Drug – bio-affecting and body treating compositions – Dentifrices – Phosphate compound containing
Reexamination Certificate
2000-04-28
2002-04-23
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Dentifrices
Phosphate compound containing
C424S400000, C424S423000, C424S484000, C424S489000, C424S049000
Reexamination Certificate
active
06375935
ABSTRACT:
FIELD OF THE INVENTION
The field of this invention is calcium phosphate cements.
BACKGROUND
Calcium phosphate cements which are prepared by combining a dry component(s) and a liquid to form a flowable paste like material that is subsequently capable of setting into a solid calcium phosphate product hold great promise for use as structural materials in the orthopedic and dental fields. For example, it is desirable to be able to inject a flowable material into a cancellous bone void and have the material set into a solid calcium phosphate mineral product that is capable of withstanding physiological loads. Materials that set into solid calcium phosphate mineral products are of particular interest as such products can closely resemble the mineral phase of natural bone and are susceptible to remodeling, making such products extremely attractive for use in orthopedics and related fields.
While a large number of different calcium phosphate cement formulations have been developed, there is a continued need for the development of yet more advanced formulations. Of particular interest is the development of formulations that set in a clinically relevant period of time into products that have sufficient strength to serve as cancellous and cortical bone substitutes and are capable of being replaced over time with natural bone.
Relevant Literature
Calcium phosphate compositions relevant to this invention include, but are not limited to those described in: “Production and Characterization of New Calcium Phosphate Cements in the CAHPO4-alpha-CA3(PO4)2 System: pH, Workability and Setting Times”; J. Materials Science: Materials in Medicine, v. 10 (1999) pp.223-230. Representative Patents describing calcium phosphate cements include: U.S. Pat. Nos. 6,027,742; 6,005,162; 5,997,624; 5,976,234; 5,968,253; 5,962,028; 5,954,867; 5,900,254; 5,697,981; 5,695,729; 5,679,294; 5,580,623; 5,545,254; 5,525,148; 5,281,265; 4,990,163; 4,497,075; and 4,429,691. Sodium hexafluorosilicate is described in U.S. Pat. Nos.: 4,161,511 and 4,160,012.
SUMMARY OF THE INVENTION
Methods are provided for producing flowable compositions, e.g. injectable pastes, that set into calcium phosphate products. In the subject methods, dry reactants that include a calcium source and a phosphate source are combined with a solution of a soluble silicate, e.g. sodium silicate, and the combined liquids and solids are mixed to produce the flowable composition. Also provided are the compositions themselves as well as kits for preparing the same. The subject methods and compositions produced thereby find use in a variety of applications, including the repair of hard tissue defects, e.g. bone defects.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
Methods are provided for producing flowable compositions, e.g. injectable pastes, that set into calcium phosphate products. In the subject methods, dry reactants that include a calcium source and a phosphate source are combined with a solution of a soluble silicate, e.g. sodium silicate, and the combined liquids and solids are mixed to produce the flowable composition. Also provided are the compositions themselves as well as kits for preparing the same. The subject methods and compositions produced thereby find use in a variety of applications, including the repair of hard tissue defects, e.g. bone defects. In further describing the subject invention, the subject methods will be described first, followed by a description of the compositions produced thereby, kits for use in preparing the same and methods for using the subject compositions in methods of hard tissue, e.g. bone repair.
Before the subject invention is further described, it is to be understood that the invention is not limited to the particular embodiments of the invention described below, as variations of the particular embodiments may be made and still fall within the scope of the appended claims. It is also to be understood that the terminology employed is for the purpose of describing particular embodiments, and is not intended to be limiting. Instead, the scope of the present invention will be established by the appended claims.
In this specification and the appended claims, the singular forms “a,” “an” and “the” include plural reference unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs.
M
ETHODS
In the subject methods, dry reactants that include a calcium source and a phosphate source are combined with a solution of a soluble silicate under conditions sufficient to produce a flowable composition that sets into a calcium phosphate containing product, even when immersed.
A feature of the subject methods is that a solution of a soluble silicate is employed. By solution of a soluble silicate is meant an aqueous solution in which a silicate compound is dissolved and/or suspended. The silicate compound may be any compound that is physiologically compatible and is soluble in water. By soluble in water is meant a concentration of at least about 1%, usually at least about 2% and more usually at least about 5%, where the concentration of the silicate employed typically ranges from about 0 to 20%, usually from about 5 to 15% and more usually from about 5 to 10%. Representative silicates of interest include, but are not limited to: sodium silicates, potassium silicates, borosilicates, magnesium silicates, aluminum silicates, zirconium silicates, potassium aluminum silicates, magnesium aluminum silicates, sodium aluminum silicates, sodium methylsilicates, potassium methylsilicates, sodium butylsilicates, sodium propylsilicates, lithium propylsilicates, triethanol ammonium silicates, tetramethanolamine silicates, zinc hexafluorosilicate, ammonium hexafluorosilicate, cobalt hexafluorosilicate, iron hexafluorosilicate, potassium hexafluorosilicate, nickel hexafluorosilicate, barium hexafluorosilicate, hydroxyammonium hexafluorosilicate, sodium hexafluorosilicate and calcium fluorosilicate. The preparation of sodium hexafluorosilicate is described in U.S. Pat. Nos. 4,161,511 and 4,160,012; the disclosures of which are herein incorporated by reference. Of particular interest in many embodiments are solutions of sodium silicate, where the manufacture of dry sodium silicate (Na2SiO3, Na6 Si2O7 and Na2Si3O7) is described in Faith, Keyes & Clark's I
NDUSTRIAL
C
HEMICALS
(1975) pp 755-761.
In the subject methods, the above described soluble silicate solutions are combined with dry reactants that include a calcium source and a phosphate source under conditions sufficient to produce a flowable composition. The dry reactants that are combined with the solution are typically particulate compositions, e.g. powders, where the particle size of the components of the particulate compositions typically ranges from about 1 to 1000 microns, usually from about 1 to 200 um and more usually from about 1 to 40 microns.
As mentioned above, the dry reactants include a calcium source and a phosphate source. The calcium source and phosphate source may be present as a single compound or present as two or more compounds. As such, a single calcium phosphate present in the dry reactants may be the calcium source and the phosphate source. Alternatively, two or more compounds may be present in the dry reactants, where the compounds may be compounds that include calcium, phosphate or calcium and phosphate. Calcium phosphate sources of interest that may be present in the dry reactants include: MCPM (monocalcium phosphate monohydrate or Ca(H
2
PO
4
)
2
.H
2
O); DCPD (dicalcium phosphate dihydrate, brushite or CaHPO
4
.2H
2
O), ACP (amorphous calcium phosphate or Ca
3
(PO
4
)
2
H
2
O), DCP (dicalcium phosphate, monetite or CaHPO
4
), tricalcium phosphate, including both &agr;- and &bgr;-(Ca
3
(PO
4
)
2
, tetracalcium phosphate (Ca
4
(PO
4
)
2
O, etc. Calcium sources of interest include: calcium carbonate (CaCO
3
), calcium oxide (CaO), calcium hydroxide (Ca(OH)2 and the like. Phosphate sources of int
Bozicevic, Field & Francis
Evans Charesse L.
Field Bret E.
Page Thurman K.
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