CA1158078A - Artificial dental root - Google Patents
Artificial dental rootInfo
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- CA1158078A CA1158078A CA000336458A CA336458A CA1158078A CA 1158078 A CA1158078 A CA 1158078A CA 000336458 A CA000336458 A CA 000336458A CA 336458 A CA336458 A CA 336458A CA 1158078 A CA1158078 A CA 1158078A
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- hydroxyapatite
- phase
- organic matrix
- bone
- dental root
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Abstract
ARTIFICIAL DENTAL ROOT
ABSTRACT OF THE DISCLOSURE
An artificial dental root comprised of a particulate or powdered form of synthetic hydroxyapatite or calcined or sintered synthetic hydroxyapatite or a mixture thereof and an organic matrix, the surface area of said artificial dental root to be brought into contact with a bone being composed of both a phase of said hydroxyapatite and a phase of said organic matrix. The artificial dental root is prepared by blending said hydroxyapatite with said organic matrix and molding the blend. The artificial dental root has moderate affinity for a bone and high mechanical strength.
ABSTRACT OF THE DISCLOSURE
An artificial dental root comprised of a particulate or powdered form of synthetic hydroxyapatite or calcined or sintered synthetic hydroxyapatite or a mixture thereof and an organic matrix, the surface area of said artificial dental root to be brought into contact with a bone being composed of both a phase of said hydroxyapatite and a phase of said organic matrix. The artificial dental root is prepared by blending said hydroxyapatite with said organic matrix and molding the blend. The artificial dental root has moderate affinity for a bone and high mechanical strength.
Description
807 ~
ARTIFICIAL DENTAL ROOT
BACKGROUND OF THE INVENTION
(1) Field o~ the Invention The invention relates to an artificial den~al root comprised of synthetic hydroxyapatite or calcined or S sintered synthetic hydroxyapatite or a mixture thereof (hereinafter, referred to as hydroxyapatite) and an organic matrix. More particula~ly, the invention relates to an artificial dental root obtained by blending hydroxyapatite with an organic polymerizable binder or organic binding polymeric material (her~inafter, referred to as an organic matrix) and molding the blend.
ARTIFICIAL DENTAL ROOT
BACKGROUND OF THE INVENTION
(1) Field o~ the Invention The invention relates to an artificial den~al root comprised of synthetic hydroxyapatite or calcined or S sintered synthetic hydroxyapatite or a mixture thereof (hereinafter, referred to as hydroxyapatite) and an organic matrix. More particula~ly, the invention relates to an artificial dental root obtained by blending hydroxyapatite with an organic polymerizable binder or organic binding polymeric material (her~inafter, referred to as an organic matrix) and molding the blend.
(2) Description of Prior Art Artificial dentures include artificLa1 tooth crowns and dens succedaneuses for the prosthesis of res-pective damaged tooth crowns as well as bridgework for theprosthesis in the case where one or more teeth are lost.
The bridgework technique utilizes an artificial denture provided with one or two bridges for supporting it to the normal tooth or teeth. However, the bridgework technique has a drawback in that, since the~ridgework is placed on the oral mucosa merely supported by the bridges, it has insufficient retention-abillty and, thus, is greatly inferior in the performance~of mastication as compared to a natural tooth. This technique has another drawback in that the natural tooth~used for support :is hurt. Therefore, in order to eliminate the drawbacks, implant dentures have :
~S8078 recently been developed, in which the lower co-nstruction of a denture is implanted into a vital -tissue wi-thin the jaw bone, under the perios~eum or wi~hin the mucous membrane to form an abutment, i.e. an artificial dental root, and the upper structure of the denture is connected to the abutment.
As the materials fo.r such artiicial dental roots, there have hitherto been utilized metallic substances such as cobalt-chrome alloy, titanium and tantalum, ceramic materials such as porous alumina ceramics, as well as glass-like carbon and a composite material consisting of polymethyl methacrylate and bone minerals incorporated into the polymethyl methacrylate. However, these materials have drawbacks with respect to toxicity to vital tissue, affinity for a bone, impediment to a bone formation, durability, mechanical strength and the like and, thus, may not provide satisfactory results.
On the other hand, recently, bioceramics based on apatite substances have increasingly become of great interest, as they may be absorbed into body and replaced by a new bone which is a host and, thus, exhibit good affinity for vital tissue. However, the apatitè sub-stances have a drawback in that they are inferior in mechanîcal strength, particularly in impact resistance.
Accordingly, studies for the utilization of the apatite substances as implant materials have been directed to the improving the mechanical strength of the ~patltie substances while maintaining the excellent affinity for a bone. For 11~8~78 example, laid-open Japanese Patent Application (Kokai) No.
53-75209 discloses an implant material having a layer of a flame sprayed apatite powder formed on~o ~he periphery of a ceramic core. The flame sprayed layer of this implant material has a rough sur ace and the implant material can be firmly fixed to a bone by the anchor effect owiny to the growth of the bone tissue in the rough area. Therefore, this implant material may provide an excellent artificial dental root, having mechanical strength improved by the rein~orcement of the ceramic material and having good affinity for a bone.
However, in the practical use of artificial dental roots, it should be taken into consideration that it becomes necessary to extract the artificial dental root once implanted when any trouble has occurred. Thus, the above-mentioned implant material may not be suitable for practical use as an artificial dental root since it may have too high an affinity for a bone. In the implant denture technique, an artificial dental root is implanted into the jaw bone or the like and then, after two or three months, a denture is connected onto the implanted dental root. If trouble, such as the displacement or damage of the implanted root, the inflammation of the peripheral tissue or the like, occurs after the implantation of the root, it is necessary to immediately extract the implanted root. In such a case, if the artificial dental root has been extremely firmly fixed to a natural bone such as the jaw bone, a part of the bone may have to be~ resected to ~ 1~8078 extract the implant-ed rootr so that the patient may ex-perience pain or the natural bone may be damaged.
SUMMAR'~ O:F THE INVENTION
The primary object of the prPsent invention is to provide an artificial dental root which does not have the above-mentioned drowbakcs.
Thus, according to the present invention, there is provided an artificial dental root comprised of a composition in which a particulate or powdered form of synthetic hydroxyapatite or calcined or sintered synthetic hydroxy-apatite or a mixture thereof is dispersed in an organic matrix, the surface area of said synthetic dental root to be brought into contact with a bone being composed of both a phase of said hydroxyapatite and a phase of said organic matrix.
It has now been found that if a composite material obtained by molding a blend of a particulate or powdered form of hydroxyapatite oE a specific particle diameter with an organic matrix has a specific area ratio of the hydroxyapatit phase to the organic matrix phase of the surface area to be brought into contact with a bone, the composite material has not only excellent mechanical properties but also moderate ability to coapt with a natural bone.
The term "moderate ability to coapt wi-th a natural bone", as used herein, is intended to mean that the implanted artificial dental root is fixed to the nat~ural bone with a moderate coaptation force which is sufficient to prevent 1 1~8078 the implanted root from being removed Erom ~he vital tissue in a normal state and to ~ithstand the practical use of the resultant denture aEter the connection of the upper structure to the implanted root, but allows the extractio.n of the implanted root without damaging the natural bone when any problems may occur.
DESCRIPTION OF PREFERRED EMBODIMENTS
Hydroxyapatite usable for ~he present invention may be prepared by Xnown processes. Thus, there may ba employed synthetic hydroxyapatite prepared, for example, as desc.ibed in Ceramics, 10, 7, 461(1975), by a dry process wherein Ca3(PO~)2 is reacted with excessive CaCO3 in a steam--containing air flow at a high temperature of 900 to 1300C or by a wet process wh~rein an aqueous solution of Ca(NO3)2 is reacted with an aqueous solution of (NI-I4)H2PO4 under a NH40H alkaline condition. There may also be employed sintered hydroxyapatite obtained by sintering the above-mentioned synthetic hydroxyapatite as well as siniered hydroxyapatite obtained by press molding synthetic hydroxy-apatite prepared by a known process and sintering themolded product at 600 to 1500C.
Hydroxyapatite can also be obtained from a natural bone, for example, by calcining a cattle bone at about 800C to remove the organic substances contained therein.
However, where such hydroxyapatite is employed, there may arise problems with respect to the procurement of the starting material, uniformity in quality and the com-patibility to a living body or the bone formation speed 07~
owing to the presence of retained impurities.
The organic matrix should not deteriorate in a living body and should not deleteriously affect the vital tissue. Preferably, the organic matrix is comprised of one or more polymers selected from bisphenol A-glycidyl methacrylate polycondensates, polymethyl methacrylate, poly-2-hydroxyethyl methacrylate, polyethylene, polysulfones, polyamides, polyesters, polytetra1uoroethylene, poly-vinylidene fluoride and polycarbonates, and copolymers or two or more monomers of said polymers.
The artificial dental root of the present invention may be prepared by blending a particulate or powdered from of hydroxyapatite as mentioned above with an organic matrîx and molding the blend in a known manner. It is lS preerable that the hydroxyapatite has a particle diameter of not more than 1000 ~m, particularly 100 to 0.01~m. It is important that the hydroxyapatite phase is in~a dis-continuous phase in the surface area of the resultant artiicial dental root to be brought into contact with a bone. The area ratio of the hydroxyapatite phase to the organic matrix phase of the surface area to be brought into contact with a bone may preferably be 5:95 to 70.30, particularly 10:90 to 60:40. If the hydroxyapatite phase is in a continuous phase or occupies more than 70~ of the surface area, the coaptation force of the resultant dental , .
root with a natural bone may become too large so that the natural bone is damaged at the time of the extraction of the implanted dental root. On the other handj if the : :
1 15~078 hydroxyapati-te phase occupies less than 5g6 of the surface area, the implanted dental root may be re~loved from the vital tissue in a normal state. It may be advantageous, from the stand point of durability and coaptability to the vital tissue, that the area ratio of the hydroxyapatite phase to the organic matrix phase be in a range from lO:90 to 60:~0.
It will be appreciated from the above description that the characteristic Eeature of the present invention consists in the fact that the excellent ability of hydroxy-apatite to coapt with a bone is advantageously controlled in the use of hydroxyapatite as material for an artificial dental root. Thus, the composite material described above with regard to the artificial dental root according to the present invention may not be suitable for use as a dental cement such as a sealant or filler for a bore or crack in a tooth, but is~very useful for a practical artificial dental root.
The present invention will be further illustrated by the following non-limitative examples.
Exam~el 1 A mixture~(pH ll to 12) of 158.5 g (1.2 mols) of diammonium hydrogenphosphate, 3780 ml of di~stilled water and 1420 ml of concentrated ammonia was added dropwl~se to a stirred mixture of 328 g~(2 mols) of calcium nitrate, 1320 ml of distilled water and 1180 ml of ooncentrated ammonia over the ccurse of 30 minutes. The obtained suspension was centrifuged to obtaln a cake. The cake was :
~.
I 15~07~
dried at 100C ~or 24 hours. The~, a part of the dried cake was heated at 500C for 3 hours in an electric furnace to obtain a hydroxyapatite powder and the remainder was sintered at 1250C for 60 minutes to obtain a white sintered hydroxyapatite.
The elmentary analysis of the non-~intered and sintered hydroxyapatites proved that they had a Ca/P ratio of 1.66 and the ~-ray diffraction thereof also proved that they were of high purity~
The hydroxyapatites obtained as mentioned above were ground and used as the starting material in the following examples.
Example 2 A sintered hydroxyapatite powder having particle diameters of lO to 70 ~m was mixed with a bisphenol A--glycidyl methacrylate/methyl methacrylate mixture (weight ratio 6/4) at a volume ratlo (calcuIated by speclfic gravity) of I:l. After addition of 0.05% by weight of benzoyl peroxide as a polymerization initiator, the mixture was uniormly blended using a stirrer. Then, the blend was charged into a glass tube having an inner.diameter of 5 mm and, ater defoaming, subj cted to a polymerization :
reaction at a temperature of 80C or 2 hours. Thus, a hydroxyapatite compositlon was obtained ~Sample l).
Example 3 The procedure as described in Example 2 was repeated, except that a sintered hydroxyapatite having particle diameters of 100 to 500 ~m was used and 2-hydroxyet~yl ~158078 methacrylate was used ins-tead of methyl methacrylate.
Thus, a hydroxyapatite composition was obtained (Sample 2).
Example 4 By repeating the procedure as described in Example 2, except that a sintered hydroxyapatite and bisphenol A-glycidyl methacrylate/methyl methacrylate (weiy~lt ratio 6~4) were mix2d at a volume ratio of 3:7, a hydroxyapatite composition was obtained (Sample 3).
Example 5 A sintered hydroxyapatite powder having a mean particle deameter of 20 ~m and a finely divided high-density polyethylene were uniformly blended at a vol~une ratio of , ~ , 1:6 using a Henschel mixer, and the blend was press molded to obtain a hydroxyapatite composition (Sample 4).
Example 6 A slntered 'nydroxyapatite powder having particle diameters of 30 to 70 ~ m and methyl methacrylate were mixed at a volume ratio of 1:1. Then, 0.05% by weight of benzoil peroxide was added as a polymerization initiator 20 and the mixture was uniformly blended. ~he blend was defoamed in a glass tube having an inner diameter of 5 mm and heated at 80C for 2 hours to obtain a hydroxyapatite composition (Sample 5).
Example 7 A sintered hydroxyapatite powder having of particle diameters of 30 to 70 ~m was uniformly blended with a finely divided polysulfone or a finely divided poly-~
tetrafluoroethylene, respectively, at a volume ratio of 1 15~07~
1:3, and the ~lend was press molded. Thus, hydroxyapatite composi-tions were obtained (Sample 6 and Sample 7, res-pectively).
Example 8 A non-sintered hydroxyapatite powder having a mean particle diameter of 50 llm was unifoxmly blended ~ith a finely di~ided 6,6-nylon at a volume ratio of 1:3, and the blend was press molded to obtain a hydroxyapatite composition (Sample 8).
Example 9 (Comparison) ~y repeating the procedure as described in Exampe 2, except that a sintered hydroxyapatite powder and bisphenol A-glycidyl methacrylate/methyl methacrylate (weight ratio 6/4) were mixed at a volume ratio of 3:97, a hydro-xyapatite composition was obtained (Sample 9).
Example 10 (Comparison) By repeating the procedure in Example 2, except that a sintered hydroxyapatite powder and bisphenol A--glycidyl methacrylate/methyl methacrylate (weight:ratio 6/4) was mixed at a volume ratio of 3:1, a hydroxyapatite composition was obtained (Sample 10). ~:
Example 11 (Comparison) A hydroxyapatite composition (Sample;ll) was prepared in the manner as in Example 2, except that a glass tube having an inner diameter of 4 mm was used.
Example 12 (Comparison) A sintered:porous hydroxyapatite having: a porosity of 65~ was impregnated with a mixture of blsphenol A-glycidyl ~: :, . --~
1 ~58078 methacrylate~ ethyl methacrylate (weight ratio 6/4) con-taining 0.05~ by weigh-t of benzoil peroxide under a reduced pressure. The impregna~ed hydroxyapatite was heated at 80C for 2 hours to obtain a hydroxyapatite composition (Sample 12).
The compositions obtained in Examples 2 through 10 and E~ample 12 were each cut to a diameter of 4 mm and a length of 10 mm, while the composition obtained in Example 11 was cut to a length of 10 mm. The cut samples were surgically implanted into a thighbone of an adult dog~
After 6 montbs, the thighbone containing each sample was cut off and each thigh~one piece was subjected to a test for evaluating the coaptation with a bone. The area ratios of the hydroxyapatite phase to the organia matrlx phase of the respective samples determined before the implantation are shown in Table l below together with the reuslts of the above-mentioned coaptation test and the results of an impact stréngth test~
The area ratios were evaluated from the photo-micrographs of the surfaces of the respective sampl~es.~The coaptation test was carried out by placing each thighbone piece on the supporting plate of an Instron tester and slowly loading at a speed of 1 cm/min in the axial dlrection of the implanted sample. :
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1 1~8Q78 It is apparent from the above re~ults that the artifisial dental roo~ o~ the present invention exhibits moderate affinity for bone and has high mechanical strength.
Example 13 Sample 1 and Sample 9 were each cut into two columns having a diameter of 3.5 mm and a length of 10 mm. The columns were implanted into bores drilled in a jaw bone of an adult dog immediately after the extraction of teeth.
The columns~obtained from Sample 9 were both remo~ed in a normal state after one month, while the columns obtained from Sample 1 were retained even after 6 months. One of the Sample 1 column was easily extracted by a usual tooth extraction technique without damaging the jaw bone. The jaw bone containing the other Sample 1 column was cut o~f after one year and subjected to observations by a light microscope and an X-ray photograph. It was proved that the implanted portion was cured and a new bone was formed in the gap between the implanted column and the jaw bone.
Problems, such as inflamation, foreign-body reaction and the like were not at all observed.
The bridgework technique utilizes an artificial denture provided with one or two bridges for supporting it to the normal tooth or teeth. However, the bridgework technique has a drawback in that, since the~ridgework is placed on the oral mucosa merely supported by the bridges, it has insufficient retention-abillty and, thus, is greatly inferior in the performance~of mastication as compared to a natural tooth. This technique has another drawback in that the natural tooth~used for support :is hurt. Therefore, in order to eliminate the drawbacks, implant dentures have :
~S8078 recently been developed, in which the lower co-nstruction of a denture is implanted into a vital -tissue wi-thin the jaw bone, under the perios~eum or wi~hin the mucous membrane to form an abutment, i.e. an artificial dental root, and the upper structure of the denture is connected to the abutment.
As the materials fo.r such artiicial dental roots, there have hitherto been utilized metallic substances such as cobalt-chrome alloy, titanium and tantalum, ceramic materials such as porous alumina ceramics, as well as glass-like carbon and a composite material consisting of polymethyl methacrylate and bone minerals incorporated into the polymethyl methacrylate. However, these materials have drawbacks with respect to toxicity to vital tissue, affinity for a bone, impediment to a bone formation, durability, mechanical strength and the like and, thus, may not provide satisfactory results.
On the other hand, recently, bioceramics based on apatite substances have increasingly become of great interest, as they may be absorbed into body and replaced by a new bone which is a host and, thus, exhibit good affinity for vital tissue. However, the apatitè sub-stances have a drawback in that they are inferior in mechanîcal strength, particularly in impact resistance.
Accordingly, studies for the utilization of the apatite substances as implant materials have been directed to the improving the mechanical strength of the ~patltie substances while maintaining the excellent affinity for a bone. For 11~8~78 example, laid-open Japanese Patent Application (Kokai) No.
53-75209 discloses an implant material having a layer of a flame sprayed apatite powder formed on~o ~he periphery of a ceramic core. The flame sprayed layer of this implant material has a rough sur ace and the implant material can be firmly fixed to a bone by the anchor effect owiny to the growth of the bone tissue in the rough area. Therefore, this implant material may provide an excellent artificial dental root, having mechanical strength improved by the rein~orcement of the ceramic material and having good affinity for a bone.
However, in the practical use of artificial dental roots, it should be taken into consideration that it becomes necessary to extract the artificial dental root once implanted when any trouble has occurred. Thus, the above-mentioned implant material may not be suitable for practical use as an artificial dental root since it may have too high an affinity for a bone. In the implant denture technique, an artificial dental root is implanted into the jaw bone or the like and then, after two or three months, a denture is connected onto the implanted dental root. If trouble, such as the displacement or damage of the implanted root, the inflammation of the peripheral tissue or the like, occurs after the implantation of the root, it is necessary to immediately extract the implanted root. In such a case, if the artificial dental root has been extremely firmly fixed to a natural bone such as the jaw bone, a part of the bone may have to be~ resected to ~ 1~8078 extract the implant-ed rootr so that the patient may ex-perience pain or the natural bone may be damaged.
SUMMAR'~ O:F THE INVENTION
The primary object of the prPsent invention is to provide an artificial dental root which does not have the above-mentioned drowbakcs.
Thus, according to the present invention, there is provided an artificial dental root comprised of a composition in which a particulate or powdered form of synthetic hydroxyapatite or calcined or sintered synthetic hydroxy-apatite or a mixture thereof is dispersed in an organic matrix, the surface area of said synthetic dental root to be brought into contact with a bone being composed of both a phase of said hydroxyapatite and a phase of said organic matrix.
It has now been found that if a composite material obtained by molding a blend of a particulate or powdered form of hydroxyapatite oE a specific particle diameter with an organic matrix has a specific area ratio of the hydroxyapatit phase to the organic matrix phase of the surface area to be brought into contact with a bone, the composite material has not only excellent mechanical properties but also moderate ability to coapt with a natural bone.
The term "moderate ability to coapt wi-th a natural bone", as used herein, is intended to mean that the implanted artificial dental root is fixed to the nat~ural bone with a moderate coaptation force which is sufficient to prevent 1 1~8078 the implanted root from being removed Erom ~he vital tissue in a normal state and to ~ithstand the practical use of the resultant denture aEter the connection of the upper structure to the implanted root, but allows the extractio.n of the implanted root without damaging the natural bone when any problems may occur.
DESCRIPTION OF PREFERRED EMBODIMENTS
Hydroxyapatite usable for ~he present invention may be prepared by Xnown processes. Thus, there may ba employed synthetic hydroxyapatite prepared, for example, as desc.ibed in Ceramics, 10, 7, 461(1975), by a dry process wherein Ca3(PO~)2 is reacted with excessive CaCO3 in a steam--containing air flow at a high temperature of 900 to 1300C or by a wet process wh~rein an aqueous solution of Ca(NO3)2 is reacted with an aqueous solution of (NI-I4)H2PO4 under a NH40H alkaline condition. There may also be employed sintered hydroxyapatite obtained by sintering the above-mentioned synthetic hydroxyapatite as well as siniered hydroxyapatite obtained by press molding synthetic hydroxy-apatite prepared by a known process and sintering themolded product at 600 to 1500C.
Hydroxyapatite can also be obtained from a natural bone, for example, by calcining a cattle bone at about 800C to remove the organic substances contained therein.
However, where such hydroxyapatite is employed, there may arise problems with respect to the procurement of the starting material, uniformity in quality and the com-patibility to a living body or the bone formation speed 07~
owing to the presence of retained impurities.
The organic matrix should not deteriorate in a living body and should not deleteriously affect the vital tissue. Preferably, the organic matrix is comprised of one or more polymers selected from bisphenol A-glycidyl methacrylate polycondensates, polymethyl methacrylate, poly-2-hydroxyethyl methacrylate, polyethylene, polysulfones, polyamides, polyesters, polytetra1uoroethylene, poly-vinylidene fluoride and polycarbonates, and copolymers or two or more monomers of said polymers.
The artificial dental root of the present invention may be prepared by blending a particulate or powdered from of hydroxyapatite as mentioned above with an organic matrîx and molding the blend in a known manner. It is lS preerable that the hydroxyapatite has a particle diameter of not more than 1000 ~m, particularly 100 to 0.01~m. It is important that the hydroxyapatite phase is in~a dis-continuous phase in the surface area of the resultant artiicial dental root to be brought into contact with a bone. The area ratio of the hydroxyapatite phase to the organic matrix phase of the surface area to be brought into contact with a bone may preferably be 5:95 to 70.30, particularly 10:90 to 60:40. If the hydroxyapatite phase is in a continuous phase or occupies more than 70~ of the surface area, the coaptation force of the resultant dental , .
root with a natural bone may become too large so that the natural bone is damaged at the time of the extraction of the implanted dental root. On the other handj if the : :
1 15~078 hydroxyapati-te phase occupies less than 5g6 of the surface area, the implanted dental root may be re~loved from the vital tissue in a normal state. It may be advantageous, from the stand point of durability and coaptability to the vital tissue, that the area ratio of the hydroxyapatite phase to the organic matrix phase be in a range from lO:90 to 60:~0.
It will be appreciated from the above description that the characteristic Eeature of the present invention consists in the fact that the excellent ability of hydroxy-apatite to coapt with a bone is advantageously controlled in the use of hydroxyapatite as material for an artificial dental root. Thus, the composite material described above with regard to the artificial dental root according to the present invention may not be suitable for use as a dental cement such as a sealant or filler for a bore or crack in a tooth, but is~very useful for a practical artificial dental root.
The present invention will be further illustrated by the following non-limitative examples.
Exam~el 1 A mixture~(pH ll to 12) of 158.5 g (1.2 mols) of diammonium hydrogenphosphate, 3780 ml of di~stilled water and 1420 ml of concentrated ammonia was added dropwl~se to a stirred mixture of 328 g~(2 mols) of calcium nitrate, 1320 ml of distilled water and 1180 ml of ooncentrated ammonia over the ccurse of 30 minutes. The obtained suspension was centrifuged to obtaln a cake. The cake was :
~.
I 15~07~
dried at 100C ~or 24 hours. The~, a part of the dried cake was heated at 500C for 3 hours in an electric furnace to obtain a hydroxyapatite powder and the remainder was sintered at 1250C for 60 minutes to obtain a white sintered hydroxyapatite.
The elmentary analysis of the non-~intered and sintered hydroxyapatites proved that they had a Ca/P ratio of 1.66 and the ~-ray diffraction thereof also proved that they were of high purity~
The hydroxyapatites obtained as mentioned above were ground and used as the starting material in the following examples.
Example 2 A sintered hydroxyapatite powder having particle diameters of lO to 70 ~m was mixed with a bisphenol A--glycidyl methacrylate/methyl methacrylate mixture (weight ratio 6/4) at a volume ratlo (calcuIated by speclfic gravity) of I:l. After addition of 0.05% by weight of benzoyl peroxide as a polymerization initiator, the mixture was uniormly blended using a stirrer. Then, the blend was charged into a glass tube having an inner.diameter of 5 mm and, ater defoaming, subj cted to a polymerization :
reaction at a temperature of 80C or 2 hours. Thus, a hydroxyapatite compositlon was obtained ~Sample l).
Example 3 The procedure as described in Example 2 was repeated, except that a sintered hydroxyapatite having particle diameters of 100 to 500 ~m was used and 2-hydroxyet~yl ~158078 methacrylate was used ins-tead of methyl methacrylate.
Thus, a hydroxyapatite composition was obtained (Sample 2).
Example 4 By repeating the procedure as described in Example 2, except that a sintered hydroxyapatite and bisphenol A-glycidyl methacrylate/methyl methacrylate (weiy~lt ratio 6~4) were mix2d at a volume ratio of 3:7, a hydroxyapatite composition was obtained (Sample 3).
Example 5 A sintered hydroxyapatite powder having a mean particle deameter of 20 ~m and a finely divided high-density polyethylene were uniformly blended at a vol~une ratio of , ~ , 1:6 using a Henschel mixer, and the blend was press molded to obtain a hydroxyapatite composition (Sample 4).
Example 6 A slntered 'nydroxyapatite powder having particle diameters of 30 to 70 ~ m and methyl methacrylate were mixed at a volume ratio of 1:1. Then, 0.05% by weight of benzoil peroxide was added as a polymerization initiator 20 and the mixture was uniformly blended. ~he blend was defoamed in a glass tube having an inner diameter of 5 mm and heated at 80C for 2 hours to obtain a hydroxyapatite composition (Sample 5).
Example 7 A sintered hydroxyapatite powder having of particle diameters of 30 to 70 ~m was uniformly blended with a finely divided polysulfone or a finely divided poly-~
tetrafluoroethylene, respectively, at a volume ratio of 1 15~07~
1:3, and the ~lend was press molded. Thus, hydroxyapatite composi-tions were obtained (Sample 6 and Sample 7, res-pectively).
Example 8 A non-sintered hydroxyapatite powder having a mean particle diameter of 50 llm was unifoxmly blended ~ith a finely di~ided 6,6-nylon at a volume ratio of 1:3, and the blend was press molded to obtain a hydroxyapatite composition (Sample 8).
Example 9 (Comparison) ~y repeating the procedure as described in Exampe 2, except that a sintered hydroxyapatite powder and bisphenol A-glycidyl methacrylate/methyl methacrylate (weight ratio 6/4) were mixed at a volume ratio of 3:97, a hydro-xyapatite composition was obtained (Sample 9).
Example 10 (Comparison) By repeating the procedure in Example 2, except that a sintered hydroxyapatite powder and bisphenol A--glycidyl methacrylate/methyl methacrylate (weight:ratio 6/4) was mixed at a volume ratio of 3:1, a hydroxyapatite composition was obtained (Sample 10). ~:
Example 11 (Comparison) A hydroxyapatite composition (Sample;ll) was prepared in the manner as in Example 2, except that a glass tube having an inner diameter of 4 mm was used.
Example 12 (Comparison) A sintered:porous hydroxyapatite having: a porosity of 65~ was impregnated with a mixture of blsphenol A-glycidyl ~: :, . --~
1 ~58078 methacrylate~ ethyl methacrylate (weight ratio 6/4) con-taining 0.05~ by weigh-t of benzoil peroxide under a reduced pressure. The impregna~ed hydroxyapatite was heated at 80C for 2 hours to obtain a hydroxyapatite composition (Sample 12).
The compositions obtained in Examples 2 through 10 and E~ample 12 were each cut to a diameter of 4 mm and a length of 10 mm, while the composition obtained in Example 11 was cut to a length of 10 mm. The cut samples were surgically implanted into a thighbone of an adult dog~
After 6 montbs, the thighbone containing each sample was cut off and each thigh~one piece was subjected to a test for evaluating the coaptation with a bone. The area ratios of the hydroxyapatite phase to the organia matrlx phase of the respective samples determined before the implantation are shown in Table l below together with the reuslts of the above-mentioned coaptation test and the results of an impact stréngth test~
The area ratios were evaluated from the photo-micrographs of the surfaces of the respective sampl~es.~The coaptation test was carried out by placing each thighbone piece on the supporting plate of an Instron tester and slowly loading at a speed of 1 cm/min in the axial dlrection of the implanted sample. :
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: o .
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~ o ,~
oo~ o ~ ;~ ~ ~ W
n ~ : o~
~D ~ ~
I u~
I ~ ~ o o o o ~ ~ ~o 5 ~
N ~
. '. I O ~ t` ~
` I ~ ~ ' :~~ ",~
. :~ i ~ '.~ * U~ : .: :~
~ ~o~ 1't~ ~ :
~ ~ , ~
___ ': ' ~ ' . . ~ :
..
'; : ' ~ ' '".
1 1~8Q78 It is apparent from the above re~ults that the artifisial dental roo~ o~ the present invention exhibits moderate affinity for bone and has high mechanical strength.
Example 13 Sample 1 and Sample 9 were each cut into two columns having a diameter of 3.5 mm and a length of 10 mm. The columns were implanted into bores drilled in a jaw bone of an adult dog immediately after the extraction of teeth.
The columns~obtained from Sample 9 were both remo~ed in a normal state after one month, while the columns obtained from Sample 1 were retained even after 6 months. One of the Sample 1 column was easily extracted by a usual tooth extraction technique without damaging the jaw bone. The jaw bone containing the other Sample 1 column was cut o~f after one year and subjected to observations by a light microscope and an X-ray photograph. It was proved that the implanted portion was cured and a new bone was formed in the gap between the implanted column and the jaw bone.
Problems, such as inflamation, foreign-body reaction and the like were not at all observed.
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An artificial dental root comprised of a composition in which a particulate or powdered form of synthetic hydroxy-apatite or calcined or sintered synthetic hydroxyapatite or a mixture thereof is dispersed in an organic matrix, the surface area of said artificial dental root to be brought into contact with a bone being composed of both a phase of said hydroxyapatite and a phase of said organic matrix, and the area ratio of said hydroxyapatite phase to said organic matrix phase of said surface area to be brought into contact with the bone being from 5:95 to 70:30.
2. An artificial dental root according to claim 1 wherein the particle diameter of said synthetic hydroxyapatite or calcined or sintered synthetic hydroxyapatite or said mixture is not more than 1000µm.
3. An artificial dental root according to claim 1 or 2 of the preceding claims, wherein said organic matrix is comprised of one or more polymers selected from bisphenol A-glycidyl methacrylate polycondensates, polymethyl methyacrylate, poly-2-hydroxyethyl methacrylate, polyethylene, polysulfones, polyamides, polyesters, polytetrafluoroethylene, polyvinylidene fluoride and polycarbonates, and copolymers of two or more monomers of said polymers.
4. A process for preparing an artificial dental root comprising uniformly blending a particulate or powdered form of synthetic hydroxyapatite or calcined or sintered synthetic hydroxyapatite or a mixture thereof with an organic matrix, molding the blend, and, during or after the molding, causing the surface area of the molded product to be brought into contact with a bone to be composed of both a phase of said hydroxyapatite and a phase of said organic matrix.
5. A process according to claim 5, wherein said surface area to be brought into contact with a bone is composed of said hydroxyapatite phase and said organic matrix phase in an area ratio of from 5:95 to 70:30.
6. A process according to claim 4 wherein the particle diameter of said synthetic hydroxyapatite or calcined or sintered synthetic hydroxyapatite or said mixture is not more than 1000 m.
7. A process according to claim 5 wherein the particle diameter of said synthetic hydroxyapatite or calcined or sintered hydroxyapatite or said mixture is not more than 1000 m.
8. A process according to claim 4, 5 or 6 wherein one or more polymers selected from bisphenol A-glycidyl methacrylate polycondensates, polymethyl methacrylate, poly-2-hydroxyethyl methacrylate, polyethylene, polysulfones, polyamides, polyesters, polytetrafluoroethylen, polyvinylidene fluoride and poly-carbonates, and copolymers of two or more monomers of said polymers are employed as said organic matrix.
9. A process according to any one of claim 4, 5, or 6 wherein the molded product is cut into a desired shape and size.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12357180A JPS5749686A (en) | 1980-09-08 | 1980-09-08 | Liquid crystal composition |
| JP123571/78 | 1980-10-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1158078A true CA1158078A (en) | 1983-12-06 |
Family
ID=14863868
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000336458A Expired CA1158078A (en) | 1980-09-08 | 1979-09-25 | Artificial dental root |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5749686A (en) |
| CA (1) | CA1158078A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57155282A (en) * | 1981-03-20 | 1982-09-25 | Mitsubishi Chem Ind Ltd | Liquid crystal composition |
| JPS59182879A (en) * | 1983-04-01 | 1984-10-17 | Hitachi Ltd | Liquid crystal composition |
| JPS59179561A (en) * | 1983-03-29 | 1984-10-12 | Hitachi Ltd | Anthraquinone pigment and liquid crystal composition containing the same |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0025809A1 (en) * | 1979-09-21 | 1981-04-01 | BBC Aktiengesellschaft Brown, Boveri & Cie. | Liquid crystals mixture |
| CH643291A5 (en) * | 1980-03-21 | 1984-05-30 | Asulab Sa | LIQUID CRYSTAL COMPOSITION FOR ELECTRO-OPTICAL DEVICE. |
| DE3014933A1 (en) * | 1980-04-18 | 1981-10-29 | Bayer Ag, 5090 Leverkusen | LIQUID CRYSTAL MATERIALS CONTAINING ANTHRACHINONE DYES |
-
1979
- 1979-09-25 CA CA000336458A patent/CA1158078A/en not_active Expired
-
1980
- 1980-09-08 JP JP12357180A patent/JPS5749686A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5749686A (en) | 1982-03-23 |
| JPH0223595B2 (en) | 1990-05-24 |
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