DENTAL IMPLANTS

Description

[0001] The invention relates to a dental implant intended for insertion into the jawbone of a patient, comprising a base body which is provided on its outer side with a circumferential external thread in an apically arranged screw area, according to the preamble of claim 1.

[0002] Oral implantology has evolved over the last four decades from a specialized to a routine treatment following tooth loss. The dental implants used in this process come in a variety of forms. They are usually screwed into the patient's jawbone in place of an extracted or missing tooth. After a healing period of three to four months, they support a prosthetic abutment or crown that serves as a tooth replacement. Such a dental implant is typically a suitably shaped metal body, resembling a pin, with a usually self-tapping screw thread at its apical end, which is used to insert the pin into the appropriately prepared implant bed in the jawbone.In cases of sufficient bone volume, there is a high probability of osseointegration of the implants, which can sustainably anchor a functionally loaded dental prosthesis. Currently, the most common indication and thus application (60-80%) of oral implants is the replacement of a single missing tooth with an implant to which a single crown is attached.

[0003] Primary and secondary stability are crucial for the integration of the implant into the jawbone and thus for the overall success of the treatment. When inserting the implant, a round bone cavity or hollow is typically created in the jawbone at the designated site, preferably by drilling (osteotemy). The implant screw is then screwed into this cavity. The thread flanks anchor themselves in the peri-implant bone purely mechanically, whereas a firm, rigid connection (also known as osseointegration) between the bone and the implant surface is not yet established immediately after implant insertion. This initial mechanical anchorage, also referred to as primary stability, therefore depends, among other things, on the design of the threads.

[0004] Following implant insertion, remodeling processes of the peri-implant bone begin. Depending on the trauma applied and the insertion procedure, osteotomy leads to the formation of a peri-implant bone layer that did not survive the trauma ("death zone"). This layer is initially resorbed by osteoclasts, and in cases of extensive death zones, this leads to a reduction in the mechanical anchorage of the implant (secondary stability) after two to four weeks of healing. This jeopardizes the clinical success and osseointegration of immediately loaded or prosthetically restored implants, particularly single-tooth implants and implants that are inserted into the alveoli immediately after tooth extraction or traumatic tooth loss and immediately restored with single crowns.

[0005] During the ongoing healing process, typically within 8 to 12 weeks after insertion, osseointegration takes place. This results in a strong, rigid bond between the implant surface and the bone tissue. This bond is ultimately essential for the load-bearing capacity of the implant, for example, against the applied chewing forces.

[0006] Another significant factor for the long-term success of dental implant treatment is the possibility of developing an infection or inflammation of the surrounding bone tissue, also known as peri-implantitis. The risk of implant failure after successful osseointegration correlates strongly with the condition of the peri-implant soft tissue, which acts as a barrier between the germ-laden oral cavity and the alveolar bone. The adhesion of the oral soft tissue to the implant surface and the resulting seal against the oral cavity can be negatively affected by a number of factors. Clinically, an infection initially manifests as inflammation of the soft tissue. This condition, known as mucositis, is similar to gingivitis in that both can heal completely.However, in cases of persistent or spreading mucositis, the inflammatory process extends to the peri-implant bone, resulting in irreversible bone loss. This stage of the disease is called peri-implantitis. Mucositis should therefore be considered a precursor to peri-implantitis.

[0007] Despite diverse treatment approaches, the progression of peri-implantitis can hardly be prevented because the implant surface, which is usually designed to promote osseointegration, has the undesirable side effect of promoting the formation and attachment of a biofilm and thus the colonization of germs.

[0008] Dental implants of the type mentioned above are known, for example, from WO 2010 / 003433 A1, US 5,209,659, EP 1 710 325 A1, EP 0 641 549 A2 or ZA 200606187 B. A dental implant according to the preamble of claim 1 is known from US 4,431,416.

[0009] The invention is based on the objective of providing a dental implant of the type mentioned above which, on the one hand, enables particularly high primary and secondary stability and thus particularly promotes the healing process, but on the other hand, facilitates the containment or treatment of any inflammation that may occur in the surrounding bone tissue in a particularly favorable way.

[0010] This problem is solved according to the invention with the features of claim 1.

[0011] The dental implant screw according to the invention thus essentially comprises two areas: firstly, the anchoring area provided at the apical end and equipped with an external thread, which is limited exclusively to a "lower" section of the total length of the implant; and secondly, the "upper" shaft area, which adjoins this anchoring area immediately in the longitudinal direction and is threadless, thus having a comparatively smooth macroscopic structure. The base body in the shaft area has a cross-section that tapers in the longitudinal direction of the base body, i.e., it is conical.

[0012] The invention is based on the consideration that, on the one hand, the primary and secondary stability of the inserted dental implant, which is essential for the success of the treatment, is significantly influenced by the thread provided in the lower end region of the base body and its anchorage in the bone tissue; in contrast, the contributions of threads located in the upper shaft region to stability are largely negligible. On the other hand, threads in the upper shaft region are rather detrimental, especially in measures against existing or incipient inflammation, as they promote the adhesion of biofilm and make therapeutic access to the interface between bone tissue and the implant surface more difficult.

[0013] Therefore, the main body of the implant should be consistently kept free of threads in its "upper", endosseous shaft area.

[0014] In particular, it is advantageously taken into account that, especially when inserting implants into hard bone, comparatively deep thread flanks (i.e., the formation of the external thread as a relatively "aggressive," self-tapping thread) are disadvantageous. These require a corresponding, usually complex osteotomy protocol—sometimes involving thread cutting in the hard bone—to allow the implant screw to be inserted without excessively high insertion torques (< 100–150 Ncm). Therefore, implant screws with deep thread flanks are primarily used clinically in soft bone—mainly in the maxilla. Another clinical application is implant insertion immediately after tooth loss, i.e., screwing the implant into the tooth socket.Due to the incongruity between the conical shape of the tooth socket and the round implant screw, usually only the first 4 to 5 mm of the implant screw can be screwed into the bone, with the remainder of the screw having no contact with the bony socket walls. Therefore, deep threads are incorporated, especially at the tip of the implant screw, to ensure high primary mechanical stability of the implants even immediately after tooth loss. This allows for immediate and ideal closure of the tooth socket with a crown anchored to the implant, and thus provides the patient with a functionally and aesthetically high-quality prosthetic restoration immediately after tooth loss.

[0015] Furthermore, it is advantageously taken into account that with complete osseointegration, i.e., after a healing period of typically about 8 to 12 weeks, a firm, rigid bond forms between the bone tissue and the implant surface. This firm bond between the peri-implant bone and the implant surface, particularly in the upper shaft region of the implant body, enables a mechanical anchorage quality of the implant that is independent of the thread design. In other words, implants with small thread flanks or no thread at all, after complete osseointegration, do not exhibit any limitations regarding their mechanical load-bearing capacity with prosthetic restoration concepts. This is also confirmed by the observed long-term clinical performance of short implant screws with conventional implant diameters.Despite a significantly reduced implant surface area, these implants also achieve the same mechanical load-bearing capacity as longer implants after complete osseointegration.

[0016] These findings suggest that the threaded area required for stability can be limited to the apical region of the implant base without significantly compromising the implant's load-bearing capacity. This can be used to consistently design the "upper" shaft region of the dental implant to facilitate any necessary treatment measures in the event of inflammation.

[0017] Inflammation of the peri-implant soft tissue (mucositis) can be triggered and / or maintained by various factors. The etiology of mucositis is therefore multifactorial. A single factor can be responsible for its pathogenesis. Furthermore, the severity and progression of mucositis are promoted by the interaction of multiple factors, not all of which have likely been identified to date. Due to the relatively high prevalence of mucositis (64.5%) and the resulting peri-implantitis (12.9%), prophylactic therapies and measures are gaining significant importance in order to prevent premature implant and / or bone loss.

[0018] Such prophylactic approaches aim to avoid or minimize irritation or inflammation of the peri-implant soft tissue. Therefore, it is desirable to identify the potential risk factors and indicators responsible for mucositis and peri-implantitis. In oral implantology, the following are among the risks for the development of mucositis: a material that is not optimally biocompatible, a rough surface, fluid contaminated with toxins or metal particles, and a biofilm that is difficult to remove. A traumatic or incorrectly performed step in the fabrication of implant-supported prostheses also increases the risk of mucositis.

[0019] A very common treatment approach for inflammation is smoothing the implant surface in the upper shaft area, which includes removing any existing threads (so-called implantoplasty). Disadvantages include contamination of the peri-implant soft and bone tissue with titanium shavings produced during grinding and a reduction in mechanical strength. Furthermore, explantation or removal of the implant is often the preferred method to prevent further bone loss, which would eventually lead to implant failure.

[0020] The indication for implant removal is either due to its technical and / or biological failure, or in the case of a patient's implant phobia, which is usually superimposed on psychosomatic factors. Technical failure often occurs as a late complication resulting from material fatigue. The implants fracture or show cracks at the connection between the implant and the prosthetic post (abutment). Both of these conditions prevent the implant from bearing any functional load. Biological implant failure, on the other hand, is often a consequence of progressive inflammation of the peri-implant soft tissue (mucositis / peri-implantitis), as described above. Furthermore, the exposure of the implant surface can sometimes lead to aesthetically unacceptable situations, which are addressed either with surgical interventions for tissue regeneration or with explantation.Furthermore, early explantation prevents progressive and irreversible peri-implant tissue loss. In rare cases, patients develop anxieties and phobias after implant placement. Despite successful osseointegration, they may desire a "metal-free" jawbone or attribute their health problems to the implants. Both of these reasons lead to the desire for premature implant removal, even if the implant has not experienced technical and / or biological failure.

[0021] If, for any of the aforementioned reasons, the removal of a fully or partially osseointegrated implant becomes necessary, this can be performed using various techniques. Clinical experience shows that the difficulty and associated bone loss increase with the osseointegrated implant length and diameter, as well as the length and / or prominence of the thread flanks. All of these parameters increase the contact area with the osseointegrated bone tissue and thus the torque required to unscrew the implant screw. Similarly, trephine burs destroy more peri-implant bone tissue with increasing implant length and diameter. Conversely, short and narrow implants, as well as implants without threads or with very short thread flanks, facilitate the removal of an implant screw. Minimal peri-implant bone loss can therefore be expected.

[0022] The aforementioned findings are taken into account in this design by ensuring that the implant screw is designed without threads in its "upper" or endosseous shaft area from the outset. Therefore, in the event of a therapeutic intervention for one of the aforementioned reasons, the removal of threads is unnecessary, and the risk of contamination or exposure of the surrounding tissue by any metal shavings or similar debris is avoided.

[0023] In other words, the invention utilizes the understanding that the essential contributions to the stability and mechanical strength of the implant are made by the apical end region of the screw thread, thus enabling and encouraging the upper, endosseous shaft region to be kept thread-free. This facilitates access to the implant surface during necessary therapeutic procedures, simplifies the removal of the inserted implant if required, and reduces the risk of contamination of the surrounding tissue by metal shavings. Accordingly, the end region supporting the screw thread, and thus the thread itself, should preferably be limited to a length of no more than 4 mm, preferably no more than 3 mm, when viewed longitudinally along the implant.

[0024] Advantageous embodiments of the invention are the subject of the dependent claims.

[0025] In a particularly preferred embodiment, the shaft area of ​​the base body is provided with an outer surface selected to suit the desired properties, preferably with a machined or polished outer surface.

[0026] From a macroscopic perspective, the base body is threadless and therefore smooth in the shaft area. From a microscopic perspective, the base body in the shaft area is advantageously designed with a surface structure particularly conducive to the desired osseointegration. For this purpose, the base body in the shaft area most preferably has an outer surface with a roughness value (Ra) of at least 1 µm. Preferably, the roughness value (Ra) should not exceed 3.5 µm. A roughness value (Ra) between 1.5 µm and 3.5 µm is particularly preferred for the outer surface. Alternatively or additionally, the base body in its shaft area also has a surface structure particularly favorable for osseointegration. For this purpose, the threadless portion of the endosseous implant body preferably has a surface with a stochastic or deterministic pattern.

[0027] In an additional or alternative advantageous embodiment, the base body is designed for even further improved osseointegration by having the threadless portion or shaft region of the endosseous implant body coated or physically, chemically, and / or optically treated, preferably biocompatible, surface. In a further advantageous embodiment, the surface of the shaft region can also have a combination or gradient of one or all of the surface modifications described above.

[0028] The base body of the dental implant is advantageously designed to provide both a screw area and a threadless shaft area. The screw area advantageously has a length of at most 40%, preferably at most 1 / 3, and preferably at most 1 / 4, of the total length of the base body. Correspondingly, the threadless shaft area advantageously has a length of at least 60%, preferably at least 2 / 3, and preferably at least 3 / 4, of the total length of the base body.

[0029] The combination of the spatially limited screw area with the threadless shaft area, as provided for in the invention, is particularly advantageous for implants with a comparatively large overall length. The base body therefore preferably has an overall length of at least 6 mm, and more preferably at least 8 mm.

[0030] The screw section advantageously has a length of at most 4 mm, preferably at most 3 mm, generally, but particularly preferably in combination with the aforementioned length values ​​for the base body. Accordingly, and in an alternative or additional advantageous embodiment considered to be independently inventive, the external thread has at most four threads, and particularly preferably, and also in an embodiment considered to be independently inventive with regard to the surprisingly achievable primary stability, at most three thread turns. In this context, "thread turn" of a screw thread is understood to mean the portion of the screw thread that is traversed from any point on the screw thread in a single complete revolution around the thread core.

[0031] In its most advanced form, this implant is particularly suitable for the immediate restoration of patients with single-tooth crowns, where load distribution across multiple implants connected by prosthetic structures (bridges, bars, etc.) is not possible. For this purpose, the thread in the screw area is advantageously designed as a so-called "aggressive" thread, which features comparatively deep thread flanks, especially at the implant tip (apex). This ensures good primary stability of the implant, even in soft bone.

[0032] In a further advantageous embodiment, the base body has a round or oval cross-section in the shaft area.

[0033] The dental implant can be designed as a one-piece implant, in which the prosthetic restoration for the patient is attached directly to the base body after its insertion into the jawbone. Alternatively, and preferably, the implant can also be designed for use in a two-piece implant system, in which an abutment is first placed onto the inserted base body, which in turn supports the actual prosthetic restoration for the patient. The base body is preferably designed at its free end of the shaft area to be suitable for connection with the abutment, i.e., adapted to the respective connection system.

[0034] Advantageously, the base body is formed from a suitably chosen, biocompatible material suitable for osseointegration, particularly preferably titanium.

[0035] The advantages achieved with the invention consist in particular in the fact that, through the intended combination of a screw area with an external thread, limited only to the apical end region of the base body, with the endosseous area, good primary and secondary stability during insertion and, after osseointegration, a load-bearing capacity of the implant that meets even high demands can be achieved, while, on the other hand, therapeutic access is particularly facilitated in case of need and especially in the event of inflammation.

[0036] This allows the dental implant to effectively meet the following five design criteria using particularly simple means: 1. Immediate loading of single-tooth implants: Immediately after the placement of single-tooth implants, a single-tooth crown can be attached in non-functional occlusion. After complete osseointegration of the implant, a functional occlusion is achieved. In particular, if the length of the screw area is preferably approximately 3 to 4 mm and the screw area has relatively deep thread flanks, a single-tooth crown can be attached in non-functional occlusion after the placement of single-tooth implants. No further threads on the implant are required. The primary stability achieved in this way is sufficient for the immediate loading of a single-tooth implant. 2.Minimally invasive therapy for mucositis or peri-implantitis: In the event of peri-implant tissue disease (mucositis / peri-implantitis), therapeutic implantoplasty (leveling and smoothing of the implant surface) is not required, as the portion of the endosseous implant body adjacent to the soft tissue is unthreaded. Even in cases of progressive peri-implantitis with peri-implant bone loss of several millimeters, implantoplasty is not necessary with this macro-design. 3. Minimally invasive implant removal: The removal of an osseointegrated implant should cause only minimal peri-implant bone loss, relatively independent of its length and diameter. The implant body according to the invention can be removed by unscrewing it from the bone socket, relatively independent of its length and diameter, because the majority of the implant body is unthreaded.4. Atraumatic Implant Insertion: The insertion of an implant should cause low friction and thus low heating of the cortical compacta of the peri-implant bone, relatively independent of its length, diameter, and material. Due to its short, threaded portion, the insertion of the implant body according to the invention generates only low friction and thus only low heating of the cortical compacta of the peri-implant bone. Atraumatic implant insertion is therefore relatively independent of the implant length, diameter, and material. 5. Osteotomy Protocol Independent of Mechanical Bone Properties: The surgical steps and instruments used to create the bone cavity for a screw implant should be independent of the biomechanical properties of the bone (hard vs. soft).The invention allows for the use of threads in the implant, which, according to the invention, are located exclusively in the apical part of the implant. These threads typically engage in the cancellous bone marrow and are therefore usually located in soft bone. An osteotomy protocol can thus be reduced to implant insertion in the soft bone, as the remaining portion of the implant, surrounded by hard cortical bone, has no thread and therefore no high friction in the hard bone. The surgical steps and instruments used to create the bone cavity for a screw implant are thus relatively independent of the biomechanical properties of the bone (hard vs. soft bone quality).

[0037] An embodiment of the invention is explained in more detail with reference to a drawing. The drawing shows: FIG. 1 a dental implant intended for insertion into the jawbone of a patient, and FIG. 2 an alternative embodiment of the dental implant according to FIG. 1 .

[0038] Identical parts are labelled with the same reference symbols in both figures.

[0039] The dental implant 1 acc. FIG. 1 The dental implant 1 is designed for insertion into a patient's jawbone and, in a standard configuration, comprises a base body 2 which is provided with a circumferential external thread 6 on its outer surface in an apically arranged screw area 4. The dental implant 1 is designed, on the one hand, to ensure particularly high primary and secondary stability, thereby promoting the healing process, while on the other hand, it is also intended to facilitate the containment or treatment of any inflammation that may occur in the surrounding bone tissue once the dental implant 1 has been inserted.

[0040] The design of the dental implant 1 utilizes the understanding that the apical end region 8 of the external thread 6 provides the essential contribution to the stability and mechanical load-bearing capacity of the implant. Accordingly, the upper, endosseous shaft region 10 can be kept unthreaded without any significant impairment of the primary or secondary stability of the inserted dental implant 1 or its load-bearing capacity after osseointegration. The base body 2 is therefore designed without threads in the proximal shaft region 10, which is provided in addition to the screw region 4 and is directly adjacent to it.This facilitates access to the implant surface when necessary for therapeutic measures, makes it easier to remove the inserted implant if required, and reduces the risk of stress on the surrounding tissue from metal shavings in the case of implantoplasty (leveling and smoothing of the implant surface).

[0041] The outer surface 12 of the shaft region 10 is specifically designed to have properties that promote healing and / or osseointegration. It could be machined or polished for this purpose. In the exemplary embodiment, the outer surface 12 in the shaft region 10, while macroscopically smooth and free of threads, also exhibits a surface structure particularly favorable for osseointegration under a microscopic view. For this purpose, the base body 2 in the shaft region 10 has an outer surface 12 with a roughness value Ra of approximately 2 µm. Alternatively or additionally, the base body 2 in its shaft region 10 can also have a surface that is particularly favorable for osseointegration with regard to its structure, coating, and / or pretreatment.

[0042] The base body 2 is designed to provide both the screw area 4 and the unthreaded shaft area 10. In the exemplary embodiment, the base body 2 has a total length L of approximately 11 mm. In contrast, the screw area 4 is limited to a length LS of approximately 3.2 mm, whereas the unthreaded shaft area 10 has a length of approximately 7.8 mm. In the exemplary embodiment, the screw area 4 thus comprises 29% of the total length L of the base body 2, and the shaft area comprises 71% of the total length L of the base body 2. The target limits of a maximum of 40% for the screw area 4 and / or a minimum of 60% for the unthreaded shaft area 10 are therefore clearly met in the exemplary embodiment. Furthermore, the external thread 6 in the exemplary embodiment, as shown in the illustrations in Figs. 1 und 2 It is clearly visible that there are only 3 complete threads.

[0043] The external thread 6 in the screw area 4 is designed as a so-called "aggressive" thread, which has comparatively deep thread flanks, especially in the apical end area 8.

[0044] In the exemplary embodiment, the base body 2 is designed with a cross-section that tapers towards the apical end region 8 in the shaft area 10 as well as in the screw area 4, i.e., in particular, is conical.

[0045] In the exemplary embodiment according to FIG. 1 The base body 2 has a round cross-section in the shaft area 10. In the alternative embodiment according to... FIG. 2 In contrast, the dental implant 1' has an oval cross-section in the shaft area 10 of the base body 2.

[0046] In both variants shown, the dental implant 1, 1' can be designed as a one-piece implant, in which the prosthetic restoration for the patient is attached directly to the base body 2 after its insertion into the jawbone. However, the variants shown are those in which the respective base body 2 is intended for use in a two- or multi-piece implant system. In this system, an abutment (not shown in detail) is first placed onto the inserted base body 2, which in turn supports the actual prosthetic restoration for the patient. The base body 2 is designed at its free end 14 of the shaft section 10 to be suitable for connection with the abutment, i.e., adapted to the respective connection system.

[0047] In the examples shown, the base body 2 is formed from a suitably chosen, biocompatible material suitable for osseointegration, in the exemplary embodiment from titanium. Reference symbol list

[0048] 1 Dental implant 2 Base body 4 Screw area 6 External thread 8 Apical end area 10 Shaft area 12 Outer surface 14 Free end L Total length L S Length of the shaft area

Claims

1. A dental implant (1, 1') comprising a main body (2) that is provided on its outside with a circumferential external thread (6) in an apically arranged screw region (4) and is designed to be thread-free in a proximal shaft region (10) which is provided in addition to the screw region (4), adjoins the screw region, and is likewise provided for osseointegration, wherein the screw region (4) has a length (LS) of at most 4 mm, preferably at most 3 mm, characterised in that the main body (2), in the thread-free shaft region (10), has a cross-section that tapers as viewed in the longitudinal direction of the main body (2).

2. The dental implant (1, 1') according to claim 1, which is designed in its screw region (4) with a self-tapping thread.

3. The dental implant (1, 1') according to claim 1 or 2, the shaft region (10) of which is designed with a polished outer surface (12).

4. The dental implant (1, 1') according to any one of claims 1 to 3, the main body (2) of which has an outer surface (12) in the shaft region (10) with a roughness with a roughness value Ra of at least 1 µm, preferably from 1.5 µm to 3.5 µm.

5. The dental implant (1, 1') according to any one of claims 1 to 4, the main body (2) of which is provided in the shaft region (10) with a biocompatible surface structure or coating.

6. The dental implant (1, 1') according to any one of claims 1 to 5, the screw region (4) of which has a length (LS) of at most ⅓, preferably at most ¼, of the total length (L) of the main body (2).

7. The dental implant (1, 1') according to any one of claims 1 to 6, the threadless shaft region (10) of which has a length of at least 2 / 3, preferably at least ¾, of the total length (L) of the main body (2).

8. The dental implant (1, 1'), in particular according to any one of claims 1 to 7, the external thread (6) of which has at most four, preferably at most three, thread turns.

9. The dental implant (1, 1') according to any one of claims 1 to 8, the main body (2) of which has a round cross-section in the shaft region (10).

10. The dental implant (1, 1') according to any one of claims 1 to 8, the main body (2) of which has an oval cross-section in the shaft region (10).