EP1699378A1

EP1699378A1 - Dental implant

Info

Publication number: EP1699378A1
Application number: EP04806462A
Authority: EP
Inventors: Ioannis Corcolis
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-12-30
Filing date: 2004-12-29
Publication date: 2006-09-13
Also published as: ITMI20032618A1; WO2005065571A1

Abstract

A dental implant is described that has two lateral recesses (8) on the lateral surface (1). They extend longitudinally for at least 1/3 of the length, starting from the coronal end (2), and care opposite each other. They are intended to be situated in an interproximal position when the implant is inserted into the bone and allow the preservation and/or regeneration of the interproximal bone peak, even in the presence of neighbouring teeth roots or dental implants, with better aesthetical and functional results than in known implants

Description

DENTAL IMPLANT

FIELD OF INVENTION

The present invention relates to a device for dental implants, suited for being inserted and integrated into the maxillary or mandibular bone to support an artificial tooth. PRIOR ART

Dental implants are commonly used in dental prosthetics for replacing the roots of missing or lost teeth. They are devices with an opportune shape, usually an approximately cylindrical, conical or frustoconical shape, with several possible variants, which can be inserted into special holes made in the maxillary or mandibular bone. They are intended to support a prosthetic stump that is fixed to the implant (two-piece implant), or can be integral with the implant that continues into the stump (one-piece implant); the prosthetic stump, protruding from the gum into the oral cavity, provides a support for a dental crown that can be cemented or fixed by other means to the stump or directly to the implant. Implants can be non submerged or submerged, depending on whether they protrude or not from the gum immediately after their insertion. They can be two-phase implants, if they are connected to the respective stumps or other type of prosthetic support after a period of primary healing or single phase if they are inserted and connected to the respective stumps in the same phase.

Implants can be made of different materials, chosen according to biocompatibility and the ability of integration with the bone, to provide the prosthesis with adequate stability and duration. They are generally made of titanium, titanium alloys, ceramics or, more rarely, surgical steel. The implants can be provided with a thread, normally of the self-tapping type, or pre-threaded for screwing into a hole made in the bone, or else implants are intended to be simply inserted with a certain pressure into a hole of shape and size that permits adequate fixing (press-fit technology): A commonly used type of implant has a shape that can be approximately cylindrical or frustoconical, with a sectional form, perpendicular to the axis of the implant (section related to the first coronal third of the length of the implant) that is circular. It has a coronal end, intended to face outwards from the, hole after insertion and an apical one, opposite to the coronal one and intended to be inserted deep into the bone. The coronal end, also known as the implant head, has a coronal surface provided with means for connecting a prosthetic stump, for implants known as two-piece implants, or continues into the stump itself, if it is a one-piece implant. The lateral surface of the implant can be suitably treated to favour osteointegration, via roughening using mechanical, chemical or other means, also in combination with each other. Grooves or protuberances can be present to better favour the primary or delayed stability of the implant in the bone. A portion, or neck, of said surface close to the coronal end, generally a band of appropriate width, is normally smooth, not as rough as the rest of the said surface or, in any case, rendered suitable for soft tissue contact and growth. Said portion is, generally intended to protrude from the bone and be surrounded by gum, which covers it. In general, the implant ends with a flat surface at the coronal end, in any case with the border that delimits the implant's lateral surface from coronal surface lying on a plane (for example, it would be a flat circular line if the implant has the form of a rotational solid, and the plane on which it lies could be perpendicular or otherwise with respect to the, implant's axis of symmetry). The same occurs for the line that delimits the lateral surface portion intended to touch the bone from the neck, which is smooth or, anyway, has been rendered suitable for contact with soft tissue. This solution has the drawback of not favouring the preservation of the bone's original morphology after the implant is installed: the tendency of the gum around a healthy tooth is actually to follow a scalloped profile, which resembles the edge of a saddle, where the gingival margin around the tooth, looking in the direction from the tooth towards the bone, is concave at the front and rear parts of the tooth (buccai and lingual surfaces respectively) extending towards the root of the, tooth (apical direction), and convex at the sides of the tooth (interproximal surfaces), extending towards the crown of the tooth (coronal direction). The bone margin has a similar tendency at a depth of approximately 2.5-3 mm (known as "biologic width" or "depth"). The bone peak between the interproximal surfaces of two adjacent teeth is known as the interproximal bone peak(or bone papilla) and gives physical support and blood supply to the portion of gum, the so-called "interdental papilla", which covers it The presence or absence of papillae is of fundamental importance for aesthetics, especially in the mouth's frontal areas. For both natural teeth and teeth supported by implants, the presence and height of the bone peak between them is decisive for presence, height, health and appearance of the gingival papilla. Even today, in the field of implantoprosthetic dentistry , it is very difficult, if not impossible to preserve or recreate the interproximal bone peak with sufficient height and volume to guarantee the presence, health and longevity of an interdental papilla. As already set forth in patent application WO 01/06944, implants with a flat coronal top cause bone resorption or hinder the regeneration of the interproximal bone peak, which impairs the functional and aesthetical '. results of the implant. This is even more true when dealing with front teeth where the "saddle" profile is very noticeable and where patients' expectations and clinicians' attention for an optimal aesthetical result are high. The proposed solution in the document referred to envisages that the border delimiting the coronal surface of the implant and the line that separates the lateral surface adapted to make contact with the bone from 'the smooth neck have a saddle-like profile corresponding to the profile^' found around a natural tooth. Nevertheless, this solution is not altogether satisfactory with regards to preservation of the interdental papilla, especially when the implant is located very close to the root of a tooth, a common situation in cases of operating to replace front teeth, but which can also arise in other positions. In spite of the availability of many types of dental implants and sophisticated and expensive regenerative techniques, even today, conservation of a papilla is still difficult and its satisfactory recreation between two contiguous dental implants is impossible. The blame for this lies in the larger amount of bone that is lost due to the summing of the vertical and horizontal components of biologic width around the two implants. In addition, since implants are usually mass-produced, a large variety of different profiles would be necessary for adapting to the various individual situations, as extreme; precision would be required in the shape and dimensions of the implant's neck. In addition, the large accentuation of the saddle profile needed in certain positions requires considerable precision in positioning the implant. Furthermore, in the case where for any reason the interproximal bone peak doe's not perfectly re-form, the large curvature of the profile would cause problems adapting the implant to the site for which it is destined, to the extent of compromising the success of the operation or, in any event, a satisfactory aesthetical result. The need is therefore felt for a dental implant that allows the preservation of the physiological contour of bone margin, even in the most difficult situations, thereby precluding the problems discussed above and associated with known solutions. SUMMARY The above-stated problems are now resolved thanks to a dental implant suitable for being inserted into a hole made in a maxillary or mandibular bone along its own longitudinal axis, the implant having a coronal end, an apical end, a lateral surface that extends between said apical and coronal end, a coronal surface separated from said lateral surface by a edge, characterized in that said lateral surface has two flat portions or recesses extending along the direction of said axis and having a maximum width, along at least one plane perpendicular to said axis, of at least 1/5, and preferably at least 1/3, of the maximum width of the implant section along said plane.

The above-stated characteristic of the lateral surfaces can vary from a simple flattening of the lateral surface's convexity up to the creation of a proper concavity or groove.

Said axis can be an axis of symmetry of the implant. The implant can basically have the shape of a rotational solid; in this case, the said maximum width coincides with the substantially circular diameter of the perpendicular section. Preferably, said flat portions or recesses are opposite each other.

Said flat portions or recesses can all be the same or different from each other., Preferably, the recesses extend for at least a fifth, more preferably for at least a fourth, and most preferably for at least a third of the maximum height, along said axis, of said lateral surface, and can even extend for more than half of said height.

In accordance with an embodiment of the invention, for two-piece implants, said recesses extend starting from said edge, in correspondence with which they preferably have their maximum width. In accordance with another preferred embodiment, the recesses extend starting from a point apically offset with respect to said edge (by 0.5 to 3 mm for example), which is not affected. Said recesses can be a flat or concave portion of surface on said lateral surface, which, for the most part, can usually be a convex surface. For one-piece implants in accordance with the present invention, the flat portions or recesses can have a maximum width and depth corresponding to the level of the bone peak (pre-existing or to where it must be re-established) when the implant is correctly positioned. The recesses concern trie portions of the implant intended to be positioned interproximally, that is facing adjacent teeth, implants or alveoli, when the implant is inserted in the bone. The object of the invention is detailed in the content of the appended claims. LIST OF FIGURES

The present invention will now be illustrated via a detailed description pf preferred, but not exclusive, embodiments, provided purely by way of example, with the aid of the enclosed figures, wherein: Figure 1 schematically represents a side view of a dental implant in accordance with the present invention,

Figure 2a schematically represents a plan view of the dental implant of Figure 1 ,

Figure 2b schematically represents a plan view of the dental implant of Figure 1 in accordance with a further aspect of the present invention, Figure 3 schematically represents a cross-section along the AA plane of Figure 1,

Figure 4 schematically represents a side view of an implant in accordance with a different further embodiment of the invention, Figure 5 schematically represents a portion of dental arch with two correctly placed implants in accordance with the present invention, Figure 6 schematically represents a frontal view of the implant of Figures 1 and 2b, Figure 7 schematically represents the portion of dental arch of Figure 5 ^' indicating the implant sections close to the root of a tooth, 5 Figure 7a represents a similar portion with implants of known type, Figure 8 schematically represents a frontal view of an implant in accordance with a different further embodiment of the invention, Figures 9 and 10 schematically represent a frontal and side view of an implant in accordance with a different further embodiment of the

10. invention, Figure 11 schematically represents a side view of a one-piece implant in accordance with a different further embodiment of the invention, Figure 12 schematically represents a portion of dental arch with two correctly placed implants in accordance with an aspect of the present

15 invention, Figure 13 schematically represents a perspective view of an implant in accordance with a different further embodiment of the invention, Figures 14 and 15 schematically represent a side and a frontal view respectively of the implant of Figure 13, 0 Figures 16a and 16b schematically represent a view of the coronal end of two variants of the implant of Figure 13, Figures 17a and 17b schematically represent a perspective view of a stump suitable for the implant of Figures 6a and 16b, Figures 18 and 19 show a side and a frontal view respectively of the 5 stump of Figure 17a or 17b, Figure 20 schematically represents a top view of the stump of Figures 18 and .19, , Figure 21 schematically represents a perspective view of an implant in accordance with a different further embodiment of the invention, Figures 22 and 23 schematically represent a side and a frontal view respectively of the implant of Figure 21 , Figures 24a and 24b schematically represent a view from the coronal end of two variants of the implant of Figure 21 , Figures 25a and 25b schematically represent a perspective view of a stump suitable for the implant of Figures 24a and 24b, Figures 26 and 27 show a side and a frontal view respectively of the stump of Figures 24a or 24b, Figure 28 schematically represents a top view of the stump of Figures 26 and 27, Figure 29 schematically represents a perspective view of an implant in accordance with a different further embodiment of the invention, Figures 30 and 31 schematically represent a side and a frontal view respectively of the implant of Figure 29, Figures 32a and 32b schematically represent a view from the coronal end of two variants of the implant of Figure 29, Figure 33 schematically represents a perspective view of a stump suitable for the implant of Figure 32a, Figures 34 and 35 schematically represent a side and a frontal view respectively of the stump of Figure 33, Figure 36 schematically represents a top view of the stump of Figures 34 and 35, Figure 37 schematically represents a perspective view of an implant in accordance with a different further embodiment of the invention, Figures 38 and 39 schematically represent a side and a frontal view respectively of the implant of Figure 37, Figure 40 schematically represents a view from the coronal end of the implant of Figure 37,

Figure 41 schematically represents a perspective view of a stump suitable for the implant of Figure 40,

Figures 42 and 43 schematically represent a side and a frontal view respectively of the stump of Figure 41 ,

Figure 44 schematically represents a top view of the stump of Figures 42 and 43, Figure 45 schematically represents a perspective view of an implant in accordance with a different further embodiment of the invention,

Figures 46 and 47 schematically represent a side and a frontal view respectively of the implant of Figure 45,

Figures 48a and 48b schematically represent a view from the coronal end of two variants of the implant of Figure 45,

Figures 49a and 49b schematically represent a perspective view of a stump suitable for the implant of Figures 48a and 48b,

Figures 50 and 51 schematically represent a side and a frontal view respectively of the stump of Figures 49a and 49b, Figure 52 schematically represents a top view of the stump of Figures 50 and 51, Figure 53 schematically represents a perspective view of an implant in accordance with a different further embodiment of the invention, Figures 54 and 55 schematically represent a side and a frontal view respectively of the implant of Figure 53,

Figures 56a and 56b schematically represent^" a view from the poronal end of two variants of the implant of Figure 53, Figures 57a and 57b schematically represent a perspective view of a stump suitable for the implant of Figures 56a and 56b,

Figures 58 and 59 schematically represent a side and a frontal view respectively of the stump of Figures 49a and 49b, Figure 60 schematically represents a top view of the stump of Figures 58 and 59. DETAILED DESCRIPTION OF AN EMBODIMENT

A side view of an implant in accordance with the present invention is shown in Figure 1. In the figure, a longitudinal axis 4 that could be an axis of symmetry of the implant is indicated; the direction of the axis 4 identifies what is essentially the direction of advancement of the implant when it is inserted into the hole made in the maxillary or mandibular bone of a patient. The lateral surface 1 extends between the apical end 3 and the coronal one 2 of the implant. The edge 5 coronally delimits the lateral surface 1 and separates it from the coronal surface 6. For two-piece implants, the coronal surface 6 can be equipped with means for fixing a prosthetic stump. These means can be of the known type... For example, J they could be a cavity 7 of suitable section that forms the female element of a coupling . in which the male element is part of the prosthetic stump. The cavity extends for a certain depth and has an appropriate section, corresponding to that of the stump's male element. An example is shown in the figures of a cavity having a section similar to the shape of the coronal surface 6, because the edge 5 is not circular due to the presence of the recesses 8 (in this way the section is able to provide a stable implant-stump coupling), but it could have any suitable shape, preferably polygonal, hexagonal for instance, so as to prevent rotation of the stump once fixed; the section can preferably have rounded comers (if polygonal for instance). A threaded blind hole 9 can be present at the bottom of the cavity 7 to allow fixing the stump via a screw passing through a specially provided hole in the stump; a different type of fixing system could also be provided, for example, cementing of the stump, with a conical or conometric coupling. In accordance with another embodiment of the invention, it is possible that instead of a cavity there is an opportunely shaped protuberance for coupling with a cavity of corresponding shape

, in the stump (see Figures 29 and 33, reference numbers 32 and 33). Also in this case fixing of the stump can be via a screw, cementing or any other known system that is considered suitable. In accordance with a further embodiment of the invention, the prosthetic stump can be an integral part of the implant and its surface an integral part of the coronal surface upon which the crown could be cemented, or fixed via a screw or in any other known manner. As usual, all or part of the lateral surface 1 preferably has chemical and physical surface characteristics that render it suitable for osteointegration. The entire implant could be made of a material suitable for osteointegration, or it could be coated with such a material in correspondence to all or part of the lateral surface 1. Commonly employed materials are titanium or its alloys, ceramics and surgical steel. The surface suited for the osteointegration can be treated to give it the correct porosity or roughness by, for example, sandblasting, acid etching plasma treatment or any other type of roughening through the addition or removal of material. Alternatively or in addition, elements can be used on said surface that carry growth factors or proteins to favour cellular adhesion or accelerate bone growth ove it.

As is usual, it is preferable that at least a portion of the lateral surface is smooth or not as rough as the rest of the surface. This portion 10, or neck, close to the coronal end of the implant, is normally left smooth or rendered less rough via a special treatment, so that it is suited for contact with soft tissue and favours growth and adhesion. In fact, this portion is generally intended to protrude from the bone and instead be surrounded by the gum, which covers it. It is separated from the rest of the lateral surface 1 by the line 12, which is generally, but not necessarily, at a constant distance from the edge 5, from 0.5 to 2 mm for example or, in accordance with another aspect, from 1.5 to 2 mm. In accordance with a different aspect of the present invention, the line 12 can also have a smaller or null vertical distance from the edge 5. As described above, the implant in accordance with the present invention has two recesses 8 that affect the lateral surface. They extend for at least 1/5 of the height of the implant, and preferably at least 1/3. They can have various shapes, for instance the margins 11 can be parallel for a section or convergent, or even widen for a section and then narrow down again. In this case, in accordance with a preferred aspect, the maximum width of the recess is in correspondence with or close to the line, 12 that separates the smooth neck 10 from the rest of the lateral surface. The depth is. also variable, as is the shape. The depth could, for instance, reach its maximum in correspondence to the maximum width of the. recess. For example, the bottom could be flat, as in Figure 2b (except for a portion, at the concave end 12, to avoid sharp internal margins) or concave, as in Figure 2a. According to a possible embodiment of the invention, the depth could be constant for the entire length or variable, decreasing towards the apical end for example.

If the impiant has an axis of symmetry, the recesses can be at least partially opposite each other with respect to the axis. They can extend starting from the edge 5, and with which their maximum width corresponds, or start from a position more towards the apical end. In general, they have a width of at least 1/5 of the maximum width of the cross-section of the implant in correspondence to the edge 5, or to the line 12. Although it is preferred that the recesses do not involve more than 2/3 of the height of surface 1, they can also extend for the entire height. Their maximum depth (with respect to. the profile of an implant without recesses) can be at least 1/16, for example, or preferably at least 1/8 of the maximum size of the cross-section of the implant at the same height. Any suitable value can be chosen for the maximum depth, as long as it does not compromise the stability of the implant-stump connection. In the case of threaded implants to be screwed in, in accordance with an embodiment of the invention, the maximum depth does not exceed the value of 1.5 mm, while this value can be exceeded in the case of press-fit implants. It is preferable that the surface affected by the recesses also has the same surface characteristics as surface 1 , namely suitable for osteointegration except for the part of recess that regards the smooth neck, if present, which can have the same characteristics suited to the adhesion of soft tissue, or could have characteristics suited to osteointegration up to the edge 5. * The implant can have various shapes and sections; Preferably, it is substantially a rotational solid, or at least the lateral surface is (except for the presence of the recesses, other grooves that may be present and any thread). Preferably, the implant has a substantially cylindrical, conical or frustoconical, or even a stepped shape. The lateral surface can have other grooves and indentations, such as to confer better primary stability (namely of the implant just inserted in the bone), and/or delayed stability (namely after a period of osteointegration), according to the experience of a person skilled in the art (for example, the depicted implant has apical grooves 13, of any shape and with any extension considered appropriate, up to the apical end 3 for instance, which, especially in the case of a press-fit implant confers greater primary and delayed stability in all situations). The implant can be of the press-fit type, which is devoid of an external thread, suitable for being introduced into a hole in the bone. In this case, the hole can be produced with a drill and then shaped via an opportunely shaped osteotome. In this case, the osteotome can give the hole a shape corresponding to the implant, also taking the longitudinal grooves into account if possible (in the case of longitudinal grooves that regard the lateral surface up to the apical end or in conical or stepped implants), in which the width of the transversal sections (that is those perpendicular to the longitudinal axis) closest to the apical end with respect to the grooves do not go beyond or not completely beyond the sections including the grooves. In press-fit technology, the implant can also have shapes different from a rotational solid. It can also have a cylindrical, conical, or frustoconical shape for one part and a shape different from a rotational solid for the other. For example, approximately half the height starting from the apical end can be of a cylindrical, conical or frustoconical shape, while the other half, near to the coronal end gradually assumes a not necessarily symmetrical shape, similar to that of the root of a natural tooth for example, preferably a single-root tooth. , The recesses can also be the same or different from each other.

The implant can be of the screw type and have a thread, generally of the self-tapping type, for insertion into the bone with a screwing movement, in this case into a hole with the shape of a rotational solid obtained via opportune drilling. The surface 1 , substantially having the shape of a rotational surface, in this case has a thread, which involves at least part of its height or all of its height (and may or may not be interrupted by the presence of grooves or recesses, depending on their depth and shape) and allows advancement of the implant along the direction of the axis 4 of symmetry. The thread can be of any known type. After the implant is inserted, the two recesses 8 are interproximally positioned, facing towards the adjacent teeth or implants, in correspondence to where the interproximal bone peak is situated in normal conditions. The presence of the recesses, in at least a third of the coronal part (that is for a third of the height of the lateral surface of the implant towards the coronal end) favours the preservation and regeneration of the interproximal bone portion, leaving more space available for its growth, even in the case of teeth or implants very close together. In this case, the presence of the recesses advantageously increases the distance between the surfaces of the implants and that of adjacent implants or tooth roots (compare Figures 7 and 7a), reducing the possibility of bone resorption or bone loss between them, without however excessively reducing the dimensions (especially the diameter), and therefore the implant's resistance and stability. This holds true particularly in the presence of adjacent implants that are also equipped with flat portions or recesses _. in the interproximal position in accordance with the present invention, which maximizes the conservation effect of an interproximal bone peak profile similar to the natural one and equivalent in terms of aesthetics and functionality. The preservation of a larger portion of bone is also possible even if the coronal surface 6 is flat and the edge 5 consequently lies on a flat surface, without the above-discussed problems arising with regards to implants in which the profile of the edge between the coronal surface and the lateral one is scalloped (the coronal surface is shaped like a saddle, for example, or in some other manner), in order to imitate the profile of a healthy bone peak. The coronal surface 6 can be flat, as illustrated in Figure 1. Nevertheless, it is possible to combine a curved profile of the edge 5 (and possibly of the entire coronal surface 6) with the presence of recesses. In this way, the effects of the curved profile can be maximized and the possibilities of bone loss (or resorption) can be reduced in the interproximal positions, with loss of the physical and nutritive support of the interdental papillae a d the consequent impossibility to preserve and/or regenerate it. Otherwise, it is also possible to achieve satisfactory results with a profile that is less curved than that necessary with implants . , - ' r of the known art and which, amongst other things, facilitates the standardization of measurements, and thus the industrial production of implants. For example, the profile of the coronal surface, of the edge separating it from the lateral surface and the smooth neck, can be substantially obtained in accordance with the teachings of WO 01/06944, obviously with the modifications required by the teachings of the present application. In accordance with another embodiment of the invention, the

-profiles can also take into account the different heights that the bone and the gum normally exhibit around a tooth on the lingual and buccai sides, as in general it is shifted more in the coronal direction on the lingual side and in the apical direction on the buccai side. For example, in the implant in Figure 4 one of the recesses 8 can be observed, intended to be interproximally positioned as stated above, and therefore in correspondence to a convexity (if seen from the coronal side) of the edge 5. The edge 5 has mutually opposed concavities 14 and 15: the concavity 14 is intended to face the lingual side, and is less accentuated, in compliance with that explained above, than the concavity 15 intended for the buccai side. The coronal surface can also be saddle-shaped, for instance, or have a suitable shape for adapting itself to the profile of the edge 5. As already described above and in document WO 01/06944, adequate means can be provided for the connection of the prosthetic stump in two-piece implants; alternatively, it can be an. integral part of the implant, if it is in one piece.

In Figure 5, an implant 16 in accordance with the present invention is shown inserted in a dental arch between a similar implant and a natural tooth 19. It is shown complete with a prosthetic stump 17 and crown 18. The gingival margin around the teeth is represented by the line 21 and the underlying bone profile by the line 20., It should be noted how the interproximally positioned recesses 8 contribute to increasing the space between implant and implant (as visible in Figure 7 where the distance between the two implants 16 in accordance with the invention is evidently greater than with traditional types of implant of the same diameter) or between implant and the root of the adjacent tooth (indicated in Figure 7 with reference number 24), facilitating conservation of the bone peak 22 and of the inter-implaήt papilla 23 in consequence. In accordance with an embodiment of the invention, as already stated above, the recesses do not involve 1he edge of separation between the lateral surface and the coronal surface. This constitutes a particularly preferred aspect. An implant is shown in Figure 8 with a flat coronal surface 6 and in Figures 9 and 10 with a curved coronal surface in which the recesses 8 start from a position that is apically offset with respect to said edge 5 (by 1 to 3 mm, for example). In accordance with a particular embodiment of the invention, they can have their maximum width, for example, in correspondence to the line 12 that separates the smooth portion from that suited to the osteointegration of the implant's lateral surface. The recesses can also start from other positions apically offset with respect to the edge 5; for example, they could also effectively start in correspondence to the line 12 of separation between the smooth- surfaced portion and the portion suited to the osteointegration of the lateral surface, and have maximum width in a more apical position.

In Figure 11, a side view is shown of a one-piece implant having recesses 8 that start from a position in correspondence with or near to the line 12 of separation between the smooth and rough parts of the implant's lateral surface. The stump 30 is shown, obtained integrally with the implant and with a shape that is suitable to receive the crown of an artificial tooth or to be individually prepared (filed) after its insertion in the oral cavity. The part of the lateral surface adapted for contact with gum tissue is delimited apically by the line 12 and coronally by the individual preparation of the stump. Other combinations of the above-described characteristics can be made according to necessity. . In the description, where possible, recesses are also to be intended as flat portions, as described above. Figure 12 shows two implants in accordance with an embodiment of the invention in which the recesses start from a position apically offset with respect to the edge that separates the lateral surface from the coronal one, correctly positioned in a portion of dental arch, similar to that shown in Figure 5, regarding implants in accordance with another embodiment of the invention.

Figures 13 to 20 refer to a two-piece implant and a prosthetic stump (the different possible shapes of the male element 31 may be noted) suitable for being fixed to it according to a particular embodiment of the invention, in which the recesses 8 touch the line 12 of separation between the rough lateral surface and the smooth or less rough portion.

Figures 21 to 28 refer to a two-piece implant of the so-called internal connection type arid a prosthetic stump suitable for being fixed to it, accprding to a particular embodiment of the invention, in which the recesses 8 also involve the edge 5. Figures 29 to 36 refer to a two-piece implant of the so-called external connection type and a prosthetic stump suitable for being fixed to it; according to a particular embodiment, of the invention, in which the coronal surface 6 is curved and the edge 5 has a scalloped profile. Figures 37 to 40 refer to a two-piece implant and a prosthetic stump suitable for being fixed to it, according to a particular embodiment of the invention, in which the coronal surface is curved, with a different type of connection to the prosthetic stump. Figures 45 to 60 refer to a two-piece implant, considering other examples of implants in accordance with the invention and relative stumps with a curved coronal surface and different configurations for the recesses. In two-piece implants, if the recesses or flat portions involve the separation edge between the lateral surface and the coronal surface, the stump could have a corresponding shape, as can be seen in Figures 25a to 26 and 49a to 50, where the stump has recesses 50 in correspondence with the profile adapted to match with the edge 5 of the implant. The recesses are in correspondence to the implant's recesses. The prosthetic stump, in the case of both one and two-piece implants, and the implant can be constructed with known technologies. The invention also relates to prosthetic stumps as described above. The stump can be of any material considered suitable, also in view of aesthetical considerations; for example, titanium alloys, zirconium, ceramics and plastics. The stump couid, for example, be of the prefabricated type and personalized via grinding, or be constructed using CAD/CAM technologies. If. considered appropriate, the margins of the recesses can be , opportunely rounded off. Other possible variants can be carried out in the light of the teachings above without departing from the spirit of the invention.

Claims

CLAIMS 1. A dental implant suitable for being inserted in a hole made in a maxillary or mandibular bone along a longitudinal axis (4) of the implant, the implant having a coronal end (2), an apical end (3), a lateral surface (1) extending between said apical and coronal ends, a coronal surface (6) separated by a edge (5) from said lateral surface, characterized in that said lateral surface has two flat portions or recesses (8) extending in the direction of said axis and having a maximum width, along at least one plane perpendicular to said axis, of at least 1/5 of the maximum width of the implant section along said plane. A

2. An implant according to claim 1 wherein said flat portions or recesses have a maximum width, along at least one plane perpendicular to said axis, of at least 1/3 of the maximum width of the implant section along said plane.

3. An implant according to any of the previous claims wherein said flat portions or recesses are mutually positioned so that when the implant is inserted in the bone, they will find themselves in the two interproximal positions.

4. An implant according to any of the previous claims having an axis of symmetry (4) and wherein said flat portions or recesses are symmetrically positioned with respect to said axis of symmetry.

5. An implant according to any of the previous claims wherein the flat portions or recesses extend for at least one fifth of the maximum height, along said longitudinal axis, of said lateral surface.

6. An implant according to claim 5 wherein the flat portions or recesses extend for at least one third of the maximum height, along said longitudinal axis, of said lateral surface.

7. Ah implant according to any of the previous claims wherein said edge lies on a flat surface.

8. An implant according to any of claims 1 to 6 wherein said edge has two convexities facing towards the coronal end. in correspondence to said flat portions or recesses and two concavities facing towards the coronal end, intended to find themselves in lingual and buccai positions (14, 15) situated between said convexities when the implant is inserted in the bone.

9. An implant according to claim 8 wherein the concavity (.14) provided for the lingual position is less pronounced than that (15) provided for the buccai position. ^{' •} A ^{' ■ ' ' ' '}

10. An implant according to any of the previous claims wherein said coronal surface has means (7 and 9) for fixing a prosthetic stump.

11. A one-piece implant, according to any of claims i to 9 including a prosthetic stump integrated in said coronal surface.

12. An implant according to any of the previous claims wherein a portion named neck (10) of said lateral surface close to the edge, separated by a : line (12) from the rest of the surface, is smooth and/or suitable to favour the adhesion of soft tissue, while the remainder of said lateral surface is at least partially treated to favour osteointegration.

13. An implant according to any of the previous claims wherein the maximum depth of the flat portions or recesses (with respect to the profile of an implant without flat portions or recesses) is at least 1/16 of the maximum dimension of the cross-section of the implant at the corresponding height.

14. An implant according to claim 13 wherein said maximum depth is at least 1/8 of the maximum dimension of the cross-section of the implant at the corresponding height

15. An implant according to any of the previous claims suitable for insertion into the bone using the press-fit technique.

16. An implant according to any of claims 1 to 14 wherein said lateral surface has a thread suitable for allowing the implant to be screwed into a-hole made in the bone.

17. An implant according to claim 16 wherein the maximum depth of said flat portions or recesses does not exceed 1.5 mm.

18. An implant according to any of the previous claims wherein the maximum width of the flat portions or recesses is in correspondence to said edge.

19. An implant according to any of claims 1 to 17 wherein the flat portions or recesses do not involve said edge.

20. An implant according to claim 19 wherein the projection of said edge on a plane perpendicular to said longitudinal axis is substantially circular.

21. Ah implant according to claim 12 wherein the maximum width of the flat portions or recesses is in correspondence to the line of separation between said neck and the rest of the lateral surface.

22. A prosthetic stump suitable for being fixed to a two-piece implant according to any of the previous claims, with two lateral recesses or flat portions (50) in correspondence to th recesses of the implant.