TECHNICAL FIELD OF THE INVENTION

The present invention concerns the branch of dentistry that focuses on the design and construction of prostheses, more specifically dental prostheses on implants and even more specifically metal supporting structures for such prostheses.

DESCRIPTION OF THE STATE OF THE ART

Several methods for making dental items, or dental prostheses are known in the art, these methods being used to restore the original teeth of a patient, who may have lost or damaged them, for functional and/or aesthetical reasons.

According to a known technique, the dental prosthesis is made by a dental technician and then screwed on implants introduced in the jawbone, usually titanium implants. These are defined as dental prostheses on implant. The dental prosthesis is typically constituted by one or more teeth which are restored in order to create an item that has variable dimensions and is suited to be screwed on the implants made for this purpose.

In the known techniques, a supporting structure of the metallic type or made of another compatible material currently in use, for example titanium, is used to restore the tooth, wherein said supporting structure occupies most of the tooth volume that constitutes the tooth core. A surface layer of a light curing composite material, which makes up the functional/aesthetic part of the restored tooth/teeth, is then laid/fixed on the supporting structure.

According to the known technique, the supporting structure of the metallic type is made using several pins that are fixed/screwed on the respective implants inserted in the jawbone. Typically, the implants are inserted at the level of the areas from where the teeth have been removed and consequently several pins are fixed/screwed on said implants. Therefore, the pins are positioned side by side. To make the supporting structure, the pins must be connected to one another, more specifically each pin must be connected to an adjacent pin on its right and/or left side. This operation is performed during a specific intermediate phase of the construction of the prosthesis, when the individual pins, fixed/screwed on the corresponding implants situated in the mouth, are welded to each other by the dentist.

In order to allow a pin to be connected/welded to the adjacent pin, the pin is preferably provided with tabs extending laterally with respect to the longitudinal development of the pin itself. The tabs of the known type are constituted by small plates with rectangular cross section that extend over such a length that the tabs of adjacent pins partially overlap, so that they can be placed in contact with each other and then welded together. The welding is typically a resistance welding operation carried out at two or more points through the passage of a high intensity electric current obtained using specific welding equipment, for example an electrode welding machine and/or a spot welder.

Once the supporting structure has been created by welding all the required pins, the operations for the construction of the remaining aesthetic/functional part of the tooth/teeth on the supporting structure are carried out, for example the laying of one or more layers of a light curing composite material, for example dentine.

In the field of the execution of said prostheses, a strongly felt need concerns the making of the supporting structure, which must have special characteristics in terms of mechanical resistance. A critical step for the achievement of the desired mechanical resistance is constituted by said pin welding step.

In fact, a drawback related to the known techniques is represented by the fact that it is difficult to make high quality and high resistance welds.

It is the object of the present invention to provide a technique for the construction of a dental prosthesis, in particular of the supporting structures associated therewith, which makes it possible to overcome the inconvenience observed in the known technique.

It is a first object of the invention to provide a solution suited to be used for making dental prostheses in which the supporting structure of the tooth guarantees improved resistance and longer duration compared to the solutions known in the art.

SUMMARY OF THE PRESENT INVENTION

The present invention is based on the general consideration of providing a pin for a supporting structure of a dental prosthesis, said pin comprising at least one tab having a convex surface suited to be placed in contact with a surface of a tab of an adjacent pin of said supporting structure.

According to a first aspect of the present invention, therefore, the same concerns a pin for a supporting structure of a dental prosthesis, said pin comprising a main body developing longitudinally along a main axis and comprising a connection area for connection to an implant inserted in a patient’s jawbone, said pin comprising a first tab extending transversally along a tab axis that is inclined with respect to said main axis, said first tab comprising at least one first contact surface suited to be placed in contact with a surface of a tab of an adjacent pin of said supporting structure or in contact with a contact surface of a connection element for connection to an adjacent pin of said supporting structure, wherein said first contact surface comprises at least one convex area.

Preferably, the tab axis of said first tab is perpendicular to the main axis.

In a preferred embodiment, the pin comprises a second tab extending transversally along a tab axis that is inclined with respect to said main axis, said second tab comprising at least one first contact surface comprising at least one convex area suited to be placed in contact with a surface of a tab of an adjacent pin of said supporting structure or in contact with a contact surface of a connection element for connection to an adjacent pin of said supporting structure. Preferably, the tab axis of said second tab is perpendicular to said main axis. According to a preferred embodiment, along a section plane that is perpendicular to said tab axis, said at least one convex area has the shape of a circle sector. Preferably, the curvature radius of said circle sector is smaller than 100 mm, more preferably the curvature radius of said circle sector is equal to 40 mm.

In a preferred embodiment, the first tab and the second tab extend from opposite sides with respect to the main axis.

Preferably, the tab axis of the first tab and the tab axis of the second tab are inclined with respect to each other by an angle included between 90° and 179°, preferably between 140° and 165°, more preferably by an angle equal to 150°.

In a preferred embodiment, the first tab comprises also a second surface, opposite said first surface with respect to said tab axis.

According to a preferred embodiment, said second surface is plane.

According to an alternative preferred embodiment, said second contact surface comprises at least one convex area suited to be placed in contact with a surface of a tab of an adjacent pin of said supporting structure or in contact with a contact surface of a connection element for connection to an adjacent pin of said supporting structure.

According to a preferred embodiment, along a section plane that is perpendicular to said tab axis, said at least one convex area of said second contact surface has the shape of a circle sector.

Preferably, the curvature radius of said circle sector is smaller than 100 mm, more preferably a curvature radius equal to 40 mm. In a preferred embodiment, the main body comprises a through hole suited to accommodate a fixing screw for fixing said pin to said implant.

Preferably, the pin is made of a metallic material.

According to another aspect of the present invention, the same concerns an assembly comprising a pin and a fixing element for fixing said pin to an implant inserted in a patient’s jawbone, wherein said pin is made as described above. According to another aspect of the present invention, the same concerns a kit for making a supporting structure of a dental prosthesis suited to be fixed to a patient’s jawbone, wherein the kit comprises two or more pins suited to be fixed to respective implants inserted in said jawbone and at least one connection element for connecting two of said pins, wherein said two or more pins are made as described above.

According to a further aspect of the present invention, the same concerns a dental prosthesis suited to be fixed to a patient’s jawbone, said prosthesis comprising a supporting structure comprising two or more pins suited to be fixed to respective implants inserted in a patient’s jawbone, wherein said two or more pins are made as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, characteristics and objectives, as well as further embodiments of the present invention are defined in the claims and clarified below through the following detailed description making reference to the attached drawings; in the drawings, corresponding or equivalent characteristics and/or component parts of the present invention are identified by the same reference numbers. In particular, in the figures:

- Figure 1 shows an axonometric view of a pin according to a preferred embodiment of the invention;

- Figure 2 shows a side view of the pin of Figure 1 ;

- Figure 3 shows the sectional view along line III-III of Figure 2;

- Figure 4 shows a plan view of the pin of Figure 1 ;

- Figure 5 shows the sectional view along line V-V of Figure 4;

- Figure 6 shows the sectional view along line VI- VI of Figure 4;

- Figure 7 shows the pin of Figure 1 associated with a fixing screw;

- Figure 8 shows the fixing screw of Figure 7 separated from the pin;

- Figure 9 shows two pins of Figure 1 during a step of construction of a supporting structure for a dental prosthesis according to a preferred embodiment of the invention;

- Figure 10 shows a sectional view of the connection area of the two pins of Figure 9;

- Figure 11 shows a dental prosthesis made using the supporting structure of Figure 9 fixed to a patient’s jaw;

- Figure 12 shows a variant embodiment of Figure 1;

- Figure 13 shows the sectional view along line XTTT-XTTT of Figure 12;

- Figure 14 shows the sectional view along line XIV-XIV of Figure 12;

- Figure 15 shows a sectional view of the contact area of two tabs of two pins of Figure 12 adjacent to each other;

- Figure 16 shows two pins of Figure 1 during a step of construction of a supporting structure for a dental prosthesis according to a variant embodiment of the invention;

- Figure 17 shows an exploded view of Figure 16.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

A pin 1 for a supporting structure 50 of a dental prosthesis 100 according to a preferred embodiment of the invention is described below with reference to Figures from 1 to 6.

A dental prosthesis 100 obtained by using several pins 1 according to the invention is shown by way of example in Figure 11. The dental prosthesis 100 according to the embodiment illustrated is preferably constituted by two teeth Dl, D2 positioned side by side and comprises two pins 1 joined to each other to form the supporting structure 50 for said prosthesis 100.

The aesthetic/functional part of the tooth/teeth is built on the supporting structure 50, for example by laying one or more layers of a light curing composite material, for example dentine.

It is evident that the number of teeth of the dental prosthesis and/or the shape and/or position of the same within the dental arch of the patient will vary depending on the specific condition of the patient in question.

The pin 1 according to the invention preferably comprises a main body 2 developing longitudinally along a main axis X and comprises a connection area 4 suitable for connection to an implant, not illustrated, conveniently inserted in the jawbone M of a patient.

The connection area 4 is shaped in such a way as to be accommodated in the corresponding connection area of the implant used (not illustrated). Preferably, the pin 1 comprises also a first tab 10a extending transversally preferably along a tab axis Ya that is inclined with respect to the main axis X and a second tab 10b extending transversally preferably along a tab axis Yb that is inclined with respect to the main axis X.

Said tab axis Ya of the first tab 10a is preferably perpendicular to the main axis X and/or said tab axis Yb of the second tab 10b is preferably perpendicular to the main axis X.

The first tab 10a and the second tab 10b substantially extend from opposite sides with respect to the main axis X.

The first tab 10a comprises a first contact surface 12a suited to be placed in contact with a surface of a tab of an adjacent pin of the supporting structure 50, as shown, for example, in Figure 9.

According to an aspect of the present invention, the first contact surface 12a comprises at least one convex area.

Analogously, the second tab 10b comprises a first contact surface 12b suited to be placed in contact with a surface of a tab of an adjacent pin of the supporting structure 50. The first contact surface 12b preferably comprises at least one convex area.

The first contact surface 12a, 12b of the first tab 10a and of the second tab 10b preferably has the shape of a circle sector, considering a section plane perpendicular to the respective tab axis Ya, Yb (as shown in Figures 5 and 6).

The curvature radius of said circle sector is smaller than 100 mm, more preferably a curvature radius equal to 40 mm.

It is evident that in variant embodiments the convex shape can have any curved shape, meaning not necessarily the shape of an arc of a circle.

According to the preferred embodiment, the first tab 10a comprises also a second surface 14a opposite the first surface 12a with respect to the tab axis Ya. The second surface 14a is preferably plane.

Analogously, the second tab 10b comprises also a second surface 14b opposite the first surface 12b with respect to the tab axis Yb. The second surface 14b is preferably plane.

The main body 2 of the pin 1 comprises a through hole 6 suited to accommodate a fixing screw 8, better visible in Figure 8, suited to fix the pin 1 to the implant introduced in the patient’s jaw M.

As shown in Figures from 7 to 9, the fixing screw 8 preferably comprises a threaded lower end area 8a suited to become engaged in a respective nut thread provided on the implant, a centre area 8b extending across the through hole 6 of the main body 2 of the pin 1 and an upper end area 8c. The upper end area 8c is provided with a hole 8d, preferably in the shape of a hexagon, suited to receive a fixing tool, preferably a socket wrench.

In the preferred embodiment of the invention, the initial length of the upper end 8c of the fixing screw 8 projects with respect to the expected final height of the tooth Dl, D2.

The fixing screw 8 is used in the initial steps over its entire length, as shown, for example, in Figure 9, which illustrates a step of assembly and construction of the supporting structure 50 of the dental prosthesis 100. The fixing screws 8 are tightened, preferably through a socket wrench, to fix the pins 1 to the respective implants. In a successive step of construction of the dental prosthesis 100, the upper end areas 8c of the fixing screws 8 are cut to measure, so that they do not project beyond the top surface of the teeth Dl, D2.

According to an aspect of the present invention, the assembly and the construction of the supporting structure 50 of the dental prosthesis 100 include the operation of fixing the pins 1 in the respective implants and the successive connection of each pin 1 to the adjacent pin 1 positioned beside it. The connection is preferably obtained by welding a tab 10a, 10b of a pin 1 to a tab 10a, 10b of the adjacent pin 1, wherein said tabs to be welded are at least partially overlapped, as shown in Figure 9.

The welding process is preferably a spot welding process, wherein an electrode welding machine or a spot welder is used to generate the passage of a high intensity electric current between the two tabs 10a, 10b in contact with the two adjacent pins, melting and welding the tabs 10a, 10b in contact with each other. For this purpose, the tabs 10a, 10b of the pin 1 are made of a metallic material, preferably titanium. More preferably, the main body 4 and the tabs 10a, 10b are made in a single body, more preferably of a metallic material, for example titanium.

According to an advantageous aspect of the present invention, thanks to the convex shape of the contact surfaces 12a, 12b of the tabs 10a, 10b, during the welding step the contact area of the two tabs 10a, 10b is reduced substantially to a point (Figure 10), or substantially to a line, so that the melting current that flows through the two tabs 10a, 10b is concentrated in said contact point/line. The resulting weld is a high quality and high resistance weld, especially compared to the tabs of known type, where the contact surfaces are substantially plane and not punctiform, so that the current is disadvantageously distributed on a larger surface.

In order to favour the assembly and the construction of the supporting structure 50 of the dental prosthesis 100, which must follow the curve of the upper or lower set of teeth in the mouth, preferably the tabs 10a, 10b of the pins 1 are not aligned but slightly inclined with respect to each other.

Preferably, the tab axis Ya of the first tab 10a and the tab axis Yb of the second tab 10b are inclined with respect to each other by an angle ALPHA included between 90° and 179°, preferably between 140° and 165°, more preferably by an angle ALPHA equal to 150°, as shown in Figure 4.

Figures from 12 to 14 show a variant embodiment of the pin 1’ according to the invention. This embodiment differs from the embodiment described above in that also the second contact surface 14a’, 14b’ of the first tab 10a, more preferably also of the second tab 10b, comprises at least one convex area.

The second contact surface 14a’, 14b’ of the first tab 10a and of the second tab 10b preferably has the shape of a circle sector, considering a section plane perpendicular to the respective tab axis Ya, Yb (as shown in Figures 13 and 14). The curvature radius of said circle sector is smaller than 100 mm, more preferably a curvature radius equal to 40 mm.

When two tabs 10a, 10b of two adjacent pins 1 are welded together, both the mutual contact areas 14a’, 14b’ of the respective surfaces to be welded are advantageously convex, as can be observed in Figure 15.

While in the embodiment of the supporting structure described above two adjacent pins that make it up are directly connected to each other by welding the respective tabs, in a preferred variant embodiment the supporting structure may comprise two adjacent pins connected to each other through an auxiliary connection element 80, as shown in Figures 16 and 17.

In this case, preferably, the first contact surface 12a of the first tab 10a of a pin 1, the one on the left in Figure 16, is placed in contact with a contact surface 80a of the connection element 80 and the first contact surface 12b of the second tab 10b of an adjacent pin 1, the one on the right in Figure 16, is placed in contact with the contact surface 80a of the connection element 80.

The first tab 10a and the second tab 10b of the adjacent pins are then welded to the connection element 80.

Advantageously, thanks to the convex shape of the contact surface 12a, 12b of the tabs 10a, 10b of the two adjacent pins 1, during the welding step the contact area of the two tabs 10a, 10b with the connection element 80 is substantially reduced to a point or substantially reduced to a line.

In a preferred embodiment, even the contact surface 80a of the connection element 80 has a convex shape, more preferably curved, as can be seen in Figure 17. This shape further enhances the quality of the weld.

In variant embodiments, however, the contact surface of the connection element may even be plane.

The above clearly shows that the proposed pin allows the set objects to be achieved.

More specifically, it is clear that the proposed solution makes it possible to carry out a spot weld that is more resistant and lasts longer than the solutions of the known type.

Even though the invention has been described making reference to the attached drawings, during the construction step it can be subjected to modifications, all of which fall within the scope of the inventive concept expressed by the following claims and are therefore protected by the present patent.