DESCRIPTION

FIELD OF THE INVENTION

This invention is related to a dental implant.

In particular it relates to an endosteal dental implant comprising of a body having a transmucosal neck with a surface configured to be mated to a stump.

The implant can be anchored to dental prostheses, such as artificial teeth, crowns, dental bridges, dentures.

BACKGROUND OF THE INVENTION

Known implants have a part anchored within the bone and a part external to the bone, and their use allows to adapt the dental prosthesis to the profile of the mucosa that covers the bone.

Basically, there are known four types of implants.

A first type (known as "bone level") provides for a screw which is inserted completely within the bone without protruding from it. The screw is connected to a prosthetic structure called stump, which acts as a support for the anchorage of the dental prosthesis.

A second type (known as "tissue level") provides for a transmucosal external bone connection. These implants comprise a screw which is partially inserted into the bone and partially external to the bone and pierces the gingiva. In the above implants, the part of the screw outside the bone can reach the gum surface or protrude from it. Also in this case, the screw is connected to a stump for anchoring the dental prosthesis.

A third type of implants relates to monoblock systems, consisting of a single piece where a part is screwed into the bone and a part is external to the bone that constitutes the support for anchoring the dental prosthesis.

A fourth type is related to the transmucosal systems comprising an endosteal screw as a single piece with a transmucosal part with a coronally inclined surface to which a stump can be screwed.

In the embodiment of the first typology of implants, the screw is completely screwed into the bone so that the upper surface of the screw is aligned with the bone. The screw is connected to a prosthetic stump, optionally consisting of several pieces. The stump must have a height such as to go beyond the mucosal layer and emerge on the outside of it. The outer part of the stump is used as a support for the construction of dental prostheses. This type of implant is widely used as it allows to connect the stump to the screw at the bone. The disadvantages are, however, that bone loss occurs locally as the connection between the screw and the stump is an attack point for bacteria and / or the development of inflammatory factors, to which the human body responds by reducing bone tissue.

Examples of implants belonging to this first type are, for example those produced and marketed by Nobel Biocare® under the NobelSpeedy™ and NobelReplace™ brand. Other examples of the above implant types are bone level systems marketed by Frialit® or by DentSply®. Further examples of this type of implant are those marketed by Bicon™, in which the screw has an enlarged upper part with a terminal conical section. Other implants belonging to the above mentioned type are bone level implants marketed by Straumann® and implants known as Straumann® Bone Level implants.

To overcome the loss of bone tissue, "tissue level" implants as described above were developed, in which the connection between the screw and the stump is external to the bone and is located at the level of the mucosal surface or is external to it. Such implants are made up by a screw of which one part is screwed into the bone and a part, called the transmucosal segment, remains outside the bone and has the upper terminal end at the level of the mucosal surface or is external to it. A stump is connected to the screw. The outer part of the stump is used as a support for making dental prostheses.

In this type of implants, the connection between the screw and the stump is sufficiently distant from the bone to prevent the development of bacteria and / or of inflammatory factors from compromising the bone. These systems feature a shoulder which constitutes the bottom point from which it is possible to begin the construction of dental prostheses.

Examples of these systems are those marketed by Straumann®, such as the so-called standard® and plus® standards tissue-level systems.

Using this type of implants places constraints on the user when making dental prostheses, as these can be made only from the point of connection between the terminal part of the screw and the stump.

The above constitutes a disadvantage as when there are surface irregularities of the mucosa, dental prostheses cannot adapt perfectly to the profile of the mucosa, leaving uncovered a part of the transmucosal segment of the screw, with a considerable aesthetic damage.

Furthermore, if the implant is inserted too deep and / or the mucous membrane is too thick, it was observed that the connection between the screw and the stump is completely inside of the mucosa with consequent problems of cementation of dental prostheses.

Monoblock systems belonging to the third type are made up by a single screw/stump block, and feature an upper end that emerges from the mucosa and constitutes the stump to which dental prostheses are to be connected.

In the above type of system, it is difficult to adapt the part of the block corresponding to the stump in the specific dental prosthesis operation to be undertaken. It is also not possible to change the angle of the part corresponding to the stump.

Examples of monoblock products are the Monotype™, manufactured and marketed by

Straumann™.

The fourth, and more powerful type of implant, comprises an endosteal and a transmucosal part made of a single piece; the transmucosal part is tapered in the coronal direction.

On the narrow base of the trunk cone it is possible to connect a stump by using a through screw. The latter implants have the advantage of not having the connection between the stump and bone screw located in the vicinity of the bone. The above systems also offer the possibility of positioning the closing edge of the prosthetic crown, without distinction, on the stump or on the truncated cone segment of the system, depending on aesthetic or functional requirements.

A limitation of these systems is provided by the inclination of the transmucosal truncated cone segment (also called the transmucosal neck).

In fact, in systems currently on the market, the transmucosal conical segment has straight sloped

(Vertical-Neck biotype implants) or concave surfaces (Prama Sweden & Martina implants).

In Prama Sweden & Martina implants, the surfaces of the transmucosal segment are concave, making it even more difficult to carry out implants with bridges in the event of incorrect parallels between these implants.

Regarding Vertical-Neck Biotype implants, the possibility of carrying out bridge prostheses using the transmucosal cone trunk, depends on the positioning of the systems themselves. Indeed, the truncated cone has a sloping surface at about 10° to the axis of the system; then to be able to carry out implants with prostheses on the transmucosal truncated cone segment of the various implants positioned for making bridge prostheses, the axes of the respective systems must be positioned with a relative maximum inclination of 20°.

On the other hand, if the transmucosal segment of a truncated cone was made with an inclination greater than 10° (relative to the system axis), equal to the diameter of the large base and the diameter of the narrow base of the transmucosal truncated cone, the height of the transmucosal neck would be not sufficient to reach the height of the mucosa.

In this type of system, there are basically three objectives to be achieved: the first objective is to have a height of the transmucosal neck of at least 2mm-3mm, which corresponds to the biological height of the gum in order to allow the crossing.

The second objective is to have a sufficient diameter of the narrow and coronal base of the transmucosal cone that allows to insert stump fastening means and torsional coupling systems such as hex and octagon heads, trefoil, etc.

The third objective is to have an inclination of the transmucosal neck surfaces such as to allow the adaptation of the prosthesis to the bridge even in the event of various systems positioned for the support of the prosthesis to bridge being inserted into the bone with non-parallel axes between them.

The greater inclination of surfaces of the transmucosal cone, the greater the parallelism difference between bridge support implants may be. In fact, if the transmucosal neck is particularly inclined, there are no bridge assembly problems due to undercut parts.

SUMMARY OF THE INVENTION

Purpose of this invention is to provide an improved dental implant type, which allows to facilitate the assembly of the prosthesis to bridge even in the event of lack of alignment between the axes of several systems used for building a prosthetic bridge. A further goal of the invention is to provide a system that facilitates total coverage of metal parts of the implant screw exposed out of the gingiva and the abutment, also in the presence of an imperfect positioning of the implants used for the bridge prosthesis itself.

This and other goals are achieved by a dental implant in conformity with the technical teachings of the accompanying claims.

An advantage of this present invention consists in the conformation of the transmucosal segment, which has a taper at increasing angles in the cervico-coronal direction.

In fact, in the case of individual systems, to be used for single crowns, the angle of the transmucosal segment is not relevant for the insertion of the subgingival crown and for the resulting coverage of metal parts of the system for aesthetic purposes. Even in the case of longer implants placed in parallel the problem does not exist, as the bridge can be inserted without any undercuts preventing this.

Instead, in the case of longer implants placed with different insertion axes, as a result of this invention, transmucosal segments will have less angled parts that may be undercut but that will be more submerged by the gum, so there will be need for them to be covered by the prosthesis. Instead, the non- undercut part, i.e. opposite to the undercut part, will be more exposed out of the gingiva but may also be covered by the crown in the less angled part of the transmucosal segment.

Furthermore, it must take into account that, in practice, the transmucosal segment is never covered up to the bone, but only partially for cosmetic purposes of covering metal parts. So, if hypothetically the gum is 2,5 mm thick, the transmucosal segment will be covered by the crown for the first millimetre, leaving 1,5 mm of transmucosal segment free from the crown down to the bone, in order to maintain a biological compliance distance to avoid inflammatory stimuli to the bone.

BRIEF DESCRIPTION OF THE FIGURES

Further characteristics and advantages of the invention will become apparent from the description of a preferred but not exclusive form of the device, shown by way of example and not of limitation in the accompanying drawings, in which:

Figure 1 is a simplified axial section of a system according to this invention, where section lines (as well as in the other figures) are omitted for simplicity;

Figure 2 is a simplified sectional view of a pair of systems intended to support a bridge;

Figure 3 is a simplified sectional view of an alternative form of embodiment of the system according to the present invention;

Figure 4 explains in simplified manner a design diagram of a different embodiment of the system;

Figure 5 and Figure 6 are alternative embodiments;

Figure 7 is yet another different embodiment also explained from the design point of view.

DETAILED DESCRIPTION OF THE INVENTION With reference to the above mentioned figures, a dental implant is shown, generally indicated by the reference number 1.

The dental implant 1 comprises an endosteal body 2 (fully visible only in Figure 2) from which extends a tapered shape transmucosal neck 3 extends.

The endosteal body 2 and the transmucosal neck 3 are made as a single piece, for example in titanium, zirconium oxide, ceramic or other metals or biocompatible materials.

The endosteal body 2, when used, is intended to be screwed, inserted by pressure, inside a bone O, while the transmucosal neck 3 is intended to be positioned inside of the gingiva G, with a free end 4 projecting from the latter, or slightly below the level of the gingiva.

In this text, reference is made to the various parts of the dental implant with a name that comes from their primary function. Thus the endosteal body 2, is primarily designed to be screwed into the bone by means of a 2B thread, pressure inserted if there is no thread. However, during the final system, it could provide for some parts to be positioned in a transmucosal area, or in the gum. Similarly the transmucosal neck 3 may, depending on the case, provide for some of its parts to be on the edge or even slightly inside the bone.

The endosteal body 2, according to the various embodiments, can provide a perfectly smooth, completely rough or partially smooth and partially rough surface.

Even the transmucosal neck can have a smooth, rough or machined surface (lathed).

It is also possible to provide various degrees of roughness, colour or surface treatment (such as anodizing), between the transmucosal neck 3 and the endosteal body 2. This makes placing the implant easier and more accurate, giving doctors additional visual cues that helps during the operation.

It is also possible to provide a different colouration / surface treatment of the various parts of the transmucosal neck 3 with different angles. This would give the doctor a clear visual indication of the part of the transmucosal neck 3 which is more or less angled and which may possibly be sunk into the bone (or the less angled part with respect to axis A).

The transmucosal neck have, as already mentioned, a free end 4, which is configured for mating with a stump 5. In the case shown on the free end, the projecting part 8 which has been hexagon shaped by extrusion has been provided for. In any case, many other configurations are possible such as an octagon, in extruded curved surfaces or intruded surfaces, etc. What is important is that the projecting portion 8, mating with a corresponding section of the stump, provides a means of torsional coupling between the implant and the stump 5, so that during use, relative rotation between the stump 5 and the implant is prevented.

As can be seen from the figures, stump 5 is kept in position by a screw 6 that meshes with a matching thread made in a blind axial hole 7 of the implant. The stump can also be fixed to the system by means of cementation or a housing as well as by screwing.

As already mentioned, the transmucosal neck 3 and endosteal body 2 have been made as a single piece, but it hasn't been ruled out for them to be made as two or more pieces that can be mutually connected by means of clamping systems or by gluing, in the event they are made from different materials (such as, for example if the endosteal part is made of titanium and the transgingival part is ceramic).

Continuing with the description of Figure 1 , it is noted that the endosteal body 2 may comprise an intermediate portion 2A interposed between the screw 2B of the endosteal body 2 and the transmucosal neck 3. It is noted that in an axial section of the implant surface, taken at a transition area between the connecting portion 2A and the transmucosal neck 3, there is a connecting surface Al comprising an angular point.

From the drawings, it is possible to notice also that an external surface of the transmucosal neck 3 is shaped so that at least a first tangent Tl to the outer surface at a first point PI proximal to the endosteal body 2 and away from connecting surfaces, which together with an axis A of the dental implant forms a first angle al.

At least a second tangent T2 to the outer surface of the transmucosal neck 3, in a point P2 away from connecting surfaces and next to the free end 4, on the other hand forms with axis A of the system, a second angle a2.

According to this invention the first angle al is smaller than the second angle a2.

The first point PI belongs to a first part 3A of the transmucosal neck 3 proximal to the endosteal body 2, while the second point P2 belongs to a second part 3B of the transmucosal neck 3.

As can be seen in Figure 1, the surface of the transmucosal neck, in the axial section, as seen from the outside shows a convex shape.

In practice, the transmucosal neck 3 may have a total height between 1,0 mm and 3,5 mm, preferably from 1,5 mm to 2,8 mm, still more preferably from 1,8 mm and 2,2 mm calculated as starting from the free end 4. In fact, the "physiological" height of the gum is between these values.

The second point P2 can be found on the second part 3B in any position near the free end 4, provided it is located at a distance D2 greater than 0,4 mm from the free end 4.

In fact, the second tangent T2 must be drawn in a really descriptive point P2 of the inclination of the surface of the second part 3B with respect to the axis, and thus sufficiently distant from connections, special machining or other non-essential items.

The same reasoning applies to the first point PI which can then be in any position of the first part 3A next to the endosteal body 2, at any one point situated from a distance of at least 0,4 mm from the latter.

Also in this case, tangent Tl must be taken at a descriptive point PI of the first part 3 A.

Note that the height of the transmucosal neck and the distance of the PI, P2 from the free end or the endosteal implant body must be considered in terms of the axial direction, as shown in the figure.

In this case the height of the transmucosal neck is that between the plane passing through the free surface 4 of the system (excluding the protuberance or recess 8 if provided) and the plane passing through the surface that contains a greater base of the transmucosal neck 3. In essence, in the embodiment of Figure 1 (but also later on), the transmucosal neck 3 is divided into a first part 3A, next to the endosteal body 2 with a minor average surface inclination compared to that of a second part 3B next to the free end 4.

The first part 3A and the second part 3B are interconnected by a second connecting surface A2. In the described embodiment the second part 3B extends for about half the height of the transmucosal body. The same applies for the first part 3A.

It needs to be said that various configurations are also possible where the second part 3B extends up to a distance D3 from the free end 4 between 0,5 mm and 2,5 mm.

Returning to the description of Figure 1 , the surface of the first part 3 A in axial section, is a first straight line segment of constant Tl tangent, while the surface of the second part 3B, always in cross- section, and is still a second straight line segment of constant tangent T2.

As the tangents Tl and T2 are inclined in a different way with respect to the axis in correspondence with the connecting surface A2, an angular point may be found. Alternatively, it is possible to provide for a bevelled joint.

The embodiments displayed in the examples of Figures 3 to 7 show different variants of the implant. The above embodiments will make use of, to indicate functionally similar parts to those already described, the same reference numerals previously used, and such parts will not be further described.

In Figure 3 there is no real distinction between the first part 3A1 and the second part 3B1 of the transmucosal neck, but as we see from the drawing, the outer surface profile of the neck is a continuous curve, which has no relevant discontinuity being composed of a single arc of a circle. In this case, the centre of the hypothetical arc of a circle will be placed at the bottom of a hypothetical median line M that divides the transmucosal segment in two. In this way, tangents Tl and T2 will comply with the ratio already expressed above for the cases previously described.

In the embodiment of Figure 4, the curve is made by the interpolation of a plurality of circumferences of increasing diameter starting from the free end 4 of the implant. As before, Tl and T2 tangents will comply with the ratio already expressed above for the cases described above.

In fact, the first 3A4 and the second part 3B4 of the curve are formed by a plurality of circular arcs mutually interconnected to form a curve with a tangent devoid of discontinuities.

The same applies to the embodiment of Figure 7, that this time shows a surface 3A5, 3B5 the transmucosal neck 3 formed by arcs of a circle interconnected with straight line segments. Preferably, the circular arcs and the straight lines are alternated.

In an alternative embodiment, not shown but similar in concept to that shown in Figure 7, the transmucosal neck 3 can present, in axial section, a surface defined by a plurality of straight line segments all with increasing angles (with respect to axis A) closer to the free end 4.

Even in these cases, tangents Tl and T2 comply with the same ratios already described previously, as well as the position of points PI and P2 where said tangents are traced. Basically, also in these embodiments, the portion of the transmucosal neck next to the free end 4, presents an inclination with respect to the axis A which is greater than that of the part of the transmucosal neck next to the endosteal body 2.

Other embodiments, such as that of Figure 5, provide for the axial section of the first part surface 3B2 of the endosteal neck to be a straight line segment, while the second 3A2 is a curve.

Figure 6 instead shows the opposite configuration where the first part 3A3 defines a straight line segment, while the second part 3B3 defines a curve.

Basically the implant of this invention as described above, proposes a transmucosal neck 3 tapered to increasing inclinations in cervical-coronal direction.

This allows to obtain a wide free end 4 surface, to allow for the attachment of the stump, and a height H of the transmucosal neck sufficient to protrude from the gingiva. Furthermore, as is apparent from Figure 2, the greater inclination of the part next to the free end 4, minimises undercut problems encountered during the assembly of bridges, on stumps with non-parallel axes.

Referring to Figure 2, and for example the implant on the right, we note that if the angle of the surface of the transmucosal neck is measured with respect to the axis of the implant, it will be noted that in the vicinity of the endosteal part, surfaces of the transmucosal segment are less inclined with respect to those in the vicinity of the occlusal plane (the free end of the implant). This inclination difference with respect to the longitudinal axis of the implant can be made up by various straight or curved line segments or by a combination of these.

With reference to the embodiments described, it must be emphasized that the optimal angle between the surfaces of the conical transmucosal segment and axis A of the implant can vary from 1 degree to 15 degrees for the part next to the endosteal body 2 and by 3 degrees to 35 degrees in the vicinity of the prosthetic platform (or free end 4) of connection with the stump.

More preferably the angle between the surfaces of the conical transmucosal segment and axis A of the implant can vary from 2 degrees to 10 degrees for the part next to the endosteal body 2 and by 7 degrees to 15 degrees in the vicinity of the prosthetic platform (or free end 4) of connection with the stump.

More preferably the angle between the surfaces of the conical transmucosal segment and axis A of the implant can vary from 3 degrees to 7 degrees for the part next to the endosteal body 2 and by 10 degrees to 14 degrees in the vicinity of the prosthetic platform (or free end 4) of connection with the stump.

The variation of the degrees basically depends on the difference between the diameter of the large base of the transgingival conical segment, which in turn depends on the diameter of the bone screw, and the narrow base of the conical transgingival segment that depends on the diameter of the prosthetic platform. In the event the transgingival conical segment is constituted by convex curvilinear parts, with different inclinations and in combination with each other or in combination with rectilinear surface sections, calculating the inclination can be made by tracing a straight line that starts from the beginning and arrives at the end of the arc that makes up the profile of that particular section of the conical transgingival segment.

How the invention works is obvious to a skilled man, with particular reference to Figure 2 which shows two implants according to Figure 1 (but the same reasoning applies with regard to the embodiments of Figures 3, 5, 6 and 7).

When an implant is positioned with an axis not perfectly perpendicular to a hypothetical level of bone crest, the surfaces of the transmucosal segment are covered by the gum unevenly. In practice, surfaces of the transgingival implant segment will be better covered by the gum in correspondence to the part where the angle between the implant axis and the hypothetical plane of the bone crest is acute (right side of the right stump of Figure 2). Conversely, where the measure of the angle between the implant axis and the hypothetical plane of the bone crest is obtuse, surfaces of the transmucosal segment will be less covered by the gum (left side of the right stump in Figure 2).

Going back to Figure 2, here two implants with incidental axes A, and therefore not perfectly parallel can be seen. It must be said that configuration shown occurs frequently in practice, given that, although it would be ideal to be able to place implants with parallel axes, in the vast majority of cases this is not possible due to the difficult working conditions, visibility, the operating space, etc. available in the mouth.

It is noted that the particular configuration of the transmucosal neck 3 of the two systems allows the assembly of the bridge in the absence of undercuts that would occur with systems with a traditional transmucosal neck (see the straight lines L that show the absence of undercut during assembly of prostheses).

In addition, the above system allows to place crowns (of the bridge in this case) perfectly on the edge of the gingiva G allowing for an excellent covering of the stumps. This results in an excellent final aesthetic effect.

Various forms of making the invention were described, but others may be designed using the same innovative concept.