. Sugawara. S. Murai, M. Nishiyama, S, Takagi, and L. C. Chow, Histopathological reaction of calcium phosphate cement in periodontal bone defect, Dent. Mater. J. (Japan). 14, 45-57 (1995).
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(26.) G. Bauer, B. J. Fellows, H. Gottschalk, J. Dumbach, W. J. Spitzer, and K. Donath, Auswirkunge des pH-Werts verschiedener Calciumphosphat Keramiken auf die biologisehe Umgebung, DVM-AK, "Implantate," Bioaktive Werkstoffe 6, 103 (1985).
(27.) D. B. Kamerer, C. D. Friedman, P. D. Costantino, C. H. Snyderman, and B. F. Hirsch, Hydroxyapatite cement: A new method for achieving watertight closure in transtemporal surgery, Am. 3. Otol. 15, 47-49 (1994).
(28.) J. F. Kveton, C. D. Friedman, J. M. Piepmeier, and P. D. Costantino, Reconstruction of suboceipital craniectomy defects with hydroxyapatite cement: A preliminary report, Laryngoscope 105, 156-159 (1995).
(29.) J. F. Kveton, C. D. Friedman, and P D. Costantino, Indications for hydroxyapatite cement reconstruetion in lateral skull base surgery. Am. J. Otol. 16, 465-469 (1995).
(30.) C. D. Friedman, P. D. Costantino, C. H. Snyderman, L. C. Chow, and S. Takagi, Reconstruction of the frontal sinus and frontofacial skeleton with hydroxyapatite cement, Arch. Facial Plast. Surg. 2, 124-129 (2000).
(31.) J. L. Weissman, C. H. Snyderman, and B. F. Hirsch, Hydroxyapatite cement to repair skull base defects: Radiologic appearance, Am. J. Neuroradiol. 17, 1569-1574 (1996).
About the authors: Laurence C. Chow is a physical chemist in the Dental Chemistry Division and Shozo Takagi is a crystallographer crys·tal·log·ra·phy
The science of crystal structure and phenomena.
crystal·log in the Cariology Division, ADAHF PRC, Polymer Division, NIST Materials Science and Engineering Materials science and engineering
A multidisciplinary field concerned with the generation and application of knowledge relating to the composition, structure, and processing of materials to their properties and uses. Laboratory. The National Institute of Standards and Technology is an agency of the Technology Administration, U.S. Department of Commerce.