U.S. patent application number 10/004828 was filed with the patent office on 2002-08-22 for method for reducing the viability of detrimental oral microorganisms in an individual, and for prevention and/or treatment of diseases caused by such microorganisms; and whitening and/or cleaning of an individual's teeth.
Invention is credited to Salonen, Jukka, Soderling, Eva, Stoor, Patricia, Yli-Urpo, Antti.
Application Number | 20020114768 10/004828 |
Document ID | / |
Family ID | 22987692 |
Filed Date | 2002-08-22 |
United States Patent
Application |
20020114768 |
Kind Code |
A1 |
Stoor, Patricia ; et
al. |
August 22, 2002 |
Method for reducing the viability of detrimental oral
microorganisms in an individual, and for prevention and/or
treatment of diseases caused by such microorganisms; and whitening
and/or cleaning of an individual's teeth
Abstract
The invention relates to a method for reducing the viability of
detrimental oral microorganisms in an individual, said method
comprising subjecting the individual's oral cavity to a bioactive
glass, the average particle size of which is less than 100 .mu.m.
Furthermore, this invention concerns a method for the prevention of
dental caries and/or gingivitis in an individual, said caries being
caused by a cariogenic bacteria; or for prevention or treatment of
periapical infections. Further the invention relates to a method
for the whitening and/or mechanical cleaning of an individual's
teeth.
Inventors: |
Stoor, Patricia; (Turku,
FI) ; Soderling, Eva; (Rusko, FI) ; Yli-Urpo,
Antti; (Littoinen, FI) ; Salonen, Jukka;
(Turku, FI) |
Correspondence
Address: |
James C. Lydon
Suite 100
100 Daingerfield Road
Alexandria
VA
22314
US
|
Family ID: |
22987692 |
Appl. No.: |
10/004828 |
Filed: |
December 7, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10004828 |
Dec 7, 2001 |
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09690810 |
Oct 18, 2000 |
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6342207 |
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09690810 |
Oct 18, 2000 |
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09260081 |
Mar 2, 1999 |
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6190643 |
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Current U.S.
Class: |
424/49 |
Current CPC
Class: |
A61K 33/42 20130101;
A61K 33/08 20130101; A61K 33/08 20130101; A61K 2300/00 20130101;
A61K 2300/00 20130101; A61K 2300/00 20130101; A61K 2800/412
20130101; C03C 2204/02 20130101; A61K 8/25 20130101; C03C 3/097
20130101; A61K 33/00 20130101; C03C 4/0007 20130101; A61P 31/04
20180101; A61K 33/42 20130101; A61Q 11/00 20130101; A61P 1/02
20180101; C03C 12/00 20130101; A61K 33/00 20130101 |
Class at
Publication: |
424/49 |
International
Class: |
A61K 007/16 |
Claims
1. A method for reducing the viability of detrimental oral
microorganisms in an individual, said method comprising subjecting
the individual's oral cavity to a bioactive glass, the average
particle size of which is less than 100 .mu.m.
2. The method according to claim 1, wherein the average particle
size is less than 50 .mu.m, preferably about 20 .mu.m or less.
3. The method according to claim 1, wherein the bioactive glass is
administered as a composition comprising particles of the bioactive
glass admixed into water or an aqueous solution.
4. The method according to claim 3, wherein the composition is a
paste comprising about 40 to 80 weight-% of bioactive glass.
5. The method according to claim 1, wherein the bioactive glass is
selected from a bioactive glass having the composition SiO.sub.2
53%; CaO 20%; P.sub.2O.sub.5 4% and Na.sub.2O 23% by weight, or
SiO.sub.2 53%; CaO 20%; P.sub.2O.sub.5 4%, Na.sub.2O 6%, K.sub.2O
12% and MgO 5% by weight.
6. The method according to claim 1, wherein the detrimental oral
microorganisms are cariogenic bacteria.
7. The method according to claim 6, wherein the cariogenic bacteria
are Actinomyces naeslundii and/or Streptococcus mutans.
8. The method according to claim 1, wherein the detrimental oral
microorganisms are periodontal bacteria.
9. The method according to claim 8, wherein the periodontal
bacteria are Actinobacillus actinomycetemcomitans and/or
Porphyromonas gingivalis.
10. The method according to claim 1, wherein the treatment is
carried out for about 10 minutes.
11. The method according to claim 1, wherein the viability of
benign oral microorganisms is reduced less than the viability of
the detrimental oral microorganisms.
12. The method according to claim 12, wherein the benign oral
microorganism is Streptococcus sanguis.
13. A method for the prevention of dental caries and/or gingivitis
in an individual, said caries being caused by a cariogenic
bacteria, or for prevention or treatment of periapical infections,
said method comprising subjecting the individual's oral cavity
and/or root canals to a bioactive glass, the average particle size
of which is less than 100 .mu.m.
14. The method according to claim 13, wherein the average particle
size is less than 50 .mu.m, preferably about 20 .mu.m or less.
15. The method according to claim 13, wherein the bioactive glass
is administered as a composition comprising particles of the
bioactive glass admixed into water or an aqueous solution.
16. The method according to claim 15, wherein the composition is a
paste comprising about 40 to 80 weight-% of bioactive glass.
17. The method according to claim 13, wherein the bioactive glass
is selected from a bioactive glass having the composition SiO.sub.2
53%; CaO 20%; P.sub.2O.sub.5 4% and Na.sub.2O 23% by weight, or
SiO.sub.2 53%; CaO 20%; P.sub.2O.sub.5 4%, Na.sub.2O 6%, K.sub.2O
12% and MgO 5% by weight.
18. The method according to claim 17, wherein the cariogenic
bacteria are Actinomyces naeslundii and/or Streptococcus
mutans.
19. The method according to claim 13, wherein the treatment is
carried out for about 10 minutes.
20. A method for the whitening and/or mechanical cleaning of an
individual's teeth, said method comprising subjecting the
individual's oral cavity to a bioactive glass, the average particle
size of which is less than 100 .mu.m.
21. The method according to claim 20, wherein the average particle
size is less than 50 .mu.m, preferably about 20 .mu.m or less.
22. The method according to claim 20, wherein the bioactive glass
is administered as a composition comprising particles of the
bioactive glass admixed into water or an aqueous solution.
23. The method according to claim 22, wherein the composition is a
paste comprising about 40 to 80 weight-% of bioactive glass.
24. The method according to claim 20, wherein the bioactive glass
is selected from a bioactive glass having the composition SiO.sub.2
53%; CaO 20%; P.sub.2O.sub.5 4% and Na.sub.2O 23% by weight, or
SiO.sub.2 53%; CaO 20%; P.sub.2O.sub.5 4%, Na.sub.2O 6%, K.sub.2O
12% and MgO 5% by weight.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a method for reducing the
viability of detrimental oral microorganisms in an individual, and
for prevention of dental caries and gingivitis, and for prevention
or treatment of periapical infections, and whithening and/or
mechanical cleaning of an individual's teeth.
BACKGROUND OF THE INVENTION
[0002] The publications and other materials used herein to
illuminate the background of the invention, and in particular,
cases to provide additional details respecting the practice, are
incorporated by reference.
[0003] Bioactive glasses have been tested as substitutes for
reconstruction of defects of the facial bones (1), rehabilitation
of the dentoalveolar complex (2), regeneration of periodontal
pockets (3), and recently also for treatment of hypersensitive
teeth (4). The surface reactive bioactive glass contains SiO.sub.2,
Na.sub.2O, CaO and P.sub.2O.sub.5. The chemical bond with bone in
vivo is reported to result from the leaching of Na.sup.+-ions and
the congruent dissolution of calcium, phosphate and silica from the
glass in an aqueous environment, giving rise to an Si-rich layer on
the material. The Si-rich layer acts as a templet for a calcium
phosphate precipitation, which then binds to the bone (5).
Bioactive glass has been successfully used for reconstructions of
closed bone defects, which are not exposed to the external
environment after the clinical procedure (1). However, there are a
number of conditions for which bioactive glasses are used as
therapeutic materials but that, at the same time, are imminently
prone to microbial infections. These include clinical conditions
such as infected frontal sinuses (6), periodontal pockets (3) and
hypersensitive teeth as a complication of periodontal treatment or
tooth wear that has resulted in the exposure of dentin and dentinal
tubules (4). Obviously, the demonstration of any antibacterial
activity of the biactive glass would add to the therapeutic value
of the material in the clinical conditions described. Earlier
studies have shown that P. gingivalis is agglutinated in the
presence of granules (315-500 .mu.m) of the bioactive glass S53P4
in an aqueous environment due to Ca.sup.+2-ions released from the
granules (19, 7). The minimum Ca.sup.2+-concentration needed to
induce agglutination of P. gingivalis was found to be 0.04 g/l (7).
In these studies, however, no reduction of the viability of the
bacteria was noticed.
[0004] Earlier studies have shown that the bioactive glass can act
as a vehicle for Ca.sup.2+, PO.sub.4.sup.3-, Na.sup.+ and
Si.sup.4+, which then mineralise type I collagen and enhance
mineral formation in the dentinal tubules. Therefore, an aqueous
preparation comprising bioactive glass may have potential to be
used as a paste for the treatment of hypersensitive teeth with
recessed gingival margins and exposed dentine. Positive effects of
such a treatment have been obtained already after 10 to 60 min,
which makes this particular material interesting even from a
clinical point of view (4).
OBJECT AND SUMMARY OF THE INVENTION
[0005] The object of the present invention is to provide an easy,
quick and safe method to reduce the viability of detrimental oral
microorganisms in an individual. A particular object is to achieve
a method which is not based on use of antibiotic drugs associated
with the risk of causing microbe restistence.
[0006] A particular object is to provide a method to reduce the
viability of cariogenic bacteria and periodontal bacteria.
[0007] Another particular object is to provide a method to
effectively reduce the viability of the detrimental oral
microorganisms while the viability of non-pathogenic oral
micro-organisms is reduced to a less degree.
[0008] A further object of this invention is to provide methods for
prevention of dental caries and/or gingivitis, and for whitening of
an individual's teeth, wherein said methods are due to the
reduction of the viability and thus the decrease of the number of
the detrimental oral micro-organisms.
[0009] Still one object is to achieve mechanical cleaning and
whitening of an individual's teeth, wherein the whitening is a
result of said mechanical cleaning.
[0010] Thus, according to one aspect, the invention concerns a
method for reducing the viability of detrimental oral
microorganisms in an individual, said method comprising subjecting
the individual's oral cavity to a bioactive glass, the average
particle size of which is less than 100 .mu.m.
[0011] According to another aspect, the invention concerns a method
for the prevention of dental caries and/or gingivitis in an
individual, said caries being caused by a cariogenic bacteria, or
for prevention or treatment of periapical infections, said method
comprising subjecting the individual's oral cavity and/or root
canals to a bioactive glass, the average particle size of which is
less than 100 .mu.m.
[0012] According to a further aspect, this invention concerns a
method for the whitening of an individual's teeth, said method
comprising subjecting the individual's oral cavity to a bioactive
glass, the average particle size of which is less than 100
.mu.m.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIGS. 1A to 1E show the effect of 1) the powdered bioactive
glass S53P4 (continuous lines) and 2) control containing no
bioactive glass (dashed lines) on the number of viable microbes in
suspension. Values shown are means; bars indicate range; n=3.
CFU=colony-forming units.
[0014] FIGS. 2A to 2E show the effect of 1) SiO.sub.2 powder
(continuous lines) and 2) control containing no SiO.sub.2 powder
(dashed lines) on the number of viable counts microbes in
suspension. Values shown are means; bars indicate range; n=2 to 3.
CFU=colony-forming units.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The term "reducing the viability of detrimental oral
micro-organisms" shall be understood to include reduction to a
certain decreased level as well as reduction to zero, i.e. complete
elimination of viable microorganisms.
[0016] The term "average particle size" means that 50% of the
number of particles have a size less than or equal to the value
mentioned (e.g. 100 .mu.m) and that 50% of the number of particles
have a size greater than or equal to said value.
[0017] According to a preferred embodiment, the average particle
size is below 50 .mu.m, most preferably about 20 .mu.m or less. The
size of the individual particles may vary in a range extending from
a value below 1 .mu.m up to about 500 .mu.m.
[0018] The "oral cavity" to be treated according to this invention
means particularly the individual's teeth and periodontal regions
in the mouth. Especially the individuals teeth down to the gingival
margin and/or the periodontal pockets of the individual's mouth
shall be treated, as well as root canals in endodontic
treatment.
[0019] The bioactive glass is preferably administered as a
composition comprising particles of the bioactive glass admixed
into water or an aqueous solution. Especially preferable is a paste
comprising about 40 to 80 weight-% of bioactive glass. The
composition can optionally also include other ingredients.
According to an especially preferable embodiment, the composition
is a tooth paste for regular use, including the bioactive
glass.
[0020] Some typical and preferable bioactive glass compositions are
presented in Table 1.
1TABLE 1 Composition (weight-%) of some bioactive glass types 1-17
Glass Type Na.sub.2O CaO P.sub.2O.sub.5 B.sub.2O.sub.3
Al.sub.2O.sub.3 SiO.sub.2 1 S63.5P6 15.00 14.00 6.00 0.50 1.00
63.50 2 S57.5P5 16.00 18.00 5.00 3.00 0.50 57.50 3 S65.SP1 17.00
13.00 1.00 1.00 2.50 65.50 4 S52P3 18.00 24.00 3.00 0.00 3.00 52.00
5 S56P6 19.00 16.00 6.00 1.50 1.50 56.00 6 S51P7 20.00 17.00 7.00
3.00 2.00 51.00 7 S51P2 21.00 21.00 2.00 2.00 3.00 51.00 8 S64P0
22.00 10.00 0.00 2.50 1.50 64.00 9 S53P4 23.00 20.00 4.00 0.00 0.00
53.00 10 S45P7 24.00 22.00 7.00 2.00 0.00 45.00 11 S52P8 25.00
12.00 8.00 0.50 2.50 52.00 12 S46P0 26.00 25.00 0.00 2.00 1.00
46.00 13 S38P8 27.00 23.00 8.00 1.00 3.00 38.00 14 S48P2 28.00
19.00 2.00 1.50 1.50 48.00 15 S55.5P4 29.00 11.00 4.00 0.00 0.50
55.50 16 S45.5P5 30.00 15.00 5.00 2.50 2.00 45.50 17.sup.x) 13-93
6.00 20.00 4.00 0.00 0.00 53.00 .sup.x)this glass contains in
addition 12% of K.sub.2O and 5% of MgO (weight-%).
[0021] Particularly preferable bioactive glasses are the glass
S53P4, which has the composition SiO.sub.2 53%; CaO 20%;
P.sub.2O.sub.5 4% and Na.sub.2O 23%, and the glass 13-93, which has
the composition SiO.sub.2 53%; CaO 20%; P.sub.2O.sub.5 4%,
Na.sub.2O 6%, K.sub.2O 12% and MgO 5%.
[0022] The method according to the invention is particularly
effective to reduce the viability of cariogenic bacteria,
especially Actinomyces naeslundii and/or Streptococcus mutans. Also
periodontal bacteria (i.e. bacteria causing gingivitis). Typical
periodontal bacteria are Actinobacillus actinomycetemcomitans
and/or Porphyromonas gingivalis. However, the reduction of the
viability of non-pathogenic oral bacteria such as Streptococcus
sanguis is lower than that for the detrimental oral microorganism.
This is a very favourable feature, because essential reduction of
the non-pathogenic oral bacteria is not wanted.
[0023] The duration of the treatment depends i.a. on the particular
bioactive glass composition used, the average particle size, the
bacteria in question, etc. As will be seen from the experimental
data, a period of about 10 minutes may be enough to effectively
eliminate viable cariogenic bacteria (bioactive glass S53P4,
average particle size 20 .mu.m), while a longer treatment is
necessary for periodontal bacteria.
[0024] Oral bacteria are known to cause discolouring of teeth, as
also coffee, tea, tobacco etc. Bioactive glass is therefore, as an
effective antibacterial agent and as a mechanically cleaning agent,
useful for cleaning and whitening of the teeth.
[0025] The invention is described in more detail in the
Experimental Section.
[0026] Experimental Section
[0027] The purpose of this study was to examine the antibacterial
effects of a paste made of the bioactive glass S53P4 (8) on oral
microorganisms representing periodontal pathogens,
caries-associated microorganisms and benign oral microflora. Two
major pathogens were used: Actinobacillus actinomycetemcomitans,
which has been suggested to play a role in juvenile periodontitis
(9, 10), and Porphyromonas gingivalis, which has been associated
with destructive periodontal lesions in adults (11, 12, 13). Also
were studied Actinomyces naeslundii, which is associated with root
caries; Streptococcus mutans, which is considered to play a major
role in caries; and Streptococcus sanguis as a representative of
the benign oral microbiota (14).
[0028] Materials and Methods
[0029] Materials
[0030] The bioactive glass powder S53P4 used in this study was
produced by Abmin Technologies Ltd, Turku, Finland. The composition
of the bioactive glass S53P4 given by weight is: SiO.sub.2 53%,
Na.sub.2O 23%, CaO 20% and P.sub.2O.sub.5 4%. The bioactive glass
was prepared from reagent grade Na.sub.2CO.sub.3,
CaHPO.sub.4.times.2H.sub.2O, CaCO.sub.3 (Merck, Darmstadt, Germany)
and Belgium sand. The glass batches were melted for 3 h at
1360.degree. C. After melting, the glass was cast into a plate,
which was cooled from 520.degree. C. to 220.degree. C. at 1.degree.
C./min in an annealing oven. The oven was turned off and air-cooled
to room temperature. The plate was crushed and dry ground in an
agate mill. Powder, of particle size <45 .mu.m, (average
particle size 20 .mu.m), was sieved out of the batch (8).
[0031] The powder was combined with a microbial suspension using a
ratio of glass powder and liquid (50 mg and 30 .mu.l,
respectively), simulating the composition used for treatment of
hypersensitive teeth (4).
[0032] As controls we used 1) no added glass powder and 2) an inert
SiO.sub.2 powder, containing 100% SiO.sub.2, of particle size
<45 .mu.m (Biomaterials project, Institute of Dentistry,
University of Turku, Finland).
[0033] Microorganisms
[0034] The microorganisms used were Actinobacillus
actinomycetemcomitans (ATCC 29523), Porphyromonas gingivalis (ATCC
33277), Actinomyces naeslundii (clinical isolate), Streptococcus
mutans (NCTC 10449) and Streptococcus sanguis (NCTC 10904).
[0035] Preparation of the Microbial Suspensions
[0036] Precultivation of A. actinomycetemcomitans, S. mutans and S.
sanguis was performed at 37.degree. C. in BHI (Brain Heart
Infusion, Unipath Ltd, Hampshire, England). After approximately 18
h of growth, the cells were washed once in saline (S. mutans and S.
sanguis) or in Reduced Transport Fluid (RTF: 0.6 g/l
K.sub.2HPO.sub.4.times.3H.sub.2O, 0.23 g/l NaCl, 0.23 g/l
(NH.sub.4).sub.2SO.sub.4, 0.11 g/l KH.sub.2PO.sub.4, 0.1 g/l
MgSO.sub.4.times.7H.sub.2O, 0.37 g/l disodium ethylenedinitrilo
tetraacetate;
C.sub.10H.sub.14N.sub.2Na.sub.2O.sub.8.times.2H.sub.2O, 0.4 g/l
Na.sub.2CO.sub.3, 0.2 g/l dithiothreitol;
C.sub.4H.sub.10O.sub.2S.sub- .2) (15) (A. actinomycetemcomitans).
The suspensions were adjusted with saline or RTF to an optical
density of approximately 1.0 [A.sub.700; corresponding to
10.sup.5-10.sup.7 colony forming units, (CFU)/ml]. P. gingivalis
was precultivated anaerobically (80% N.sub.2, 10% CO.sub.2, 10%
H.sub.2) at 37.degree. C. on Brucella agar plates (Difco
Laboratories, Detroit, USA). The cells were harvested after 6 days'
growth, washed once in Brewer Thioglycollate medium (500 g/l Beef
Infusion, 5 g/l NaCl, 2 g/l K.sub.2HPO.sub.4, 10 g/l Proteose
Peptone, 5 g/l Bacto Dextrose, 0.5 g/l Na-Thioglycollate, 0.5 g/l
Bacto Agar, 0.002 g/l Bacto Methylene Blue) and finally adjusted
with Brewer Thioglycollate medium to an optical density of
approximately 1.0 (A.sub.700; corresponding to 10.sup.4-10.sup.5
CFU/ml). A. naeslundii was precultivated in Brewer Thioglycollate
medium (Difco) at 37.degree. C. for 3 days, washed once in RTF and
adjusted with RTF to a density of approximately 1.0 (A.sub.700;
corresponding to 10.sup.5-10.sup.6 CFU/ml).
[0037] Incubation Experiments
[0038] The bioactive glass powder (50 mg) and 30 .mu.l of the
microbial suspension were first vortexed for thorough mixing for 10
min at room temperature in Eppendorf tubes (Sarstedt, Germany),
followed by incubation without agitation for 50 min at 37.degree.
C. The controls contained 1) no added bioactive glass powder or 2)
50 mg inert SiO.sub.2 powder (particle size <45 .mu.m).
[0039] For assessment of viability as CFU, the incubation was
stopped by adding 470 .mu.l RTF (A. Actinomycetemcomitans, P.
gingivalis, A. naeslundii) or saline (S. mutans, S. sanguis),
followed by vortexing and gentle sonication for 2 s to detach the
microorganisms from the bioactive glass powder and from the inert
SiO.sub.2 powder. The assessment of viability as CFU of the
microbial suspensions was performed on solid growth media by
cultivating 10 .mu.l samples from the suspensions diluted in saline
(10.sup.1-10.sup.7). The undiluted suspension was also cultivated
by using 20 .mu.l samples. A. actinomycetemcomitans and A.
naeslundii were cultivated on blood agar anaerobically at
37.degree. C. for 3 days and approximately 18 h, respectively. P.
gingivalis was cultivated anaerobically at 37.degree. C. for 6 days
on Brucella agar plates. S. mutans and S. sanguis were cultivated
on Mitis salivarius agar for approximately 18 h at 37.degree. C.
aerobically in an atmosphere consisting of 74% N.sub.2, 19% O.sub.2
and 7% CO.sub.2. The experiment was performed with 2-3 parallels
and repeated once.
[0040] Ion Release from the Bioactive Glass Paste and Related pH
Changes
[0041] The release of ions from the bioactive glass powder (50 mg)
during the 60 min contact with saline (30 .mu.l) was analyzed with
a Direct Current Plasma Atomic Emission Spectroscopy DCP-AES at the
Department of Chemistry at .ANG.bo Akademi University, Turku,
Finland. The determinations were performed in triplicate. After the
vortexing (10 min) and incubation (50 min) the samples were
suspended in 5 ml laboratory grade H.sub.2O (Milli-QUF PLUS,
Millipore, Molsheim, France), rapidly mixed and immediately
filtrated with a Millex-GS 0.22 mm filter (Millipore).
[0042] The time-dependent changes in the pH values of saline and
Brewer Thioglycollate medium were monitored after 10-min and 60-min
incubation with the bioactive glass powder. The measurements were
performed with a combination electrode pHC4406 (Radiometer,
Copenhagen, Denmark).
[0043] Results
[0044] The time-dependent release of calcium, phosphorous, silica
and sodium from the bioactive glass paste is given in Table 2. For
calcium, phosphorous and sodium, the amount of released ions did
not increase during the prolonged incubation, but for silica the
amount tripled during the 10-60-min incubation. The increased
osmotic pressure was created mostly by an almost immediate release
of high amounts of sodium, which corresponds to a concentration of
3.38% at 10 min and 3.50% at 60 min.
[0045] Table 2. Measurements of the release of four elements from
the bioactive glass S53P4 in powdered form, showing almost instant
release of calcium, phosphorous and sodium. The amount of released
silicon tripled during the time period, 10-60 min. The values shown
are means.+-.standard deviations (s) in mg/l.
2 10 min 60 min Element Mean s Mean s Ca 2990 .+-. 210 3520 .+-.
190 P 170 .+-. 30 160 .+-. 000 Si 1440 .+-. 120 4740 .+-. 50 Na
33790 .+-. 540 34980 .+-. 220
[0046] During the incubation with bioactive glass powder, the mean
(.+-.standard deviation) of the pH of both the saline and the
Brewer Thioglycollate medium increased in 10 min from 6.9 (.+-.0.3)
to 10.8 (.+-.0.1). No further increase of the pH was seen.
[0047] A. actinomycetemcomitans totally lost its viability in
contact with the bioactive glass powder within 60 min. A major
decrease in the number of viable microbes was already seen within
10 min, as the number of viable microbes decreased from
9.times.10.sup.5 to 9.times.10.sup.2. Also P. gingivalis lost its
viability in contact with the glass powder within 60 min. After 10
min, a decrease from 9.times.10.sup.4 to 1.times.10.sup.3 in the
number of viable cells was seen. S. mutans lost its viability
almost totally, from 6.times.10.sup.6 to 0.8.times.10.sup.1, after
10 min incubation with the bioactive glass powder. A total loss of
viability of A. naeslundii was also seen already after 10 min. S.
sanguis showed a significant loss of viability, at 10 min, from
7.times.10.sup.6 to 1.times.10.sup.4 and at 60 min, further down to
1.times.10.sup.3. (FIG. 1). However, S. sanguis was the only
microbe that had any viable cells left after 60 min.
[0048] The incubations with the reference material, the inert
SiO.sub.2, powder, showed results similar to those of the controls
with no glass powder (FIG. 2).
[0049] Discussion
[0050] In this study the bioactive glass paste showed a broad
antibacterial effect on the microorganisms tested. The effect found
may be due to several influences including high pH, osmotic effects
and the Ca.sup.2+-concentration (7).
[0051] Since the bioactive glass S53P4 reacts in a surface reactive
manner in an aqueous environment, the release of ions and
consequently the rise of the pH increases with an increasing
surface area of the glass. In the form of a powder (<45 .mu.m)
the surface area of the glass is large per weight unit, and thus
the release of ions is high. In our experiments the surface
area/volume (SA/V) ratio was very high, approximately 1920
cm.sup.-1. Earlier experiments with bioactive glass S53P4 granules
(297-500 .mu.m) where the SA/V ratio was 0.4 cm.sup.-1 showed
almost a linear increase in release of ions during the first 7
hours (16). Owing to the high SA/V ratio in the present experiment
the release of ions was up to .times.300 times greater during the
60 min incubation than in the earlier experiments with granules (60
min: Ca 24 mg/l, P not detected, Si 15 mg/l, Na 12 mg/l) (16).
Thus, the release of ions was faster from the bioactive powder than
from the granules. Also the pH change observed with the
<45-.mu.m glass powder within 60 min (pH 7->11) was higher
than that reported with granules earlier (pH 7->9) (8).
[0052] Most heterotrophic bacteria grow well in media with an
osmotic pressure created by 0.75% salt. Concentrations higher than
1% become inhibitory for most bacteria. However, many streptococci
of the oral cavity can grow well on a 5% sucrose medium, while the
growth of most other oral bacteria is inhibited under such
conditions (17). As judged by the concentrations of the separate
ions released from the glass powder, the total osmotic pressure
was, already after 10 min, created by a concentration higher than
3% and, after 60 min, by a concentration above 4% (see Table 2).
Since the outer membrane of gram-negative bacteria (A.
actinomycetemcomitans, P. gingivalis) is reported to be a more
efficient permeability barrier than the cell wall of the
gram-positive bacteria (A. naeslundii, S. mutans, S. sanguis) (18),
the osmotic effects due to the bioactive glass paste could partly
explain the relative resistance of the gram-negative microorganisms
and the more rapid loss of viability of A. naeslundii and S.
mutans. Because S. sanguis, despite the lack of an effective
permeability barrier, was the only microbe that managed to maintain
some viability also other mechanisms must be involved.
[0053] The Ca.sup.+2-ion concentration measured in association with
the paste of bioactive glass powder used in this study was much
higher (3.0-3.5 g/l) than that shown (0.04 g/l ) in the earlier
study (7) using granules (315-500 .mu.m) of the same bioactive
glass.
[0054] In addition to the immediate antibacterial effect due to the
instant release of ions from the bioactive glass, possible residues
of bioactive glass cause long term effects over days and even
months, due to the continuing leaching of ions from the bioactive
glass.
[0055] In conclusion, the bioactive glass paste appears to possess
a broad antimicrobial effect on microorganisms of both supra- and
subgingival plaque. Consequently, the bioactive glass paste may
have beneficial effects on oral health both from a cariological and
a periodontal point of view, in addition to its more direct
therapeutic effect on root surface hypersensivity. Apparently, the
clinical benefits of the bioactive glass powder when used as a
paste or as a component in toothcare products come from a
combination of good influences rather than from any single
property, such as its ability to reduce bacterial growth. These
influences include mechanical cleaning and remineralisation of both
dentine and enamel.
[0056] It will be appreciated that the methods of the present
invention can be incorporated in the form of a variety of
embodiments, only a few of which are disclosed herein. It will be
apparent for the specialist in the field that other embodiments
exist and do not depart from the spirit of the invention. Thus, the
described embodiments are illustrative and should not be construed
as restrictive.
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