WO2017199118A1

WO2017199118A1 - Dental system with implant and prosthetic crown that provides a system for removing said prosthetic crown from the implant

Info

Publication number: WO2017199118A1
Application number: PCT/IB2017/052589
Authority: WO
Inventors: Fausto SOMMOVIGO; Nicola SPAGGIARI
Original assignee: Sommovigo Fausto; Spaggiari Nicola
Priority date: 2016-05-20
Filing date: 2017-05-04
Publication date: 2017-11-23
Also published as: ITUA20163640A1

Abstract

System for removing a prosthetic crown from a dental implant of the type comprising an abutment to which said crown is cemented, comprising - a channel passing through said prosthetic crown open toward said implant, - a thrust element available between said prosthetic crown and said implant, - rotation and translation means for said thrust element, with direction of translation from said crown to said implant and/or vice versa, said thrust element, during the removal operation, abutting on said implant and at the opposite end abutting on said prosthetic crown; said thrust element being adapted to be rotated and translated by the dentist, at the time of the removal operation of said prosthetic crown, by means of rotation of a tool from the outside of said crown through said channel, so as to generate a thrust toward said crown, pushing on this latter and enabling its detachment.

Description

"DENTAL SYSTEM WITH IMPLANT AND PROSTHETIC CROWN THAT PROVIDES A SYSTEM FOR REMOVING SAID PROSTHETIC CROWN FROM THE IMPLANT"

DESCRIPTION

Technical field

The present invention relates to the field of dental implant systems and more in particular to a dental system or device with an integrated system or device for removing a cemented prosthetic crown from a dental implant.

The subject matter of the invention also includes a prosthetic crown inte- grating the removal system or device, an implant abutment integrating said removal system or device.

Moreover, the subject matter of the invention also includes a method for producing a system for removing a cemented prosthetic crown from the abutment associated with a dental implant, and to a method for removing a cement- ed prosthetic crown from the abutment associated with a dental implant.

State of the art

As is known, dental implants are currently widely utilized to replace one or more missing dental elements.

At the state of the art, prosthetics on implants can be produced with two different methods. The first provides for direct screwing of the false tooth (prosthetic crown) on the implant.

The screw that blocks the crown is threaded on the internal thread of the implant. The route of the screw that is parallel to the implant axis can fall within areas aesthetically visible when the patient smiles. In this case, the clinical choice is for cemented prosthetics. A prosthetic abutment, the artificial analog of a filed tooth on which the prosthetic crown is cemented, is screwed onto the implant.

The cement utilized is a material that passes from plastic state to rigid state after mixing and fills the spaces between crown and abutment to create an intimate bond between the two structures.

Other situations in which the cemented prosthesis is chosen are those in which several non-parallel implants exist, so as to facilitate an extended restora- tion that solidarizes the implants with one another.

The advantages of the screw retained prosthesis relate to the possibility of removing the work.

On the other hand, it requires greater precision and greater passivity. In fact, above all in the case in which it is screwed directly onto several implants, the prosthesis must contact all the implants simultaneously and maintain the bond with them without forcing.

The various advantages of the cemented prosthesis include those linked to aesthetics and to the fact that the union between the abutment screwed di- rectly onto the implant and the final cemented restoration is obtained through the interposition of cement, making it possible to produce an article with greater tolerance.

The disadvantages are linked to the presence of cement, the excesses of which can be difficult to remove, and to the difficulty or impossibility of removing the cemented restoration, which may become necessary if the abutment should loosen or in the case of infectious complications on the implant.

This can mean that the prosthetic crown has to be destroyed to gain access to the abutment underneath. In practice, unlike a simple "screw-retained" prosthesis, a cemented prosthesis cannot be "inspected".

In relation to the cemented prosthesis, there is currently no type of solution that enables safe non-destructive removal of the crown in the case of operation on the implant below.

Object and summary of the invention

The object of the present invention is to produce a dental system that en- ables the non-destructive removal of a cemented prosthetic crown from a dental implant.

With reference to this object, another important object of the present invention is to produce a dental system that simplifies the operation of the dentist on the mouth of the patient in the case of removal of the cemented prosthetic crown on implants.

The object of the present invention is to produce a dental system for removing a cemented prosthetic crown from a dental implant by means of a non- traumatic re-operation in the mouth of the patient.

Yet another object of the present invention is to produce a dental system that enables the removal of a prosthetic crown from a dental implant in a simple manner.

These and other objects, which will be more apparent below, are achieved with a dental system or device comprising a dental implant, provided with an abutment, and a prosthetic crown cemented to said abutment, characterized in that it comprises a system or device for removing said prosthetic crown from said implant, said removal system comprising

-a channel passing through said prosthetic crown open toward said implant,

-a thrust element available between said prosthetic crown and said implant,

-roto-translation means for said thrust element, with direction of transla- tion from said crown to said implant and/or vice versa,

said thrust element, during the removal operation, abutting on said implant and at the opposite end abutting on said prosthetic crown; said thrust element being adapted to be roto-translated by the dentist, at the time of the removal operation of said prosthetic crown, by means of rotation of a tool from the outside of said crown through said channel, so as to generate a thrust toward said crown, pushing on this latter and enabling its detachment.

Therefore, the invention also relates to a system or device for removing a prosthetic crown from a dental implant of the type comprising an abutment to which said crown is cemented, comprising

- a channel passing through said prosthetic crown open toward said implant,

- a thrust element available between said prosthetic crown and said implant,

- roto-translation means for said thrust element, with direction of transla- tion from said crown to said implant and/or vice versa;

the thrust element, during the removal operation, abuts on said implant and at the opposite end abuts on said prosthetic crown; said thrust element is adapted to be roto-translated by the dentist, at the time of the removal operation of said prosthetic crown, by means of rotation of a tool from the outside of said crown through said channel, so as to generate a thrust toward the same crown, pushing on this latter and enabling its detachment.

Preferably, the thrust element, available between said prosthetic crown and said implant, is

-adapted to be inserted through said channel, at the time of the removal operation of said prosthetic crown, between the prosthetic crown and the implant,

or

-already present between the implant and the prosthetic crown at the time of the removal operation of the crown.

Advantageously, the rotation and translation means comprise an internally threaded hole for swivel coupling to a counter-threaded pin-shaped portion pro- duced on the thrust element.

Preferably, the channel is aligned with the hole, i.e. the projection of said hole is contained in the projection of the channel or vice versa, and preferably the hole and the channel are coaxial.

According to preferred embodiments, the prosthetic crown comprises an inner portion made of reinforcing material, preferably metal or another high strength material; on this inner portion there is defined an impression for housing the coupling part to the abutment; at the interface between the inner portion of the impression and the abutment there is available the material for cementing the crown to the abutment.

According to preferred embodiments provided with threaded hole for roto- translation coupling with the thrust element, the hole is produced on a portion of the prosthetic crown in contact with the implant, and wherein the counter- threaded pin-shaped portion of the thrust element, during the removal step of the crown, is engaged with its thread on the thread of said hole and abuts with its end against said implant, so that a rotation action of the thrust element toward the implant, corresponds to a reaction force of the thrust element on the thread of the hole and consequently on the prosthetic crown, in the direction of detachment from the implant.

Preferably, the thrust element is the end of a tool, separate from the implant/prosthetic crown assembly, which can be utilized by the dentist to remove said crown; this end of the tool being adapted to be screwed into the hole by passing the same end through the channel. Alternatively, the thrust element can be a screw engaging on the hole, with its head housed in the channel; a tool being adapted to enter said channel and act on said head of the screw to rotate it. Alternatively, this screw may only be aesthetic, for example made of plastic material and of the same color as the tooth, and close the hole; at the time of the operation on the implant, the aesthetic screw is removed and the head of the tool that acts as thrust element is inserted.

Preferably, a temporary screw can be provided, positioned in the hole.

Preferably, the channel has a larger diameter with respect to the threaded hole.

According to preferred embodiments, the threaded hole is instead produced on the implant (preferably on the abutment screwed to the base body of the implant); the thrust element is housed in said hole and its counter-threaded pin-shaped portion is engaged on the thread of the same hole; during the removal step of the crown the end of the thrust element abuts with an end thereof against the prosthetic crown and abuts with its thread on the thread of the hole, so that a rotation action of the thrust element toward the crown corresponds to an attempt of translation thereof and therefore a force of the same thrust element on the prosthetic crown, in the direction of detachment from the implant.

Preferably, the threaded hole is coaxial to the slot for housing the head of the fixing screw of the abutment to the base body.

Preferably, the threaded hole is separate from the slot for housing the head of the fixing screw of the abutment to the base body.

Preferably, the thrust element is a threaded grub screw, the thrust end of which on the crown is provided with a seat for coupling with the end of a tool in- sertable through said hole and adapted to roto-translate this grub screw.

According to another aspect, the invention also relates to a prosthetic crown comprising an inner portion made of reinforcing material on which there is defined an impression for housing the coupling part cemented to the abutment of a dental implant; this crown comprises a through channel that extends from the masticatory surface toward the impression, open on said impression; the end part facing the impression of said channel is formed by a threaded hole for coupling to a threaded thrust element to be utilized to remove the prosthetic crown. This crown is preferably associated with a system for removing a crown from an implant according to one or more of the configurations described above.

According to another aspect, the invention also relates to a prosthetic abutment of a dental implant, on which a prosthetic crown is to be cemented, comprising a slot with a circular section open toward the prosthetic crown; this slot is internally threaded and adapted to house a threaded thrust element to be utilized to remove said prosthetic crown. This abutment is preferably associated with a system for removing a crown from an implant according to one or more of the configurations described above.

According to another aspect, the invention also relates to a method for producing a system for removing a cemented prosthetic crown from the abutment associated with a dental implant, which provides for

- producing a channel passing through said prosthetic crown,

-arranging a thrust element provided with thread between said prosthetic crown and said implant, so that said thrust element abuts on said implant and at the opposite end abuts on said prosthetic crown, so that said thrust element can, if required, be roto-translated acting on said through channel by means of rotation of a tool from the outside of said crown through said channel, so as to generate a thrust toward said crown, pushing on this latter and enabling the detachment thereof.

Preferably, the method provides that the thrust element is housed in a threaded hole produced on the abutment of said implant and is provided with means for coupling to the tool outside the crown.

Preferably, the method comprises a step of producing a portion of threaded hole in said channel, so that, if necessary, the end of a tool can be inserted in said channel engaging with its thread on the thread of said hole and abutting with its end against the implant, so that a rotation action of said tool toward said implant corresponds to a reaction force on the thread of said hole and consequently on said prosthetic crown, in the direction of detachment from said implant.

According to another aspect, the invention also relates to a method of removing a cemented prosthetic crown from the abutment associated with a dental implant, which provides for

- arranging a thrust element between the prosthetic crown and the implant, so that the thrust element abuts on the implant and at the opposite end abuts on the prosthetic crown,

- roto-translating, acting in a through channel produced through the prosthetic crown, the thrust element, by means of rotation of a tool from the outside of the crown through said channel, so as to generate a thrust toward the crown, pushing on this latter and enabling the detachment thereof.

This method enables the prosthetic crown to be removed from the implant without acting on the body of the patient, but limiting the operations only to the upper part of the dental system: Moreover, with this method the removability of the crown from the implant in a non-destructive manner can be verified before arranging the base body of the implant on a patient, and the removal operations can be practiced with the implant separated from the body of the patient, again in a non-destructive manner.

According to preferred embodiments, the thrust element is inserted between the prosthetic crown and the abutment before cementing the prosthetic crown to the implant; preferably the thrust element is inserted in a threaded hole produced on the abutment of the implant; during the removal step of the crown, the end of the thrust element abuts with an end thereof against the prosthetic crown and abuts with its thread on the thread of said hole, so that a rotation action of the thrust element toward the crown corresponds to a force of the same said thrust element on the said prosthetic crown, in the direction of detachment from said abutment.

According to other preferred embodiments, the thrust element is the end of a tool and is inserted between the prosthetic crown and the implant, through said channel, at the time of the removal operation of said prosthetic crown; preferably the threaded thrust element is coupled in a counter-threaded hole, produced on an inner portion made of reinforcing material of said prosthetic crown, open toward the implant; during the removal step of the crown, the end of the tool forming the thrust element engages with its thread on the thread of the hole and abuts with its end against the implant, so that a rotation and translation action of said thrust element toward said implant corresponds to a reaction force of said thrust element on the thread of said hole and consequently on said prosthetic crown, in the direction of detachment from said implant (advantageously the implant is formed by the abutment associated with the base body that forms the intraosseous portion).

According to another aspect, the invention also relates to an assembly formed by a dental implant with abutment and prosthetic crown cemented on said abutment, wherein the implant comprises a base body to be anchored to the bone of the patient, and reversible fixing means of the abutment to the base body; advantageously, this assembly comprises a system for removal of the crown from the implant according to one or more of the configurations described above.

Preferably, the reversible fixing means comprise a fixing screw arranged passing through the base of the abutment and engaged inside a corresponding hole produced in the base body.

Preferably, the abutment comprises a slot with a circular section open toward the prosthetic crown; on the bottom of this slot there is housed the head of the fixing screw of the abutment to the base body.

Brief description of the drawings

Further characteristics and advantages of the invention will become more apparent from the description of several preferred but non-exclusive embodiments thereof, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Fig. 1 represents an axial sectional view of a first embodiment of dental system with system for removing a prosthetic crown from an implant according to the invention;

Fig. 2 represents the system of Fig. 1 during the removal step of the prosthetic crown according to the invention;

Figs. 3a and 3b respectively represent the axial section and the plan view of the base body of the implant of Fig. 1 ;

Figs. 4a and 4b respectively represent the axial section and the plan view of the abutment of the implant of Fig. 1 ;

Figs. 5a and 5b respectively represent the axial section and the plan view of a thrust grub screw of the prosthetic crown of the assembly shown in Fig. 1 ;

Figs. 6a and 6b respectively represent the axial section and the plan view of the prosthetic crown of the assembly shown in Fig. 1 ;

Fig. 7 represents an axial sectional view of a second embodiment of dental system according to the invention, similar to the first embodiment of Fig. 1 , with the axis of the abutment inclined by 60° with respect to the axis of the im- plant;

Fig. 8 represents the system of Fig. 7 during the removal step of the prosthetic crown according to the invention;

Fig. 9 represents an axial sectional view of a third embodiment of dental system according to the invention;

Fig. 9a represents a portion of the same view as Fig. 9, highlighting the abutting position of the tool on the abutment, i.e. at the time of generation of the thrust that separates crown and abutment;

Fig. 10 represents the system of Fig. 9 during the removal step of the prosthetic crown, according to the invention.

Detailed description of an embodiment of the invention

Figs. 1 to 6 cited above show a dental system or device that comprises a dental implant 1 1 to be inserted in the bone H of the patient and a prosthetic crown 12 cemented on the implant 1 1 . Associated therewith is a system or device for removal of the prosthetic crown 12 from the implant 1 1 , described in de- tail below.

The dental implant 1 1 comprises a base body 13, to be inserted in the bone, and an abutment 14, fixable, by means of reversible fixing means 15, to the base body 13, which projects from the bone of the patient.

The base body 13 has a shape tapered from a connection face 16 to the abutment 14 to the tip to be inserted in the bone. The lateral surface of the base body is provided with a thread 13A for anchoring to the bone.

The connection face 16 is provided with an anti-rotation shaped seat 17, for example polygonal, and preferably hexagonal, in shape, adapted to accommodate the shank 18 of the abutment 14 that therefore couples to the base body without being able to rotate.

The bottom of the seat 17 is provided with a threaded hole 19, adapted to accommodate a fixing screw 20 of the abutment to the base body 13.

The shank 18 forms the base of the abutment 14 and the fixing screw 20 is arranged passing through the base of said abutment and is engaged in the hole 19.

In particular, the abutment 14 comprises a slot 21 , in this example with a circular section, open toward the prosthetic crown 12. On the bottom of the slot 21 there is housed the head 22 of the fixing screw 20.

According to the invention, the system for removing the crown 12 from the implant 1 1 enables access to the implant in cases in which it is necessary to operate thereon, once implanted in the bone.

The prosthetic crown 12 comprises through a channel or duct or opening

23, open toward the implant 1 1 . This channel, when the implant is installed, is closed on the masticatory surface of the crown by an appropriate dental material, of known type.

The removing system, or device, comprises a thrust element 25 available between the prosthetic crown 12 and the implant 1 1 .

Moreover, the removal system comprises roto-translation means 26 for the thrust element 25, with direction of translation from the prosthetic crown 12 to said implant 1 1 and/or vice versa, as better described below.

In practice, during the removal operation, the thrust element 25 abuts on the abutment 14 of the implant 1 1 and at the opposite end abuts on the prosthetic crown 12, so that, by means of a tool U handled from the outside of the crown 12 (see Fig. 2), the dentist roto-translates the thrust element 25, which, abutting on the crown 12, generates a thrust toward the same, overcoming the fixing strength produced by cementing, enabling the detachment of the prosthetic crown from the abutment 14.

In this example, the thrust element 25 is already present between the im- plant 1 1 and the prosthetic crown 12 at the time of the removal operation of the crown, having been arranged in this position at the time of completing the implant/crown assembly on the mouth of the patient.

The rotation and translation means 26 comprise an internally threaded hole 27 for swivel coupling to a counter-threaded pin-shaped portion 25A of the thrust element 25. In this example, the hole 27 is coaxial to said slot 21 for housing the head 22 of said fixing screw 20 of the abutment 14 to the base body 13; in particular, in this example, the slot 21 is a continuation of the threaded hole 27.

In this example, the thrust element 25 is a threaded grub screw provided with an impression for a tool such as a screwdriver, Allen key, etc., so that the whole of the lateral surface thereof corresponds to the counter-threaded pin- shaped portion 25A.

In this example, the channel 23 is aligned with the hole 27, i.e. the projection of the channel 23 is contained in the projection of the hole 27. In practice, the channel has a smaller diameter with respect to the threaded hole. More in particular, the hole 27 and the channel 23 are coaxial.

Again in this example, the axis of the screw 20 is parallel to the axis of rotation of the thrust element 25 and more preferably they are coincident, i.e. coaxial.

The prosthetic crown 12 comprises an inner portion 12A made of reinforcing material, preferably metal. On this inner portion 12A there is defined an impression 12B for housing the coupling part of the abutment 14; at the interface between the inner portion 12A of the impression 12B and the abutment 14 there is available the material for cementing the crown to the abutment (the material is not indicated in the figures, for graphical simplicity).

From the point of view of operation, the dentist inserts the base body 13 of the implant 1 1 in the bone of the patient. Subsequently, he/she associates the abutment 14 with the base body, blocking it with the screw 20. Subsequently, he/she tightens the grub screw/thrust element 25 of the threaded hole 27 and cements the prosthetic crown 12 to the abutment 14.

In the case in which operations are required on the implant, the crown 12 must be removed to access the screw 20. To do so, the dentist removes the covering material of the channel 23 and inserts the tip of a tool U in the channel, causing it to engage with the impression of the grub screw/thrust element 25. The dentist rotates the tool, roto-translating the grub screw 25 toward the crown. Therefore, the grub screw abuts against the crown 12 and is abutting on the thread of the hole 27 (is engaged on this thread). Therefore, a rotation action of the grub screw 25 corresponds to a movement thereof toward the crown. However, the grub screw is prevented from translating by the same crown and therefore a thrust F is generated thereon, which tends to separate the crown from the abutment, overcoming the cementing force.

Figs. 7 and 8 show a second embodiment of the invention (the same reference numerals have been used as they indicate substantially the same components as the previous example), varying with respect to the case described above in that the hole 27 in which the thrust element 25 is housed is separated from the slot 21 and in that the axis of the screw 20 (and therefore the axis X of the base body 13) is inclined (for example by 60°) with respect to the axis Y of rotation of the thrust element 25. In practice, access to the screw 20 is different from access to the thrust element 25. Nonetheless, the operating method for action on the system is the same as described above.

Figs. 9, 9a and 10 show a third embodiment of the invention, varying sig- nificantly with respect to the examples indicated above. In this case the thrust element is not inserted in a slot produced on the implant but into a hole produced on the prosthetic crown. The reference numerals of similar components in the same positions are the same as in the previous examples.

Also in this case, the prosthetic crown 12 comprises a through channel 23, open toward the implant 1 1 . This channel, when the implant is installed, is closed on the masticatory surface of the crown by an appropriate dental material, of known type. Also in this case, the removal system or device 124 of the prosthetic crown 12 comprises a thrust element 125 available between the prosthetic crown 12 and the implant 1 1 . However, unlike the previous cases, in this example the thrust element 125 is adapted to be inserted through the channel 23, be- tween the prosthetic crown and the implant 1 1 , only at the time of the removal operation of the prosthetic crown 12.

Similarly, the removal system or device 24 comprises roto-translation means 26 for the thrust element 25, with direction of translation from the prosthetic crown 12 to said implant 1 1 and/or vice versa, as better described below.

The rotation and translation means 26 comprise an internally threaded hole 127 for swivel coupling to a counter-threaded pin-shaped portion of the thrust element 125.

As mentioned, the threaded hole 127 is produced on the prosthetic crown 12, and more in particular on the inner portion 12A made of reinforcing material, on which there is defined the impression 12B for housing the coupling part of the abutment 14 (at the interface between the inner portion 12A of the impression 12B and the abutment 14 there is available the material for cementing the crown to the abutment).

The threaded hole 127 is produced as a continuation of the channel 23 and therefore they are aligned, i.e. the projection of the hole is contained in the projection of said channel, preferably the hole 127 and the channel 23 are coaxial (have a same axis Y). More preferably, in this example the diameter of the channel 23 is larger than the diameter of the hole 127.

Moreover, in this example, the axis Y of the hole 127 and of the channel 23 is parallel to the axis X of the fixing screw 20 of the abutment 14 to the base body 13, but they are offset from each other, i.e. they are not coaxial.

For example, the thrust element 125 is the end of a tool K, separate from the implant/prosthetic crown assembly, that can be utilized by the dentist to remove the crown; this end of the tool is a counter-threaded pin-shaped portion 125A and is adapted to be screwed into the hole 127, passing through the channel 13.

In practice, this counter-threaded pin-shaped portion 125A of the thrust element 125 is inserted in the channel 13, engages with its thread on the thread of the hole 127 and abuts with its end against a portion of the implant (the abutment 14), so that a rotation action of the tool K by the dentist, or a roto- translation of the thrust element toward the implant (i.e. to move the end of the thrust element 125 toward the abutment 14) corresponds to a reaction force of the same thrust element 125 on the thread of the hole and consequently on the prosthetic crown 12, in the direction of detachment from the abutment 14. This thrust F is able to overcome the resistance offered by the cementing force between crown and abutment.

In other examples, not shown in the figure, in the hole 127 there can be housed a screw, which acts as thrust element. In practice, the screw is engaged on said hole 127, with its head housed in said channel. The tool is adapted to enter the channel 23 and to act on the head of the screw to rotate and translate it and enable it to abut on the abutment and therefore to obtain a reaction on the thread of the hole 127 or on the crown, enabling the detachment thereof. Alternatively, this screw may only be aesthetic, for example made of plastic material and of the same color as the tooth, and close the hole 127; at the time of the operation on the implant, the aesthetic screw is removed and the head of the tool K that acts, as described, as thrust element, is inserted.

From a point of view of implementation, the system for removing the cemented prosthetic crown from the abutment provides for producing a channel passing through the prosthetic crown, and arranging the thrust element provided with thread between the prosthetic crown and the implant.

According to the variants indicated above, in this method of implementa- tion the thrust element is housed in a threaded hole produced on the abutment of the implant and is provided with means for coupling to the tool outside the crown. Otherwise, the method comprises a step of producing a portion of threaded hole in the channel, so that, if required, the end of a tool can be inserted in said channel abutting with its thread on the thread of the hole and abutting with its end against the implant.

It is understood that the drawing only shows possible non-limiting embodiments of the invention, which can vary in forms and arrangements without however departing from the scope of the concept on which the invention is based. Any reference numerals in the appended claims are provided purely to facilitate the reading thereof, in the light of the above description and accompanying drawings, and do not in any way limit the scope of protection.

Claims

1 ) Dental system comprising a dental implant, provided with an abutment, and a prosthetic crown cemented to said abutment, characterized in that it provides a system for removing said prosthetic crown from said dental implant, comprising

- a channel passing through said prosthetic crown open toward said implant,

- a thrust element available between said prosthetic crown and said implant,

- roto-translation means for said thrust element, with direction of translation from said crown to said implant and/or vice versa,

2) System according to claim 1 , wherein said thrust element available between said prosthetic crown and said implant is

- adapted to be inserted through said channel, at the time of the removal operation of said prosthetic crown, between said prosthetic crown and said implant,

or

- already present between said implant and said prosthetic crown at the time of the removal operation of the crown.

3) System according to claim 1 or 2, wherein said roto-translation means comprise an internally threaded hole for swivel coupling to a counter- threaded pin-shaped portion of said thrust element.

4) System according to claim 3, wherein said channel is aligned with said hole, or the projection of said hole is contained in the projection of said channel or vice versa, preferably said hole and said channel are coaxial.

5) System according to one or more of the preceding claims, wherein said abutment comprises a slot with a circular section open toward said prosthetic crown.

6) Dental system according to one or more of the preceding claims, wherein said prosthetic crown comprises an inner portion made of reinforcing material, preferably metal, on said inner portion there being defined an impression for housing the coupling part of said abutment; at the interface between said inner portion of the impression and said abutment there being available the material for cementing said crown to the abutment.

7) System according to one or more of claims 3 to 6, wherein said hole is produced on a portion of said prosthetic crown in contact with said implant, and wherein said counter-threaded pin-shaped portion of said thrust element, during the removal step of the crown, engages with its thread on the thread of said hole and abuts with its end against said implant, so that a rotation action of said thrust element toward said implant corresponds to a reaction force of said thrust element on the thread of said hole and consequently on said prosthetic crown, in the direction of detachment from said implant.

8) System according to claim 7, wherein said thrust element is the end of a tool, separate from the implant/prosthetic crown assembly, that can be utilized by the dentist to remove said crown; said end of the tool being adapted to be screwed into said hole by passing the same end through said channel of the crown.

9) System according to claim 7, wherein said thrust element is a screw engaging on said hole, with its head housed in said channel; a tool being adapted to enter said channel and act on said head of the screw to rotate it.

10) System according to claim 7, 8 or 9, wherein said channel has a larger diameter with respect to said threaded hole.

1 1 ) System according to one or more of claims 3 to 6, wherein said threaded hole is provided on said implant, said thrust element being housed in said hole and its said counter-threaded pin-shaped portion is engaged on the thread of said hole; during the removal step of the crown the end of said thrust element abuts with an end thereof against said prosthetic crown and abuts with its thread on the thread of said hole, so that a rotation action of said thrust ele- ment toward said crown corresponds to a force of the same said thrust element on said prosthetic crown, in the direction of detachment from said implant.

12) System according to claims 7 and 1 1 , wherein said threaded hole is coaxial to said slot for housing the head of said fixing screw of the abutment to the base body.

13) System according to claim 1 1 , wherein said threaded hole is separate from said slot for housing the abutment.

14) System according to claim 1 1 , 12 or 13, wherein said thrust element is a threaded grub screw, the thrust end of which on the crown is provided with a seat for coupling with the end of a tool insertable through said hole and adapted to roto-translate said grub screw.

15) Prosthetic crown of the type to be cemented to an abutment of a dental implant, comprising a masticatory surface and an inner portion made of reinforcing material, on which there is defined an impression for housing the abutment of the dental implant, characterized in that it comprises a through channel that extends from the masticatory surface toward said impression, open on said impression; the end part toward said impression of said channel being formed by a threaded hole for coupling to a threaded thrust element to be utilized to remove said prosthetic crown, preferably related to a system for remov- ing a dental system according to one or more of the preceding claims.

16) Prosthetic abutment of a dental implant, on which a prosthetic crown is to be cemented, comprising a slot with a circular section open toward the prosthetic crown, said slot being internally threaded and adapted to house a threaded thrust element to be utilized to remove said prosthetic crown, prefera- bly related to a system for removing a dental system according to one or more of the preceding claims.

17) Method of producing a system for removing a cemented prosthetic crown from the abutment associated with a dental implant, which provides for producing a channel passing through said prosthetic crown,

- arranging a thrust element provided with a thread between said prosthetic crown and said implant, so that said thrust element abuts on said implant and at the opposite end abuts on said prosthetic crown, so that said thrust element can, if required, be roto-translated acting on said through channel by means of rotation of a tool from the outside of said crown through said channel, so as to generate a thrust toward said crown, pushing on this latter and enabling the detachment thereof.

18) Method according to claim 17, wherein said thrust element is housed in a threaded hole produced on the abutment of said implant and is provided with means for coupling to said tool outside the crown.

19) Method according to claim 17, comprising a step of producing a portion of threaded hole in said channel, so that, if required, the end of a tool can be inserted in said channel abutting with its thread on the thread of said hole and abutting with its end against the implant, so that a rotation action of said tool toward said implant corresponds to a reaction force on the thread of said hole and consequently on said prosthetic crown, in the direction of detachment from said implant.

20) Method of removing a cemented prosthetic crown from the abutment associated with a dental implant, which provides for

- arranging a thrust element between said prosthetic crown and said implant, so that said thrust element abuts on said implant and at the opposite end abuts on said prosthetic crown,

- roto-translating, acting in a through channel produced through the prosthetic crown, said thrust element, by means of rotation of a tool from the outside of said crown through said channel, so as to generate a thrust toward said crown, pushing on this latter and enabling the detachment thereof.

21 ) Method according to claim 20, wherein said thrust element is inserted between said prosthetic crown and said implant before cementing of the prosthetic crown to the implant; preferably said thrust element is inserted in a threaded hole produced on the abutment of said implant; during the removal step of the crown the end of said thrust element abuts with an end thereof against said prosthetic crown and abuts with its thread on the thread of said hole, so that a rotation action of said thrust element toward said crown corresponds to a force of the same said thrust element on said prosthetic crown, in the direction of detachment from said abutment.

22) Method according to claim 20, wherein said thrust element is the end of a tool and is inserted between said prosthetic crown and said implant, through said channel, at the time of the removal operation of said prosthetic crown; preferably said threaded thrust element is coupled in a counter-threaded hole, produced on an inner portion of said prosthetic crown made of reinforcing material, open toward the implant; during the removal step of the crown, said end of the tool forming said thrust element being engaged with its thread on the thread of said hole and abutting with its end against said implant, so that a rota- tion action of said thrust element toward said implant corresponds to a reaction force of said thrust element on the thread of said hole and consequently on said prosthetic crown, in the direction of detachment from said implant.