Note: Descriptions are shown in the official language in which they were submitted.
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ROOT CANAL FIL.LER FOR DENTAL USE
BACKGROUND OF THE INVENTION
Field of the Invention
This invention concerns a root canal filling material
for dental useO
Description of the Prior Art
So-called powder/liquid type dental compositions
using powdery agents and liquid agents have been applied
as various kind of products in many application fields
such as, for examples, tooth reconstructing material, pulp
capping material, root canal filling material and various
kinds of dental cements (for joining, filling, capping,
lining, backing, etc.).
While these materials are mainly composed Or inorganic
or synthetic resin type materials as the main ingredient,
there has been a problem that they show deleterious effects
on biobodies. That is, conventional dental compositions
are more or less stimulative to biobodies and, since they
are made Or materials different from those of the biobody,
their biocompatibility is poor.
Thus, there has been a difficulty in using conventional
dental compositions as root canal filling material because
Or their stimula-ting nature to the biobody and, accordingly t
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it has been desired for the development of such root canal filling
material for dental use that has no stimulating nature and can
be hardened firmly in a relatively short pexiod of time with an
appropriate time margin for the operation.
SU~D~ARY OF THE INVENTION
The object of this invention is to provide root
canal filling material for dental use that can be hardened to an
adequate strength in a relatively short period of time with an
appropriate time margin for the operation, while giving no
stimulations and securing biocompatibility.
This invention provides a root canal filling material
for dental use, comprising:
(A) a powdery agent consisting essentially of (i) from
10 to 90% by weight (based on the powdery agent) of alpha
tricalcium phosphate (~-Ca3(PO4)2), (ii) from 9 to 70% by weight
lbased on the powdery agent) of hydroxyapatite and (iii) from 1
to 35% by weight (based on the powdery agent~ of a combination of
an X-ray contrast medium and a pharmaceutical agent, and
~B) a liquid agent consisting essentially of (i)
from 10 to 40% by weight (based on the liquid agent) of a homo~
polymer of acrylic acid or a copolymer thereof with another
unsaturated carboxylic acid copolymerizable with acrylic acid,
(ii) from 35 to 88.5% by weight (based on the liquid agent) of
purified water, (iii) from 1 to 15% by weight of an organic or
inorganic non-toxic acid and (iv) from 0.5 to 10% by weight (based
on the liquid agent) of at least one member selected from the
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group consisting of [a] water-soluble calcium, aluminum, sodium
or magnesium salts, [b] surface active agentsl [c~ p~ controllers
and [d] viscosity improvers, wherein the liquid agent is capable
of reacting with the said powdery agent and forming a coagulated
hardened product in an oral circumstance.
~ powdery agent including ~-TCP (~-Ca3(PO4)2):
alpha type tricalcium phosphate), hydroxyapatite, an X-ray con-
trast medium and a pharmaceutical agent is kneaded with a poly-
acrylic acid type liquid agent capable of reacting with the
powdery agent in an oral circumstance to form a coagulated
hardened product.
The most prominent feature of this invention is
to us~ ~-TCP as an ingredient of the powdery agent.
~s has been well-known, the main constituent ingre-
dient for inorganic components such as too-th and bone is
HAP (Cal0(PO4)6(OH)2 : hydroxyapatite) and inorganic biomaterails
similar thereto have been noted in recent years.
Such inorganic biomaterials are favorable because oE
their compatibility with biobody tissues such as induction of
formation and binding of newly formed bones at the interface with
hard tissues in addition to their in-vivo stability. They are
classified into bioinert materials such as A12O3 and bioactive
materials such as HAP depending on the activity with the biobody
tissue interface. ~-TCP used in this invention is a HAP precur-
sor having a feature of biodegradability like that of low crystal-
line HAP, but it is a biocompatible inorganic material which
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has chemical activity as well and can be expected to be con-
verted into HAP in the presence of water. The ~-TCP can be
converted into a firm coagulated hardened product in a short
period of time withi.n an oral cavity when kneaded with a poly-
acrylic acid type liquid agent. It is widely known that the
polyacrylic type copolymer has generally been used as the
liquid ingredient for dental cement compositions.
While biocompatible inorganic materials include HAP,
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~-TCP and the like in addition to ~ -TCP used in this
invention, but both of HAP and ~-TCP are poor in the
chemical activity and di~icult to be hardened ln the oral
circumstance. C~-TCP is used as the ingredient in -this
sense and a novel root canal filling material not found in
the prior art can be obtained by blending~-TCP with HAP
into and adequate composition.
By using a polyacrylic acid type aqueous solution as
the liquid agent, it is possible to provide a kneaded
slurry with an appropriate viscosity and attain firm har-
dening in an oral circumstance in a relatively short
period of time while giving an appropriate time margin for
the operation.
Root canal filling material is used for supplementing
and~illing material defect of pulp cavities formed after
the pulpectomic operation or therapy for infected root
canal. The root canal therapy is completed after the
canal has been filled exactly.
The object of the root canal therapy is to completely
close the space in the root canal, e.g., for interrupting
the route of infection between the root canal and the
peridental tissues, between the root canal and the oral
cavity and the like and protecting the wound at the apical
portion to form granulat,ion tissues to heal bone scars,
thereby preserving pulpless tooth in the state not delete-
rious to human body and maintaining -the function of the
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69065~23
tooth.
While Ca(OH)2 type root canal filling materials
have exclusively been used in this field, their primary
object resides in obtaining therapeutic ef-Eects and most o~
them are not hardenable. Further, conventional root canal
filling materials are filled to the root canal together with
gutta-percha, but this operation is troublesome~
Accordingly, the root canal filling material for
dental use according to this invention is an extremely
advantageous material that can complete airtigh-t canal fill-
ing by the operation for once, and can be coagulated ~irmly
to harden in a short period of time in the root canal with an
appropriat~ time margin for the operation. It is of course
possible to use the material in combination with conventional
solid material.
The root canal filling material according to this
invention is prepared from the powdery agent and the liquid
agent shown in Table-l.
Explanation is at first made to the powdery agent.
The powdery agent comprises ~-TCP, HAP, X-ray contrast media
and a pharmaceutical agent.
~-TCP is contained in the powdery agent by from
10 to 90 %, pre~erably 15 to 40 % by weight based on the
powdery agent. If ~-TCP is less than 10 %, biocompatibility
is reduced to increase the hardening time and, in addition,
coagulation does not proceed completely.
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69065-23
While on the other hand, if ~-TCP is more than 90%,
it is difficult to obtain an appropriate time margin for the
operation since the hardening reaction proceeds too rapidly ancl
the strength of the coagulated hardened product becomes exces~
sively high in view of the physical properties, although it is
advantageous in view o~ the biocompatibility.
It is sufficient that the root canal filling
material can fill the space in the root canal and, if the
strength upon hardening is too high, it can not be taken out
upon re-operation.
Then, ~AP is used primarily for the improvement
of the biocompatibility and also for adjusting (retarding) the
reaction of ~-TCP and polyacrylic acid and adjusting (lowering)
the strength o the coagulated hardened product. HAP is con-
tained in the powdery agent by from 9 to 70 %, preferably 20 to
55 % by weight based on the powdery agent, depending on the
content of ~-TCP. If HAP is less than 9 %, the foregoing object
can not be attained and, particularly, the strength of the
powdery agent becomes excessive failing to impro~e the biocom-
patibility. While on the other hand, if HAP is more than 70 %,
it is difficult to react the coagulated hardened product with
the liquid agent in a short period of time although the bio-
compatibility is impro~ed.
Substances that can be used as the X-ray contrast
medium and/or pharmaceutical agent include iodoform, barium
sulfate, tantalum powder, silver powder, bismuth subcarbonate
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(i.e., bismus oxycarbonate (BiO)2CO3), various salts of chloro-
hexidine, calcium fluoride and sodium monofluoro phosphate.
Among them, iodoform is most appropriate, which has -the func-
tions both of X-ray contrast medium and antibacterial effect.
Although barium phosphate can be used as an X-ray contrast
medium, it is necessary to additionally use another ingredient,
for e~ample, chlorohexidine hydrochloride as an antibacterial
agent. Sodium monofluoro phosphate can be used as the pharmaceu-
tical agent.
The total amount of the X-ray contrast medium
and the pharmaceutical agent in the powdery agent is from 1 to
35 %, preferably 10 to 35 % by weight, depending on the con-
dition of use.
If the amount of the X-ray contrast medium and
the pharmaceutical agent is less than 1 %, X-ray impermeabil-
ity becomes poor making it difficult to check the filled state
in the root canal after application, as well as it is no more
possible to maintain the aseptic state in the root canal after
the therapy. Image pick-up is impossible and bacterial
infection is caused. Further, if the amount of the X-ray
contrast media antibacterial agent or pharmaceutical agent
is increased more than 30 %, no other effects than their
inherent function can be attained and, in addition, the con-
tent of ~-TCP is relatively decreased undesirably.
Explanation will then be made to the polyacrylic
acid type liquid agent referring to Table-l.
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The liquid agent includes an acrylic acid polymer,
purified water, an organic acid or inorganic acid, as well as
one or more other ingredients that are conventionally used in a
root canal filling material.
The acrylic acid polymer may be a homopolymer of
acrylic acid or a copolymer of acrylic acid and another unsaturated
carboxylic acid copolymerizable with acryli~ acid, such as
itaconic acid, fumaric acid and maleic acid.
The acrylic acid polymer is contained in the liquid
agent in an amount of from 10 to 40 %. If the acrylic acid
polymer is less than 10 %, hardening reaction with the powdery
agent does not proceed sufficiently. While on the other hand, if
it is more than 40 ~, ~iscosity of the liquid agent is increased
and the kneaded slurry becomes too hard thereby reducing the
operationability and bringing about a difficulty of use upon
filling the root canal.
If purified water is less than 35 %, the viscosity
Qf the kneaded slurry becomes too high bringing about a diffi-
culty in use, and conversion of ~-TCP into HAP can no more be
expected. Whereas, if the purified water is more than 88.5 %
the viscosity is too low bringing abcut a difficulty in use.
Organic acid or inorganic acid includes mainly
monobasic or polybasic carboxylic acids such as glycolic acid,
lactic acid, citric acid, acetic acid and tartaric acid, or
inorganic acids such as phosphoric acid, hydrochloric acid and
nitric acid and they are contained by from 1 to 15 ~ in the
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liquid agent. They are used for adjusting the hardening time,
sharpness for the hardening and the strength upon hardening.
The sharpness of the hardening means the rate of rising speed
of rapid hardening of the kneading slurry from the powdery agent
and the liquid agent after the elapse of a predetermined time
margin for the operation.
If the organic acid or inorganic acid is less than
1 %, the foregoing object can not be attained. While on the
other hand, if it is more than 15 %, the time margin for the
operation becomes extremely shortened making it impossible for
sufficient kneading and, as a result, the hardened product can
not completely be converted into a coagulated state thereby
tending to cause embrittline destruction or the like.
Other ingredients that can be included in the
liquid agent are for example water soluble calcium salt,
aluminum salt, sodium salt or magnesium salts; sur~ace active
agents such as cationic surface active agent, anionic surface
active agent and nonionic surface active agent, pH controllers
such as sodium hydroxide and potassium hydroxide; and viscosity
improvers such as carboxymethylcellulose, hydroxypropyl-
cellulose, polyoxyethylene high polymer, polyethylene glycol
and water soluble silicon, and they are contained in an amount
of from 0.5 to 10 ~ of the liquid agentu As the water soluble
calcium salt, phosphate is preferable and, for example, calcium
dihydrogenphosphate monohydrate is used for adjusting the
hardening time, sharpness of the hardening and the mechanical
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strength. The surface acti~e agent is used for securing the
wettability of the kneading slurry, the pH controller is used
for adjusting the pH value and the viscosity improver is used for
adjusting the viscosity.
In any of the cases, the amount o~ each of the
ingredients in the powdery agent and the amount of each of the
ingredients in the liquid agent may properly be adjusted depend-
ing on the purpose. The powder/liquid weight ratio is preferably
2:1 to 1:2, more preferably about 1:1. The powdery agent and
the liquid agent are normally separated from each other until
shortly before use.
Example
Table 2 shows examples for root canal filling mate-
rials.
In Example 1, the powder/liquid ratio is 1.0, the
hardening time is 45 minutes, and the compression strength is
75 kg/f/cm2. In Example 2, the powder/liquid ratio is 1.0, the
hardening time is 35 minutes and the compression strength is
93 kg/f/cm2. In Example 3, the powderlliquid ratio is 1.0, the
hardening time is 60 minutes and the compression strength is
88 kgf/cm2.
In Examples 1, 2 and 3, hardening time is appropriate
as the time margin for the handling of root canal ~illing
materials, to obtain adequate compression strength.
In the actual use of the root canal ~illing material,
the powdery agent and the polyacrylic type liquid agent are
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kneaded at a predetermined powder/liquid ratio, for example,
1.0 into a slurry to provide an appropriate
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viscosity. Then, when the kneaded slurry i9 filled, for
example, to the root canal after the pulpectomic operation,
coagulated hardened product of an adequate compression
strength is obtained after the elapse Or a predetermined
of hardening time.
Since the coagulated hardened product contains ~ -TCP
and HAP, it is biocompatible and causes no stimulations.
By the way, the polyacrylic acid type liquid agent is
used in this invention. It has been found tha-t if the
lactic polymer type liquid agent were used instead of the
polyacrylic acid type agent, the compression strength of
the coagulated hardened product would be lowered and the
hardening time be increased and, accordingly, the lactic
polymer type liquid agent is not suitable to such a use.
As is apparent from the foregoings, the root canal
filling material according to this invention can be har-
dened to an adequate strength in a relatively short period
of time with an appropriate time margin for the operation
in an oral circumstance when used as a root canal filling
material, while giving no stimulating nature to a biobody
and securing biocompatibility~
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Table 1
. _
Ingredient ratio(~)
_ _ _ .
Powdery ~ -TCp 10 - 90
agent (~ -Ca3(PO4) 2~ alpha type tricalcium
phosphate)
HAP _
(Cal0(P4)6(OH)2~ hydroxyapatite) 9 - 70
X-ray contrast media, antibacterial agent
or pharmaceutical agent
Ebarium sulfate(BaSO4), iodoform(CHI3)] 1 - 35
. .
liquid acrylic acid polymer l0 - 40
agent (copolymer of acrylic acid and itacor.ic acid)
(copolymer of acrylic acid and fumaric acid) .
(copolymer of acrylic acid and maleic acid) .
_~
purified water 35 - 88.5
_
organic or inorganic acid 1 - 15
Etartaric acid, glycolic acid, phosphoric
acid, hydrochloric acid, nitric acid] _ ¦
other ingredient
Ewater-soluble calcium salt, surface active o.S - 10
agent, pH conroller, viscosity improverl
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Table 2
Exa- powdery agent liquid agent powder/ hardening compres-
mple liquid time[min] sion
ratio strength
[kgf/cm2 ~ _
1 ~-TCP 25% acrylic acid
HAP 45% polymer 23
iodoform 30% purified
water 72%
glycolic
acid 3.0% 1.0 45 75
cationic surface
active agent 0.4
sodium
__ hydroxide 1.6%
2 ~-TCP 30% acrylic acid
HAP 39% polymer 25.0%
barium purified
sulfate 14.9% water 69.9~ 1.0 35 93
sodium mono- phosphoric
fluoro phos- acid 2.7%
phate 0.4~ cationic
bismuth surface
subcarbonate active agent
15.0~ 0.4%
chlorohexi- polyethylene
dine hydro~ glycol 2.0%
chloride 0~7% _
: _ _
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Exa- powdery agent liquid agent powder/ hardening compres-
mple liquid time[min] sion
ratio strength
_ : [kgf/cm
3 C~TCP 20% acrylic acid 1.0 60 88
HAP 45% polymer 25.0~
iodoform 35~ purified water
2.4%
hydroxypropyl-
cellulose 1.3%
sodium hydroger
. . phosphate 2.3%1 . .
14 -
,~ ~,.. .
