^• k A A A

DESCRIPTION

Scope of the Invention

The present invention relates to the dental field and in particular relates to an endodontic supporting pin for a tooth reconstruction and to a corresponding connector. State of the art

As it is known, in endodontic field operations of root canal treatment are usually carried out.

The operation of root canal treatment provides the removal of the tooth pulp and in particular it consists in drilling, by appropriate milling tools, a root canal of the tooth itself by completely removing its content of vessels and nerves.

Such an operation is followed by a subsequent step of sealing the so-treated root canal, carried out by proper sealing materials, for example cements and/or thermoplastic materials used as canal filler.

The sealing step, in some cases, is followed by a partial tooth reconstruction step comprising a step of installation of a supporting pin. In fact, based on the volume of material removed by milling, a large part of the tooth needs to be reconstructed for recovering its original functionalities as well as its aesthetical appearance. Thus the supporting pin acts as a support for an auxiliary tooth portion, for example a prosthetic crown, and also represents a support for promoting the correct reconstruction of the tooth itself.

In particular, the installation step results in a partial removal of the sealing material of the root canal or, alternatively if not present, a partial filling thereof, so that to define a housing seat in which the supporting pin is inserted. In other words, in the root canal a bottom seal made of sealing material is held or created, for substantially realizing a partial housing seat for the supporting pin.

More particularly, said installation step provides that a portion of the supporting pin is inserted and fastened into the housing seat of the root canal by employing a fastening material, usually a resin, different from the sealing material, and/or in combination with further mechanical fastening means, for example a thread obtained on a portion of the pin.

The remaining portion of the supporting pin is conversely held as protruding from the root canal such that the prosthetic crown can be applied. The supporting pin is thus adapted to assure the filling solidity and the structural resistance of the prosthetic crown as well as that of the tooth portion subjected to coronal reconstruction.

Different typologies are known of endodontic supporting pins used for the tooth reconstruction.

An example of supporting pin for endodontic applications is described in the document US 6,371,763 disclosing a supporting pin composed of a plurality of glass fiber micro -filaments homogeneously clustered together in a linear or twisted way. The number of micro-filaments defines the external diameter of the supporting pin. The so- realized pin is substantially flexible so that it can be inserted in the drilled root canal thereby fitting to its usually curved configuration.

Endodontic supporting pins having rigid structure are known as well.

In US 2003/0113691 a substantially cylindrical supporting pin is described, provided with a housing for the connection of a removing tool. In particular, the housing is substantially coaxial to the pin axis, with circular or polygonal section, and is adapted to be engaged by a removing tip having a shape complementary thereto," integral with the removing tool. The housing has a diameter, or however a width, much smaller than the external diameter of the supporting pin in order to not impair its mechanical resistance.

When the pin is in place, the housing is generally filled with easily removable material, in particular to allow the engagement thereof with the tip of the tool for the pin removal.

It is also known the use of pins of tubular shape to allow the installation thereof on already existing pins, or to leave free access to the tooth canal. Usually, those are pins made of metal to assure an adequate sturdiness in their use.

In particular, patent US 5,161,973 relates to a method for installing a pin in a tooth already having a metal obturator inside thereof. The method comprises the steps of obtaining a hole in the tooth with a tubular cutter having an internal diameter larger than the obturator diameter and inserting a tubular pin into the hole, the pin receiving the metal obturator in its own inside. The pin is thus tubular in order to be installed in a tooth wherein a metal obturator has already been installed, which is englobed outside thereof without being removed.

Document CH 652588 relates to a tubular pin for allowing the access to the tooth root canal in which it is installed. In this way, treatments to the canal can be performed without the need of pin removal.

German Patent DE 828283 relates to a structured pin for driving a drill in case damaged portions of a tooth root canal have to be removed, without impairing the healthy portions of the root itself. For this purpose the pin has to be a metal one.

German Patent DE 1191073 describes a tooth pin having an opening for the insertion of a metal wire adapted to be inserted into the tooth canal to prevent the cement from entering during the fastening step of the pin. The metal wire is then removed such that the opening remains free to allow accessing to the canal for possible medications.

French Patent FR 1.322.961 relates to a pin for tooth prostheses comprising a threaded rod intended to be screwed in a corresponding tapping of a sleeve inserted and cemented in a canal made in a tooth root.

Finally, International Patent Application WO 2009/102958 relates to a tooth pin system having a thermoplastic coating and which is heated and inserted in a canal of a tooth root for the pin fastening.

These supporting pins and others known in the art give rise to some problems during the installation step in the root canal, and in particular generate drawbacks of structural resistance in the connection supporting pin - root canal.

In detail, in the usual practice, the installation and the fastening of the supporting pin inside the root canal during the reconstruction step, occur as follows.

Firstly, by means of a needle or cannula a resin amount is inserted into the root canal, adapted to fill it at least partially.

Secondly, the supporting pin is positioned into the resin by submerging it until a desired depth. During the pin submersion into the resin a passage opens on the open surface of the latter upon which air bubbles can remain trapped into the resin until even its solidification.

Therefore the presence of air bubbles into the resin determines structural drawbacks in the supporting pin - root canal assembly, that is to say it yields a depletion of mechanical resistance which can cause a poor pin stability with possible rupture of the reconstructed tooth portion.

Italian Patent IT 1372930 provides the use of a steel metal needle for injecting the resin into the endodontic hollow. The needle is then tailored cut, directly inside the patient mouth, and left inside the hollow. This supplementary operation could impair the correct positioning of the needle itself and makes difficult the pin dimensioning. The patent suggests the use of a needle for injecting the resin starting from the bottom of the endodontic hollow, to avoid the inclusion of air bubbles. However these needles are stiffer than dentin and can damage the tooth canal walls. However other material types, which can be employed alternatively to metal, are not indicated in the patent nor indication is given about the size of the internal diameter of the needle. From the patent drawing it can then be observed that the needle end portion is partially cut, to facilitate the insertion thereof into the canal and promote the resin outflow. However this makes the ending part weaker than the remaining part of the needle, with subsequent problems relating to the needle resistance.

Summary of the invention

It is therefore object of the present invention to provide an endodontic supporting pin and a corresponding connector which allow overcoming the above mentioned drawbacks referring to the known art.

It is also an object of the present invention to provide an endodontic supporting pin having, in use, a mechanical resistance comparable to the original bone resistance of the tooth in which it is inserted.

It is further an object of the present invention to provide an endodontic supporting pin which, in use, is particularly resistant from a structural point of view regardless of its dimensions.

It is again an object of the present invention to provide an endodontic supporting pin able to fit to different use requirements.

It is also an object of the present invention to provide an endodontic supporting pin which is easy and cheap to realize.

It is further an object of the present invention to provide an endodontic supporting pin having already the correct measure and which does not require additional cut operations once installed into the tooth.

It is a further an object of the present invention to provide a kit comprising an endodontic supporting pin and a related connector which simply and effectively solve the drawbacks of conventional solutions.

These and other objects are obtained by an endodontic supporting pin according to claim 1.

In particular the endodontic supporting pin, according to the present invention, comprises an elongated body having a longitudinal axis and a prearranged external width or external diameter (d _ext ), a through hole extended into the elongated body with a drilling axis substantially parallel to said longitudinal axis and with a prearranged internal width or internal diameter (dj„ _t ), wherein the ratio between the internal width/internal diameter (di„ _t ) of the through hole and the external width/external diameter (d _e * _t ) of the elongated body determined on a common measurement plane perpendicular to the longitudinal axis and to the drilling axis cross-cutting the supporting pin, is comprised between 0.3 and 0.9, so that the supporting pin is adapted to act as a cannula for injecting a fastening material into a root canal of a tooth and that the through hole is adapted to be filled with the fastening material, thereby constituting a core of the supporting pin.

Preferably the ratio between the internal width/ internal diameter (dj _nt ) and the external width/ external diameter (d _ext ) is in the range from 0.5 to 0.65.

The term "external/internal width" is substantially referred to polygonal sections of the elongated body and/or the through hole of the supporting pin according to the invention and by this definition the maximum width of the considered polygonal section is substantially intended. Conversely, the term "external/internal diameter" is referred to substantially circular sections of the elongated body and/or the through hole.

The supporting pin is intended to couple with a connector according to claim 11.

Specifically, the connector has a hollow body which defines a passage duct of a fastening material, provided with a connecting portion to be combined with a device for injecting a fastening material and a tip portion to be coupled with a free end of the supporting pin. With the term "free end" the end of the supporting pin is meant, which is intended to appear, once installed, from the root canal.

The connector tip portion has a complementary shape with respect to the shape of the free end of the supporting pin for realizing a substantially sealed shape coupling.

More in detail, the tip portion has shape and size suitable to be fitted on the outside or to be inserted inside the free end of the supporting pin; the connecting portion of the connector has suitable shape and size to be combined with a device for injecting a fastening material, or else it can be integral with the injecting device itself.

The above described technical characteristics of the endodontic supporting pin are advantageous with respect to the known art for the following reasons.

The supporting pin, according to the present invention, besides playing the main function of support for the prosthetic reconstruction of the tooth, also acts as a cannula for the injection of a fastening material into the tooth root canal and allows to realize a homogeneous distribution of the fastening material by avoiding the drawback due to the formation of air bubbles, as described in detail in the following. The presence of an outer connector allows easily putting into communication the supporting pin with an injecting device, without modifying the structure of the pin itself and can be easily removed at the end of the installation step.

In particular, the installation of the endodontic supporting pin, object of the present invention, occurs as follows.

A first step provides the realization of a housing seat for the supporting pin with sealing of a bottom portion of the root canal. In particular, the housing seat is obtained by a partial removal of sealing material from the root canal if already present, or alternatively by a partial filling of the root canal itself always with the sealing material.

In a second step, the supporting pin engages the housing seat contacting with a bottom surface thereof (seal), in particular it is in abutment with the housing seat, or it is inserted up to a certain depth therein, or again, alternatively the supporting pin engages the housing seat at a certain distance from the bottom surface.

Preferably, before positioning the supporting pin into the housing seat, the collector tip portion is coupled with the free end of the supporting pin. Furthermore, if required, the connecting portion of the adapter is combined with the device for injecting the fastening material.

Through the through-hole present in the elongated body of the supporting pin a fastening material is therefore introduced, preferably a self-hardening injectable resin, which arranges over the bottom surface of the housing seat, filling the housing seat i.e. the remaining part of the root canal with a distribution going from the bottom surface towards the top of the root canal itself. Such a distribution causes, at the same time, the fastening of the supporting pin into the canal, which is gradually surrounded by the going up resin, until being englobed into the same resin. Finally, at the end of the filling, the connector tip portion is disconnected from the free end of the supporting pin. In accordance with the invention, a resin insertion carried out through the through-hole of the supporting pin avoids the presence of air bubbles into the hardened resin. Of course no opening is generated on the open surface of the resin since the supporting pin is already positioned in the housing seat of the root canal when the resin is injected, thus allowing a homogeneous distribution thereof also free from defects such as air bubbles.

Advantageously, in accordance with the invention the afore said ratio (di _nt /d _e xt) allows facilitating the resin outflow within the through hole, without causing restrictions in its delivery and plugging and/or clogging in the through hole. Furthermore such a ratio (di _nt /dext) allows obtaining an adequately robust supporting pin.

Still in accordance with the invention, during the resin insertion step, the through hole itself of the supporting pin is in its turn gradually filled with resin and, therefore, at the end of the installation step the supporting pin has a core made of resin. This prevents bacterial infiltrations from occurring in the tooth root canal which can cause infections to the roots and outside the tooth roots and contributes to increase the mechanical resistance of the supporting pin.

Preferably, the elongated body of the supporting pin has a cylindrical or frusto- conical shape having a circular/ polygonal base and the through hole has a substantially circular/ polygonal shape, or a combination thereof. Preferably, the connector tip portion is fitted outside the free end of the supporting pin and similarly the passage duct has respectively a cylindrical or frusto-conical shape having a circular/ polygonal base with a substantially circular/ polygonal section.

In a preferred embodiment the supporting pin according to the present invention having a frusto-conical shape has an outer side wall tilted with respect to the longitudinal axis, of an angle comprised between 2° and 15°. Consequently, the passage duct of the connector tip portion has in its turn a corresponding frusto-conical shape.

Advantageously, the elongated body is realized in a composite material preferably comprising carbon fiber and/or glass fiber, or else it is made of metal or plastic material. The selection of the material used for the elongated body and the fastening material, i.e the resin representing the core of the supporting pin in use, allows diversifying the mechanical and structural characteristics of the supporting pin in accordance with specific requirements, differently from the pins realized and used according to known art which do not provide for a core made of resin. Advantages follow such a higher resistance to cyclic loads the treated tooth is subjected to, mainly during chewing. In fact the resistance and in general the mechanical characteristics of the supporting pin can vary according to the typology of used resin, the density thereof and other parameters.

Preferably, the elongated body comprises at its end adapted to be introduced in the housing seat of the tooth root canal, at least one notch radial with respect to the drilling axis. In particular, the notch is obtained in the pin thickness and creates a passage intercepting the through hole. In this way at the notch, the resin coming from the through hole expands in radial direction too and promotes a more homogeneous distribution thereof. With the aid of the notch also a possible clogging effect is prevented when the end of the supporting pin contacts the bottom surface of the housing seat of the tooth root canal.

Preferably, the afore said elongated body has one or more openings intercepting the through hole. Also the openings have the function of causing the resin outflow substantially in a direction radial with respect to the drilling axis at a higher height with respect to the notch made at the end of the supporting pin.

The openings can be shaped as one or more slots or as one or more holes aligned each other along the longitudinal axis.

The openings are preferably obtained on the elongated body of the supporting body from opposite sides with respect to a symmetry plane containing said longitudinal axis. Detailed description of the figures

Further characteristics and advantages of the present invention will be more evident from a review of the following specification of some preferred, but not exclusive, embodiments, shown for illustration purposes only and without limitation, with the aid of the attached drawings, in which:

• figure 1 shows a perspective view of an endodontic supporting pin, according to the present invention;

• figure 2 shows a cross sectional view of the endodontic supporting pin of figure 1, according to the present invention;

· figure 3 A shows a supporting pin according to the present invention coupled with a connector in an embodiment according to the present invention;

• figure 3 shows the endodontic supporting pin of figure 1 during a first installation step in a tooth root canal;

• figure 4 shows the endodontic supporting pin in a time step subsequent to the step shown in figure 3;

• figure 5 shows a constructive variation of the endodontic supporting pin of figure 1, according to the present invention;

• figures 6 to 6C show additional constructive variations of the endodontic supporting pin according to the present invention.

Detailed description of the invention

Referring to figure 1 an endodontic supporting pin 100 is represented, according to the present invention used for dental applications of prosthetic reconstruction of a tooth generally following operations of root canal treatment or alike.

In particular the supporting pin 100 comprises an elongated body 10 with a longitudinal axis 10' and an external width or external diameter d _e t (Fig. 2). On the elongated body 10 a through hole 15 is obtained having internal width or internal diameter dj„ _t (Fig. 2) with a drilling axis 15' substantially parallel to the longitudinal axis 10' and preferably coincident thereto.

As better highlighted in figure 2, the ratio between the internal width/internal diameter di„ _t of the through hole 15 and the external width/external diameter d _ex t of the supporting pin 100 determined on a common measurement plane 30 (Fig. 1) perpendicular to the longitudinal axis 10' and to the drilling axis 15', is comprised between 0.3 and 0.9. Preferably such a ratio di„ _t / d _ext is comprised between 0.5 and 0.65.

In particular, as represented in the examples of figures 1 to 6C, the elongated body 10 and the through hole 15 have substantially a circular section and in such a case it is referred to the expression "internal diameter" of the through hole 15 and "external diameter" of the elongated body 10, without however excluding the possibility of providing an elongated body and/or a through hole with different geometry, for example with polygonal section, for which it is referred to the expression "internal width" of the through hole and "external width" of the elongated body, such an embodiment not being shown in figures.

Dimensional examples of the supporting pin 100, according to the present invention, provide for a through hole 15 with a dj„ _t = 0.25 mm and an elongated body 10 with dext = 0.7 mm, both detected on the common measurement plane 30. Or else a supporting pin with dj„ _t = 0.5 mm and d _ex t = 1 mm or again with di„ _t = 0.7 mm and d _ex t = 1.5 mm.

An alternative embodiment of the supporting pin according to the present invention wherein parts structurally and functionally corresponding to the afore mentioned ones for the pin 100 hold the same reference numbers, is shown in the example of figure 5 wherein a supporting pin 101 is represented.

The supporting pin 101 has an elongated body 11 substantially similar to the pin of figure 1, but having a frusto-conical shape and comprising an outer side wall 12 tilted, with respect to the longitudinal axis 10', of an angle comprised between 2° and 15°. Additionally the supporting pin 101 has, at one end 10a, a notch 18 adapted to facilitate the outlet of the resin used for the pin fastening, according to a radial direction with respect to the drilling axis 15', as it will be better evident in the following.

Further embodiments of the supporting pin according to the present invention are shown in the examples of figures 6, 6A, 6B and 6C. In particular in the afore said figures, wherein parts structurally and functionally corresponding to those of the afore described pins hold the same reference numbers, supporting pins 102, 102', 103, 103' are shown, respectively. In detail, the afore said supporting pins comprise one or more openings 25, 25' obtained on the frusto-conical elongated body 11 which intercept the through hole 15, at a height higher than the notch 18 obtained on the end 10a and, specifically, comprise a single slot 25 (Fig. 6) or several slots 25 aligned each other along the longitudinal axis 10' (Fig. 6A), or alternatively a single hole 25' (Fig. 6B) or still several holes 25' aligned each other along the longitudinal axis 10' (Fig. 6C).

The elongated body 10, 11 of the supporting pin 100, 101, 102, 102', 103, 103' is preferably made of a composite material comprising carbon fiber and/or glass fiber or it can alternatively be made of metal or plastic material.

Figure 3A shows an example of connector 300 according to an embodiment of the present invention. The connector 300 has a hollow body that, in its inside, defines a passage duct 301 in which a fluid coming from a source - not represented - is intended to flow, the source can be an injecting device. The fluid is fed into the connector through a connecting portion 302 adapted to be coupled with the feeding source, and outflows through a tip portion 303. The tip portion is shaped and sized so that to result complementary to a free end 10b, opposite to the end 10a, of the supporting pin for realizing with the same a substantially sealed shape coupling.

More in detail, the tip portion has shape and size suitable to be inserted into the through hole 15 of the supporting pin at the free end 10b, or preferably to be fitted outside thereof.

The connector 300 can be integral with the injecting device but, preferably, it is a standalone part in order to be changed according to needs based on the shape and size of the supporting pin to be used according to requirements or applications.

Referring to figures 3 and 4, a supporting pin 100 is shown according to the present invention as represented in the embodiment of figure 1, during a step of installation in a root canal 210 of a tooth 200.

Firstly, a housing seat 211 is obtained in the root canal 210 of the tooth 200, generally obtained by removing a part of the already present sealing material from the root canal 210 so that to hold a sealing 280 in the bottom portion of the root canal 210 itself. The sealing 280 defines a corresponding bottom surface 210b. Alternatively, the housing seat 211 can be prearranged by inserting the sealing material into the root canal if this is not already present.

The supporting pin 100 is subsequently engaged in the housing seat 211, preferably until reaching and abutting against the bottom surface 210b of the sealing 280, however without excluding, as shown in figures 3 and 4, a positioning thereof at a height higher than the bottom surface 210b of the sealing 280.

The adapter 300 is fastened to the supporting pin 100 preferably before positioning the pin itself into the housing seat 211. Therefore the supporting pin 100, according to the present invention, allows injecting a fastening material through the through-hole 15, in particular an injectable resin 250 (Fig. 3) and acting substantially as an injection cannula or needle. To do this the free end 10b, opposite with respect to the end 10a, of the supporting pin 100 is coupled to the connector 300, which belongs to the device for injecting the resin 250.

In this way, the resin 250 flows through the through hole 15 and gradually fills the root canal 210 of the tooth 200 and, at the same time, also the through hole 15 of the supporting pin 100, with a distribution going from the bottom surface 210b of the sealing 280, towards a top 210a of the root canal 210 itself thus preventing air bubbles from forming in the resin as conversely occurs by following the known installation steps. The supporting pin 100 remains thus trapped in the root canal 210 as a consequence of the hardening of the resin 250 itself. The connector 300 is then removed leaving the supporting pin installed in the tooth root canal.

The advantages of the present invention, already evident in the afore mentioned description, can be summarized by pointing out that the supporting pin, according to the invention, allows carrying out an installation in the root canal of a tooth by acting as a cannula or needle for the injection of a fastening material so that to obtain a homogeneous distribution of the fastening material itself therefore avoiding the drawback due to the formation of air bubbles.