Patent Application
20200046458
The present invention relates to an endodontic pin having a base pin, wherein the base pin has a root portion for fastening the base pin in a natural tooth root and a crown portion for fastening a tooth crown facing to the endodontic pin and/or for arranging in a natural tooth crown, and the base pin is composed of a composite material having at least one organic binder.
In endodontics, a branch of dentistry, a remnant of a natural tooth or at least of a natural tooth root is used to fasten a root pin or endodontic pin with its root portion in the tooth root. The crown portion of the endodontic pin is used to stabilize and/or otherwise supplement a remnant of a natural tooth crown and/or to fasten a tooth crown facing to the crown portion of the endodontic pin.
Endodontic pins made of various materials are known in the prior art. For example, there are many endodontic pins made of metal, e.g. titanium and the like. A problem here is, on the one hand, that the mechanical properties of these metals deviate markedly from the natural tooth substance. On the other hand, there are also problems regarding the biocompatibility of metals, since deposition of metal ions in the tooth and/or in the surrounding soft tissue has been a critical issue.
The prior art also comprises endodontic pins of the type in question in which glass fibers or carbon fibers are embedded in the organic binder. However, experience has shown that signs of fatigue and especially a separation of fibers and binder may occur in these fiber-reinforced synthetics.
The problem addressed by the invention is therefore to improve an endodontic pin of the abovementioned type in such a way its mechanical properties are as similar as possible to the natural tooth substance and in such a way that it has the longest possible useful life.
To this end, the invention provides that the composite material has glass particles as a filler.
An underlying concept of the invention is therefore to produce the endodontic pin using a composite material, or composite, which on the one hand has an organic binder and on the other hand is filled with glass particles as filler. It has been found that in this way endodontic pins can be provided which have mechanical properties very similar to the natural tooth substance and which also have a sufficiently long useful life. Preferred variants of endodontic pins according to the invention have, as the finished end product, a flexural strength in the range of 150 MPa (megapascal) to 250 MPa, preferably of 180 MPa to 220 MPa, particularly preferably 200 MPa. The compressive strength of such endodontic pins is expediently in the range of 450 MPa to 550 MPa, preferably in the range of 500 to 550 MPa, particularly preferably 550 MPa. The flexural modulus of such endodontic pins is expediently in the range of 12 GPa (gigapascal) to 25 GPa, preferably of 17 GPa to 25 GPa, particularly preferably 20 GPa. The surface hardness of preferred endodontic pins is expediently in the range of 85 HV (Vickers hardness) to 120 HV, preferably of 90 HV to 100 HV, particularly preferably 95 HV. All of these parameters can be determined according to EN ISO 4049, edition: 2013 Mar. 1.
The grain sizes of the glass particles of the composite material are preferably in the range of 0.01 μm (micrometer) to 50 μm, particularly preferably in the range of 0.01 μm to 3 μm. The glass particles can be rounded, but they can also have a particle shape deviating from the latter. For the tightest possible packing, the composite material preferably has glass particles of different grain sizes. The composite material can have glass particles of a single glass type, but also of different glass types. These are preferably what are known as macrofilled composite materials. The volume fraction of the glass particles in the finished end product of the endodontic pin or base pin expediently measures at least 78% by volume, preferably at least 83% by volume, particularly preferably at least 90% by volume. The glass particles are preferably ones that have or consist of barium glass and/or strontium glass. The glass particles expediently have a silanized surface. Barium glass and strontium glass are particularly materials that are inherently radiopaque, such that the endodontic pin can be imaged by X-ray even after application in the tooth of the patient. If the glass particles themselves are not radiopaque, aluminum oxide or the like can also be added as further filler to the composite material in order to create suitable radiopacity and therefore visibility in an X-ray image. As further filler, zinc oxide (ZnO) can be added to the composite material of the endodontic pin in order to achieve an antibacterial action. The volume fraction of the zinc oxide in the endodontic pin, i.e. in the end product, is expediently ca. 2-5%. Further fillers of the composite material can be pigments, i.e. coloring agents, and/or catalysts for supporting the polymerization of the organic binder, and/or other additives.
In preferred embodiment variants of the invention, the organic binder includes or consists of at least one methacrylate. The organic binder preferably has methacrylate at least as the main constituent.
The product designated REF 2061, available from Indigodental GmbH & Co. KG in Pinneberg, Germany, can be used for example as the composite material for the production of the base pin or endodontic pin. This product contains triethylene glycol dimethacrylate, urethane dimethacrylate, bis-GMA, and ethoxylated bisphenol A dimethacrylate. The product REF 2050, for example, from the same company can be used as the organic binder.
An endodontic pin is a pin that can be used in endodontics. An endodontic pin according to the invention can also be referred to as a root pin. The endodontic pin according to the invention can be formed exclusively of the base pin. However, endodontic pins according to the invention can also have further constituent parts, e.g. the attachment casing mentioned further below. The base pin has at any rate a root portion. This is the part of the base pin that is anchored in a natural tooth root in order to fasten the base pin. For this purpose, a corresponding canal is generally created in the natural tooth root, e.g. by drilling, into which canal the root portion of the base pin is inserted. The base pin additionally has a crown portion. This is the part that is to be arranged in the region of a natural tooth crown of a natural tooth, or in most cases of a remaining part of the latter. However, the crown portion can also serve for fastening a tooth crown facing, particularly if there remains absolutely nothing or just remnants of the natural tooth crown. Endodontic pins according to the invention can therefore be used, on the one hand, to fasten a tooth crown facing, i.e. an artificial tooth crown or an artificial part of a tooth crown, on a natural tooth root. However, endodontic pins according to the invention can also be used to stabilize a remaining part of the natural tooth crown and serve as an anchor for artificial parts of the tooth crown that are optionally to be added. In this sense, the tooth crown facing can thus replace only parts of a natural tooth crown or else the entire natural tooth crown. In order to fasten the root portion of the base pin in the tooth root, the nerve canal often present originally in the natural tooth root, and in most cases drilled a little further, is used as a canal for fastening the root portion in this canal.
Endodontic pins or root pins according to the invention are preferably prefabricated mass-produced items that can be manufactured cost-effectively and that the dentist can fit at a single visit into the remaining tooth root or into the remaining natural tooth. Since the composite material of the endodontic pin according to the invention is very similar to the natural tooth substance in terms of its mechanical properties, the drills, grinders and the like that are familiar to a dentist can be used for any shortening or shaping work that may be needed before fitting.
The root portion of the base pin is preferably bonded or cemented with a fastening material, or in other words a cement, into the previously prepared and cleaned canal of the natural tooth root. The fastening material used for this purpose preferably has a composition similar to that of the composite material of the base pin. The fastening material is thus expediently also a composite material with an organic binder and glass particles as filler. Thus, the organic binder of the fastening material can preferably again include or be composed of at least one methacrylate. However, since the fastening material in the uncured state should be liquid or at least pasty, provision is expediently made that the degree of filling, i.e. the volume fraction of the fillers, in particular of the glass particles, is less than in the composite material of the endodontic pin. The proportion of filler, in particular the proportion of glass particles, in the fastening material is expediently between 45% by volume and 65% by volume.
By virtue of the proportion of organic binder of the fastening material, the latter can be polymerized by the action of light and thus cured. In order to support and promote the best possible permanent connection and rapid curing of the fastening material, provision is made, in particularly preferred variants of endodontic pins according to the invention, that the base pin has a light admission surface in the crown portion and, in order that light introduced via the light admission surface is conveyed onward into the root portion, is designed to be light-transmitting at least in part, preferably all over. Therefore, in these embodiments, the base pin itself is used as a kind of light guide, such that light introduced into the base pin via the light admission surface is guided via the base pin itself to the fastening material, in order to force the curing of the fastening material.
In order to provide suitably good light transmission, the base pin in preferred embodiments has a relatively low opacity at least in part, preferably all over, or to put it the other way a relatively high degree of translucence. The opacity of the base pin at least in part, preferably all over, is preferably in a range of between 15% and 45%, preferably in a range of 25% to 30%, particularly preferably ca. 27%. This opacity, and all the opacities mentioned below, can be determined according to DIN 6174. The light admission surface is expediently located at the end of the crown portion of the base pin remote from the root portion.
To ensure that the light introduced via the light admission surface is guided particularly effectively to the places where it is needed for curing the fastening material or cement material, the base pin in preferred variants has a lens body. This lens body is expediently located in the crown portion of the base pin. The lens body is preferably configured as a thickening of the base pin. This means that the lens body therefore preferably has a diameter greater than the root portion and also greater than the rest of the crown portion of the base pin. The lens body is distinguished by its refractive action. It diverts the light, introduced via the light admission surface, in such a way that said light is conveyed to the places where it is needed for curing the fastening material. These are in particular the outer surfaces of the root portion of the base pin, and also any shoulder portions of the endodontic pin that may be present, which shoulder portions are explained in more detail below and can likewise bear on the remaining natural tooth root.
In preferred embodiments, the root portion of the base pin is designed as a cone tapering in a direction away from the crown portion. It is preferably a root portion that is rotationally symmetrical with respect to a longitudinal axis of the base pin. The cone is thus expediently frustoconical or conical. The outer surface of the root portion of the base pin can have a certain roughness. However, there are preferably no outwardly visible structures such as threads or the like in the outer surface of the root portion of the base pin. In preferred embodiments, it could thus be said that the outer surface of the root portion is smooth.
As has been stated, endodontic pins according to the invention can be formed exclusively of the base pin. However, in other embodiments of the invention, provision can also be made that the endodontic pin has, in addition to the base pin, an attachment casing which envelops, preferably exclusively, the crown portion of the base pin, preferably in a circumferentially closed manner. Provision is preferably made here that the attachment casing has a higher opacity than the base pin. The higher opacity of the attachment casing in relation to the base pin serves to ensure that the complete or partial crown that is ultimately created is as similar as possible, also in terms of color, to the natural appearance of a tooth crown. The opacity of the attachment casing is expediently in the range of 50% to 80%, preferably 65% to 75%, particularly preferably ca. 70%.
Apart from the pigments, i.e. coloring agents, needed for its color, the attachment casing can be made of the same composite material as the base pin or can at least have such a material. To color the composite material used for producing the attachment casing, organic and/or inorganic pigments known per se can be used, e.g. also whiteners such as TiO2. The pigments can be adapted such that the overall appearance of the attachment casing is as close as possible to that of the natural dentine in the mouth of the patient. Expressed using the Lab color space, the attachment casing preferably has an L value of 59 to 69 and/or an a value of −0.35 to −3.2 and/or a b value of −0.4 to −6.95. Like the determination of the opacity, the determination of the L value, the a value and the b value can be carried out according to the provisions of DIN 6174. In preferred embodiments of such endodontic pins, provision is made that the attachment casing, which could also be designated as a restorative attachment casing, forms a shoulder portion of the endodontic pin, which shoulder portion protrudes relative to the root portion of the base pin. This shoulder portion is expediently formed in a closed manner around the circumference of the whole endodontic pin. With this shoulder portion, the endodontic pin can bear on the remaining natural tooth root.
In preferred embodiment of the invention, provision is made that the base pin is of an inherently monolithic configuration. This preferably also applies to the optionally present attachment casing. Monolithic here means produced from one casting or in one piece. There are therefore expediently no interfaces in the base pin and if appropriate also in the attachment casing. The base pin is therefore preferably formed from one piece, and the composite material is preferably uniform throughout the inside of the base pin. The same preferably applies also to the attachment casing.
In particularly preferred embodiments of endodontic pins according to the invention, provision is made that the glass particles are fused together. The glass particles of the composite material of the endodontic pin are thus still discernible as such in corresponding microscopic images but are interconnected by melting and fusing together of their surfaces. This fusing together of the glass particles can be achieved by a laser treatment of the base pin and, if appropriate, also of the attachment casing, as is explained in more detail below. The base pin and/or also the optionally present attachment casing can thus be laser treated, as can be seen from the fusing together of the glass particles. The fusing together results in a still stronger bond than the one already provided by the connection of the glass particles by means of the cured organic binder. In preferred embodiments, the glass particles are fused together in the whole base pin. If an attachment casing is present, this also applies in preferred embodiments to the attachment casing. Thus, the glass particles are also expediently fused together in the whole of the attachment casing if present.
To be able to create in the remaining natural tooth root a canal matching the root portion of the base pin, drills are expediently made available which are adapted in shape to the shape of the root portion of the base pin. Here, adapted means that the drills are able to drill, into the remaining natural tooth root, a hole or a canal that provides the space needed to fasten therein the root portion of the base pin and the necessary fastening material. The shape of the drill thus corresponds substantially to the shape of the root portion of the base pin or can be slightly larger in order to create space also for the fastening material. In this context, the invention also relates to a kit having at least one endodontic pin according to the invention, preferably several endodontic pins according to the invention, and at least one drill, wherein the shape of the drill is adapted to the shape of the root portion of the base pin of the endodontic pin. Such a kit can of course also comprise several endodontic pins and also, if necessary, several drills matching them. In addition, the kit can also comprise the appropriate fastening material. The drills can have a longitudinal stop and/or a preferably visible marking, such that the hole is always drilled to the optimal length or depth in the tooth root.
Further features and details of preferred embodiments of endodontic pins according to the invention and of methods for their production are explained in more detail below in the description of the figures, in which:
The example of an endodontic pin 1 according to the invention shown in
The region of the base pin 2 arranged inside the attachment casing 13 in the embodiments of
The length 23 of the tooth portion 3 of the base pin 2 is preferably in a range of 11 mm to 13 mm, preferably 12 mm. The length 24 of the crown portion 5 of the base pin 2 expediently measures between 3 mm and 5 mm, preferably 4 mm. The overall length 22 of the base pin 2 accordingly results from the sum of these two values. At its lower end directed away from the crown portion 5, the root portion 3 expediently has a width 26 of between 1.0 mm and 1.5 mm. This end is preferably a blunt end, i.e. not a pointed end. The width 27 at the end of the crown portion 5 of the base pin 2 remote from the root portion 3 preferably measures between 1.8 mm and 2.2 mm, preferably 2 mm. In variants with an attachment casing 13, as shown by way of example in
The natural tooth root 4 into which a canal 33 has been drilled is shown in each case. The respective endodontic pin 1 is cemented or bonded in the canal 33 by the fastening material 28. Before the tooth crown facing 6 is applied or the tooth crown 32 completed, the fastening material 28 can be cured by light being introduced into the respective light admission surface 10, since the suitably light-transmitting base pin 2 of the respective endodontic pin 1 conveys the light, needed for accelerated curing of the fastening material 28, from the light admission surface 10 into the root portion 3 and if appropriate also into the shoulder portion 14 and thus directly to the fastening material 28. As soon as the respective endodontic pin 1 is suitably fastened in the natural tooth root 4, a tooth crown facing 6 can then be applied to the crown portion 5 of the base pin 2 and, if present, to the attachment casing 13 of the endodontic pin 1. These tooth crown facings 6 are known per se. As is known in the prior art, they can be produced and fastened to the respective crown portion 5 or attachment casing 13 by methods known per se. However, the tooth crown facing 6 can also take the form of veneers, i.e. front tooth facings, or onlays, i.e. artificial bite surfaces. However, if regions of the natural tooth crown 32 are still present, they can be supplemented by methods known per se for building up a tooth crown facing 6 and can be built up again to a complete tooth crown 32, after insertion of the endodontic pin 1 into the tooth root 4. The crown portion 5, along with the attachment casing 13 if present, is then arranged in the natural tooth crown 32 and serves to stabilize the latter and acts as a fastening point for the artificially added parts of the tooth crown 32.
For the sake of completeness, it will be noted that, as is also shown in
A possible method for producing endodontic pins 1 according to the invention is explained by way of example below. Individual steps of the method, e.g. the polymerization by the use of the LED lamp 19 and/or the laser irradiation for fusing the glass particles 9, can also be combined with method steps other than those explained below.
First of all, the individual constituent parts of the composite material 7, i.e. primarily the organic binder 8 and the preferably silanized glass particles 9 and if appropriate other fillers such as zinc oxide, catalysts and/or additives, are mixed with one another. Alternatively, as has already been explained in the introduction, it is also possible to use commercially available ready-made mixtures of the composite material 7.
The production of a base pin 2 is now explained with reference to
Alternatively to this, the composite material 7 could of course also be introduced by injection molding into an already closed mold.
In preferred embodiments of the method, the filled and closed mold is then heated to a temperature of 300° C. and maintained at this temperature for at least half an hour. In this way, a temperature-induced polymerization process takes place for curing the organic binder 8 in the composite material 7. To further promote the polymerization or curing of the organic binder 8, an LED lamp 19 is provided in the illustrative embodiment shown. The light of the LED lamp 19, which preferably lies in a wavelength range of 395 to 480 nanometers, particularly preferably of 450 to 480 nanometers, passes through the light-transmitting first mold half 17 to the composite material 7 in the mold cavities 34 and 35 and further promotes the polymerization or curing of the organic binder 8. The LED lamp 19 can be so large that it covers the whole of the first mold half 17. Of course, it is equally possible also to move the LED lamp 19 along the first mold half 17 in order to expose the whole mold cavity 34, 35 uniformly to LED light.
Following this process of curing or polymerization of the organic binder 8, the composite material 7 in the mold cavities 35 and 35 is then also subjected to laser treatment in order to fuse the glass particles 9 of the composite material together. For this purpose, the composite material 7 in the mold cavities 34 and 35 is subjected to laser light from the laser light source 20 by way of the first mold half 17. The intensity and the duration of irradiation are set such that the laser light passes through the whole of the composite material 7 and, in this way, the glass particles 9 in the composite material 7 are fused together in the whole of the base pin 2 located in the mold halves 17 and 18. For this purpose, the laser light source 20 can be suitably guided across the whole of the first mold half 17 or the whole region of the mold cavities 34 and 35. After completion of the laser treatment, the base pin 2 produced can be removed from the mold halves 17 and 18. As a result of the curing of the organic binder 8 and the subsequent fusion of the glass particles 9, in particular at their surfaces, a monolithic base pin 2 is preferably produced. If the endodontic pin 1 that is to be produced according to the invention is intended to be composed exclusively of the base pin 2, the production process is thereby concluded, although this does not of course rule out secondary treatments, e.g. of the surface.
By contrast, if the endodontic pin 1 according to the invention is intended also to have an attachment casing 13, the finished base pin 2 is introduced into a second mold 37 shown in
In this connection, provision can be made that one or more endodontic pins 1 are sold in a kit together with suitably matching drills 15. This kit can additionally comprise the appropriate fastening material 28.
| Number | Date | Country | Kind |
|---|---|---|---|
| A 98/2017 | Mar 2017 | AT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/055724 | 3/8/2018 | WO | 00 |
