GB1586729A - Dental implants - Google Patents

Description

(54) DENTAL IMPLANTS (71) We, PANTOMEDICAL GRIFO S.a.s. of Piazza Morlacchi, 24 Perugia, Italy, an Italian Limited Partnership Company, and Mr. Nicola Staffolani of Via Gigliarelli, 44 Perugia, Italy, - both of Italian nationality, do hereby declare the Invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following Statement: This invention relates to an implantable device for mounting a dental prosthesis.

It has been previously proposed to provide dental implants of the blade or screw type but such implants suffer from the disadvantage that new bony tissue is formed at the site of the surgical operation for the dental implant. It has also been ascertained that such tissue reformation never reproduces the normal dental-alveolar characteristics in the absence of an existing alveolar structure and parodontal ligaments. Research work has also shown that after an indefinite period, usually not more than 5 to 7 years, an osseous reabsorption nearly always occurs around the implant. Such reabsorption is caused by the fact that the implant is unable to sustain the masticatory stress or the microshocks caused in the oral cavity during speech, deglutitian and other voluntary and involuntary movement of the tongue and cheeks.

It is an object of the present invention to obviate or mitigate the aforesaid disadvantages.

According to the present invention there is provided an implantable device for mounting a dental prosthesis, comprising a mounting pin having one end free for receiving a prosthesis support and its other end ball-shaped and located in a socket of a pin holder in a manner permitting limited movement of the pin relative to the holder, and a base for fixing the pin holder in position including expansible hook formations adapted to anchor the base in a preformed cavity in the jaw bone.

Preferably, at least the base of the device is made of titanium or tantalum which is preferably heat treated for extra strength.

The socket may be lined with elastomeric material to permit limited movement of the pin relative to the holder and in this case the socket lining may be provided with a sheath of elastomeric material on the pin.

The end of the pin holder from which the pin protrudes is preferably of cylindrical external shape.

The hook formations of the base are preferably provided by two to five pointed projections of triangular, square or circular cross section each of which is inclined before expansion at an angle of not more than 45" relative to an axis of symmetry of the base.

The base preferably has a bore into which a spreader pin can be driven to expand the hook formations. The pin holder and the base are preferably in screw-threaded connection.

A single pin holder and mounting pin may be associated with a single base for placing the base in position. Alternatively the pin holder may be integral with at least two arms carrying respective bases in which case the undersides of the arms are preferably rounded.

The invention also extends to the combination of a device as defined above with a driver for driving a spreader pin into the base for the purpose of expanding the hook formations, said driver comprising a tube with one end threaded for screw engagement in a tapped bore of the base and its other end enlarged to form a flange, and a push-rod slidable in said tube under the influence of a driving force so as to force the spreader pin into the base. Preferably the push rod has an enlarged head to limit the driving stroke thereof.

The invention is also directed to a method of implanting a device as previously defined, otherwise than for the medical treatment of human beings to cure or prevent disease, comprising incising the gingival fibromucous membrane, drilling a cavity in the jaw bone, inserting the base in the cavity, driving a spreader pin into the base so as to expand the hook formations, and, if necessary, attaching the pin holder to the base.

In an appropriate constructional realisa tion the device of the invention when implanted has the advantage of providing a totally enclosed alveolus within the jaw bone whereby the saliva or other liquid that can pass through any gap between the mounting pin and the alveolus is prevented from contacting the jaw bone and/or the gum where it could produce infections.

Furthermore the prosthesis mounted on the pin performs more like a natural tooth since the stresses transmitted to the prosthesis are damped and appropriately distributed in relation to the characteristics of the bone in which the device is implanted by suitable selection of the number of hook formations of the base.

The invention will now be further described by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a side partially cutaway view of a first embodiment of implantable device of the present invention with the two portions thereof separated; Fig. 2 is a view similar to Fig. 1 but showing the two portions coupled to each other after the application of the prosthesis; Fig. 3 is an axial section of the base portion with a spreader pin and driver; Fig. 4 is a detail of Fig. 3 after spreading of the hook formations of the base portion in readiness for the reception of the upper portion of the device Fig. 5 is a side partially cutaway view of a second embodiment of the present invention with two base portions, and Fig. 6 is a plan top view of the device of Fig. 5.

Referring to the Figs. 1 to 4 concerning the first embodiment of the device wherein only one base portion or root assembly is provided the device comprises an upper portion generally indicated at 1 and a lower portion generally indicated at 2, the portion 1 comprising a body formed of two pieces that are side welded to each other. In the portion 1 a spheric socket or alveolus 3 is cut, the form of which may also be different e.g. elongated, ellipsoidal or similar; this alveolus extends upwards with a vertical duct 4 in order to form the housing seat of a pin 5 terminating in its lower portion with a spheric head 5a. The pin 5 protrudes from the body 1 with a length that is sufficient for holding means 6 supporting the tooth (not shown).The spheric head 5a and the pin 5 are covered by an elastomeric material 7 able to support resiliently the alveolus 3 in order to allow slight oscillations of the tooth with respect to the portion 2 forming the root assembly, to which the portion 1 will be screwed. To this end, the lower portion of the body 1 is provided with a cylindrical threaded end 8 that is screwed to a threaded seat 9 cut in the body 2 forming the root assembly.

It should be noted that instead of covering the pin 5 and its spheric head 5a with an elastomeric material 7 it is also possible to apply thereto an elastic sheath with a sealed interspace filled by a liquid.

The external wall of the portion 1 in the area above the median plane of the alveolus 3 and the spheric pin head 5a is substantially cylindrical so as to replace almost integrally the bone removed for the insertion of the device in order to avoid the reformation of new bony tissue and to stabilize the dental implant that is thus exactly fitted in the cavity provided in the bone for housing the prosthesis. The lower portion 2 of the device comprises a cylindrical upper portion 2a wherein the threaded seat is provided. The portion 2 has an external radius not greater than the maximum one of the portion 1. The bore 9 extends in a cavity comprising a first conical section 10, a cylindrical section 10a and a second conical section 10b, whose apex lies on the X-X axis of the device in correspondence with the lower base plane of the section 10a.In the illustrated embodiment, three or four tips 11 are formed in the body 2, which can be of triangular, circular or square cross section and whose lower edges 1 la initially form with the X-X axis of the root assembly an angle not greater than 45" so that the outstanding ends of such tips before assembling are substantially aligned with the cylindrical external wall of the portion 2. while each of said tips 11 forms a tang llb directed inwards and shaped as a guide cam that substantially extends up to the X-X axis.

The device is preferably made of heat treated titanium at least in the area corresponding to the portion 2 in order to give greater strength to the material of the tips 11. However, tantalum or any other material that offers substantially equivalent strength and does not give rise to the phenomenon of rejection from the organism can also be used.

The application of the device of Figs. 1 to 4 occurs as follows.

After an accurate preliminary radiography of the dental arches in order to put in evidence the area of thicker jaw bony tissue able to house the prosthesis without damaging the jaw sinuses and the mandible canal and after evaluation of the more suitable points for fixing the dental implant and the specific characteristics thereof, device will be applied whose portion 2 is provided with two or more tips 11 according to the load that can be sustained by the bone in the area concerned.

An incision of the gingival fibromucous membrane is effected in order to uncover the alveolar edge and by means of a drill a cavity is formed for receiving the device in which the portion 2 is to be inserted by embedding the same up to the provided depth by means of an instrument generally marked with 12 in fig. 3. Such an instrument is formed by a tubular means 14, the lower portion 14a of which is externally threaded in order to be screwed in the threaded seat 9, while the upper portion thereof is formed by a large grip flange 14b.In the bore 15 of the instrument 12 a little spreader pin is at first inserted and then a little shank or stem 17 is introduced, whose length is such that the portion of its head 1 7a initially projecting downwards has a length equal to the stroke of the pin when it is inserted among the tips 11, this pin 16 engaging the shaped tangs 1 1b thereof and causing the rotation of said tips out and upwards and their embedding in the bone. A good grip of said tips 11 in the bone is obtained without chipping if the embedding is carried out abruptly To this end it is sufficient to use a strong dental forceps with two arms 18, 1 8a the latter of which is fork-shaped.These arms are inserted between the flange 14a and the outstanding portion of the shank 17 by forcing quickly the head 17a of the shank 17 till the latter is pushed into the bore 15, which causes the insertion of the little pin 16 among the conically shaped tangs 11b acting as cams, that owing to the movement thereof force the tips 11 to rotate out and upwards. The length of the little pin 16 is such that the axial displacement thereof is sufficient to carry out the rotation of the tips 11, said little pin 16 then remaining firmly embedded among the tangs 1 lib (fig. 4). On the external surface of the tips 11 notches 19 are formed in the bending area of said tips 11 in order to facilitate the above mentioned operation.

The instrument 14 is thereafter removed and the upper portion 1 of the device is screwed in the seat 9 through the threaded end 8. The device is then ready for receiving the support 6 carrying the tooth or a bridge with more teeth.

The variant of the device shown in Figs. 5 and 6 is employed when it is necessary to distribute the load acting on the pin 5 with the spheric head 5a over more than one root assembly. Thus the upper portion, that forms the body in which the alveolus for receiving the pin 5 and its spheric head 5a is obtained, is identical to the upper portion of the first embodiment, while the lower portion is integral with a bridge 20 at which ends the threaded seats 9 of each root assembly are formed, said lower portion being obtained for constructive reasons separately from the upper one and successively fixed thereto. The equivalent parts of the two embodiments are marked with the same reference numbers. Obviously, the bridge 20 may be also replaced by a spider having three or four arms according to the individual requirements.In this case the device is formed so that it is integral with the root assembly at the end of the operation as shown in Figs. 5 and 6.

The application is carried out through an operation similar to that already described by providing in the bone a longitudinal cavity for the insertion of the root assemblies. It is opportune to round off the lower portion 20a of the bridge in order to avoid that the latter compresses the bone with a shearing stress.

If the available bony tissue has a limited height, e.g. in consequence of the individual age or the characteristics of the jaw bones, the portion that includes the alveolus 3 may be lowered in order to embody partially said alveolus in the bridge 20. Thus, the latter will be provided in the central and lower part with a spheric projection that will act as an intermediate support in order to reduce the unit load acting on the bone.

Although only two embodiments are illustrated, it is evident that it is possible to make a large range of variants that are suited to the different individual conditions. Therefore, not only can the device be provided with a root assembly with several tips, generally two to maxlmum five, but also a bridge can be provided with two or more arms, each with its respective root assembly.

The assembling of said bridge still involves the spreading of the tips 11 through the insertion of the little pin 16 by means of the above mentioned instrument 14. It should be noted also that the root assemblies of a bridge can have different heights due to the variable height of the bone so that the root assembly can be embedded at the more suitable depth.

However, the selection of the device more suitable to the various operative conditions among those of an equipment range according to the present invention can be easily effected by anyone skilled in the art.

WHAT WE CLAIM IS: 1. An implantable device for mounting a dental prosthesis, comprising a mounting pin having one end free for receiving a prosthesis support and its other end ball-shaped and located in a socket of a pin holder in a manner permitting limited movement of the pin relative to the holder, and a base for fixing the pin holder in position including expansible hook formations adapted to anchor the base in a preformed cavity in the jaw bone.

2. A device as claimed in claim 1, wherein at least the base is made of titanium or tantalum.

3. A device as claimed in claim 2, wherein the titanium or tantalum is heat treated for extra strength.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (15)

**WARNING** start of CLMS field may overlap end of DESC **. which the portion 2 is to be inserted by embedding the same up to the provided depth by means of an instrument generally marked with 12 in fig. 3. Such an instrument is formed by a tubular means 14, the lower portion 14a of which is externally threaded in order to be screwed in the threaded seat 9, while the upper portion thereof is formed by a large grip flange 14b.In the bore 15 of the instrument 12 a little spreader pin is at first inserted and then a little shank or stem 17 is introduced, whose length is such that the portion of its head 1 7a initially projecting downwards has a length equal to the stroke of the pin when it is inserted among the tips 11, this pin 16 engaging the shaped tangs 1 1b thereof and causing the rotation of said tips out and upwards and their embedding in the bone. A good grip of said tips 11 in the bone is obtained without chipping if the embedding is carried out abruptly To this end it is sufficient to use a strong dental forceps with two arms 18, 1 8a the latter of which is fork-shaped.These arms are inserted between the flange 14a and the outstanding portion of the shank 17 by forcing quickly the head 17a of the shank 17 till the latter is pushed into the bore 15, which causes the insertion of the little pin 16 among the conically shaped tangs 11b acting as cams, that owing to the movement thereof force the tips 11 to rotate out and upwards. The length of the little pin 16 is such that the axial displacement thereof is sufficient to carry out the rotation of the tips 11, said little pin 16 then remaining firmly embedded among the tangs 1 lib (fig. 4). On the external surface of the tips 11 notches 19 are formed in the bending area of said tips 11 in order to facilitate the above mentioned operation. The instrument 14 is thereafter removed and the upper portion 1 of the device is screwed in the seat 9 through the threaded end 8. The device is then ready for receiving the support 6 carrying the tooth or a bridge with more teeth. The variant of the device shown in Figs. 5 and 6 is employed when it is necessary to distribute the load acting on the pin 5 with the spheric head 5a over more than one root assembly. Thus the upper portion, that forms the body in which the alveolus for receiving the pin 5 and its spheric head 5a is obtained, is identical to the upper portion of the first embodiment, while the lower portion is integral with a bridge 20 at which ends the threaded seats 9 of each root assembly are formed, said lower portion being obtained for constructive reasons separately from the upper one and successively fixed thereto. The equivalent parts of the two embodiments are marked with the same reference numbers. Obviously, the bridge 20 may be also replaced by a spider having three or four arms according to the individual requirements.In this case the device is formed so that it is integral with the root assembly at the end of the operation as shown in Figs. 5 and 6. The application is carried out through an operation similar to that already described by providing in the bone a longitudinal cavity for the insertion of the root assemblies. It is opportune to round off the lower portion 20a of the bridge in order to avoid that the latter compresses the bone with a shearing stress. If the available bony tissue has a limited height, e.g. in consequence of the individual age or the characteristics of the jaw bones, the portion that includes the alveolus 3 may be lowered in order to embody partially said alveolus in the bridge 20. Thus, the latter will be provided in the central and lower part with a spheric projection that will act as an intermediate support in order to reduce the unit load acting on the bone. Although only two embodiments are illustrated, it is evident that it is possible to make a large range of variants that are suited to the different individual conditions. Therefore, not only can the device be provided with a root assembly with several tips, generally two to maxlmum five, but also a bridge can be provided with two or more arms, each with its respective root assembly. The assembling of said bridge still involves the spreading of the tips 11 through the insertion of the little pin 16 by means of the above mentioned instrument 14. It should be noted also that the root assemblies of a bridge can have different heights due to the variable height of the bone so that the root assembly can be embedded at the more suitable depth. However, the selection of the device more suitable to the various operative conditions among those of an equipment range according to the present invention can be easily effected by anyone skilled in the art. WHAT WE CLAIM IS:

1. An implantable device for mounting a dental prosthesis, comprising a mounting pin having one end free for receiving a prosthesis support and its other end ball-shaped and located in a socket of a pin holder in a manner permitting limited movement of the pin relative to the holder, and a base for fixing the pin holder in position including expansible hook formations adapted to anchor the base in a preformed cavity in the jaw bone.

2. A device as claimed in claim 1, wherein at least the base is made of titanium or tantalum.

3. A device as claimed in claim 2, wherein the titanium or tantalum is heat treated for extra strength.

4. A device as claimed in any one of

claims l to 3, wherein the socket is lined with elastomeric material to permit said limited movement of the pin relative to the holder.

5. A device as claimed in claim 4, wherein the socket lining is provided by a sheath of elastomeric material on the pin.

6. A device as claimed in any one of claims 1 to 5, wherein that end of the pin holder from which the pin protrudes is of cylindrical external shape.

7. A device as claimed in any one of the preceding claims, wherein the hook formations are provided by two to five pointed projections of triangular, square or circular cross section each of which is inclined before expansion at an angle of not more than 45" relative to an axis of symmetry of the base.

8. A device as claimed in any one of the preceding claims, wherein the base has a bore into which a spreader pin can be driven to expand the hook formations.

9. A device as claimed in any one of the preceding claims, wherein the pin holder and the base are in screw threaded connection.

10. A device as claimed in any one of claims 1 to 8, wherein the pin holder is integral with at least two arms carrying respective bases.

11. A device as claimed in claim 10, wherein the undersides of the arms are rounded.

12. An implantable device for mounting a dental prosthesis, substantially as herein described with reference to and as illustrated in Figs. l to 4 or Figs. 5 and 6 of the accompanying drawings.

13. In combination with a device as claimed in any one of the preceding claims, a driver for driving a spreader pin into the base for the purpose of expanding the hook formations, said driver comprising a tube with one end threaded for screw engagement in a tapped bore of the base and its other end enlarged to form a flange, and a push-rod slidable in said tube under the influence of a driving force so as to force the spreader pin into the base.

14. The combination as claimed in claim 13, wherein the push-rod has an enlarged head to limit the driving stroke thereof.

15. A method of implanting a device as claimed in any one of claims 1 to 12, otherwise than for the medical treatment of human beings to cure or prevent disease, comprising incising the gingival fibromucous membrane, drilling a cavity in the jaw bone, inserting the base in the cavity, driving a spreader pin into the base so as to expand the hook formations, and, if necessary, attaching the pin holder to the base.