Denture system, engagement piece used for denture system, method for producing denture base and denture

A denture system comprising: abutments coupled to the fixtures; and a denture to be detachably attached to the abutments, the denture including: a denture base; an artificial tooth supported by the denture base; a plurality of engagement piece members defining slits extending in the up-down direction; and a lid portion connecting end portions of the engagement piece members as well as closing one end of fitting hole in the up-down direction and covering an entire surface of the tip of the abutment, wherein the lid portion configures a part of the denture base, the piece member has a first surface and a second surface, and a grooved allowance portion is provided allowing the piece member to deform and spread in direction from the first surface toward the second surface.

TECHNICAL FIELD

The present invention relates to a denture system and dentures.

BACKGROUND ART

In recent years, denture systems so called “implants” are beginning to employ a structure including one or more fixtures (implant bodies), and a number of artificial teeth greater than the number of fixtures. With such a system, the number of fixtures can be reduced, thereby reducing the physical and economic burden on the patient.

On the other hand, in a system of this type, a denture including a denture base and artificial teeth is detachably attached to an abutment fixed to a fixture. (the first patent document)

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

However, the conventional technique requires a step of finishing the denture by filling an area to be the denture base with a resin, with a semi-finished product (unfinished) denture, which has been obtained by taking an impression and molding, attached to the abutment. This step may increase the physical/time burden on the patient and the dentist and the cost.

This problem will be described in detail.

Impression materials used when taking an impression of the oral cavity and plasters, which are materials of male molds produced from the impression materials, have very little shrinkage when set. On the other hand, with conventional techniques, a hook attached to the abutment is firmly fitted to the abutment with no gap therebetween.

Therefore, even if materials have little shrinkage, it will not be possible to prevent the hook from giving an external force onto a plurality of abutments spaced apart from one another. Such an external force may deteriorate the fit and may also apply a load on the fixture.

Therefore, as described above, with conventional techniques, a semi-finished product of a denture is filled with a resin to be the denture base, with the semi-finished product attached to the abutment installed in the oral cavity.

Therefore, it is an object of the present invention to reduce the physical/time burden on the patient and the dentist and the cost.

In order to achieve the object set forth above, a system of the present invention is, in one aspect, a denture system including a fixture2to be buried in an oral tissue4, an abutment3coupled to the fixture2and having a surface to be exposed in an oral cavity, and a denture1to be detachably attached to the abutment3, wherein: the denture1includes a denture base10made of a nylon-based thermoplastic resin to be in contact with a gum40, an artificial tooth11supported by the denture base10, and at least one tongue-shaped engagement piece member13, wherein the engagement piece member13is deformed to flare out, as if by pivoting about an end portion13athereof in a vertical direction Z, when attaching/detaching the denture1, and the engagement piece member13engages with the abutment3when worn, and wherein the engagement piece member13, by itself or together with the denture base10, defines a fitting hole14to be detachably fitted over said surface of the abutment3; the engagement piece member13is formed by a nylon-based thermoplastic resin, and the engagement piece member13has a first surface31extending in a horizontal direction X along said surface of the abutment3over a range of a center angle θ less than 180° and extending in the vertical direction Z from the end portion13ato be in contact with said surface of the abutment3, and has a second surface32opposite to the first surface31; and the denture base10has a third surface33opposing the second surface32while being spaced apart from the second surface32, defining a groove-shaped allowance portion15between the second surface32of the engagement piece member13and the third surface33of the denture base10, wherein the allowance portion15allows the engagement piece member13to be deformed to flare out in a direction X of moving from the first surface31toward the second surface32.

In the system of the present invention, the abutment3fits into the fitting hole14, formed by the engagement piece members13, thereby making it possible to attach/detach the entire denture1to the abutment3.

Since the fitting hole14is formed by the engagement piece members13made of a nylon-based resin, a high positional precision of the fitting hole14with respect to the abutment3is not needed because of the elastic deformation of the engagement piece members13.

That is, even if the position of the fitting hole14is slightly shifted with respect to the abutment3, the engagement piece member13made of a nylon-based resin is elastically deformed, as if by pivoting about the end portion13athereof, thereby improving the fit of the denture1. Moreover, the external force acting upon the fixture2due to the shifting will be reduced significantly.

There is no longer a need for the step of fixing a metal piece to the denture base with the denture base placed in the patient. This reduces the physical/time burden on the patient and the dentist.

In the present system, the denture base and the engagement piece members are formed by a nylon-based thermoplastic resin (polyamide). The polyamide resin can stretch significantly in response to a stress and is easily elastically deformed. This results in a good fit. Note that the polyamide may be TR90 from EMS.

In the present invention, a metal base may be included, in addition to the denture base10made of nylon. The metal base is formed by a metal or an alloy, such as a gold alloy, cobalt chrome or titanium, for example, and is arranged on the inner surface or the inside of the denture base10, thereby reinforcing the denture base10or connecting together a plurality of denture bases10for reinforcement.

In the present invention, a reinforcement material of a glass fiber, a metal, or the like, may be added inside the denture base10made of nylon, and the denture base10may be formed by an FRP, for example.

Now, since the denture1is removed and cleaned on a daily basis, engagement piece members13made of a resin may deteriorate or may be deformed permanently. In contrast, if engagement piece members13are formed by a nylon-based resin, they are less likely to be deformed permanently, and the engagement piece members13can be restored by adjusting the shape of the engagement piece members13back to its initial shape, etc., while blowing a hot air at and around the engagement piece members13.

DESCRIPTION OF EMBODIMENTS

In a preferred embodiment of the present invention, one or more engagement piece members13are provided for one fitting hole14, and a slit13sextending in the vertical direction Z is defined between the engagement piece member13and the denture base10or between the plurality of engagement piece members13and13; and more preferably, the engagement piece members are integrally continuous with one another via the end portion13aand an area of the denture base10that covers the head of the abutment.

One or more engagement piece members13can freely deform with respect to one another by virtue of slits13sextending in the vertical direction Z. Therefore, the positional shift of the fitting hole14with respect to the abutment3can be easily absorbed.

In a more preferred embodiment of the present invention, the abutment3includes a male screw portion3sto be screwed into the fixture2, and a top3tprojecting from the fixture2to be fitted into the denture1through the fitting hole14, wherein the abutment3defines a narrowed circumferential engaged groove3eto be engaged by the engagement piece member13between the top3tand the male screw portion3s, and a plurality of longitudinal grooves3g, the number of which is equal to the number of slits13s, spaced apart from one another in a direction of the circumference, extending from the top3ttoward the male screw portion3s, and having a depth generally equal to or greater than a depth of the engaged groove3e.

Note that the term “toppu (top)” means “top” in English, referring to the top portion, irrespective of whether it is pointing upward/downward.

In such a case, the longitudinal groove3gof the abutment3allows the core to come into the engaged groove3eof the abutment3. A plurality of longitudinal grooves3gof the abutment3are useful as grooves to be engaged with a tool when screwing the abutment3into the fixture2.

In another preferred embodiment of the present invention, the system further includes a replica3R having a similar shape to the abutment3, the replica3R including a male screw portion3sto be screwed into the fixture2, and a top3tprojecting from the fixture2so that the top3tcan be fitted into the denture1through the fitting hole14, wherein the replica3R of the abutment defines a narrowed circumferential engaged groove3ewhich can be engaged with the engagement piece member13between the top3tand the male screw portion3s, and a plurality of longitudinal grooves3g, the number of which is equal to the number of slits13s, spaced apart from one another in a direction of the circumference, extending from the top3ttoward the male screw portion3s, and having a depth generally equal to or greater than a depth of the engaged groove3e.

In such a case, the longitudinal groove3gof the replica3R allows the core to come into the engaged groove3eof the abutment3.

Since the longitudinal groove3gis formed in the replica3R of the abutment3and there is no need to provide the longitudinal groove3gin the abutment3, the engagement between the abutment3without the longitudinal groove3gand the engagement piece members13may likely be stable.

In a preferred embodiment of the present invention, the end portion13aof the engagement piece member13is integrally continuous with the denture base10. The engagement piece member13and the denture base10integrally continuous with each other will less likely be damaged by an external force.

In another preferred embodiment of the present invention, a plurality of engagement piece members13are formed as a single engagement piece13P made of the nylon-based thermoplastic resin. The engagement piece13P does not have a shape unique to the patient, and can therefore be mass-produced in advance with a high precision. This allows for a cost reduction and a performance enhancement.

In a more preferred embodiment of the present invention, another resin different from the resin for coupling together the engagement piece member13and the denture base10is inserted.

The other resin in such a case may be a two-component resin, called an “autopolymerizing resin (selfcuring resin)”, and since technicians always have such a resin on hand, the method can easily be carried out.

In a more preferred embodiment of the present system, a plurality of fixtures2and abutments3are provided in the oral cavity, and the system is applied to the fixtures2and the abutments3.

Note however that the fixture2and the abutment3may be provided only in one location with the provision of a clasp.

In a more preferred embodiment of the present system, the engagement piece member13and the allowance portion15are provided on the left side and on the right side of each fitting hole14so that the positions of the fitting holes14for the abutments3can be slightly moved in the left-right direction X1of the horizontal direction X.

In such a case, even if there is a slight error between the pitch between a plurality of abutments3and3and the pitch between a plurality of fitting holes14and14, awkwardness will unlikely be felt when the denture1is worn because of the slight movement of the engagement piece members13.

In a more preferred embodiment of the present system, the engagement piece member13and the allowance portion15are arranged in front of the fitting hole14and on the back of the fitting hole14so that the position of the fitting hole14with respect to the abutment3is allowed to move slightly in the front-back direction Y.

In such a case, as the engagement piece member13slightly moves also in the front-back direction Y, substantially no awkwardness will be felt when the denture1is worn.

On the other hand, in one aspect, a method for producing the denture1of the present invention includes the steps of: producing a female mold50of the oral cavity using a flexible impression material23with at least the fixture2buried in the oral tissue4; producing, from the female mold50, a male mold51having a shape of the abutment3and a shape of the oral cavity; attaching a core70at least having a shape of a groove15forming the allowance portion15over an area of the male mold51corresponding to the abutment3; producing a matrix52by filling, with a filler53, a gap S to be an undercut formed between an end face at an upper end or a lower end of the core70and a surface of the male mold51; and obtaining, from the matrix52, the denture base10and the engagement piece member13made of a resin.

With this method, the core70forms the groove15to be the allowance portion15, and an undercut S is filled with the filler53. This allows the resin of the denture base10to be released from the core70.

In an embodiment of the present method, in the step of producing the female mold50, the female mold50is produced with the abutment3or the replica3R of the abutment3attached to the fixture2.

In such a case, in a preferred embodiment, the abutment3or the replica3R is provided with a cylindrical outer circumferential surface39at a position in the vicinity of the fixture2, wherein the cylindrical outer circumferential surface39has an outer diameter which is larger than an outer diameter of a top3tprojecting from the fixture2to be fitted into the denture1through the fitting hole14and which is smaller than an outer diameter of the fixture2;

the core70includes a C-shaped or ring-shaped positioning portion79for positioning the core70with respect to the male mold51by being fitted over, while being in contact with, an area519of the male mold51corresponding to the cylindrical outer circumferential surface; and

in the attachment step, the core70is attached to the male mold51with the positioning portion79fitted over the area519corresponding to the cylindrical outer circumferential surface39.

In this preferred embodiment, the core70is positioned with respect to the male mold51with the positioning portion79fitted to the area519of the male mold51corresponding to the cylindrical outer circumferential surface39. Therefore, even an inexperienced technician can position the core70with respect to the male mold51with a high precision.

Herein, the term “cylindrical outer circumferential surface” means that the outer circumferential surface does not need to be a complete cylindrical surface, but a portion of the cylindrical surface may be missing, and it may also be a tapered cylindrical surface.

The C-shaped or ring-shaped positioning portion79means that the positioning portion79may have an incomplete, C-shaped ring shape, as well as a complete ring shape.

In still another preferred embodiment, the core70includes a cylindrical portion72A having a cylindrical shape, and a plurality of blade portions71A extending from an inner circumferential surface of the cylindrical portion72A toward a center of the cylindrical portion72A at positions corresponding to the slits13s, wherein a part or whole of the slits13sis formed by virtue of the blade portions71A in the step of obtaining the denture base10.

Since the blade portions71A form the slits13s, the formation of the slits13sis facilitated.

Note that the slits13smay be partially formed by the blade portions71A, with the remaining portion of the slits13sbeing formed by removing the resin by processing.

In a more preferred embodiment of the present method, in the step of producing the male mold51, longitudinal grooves51gfor receiving projecting ends of the blade portions71A fitted thereto and allowing the blade portions71A to move vertically when the core70is attached are provided in an area of the male mold51corresponding to the abutment3, and the blade portions71A of the core70are attached in the vertical direction Z along the longitudinal grooves51g.

In such a case, the blade portions71A come into the engaged grooves3eof the abutment3. Therefore, since a part or whole of the slits13sis formed in the molding process, the formation of the slits13sis facilitated.

In another preferred embodiment of the present method, the method further includes a processing step of removing portions of the denture base10, produced from the matrix52, to be slits13s.

In such a case, since the slits13sare formed by subsequent processing, the shape of the core70is simplified, and it is possible, with cores70of a single shape, to accommodate abutments3of different shapes.

In still another embodiment of the present method, in the step of producing the male mold51, the male mold51having a shape of the oral cavity, with the replica60of the fixture2buried in the male mold51, is produced from the female mold50; and in the step of attaching the core70, the core70having a shape of the fitting hole14and a shape of a groove15forming the allowance portion15is attached to the replica60.

In such a case, since the core70is attached to the replica60of the fixture2, the positional shift of the allowance portion15with respect to the fixture2is unlikely to occur.

In still another embodiment of the present method, the method includes: a step of producing a female mold50of an oral cavity with at least the fixture2buried in the oral tissue4; a step of producing, from the female mold50, a male mold51having a shape of a projecting portion15P corresponding to the allowance portion15and a shape of the oral cavity; a step of producing, from the male mold51, a denture base10having a shape of a hole15H forming the allowance portion15; and a coupling step of coupling an end portion of the engagement piece13P in the vertical direction Z to the denture base10, with the engagement piece13P and the denture base10being spaced apart from each other over the allowance portion15, thereby obtaining the denture1while ensuring the allowance portion15.

If an engagement piece13P including a plurality of engagement piece members13is formed in advance, as described above, it saves the technician's labor of molding slits between a plurality of engagement piece members13, thus facilitating the fabrication of the denture1.

A system of the present invention is, in another aspect, a denture system applied to a plurality of fixtures2buried in an oral tissue4, the denture system comprising: abutments3coupled to the fixtures2and having a surface to be exposed in an oral cavity; and a denture1to be detachably attached to the abutments3, the denture1including:

a denture base10made of a resin and to be in contact with a gum40;

an artificial tooth11supported by the denture base10;

a plurality of tongue-shaped engagement piece members13that are plurally separated in a circumferential direction, wherein the engagement piece members13are deformed to spread, as if by pivoting about each end portion13athereof in an up-down direction Z, when attaching and detaching the denture1, and the engagement piece members13engage with the abutments3when worn, and wherein the engagement piece members13define a slit13sextending in the up-down direction Z and define a fitting hole14to be detachably fitted over the surface of the abutment3;

a lid13cconfiguring a part of the denture base10, wherein the lid portion13ccloses one end of the fitting hole14in the up-down direction Z as well as connects end portions13aof the engagement piece members13with each other, and covers an entire surface of a top3tof each of the abutments3,

each of the engagement piece members13and the lid portion13care formed by a nylon-based thermoplastic resin,

each of the engagement piece members13has a first surface31extending in a horizontal direction X along the surface of the abutment3over a range of a center angle θ less than 180° and extending in the up-down direction Z from one of the end portions13ato be in contact with the surface of the abutment3, and has a second surface32opposite to the first surface31; and

a groove-shaped allowance portion15provided for an outer circumference of the second surface32of each of the engagement piece members13, wherein the allowance portion15allows the engagement piece members13to be deformed to spread in a direction from the first surface31toward the second surface32.

Preferably, the denture base10has a third surface33opposing the second surface32while being spaced apart from the second surface32, and the groove-shaped allowance portion15is defined between the second surface32of each the engagement piece members13and the third surface33of the denture base10.

Preferably, a plurality of cushion portions16, a plurality of arc-shaped cushion portions16, or an annular cushion portion16is integrally formed in an area of the lid portion13ccorresponding to an outer circumferential edge of the top3tof each of the abutments3, and each of the cushion portions16projects toward each of the abutments3inside the engagement piece members13.

The cushion portion16works as a cushion to the denture1instead of a natural periodontal ligament by elastically deforming after receiving the reaction force from a surface of the top3tof the abutment3when biting.

In this case, the cushion portion16is integrally formed in the engagement piece13P in advance, thereby further reducing a dental technician's burden.

An engagement piece of the present invention is used for a denture system including an abutment3having a surface to be exposed in an oral cavity and a denture1to be detachably attached to the abutment3,

the denture1comprising: a body part12of a denture base10, the denture base10formed by a resin and to be in contact with a gum40; an artificial tooth11supported by the body part12of the denture base10; and an engagement piece13P for engaging the body part12of the denture base10to the abutment3, the engagement piece13P formed by a nylon-based thermoplastic resin and forming a part of the denture base10, wherein the engagement piece13P includes:

a lid portion13cto cover an entire surface of a top3tof the abutment3and to be covered by the body part12of the denture base10, and

a plurality of engagement piece members13extending from the lid portion13cin an up-down direction Z, wherein the engagement piece members13elastically deform to spread around an end portion13ain the up-down direction Z when attaching and detaching the denture1, engage with the abutment3when worn, and are spaced apart from one another in a circumferential direction,

wherein each of the engagement piece members13has a first surface31to be in contact with an outer circumferential surface of the abutment3and has a second surface32opposite to the first surface3, and the first surfaces31of the engagement piece members13define a fitting hole14to be detachably fitted over the outer circumferential surface of the abutment3, and

the lid portion13ccloses one end, in the up-down direction Z, of the fitting hole14defined by the engagement piece members13.

When the engagement piece13P is produced by injection molding with metal patterns in a lot production, it is not necessary for a dental technician to manufacture every time a plurality of engagement piece members13or a slit13sbetween the engagement piece members13.

Preferably, the engagement piece13P further comprises an outer portion13rextending in the up-down direction Z from a circumference of the lid portion13cto sandwich a tubular member between the outer portion13rand the engagement piece members13, and the outer portion13rhas a third surface33being further from an axis3L of the abutment3than the second surfaces32of the engagement piece members13, and the outer portion13ris joined to the body part12of the denture base10,

an allowance portion15is defined between the second surfaces32and the third surface33of the outer portion13rand allows the engagement piece members13to be elastically deformed to spread in a direction from the first surface31toward the second surface32, and

the lid portion13ccloses one end, in the up-down direction, of the fitting hole14defined by the engagement piece members13and the one end, in the up-down direction, of the allowance portion15.

In this case, it is easy for a dental technician to form the allowance portion15when molding the denture base10.

More preferably, the outer portion13rof the engagement piece13P extends in the up-down direction Z from an outer circumference of the lid portion13cand is formed in tubular shape, and an inner circumferential surface of the tubular outer portion13rdefines the third surface33.

In this case, it becomes much easier to form the allowance portion15.

Preferably, a plurality of cushion portions16, a plurality of arc-shaped cushion portions16, or an annular cushion portion16is integrally formed in an area of the lid portion13ccorresponding to an outer circumference of the top3tof the abutment3, and each of the cushion portions16projects toward the abutment3inside the engagement piece members13.

The cushion portion16works as a cushion to the denture1instead of a natural periodontal ligament by elastically deforming after receiving the reaction force from a surface of the top3tof the abutment3when biting.

In this case, the cushion portion16is integrally formed in the engagement piece13P in advance, thereby further reducing a dental technician's burden.

Now, a resin itself is colorless and transparent. A resin used for the denture base10of a denture is always provided with a pigment in order to obtain a tone of color similar to gum. However, in light of safety to human body, such a pigment is limited to fine powder of metallic oxide such as Fe2O3and TiO2having a rough surface in microscopic.

Such fine powder having rough surface damages resin material of an engagement piece member13in microscopic when the engagement piece member13deforms. Therefore, if an additive amount of the pigment is set to be from 0.10 weight percent to 0.20 weight percent as in the past, strength of the engagement piece member13may be deteriorated by detaching and attaching a denture1every day. If this deterioration becomes remarkable, elasticity of the engagement piece member13may be lost, or the engagement piece member13may be damaged.

Therefore, preferably, a ratio of a pigment to a resin forming the engagement piece13P is set to be from 0 weight percent to 0.07 weight percent.

In this case, since a ratio of the pigment is smaller than a conventional ratio of the pigment, the denture1shows an excellent durability when repeatedly detaching from and attaching to the abutment3.

When no pigment is contained into the engagement piece13, the engagement piece member13may show the most excellent durability. On the other hand, when texture (feeling) of a denture base10is considered to be important, it is preferable to contain a small amount of pigment.

From such a view point, it is preferable that a ratio of a pigment to a resin (nylon) forming an engagement piece13is set to be from 0 weight percent to 0.05 weight percent, and it is most preferable that such a ratio is set to be from 0 weight percent to 0.03 weight percent.

Note: even if no pigment is added to nylon of the engagement piece13P, adding a pigment into a resin of the body part12of the denture base10prevents texture (feeling) from degrading.

Preferably, a ratio of pigment contained in a resin forming the engagement piece13P is smaller than a ratio of pigment contained in a resin forming the body part12.

In this case, a ratio of pigment contained in a nylon of the engagement piece member13is smaller than a ratio of pigment contained in a resin of the body part12of the denture base10. Therefore, an excellent durability and good texture (feeling) will be achieved.

A method for producing a denture1according to the present invention, in another aspect, is

a method for producing a denture1to be detachably attached to the abutment3having a surface to be exposed in an oral cavity,

the denture1including a body part12of a denture base10made of a resin and to be in contact with a gum40, an artificial tooth11supported by the body part12of the denture base10, and an engagement piece13P made of a nylon-based thermoplastic resin, forming a part of the denture base10, and engaging the body part12of the denture base10to the abutment3, wherein the engagement piece13P includes:

a lid portion13cto cover an entire surface of a top3tof the abutment3and to be covered by the body part12of the denture base10;

a plurality of engagement piece members13extending from the lid portion13cin an up-down direction Z, wherein the engagement piece members13elastically deform to spread around an end portion13ain the up-down direction Z when attaching and detaching the denture1, engage with the abutment3when worn, and are spaced apart from one another in a circumferential direction, wherein each of the engagement piece members13has a first surface31to be in contact with an outer circumferential surface of the abutment3and has a second surface32opposite to the first surface3, and the first surfaces31of the engagement piece members13define a fitting hole14to be detachably fitted over the outer circumferential surface of the abutment3; and

an outer portion13rextending in the up-down direction Z from a circumference of the lid portion13cto sandwich a tubular member between the outer portion13rand the engagement piece members13, and the outer portion13rhas a third surface33being further from an axis3L of the abutment3than the second surfaces32of the engagement piece members13, and the outer portion13ris joined to the body part12of the denture base10,

an allowance portion15is defined between the second surfaces32and the third surface33of the outer portion13rand allows the engagement piece members13to be elastically deformed to spread in a direction from the first surface31toward the second surface32, and

the lid portion13ccloses one end, in the up-down direction, of the fitting hole14defined by the engagement piece members13and the one end, in the up-down direction, of the allowance portion15,

wherein the method for producing the denture1comprises the steps of:

producing a female resin mold54having a depressed portion500corresponding to a shape of an oral tissue4, and the engagement piece13P embedded in the depressed portion500;

inserting a restraint member R into the allowance portion15of the engagement piece13P, the restraint member R to be inserted into the allowance portion15and to be a core when molding the body part12of the denture base10, preventing the outer portion13rfrom deforming toward the engagement piece members13when molding the body part12of the denture base10;

producing a male plaster mold56by pouring a plaster into the depressed portion500of the female resin mold54after the insertion of the restraint member R, the restraint member R and the engagement piece13P being integral with the plaster;

producing a denture base10in which the engagement piece13P is integral with the body part12of the denture base10by supplying a molten resin around the male plaster mold56; and

removing the male plaster mold56and the restraint member R.

In this case, the restraint member R restrains the outer part13rfrom deforming toward the engagement piece members13when molding the denture base10. Thereby, the allowance portion15is secured, and the engagement piece members13engage with an engaged part of the abutment3, and the denture1is attached to or detached from the abutment3.

Furthermore, since the engagement piece members13are formed in the engagement piece13P in advance, it is easy for a dental technician to work.

Especially, since the restraint member R or a tubular member R1is inserted into the allowance portion15, the outer portion13ris prevented from its deformation caused by pressure in molding process of the denture base10.

A method for producing a denture1according to the present invention, in still another aspect, is

a method for producing a denture1to be detachably attached to the abutment3,

the denture1including a body part12of a denture base10made of a resin and to be in contact with a gum40, an artificial tooth11supported by the body part12of the denture base10, and an engagement piece13P made of a nylon-based thermoplastic resin, forming a part of the denture base10, and engaging the denture base10to the abutment3, wherein the engagement piece13P includes:

a lid portion13cto cover an entire surface of a top3tof the abutment3and to be covered by the body part12of the denture base10; and

a plurality of engagement piece members13extending from the lid portion13cin an up-down direction Z, wherein the engagement piece members13elastically deform to spread around an end portion13ain the up-down direction Z when attaching and detaching the denture1, engage with the abutment3when worn, and are spaced apart from one another in a circumferential direction,

wherein each of the engagement piece members13has a first surface31to be in contact with an outer circumferential surface of the abutment3and has a second surface32opposite to the first surface31, and the first surfaces31of the engagement piece members13define a fitting hole14to be detachably fitted over the outer circumferential surface of the abutment3,

the method for producing the denture comprising the steps of:

producing a female mold50having a depressed portion500corresponding to a shape of an oral tissue4, and a replica3R of the abutment3embedded in the depressed portion500;

producing a male mold51by pouring a plaster into the depressed portion500of the female mold50, the replica3R projecting from the male mold51;

externally fitting the engagement piece13P on the replica3R of the male mold51, wherein a tubular member R1for forming an allowance portion15is externally fitted on an outer circumference of the engagement piece members13of the engagement piece13P, and the allowance portion15allows an elastic deformation of the engagement piece members13;

producing a denture base10in which the engagement piece13P and the tubular member R1are integral with the body part12of the denture base10by supplying a molten resin around the male plaster mold56; and

removing the male plaster mold51and the tubular member R1.

The present invention will be understood more clearly from the following description of preferred embodiments taken in conjunction with the accompanying drawings. Note however that the embodiments and the drawings are merely illustrative, and should not be relied upon for defining the scope of the present invention. The scope of the present invention shall be defined only by the appended claims. In the accompanying drawings, like reference numerals denote like components throughout the plurality of figures.

As shown inFIGS. 1A and 1C, the present denture system includes the denture1, the fixture2, and the columnar abutment3.

As shown inFIG. 2, the fixture2is a so-called “implant body”, an artificial tooth root obtained by performing a surface process (surface finishing) on a biomaterial (a typical material being titanium, which is well compatible with a living body). The fixture2is buried in the oral tissue4such as an alveolar bone41of the jaw to be integrated with the bone.

The abutment3is coupled to the fixture2and exposed in the oral cavity. That is, the abutment3is fixed to the fixture2with a screw (not shown) and is coupled to the fixture2so that the artificial denture1can be attached thereto.

As shown inFIGS. 1A and 1C, the denture1is detachably attached to the abutment3. The denture1includes the nylon-made denture base10to be in contact with the gum40, and ceramic artificial teeth11integral with the denture base10and supported by the denture base10.

For example, a pair of the fixtures2and the abutments3is provided in the oral cavity, and the present system is applied to the pair of the fixtures2and the abutments3.

The artificial teeth11are secured to one end of the denture base10in the vertical direction Z. The other end surface of the denture base10in the vertical direction Z is softly in contact with the gum40.

As shown in the enlarged cross-sectional view ofFIG. 3A, the denture base10includes a main body12and the engagement piece members13integrally continuous with each other, and defines the fitting holes14into which columnar abutments3are detachably fitted. The engagement piece members13and the denture base10are formed by a nylon-based thermoplastic resin, for example.

The fitting holes14are open toward the gum40. That is, the fitting holes14of an upper denture1are open in the upward direction, and the fitting holes14of a lower denture1are open in the downward direction.

As shown inFIGS. 3A and 3B, in the present embodiment, the engagement piece member13forms a part of the fitting hole14. That is, in the present embodiment, as clearly shown inFIG. 3B, the fitting hole14is defined by the main body12and the engagement piece member13. The fitting hole14positions and fixes the denture base10with respect to the abutment3. The engagement piece member13has a first surface31to be in contact with and engaging with the side surface of the abutment3, and a second surface32opposite to the first surface31.

In the present embodiment, where the denture1is placed in the lower jaw, the upper end portion13aof the engagement piece member13ofFIG. 3Ais continuous with the denture base10, and the engagement piece member13extends downwardly in the vertical direction Z from the end portion13aof the engagement piece member13.

Note that although not shown, in a case where the denture1is placed in the upper jaw, the lower end portion of the engagement piece member13is continuous with the main body12, and the engagement piece member13extends upwardly in the vertical direction Z from the end portion of the engagement piece member13.

In the present embodiment, an engagement element (engagement protrusion)13eto be engaged with the narrowed engaged groove (engaged element)3eof the abutment3is formed integrally with the engagement piece member13at the lower end of the engagement piece member13. As the engagement element13eis engaged with the engaged groove3e, the denture1is prevented from inadvertently coming off the abutment3.

The denture base10ofFIG. 3Bincludes the allowance portion15formed between the second surface32and the third surface33of the main body12, wherein the allowance portion15allows the engagement piece member13to move or deform in the horizontal direction X from the first surface31toward the second surface32. The allowance portion15is provided as a groove15formed in the denture base10. The third surface33is spaced apart from, and opposing, the second surface32.

In the present embodiment, the groove15is continuous with the fitting hole14via the slit13s, thereby facilitating the movement of the engagement piece member13. When placing/removing the denture1, the engagement piece member13retracts toward the groove15, thereby allowing the denture1to be attached/detached to/from the abutment3.

The denture base10may include a cushion portion16formed at the deep end in the vertical direction Z of the fitting hole14ofFIG. 3A. The cushion portion16is formed by a plurality of small projections, and the projections will provide the denture1with cushioning in place of the natural periodontal membrane by elastically deforming when clenching the teeth.

The denture base10made of a nylon-based resin will unlikely deteriorate and will unlikely whiten over years of use. Moreover, the denture base10of such a material will unlikely lose the elasticity of the engagement piece member13. Particularly, when the engagement piece member13deteriorates due to permanent deformation, lowering of elasticity, etc., it will be possible to restore the engagement piece member13while heating, with a hot air, the engagement piece member13and the denture base10around the fitting hole14.

FIGS. 4A and 4Bshow a reference embodiment as an aid to understanding the present invention.

In this example, a pair of engagement piece members13is provided. The pair of engagement piece members13extend in the horizontal direction X from the denture base10. In this example, it will be difficult to release in the molding process.

In Embodiment 2, a pair of semi-cylindrical engagement piece members13is provided. The pair of engagement piece members13extend in the vertical direction Z from the denture base10. The groove15is filled with a buried material18such as silicone gel (i.e., the material18is buried in the groove15). The buried material18compressively deforms to allow the movement of the engagement piece member13.

In Embodiment 3, the engagement piece member13is provided while being divided in four pieces. The four divided engagement piece members13form a generally cylindrical shape as a whole, and extend in the vertical direction Z from the denture base10. Note that the engagement element13emay be formed as a small hemispherical projection integral with the first surface31(seeFIG. 20B).

In Embodiments 2 and 3, where the engagement piece member13and the allowance portion15are arranged on the left side and on the right side of the fitting hole14, the position of each fitting hole14with respect to the corresponding abutment3is allowed to move slightly in the left-right direction X1of the horizontal direction X.

Where the engagement piece member13and the allowance portion15are arranged in front of the fitting hole14and on the back of the fitting hole14, the position of the fitting hole14with respect to the abutment3is allowed to move slightly in the front-back direction Y. Thus, where slight movement is allowed in the left-right direction X1or the front-back direction Y, a shift between the position of the abutment3and the position of the fitting hole14will be absorbed in these directions.

Next, an example of a method for producing the denture base10according to the present invention will be described with reference toFIGS. 7A to 12B. Note that for the convenience of drafting figures, the protruding portion of the engagement piece member13is not shown in the embodiment ofFIGS. 7A to 16Band in the embodiment ofFIGS. 18 and 19.

First, as shown in step1ofFIG. 7A, the dentist produces a female mold50of the oral cavity with the fixture2buried therein according to a well-known method.

That is, after attaching, by screwing, a guide pin22into a female screw of the fixture2, the dentist places the impression material23made of a self-hardening resin in the oral cavity, and presses the surface of the impression material23against the surface of the oral cavity. The impression material23is more flexible than the nylon-based resin forming the denture base10. Next, an open tray21is set so that the guide pin22projects through a window20of the open tray21. Then, after turning the tip of the guide pin22to take out the guide pin22from the female screw of the fixture2, the open tray21and the impression material23are removed from the oral cavity. Thus, the female mold50is produced.

Next, as shown in step2ofFIG. 7B, after the impression material23is solidified, a replica60of the fixture2is screwed and fixed to the tip of the guide pin22. The subsequent steps are performed by the dental technician rather than the dentist.

As shown in step3ofFIG. 8A, the technician pours a plaster51aonto the surface of the impression material23in order to make a male mold51of the impression material23. Thus, the male mold51ofFIG. 8B, having the replica60of the fixture2is buried therein and having the shape of the oral cavity, is produced from the female mold50.

Then, in the order from step4ofFIG. 8Bto step6ofFIG. 9B, a first core70having the shape of the fitting hole14, the shape of the slit13sand the shape of the groove15forming the allowance portion15as shown inFIG. 9Bis attached to the replica60ofFIG. 8B, thereby producing a matrix52of the denture base10ofFIG. 9B.

In order to produce the matrix52from the male mold51ofFIG. 8B, a metal first part71having the shape of the fitting hole14and the slit13sand forming a part of the first core70is first screwed and attached into a female screw60sof the replica60as shown in step5ofFIG. 8C. After the attachment of the first part71, a second part72having the shape of the groove15and forming the other part of the first core70is attached over the first part71as shown inFIG. 9A.

Now, although a gap S to be an undercut in the molded product is formed between the end surface of the second part72and the surface of the male mold51, as shown inFIG. 9B, the shape of the first core70of the matrix52is corrected by filling the gap S with the filler53. Note that the filler53may be a resin such as a silicone resin or an epoxy resin, a plaster, a clay, etc., as well as a wax. Note that the second part72is preferably provided with a rotation preventing means, such as grooves72einto which the blade portions71A of the first part71fit. Such grooves72eprevent the second part72from rotating, and prevents the portion formed by the filler53from positionally shifting with respect to the male mold51.

Then, the matrix52is wrapped around by a self-hardening resin to produce, from the matrix52, a resin mold54of a self-hardening resin having a groove15A corresponding to the groove15, as shown inFIG. 10. Note that the resin mold54has holes14A and17A corresponding to the fitting hole14and the slit13s.

Then, a second core80is attached to the groove15A of the resin mold54as shown in step7ofFIG. 10to produce a model55with a portion81of the second core80projecting from the resin mold54as shown in step8ofFIG. 11. Note that the second core80has the shape corresponding to the groove15and the slit13s.

Then, a plaster is poured into the depressed portion of the model55ofFIG. 11and then allowed to set, thereby producing a plaster mold56with the portion81of the second core80integrally buried in the plaster as shown in step9ofFIG. 12A. Note that a generally columnar portion56scorresponding to the hole14A ofFIG. 10is integrally formed with the plaster mold56.

Then, the nylon denture base10is molded from the plaster mold56ofFIG. 12A. Thus, the nylon denture base10ofFIG. 12Bis obtained from the matrix52of the denture base10ofFIG. 9B. Thus, the burden on the dentist and the patient is reduced.

With the denture1thus produced, it is possible to correct or amend the fit of the engagement piece member13to the abutment3in order to enhance the wearability through a procedure as follows.

First, the denture1is worn and used by the patient over a short period of about 1 to 3 weeks or over a long period of some years. Then, the dentist asks the patient of the fit, and the denture1is taken out from the patient, after which the dentist heats the engagement piece members13. With the fit taken into consideration, the heated engagement piece members13are deformed. The deformed engagement piece members13are cooled, after which the denture1is placed back in the patient.

The wearability is improved by repeating the correcting or amending operation.

The improvement of the wearability through the correcting operation is obtained also when only one engagement piece member13ofFIG. 1is provided, or the engagement piece member13is a completely continuous loop ofFIG. 17Bto be described below.

However, where the upper or lower end portion of the engagement piece member13is continuous with the main body12, the engagement piece member13extends in the vertical direction Z from the end portion13aof the engagement piece member13, and the engagement piece member13is provided around the abutment3as a plurality of pieces separated from one another in the circumferential direction of the abutment3, as shown inFIG. 6A, the engagement piece member13can easily be deformed, thereby facilitating the correcting operation and allowing for correction over a wide range.

With the method described above, step6A ofFIGS. 13A and 13Bmay be employed instead of step6ofFIGS. 9A and 9B. That is, a cylindrical groove15B may be formed in the plaster portion51aof the male mold51ofFIG. 13A, and the second part72having a cylindrical body may be inserted into the groove15B.

Steps11to13ofFIGS. 14A to 14Cmay be employed instead of step6ofFIG. 9Ato step10ofFIG. 12B. In such a case, a semi-finished product10A made of a nylon resin ofFIG. 14Bis produced in a state where the first part71of the first core is attached to the male mold51ofFIG. 14A, and the groove15is cut in the semi-finished product10A.

Where a pair of grooves15and a pair of engagement piece members13are provided, a core or a mold shaped as shown inFIGS. 15A and 15Bmay be employed instead of the shape ofFIGS. 9A and 9B. In such a case, the plaster mold56and the denture base10shaped as shown inFIGS. 16A and 16Bare obtained instead of the shapes of the plaster mold56and the denture base10ofFIGS. 12A and 12B.

FIGS. 17A to 19Bshow another embodiment of the production method.

As shown inFIG. 17A, in the state of an intermediate product of the present embodiment, the engagement piece member13has an endlessly continuous cylindrical shape, and there are provided no slits13sconnecting together the circular fitting hole14and the cylindrical groove15.

In the case of this embodiment, the second core80ofFIG. 18is used instead of the second core80ofFIG. 10. The second core80includes a buried portion (portion)81, a columnar portion82to be later buried in the plaster mold56(FIG. 19A) and fitted to the hole14A, a cylindrical portion83to be fitted to the groove15A, and a cover plate84formed integral with one another.

In the case of this embodiment, the plaster mold56and the denture base10shown inFIGS. 19A and 19Bare obtained instead of the plaster mold56and the denture base10shown in step9ofFIGS. 12A and 12BandFIG. 10. Then, as shown inFIG. 19C, the denture base10is processed to have areas to be the slits13s, thereby obtaining the denture base10having the slits13s.

As shown in these figures, the top surface of the abutment3may have a conic shape. On the other hand, the top surface or the bottom surface of the fitting hole14may have a shape that conforms with the top surface of the abutment3.

As shown inFIGS. 27A to 27C, in this embodiment, the engagement piece13P is provided separately from the denture base10. The denture base10and the engagement piece13P are formed by a nylon-based thermoplastic resin of the same type or resins of different types. A coupling layer19of a two-component autopolymerizing resin is interposed between the denture base10and the engagement piece13P, whereby the denture base10and the engagement piece13P are coupled together and formed integral and continuous together.

InFIGS. 27A and 27B, the engagement piece13P is formed in a generally cylindrical shape with a bottom, i.e., a cup shape, having a plurality of (e.g., four) slits13sand engagement piece members13, with a lid portion13cfor coupling together the plurality of engagement piece members13. Note that each engagement piece member13has an engagement element13e.

The lid portion13ccovers the top portion (top)3tof the abutment3. InFIG. 27A, anchor grooves13gand10gare formed in the lid portion13cand an area of the denture base10opposing the lid portion13c. The space between the lid portion13cand the denture base10and the anchor grooves13gand10gare filled with the autopolymerizing resin of the coupling layer19.

Note that the anchor grooves13gof the denture base10are formed in the inner surface of an accommodating depressed portion10c.

A deep hole10hto be the gate for pouring the resin is formed in the denture base10, and the deep hole10his also filled with the resin. Note that the deep hole10hconnects the outer surface of the denture base10with the deep end of the accommodating depressed portion10c.

The accommodating depressed portion10chaving a columnar shape for accommodating the engagement piece13P therein is formed in the denture base10. The accommodating depressed portion10cis defined by the third surface33of the denture base10. The third surface33opposes the second surface32.

Note that the slits13srun through the engagement piece13P in the radial direction from the first surface31to the second surface32.

Next, a method for producing the denture1of the embodiment will be described.

Then, in the order from steps34to40ofFIGS. 22B to 26A, the denture base10having the accommodating depressed portion10cforming the allowance portion15ofFIG. 27Ais formed. The method for forming the denture base10will now be described.

In order to form the denture base10, a second replica61of the abutment3is attached to a first replica60buried in the male mold51as shown inFIG. 23Ain step34shown inFIG. 22Bfollowing step3. At the time of this attachment, the engagement piece members13of the engagement piece13P are elastically deformed to engage with the engaged groove3eof the abutment3. Then, in step35ofFIG. 23B, the engagement piece13P is fitted to the second replica61. In this state, the gap S to be an undercut is present between the engagement piece13P and the male mold51.

After the fitting, as shown in step36ofFIG. 24A, a core90is arranged around the engagement piece13P in order to form the allowance portion15(FIG. 27A) of the engagement piece member13. In this example, the core90is formed by a wax covering the lid portion13cand the circumference of the engagement piece13P and filling the gap S. Thus, the male mold51having the shape of the projecting portion15P corresponding to the allowance portion15and the shape of the oral cavity is produced from the female mold50ofFIG. 22A.

Note that the core90may be formed by a cup-shaped metal or resin core covering the circumference of the engagement piece13P and the lid portion13c, and the filler (wax)53filling the gap S below the engagement piece13P.

The wax forming the core90serves also as the filler53filling the gap (undercut) S formed on the surface between the engagement piece13P and the male mold51. The wax forming the core90fills the anchor groove13gformed in the lid portion13cof the engagement piece13P.

The outer surface of the core90(the projecting portion15P) thus formed has a generally columnar shape.

After the core90is formed, a plaster mold56A shown in step37ofFIG. 24Bis obtained from the male mold51ofFIG. 24A. The denture base10having the artificial tooth11is obtained by using the plaster mold56A and a well-known female mold (not shown). That is, the denture base10having the shape of the hole1511forming the allowance portion15is obtained from the male mold51.

Then, the denture base10ofFIG. 24Bis removed from the plaster mold56A, and the anchor grooves10gand the deep hole10hare formed in the denture base10as shown in step38ofFIG. 25A.

On the other hand, an area of the wax corresponding to the lid portion of the male mold51obtained in step36ofFIG. 24Ais removed as shown in step39ofFIG. 25B, thereby exposing the lid portion13cof the engagement piece13P. Then, as shown in step40ofFIG. 26A, the denture base10obtained in24B described above is attached to the engagement piece13P, which has been exposed as some wax has been removed.

In the state shown inFIG. 26A, a gap19scorresponding to the coupling layer19is formed between the engagement piece13P and the denture base10. Then, as shown in step41ofFIG. 26B, a well-known two-component autopolymerizing resin is poured into the gap19sand the anchor grooves10gand13gthrough the deep hole10h.

As the polymerizing resin sets, the denture base10and the engagement piece13P become integral with each other with the coupling layer19interposed therebetween while the engagement piece13P and the denture base10are spaced apart from each other over the allowance portion15. That is, the denture base10and the engagement piece13P become integral with each other with the coupling layer19interposed therebetween while ensuring a moving range of the engagement piece member13by virtue of the remaining portion of the core70. After the polymerizing resin sets, the denture base10integral with the engagement piece13P is removed from the male mold51, thus obtaining the denture1ofFIG. 27A.

The denture1thus produced by the technician is placed in the oral cavity of the patient so that the fitting hole14of the engagement piece13P fits over the abutment3while the denture base10is in contact with the gum40as shown inFIG. 27C.

At the time of this attachment, the engagement piece members13of the engagement piece13P are elastically deformed to engage with the engaged groove3eof the abutment3.

FIGS. 28A to 29Bshow other examples of the denture1.

In the examples ofFIGS. 28A and 28B, the engagement piece member13and the denture base10are formed by a nylon-based thermoplastic resin, and the lid portion13cof the engagement piece13P and the denture base10are welded with each other in the accommodating depressed portion10c. In these examples, the coupling step is performed by welding the engagement piece13P and the denture base10with each other.

Such welding may be done by induction heating using a high frequency. In addition to the welding, the engagement piece13P and the denture base10may be engaged with each other as shown inFIG. 28B.

In the example ofFIG. 29Aor29B, the engagement piece member13is held by being directly or indirectly engaged with the denture base10. In these examples, the coupling step is performed by directly or indirectly engaging the engagement piece13P and the denture base10with each other.

In the examples ofFIGS. 29A and 29B, a cushion16K such as a silicone gel may be inserted between the lid portion13cof the engagement piece13P and the denture base10.

Note that inFIG. 29B, the engagement piece13P and the denture base10are engaged with each other with a C-shaped engagement ring19R therebetween.

FIG. 30is a perspective view of a model showing an arrangement of the abutments3with respect to the oral cavity.

In this figure, a pair of abutments301and302arranged on the back side has their axial lines301sand302sparallel to each other. A pair of abutments303and304arranged on the front side has their axial lines303sand304sparallel to each other. However, the axial lines301sand302sof the abutments301and302and the axial lines303sand304sof the abutments303and304are not parallel to each other but are arranged in a skew relationship with respect to each other.

In such a case, the engagement piece members13of the present denture system elastically deform, thereby enabling the realization of the denture1which fits to the four abutments301to304.

In such a case, the denture1having a plurality of engagement piece members13and the denture1having a structure shown inFIGS. 4A and 4Bhave high applicability.

In the example to follow, a closed tray21A is used instead of the open tray21having a window.

FIGS. 31A to 33Dshow an example of the production method.

First, as shown in step51ofFIG. 31A, the dentist produces the female mold50of the oral cavity, with the fixture2buried therein and the abutment3coupled to the fixture2, by using the tray21A and a flexible impression material23(self-hardening resin) according to a well-known method. As the impression material23cures, the tray21A and the impression material23are removed from the oral cavity, thus obtaining the female mold50.

A plaster is poured into the obtained female mold50and the plaster sets, thereby producing the male mold51having the shape of the abutment3shown in step52ofFIG. 31Band the shape of the oral cavity.

Note that since the impression material23is flexible, the female mold50and the male mold51can be released from each other even with the engaged groove3ein the abutment3.

Next, as shown inFIG. 32B, the cylindrical core70is attached over an area51bof the male mold51corresponding to the abutment. While the core70is formed by, for example, a metal such as stainless, Teflon or ceramic, it is preferred to use a material that has a good heat resistance in the molding process and that can easily be released from the denture base10.

As shown inFIGS. 32A and 32B, the core70includes a cylindrical portion72A having a cylindrical shape, and a plurality of blade portions71A provided at positions corresponding to the slits13sand extending from the inner circumferential surface of the cylindrical portion72A toward the center of the cylindrical portion72A. The blade portion71A forms a part of the slit13sin the step of obtaining the denture base10to be described later.

The end of each blade portion71A on the inner circumference side is close to, or in contact with, the area51b.

An end face70eof the core70on one side (the lower side in the figure) in the vertical direction that opposes the male mold51is in contact with an area51ccorresponding to the ridge of the gum, thereby forming the gap S to be an undercut between the end face70eof the core70and the surface of the male mold51, but the gap S is filled with the filler53to produce the matrix52in the present embodiment. In the present embodiment, the filler53may preferably be, for example, a ceramic material, such as a plaster, which can be easily molded and broken, and which can withstand the heat during the process of molding the denture base10.

Then, an intermediate product of the denture base10having the artificial tooth11shown in step54ofFIG. 32Cis molded by a well-known method from the matrix52. After the nylon of the denture base10sets, the male mold51and the filler53are crushed, and moreover the core70is pulled out of the intermediate product of the denture base10.

Thus, an intermediate product of the denture base10shown inFIGS. 33A and 33Bis obtained. The intermediate product includes a groove130formed therein to be a part of the slit13s.

Then, in the area of the groove130, the slit13sofFIG. 33Cis formed so that the fitting hole14and the allowance portion15are connected with each other. The slit13sserves to make it easier for the engagement piece members13and13to be deformed independently of each other.

Thus, the nylon denture base10ofFIG. 33Cis obtained from the female mold50ofFIG. 31A. Thus, the burden on the dentist and the patient is reduced.

FIGS. 34A to 36Cshow the structure and the production method of Embodiment 11.

In this example, a plurality of longitudinal grooves3gare included on the abutment3.

As shown inFIGS. 34A and 34B, the abutment3or a replica3R thereof having a shape similar to that of the abutment3includes a male screw portion3sto be screwed into a female screw2sof the fixture2, and a top3tprojecting from the fixture2over which the denture1is fitted through the fitting hole14. Note that the top3tis the upper end portion of the abutment3for the lower jaw, and the lower end portion of the abutment3for the upper jaw.

InFIG. 36C, the abutment3is provided with a cylindrical or spherical outer surface over which the denture base10and the engagement piece members13are fitted. Formed on the side surface of the abutment3are an engaged groove3eand two, three or four longitudinal grooves3g.

InFIG. 36C, the engaged groove3eis formed in a circumferential shape between the top3tand the male screw portion3s. The engaged groove3eis formed in a narrowed shape with which the engagement piece members13engage. The longitudinal grooves3gare provided on the side surface of the abutment3, and extending from the top3ttoward the male screw portion3s, with the depth thereof being generally equal to or greater than that of the engaged groove3e. The longitudinal grooves3gare spaced apart from one another in the circumferential direction, and the number of longitudinal grooves3gis the same as the number of slits13s.

InFIG. 34B, the abutment3or the replica3R is provided with the cylindrical outer circumferential surface39at a position closer to the fixture2. The cylindrical outer circumferential surface39has an outer diameter that is greater than the outer diameter of the top3twhich projects from the fixture2and over which the denture1is fitted through the fitting hole14and that is smaller than the outer diameter of the fixture2.

A C-shaped or ring-shaped positioning portion79is formed integral with a cylindrical portion71A at the lower end portion of the cylindrical core70ofFIGS. 35A and 35B. The positioning portion79is for positioning the core70with respect to the male mold51by being fitted over, while being in contact with, an area519of the male mold51corresponding to the cylindrical outer circumferential surface39(FIG. 34B).

In the present embodiment, steps61to64ofFIGS. 34A to 35Care performed as are steps51to54ofFIGS. 31A to 32Cof the embodiment described above, thereby molding the denture base10ofFIG. 35C.

In step62of producing the male mold51ofFIGS. 34C and 34Dof the present embodiment, the longitudinal groove51g, into which the projecting end of the blade portion71A ofFIG. 35Afits and which allows for up and down movement of the blade portion71A when attaching the core70, is formed in an area of the male mold51corresponding to the abutment, and in the attachment step shown inFIGS. 35A and 35B, the blade portion71A of the core70is attached in the vertical direction Z along the longitudinal groove51g. In this process, the core70is attached to the male mold51while the positioning portion79is fitted over the area519corresponding to the cylindrical outer circumferential surface39(FIG. 34B).

Thus, since the blade portion71A of the core70is fitted into the longitudinal groove51gand also the positioning portion79is fitted over the area519, the core70and the male mold51are unlikely to be positionally shifted. Therefore, the area formed by the filler53is unlikely to be positionally shifted with respect to the male mold51.

Note that the blade portion71A of the core70of the present embodiment extends in the vertical direction Z and goes into the deepest portion of the engaged groove3eof the abutment3, forming the entire portion of the slit13s(FIG. 36A).

In the present embodiment, after the nylon resin is cured inFIG. 35C, the male mold51and the filler53are crushed, and moreover the core70is pulled out of the denture base10, thus producing the denture1shown inFIGS. 36A and 36B. Therefore, there is no need to produce, by processing, the slits13safter the molding process.

As shown inFIG. 36A, in this embodiment, three slits13sare provided. The slits13sextend in the radial direction of the abutment3so as to separate the engagement piece members13from one another in the circumferential direction. With respect to the abutment3, the engagement piece member13extends in the circumferential direction of the abutment3as shown inFIG. 36Aalong the side surface of the abutment3ofFIG. 36Cover a range of the center angle θ less than 180°.

Since the number of engagement piece members13is typically preferably two to four, the center angle θ is preferably greater than 60° and less than 180°.

While the engagement piece members13are deformed to flare out, as if by pivoting about the end portion13aofFIG. 36B, when attaching/detaching the denture1, if the center angle θ is greater than 180°, the flexural rigidity will be high and they will not easily be deformed.

On the other hand, if the center angle θ is less than 60°, the force of holding the abutment3by the engagement piece member13will likely be insufficient.

In the present embodiment, the abutment3ofFIG. 36Cdoes not always need to be provided with the longitudinal groove3gand/or the positioning portion79, and the replica3R of the abutment3ofFIG. 34Bmay be provided with the longitudinal groove3gand/or the positioning portion79. For example, without providing the abutment3with the longitudinal groove3gand the positioning portion79, the dentist attaches, by screwing, the replica3R having the longitudinal groove3gand/or the positioning portion79, instead of the abutment3, to the fixture2, and produces the female mold50ofFIG. 34Bwith the replica3R attached.

Thus, where the artificial tooth11is produced by using the replica3R having the longitudinal groove3g, the longitudinal groove3gdoes not need to be formed on the abutment3as shown inFIG. 38C, and an existing abutment3having a hole on the top3t, which engages with a tool, can be used.

On the other hand, where the abutment3having the longitudinal groove3gis used, the longitudinal groove3gof the abutment3serves as a groove to be engaged with a tool when screwing the abutment3into the fixture2. Therefore, there is no need for the engaging hole of the existing abutment3, resulting in a large surface area on the top3tover which the abutment3is in contact with the denture base10.

FIGS. 37A to 38Cshow still another embodiment. In this embodiment, the core70ofFIG. 37Ais divided in the radial direction into a plurality of pieces. The divided cores70D can be brought closer in the radial direction toward and attached to the area51bof the male mold51ofFIG. 37Bcorresponding to the abutment.

Note that after the attachment, the divided cores70D and70D may be put together by a bond or an adhesive.

FIGS. 39A to 40Dshow a general-purpose embodiment. While the height of the core70may be lower than, or higher than, the abutment3in the embodiments ofFIGS. 1A to 38Cdescribed above, the height of the cylinder to be the core70is set to be high in advance in the embodiment ofFIG. 39A.

InFIG. 39A, the core70is cut off along a phantom line denoted by a two-dot-chain line so as to remove an upper portion thereof in advance. The core70of the present embodiment has no blade portion71A, and therefore the slits13sofFIGS. 40C and 40Dare formed by processing after the molding process in a cylindrical area130ofFIGS. 40A and 40B.

In this example, a plurality of projections3pare formed integrally on the side surface of the abutment3or the replica3R thereof. The projections3pextend from the top3ttoward the male screw portion3s(FIG. 34B), and have a greater height than the depth of the engaged groove3e, and a number of projections3pequal to the number of the slits13s(FIG. 40C) are provided while being spaced apart from one another in the circumferential direction.

In this example, the male mold51ofFIGS. 41C and 41Dis produced by removing the female mold50as shown inFIG. 41B. Projections51pcorresponding to the projections3pare formed integrally on the male mold51. The cylindrical core70is attached to the male mold51, and then the denture1is produced through steps63to65ofFIGS. 35B to 36B.

In this example, the core70needs no blade portion71A.

In this example, the positioning portion79is formed integrally on the lower end portion of the core70. The positioning portion79is in contact with, or close to, the circumference of the area51bof the male mold51corresponding to the abutment so as to position the core70in the radial direction. The positioning portion79will also facilitate the filling with the filler53.

FIGS. 43 to 46Cshow a fabrication method in a case where there is one engagement piece member13.

InFIG. 43, the core70includes the positioning portion79, the first part71having a curved plate shape, and a pair of blades73. The ring-shaped positioning portion79has the function of holding the core70attached to the male mold51as shown inFIG. 45A.

In the present embodiment, a denture is produced as will be described below by using the replica3R of an abutment having a pair of longitudinal grooves3gcorresponding to a pair of blades73.

In the present embodiment, steps111to116ofFIGS. 44A to 46Care performed as are steps61to66ofFIGS. 34A to 35Cof the embodiment described above, thereby molding the denture base10ofFIG. 46C.

Now, in the present embodiment, an area of the male mold51corresponding to the engaged groove3eof the abutment is filled with a ceramic filler300such as a plaster as shown inFIG. 45A. This makes it possible to attach/detach the denture base10to the abutment3in such a manner that the denture base10ofFIG. 46Cdoes not engage with the engaged groove3e.

In a reference embodiment ofFIG. 47, a plurality of (preferably, three or four) engagement piece members13formed integrally with the denture base10are fitted into an engaged depressed portion3cformed inside the abutment3. As compared with the reference embodiment, the present invention is advantageous in that a stable fit is likely to be obtained since the engagement piece members13engage with the outer circumferential surface of the abutment3.

As shown inFIGS. 48A and 48C, the present denture system includes the denture1, the fixture2, and the columnar abutment3.

As shown inFIG. 50, the fixture2is a so-called “implant body”, an artificial tooth root obtained by performing a surface process (surface finishing) on a biomaterial (a typical material being titanium, which is well compatible with a living body). The fixture2is buried in the oral tissue4such as an alveolar bone41of the jaw to be integrated with the bone.

The abutment3is coupled to the fixture2and exposed in the oral cavity. That is, the abutment3is fixed to the fixture2ofFIG. 50with a screw ofFIG. 51Cand is coupled to the fixture2so that the artificial denture1can be attached thereto.

As shown inFIGS. 48A and 48C, the denture1is detachably attached to the abutment3. The denture1includes the nylon-made denture base10to be in contact with the gum40, and ceramic artificial teeth11integral with the denture base10and supported by the denture base10.

For example, a pair of the fixtures2and the abutments3is provided in the oral cavity and the present system is applied to the pair of the fixtures2and the abutments3.

The artificial teeth11are secured to one end of the denture base10in the vertical direction Z. The other end surface of the denture base10in the vertical direction Z is softly in contact with the gum40.

As shown in the enlarged cross-sectional view ofFIG. 50, the denture base10includes a main body12and the engagement piece members13integrally continuous with each other, and defines the fitting holes14into which columnar abutments3are detachably fitted. The engagement piece members13and the denture base10are formed by a nylon-based thermoplastic resin, for example.

The fitting holes14are open toward the gum40. That is, the fitting holes14of an upper denture1are open in the upward direction, and the fitting holes14of a lower denture1are open in the downward direction.

As shown inFIG. 50, the engagement piece members13form the fitting hole14. That is, as clearly shown inFIG. 51B, the fitting hole14is defined by a plurality of the engagement piece members13. The fitting hole14positions and fixes the denture base10with respect to the abutment3. The engagement piece member13has a first surface31to be in contact with and engaging with the side surface of the abutment3, and a second surface32opposite to the first surface31.

In the present embodiment, where the denture1is placed in the lower jaw, the upper end portion13aof the engagement piece member13ofFIG. 50is continuous with the denture base10, and the engagement piece member13extends downwardly in the vertical direction Z from the end portion13aof the engagement piece member13.

Note that although not shown, in a case where the denture1is placed in the upper jaw, the lower end portion of the engagement piece member13is continuous with the main body12, and the engagement piece member13extends upwardly in the vertical direction Z from the end portion of the engagement piece member13.

In the present embodiment, an engagement element (engagement protrusion)13eto be engaged with the narrowed engaged groove (engaged element)3eof the abutment3is formed integrally with the engagement piece member13at the lower end of the engagement piece member13. As the engagement element13eis engaged with the engaged groove3e, the denture1is prevented from inadvertently coming off the abutment3.

The denture base10ofFIG. 51Cincludes the allowance portion15formed between the second surface32and the third surface33, wherein the allowance portion15allows the engagement piece member13to move or deform in the horizontal direction X from the first surface31toward the second surface32. The allowance portion15is provided as a groove15formed in the denture base10. The third surface33is spaced apart from, and opposing, the second surface32.

The groove15ofFIG. 51Ais continuous with the fitting hole14via the slit13s, thereby facilitating the movement of the engagement piece member13. When placing/removing the denture1, the engagement piece member13retracts toward the groove15, thereby allowing the denture1to be attached/detached to/from the abutment3.

The denture base10may include a cushion portion16formed at the deep end in the vertical direction Z of the fitting hole14ofFIG. 50. The cushion portion16is formed by a plurality of small projections or ridges, and the projections or the ridges will provide the denture1with cushioning in place of the natural periodontal membrane by elastically deforming when clenching the teeth.

The denture base10made of a nylon-based resin will unlikely deteriorate and will unlikely whiten over years of use. Moreover, the denture base10of such a material will unlikely lose the elasticity of the engagement piece member13. Particularly, when the engagement piece member13deteriorates due to permanent deformation, lowering of elasticity, etc., it will be possible to restore the engagement piece member13while heating, with a hot air, the engagement piece member13and the denture base10around the fitting hole14.

In this case, the engagement piece members13ofFIG. 51Aare provided in a state in which the engagement piece member13is divided into four parts. The four divided engagement piece members13are almost cylindrical shape as a whole and extend from the denture base10in the up-down direction Z. Note: the engagement element13emay be formed by a small protrusion integral with the first surface31.

The abutment3ofFIG. 51Cdefines, between the top3tand the male screw portion3s, a narrowed circumferential engaged groove3ewith which the engagement piece members13engage. The abutment3comprises the male screw portion3sto be screwed into the fixture2(FIG. 48) and the through hole3hinto which the male screw portion3s.

FIG. 49is a perspective view of a model showing an arrangement of the abutments3with respect to the oral cavity.

In this figure, a pair of abutments301and302arranged on the back side has their axial lines301sand302sparallel to each other. A pair of abutments303and304arranged on the front side has their axial lines303sand304sparallel to each other. However, the axial lines301sand302sof the abutments301and302and the axial lines303sand304sof the abutments303and304are not parallel to each other but are arranged in a skew relationship with respect to each other.

In such a case, the engagement piece members13of the present denture system elastically deform, thereby enabling the realization of the denture1which fits to the four abutments301to304. In this case, the denture1ofFIG. 48having a plurality of engagement piece members13has high applicability.

The engagement element13eof the engagement piece member13rubs against the abutment3every time the denture1ofFIG. 50is attached or detached. Therefore, it is preferred that the engaged groove3eis formed in a smooth shape.

Next, the nylon-based engagement piece13P ofFIG. 51AandFIG. 51Cthat is principal part of the present invention will be described in detail.

The engagement piece13P is integrally formed by a lid portion13c, engagement piece portions13, an outer portion13r, and cushion portions16, and defines an allowance portion15.

The number of the engagement piece members13is three or four, for example. The engagement piece members13extend from the lid portion13cin an up-down direction Z. The engagement piece members13elastically deform to spread around an end portion13ain the up-down direction Z when attaching and detaching the denture1, and engage with the abutment3when worn. The engagement piece members13are spaced apart from one another via slits13sin a circumferential direction.

The outer portion13ris a cylindrical shape, for example. The outer portion13rhas a third surface33extending in the up-down direction Z from a circumference of the lid portion13cand being further from an axis3L of the abutment3than the second surfaces32of the engagement piece members13. As shown inFIG. 50, the outer portion13ris joined to the body part12of the denture base10after molding the denture base10. The outer portion13rsandwiches a tubular member between the outer portion13rand the engagement piece member13, thereby securing the allowance portion15between the second surface32and the third surface33.

The allowance portion15ofFIG. 51Callows the engagement piece members13to be elastically deformed to spread in a direction from the first surface31toward the second surface32. The allowance portion15is defined between the second surface32and the third surface33of the outer portion13r.

Note: an engagement concave132or a small through hole that is used for ensuring the engagement between the outer portion13rand the body portion12may be provided on the fourth surface34of the outer portion13r.

The lid portion13ccovers an entire surface of the top3tof the abutment3and is covered by the body part12(FIG. 50) of the denture base10. The lid portion13ccloses one end, in the up-down direction Z, of the fitting hole14defined by the engagement piece members13and closes one end, in the up-down direction Z, of the allowance portion15.

As shown inFIG. 50, the lid portion13cand the outer portion13rare integrated with the body portion12, forming a part of the denture base10.

The cushion portion16ofFIG. 51Cprojects toward the abutment3at an area of the lid portion13ccorresponding to the outer circumferential edge of the top3tof the abutment3and inside the engagement piece members13. The cushion portion16may be formed by a plurality of arc-shaped cushion portions16ofFIG. 51Aor a circular shape cushion portion16.

That is, the cushion portion16projects toward the abutment3ofFIG. 51Cinside the engagement piece members13and contacts with the outer circumferential edge of the top3toutside the through hole3h.

The outer circumferential edge of the top3thas a conic tapered surface3fin which the edge is closer to the fixture2(FIG. 48) as the edge is closer to the outer end of the top3t. The cushion portion16contacts with the abutment3on the tapered surface3f.

The engaged groove3eis formed so as to be longer than the engagement element13ein the direction of the axis3L. Thereby, the engagement piece13P slightly moves up and down with respect to the abutment3in accordance with the deformation of the cushion portion16when clenching teeth.

A ratio of pigment to resin forming the engagement piece13P is set to be from 0 weight percent to 0.07 weight percent. Therefore, a ratio of the pigment contained in the resin forming the engagement piece13P is smaller than a ratio of pigment contained in resin forming the body part12of the denture base10(0.1 weight percent to 0.20 weight percent).

Next, a method for producing the denture1(FIG. 50) will be described.

FIG. 52A to 57Bshows an example of the method.

First, as shown inFIG. 52A, a dentist produces, according to a well-known method, a female mold50of the oral cavity by using a tray21A and a soft impression material23(silicon resin (including silicon rubber)). The fixture2is buried in the mold50and the abutment3is connected with the fixture2. After the impression material23is solidified, the tray21A and the impression material23are removed from the oral cavity, thereby obtaining the female mold50. The subsequent steps are performed by a dental technician rather than a dentist.

As shown inFIG. 52B, a replica3R of the abutment3(not abutment3itself) is installed to the female mold50.

As shownFIG. 53A, the dental technician pours a plaster51ainto the concave portion of the impression material23in order to make a male mold51of the impression material23. Thus, the male mold51, having the replica3R of the abutment2projected therefrom and having the shape of the oral cavity, is produced from the female mold50. Then, as shown inFIG. 53B, the engagement piece13P made by a nylon is fitted to the replica3R of the male mold51. The engagement piece13P contains no pigment.

Now, although a gap S to be an undercut in the molded product is formed between the lower end of the engagement piece13P and the surface of the male mold51, as shown inFIG. 54A, the shape of the male mold51is corrected by filling the gap S with the filler53. Note that a wax may be employed as the filler53, for example.

Then, as shown inFIG. 54B, the replica3R, the filler53and the plaster51aare removed from the female resin form54after wrapping the male mold51with a self-hardening resin (impression material like silicon resin). Thus, as shown inFIG. 55A, the female resin mold54that the engagement piece13P is buried in is produced. The mold54has the depressed portion500corresponding to the shape of the oral cavity4.

Thereafter, the restraint member R formed of a metallic pipe is inserted into the allowance portion15of the engagement piece13P of the female resin mold54shown inFIG. 55B. The restraint member R is inserted into the allowance portion15and works as a core when molding the body part12of the denture base10. Therefore, the outer portion13ris prevented from deforming (moving) toward the engagement piece members13when molding the body part12of the denture base10.

After the insertion of the restraint member R, as shown inFIG. 56A, plaster is poured into the depressed portion500of the female resin mold54. Thereby, the male plaster mold56is produced. The restraint member R is buried in the plaster of the mold56, and the engagement piece13P is integral with the mold56.

The molten resin made of nylon containing 0.10 to 0.20 weight percent of pigment is injected between the male plaster mold56and a well-known female mold of a denture1(not shown), thereby molding the body part12of the resin denture base10ofFIG. 57Aas well as producing the denture base10in which the body part12of the denture base10is integral with the engagement piece13P. After the body part12is solidified, the plaster of the male plaster mold56and the restraint member R is removed.

Therefore, not only a dentist's and a patient's burden will be reduced, but also work of forming the allowance portion15by a dental technician will remarkably be simple and easy.

In this embodiment, the restraint member R may be a cup-like resin having a cylindrical portion to be inserted into the allowance15or may be a piece of rubber, instead of a metallic pipe.

As shown inFIG. 58A, in this embodiment, the body part12of the denture base10is formed by resin, such as polycarbonate, acryl resin, or polyester, different from the resin of the engagement piece13P. A coupling layer19of a two-component autopolymerizing resin is interposed between the body part12of the denture base10and the engagement piece13P, whereby the denture base10and the engagement piece13P are coupled together and formed integral and continuous together.

InFIG. 58A, the engagement piece13P is formed in a generally cylindrical shape with a bottom, i.e., a cup shape, having a plurality of (e.g., four) slits13sand engagement piece members13inside the outer portion13r, with a lid portion13c. The lid portion13ccouples together the plurality of engagement piece members13. Note that each engagement piece member13has an engagement element13e.

The lid portion13ccovers the top portion (top)3tof the abutment3. The anchor grooves13gand10gare formed in the lid portion13cand an area of the body portion12of the denture base10opposing the lid portion13c. The space between the lid portion13cand the body part12of the denture base10and the anchor grooves13gand10gare filled with the autopolymerizing resin of the coupling layer19.

Note that the anchor grooves13gof the body part12of the denture base10are formed in the inner surface of an accommodating depressed portion10c.

A deep hole10hto be the gate for pouring the resin is formed in the denture base10, and the deep hole10his also filled with the resin. Note that the deep hole10hconnects the outer surface of the denture base10with the deep end of the accommodating depressed portion10c.

The accommodating depressed portion10chaving a columnar shape for accommodating the engagement piece13P therein is formed in the body part12of the denture base10.

Note that, as shown inFIG. 51A, the slits13srun through the engagement piece13P in the radial direction from the first surface31to the second surface32.

The method of this embodiment for producing a denture1is disclosed in the paragraphs 0087 to 0098 andFIG. 21AtoFIG. 27Cof WO 2012/132819A1, and the entire contents of these disclosures and descriptions are hereby incorporated herein.

InFIG. 58B, the outer portion13rof the present embodiment has the third surface33that is a part of the recessed cylindrical surface (not a complete cylindrical shape), and is divided into the plural. On the other hand, the engagement piece members13do not oppose to the outer portions13r, and the engagement piece members13and the outer portions13rare alternately placed in the circumferential direction. In this case, the restraint member R is still supported by being sandwiched between the outer portions13rand the engagement piece member13. Therefore, the allowance portion15(FIG. 50) is able to be formed toward which the engagement piece members13deform.

Note that the outer portions13rmay be formed by a plurality of pins (round bars) integral with the lid portion13c. In this case, a surface of the pin forms the third surface33.

In the embodiment ofFIG. 58D, there are no the outer portions13r. In this embodiment, the second surface32of the plurality of the engagement piece members13ofFIG. 58Eis formed so as to be slightly widened from the lid portion13ctoward the tip. On the other hand, the tip portion of the engagement piece member13is formed so as to be slightly tapered toward the tip. Therefore, when the cylindrical restraint member R is externally fitted to the outer circumference of the second surface32of the engagement piece members13, the restraint member R is held around the engagement piece members13because of elasticity of resin of the engagement piece members13.

In order to position the restraint member R in the direction of axis3L, it is preferred that a flange139is provided with the lid portion13c. The flange139protrudes more outward than the second surface32of the engagement piece members13.

Note that in the embodiments ofFIG. 58BtoFIG. 58E, if release agent is applied over the outer surface of the metallic restraint member R, the restraint member R will easily be removed from the body part12of the denture base10when producing the denture1.

Now, in the embodiments ofFIG. 58BtoFIG. 58E, the allowance portion15is not formed in the process ofFIG. 54Bbecause the impression material23contacts with the engagement piece members13. Therefore, the denture1is produced in accordance with the following process.

In this case, after the process ofFIG. 52AtoFIG. 53B, a circular tube restraint member R is externally fitted over the engagement piece members13. Therefore, the allowance portion15is secured.

That is, in these embodiments, after the process ofFIG. 52AtoFIG. 53B, a tubular member R1is externally fitted to the outer circumference of the engagement piece members13of the engagement piece inFIG. 54A. The tubular member R1is provided in order to form the allowance portion15that allows the engagement piece member13to elastically deform. Thereafter, after the similar process ofFIG. 54AtoFIG. 55B, a female resin mold54is produced. The mold54has a depressed portion500that the engagement piece13P and the tubular member R1are buried in and corresponds to the shape of the oral tissue4.

Thereafter, as with the process ofFIG. 56AandFIG. 56B, plaster is poured into the depressed portion500of the female resin mold54, producing a male plaster mold56in which the tubular member R1and the engagement piece13P are integral with the plaster. Thereafter, as with the process ofFIG. 57A, molten resin containing pigment is injected around the male plaster mold56, producing the denture base10in which the engagement piece13P is integral with the body portion12of the denture base10. After the production, as with the process ofFIG. 57B, the plaster of the male plaster model56and the tubular member R1are removed, and the denture1is produced.

In the engagement piece13P of these embodiments, the outer portion13rfurther comprises at least one restraint portion. The outer portion13ris prevented from deforming toward the engagement piece members13when molding the body part12of the denture base10, thereby restraining the allowance portion15from being compressed by pressure when molding the body part12(FIG. 50) of the denture base10.

In the embodiments ofFIG. 59AtoFIG. 59C, the restraint portion is formed by the rib131restraining the outer portion13rfrom falling (coming) toward the engagement piece member13. The rib131is provided at a corner formed by the lid portion13cand the outer portion13rin the slit13s.

In the engagement piece13P ofFIG. 60AandFIG. 61A, the shape of the third surface33of the outer portion13ris round shape in a plane section, and the shape of the fourth surface34, opposite to the third surface33, of the outer portion13ris quadrangle shape or hexagonal shape in a plane section. Each corner34cof the quadrangle shape or hexagonal shape forms the restraint portion.

Note that, inFIG. 61A, a plurality of pins are provided in a circumference as the cushion portions16.

FIG. 62Bshows the engagement piece13P and the tubular member R1. The tubular member R1comprises: the base101that covers the circumference of the engagement piece member13and is to be the allowance portion; and the skirt102protruding from the base101in the axis direction of the tubular member R1. The engagement piece13P of this embodiment has a similar structure to the engagement piece13P ofFIG. 58DandFIG. 58E. The difference between the structure of the engagement piece13P ofFIG. 62CtoFIG. 62Dand that ofFIG. 58DtoFIG. 58Eis that the engagement piece13P ofFIG. 62CtoFIG. 62Dis provided with the continuous portion13P1in which the upper parts of the engagement piece members13are cylindrically continuous with each other. Note that the tubular member R1does not melt by molding heat as well as has the strength enabling the member R1not to be depressed by pressure when molding.

In this embodiment, the denture1is produced in accordance with the following process.

As with the description above, after the process ofFIG. 52A,FIG. 52BandFIG. 53A, as shown inFIG. 62A, the male mold51in which the replica3R protrudes from the plaster is produced. Exposed part of the replica3R has the same shape as the abutment3ofFIG. 50.

On the other hand, the tubular member R1is externally inserted into around the engagement piece members13of the engagement piece13P. On this occasion, the state that the tubular member R1is held on the engagement piece members13is maintained because of elasticity of resin of the engagement piece members13.

Next, as shown inFIG. 63A, the engagement piece13P is fitted to the replica3R. In the piece13P, the tubular member R1ofFIG. 62Bis externally fitted to the male mold51ofFIG. 62A. Thereby, the engagement element13eof the engagement piece13P is engaged with the groove3eof the replica3R.

Note the height of the tubular member R1is set so that the lower end of the skirt102closes to the plaster of the male mold51.

After the external engagement described above, as shownFIG. 63B, the tubular member R1is moved in the axis direction of the replica3R so that the lower end of the skirt102contacts the plaster. Note that although a slight (tiny) gap is formed between the skirt102and the plaster, the gap is filled with plaster (not shown).

Molten resin made of nylon containing 0.10 to 0.20 weight percent of pigment is injected into between the male mold51and a well-known female mold (not shown) of a denture1, thereby molding the resin body part12of the denture base10ofFIG. 64Aas well as producing the denture base10in which the engagement piece13P is integral with the body part12of the denture base10. After the body part12is hardened, the plaster of the male mold51and the tubular member R1are removed.

FIG. 65Bshows the engagement piece13P and the tubular member R1. In this embodiment, the skirt102is slidable in the up-down direction with respect to the base101of the tubular member R1. Furthermore, an end of the skirt102contacting the plaster may be in wave shape so that it becomes easy for the end to be along oral shapes of many patients.

In this embodiment, the tubular part R1may be formed of metallic pipe such as copper pipe and steel pipe. Note that, in this embodiment, the continuous portion13P1ofFIG. 62Cis not provided. The other structure is the same as the embodiment ofFIG. 62BtoFIG. 62D.

In this embodiment, the denture1is produced in accordance with the process described as follows.

As with the description above, after the processes ofFIG. 52A,FIG. 52B, andFIG. 53A, as shown inFIG. 65A, the male mold51in which the replica3R protrudes from the plaster part51ais produced.

On the other hand, the tubular member R1is externally inserted into around the engagement piece members13of the engagement piece13P. On this occasion, the state that the tubular member R1is hold on the engagement piece members13is maintained because of elasticity of resin of the engagement piece members13.

Next, the engagement piece13P is fitted to the replica3R, as shown inFIG. 66A, with the tubular member R1ofFIG. 65Bexternally fit to the male mold51ofFIG. 65A. Thereby, the engagement element13eof the engagement piece13P is engaged with the groove3eof the replica3R.

On this occasion, the skirt102slides with respect to the base101in the axis direction of the replica3R, and then the tip of the skirt102contacts with the plaster part51aof the male mold51. Thereafter, a gap formed between the skirt102and the plaster51ais filled with plaster (not shown).

Note that the base101and the skirt102are fixed with each other by adhesive or sticker.

Molten resin made of nylon containing 0.10 to 0.20 weight percent of pigment is injected into between the male mold51and a well-known female mold (not shown) of a denture1, thereby molding the resin body part12of the denture base10ofFIG. 66Bas well as producing the denture base10in which the engagement piece13P is integral with the body part12of the denture base10. After the body part12is hardened, the plaster part51aof the male mold51and the tubular member R1are removed.

In the embodiment ofFIG. 62AtoFIG. 66B, the number of process remarkably decreases, and thereby work forming the allowance portion15by a dental technician becomes more simple and easier.

While preferred embodiments have been described above with reference to the drawings, various obvious changes and modifications will readily occur to those skilled in the art upon reading the present specification.

For example, the cushion portion may not be provided.

The denture1may be a partial denture.

The following structure may be employed: a depressed portion as an engagement element13eis formed in an engagement piece member13, and a ridge as an engaged groove3eis formed in an abutment3.

Therefore, such changes and modifications shall be deemed to fall within the scope of the present invention.

Industrial Applicability

The present invention can be applied to dental treatment.

Reference Signs List

18: Buried material