Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
FINE FILLING METHOD AND FINE FILLER FOR DENTAL PURPOSES
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dental fine filling
method for protecting or restoring pits and fissures or minute
decalcified surface lesions in enamel by rubbing therein a
powder, granules, a solution (suspension) or paste containing
hydroxy-apatite or tetracalcium phosphate with or without
adjuvants and then optionally covering the site with a polymer
or fluoride, and to a dental fine filler used for such filling,
which is based on hydroxy-apatite or tetracalcium phosphate
which may or may not contain calcination-promoting protein or
a coating agent.
2. Description of the Prior Art
When plaque deposits on the surface of enamel, acids
produced therein by microorganisms gradually etch the enamel
and produce minute lesions therein. (This process is herein-
after referred to as decalcifical:ion. It is recognized thatdecalcified lesions are recalcified and restored by saliva.)
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O ~ the enamel is decalcified, plaque is soon redeposited on
the decalclfied lesions, even though it is removed by brushing,
so that the enamel is subjected to repeated decalcification
due to acids. Thus, decalcification advances through repe-titive
occurrence of decalcification, removal of the plaque, rede-
position of the plaque and decalcification, ending in visually
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detectable caries. In conventional dental treatment, the
hard tissue of a visually detectable carious tooth including
it's periphery is resected, and various plastics, cements
or metals are filled in the resected site as a replacement of
the lesion~ ~owever, this method requïres a high degree of
technical skill. In addition, if filling is incomplete, the
carious process again advances from the periphery of the filling
m~terial. In recent years, a sealant method has been developed
in which the pits and fissures that are most susceptible to
caries or decalcified lesions caused by the incipient decalci-
fication are occluded with a sealant that is a polyacrylate,
polyurethane or other polymer to isolate them from the oral
environment, thereby preventing caries from occurring.
According to the sealant method, the pits and fissures or
~ 15 decalcified lesions, which may have been treated with acids
; depending upon the sealant agents used, axe occluded therewith
; ~ to prevent plaque from occurring and acting on the site,
~; thereby preventing caries. In this method, however, insufficient
or excessive acid treatment or deposition of saliva on the acid-
treated surface may cause a decline in the bonding force of
the sealants with respect to pits and fisssures or decalcified
lesions~ The sealants, if occluded in too large an amount,
may also brea~ due to mastication and biting. Thus, with the
sealant method, there is the possibility that the sealants
may dislodge depending upon their quality and the technical
skill of the operator, and the effectiveness of the method varies
~ith the clinical skill of the operator. With the sealant
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method, difficulty is encountered in covering minute decalci-
fied lesions with the sealant agents and in the recalcification
of the covered decalcified lesions since they do not come into
contact with saliva. In efforts to enhance resistance to
caries by the reinforcement or protection of dentin, fluorine
ions are applied to the surface of teeth or added to drinking
water and foods. However, a special technique is required
for the manipulation of fluorine compounds. As a method of
depositing an enamel composition on the surface of teeth,
Japanese Patent Application Laid-Open ~XOKAI) No. 47-1567
proposes to form brassid on the surface of teeth using as the
medium a gelatiniform substance prepared in such a manner that
its toxicity and final pH do not harm the mouth, and to convert
brassid to hydroxy-apatite. However, this method not only
1~ requires an extended period of time for the conversion of
brassid to hydroxy-apatite, but also requires use of the
gelatiniform substance so as to help bond brassid to the surface
of teeth.
Application of fluorine ex:ists as a procedure for
reinforcing the surface of teeth, and the sealant method or the
method disclosed in Japanese Patent Application Laid-Open
(KOKAI~ No. 47-1567 is available as a procedure for protecting
the pits and fissures and restoring decalcified lesions.
However, these methods re~uire special clinical skill and
involve the difficulties mentioned above.
SUMMARY OF THE INVENTION
As object of the present invention is to provide a
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dental fine filling method which can easily be
carried out in s short period of time with no need
for any special clinical skill for safe protection
and restoration of pits and fissures and decalcified
lesions.
According to one aspect of the invention,
there is thus provided a dental fine filling method
for protecting or restoring pits, fissures or minute
decalcified surface lesions in the enamel of a tooth,
which method comprises rubbing on the surface of the
tooth a fine filler containing finely divided
particles of hydroxy-apatite or tetracalcium
phosphate, whereby the hydroxy-apatite or tetracal-
clum phosphate is bonded to the tooth and recalcific-
ation of the tooth is promoted due to the presence of
saliva.
The present invention:also provides, in a
further aspect thereof, a flne-~ filler for dental
purposes, comprising finely dîvided particles of
20- hydroxy-apatite or tetracalcium phosphate and a
calcification promoting proteln selected from the
group consisting of phosvitan, casein and histidine-
~ rich protein.
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According to the method of the invention,
suspensions of finely divided hydroxy-apatite
containing radioactive calcium and finely divided
brassid were prepared and added to an artificial
tooth prepared by sintering hydroxy-apatite for the
immersion thereof. The upper face of the artificial
tooth was rotatively abraded through a rubber
membrane. After elapse of a certain time, the
artificial tooth was removed and, soon thereafter, a
large amount of distilled water was added dropwise
thereto for washing, followed by the addition of a
PSC cocktail. Radioactivity of the artificial tooth
was measured with a liquid scintillation counter,
whereby the amounts of hydroxy-apatite and brassid
bonded to the artificial tooth '~
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were determined. As a result, it was found that the bonded
amounts depended upon the pH of the suspensions, but the
amount of hydroxy-apatite bonded was much larger than the amount
of brassid bonded in any pH range. It was also confirmed by
nominal experimentation that tetracalcium phosphate ~Ca4~PO4)2O~
obtained by sintering an equimolar mixture of tricalcium
phosphate and calcium oxide at 1500C bonded easily to a tooth,
as was the case with hydroxy-apatite, and the tetracalcium
phosphate bonded changed to hydroxy-apatite immediately upon
contact with saliva to promote the recalcification of the tooth.
The fact that these substances promote the recalfification of
teeth and protect the teeth from decay was supported by the
following experimentation. An extracted 3rd molar subjected
to ar,tificial caries was immersed under agitation in a hydroxy-
apatite or tetracalcium phosphate paste at 37C for 5 hours,and the surface enamel layer of the tooth was thereafter
observed under a polarization microscope. As a result, decalci-
fied lesions were found over a wide range of the control group,
whereas the hydroxy-apatite or tetracalcium phosphate-treated
group was recalcified on the surface layer, with the decalci-
fied lesions being thinner than those of the control group.
These indicate that hydroxy-apatite or tetracalcium phosphate
is efficiently bonded to the surfaces of teeth to cover or
cure the decalcified lesions and promotes the recalcification
of enamel by contact with saliva. Thus, the present invention
provides a method for the protection of pits and fissures or
- for the restoration of decalcified lesions by making use of the
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properties of hydroxy-apatite or tetracalcium phosphate bonding
selectively to the surface decalcified lesions of teeth. The
invention also provides a fine filler used in the method.
It is desired that the hydroxy-apatite or tetracalcium
phosphate to be used be as finely divided as possible. In
general, they are finely divided to about 0.02 to 10 microns
for use. The finely divided hydroxy-apatite or tetracalcium
phosphate is formulated to about a 5 to 95~ solution (suspension)
or paste with or without water OI' a coating agent. These
materials are rubbed on a tooth, from which the plaque has been
removed, with a fingertip, brush, stick, cloth or the like for
at least 1 min, preferably 3 min. In the course of this
operation, the hydroxy-apatite or tetracalcium phosphate is
further finely divided and bonded to the pits and fissures
or minute decalcified lesions of the enamel. Since the hydroxy-
apatite or tetracalcium phosphate is the highest nutritive
calcium substance, the patient may swallow extra calcium salts
remaining in the mouth. Preferably, washing of the mouth with
water should be carried out lightly and limited to about one
time. The recalcification of the hydroxy-apatite or tetracalcium
phosphate bonded to the tooth surface is promoted due to the
presence of saliva.
It is preferred to use powders, granules, solutions
(suspensions) or pastes of hydroxy-apatite or tetracalcium
phosphate which are prepared by mixing with a suitable amount
of an a~juvant selected from a phosphate such as tricalcium
phosphate and monohydrogen calcium phosphate; a fluoride such
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as sodium fluoride, sodium monoFluorophosphate, apatite
fluoride and stannous fluoride; calcification-promoting protein
such as phosvitin, casein and histidine-rich protein (these
proteins were found to act as the catalysts and accelerators
for the calcification of hydroxy-apatite); or a mixtuxe thereof,
since the adjuvant promotes the recalcification of the decalcified
lesions and reinforces the covered layer. The amounts of these
adjuvants to be added may be selected arbitrarily depending
upon their types. ~n general, however, the phosphate should
be used in amounts of about 1 to 60%, the fluoride in an amount
of 1000 ppm at most and the calcification-promoting protein
in an amount of about 1~ at most, with respect to the hydroxy-
apatite and/or tetracalcium phosphate. The coating agent used
for tne paste may bs vinyl acetate, glue, polyacrylic acid,
gum arabic or the like.
Thus, the hydroxy-apatite or tetracalcium phosphate is
bonded to the surface of teeth merely by rubbing thereon the
hydroxy-apatlte or tetracalcium phc~sphate-containing paste,
and is recalcified by saliva. The presence of the adjuvants
serves to enhance such recalcification and the strength of
teeth. The method according to the present invention can
easily be carried out without recourse to acid treatments,
moisture-proofing and polymerization treatments applied in
the conventional sealant method, and without any special
clinical skill. Further, the hydroxy-apatite, tetracalcium
phosphate, adjuvants and coating agents have no adverse in-
fluence upon the llving ~ody. Still further, the hydroxy-apatite
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is a component the same as that found in teeth, whlle the
tetracalcium phosphate is easily converted to hydroxy-apatite
by saliva. Thus, since these substances do not constitute
foreign matter with respect to teeth, unlike the prior art
sealant agents, and since they bond firmly to the pits and
fissures and decalcified lesions with no risk of being dislodged,
comple-tely restored teeth are produced. In addition, plasti-
ci~ers, solvents, dilutents and so on may be added to the
paste comprising hydroxy-apatite or tetracalcium phosphate
and the calcification-promoting protein and coating agent in
such a manner that the resulting system has a viscosity suitable
for covering the surface of teeth and providing a film of
uniform thickness. The application of such a system to the
surface of teeth is advantageous in that the su~face of teeth
can be,reinforced an improved in appearance.
It is also possible to reinforce teeth by rubbing
the hydroxy-apatite or tetracalcium phosphate-containing
powders, granules, solutions (suspensions) or pastes on the
surfaces thereof, followed by the a~plication of fluoride.
It is particularly preferable to r~b on the paste containing
hydroxy-apatite or tetracalcium phosphate and the calcification-
promoting protein and, thereafter, apply fluoride thereon in the
conventional manner. It i5 also possible to rub the paste
on the surface of teeth and thereafter cover and protect the
site with a polymer. The polymers used to this end may be
selected from polymers so far used as the sealants, such as
EPOXYLIGHT 9070, NUVA-SEAL*, EPOXYLIGHT 9075, ENAMELIGHT ,
* Trade mark
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1327256
DELTON , WHITE SEALANT , P&F SE~LANT , FISSURESEAL , TEETHMATA S '
P~ISMA SHIELD , HELIOSEAL , or polymers used with sustained
release preparations for pharmaceuticals such as shellac,
polyvinyl acetate, polyvinyl butyral, ethyl cellulose, cellu-
lose acetate phthalate, polyvinyl alcohol phthalate, styrene-
acrylic acid copolymers, methyl acrylate-methacrylic acid
copolymers, copolymers of vinyl pyridine or alkyl pyridine
with other vinyl monomers, cellulose acetate diethylaminoacetate,
polyvinyl acetate diethylaminoacetate, polyvinyl aminoacetal,
polyvinyl alcohol derivatives, amino cellulose derivatives,
dimethylaminoethyl methacrylate-methyl methacrylate copolymers
and copolymers of vinyl pyridine or alkylvinyl p~dine with
acrylic acid. These polymers may be applied to the site in the
conventional manner. The hydroxy-apatite or tetracalcium
phosphate and adjuvants rubbed in place by this coating are
retained on the surface of the teeth over an extended period
of time without being dislodged, and are efficiently recalci-
fied. The hydroxy-apatite or tetrcicalcium phosphate and
calcification-promoting protein-containing paste may be added
with, e, g., pharmaceutically active components such as an
abrasive selected from calcium carbonate, calcium hydrogen
phosphate, aluminum hydroxide, silicic anhydride and other
abrasives; a humectant such as glycerin, sorbitol and propylene
glycol; a foaming agent such as sodium lauryl sulfate and soap
powders; a binder such as carboxymethylcellulose and carrageenan;
a perfume; a sweetener, a preservative; and a halitosis remover
and tooth detinter. To use this system in a manner similar
* Trade mark
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to a dentifrice provides a usable procedure which makes it
possible to remove pla~ue simultaneously with rubbing of the
hydroxy-apatite or tetracalcium phosphate and calcification-
promoting protein on to the surface of teeth.
Thus, there is provided a method for remedying the
decalcification that is the incipient state of caries, which
method makes use o~ the properties of the adjuvant-containing
or free hydroxy-apatite, which is the same component as tooth,
or tetracalcium phosphate bonding selectively and ~irmly to
the pits and fissures or decalcified lesions, and in which
the hydroxy-apatite or tetracalcium phosphate is rubbed on
the surface of teeth with or without adjuvants to protect
the surface of the teeth or cover the decalcified lesions
for the purpose of taking advantage of spontaneous healing
power obtained through recalcification by saliva. There is
also provlded a filler used in the above-described method.
The tooth-reinforcing and caries-preventing method and filler,
which were not available until nejw, do not re~uire any special
technical skill and have considerable technical advantages
over the conventional fluoride coating and sealant methods.
Other features and advantages of the present invention
will be apparent from the following description.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention will now be described in detail
~5 with reference to a number of examples.
Example 1
Fifty (5~) g of hydroxy-apatite finely divided to
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10 microns or less to which 50 ml of water was added was
treated in a chaser mill to obtain a paste. Shortly after
the teeth were brushed with a dentifrice followed by rinsing,
the paste was carefully rubbed on the surface of the teeth
with a fingertip for 3 min. Afterwards, excess paste was
removed from within the mouth by light rinsing. This procedure
was carried out whenever teeth were brushed.
Example 2
Fifty (50) g of hydroxy-apatite finely divided to
10 microns or less to which 50 ml of an aqueous solution
containing 500 ppm of sodium fluoride was added was treated
in a chaser mill to obtain a paste. At the completion of
ordinary brushing, teeth were brushed for 3 min with a toothbrush
to which paste was applied. This was followed by light rinsing.
This brushing was always carried out after ordinary brushing.
Example 3
Fifty (50) g of hydroxy-apatite finely divided to
10 microns or less to which 50 ml of water containing 0.01 mg
of casein was added was treated in a chaser mill to obtain
a paste. At the completion of ord~inary brushing~ the paste
was carefully rubbed on the surface of the teeth with a
fingertip for 3 min. This procedure was carried out whenever
teeth were brushed.
Example 4
In a manner similar to that described in Example 3,
the paste was rubbed on the surface of teeth and excess paste
within the mouth was then washed away by rinsing. Following
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drying, a Nuva-Seal liquid was thinly applied to the surface of
! ~t ` the teeth and was hardened by an ultraviolet lamp for sealing
purposes.
Example 5
In a manner similar to that described in Example 3,
the paste was rubbed on the surface of teeth and excess paste
within the mouth was then washed away by rinsing. Diamine
silver fluoride was applied in the conventlonal manner.
Example 6
Four (4) g of hydroxy-apatite finely divided to 10
microns or less and 0.04 mg of casein were added to and mixed
sufficiently with 100 ml of vinyl acetate to prepare a homo-
geneous dispersion. After ordinary brushing, the teeth were
dried with warm air and then uniformly coated with the dispersion
by means of a brush. Drying gave a glossy, white and fine
coating on the surface of the teeth.
Example 7
Fifty ~50~ g of tetracalcium phosphate finely divided
to lO microns or less to which 50 ml of water was added was
treated in a chaser mill to obtain a paste. Shortly after
teeth were brushed with a dentifrice followed by thorough
rinsing, the paate was carefully rubbed on the surface of the
teeth with a fingertip for 3 min. Afterwards, excess paste was
removed from within the mouth by light rinsing. This procedure
was carried out whenever teeth were brushed.
Example 8
Fifty (50) g of tetracalcium phosphate finely divided
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to 10 microns or less to which 50 ml of an aqueous solution con
taining 500 ppm of sodium fluoride was added was treated in
a chaser mill to obtain a paste. At the completion of ordinary
brushing, teeth were brushed for 3 min with a toothbrush to which
the paste was applied. This was followed by light rinsing.
This brushing was always carried out after ordinary brushingO
Example 9
Fifty (50~ g of tetracalcium phosphate finely divided
to 10 microns or less to which 50 ml of water containing
0.01 mg of casein was added was treated in a chaser mill to
obtain a paste. At the completion of ordinary brushing, the
paste was carefully rubbed on the surface of the teeth with
a fingertip for 3 min. This procedure was carried out whenever
teeth were brushed.
Example 10
In a manner similar to that described in Example 3, the
paste was rubbed on the surface of teeth and excess paste
within the mouth was then washed away by rinsing. Following
drying, a Nuva-Seal liquid was th~nly applied to the surface
of the teeth and was hardened by an ultraviolet lamp for
sealing purposes.
Example 11
Four (4) g of tetracalcium phosphate finely divided
to 10 microns of less and 0.04 mg of casein were added to and
mixed sufficiently with 100 ml of vinyl acetate to prepare
a homogeneous dispersion. After ordinary brushing, the teeth
were dried with warm air and then uniformly coated with the
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dispersion by means of a brush. Drying gave a glossy, white
and fine coating on the surface of the teeth.
Reference Examples
In order to measure the amount of hydroxy-apatite
bonded to the surface of a tooth, the following in vitro tests
were conduted:
(A) Synthesis of hydroxy-apatite and brassid
One hundred (100) ml of a 0.1 M CaC12 solution ~containing
CaC12 manufactured by Aeroham) was slowly added dropwise,
under agitation, to 100 to 200 ml of 0.lM Na2HPO4 solutions
to synthesize hydroxy-apatite in the conventional manner.
On the other hand, a 0.1M 45CaC12 solution was similarly added
dropwise to 100 to 200 ml of 0.01 NaH2PO4 solutions to prepare
brassid. After preparation, the hydroxy-apatite and brassid
were preserved in the corresponding 0.1 M Na2HPO4 and 0.1 M
NaH2PO4 solutions. For use, they were resuspended in 0.01 M
phosphoric acid buffers of the corresponding pH.
(B) Preparation of artificial tooth
The hydroxy-apatite was molded into a disc which was
1 cm in diameter and 3 mm in thickness, and the disc was
sintered to form a hydroxy-apatite tablet, the surface of which
was evenly abraded with No. 600 sand paper. Afterwards, the
tablet was brushed to carefully remove powders, while distilled
water flowed thereover, thereby making an artificial tooth.
tC) An acryl tank which was 12 cm in length, 4 cm in
width and 10 mm in depth was provided in its bottom with five
blind holes for the fixation of hydroxy-apatite tablets, each
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of which was 1 cm in diameter and 2 mm in depth. Five hydroxy-apatite
tables were fixed in the blind holes and 5 ml of a hydroxy-
apatite or brassid suspension was added to immerse the tablets.
The upper surface of the tablets was abraded at 1 rpm. Upon
elapse of a certain time, the tablets were removed and, soon
thereafter, washed by dropwise addition of a large amount
of distilled water. Two (2) ml of a PSC cocktail was added to
the tablets to measure the radioactivity of the tablets with a
liquid scintillation counter.
(D) Results
As the results of tests performed at pH 9.0 and 5.0
that were the stable pH of hydroxy-apatite and brassid, re-
spectively, the amount of hydroxy-apatite bonded to the tablets
was 5 micrograms after 5 min. Thereafter, this increased
gradually and reached 164 micrograms after 40 min, as calculated
from 5.4 x 105 CPM/mg and 8.9 x 105 CPM~mg that where the specific
radioactivities of the hydroxy-apatite and brassid used, re-
spectively. Thls bonded amount was much larger than that
of brassid by a factor of 20 after 5 min and 109 after 40 min.
From the results of tests performed at pH 5.5, 6.8,
7.4 and 8.5, where rubbing was carried out at the same pH,
it was also found that the bonding force of hydroxy-apatite
to the tablets was markedly increased.
These results are tabulated below.
pH Condition 'B
Aftar 10 min After 60 min
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A: pH 9, B: pH 5 32.8 201.7
A, B pH 8.5 2~0 5.4
" pH 7.4 6.6 5.4
" pH 6.8 2.3 6.4
" pH 5.5 11.2 8.4
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A: hydroxy-apatite; B: brassid
Figures represent the amounts in we:Lght ratio
of hydroxy-apatite and tetracalcium phosphate
bonded to the tablets.
These results reveal that hydroxy-apatite is selectively
bonded to the surface of teeth.
Thus, according to the method of the present invention,
a fine filler containing hydroxy-apatite that is a biomaterial
firmly bonding to the pits and fissures or minute decalcified
lesions in the surfaces of teeth or tetracalcium phosphate
with or without adjuvants is rubbed on the surface of teeth,
optionally followed by covering the thus rubbed site with a
polymer, to cover the pits and fissures or decalcified lesions
with~the fine filler, so that spontaneous healing power is
augmented under the action of saliva or the adjuvants for
the restoration of the decalcified lesions. This method
exhibits excellent effects merely by rubbing the fine filler
` on the surface of teeth. Slnce hydroxy-apatite or tetracalcium
phosphate is the most ideal calcium substance, it is harmless
if swallowed and the filler can ~e used without fear of harmful
effects. No special clinical skill is re~uired to carry out
this method. Accordingly, the method of the invention is
advantageous in that it can easily be carried out by the
patient himself.
The present method in which caries is suppressed
in its incipient stage by making use of, and augmenting,
spontaneous healing power obtained through recalcification by
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saliva is the most effective means for preventing caries that
is not found in the prior art. The present invention is
also applicable to the treatment of paresthesia and pyrrhoea
alveolaris.
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