U.S. patent application number 14/075230 was filed with the patent office on 2014-05-15 for block copolymers for tooth enamel protection.
The applicant listed for this patent is Colgate-Palmolive Company, Howard University. Invention is credited to Mahmoud Hassan, Yanda Lei, James W. Mitchell, Jianhong Qiu, Tongxin Wang, Lynette Zaidel.
Application Number | 20140134116 14/075230 |
Document ID | / |
Family ID | 49622915 |
Filed Date | 2014-05-15 |
United States Patent
Application |
20140134116 |
Kind Code |
A1 |
Wang; Tongxin ; et
al. |
May 15, 2014 |
Block Copolymers For Tooth Enamel Protection
Abstract
Described herein are block copolymers having hydrophobic blocks
and hydrophilic blocks which are effective in binding to the
surface of hard tissue; compositions comprising the same, as well
as methods of making and using the same are also described.
Inventors: |
Wang; Tongxin; (Berwyn
Heights, MD) ; Lei; Yanda; (Greenbelt, MD) ;
Mitchell; James W.; (Durham, NC) ; Zaidel;
Lynette; (Cranford, NJ) ; Qiu; Jianhong;
(Green Brook, NJ) ; Hassan; Mahmoud; (Somerset,
NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Colgate-Palmolive Company
Howard University |
Piscataway
Washington |
NJ
DC |
US
US |
|
|
Family ID: |
49622915 |
Appl. No.: |
14/075230 |
Filed: |
November 8, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61724736 |
Nov 9, 2012 |
|
|
|
61780199 |
Mar 13, 2013 |
|
|
|
Current U.S.
Class: |
424/57 ; 424/49;
525/287; 525/299 |
Current CPC
Class: |
A61K 8/21 20130101; C08F
293/005 20130101; A61K 8/90 20130101; A61Q 11/00 20130101 |
Class at
Publication: |
424/57 ; 424/49;
525/287; 525/299 |
International
Class: |
A61K 8/90 20060101
A61K008/90; A61Q 11/00 20060101 A61Q011/00 |
Claims
1. A block copolymer having at least one hydrophobic block and at
least one hydrophilic block which are effective to bind to
hydroxyapatite.
2. The block copolymer of claim 1, wherein the block copolymer is
effective to protect the hydroxyapatite from loss of calcium by at
least about 10 percent after exposure of the hydroxyapatite to the
copolymer and subsequent exposure of the copolymer coated
hydroxyapatite to citric acid.
3. The block copolymer of claim 1, wherein the hydrophilic block is
selected from the group consisting of phosphonated block,
phosphorylated block, carboxylated block, sulfate substituted
block, amino substituted block, hydroxyl substitued block and
mixtures thereof.
4. The block copolymer of claim 2, wherein the hydrophilic block is
selected from the group consisting of phosphonated block,
phosphorylated block, carboxylated block, sulfate substituted
block, amino substituted block, hydroxyl substitued block and
mixtures thereof.
5. The block copolymer of claim 4, wherein the block copolymer has
a molecular weight in the range of from about 1,000 to about
1,000,000, individual hydrophilic blocks having a molecular weight
in the range of from about 200 to about 1,000,000, and individual
hydrophobic blocks having a molecular weight in the range of from
about 200 to about 1,000,000.
6. The block copolymer of claim 4, wherein the hydrophilic blocks
comprise from about 10 to about 90 weight percent of the block
copolymer and the hydrophobic blocks comprise from about 10 to
about 90 weight percent of the block copolymer.
7. The block copolymer of claim 4, wherein the block has a
molecular weight and the polymers have a total molecular weight
effective to provide a solubility in water of from about 0.001 to
about 100 g/l.
8. The block copolymer of claim 4, wherein the block copolymer is
selected from the group consisting of a diblock copolymer, a
triblock copolymer and a multi-armed copolymer.
9. The block copolymer of claim 4, wherein the block copolymer has
a molecular weight in a range of 1,000 to 1,000,000.
10. The block copolymer of claim 6, wherein the block copolymer has
a molecular weight in a range of 1,000 to 10,000.
11. The block copolymer of claim 8, wherein the block copolymer has
a molecular weight in a range of 1,000 to 10,000.
12. The block copolymer of claim 2, wherein the block copolymer has
the structure of formula I or formula II: ##STR00013## where A is
selected from the group consisting of (CH.sub.2).sub.p,
(CH.sub.2CH.sub.2O).sub.q, (phenyl), (C(.dbd.O)--O).sub.y, or any
combination thereof, where for substituent A p, q=0, 1, 2, 3 . . .
20; x=0, 1, y=0 or 1; R.sub.1 is selected from the group consisting
of H.sub.a, (CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.1
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1; R.sub.2 is
selected from the group consisting of H.sub.a, (CH.sub.2).sub.p,
(CH.sub.2CH.sub.2O).sub.q, (phenyl), (C(.dbd.O)--O).sub.y, or any
combination thereof, where for R.sub.2 p, q=0, 1, 2, 3 . . . 20;
x=0, 1, y=0, 1, a=0, 1; R.sub.3 is selected from the group
consisting of H.sub.a, (CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q,
(phenyl), (C(.dbd.O)--O).sub.y, or any combination thereof, where
for R.sub.3 p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
R.sub.4 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.4
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1; R.sub.5 is
selected from the group consisting of H.sub.a, (CH.sub.2).sub.p,
(CH.sub.2CH.sub.2O).sub.q, (phenyl), (C(.dbd.O)--O).sub.y, or any
combination thereof, where for R.sub.5 p, q=0, 1, 2, 3 . . . 20;
x=0, 1, y=0, 1, a=0, 1; R.sub.6 is selected from the group
consisting of H.sub.a, (CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q,
(phenyl), (C(.dbd.O)--O).sub.y, or any combination thereof, where
for R.sub.6 p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
R.sub.7 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.7
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1; R.sub.8 is
selected from the group consisting of an alkali metal, an ammonium,
protonated alkyl amine, H.sub.a, (CH.sub.2).sub.p,
(CH.sub.2CH.sub.2O).sub.q, (phenyl), (C(.dbd.O)--O).sub.y, or any
combination thereof, where for R.sub.8 p, q=0, 1, 2, 3 . . . 20;
x=0, 1, y=0, 1, a=0, 1; R.sub.9 is selected from the group
consisting of an alkali metal, an ammonium, protonated alkyl amine,
H.sub.a, (CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.9
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1; R.sub.10 is
hydrogen, alkali metal or ammonium; and m and n are each
independently in a range from about 5 to about 3000.
13. The block copolymer of claim 12, wherein the block copolymer
has a molecular weight in the range of from about 1,000 to about
1,000,000, individual hydrophilic blocks having a molecular weight
in the range of from about 200 to about 1,000,000, and individual
hydrophobic blocks having a molecular weight in the range of from
about 200 to about 1,000,000.
14. The block copolymer of claim 12, wherein the hydrophilic blocks
comprise from about 10 to about 90 weight percent of the block
copolymer and the hydrophobic blocks comprise from about 10 to
about 90 weight percent of the block copolymer.
15. An oral hygienic composition comprising: an orally acceptable
carrier; and a block copolymer having at least one hydrophobic
block and at least one hydrophilic block which are effective to
bind to hydroxyapatite and the block copolymer is effective to
protect the hydroxyapatite from loss of calcium by at least about
10 percent after exposure of the hydroxyapatite to the copolymer
and subsequent exposure of the copolymer coated hydroxyapatite to
citric acid.
16. The oral hygienic composition of claim 15, wherein the block
copolymer has the structure of formula I or formula II:
##STR00014## where A is selected from the group consisting of
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for
substituent A p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0 or 1; R.sub.1
is selected from the group consisting of H.sub.a, (CH.sub.2).sub.p,
(CH.sub.2CH.sub.2O).sub.q, (phenyl), (C(.dbd.O)--O).sub.y, or any
combination thereof, where for R.sub.1 p, q=0, 1, 2, 3 . . . 20;
x=0, 1, y=0, 1, a=0, 1; R.sub.2 is selected from the group
consisting of H.sub.a, (CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q,
(phenyl), (C(.dbd.O)--O).sub.y, or any combination thereof, where
for R.sub.2 p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
R.sub.3 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.3
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1; R.sub.4 is
selected from the group consisting of H.sub.a, (CH.sub.2).sub.p,
(CH.sub.2CH.sub.2O).sub.q, (phenyl), (C(.dbd.O)--O).sub.y, or any
combination thereof, where for R.sub.4 p, q=0, 1, 2, 3 . . . 20;
x=0, 1, y=0, 1, a=0, 1; R.sub.5 is selected from the group
consisting of H.sub.a, (CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q,
(phenyl), (C(.dbd.O)--O).sub.y, or any combination thereof, where
for R.sub.5 p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
R.sub.6 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.6
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1; R.sub.7 is
selected from the group consisting of H.sub.a, (CH.sub.2).sub.p,
(CH.sub.2CH.sub.2O).sub.q, (phenyl), (C(.dbd.O)--O).sub.y, or any
combination thereof, where for R.sub.7 p, q=0, 1, 2, 3 . . . 20;
x=0, 1, y=0, 1, a=0, 1; R.sub.8 is selected from the group
consisting of an alkali metal, an ammonium, protonated alkyl amine,
H.sub.a, (CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.8
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1; R.sub.9 is
selected from the group consisting of an alkali metal, an ammonium,
protonated alkyl amine, H.sub.a, (CH.sub.2).sub.p,
(CH.sub.2CH.sub.2O).sub.q, (phenyl), (C(.dbd.O)--O).sub.y, or any
combination thereof, where for R.sub.9 p, q=0, 1, 2, 3 . . . 20;
x=0, 1, y=0, 1, a=0, 1; R.sub.10 is hydrogen, alkali metal or
ammonium; and m and n are each independently in a range from about
5 to about 3000.
17. A method for protecting tooth enamel from acid erosion, the
method comprising: applying a block copolymer to tooth enamel, the
block copolymer having at least one hydrophobic block and at least
one hydrophilic block which are effective to bind to
hydroxyapatite.
18. The method of claim 17, wherein the block copolymer is
effective to protect the hydroxyapatite from loss of calcium by at
least about 10 percent after exposure of the hydroxyapatite to the
copolymer and subsequent exposure of the copolymer coated
hydroxyapatite to citric acid.
19. The method of claim 18, wherein the block copolymer has a
molecular weight in a range of from about 1,000 to have
1,000,000.
20. The method of claim 18, wherein the block copolymer has a
molecular weight in the range of from about 1,000 to about
1,000,000, individual hydrophilic blocks having a molecular weight
in the range of from about 200 to about 1,000,000, and individual
hydrophobic blocks having a molecular weight in the range of from
about 200 to about 1,000,000.
21. The method of claim 20, wherein the hydrophilic blocks comprise
from about 10 to about 90 weight percent of the block copolymer and
the hydrophobic blocks comprise from about 10 to about 90 weight
percent of the block copolymer.
22. The method of claim 18, wherein the block copolymer has the
structure of formula I or formula II: ##STR00015## where A is
selected from the group consisting of (CH.sub.2).sub.p,
(CH.sub.2CH.sub.2O).sub.q, (phenyl), (C(.dbd.O)--O).sub.y, or any
combination thereof, where for substituent A p, q=0, 1, 2, 3 . . .
20; x=0, 1, y=0 or 1; R.sub.1 is selected from the group consisting
of H.sub.a, (CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.1
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1; R.sub.2 is
selected from the group consisting of H.sub.a, (CH.sub.2).sub.p,
(CH.sub.2CH.sub.2O).sub.q, (phenyl), (C(.dbd.O)--O).sub.y, or any
combination thereof, where for R.sub.2 p, q=0, 1, 2, 3 . . . 20;
x=0, 1, y=0, 1, a=0, 1; R.sub.3 is selected from the group
consisting of H.sub.a, (CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q,
(phenyl), (C(.dbd.O)--O).sub.y, or any combination thereof, where
for R.sub.3 p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
R.sub.4 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.4
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1; R.sub.5 is
selected from the group consisting of H.sub.a, (CH.sub.2).sub.p,
(CH.sub.2CH.sub.2O).sub.q, (phenyl), (C(.dbd.O)--O).sub.y, or any
combination thereof, where for R.sub.5 p, q=0, 1, 2, 3 . . . 20;
x=0, 1, y=0, 1, a=0, 1; R.sub.6 is selected from the group
consisting of H.sub.a, (CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q,
(phenyl), (C(.dbd.O)--O).sub.y, or any combination thereof, where
for R.sub.6 p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
R.sub.7 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.7
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1; R.sub.8 is
selected from the group consisting of an alkali metal, an ammonium,
protonated alkyl amine, H.sub.a, (CH.sub.2).sub.p,
(CH.sub.2CH.sub.2O).sub.q, (phenyl), (C(.dbd.O)--O).sub.y, or any
combination thereof, where for R.sub.8 p, q=0, 1, 2, 3 . . . 20;
x=0, 1, y=0, 1, a=0, 1; R.sub.9 is selected from the group
consisting of an alkali metal, an ammonium, protonated alkyl amine,
H.sub.a, (CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.9
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1; R.sub.10 is
hydrogen, alkali metal or ammonium; and m and n are each
independently in a range from about 5 to about 3000.
23. The block copolymer of claim 2, wherein the hydrophobic block
comprises a monomer selected from the group consisting of alkyl
acrylate, styrene, olefin, a vinyl monomer, a fluoro monomer,
acrylonitrile, and a combination of two or more thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 61/724,736, filed on Nov. 9, 2012, and U.S.
Provisional Application Ser. No. 61/780,199, filed on Mar. 13,
2013, which both applications are incorporated by reference as if
fully rewritten herein.
BACKGROUND
[0002] There is a need for oral care products offering superior
protection against acid dissolution of tooth enamel that surpasses
traditional fluoride approaches as awareness of erosion and the
impact of dietary habits increases among dental practitioners and
their patients. Extrinsic and intrinsic acid are the two most
important factors governing demineralization, in which the former
is prevalent because of the strikingly increased consumption of
soft drinks. A. Wiegand et al., "Review on fluoride-releasing
restorative materials--fluoride release and uptake characteristics,
antibacterial activity and influence on caries formation,"Dental
Materials, 2007, 23(3): 343-62. An interesting experiment that used
soft drinks to etch tooth enamel indicated that the loss rate of
enamel in a soft drink was as high as 3 mm per year. R. H. Selwitz
et al., "Dental caries," The Lancet, 2007, 369(9555): 51-9. For
example, Coca Cola could reduce the hardness of enamel by 63% of
the original enamel hardness after only 100 seconds of erosion. S.
Wongkhantee et al., "Effect of acidic food and drinks on surface
hardness of enamel, dentine, and tooth-colored filling materials,"
Journal of Dentistry, 2006, 34: 214-220. Dietary acids such as
citric acid are particularly damaging to tooth enamel because these
acids not only have an acid pH, but they also have a calcium
chelating capacity which enhances enamel dissolution. Hence, it is
important to have new protective agents that are readily applied,
are biologically suitable, and can coat tooth enamel and protect
enamel from erosion and attack by foods such as dietary acids.
[0003] Currently, fluoride compounds are widely used to prevent
caries formation and have also been identified as minerals that
protect against acid erosion if formulated under the right
conditions. A. Wiegand et al., "Review on fluoride-releasing
restorative materials--fluoride release and uptake characteristics,
antibacterial activity and influence on caries formation," Dental
Materials, 2007, 23(3): 343-62. R. H. Selwitz et al., "Dental
caries," The Lancet, 2007, 369(9555): 51-9. C. Hjortsjo et al. "The
Effects of Acidic Fluoride Solutions on Early Enamel Erosion in
vivo", Caries Research, 2008, 43: 126-131. But high loading of
fluoride may induce dental fluorosis. WHO, "Fluorides and Oral
Health: Report of A WHO Expert Committee On Oral Health Status and
Fluoride Use," WHO Technical Report Series 846 Geneva, Switzerland,
World Health Organization, 1994. A. K. Mascarenhas, "Risk factors
for dental fluorosis: A review of the recent literature," Pediatric
Dentistry 2000, 22(4): 269-277. Nonfluoride functional agents have
also been highlighted to deliver antierosion benefits. Ganss et al.
"Efficacy of the stannous ion and a biopolymer in toothpastes on
enamel erosion/abrasion" J. of Dentistry, 2012, 40: 1036-1043.
There are many publications that also highlight remineralization
processes. Nano hydroxyapatite has been employed for
remineralization of tooth enamel. L. Li et al., "Bio-Inspired
Enamel Repair via Glu-Directed Assembly of Apatite Nanoparticles:
an Approach to Biomaterials with Optimal Characteristics," Advanced
Materials, 2011, 23(40): 4695-4701. L. Li et al., "Repair of enamel
by using hydroxyapatite nanoparticles as the building blocks,"
Journal of Materials Chemistry, 2008, 18: 4079-4084. Y. Cai et al.,
"Role of hydroxyapatite nanoparticle size in bone cell
proliferation," Journal of Materials Chemistry, 2007, 17:
3780-3787. P. Tschoppe et al., "Enamel and dentine remineralization
by nano-hydroxyapatite toothpastes," Journal of Dentistry, 2011,
39(6): 430-7. But the efficiency of enhancing remineralization is
highly dependent on the nanostructure of apatite and varies a lot
from case to case.
[0004] Casein phosphopeptides-armohous calcium phosphate (CPP-ACP)
complexes are known to bind to tooth enamel and provide a way for
remineralization of the enamel. Srinivasan et al. "Comparison of
the remineralization potential of CPP-ACP and CPP-ACP with 900 ppm
fluoride on eroded human enamel: An in situ study", Archives of
Oral Biology, 2010, 57: 541-544. E. C. Reynolds. "Remineralization
of enamel subsurface lesions by casein phosphopeptide-stabilized
calcium phosphate solutions," Journal of Dental Research, 1997, 76:
1587-1595. M. Panich et al. "The effect of casein
phosphopeptide-amorphous calcium phosphate and a cola soft drink on
in vitro enamel hardness," Journal of American Dental Association,
2009, 140; 455-460." However, CPP and other dairy products may have
potential health risks such as allergic reactions, ranging from
minor swelling of the mouth to serious anaphylaxis, which can be
potentially life threatening. G. H. Docena et al., "Identification
of casein as the major allergenic and antigenic protein of cow's
milk," Allergy, 1996, 51(6): 412-416. B. Schouten et al., "Acute
allergic skin reactions and intestinal contractility changes in
mice orally sensitized against casein or whey," International
Archives of Allergy and Immunology, 2008, 147(2): 125-134. In view
of the latter problems, alternate materials are needed which will
not only provide effective protection of tooth enamel, but also are
non-toxic, biologically suitable and provide a readily usable
synthesis to provide materials which may be effectively used for
enamel protection.
SUMMARY
[0005] Block amphiphilic copolymers having hydrophobic blocks and
hydrophilic phosphonated or phosphorylated or carboxylated blocks
have been developed where the copolymers are effective to bind to
hard tissue which includes hydroxyapatite (HA) and enamel. These
copolymers bind to and protect the hard tissue from acid erosion.
The hydrophilic phosphonated or phosphorylated or carboxylated
blocks are effective to bind to the hard tissue and the hydrophobic
blocks are effective to protect the hard tissue from loss of
calcium by at least 5 percent after exposure of the hydroxyapatite
to the polymers for 0.1-10 minutes and subsequent exposure of the
polymer coated hydroxyapatite to a 0.3-1% citric acid solution,
such as for 15 minutes at 37.degree. C. as compared to
hydroxyapatite which is not bound to the block copolymers. It
should be noted that other temperatures and time periods may also
be used to illustrate the effect of the composition. In some
embodiments, hydrophilic phosphonated or phosphorylated or
carboxylated block copolymers are effective to protect the hard
tissue from loss of calcium by at least 10 percent. In some
embodiments, hydrophilic phosphonated or phosphorylated or
carboxylated block copolymers are effective to protect the hard
tissue from loss of calcium by at least 15 percent. In some
embodiments, hydrophilic phosphonated or phosphorylated or
carboxylated block copolymers are effective to protect the hard
tissue from loss of calcium by at least 20 percent. In some
embodiments, hydrophilic phosphonated or phosphorylated or
carboxylated block copolymers are effective to protect the hard
tissue from loss of calcium by at least 25 percent. In some
embodiments, hydrophilic phosphonated or phosphorylated or
carboxylated block copolymers are effective to protect the hard
tissue from loss of calcium by about 30 percent. In some
embodiments, hydrophilic phosphonated or phosphorylated or
carboxylated block copolymers are effective to protect the hard
tissue from loss of calcium by at least 30 percent.
[0006] In one form, the block copolymers have a molecular weight
(Mn) in a range of from about 1,000 to 1,000,000. According to one
form, the block copolymers have a molecular weight in a range of
1,000 to 10,000. The hydrophilic blocks may include blocks with
pending functional groups such as phosphonic, phosphoryl, carboxyl,
sulfonic, amino, hydroxyl groups, or other hydrophilic groups. In
an important aspect, the phosphonated or phosphorylated or
carboxylated blocks have a molecular weight in a range of from
about 200 to about 1,000,000. According to one form, the
hydrophobic blocks have a molecular weight in a range of from about
200 to about 1,000,000. The phosphonated or phosphorylated or
carboxylated blocks generally comprise from about 10 to about 90
weight percent of the copolymers and the hydrophobic blocks
comprise from about 10 to about 90 weight percent of the block
copolymers. In any event, the block copolymers are dispersible in
an aqueous media and effect protection of tooth enamel from acid
erosion. The polymers may be polymers having two blocks (bi-block
copolymers), three blocks (tri-block polymers) where there are two
blocks which may be hydrophobic and one hydrophilic block or two
hydrophilic blocks and one hydrophobic block and multi-armed
blocks. Arms extend from a common core and the arms may have one or
more blocks.
[0007] In one aspect, the polymers have molecular weights of from
about 1,000 to about 1,000,000 and hydrophobic and hydrophilic
blocks have molecular weights of from about 1,000 to about
1,000,000 which provide a good solubility in water in a range of
from about 0.001 to about 100 g/l at 25.degree. C.
[0008] In another aspect, compositions which are effective for use
in connection with dental hygiene, such as toothpaste, mouthwash,
strips, and gel containing trays which include the block copolymers
described herein, are effective for reconstituting protection of
tooth enamel from acid erosion as described herein. Regular
applications of the compositions, which include the block
copolymers, are effective for providing a protective layer on tooth
enamel at a first time of application, and thereafter. Regular use
of the compositions, as by brushing teeth or use of mouthwash,
gels, or strips provide a way of regularly applying the copolymers
for protection against acid erosion of tooth enamel.
[0009] In an important aspect the phosphonated or phosphorylated
block copolymers have the general formula:
##STR00001##
[0010] In another aspect, the carboxylated copolymers have the
general formula:
##STR00002##
[0011] Where in the above formulas I and II A is selected from the
group consisting of (CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q,
(phenyl), (C(.dbd.O)--O).sub.y, or any combination thereof, where
for substituent A p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0 or 1;
[0012] R.sub.1 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.1
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0013] R.sub.2 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.2
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0014] R.sub.3 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.3
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0015] R.sub.4 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.4
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0016] R.sub.5 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.5
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0017] R.sub.6 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.6
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0018] R.sub.7 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.7
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0019] R.sub.8 is selected from the group consisting of an alkali
metal, an ammonium, protonated alkyl amine, H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.8
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0020] R.sub.9 is selected from the group consisting of an alkali
metal, an ammonium, protonated alkyl amine, H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.9
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0021] R.sub.10 is hydrogen, alkali metal, or ammonium;
[0022] m and n are each independently in a range from about 5 to
about 3000.
[0023] The block copolymers can be synthesized from reversible
addition fragmentation chain transfer radical polymerization
(RAFT), atomic transfer radical polymerization (ATRP) which often
use a catalyst such as a transition metal catalyst and which can
effect multi-armed blocks, other chain transfer polymerization,
free radical polymerization, ionic polymerization or direct
coupling from homopolymers.
[0024] Initiators include, but are not limited to, benzoyl
peroxide, dicumyl peroxide, t-butyl peroxybenzoate,
2,2-azobisisobutyronitrile (AIBN) and other materials that can
generate radicals in direct or indirect approaches. The initiators
for ATRP can be 2-bromoisobutyryl bromide or others with similar
structure.
[0025] The general chemical formula for the chain transfer agent
(CTA) for RAFT polymerizations is shown below:
##STR00003##
[0026] where Z and R can be the same or different substitutes.
Typical chain transfer agents include, but are not limited to,
cumyldithiobenzoate, 2-cyano-2-yl-dithiobenzoate and
4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid
with their structure shown as below.
##STR00004##
[0027] In an important aspect the copolymers are the reaction
product of hydrophobic monomers such as acrylates (alkyl
(meth)acrylate, alkyl acrylate), styrene, olefins (ethylene,
propylene, butylenes, butadiene), vinyl monomers (vinyl acetate,
vinyl ether), fluoro monomers (perfluorocarbon,
tetrafluoroethylene), acrylonitrile, which will provide the
hydrophobic block after polymerization and other hydrophilic
monomers to provide the hydrophilic block. The hydrophilic monomers
contain polymerizable groups and active phosphate acid, phosphonic
acid and related esters, as well as other phosphorous containing
monomers, such as alkyl (meth)acryloyloxyethyl phosphate,
bis(2-methacryloxyethyl) phosphate, vinyl phosphonic acid and other
monomers.
[0028] In another aspect, the block copolymers comprise from about
0.001 to about 50 weight percent of a dental hygienic composition
such as an ingredient which forms the basis of toothpaste or gel
which also includes abrasive particulates such as aluminum
hydroxide, calcium carbonate, dicalcium phosphate, and silicas;
flavorants, humectants, antibacterial agents, and remineralizers
such as fluoride, hydroxyapatite and phosphates such as calcium
phosphate. The block copolymers also may be included in aqueous
compositions which form the basis of mouthwash which also include
fluoride, alcohol, chlorhexidine gluconate, cetylpyridinium
chloride, hexetidine, buffers such as benzoic acid, methyl
salicylate, benzalkonium chloride, methylparaben, hydrogen
peroxide, domiphen bromide and fluoride, enzymes, and calcium.
Mouthwash can also include other antibacterials such as, e.g.,
phenol, thymol, eugenol, eucalyptol or menthol as well as
sweeteners such as sorbitol, sucralose, sodium saccharin, and
xylitol. In this aspect the copolymers are dispersible in an
aqueous media and the block copolymers form from about 0.001 to
about 20 weight percent of the aqueous composition which forms the
mouthwash.
[0029] In yet another aspect, the phosphonated or phosphorylated
block copolymers are formed in a two-step reversible
addition-fragmentation transfer (RAFT) polymerization or a one pot
RAFT polymerization reaction. Illustrative of the two step RAFT
reaction is shown below.
Monomer-1 (hydrophobic monomer)+Chain Transfer Agent (CTA)+Free
Radical Initiator.fwdarw.Poly(monomer-1)-Chain Transfer RAFT
agent
then
Poly(monomer-1)-Chain Transfer RAFT agent+Monomer-2 (phosphorous
monomer)+Free Radical Initiator.fwdarw.
##STR00005##
[0030] In another aspect, the carboxylated block copolymers are
also formed in a two-step RAFT polymerization or a one pot RAFT
polymerization reaction. Illustrative of the two step RAFT reaction
is shown below.
Monomer-1 (hydrophobic monomer)+CTA+Free Radical
Initiator.fwdarw.Poly(monomer-1)-Chain Transfer RAFT agent
then
Poly(monomer-1)-Chain Transfer RAFT agent+Monomer-2 (carboxylated
monomer)+Free Radical Initiator.fwdarw.
##STR00006##
[0031] where A is selected from the group consisting of
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for
substituent A p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0 or 1;
[0032] R.sub.1 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.1
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0033] R.sub.2 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.2
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0034] R.sub.3 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.3
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0035] R.sub.4 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.4
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0036] R.sub.5 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.5
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0037] R.sub.6 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.6
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0038] R.sub.7 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.7
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0039] R.sub.8 is selected from the group consisting of an alkali
metal, an ammonium, protonated alkyl amine, H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.8
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0040] R.sub.9 is selected from the group consisting of an alkali
metal, an ammonium, protonated alkyl amine, H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.9
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0041] R.sub.10 is hydrogen, alkali metal, or ammonium; and
[0042] m and n are each independently in a range from about 5 to
about 3000.
[0043] The block copolymers can be synthesized from reversible
addition fragmentation chain transfer radical polymerization
(RAFT), atomic transfer radical polymerization (ATRP), other chain
transfer polymerization, free radical polymerization, ionic
polymerization or direct coupling from homopolymers.
[0044] Initiators include, but are not limited to, benzoyl
peroxide, dicumyl peroxide, t-butyl peroxybenzoate,
2,2-azobisisobutyronitrile (AIBN) and other materials that can
generate radicals in direct or indirect approaches. The initiators
for ATRP can be 2-bromoisobutyryl bromide or others with similar
structure. The general chemical formula for the chain transfer
agent for RAFT is shown below:
##STR00007##
[0045] where Z and R can be the same or different substitutes.
[0046] In the "one pot" method, the reaction for phosphonated or
phosphorylated block copolymer proceeds as follows as part of a
single step with the phosphorous acid being added to the reaction
mixture having the hydrophobic block:
Monomer-1 (hydrophobic monomer)+Chain Transfer Agent+Free Radical
Initiator.fwdarw.Poly(monomer-1)-Chain Transfer RAFT
agent+Monomer-2 (phosphorous monomer).fwdarw.
##STR00008##
[0047] or, in another aspect, the reaction for carboxylated block
copolymer proceeds as follows as part of a single step with the
carboxylated monomer being added to the reaction mixture having the
hydrophobic block:
Monomer-1 (hydrophobic monomer)+Chain Transfer Agent+Free Radical
Initiator.fwdarw.Poly(monomer-1)-Chain Transfer RAFT
agent+Monomer-2 (phosphorous monomer).fwdarw.
##STR00009##
[0048] where A is selected from the group consisting of
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for
substituent A p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0 or 1;
[0049] R.sub.1 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.1
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0050] R.sub.2 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.2
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0051] R.sub.3 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.3
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0052] R.sub.4 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.4
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0053] R.sub.5 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.5
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0054] R.sub.6 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.6
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0055] R.sub.7 is selected from the group consisting of H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.7
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0056] R.sub.8 is selected from the group consisting of an alkali
metal, an ammonium, protonated alkyl amine, H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.8
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0057] R.sub.9 is selected from the group consisting of an alkali
metal, an ammonium, protonated alkyl amine, H.sub.a,
(CH.sub.2).sub.p, (CH.sub.2CH.sub.2O).sub.q, (phenyl),
(C(.dbd.O)--O).sub.y, or any combination thereof, where for R.sub.9
p, q=0, 1, 2, 3 . . . 20; x=0, 1, y=0, 1, a=0, 1;
[0058] R.sub.10 can be hydrogen, an alkali metal, or an ammonium;
and
[0059] m and n are each independently in a range from about 5 to
about 3000.
[0060] The block copolymers can be synthesized from reversible
addition fragmentation chain transfer radical polymerization
(RAFT), atomic transfer radical polymerization (ATRP), other chain
transfer polymerization, free radical polymerization, ionic
polymerization or direct coupling from homopolymers.
[0061] Initiators include, but are not limited to, benzoyl
peroxide, dicumyl peroxide, t-butyl peroxybenzoate,
2,2-azobisisobutyronitrile (AIBN) and other materials that can
generate radicals in direct or indirect approaches. The initiators
for ATRP can be 2-bromoisobutyryl bromide or others with similar
structure. The general chemical formula for the chain transfer
agent for RAFT is shown below:
##STR00010##
[0062] where Z and R can be the same or different substitutes.
[0063] In the third aspect, the amphiphilic copolymers are prepared
by using a free radical polymerization without RAFT chain transfer
agent or by using an atom transfer radical polymerization (ATRP)
either from `one-pot` polymerization or `two step` polymerization
as that for RAFT.
[0064] The water solubility and/or dispersibility of the block
copolymers may be controlled by the molecular weight of the
hydrophilic portion of the copolymer and the ratios of the two
blocks. This is done for example by having a feeding ratio and
polymerization time of the phosphorous monomer such that a
dispersibility or solubility of the block copolymer is from about
0.001 g/L to 100 g/L in water at 25.degree. C.
BRIEF DESCRIPTION OF THE DRAWINGS
[0065] FIG. 1 indicates the controlled synthesis of hydrophobic
block via RAFT method by using different monomer/chain transfer
RAFT agent/initiator ratios. MMA stands for methyl methacrylate,
CTA stands for chain transfer agent, AIBN stands for
azoisobutyronitrile, and MOEP stands for methacryloyloxyethyl
phosphate.
[0066] FIGS. 2a through 2f illustrate Fourier transform Infrared
(FTIR) spectra of enamel treated with polymers at different pHs and
concentrations. FIGS. 2a, 2c and 2e relate to aqueous compositions
where the polymers are solubilized at 1 g/L. FIGS. 2b, 2d and 2f
relate to aqueous compositions where the polymers are solubilized
at 0.2 g/L. The pH of the treatment solution is 3.1 in FIG. 2a, 3.7
in FIG. 2b, 4.2 in FIGS. 2c and 2d and 7.0 in FIGS. 2e and 2f. The
insert in FIG. 2a is a FTIR spectrum of a phosphate copolymer.
[0067] FIGS. 3-1 through 3-3 indicate the UV spectra of a phosphate
block copolymer before and after binding with HA powder at
different conditions. FIG. 3-4 through FIG. 3-6 illustrate the UV
spectra of carboxylic block copolymers before and after binding
with HA at different conditions. FIG. 3-7 compares the binding
efficiencies of phosphorylated polymer and carboxylated polymer at
different concentrations and pHs.
[0068] FIG. 4 illustrates the effects of the block copolymers
described herein on calcium erosion by acid environments.
[0069] FIG. 5 indicates the anti-erosion efficiency of the
phosphorylated or carboxylated diblock copolymers and the enhanced
performance in presence of fluoride.
[0070] FIG. 6-1 is the enamel surface morphology after exposing to
acid. FIG. 6-2 is the enamel surface morphology which was treated
by phosphate block copolymer and then exposed to acid erosion.
DETAILED DESCRIPTION
Examples and Tests
[0071] 1. Controlled synthesis of hydrophobic blocks 2. Block
copolymer synthesis 3. Polymer/enamel binding 4. Quantitative
analysis of polymer/HA binding 5. Anti erosion test by phosphate
block copolymer 6. Anti erosion test by phosphate block copolymer
in presence of fluoride 7. SEM observation on the surface
morphology of enamel
[0072] 1. Controlled Synthesis of Hydrophobic Blocks
[0073] Typically, 10 mmol MMA, 0.25 mmol chain transfer RAFT agent
(e.g. the chain transfer agent
4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid)
and 0.1 mmol AIBN were dissolved in 10 ml 1,4-dioxane. After
purging with Argon for 1 h, the system was heated to 70.degree. C.
for a period of time. Gel permeation chromatography (GPC) was used
to monitor the average macromolecular weight (Mn) of hydrophobic
block. For example, Mn of polymethyl methacrylate (PMMA) can be
well controlled using different monomer/CTA/initiator ratios as
shown in FIG. 1.
[0074] 2. Block Copolymer Synthesis
##STR00011##
[0075] The synthesis of PMMA-b-PMOEP is shown in Scheme 1. Once the
targeted Mn of PMMA segment was achieved, certain amounts of
methacryloyloxyethyl phosphate (MOEP) in 1,4-dioxane was then
injected into the system with syringe and the reaction was further
allowed to continue for different reaction times. The composition
of PMMA-b-PMOEP could be adjusted by using different feeding ratios
and different polymerization times as shown in Table 1.
TABLE-US-00001 TABLE 1 Composition of PMMA-b-PMOEP using different
polymerization time and feeding ratios RAFT -chain Number of Number
of MMA transfer AIBN MOEP MMA in MOEP in (mol) agent(mol) (mol)
(mol) copolymer copolymer 100 2.5 1 50 17 9 100 2.5 1 50 19 14 100
2.5 1 80 17 14 100 2.5 1 80 20 35
[0076] The synthesis of PMMA-b-PAA by RAFT polymerization is shown
in Scheme 2. Once the targeted Mn of PMMA segment was achieved,
certain amounts of acrylic acid (AA) in 1,4-dioxane was then
injected into the system with syringe and the reaction was further
allowed to continue for different reaction times. The composition
of PMMA-b-PAA could be adjusted by using different feeding ratios
and different polymerization times as shown in Table 2. PAA stands
for poly acrylate acid.
##STR00012##
TABLE-US-00002 TABLE 2 Composition of PMMA-b-PAA using different
feeding ratios Molar ratios for monomers, RAFT agent and
initiator.sup.a MMA AA RAFT agent AIBN Structure of block copolymer
.sup.b 100 200 2.5 1 P(MMA).sub.20-b-P(AA).sub.19 100 500 2.5 1
P(MMA).sub.18-b-P(AA).sub.29 100 1000 2.5 1
P(MMA).sub.17-b-P(AA).sub.35
[0077] 3. Polymer/Enamel Binding
[0078] The structure of block copolymer used in this test is
P(MMA).sub.19-b-P(MOEP).sub.14. Before polymer treatment, the
surface of bovine enamel was pre-conditioned by immersing the
enamel in 1% citric acid solution (pH=3.8) for 5 min. Polymer
solution with different concentrations (0.2 and 1.0 g/L) and
different pHs (3.1, 4.2 and 7.0) were used to treat the bovine
enamel surface for 5 min at 50 rpm. Then the treated surface was
washed with phosphate buffer solution (pH=7.0) and acid solution
(pH=3.8) for three cycles (5 min/cycle). The treated and etched
enamel was characterized by FTIR spectroscopy after air dry. The
FTIR spectra are shown in FIG. 2. The peaks at 1452, 1407, and 869
cm.sup.-1 could be assigned to the existence of carbonated
hydroxyapatite on the surface. The peak at 1730 cm.sup.-1 could be
ascribed to the characteristic absorption peak of C=0 in block
copolymers. Both the effects of polymer concentration and pH on the
binding were evaluated. When increasing the polymer concentration
from 0.2 to 1.0 g/L, the relative intensity of peak at 1730
cm.sup.-1 was increased, indicating higher polymer concentration
could facilitate the binding efficiency. This could be ascribed to
the strong interaction between phosphate groups in the block
copolymer and the active site on enamel. Also, from the FIGS. 2a,
2c and 2e, when the pH is increased from 3.1 to 7.0 and the polymer
concentration is kept constant as 1.0 g/L, less polymer could be
adsorbed onto the enamel surface. The first and second dissociation
constants, pK.sub.al and pK.sub.a2 for phosphoric acid are 2.12 and
7.21, respectively. The phosphate groups of the copolymer are
believed to exist in the form of R--HPO.sub.4.sup.- and
R--PO.sub.4.sup.2-, where R stands for the polymer side chains
attached to the backbone. The former moiety (R--HPO.sub.4.sup.-)
will be dominant over the latter one at the pH range (3.1-7.0) in
this test. The phosphate block copolymer with negative charge could
bind with the calcium domains on HA surface via electrostatic
interaction. A lower pH value of the polymer solutions appears to
facilitate the binding.
[0079] 4. Quantitative Analysis of Polymer/Hydroxyapatite (HA)
Binding
[0080] The structures of block copolymers used in this test are
P(MMA).sub.19-b-P(MOEP).sub.9 and P(MMA).sub.17-b-P(AA).sub.35.
Polymer solutions of 5 ml with different concentrations and
different pH values were mixed with 100 mg HA powder for 2 h at
room temperature. After centrifuging for 10 min at 10000 rpm, the
solution was used tested by UV-vis spectroscopy. The absorbance of
thiocarbonyl group (C.dbd.S) before and after binding were utilized
to calculate the adsorbed polymer onto HA powder. The calibration
curve was performed by using polymer solution with known
concentrations. The UV spectra of phosphorylated or carboxylated
block copolymer before and after binding are shown in FIG. 3-1 to
FIG. 3-6. The calculated adsorbed polymer bound to HA is shown in
FIG. 3-7. It can be seen that when the polymer concentration is
gradually increased from 0.06 to 1.0 g/L, more and more polymer
could be adsorbed onto the HA surface.
[0081] 5. Anti Erosion Test of Phosphate Block Copolymer
[0082] The structure of block copolymer used in this test is
P(MMA).sub.17-b-P(MOEP).sub.12 and P(MMA).sub.18-b-PAA.sub.29.
Atomic absorption (AA) spectrometry is one of the most reliable and
sensitive methods on evaluating the dental erosion by monitoring
the mineral loss. The typical testing procedure used was as
follows. First, sintered hydroxyapatite (HA) discs were immersed in
1% citric acid (pH=2.5) for 15 min at room temperature, then soaked
in water and sonicated for 30 min. HA discs were fixed on a 6 well
plate by using KERR compounds. Note that only the top surface of HA
was exposed to the solutions. After air drying, the fixed HA discs
were challenged by 1% citric acid (pH=3.8) for 15 min at 37.degree.
C. with a shaking speed of 50 rpm. The solution was collected and
the calcium concentration was designated as [Ca].sub.ref. The HA
discs were washed with phosphate buffer solution (PBS, pH=7.0) and
then treated with polymer solution (1 g/L) or PBS (as blank) for 2
min. After another washing with PBS, the HA was again challenged
with citric acid for another 15 min. The solution was collected and
the calcium concentration was measured by AA spectrometry
[Ca].sub.treat. Because of the heterogeneity among HA samples, the
relative calcium level (Ca level), calculated as the following
equation (51), was utilized as an index to assess the protecting
efficiency against acid erosion.
Ca level = [ Ca ] treat [ Ca ] ref * 100 % Equation S 1
##EQU00001##
[0083] The different polymer treatments on HA surface could
influence the calcium level as shown in FIG. 4. The calcium level
after phosphorylated polymer treatments with different polymer
treating times was decreased from 91% for blank (non-polymer
treated) to 50%, 48%, 34%, 17% for 0.5, 1, 2, or 5 minutes polymer
treatment, respectively. The calcium level after carboxylated
polymer treatments with different polymer treating time was
decreased from 91% for blank (non-polymer treated) to 56%, 60%,
64%, 31% for 0.5, 1, 2, or 5 minutes polymer treatment,
respectively. The possible reason is that the adsorbed polymer onto
enamel/HA could form a protective layer and prevent the mineral
from release.
[0084] 6. Anti Erosion Test of Phosphate Block Copolymer in
Presence of Fluoride
[0085] Since the fluoride ion is widely used in oral care to
protect enamel against acid attack, phosphorylated or carboxylated
block copolymers can greatly enhance the efficiency of this
traditional treatment. Another anti erosion test based on
phosphorylated or carboxylated block copolymer and fluoride was
performed using the pH stat instrument. In this experiment, the HAP
discs were immersed in 15 ml 0.3% citric acid solution (pH 3.8) for
15 minutes before and after 2-minute treatment. The treatments were
polymer aqueous solution, or NaF aqueous solution or the mixture of
polymer and NaF aqueous solution. The amount of the 10 mM HCl added
over time to keep pH 3.8 was recorded. The % reduction
(anti-erosion efficiency) is calculated as
( 1 - ( acid addition / time ) after ( acid addition / time )
before ) * 100. ##EQU00002##
The corresponding results are shown in FIG. 5. It is clearly shown
that the anti-erosion efficiency of the mixture of NaF and polymer
is increased by 15-30% compared with the other treatments.
[0086] 7. Surface Morphology
[0087] The protective layer that is formed on the enamel surface
could prevent the mineral loss as indicated by previous data. This
layer could also protect the surface morphology of enamel surface
by obstructing the diffusion of external acid. Without any
treatment, enamel could be easily etched by acid as shown in FIG.
6-1. When the surface was treated by phosphate block copolymer
first, the surface morphology before and after acid erosion, the
tooth surface was largely preserved as shown in FIGS. 6-2.
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