Technical Field

[0001] The present invention relates to a subgingival implant adapt to retain implants in a bone graft.

[0002] Lifting the Schneider membrane is a step in the surgical procedure to increase the thickness of the jaw bone and facilitate the insertion of dental implants.

[0003] The reconstruction of the bone of the posterior maxilla requires the integrity of the maxillary sinus membrane, known as Schneider membrane, which forms a barrier between the sinus cavity and the surrounding bone. The posterior alveolar bone can be substantially thinner than the other portions of the crestal bone due to bone resorption in the edentulous, thus not providing a thickness sufficient to ensure a permanent dental implant.

Background Art

[0004] EP 17154694 of the same Applicant describes a tool for detaching the Schneider membrane from the sinus floor comprising a flexible tube, a syringe for a saline solution connected to the flexible tube that has a head unit at its opposite end. The head unit has a flexible tube terminal tract being provided with an end element projecting radially and a concentric abutment member intended to abut the maxillary bone on the side opposite to the Schneider membrane. In this way, the radial holes are kept patent when in working position the head unit is inserted into a hole drilled in the maxillary bone in a surgical operation for lifting the sinus floor.

[0005] In EP 17154694 the saline solution is delivered by the syringe in order to obtain a de tachment of the Schneider membrane.

[0006] The step following the detachment of the Schneider membrane from the floor of the maxillary sinus is to fill with bone graft or artificial bone the space that formed as a result of the aforementioned detachment.

[0007] To ensure the maintenance of this space where the implant is inserted, a mechanical device is used such as a temporary abutment to be applied on a implant completely inserted into the bone graft through the gingival mucosa and the pre-existing bone. See for example the sinus lift temporary abutments on page 1 of the BICON catalog,

Boston (MA - U.S.A.) to be applied to the implants shown on the same page. Each temporary abutment acts as a spacer, being positioned between the gingival mucosa and the proximal end of an implant. Its purpose is to hold the implant in place for as long as necessary for the consolidation of the bone graft. However, this single abutment has some drawbacks: being held only by the gingival mucosa that is previously cut and then closed on it, the abutment has no stable position. Furthermore, in the case of two or more consecutive implants, their relative position is not carefully defined by the separate temporary abutments.

[0008] EP 2489328 discloses a modular framework superstructure for dental implants

comprising a modular series of stumps and rods with horizontal axis, each of them being composed of a tubular bar provided at one end with a ear with hole, whereas at the other end of said bar a clip is applied, being provided with circular hole identical to the first hole, having suitable dimensions to receive one of said stumps. This framework allows adjacent stumps for assuming and maintaining a perfectly vertical position that favors a balanced, homogeneous transmission of the stress to implants. The superstructure according to the cited patent is designed to be permanently installed in a patient’s mouth for counter-biasing stresses transmitted by crowns to the stumps. Summary of the Invention

[0009] An object of the invention is to provide a positioning element which can have a stable position under the gingival mucosa.

[0010] Another object is to provide a positioning element that can be placed simultaneously on several implants to define a more precise mutual position with respect to the prior art temporary abutment, creating a greater extension of the bone graft between the pre existing bone and the Schneider membrane.

[0011] The objects are achieved by the present invention which provides a subgingival po sitioning element, adapt to retain in a bone graft between the maxillary sinus floor and the Schneider membrane, each implant having a cavity designed to permanently receive subsequently an abutment bearing a crown, the positioning subgingival element comprising an elongated plate having a proximal side intended to face the gingival mucosa and a distal side intended to face the Schneider membrane, the elongated plate being enlarged in at least two cups that are separated from each other by the distance between the axis of an implant and the axis of a consecutive implant, each cup protruding from the distal side of the elongated plate and centrally extending in a protuberance designed to be positioned in said respective implant cavity.

[0012] Advantageously, the elongated plate is provided, in an intermediate position between one abutment and the other, of a through hole for a screw for fixing the elongated plate to the pre-existing bone layer.

Brief Description of Drawings

[0013] Further features and advantages of the present invention will appear mostly clear from the indicative and therefore non-limiting description of embodiments of a sub gingival positioning element, as illustrated in the enclosed drawings in which: - Figure 1 is a plan view from the proximal side of a first embodiment of a sub gingival positioning element according to the present invention;

- Figure 2 is a side view of the subgingival positioning element in Figure 1;

- Figure 3 schematically represents the side view of the subgingival positioning element in Figure 2 on implants that, shown in a side view and partially cross- sectioned, are inserted in a maxillary bone;

- Figure 4 is a side view of a second embodiment of a subgingival positioning element according to the present invention;

- Figure 5 is a plan view from the proximal side of a third embodiment of a sub gingival positioning element according to the present invention;

- Figure 6 is a side view of the subgingival positioning element in Figure 5; and

- Figure 7 is a plan view from the proximal side of a fourth embodiment of a subgingival positioning element according to the present invention.

[0014] Description of Embodiments of the Invention

[0015] Reference is initially made to Figures 1 and 2 that are plan view from the proximal side and, respectively, from a side view, a first embodiment of subgingival positioning element 1 according to the present invention.

[0016] The subgingival positioning element 1 comprises an elongated plate 2. The elongated plate 2 has a proximal side 3 that is smooth, intended to face the gingival mucosa mg, when put in place, and a distal side 4, intended to face the Schneider membrane ms.

This can be seen in Figure 3 which is a side view of the subgingival positioning element in Figure 1 in situ on implants I, I.

[0017] The elongated plate 2 is enlarged, at its ends, in two cups 5, 5 separated one from the other by the distance between the y-axis of an implant I and the y-axis of a consecutive implant I. Each cup 5, 5 protrudes from the distal side 4 of the elongated plate 2, and has centrally a protuberance 6 intended to be positioned on a respective implant I. The protuberance 6 is tapered with a frustoconical shape. It is easily understood that the shape of the protuberance 6 depends on the shape of the cavity 31 of the implant I on which the protuberance 6 is intended to be supported temporarily, i.e. for as long as necessary for the consolidation of the bone graft io. Then, even if not shown in the drawing, the shape of the protuberance can be also prismatic, or cylindrical, or different on the basis of the kind of implant I being installed.

[0018] The protuberance 6 is shown in a fragmentary cross-sectioned view in Figure 3, only partially inserted in the cavity 31, but this graphic representation is not to be intended as binding in embodying the invention.

[0019] The elongated plate 2 has a rectangular section with chamfered distal edges for fitting to the endosseous insertion without creating stress points.

[0020] As regards sizes of the positioning element, by way of an example, excluding the cups, the elongated plate 2 has a length of 10 mm, a width of 5 mm and a thickness of 2 mm. Each cup 5, 5, in its distal side 4, has a radius of 6.5 mm. The thickness of each cup 5, 5 is preferably 1.5 times the thickness of the plate, i.e. 3 mm, while the pro tuberance has a thickness twice that of the plate, i.e. 4 mm. It should be clear that these measurements are only indicative since the positioning element must be sized so that the cups 5, 5 are in situ with their protuberances 6 at the implants I, I, as will be seen below with reference to Figure 3.

[0021] As regards the use of the positioning element according to the present invention, after having surgically proceeded to lift the Schneider membrane ms from the floor of the maxillary sinus ps , between the one and the other, a traditionally known bone graft io is inserted. The implants I, I were applied in the bone graft through the gingival mucosa ms and the maxillary bone om. By opening the gingival mucosa mg with crestal access, the subgingival positioning element 1 is applied. By using the per foration in the maxillary bone om used for the application of the implants I, I, the cups 5, 5 of the subgingival positioning element 1 are located coaxially with the implants I,

I, in the bone graft io previously placed between the floor of the maxillary sinus ps and the Schneider membrane ms. Next, a closure of the gingival mucosa mg keeps the sub gingival positioning element on implants I, I for the entire time necessary for the con solidation of the bone graft io.

[0022] Although in the previous description conventionally bone graft or artificial bone was mentioned as a substance filling the space created by lifting the Schneider membrane, it should be specified that, with the device according to the present invention, one could do without bone grafting because the implants that hold up the Schneider membrane create a curtain effect on a blood clot that is interposed between Schneider membrane and maxillary bone. In this way, the blood clot, not being crushed by the weight of the membrane that remains raised, stabilizes and transforms itself into bone. Thus, the insertion of those materials today generically called bone grafting can be avoided, but whose function is only that of spacer, with consequent economic savings and surgical facilitation.

[0023] Advantageously, the elongated plate 2 is provided with a through hole 7 in an in termediate position between one cup 5 and the other. The through hole 7 serves to insert a screw 8 for fixing the elongated plate 2 to the maxillary bone om. In this way, the subgingival positioning element 1 is further secured over the implants I, I.

[0024] Refer now to Figure 4, in which a second embodiment of the invention is shown.

Figure 4 uses the same reference numbers for parts that are the same as or similar to those of the preceding figures. The second embodiment of the invention differs from the first in that the subgingival positioning element 10 comprises an elongated plate 20 enlarged in three cups 5 separated from each other by the distance between the axis y of an implant and the axis y of a consecutive implant.

[0025] In conclusion, the positioning element 10 is combined with three consecutive

implants. For the rest, features and functionality are identical to those of the first em bodiment.

[0026] Reference is now made to Figures 5 and 6, which are a plan view from the proximal side and a side view of a third form of subgingival positioning element according to the present invention.

[0027] They show a subgingival positioning element 11, in which one of the two cups, the one indicated with 50, is connected in an adjustable position to the elongated plate 21.

[0028] In particular, the elongated plate 21 has a through slot 23 extending in a direction or thogonal to the implant axis y as shown in Figure 3. The cup 50 has a central threaded hole and is joined to the elongated plate 21 by means of a cup-carrying screw 25 inserted in the through slot 23 on the proximal side 30 of the elongated plate 21 and retained therein. In fact, the head of the screw 25 is held on the edge 24 of the through slot 23.

[0029] For the third embodiment of a subgingival positioning element 11, also, each pro tuberance 6, 60 has a shape corresponding to that of the cavity of an implant so as to be temporarily retained therein. As an example, it is shown as frustoconical. The taper angle is the one established for the implants. Of course, if the chosen implant has a cavity of a different shape also the protuberance is shaped accordingly.

[0030] The purpose of making at least one cup, the one indicated with 50, adjustable in position on the elongated plate 21, is to correct any construction errors, in order to allow in any case a perfect positioning of the cup protuberances on the implants previously installed in the dental arch.

[0031] Refer now to Figure 7, which is a plan view from the proximal side of a fourth form of subgingival positioning member 12 according to the present invention. Therein, equal or similar numbers are used to indicate parts equal or similar to those of the third embodiment.

[0032] The main difference of the fourth embodiment is that the elongated plate 22 is

lightened with through holes 26, visible in the proximal side 32, in particular in its part included between the two cups 51, 52. The through holes 26, which are indicated squared by as an example only, are used to outline a non-compact bar in its constituent material, which could also be realized as a grid or a net. The openings in the elongated plate 22, whatever they are, have the function of favoring the blood circulation between the mucosa and the bone, although probably not necessary given the reduced dimensions of the elongated plate 22.