WO2008096294A1

WO2008096294A1 - A dental implant

Info

Publication number: WO2008096294A1
Application number: PCT/IB2008/050339
Authority: WO
Inventors: Espedito Brescia
Original assignee: Apollonia & Fama Implant S.R.L.
Priority date: 2007-02-09
Filing date: 2008-01-31
Publication date: 2008-08-14
Also published as: ITFI20070035A1

Abstract

A dental implant, comprising a generically axial- symmetric endosteal body (11) with three different portions (12, 13, 14) in series with each other, respectively an apical portion (12), a central portion (13) and a coronal portion (14), a first common single- start threading (16) with a crest (18) being formed in the central portion (13) and the apical portion (12), while a second, multi-start threading (17) with at least two threads having respective crests (17a, 17b) is formed in said coronal portion (14), the roots of the threadings defining a core (C) of the implant. The single crest (18) of the first threading (16) develops into said at least two crests (17a, 17b) of the second threading (17) such that said root (C) of the implant progresses continuously between the first threading (16) and the second threading (17).

Description

TITLE

A DENTAL IMPLANT DESCRIPTION

Field of the invention The present invention generally refers to the field of dental implantology and more precisely it concerns a dental implant provided with a new type of thread. Background of the invention

As known, in modern dental implantology, dental implants are designed to be surgically inserted in place of the natural root of a lost tooth. The implant becomes osteointegrated and has the function of anchoring a dental prosthesis, in the same way as a natural root. The prosthesis can consist of a single artificial tooth or even of a complex structure with several artificial teeth. The prosthesis is joined to the implant by means of a so- called abutment, fixed by means of a retention screw to the dental implant.

Modern implantology has up to now developed different implant designs: threaded and non-threaded, submerged (for biphasic implantology) and transgingival (for monophasic implantology), cylindrical and "root- form", etc.

As far as the threaded implants are concerned, a typical structure thereof provides for an apical portion

(corresponding to the end of the implant which is positioned deeper into the bone) , a central portion and a coronal portion.

The outer thread of the implant has an important role in the design of the dental implant, which does not follow international isometric norms but is the result of appropriate research and development. In order to obtain optimal stability in the implant site, several implant types have, on the coronal portion, a double-start threading (or, in some cases, even triple-start or multi- start threadings) , with lower pitch and depth than the single-start threading which instead covers the central and apical body of the implant. The single-start threading of the central and apical implant ends on a cylindrical separation band separating the central portion from the coronal portion; the two thread crests of the coronal portion start on this same cylindrical band.

This configuration, as for instance shown in WO/03014654 or US2006/172258A1, leads to the definition of a significant discontinuity, such as a step or in any case a change in the diameter, between the root of the single- start threading and the root of the double-start threading (this latter root being substantially aligned with the surface of the aforesaid cylindrical separation band) . Since the implant-housing site prepared by a cutter has an axial-symmetric conformation, the abovementioned discontinuity results damaging, leading to the formation of tensions in the surrounding bone structure and excessive compressions on the implant body. Summary of the invention The main object of the present invention is to provide a dental implant which, when inserted in the implant site, prevents the formation of tensions both on the surrounding bone structure and on the same implant.

This and other objects, which will be more clear below, are achieved with a dental implant whose essential characteristics are defined in the first of the attached claims .

Brief description of the drawings The characteristics and advantages of the dental implant according to the present invention will be apparent from the following description of an embodiment thereof, given as exemplifying and non-limiting with reference to the attached drawings, wherein: figure 1 represents a front view of an implant according to the invention; figure 2 represents a longitudinal section view of a portion of the implant of figure 1 ; - figure 3 shows an enlarged axonometric view of a detail of the implant of figure 1; and figure 4 is a front view of the implant as in figure 1, in a schematical representation that shows the manufacture process of the implant, and highlights the substantial continuity of the core of the same. Detailed description of the invention

With reference to the above figures, a dental implant is indicated in its entirety at 10. Such implant 10 comprises an endosteal body 11, composed of three different portions in series with each other, respectively an apical portion of tapered shape 12, a substantially cylindrical central portion 13 and a coronal portion 14, also having a tapered shape.

The endosteal body 11 axially has a partially threaded seat 15, in which a corresponding abutment can be housed (not shown in the figures), of known type and for the support of a prosthesis.

On the apical portion 12 and on the central portion

13, a first threading 16 with a common single thread of substantially trapezoidal section, while on the coronal portion 14 a second, double-start threading 17 is present.

According to the invention, the single crest 18 of the first threading 16 continuously develops, substantially at the transition area between the central portion 13 and the coronal portion 14, into the two crests

(indicated at 17a and 17b) of the second, double-start thread 17.

In particular, such development is obtained by a progressive lowering of the single crest 18 of the first threading 16 towards the core of the implant, generating a groove 19 which internally splits the same crest into two separate threads, which materialise the two crests 17a and 17b of the second, double-start threading 17.

Such a result can for example be attained by realizing, in a first step, the first threading 16 over the entire side surface of the implant. As shown in figure 4, the first threading is carried out via a first shaped tool A. Subsequently, the groove 19 can be obtained by means of a second shaped tool B which enters on the first threading 16, progressively digging into the crest 18 while the implant rotates over a certain angle, in general equal to about 180°. Once the desired depth is reached, this will be maintained constant up to the end of the coronal portion 14, controlling the distance of the tool B from the core axis and also taking into account the increase of the core diameter. In the example of the figures, a transition zone is observed between the first and second threading, generically indicated at the letter I in figure 1, shaped due to a non-symmetric entry of the above mentioned tool B with respect to the crest 18. In such zone I, the beginning of the groove 19 is in fact visible, along with the start of one of the crests 17a of the second threading 17, while the other crest 17b is formed when, as its action continues, the tool B becomes more centred with respect to the crest 18.

On the other hand, it is clear that, according to the specific constructive solutions one may choose, of which the one indicated above represents only one possible example, the continuous transition between the single- start threading and the double- or multi-start threading can take on different dimensional and morphological features . In any case, as a result of the above described action of the two tools, the first threading 16 develops into the two crests of the second threading 17 while substantially maintaining the same overall dimensions, in particular in terms of pitch, width (the width of the single thread of the first threading 16 is substantially equal to the distance between the external flanks 17a' and 17b' of the two threads of the second, double-start threading 17) and slope of the threads (the slope of the external flanks 17a' and 17b' of the second threading 17 is substantially equal to the slope of the flanks of the single thread of the first threading 16) .

It should also be noted that the height of the two crests of the second threading 17 is lower than the height of the crest of the first threading 16. Moreover, the root of the threading, corresponding to the core of the implant, continuously progresses between the first threading 16 and the second threading 17. In practice, as more clearly represented by the marked line C of figure 4, there is no discontinuity of such root or core from the apex of the implant up to, and including, the coronal portion .

Thanks to the invention, a double-start threading is then obtained on the coronal portion 14 in practice as a continuation of the single-start threading formed in the apical 12 and central 13 portions, thus avoiding a discontinuity, such as a step, between the core of the central portion and the core of the coronal portion, all this assisting the reduction of the tensions generated around the endosteal body and on the surrounding bone when the implant is inserted in the implant site previously formed by the dental surgeon. By maintaining the same pitch and dimensions between the first threading and the second threading (the latter considered in its entirety) , the second threading can adapt itself to the grooving formed in the implant site by the first threading. The invention thus conceived is susceptible to numerous modifications and variants, all coming within the scope of the invention; moreover, all details can be substituted with other technically equivalent elements, without departing from the protective scope of the invention itself.

Claims

1. Dental implant, comprising a generically axial- symmetric endosteal body (11) with three different portions (12, 13, 14) in series with each other, respectively an apical portion (12), a central portion (13) and a coronal portion (14), a first common single- start threading (16) with a crest (18) being formed in said central portion (13) and said apical portion (12), while a second, multi-start threading (17) with at least two threads having respective crests (17a, 17b) is formed in said coronal portion (14), the roots of said threadings defining a core (C) of the implant, characterised in that the single crest (18) of said first threading (16) develops into said at least two crests (17a, 17b) of said second threading (17) such that said root (C) of the implant progresses continuously between the first threading (16) and the second threading (17).

2. The implant according to claim 1, characterised in that said second threading (17) is a double-start threading and the pitch of said second threading being substantially the same as said first threading (16).

3. The implant according to claim 1 or 2, characterised in that the development of said first single-start threading (16) into said second double-start threading (17) is substantially defined at the transition zone between said central portion (13) and said coronal portion (14) .

4. The implant according to the claim 2 and 3, characterised in that the development of said first threading (16) into said second threading (17) consists of a lowering of the crest (18) of the single thread of said first threading (16) towards the core of the implant, to generate an inner groove (19) which splits said single crest (18) into two parallel crests (17a, 17b) which materialise said two threads of said second threading (17) .

5. The implant according to one or more of the claims from 1 to 4, characterised in that the width of the thread of said first threading (16) is substantially equal to the distance between the external flanks (17a¹, 17b') of the two threads of said second threading (17) .

6. The implant according to one or more of the claims from 1 to 5, characterised in that the slope of the external flanks (17a¹, 17b') of the threads of said second threading (17) is substantially equal to the slope of the flanks of the thread of said first threading (16) .

7. The implant according to one or more of the claims from 1 to 7, characterised in that the height of the threads of said second threading (17) is lower than the height of the single thread of said first threading (16) .

8. The implant according to one or more of the claims from 1 to 7, characterised in that the cross- section of the single thread of said first threading (16) is substantially trapezoidal.

9. The implant according to any of the previous claims, wherein said apical portion (12) has a tapered shape, said central portion (13) has a substantially cylindrical shape and said coronal portion (14) also has a tapered shape.

10. A method for manufacturing a dental implant comprising a generically axial-symmetric endosteal body

(11) with three different portions (12, 13, 14) in series with each other, respectively an apical portion (12), a central portion (13) and a coronal portion (14), a first common single-start threading (16) with a crest (18) being formed in said central portion (13) and said apical portion (12), while a second, double-start threading (17) with two threads having respective crests (17a, 17b) is formed in said coronal portion (14), the roots of said threadings defining a core (C) of the implant, characterized in that, in a first step, said first threading (16) is carried out over the entire side surface of the implant via a first shaped tool (A) and, subsequently, said second threading (17) is carried out via a second shaped tool (B) which enters on said first threading (16), progressively digging into the crest (18) thereof, while the implant rotates over a certain angle, so as to obtain said two crests (17a, 17b) .

11. The method according to claim 10, characterised in that the development of said first single-start threading (16) into said second double-start threading (17) is substantially defined at the transition zone between said central portion (13) and said coronal portion (14) .

12. The method according to the claims 10 or 11, characterised in that the cross-section of the single thread of said first threading (16) is substantially trapezoidal.

13. The method according to any of the claims from 10 to 12, wherein said apical portion (12) has a substantially tapered shape, said central portion (13) has a substantially cylindrical shape and said coronal portion (14) also has a tapered shape.