DENTAL IMPLANT COMPONENT

Abstract: Dental implant component (10) on which a dental prosthesis (30; 40) or core part thereof is intended to be fabricated having a proximal end (2), a distal end (6) and a channel (7) which extends from a proximal opening (9) in the proximal end to the distal end, characterised in that the dental implant component is provided with a roof wall structure (5) at the distal end of which a predetermined area (18) is adapted to be removed to provide a distal opening to the channel of predetermined dimension for enabling a post (50) to be positioned in the channel during fabrication of the dental prosthesis or core part thereof with a close fit being formed between the post and the distal opening.

Description: DENTAL IMPLANT COMPONENT Field of the Invention The present invention relates to a dental implant component on which a dental prosthesis or core part thereof is intended to be fabricated. Background of the Invention Such dental implant components are commonly referred to as "cylinders" in the art but this term is not used herein when specifically referring to the present invention as it implies a circular cross-section of constant diameter for the component which is not an essential feature for the purposes of the present invention. A dental prosthesis is one of the components which make up a dental implant which is a structure which is anchored to the bone (maxilla or mandible) of a jaw of a patient to replace one or more lost natural teeth. A dental implant comprises a dental prosthesis support structure which is anchored to the jaw bone of a totally or partially edentulous patient to support the dental prosthesis. The dental prosthesis support structure is typically formed by (i) one or more anchoring members (fixtures) implanted in the bone tissue of the maxilla or mandible, the number of fixtures used depending on whether the dental implant is to be for a single-tooth replacement, in which case a single fixture will be used, or for replacement of a number of lost teeth, in which case one or, more usually, a plurality of fixtures will be used, and (ii) a transmucosal member (abutment) for each fixture, each abutment being connected to the coronal end of a fixture to bridge the soft tissue layer (gingiva) of the jaw overlying the fixture site. A structure which presents one or more artificial replacement teeth - the dental prosthesis - is then connected to the coronal end(s) of the abutment(s), e.g. a crown for a single-tooth replacement or a bridge for replacement of a number of lost natural teeth. To ensure that the dental prosthesis fits in with the prevailing conditions in the oral cavity, for instance natural teeth still left in the maxilla and mandible, the dental prosthesis is fabricated on a full-scale model of the jaw prepared in a manner known per se. Usually incorporated in the model are one or more analogue components, the number corresponding to the number of fixtures implanted in the jaw bone. The or each analogue component has an end which is an analogue of the coronal end presented by the or each coronal member of the dental prosthesis support structure, e.g. the abutment(s). The or each analogue component is incorporated into the model so that the analogue end accurately reproduces the position and orientation that the coronal end of the associated coronal member of the dental prosthesis support structure has or will have in the jaw. A cylinder having a proximal or apical end which complements the coronal end of the coronal member(s) of the dental prosthesis support structure is then seated on the analogue end of each analogue component. A dental prosthesis which fits in with the prevailing conditions in the oral cavity is then fabricated on the cylinder or cylinders whereupon the dental prosthesis is transferred to the dental prosthesis support structure for anchorage to the jaw bone. The manner in which the dental prosthesis is fabricated on the cylinder(s) depends on whether it is for a single-tooth replacement or for replacing a number of teeth and also on whether the prosthesis is to be a permanent prosthesis or a temporary prosthesis for use in an interim period while a permanent prosthesis is fabricated. Permanent dental prostheses are typically formed by applying a wax pattern on the cylinder(s) and forming a cast structure on the cylinder(s) having the same profile as the wax pattern by the lost-wax casting process in which the cylinder- wax pattern assembly is placed in a mould and surrounded by investment material and a precious or semi-precious metal such as gold is injected into the mould to replace the wax pattern. In this regard, the cylinder(s) can be totally or partially formed of a burnout material, e.g. a plastic such a polystyrene, in which case the burnout material is also replaced by the precious or semi-precious metal. The use of the investment material, however, ensures that the surface features at the apical or proximal end(s) of the cylinder(s), for example polygonal faces, which enable the cylinder(s) to index with the coronal end(s) of the coronal member (s) of the dental prosthesis support structure are retained in the cast structure if these features are presented by burnout material. A permanent single-tooth dental prosthesis thus typically comprises an inner cast framework which includes, or is based on, a cylinder which is connectable to the coronal end of the coronal member of the dental prosthesis support structure, e.g. an abutment, and a porcelain layer fired onto the inner framework. The wax pattern may or may not be shaped to give a tooth-like inner framework onto which the porcelain layer can be fired. Where a number of natural teeth are to be permanently replaced the dental prosthesis will typically comprise an inner casted framework which includes, or is based on, a number of cylinders connectable to the coronal members of the dental prosthesis support structure, e.g. abutments, and a range of artificial teeth (denture) mounted on the inner casted framework. In this instance, the wax pattern will typically splint the cylinders on the analogues in the model to form a cast framework which can bridge across the spaced-apart coronal members of the dental prosthesis support structure and the denture will be mounted on the casting either before or after the casting is mounted on the dental prosthesis support structure. Alternately, the dental prosthesis may be formed by applying an isolated wax pattern to each cylinder to form individual castings which are then mounted to the coronal members of the dental prosthesis support structure with the denture then being mounted onto the castings. For an overview on the formation of permanent dental prostheses see inter alia 'Dental Implants: A Guide for the General Practitioner', Michael Norton, Quintessence Publishing, 1995, Chapters 4 and 5. The use of temporary dental prostheses is well-known and the circumstances in which a temporary dental prosthesis is needed is documented in US patent No. 5,259,759 (Jorneus et al/Nobelpharma AB). In the case of a temporary single- tooth dental prosthesis, the usual procedure is to form an acrylic resin artificial tooth on the cylinder by applying the acrylic resin to the outer surface of the cylinder when mounted on the analogue end of the analogue in the model, shaping the acrylic resin and then curing the acrylic resin. The convention in the art is for a cylinder to be in the form of a sleeve, that is to say, having a proximal or apical end for engagement with the analogue end of an analogue and therefore the coronal end of the associated coronal member of the dental prosthesis support structure, a distal end spaced from the proximal end and an open-ended channel which extends from a proximal opening in the proximal end to a distal opening in the distal end. Such cylinders are disclosed in US patent No. 5,259,759 supra, US patent No. 5,527,183 (O'Brien /Collaborative Enterprises, Inc.), US patent No. 5,533,898 (Mena), US patent No. 5,439,380 (Marlin), US patent No. 5,180,303 (Hornberg et al/Regents of the University of California) and US patent No. 5,234,339 (Grigereit/Kulzer, Inc.). In some of these US patents the cylinders are fixed directly to a fixture, that is to say, the need for an abutment in the dental prosthesis support structure is obviated. By using a sleeve cylinder in the formation of a dental prosthesis for the replacement of a plurality of lost teeth, e.g. a bridge, an inner cast framework having open-ended channels therethrough can be formed. In the case of a double construction bridge (see Chapter 5, 'Dental Implants: A Guide for the General Practitioner' supra) these channels act as access passages for screws to pass through and secure the inner cast framework to the dental prosthesis support structure. The denture is then cemented to the inner cast framework screw- retained to the dental prosthesis support structure. In a regular bridge, the access passages can communicate with access passages formed in the denture when the denture is cemented to the inner cast framework. The cemented assembly can then be screw-retained to the dental prosthesis support structure via the communicating access passages. In the case of single-tooth dental prosthesis, e.g. a crown, the use of a sleeve cylinder allows the dental prosthesis to be cemented to the coronal member of the dental prosthesis support structure extra-orally with the cemented assembly then being added to the apical structure of the dental prosthesis support structure already anchored to the maxilla or mandible, as will be discussed more fully hereinafter. In the case of permanent dental prostheses the formation of the access passages is as a result of a post being inserted into each cylinder when mounted on an analogue in the model to an operational position in which the trailing end of the post projects from the distal opening in the cylinder to a height greater than that to which the wax pattern is to be built and in which the post forms a close fit with the distal opening in the cylinder. The wax pattern is then built-up around the post whereby removal of the post after the pattern has been completed leaves a passage in the wax pattern which communicates with the channel in the cylinder. This channel in the wax pattern is reproduced in the casting. The close fit of the post with the distal opening of the cylinder acts to prevent wax leaking into the cylinder prior to casting which might otherwise make it difficult for the prosthesis to be properly secured on the dental prosthesis support structure. Usually the insertion end of the post is screw-threaded and in the operational position is engaged in an internally-threaded section of a socket in the analogue end of the analogue structure which may or may not be a replica of an internally-threaded section of a socket which opens in the coronal end(s) of the dental prosthesis support structure. A post is also used in similar fashion when a sleeve cylinder is used for forming a temporary dental prosthesis. For example, to form a temporary single-tooth dental prosthesis the proximal end of the cylinder is engaged to the analogue end of the analogue structure in the model of the partially edentulous patient and the post is inserted into the cylinder to an operational position in which the trailing end of the post projects from the distal opening in the cylinder to a height greater than that to which the acrylic tooth is to be built and in which the post forms a close fit with the distal opening in the cylinder. Acrylic resin is then applied to the outer surface of the cylinder, shaped into the form of a natural tooth which fits in with the surrounding dentition in the model and then cured. The close fit of the post with the distal opening of the cylinder acts to prevent the acrylic resin leaking into the cylinder prior to curing which might otherwise make it difficult for the prosthesis to be properly secured on the dental prosthesis support structure. The post further acts to form a channel in the cured acrylic tooth which communicates with the channel in the cylinder or in another words to form an open-ended channel through the temporary single-tooth dental prosthesis formed through which, for example, a screw can pass to screw-retain the prosthesis to the dental prosthesis support structure. To illustrate the fact that the use of a sleeve cylinder enables extra-oral connection of a single-tooth dental prosthesis to the coronal member of a dental prosthesis support structure supra, one can consider the case of securing a temporary single- tooth dental prosthesis to a dental prosthesis support structure in which the coronal member is a conventional abutment comprising (i) a sleeve part which sits on the coronal end of a fixture in which there is an internally -threaded socket, and (ii) a screw part which is inserted through the lumen in the sleeve and screwed into the internally-threaded socket in the coronal end of the fixture to secure the abutment sleeve to the fixture through a head of the screw bearing down on a shoulder in the lumen of the abutment sleeve. The open-ended channel formed in the temporary single-tooth dental prosthesis by the post enables the sleeve cylinder sub-structure of the temporary single-tooth dental prosthesis to be cemented to the abutment sleeve extra-orally and the assembly so formed to be placed on the coronal end of the fixture with the abutment screw then being inserted through the prosthesis-abutment sleeve assembly for engagement in the internally-threaded socket in the fixture. The channel in the prosthesis would then be filled in. In the above illustration of extra-oral connection it is possible that the abutment sleeve could be releasably positioned in the model in place of an analogue thereof whereby the cylinder is placed on the abutment sleeve during fabrication of the prosthesis. More generally, there are other conceivable instances in which the coronal members of a dental prosthesis support structure are incorporated in a model for use in combination with a cylinder prior to being anchored to the jaw bone. Another type of prior art cylinder corresponds to the sleeve cylinder except that a roof wall structure is provided across the distal opening. With this type of cylinder a dental prosthesis not having an access passage therein is formed necessitating intra-oral connection of the prosthesis to the support structure. For example, when forming a temporary single-tooth dental prosthesis a post cannot be used when the acrylic resin in applied with the consequence that no access channel is formed in the prosthesis. Thus, when the temporary prosthesis formed with this type of cylinder is to be cemented to the two-piece abutment described hereinabove the cementing step will have to take place intra-orally as the abutment sleeve will need to be screw-retained to the fixture by the abutment screw before the prosthesis can be cemented to the abutment sleeve. The problem with the hitherto proposed cylinders is that they restrict the practitioner to the manner in which the dental prosthesis can be engaged to the dental prosthesis support structure. The present invention proposes to improve this position. Summary of the Invention According to a first aspect of the present invention there is provided a dental implant component on which a dental prosthesis or core part thereof is intended to be fabricated having a proximal end, a distal end and a channel which extends from a proximal opening in the proximal end to the distal end, characterised in that the dental implant component is provided with a roof wall structure at the distal end of which a predetermined area is adapted to be removed to provide a distal opening to the channel of predetermined dimension for enabling a post to be positioned in the channel during fabrication of the dental prosthesis or core part thereof with a close fit being formed between the post and the distal opening. The advantage of the dental implant component of the invention is that it gives the practitioner the ability to decide whether or not to form the distal opening and hence the option of the way in which the dental prosthesis is to be formed and attached to a dental prosthesis support structure for anchorage to the jaw bone. The dental implant component may be formed from a metal, for example titanium or gold, or a plastics material, for instance one which can burn-out during investment or lost-wax casting. It follows from the last point that a dental implant component in accordance with the invention need not necessarily form a part of the dental prosthesis or core part fabricated thereon since burn-out material will be replaced by a casting if the dental prosthesis or core part is formed by lost-wax casting. In an embodiment of the invention such as hereinafter to be described the dental implant component is a one-piece component. In an embodiment of the invention such as hereinafter to be described the predetermined area of the roof wall structure is a predetermined portion of the roof wall structure. The predetermined area may be adapted to be removed by making the predetermined area of reduced wall thickness. This would facilitate grinding away of the predetermined area and may be achieved by making the predetermined area a recessed area of the roof wall structure. The recessed area may be formed by the provision of a recess in a proximal surface of the roof wall structure. The boundary of the recess on the proximal surface may be highlighted on a distal surface of the roof wall structure by a boundary marking, for instance a grooved track, thereby ensuring accurate removal of the predetermined area of the roof wall structure. Of course, the use of a marking on the distal surface of the roof wall structure to delimit the boundary of the predetermined area is not limited to the case where a recess is provided on the proximal surface of the roof wall structure. In an embodiment of the invention such as hereinafter to be described the predetermined area of the roof wall structure consists of a first sub-area which is adapted to be removed to provide a pilot distal opening to the channel which is of a dimension less than the predetermined dimension and a second sub-area juxtaposed with the first sub-area which is adapted to be removed by grinding away of a peripheral edge of the pilot distal opening whereby the pilot distal opening is enlarged to the distal opening of the predetermined dimension. In an embodiment of the invention such as hereinafter to be described the predetermined area of the roof wall structure consists of a transverse base and a distally-extending projection on the base into which the channel extends to define a cavity in the projection of dimension less than the predetermined dimension whereby removal of the projection or a distal portion thereof to expose the cavity provides the pilot distal opening to the channel. In an embodiment of the invention the predetermined area of the roof wall structure is presented by a distally-extending projection into which the channel extends to define a cavity in the projection of the predetermined dimension whereby removal of the projection or a distal portion thereof to expose the cavity provides the distal opening to the channel of the predetermined dimension. It may be useful for an outer surface of the dental implant component to be provided with a surface structure for inhibiting proximal-distal movement of the dental prosthesis or core part fabricated thereon. With this in mind, the projection may present a transversely-extending flange at its distal end. In an embodiment of the invention the predetermined area of the roof wall structure is a releasably securable portion of the component. According to a second aspect of the present invention there is provided a dental implant system comprising a dental implant component according to the first aspect of the invention and a post adapted for insertion in the channel of the dental implant component through the distal opening to an operational position in which the post forms a close fit with the distal opening. According to a third aspect of the invention there is provided a method of forming a dental prosthesis for mounting on a coronal end of a dental prosthesis support structure comprising the steps of providing a dental implant component having a proximal end for engagement with the coronal end of the dental prosthesis support structure, a distal end capped by a roof wall structure and a first channel which extends from a proximal opening in the proximal end to the roof wall structure; providing a post; providing a distal opening to the first channel through the roof wall structure of a size sufficient for the post to be inserted into the first channel; positioning the post in the first channel such that the post projects from the distal opening; and forming the dental prosthesis by either fabricating an artificial tooth-presenting structure on the dental implant component with the projecting post being used such that an open-ended second channel is formed in the artificial tooth-presenting structure which communicates with the first channel or fabricating a core part of the dental prosthesis on the dental implant component with the projecting post being used such that an open-ended second channel is formed in the core part which communicates with the first channel and providing an artificial tooth-presenting structure on the core part. Preferably, in the method according to the invention a distal opening of dimension which produces a close fit with the post when inserted into the channel is provided in which case the dental implant component and post used in the method may be a dental implant system according to the second aspect of the invention. The method of the invention may be used for single-tooth replacement in which case the artificial tooth-presenting structure presents a single artificial tooth. In this instance, the artificial tooth-presenting structure of the dental implant component may be an acrylic resin artificial tooth cured to the dental implant component or a layer of porcelain applied to a core part of a dental prosthesis fabricated on the dental implant component. The method of the invention may also be used for replacing a plurality of lost natural teeth in which case the artificial tooth-presenting structure presents a corresponding number of artificial teeth. In this instance, more than one dental implant component may need to be used. Ordinarily, core parts would then be formed on each dental implant component which are connected together in series so as to form a bridge structure on which the artificial tooth-presenting structure is able to be provided. The core parts could, on the other hand, be formed independent from one another. The artificial tooth-presenting structure may be a denture securable to the core parts either intra- or extra-orally. In an embodiment of the method according to the invention an open-ended third channel is provided in the artificial tooth-presenting structure which communicates with the second channel in the core part. This has particular application in the formation of a regular bridge for the reasons outlined hereinabove. By way of example, embodiments of the invention will now be described with reference to the accompanying Figures of drawings. Brief Description of the Drawings Figure 1 is a side view of a dental implant component in accordance with the invention; Figure 2 is a cross-sectional side view of the dental implant component; Figure 3 is a perspective view from underneath of the dental implant component; Figure 4 is an underneath view of the dental implant component; Figure 5 is a perspective view from above of the dental implant component; Figure 6 is a plan view of the dental implant component; Figure 7 is a schematic cross-sectional side view of a first temporary single-tooth dental prosthesis formed through use of the dental implant component; Figure 8 is a schematic side view of the first temporary single-tooth dental prosthesis in the process of being mounted intra-orally onto an abutment sleeve; Figure 9 is a side view, mainly in cross-section, of a second temporary single-tooth dental prosthesis formed through use of the dental implant component; Figure 10 is a side view of the second temporary single-tooth dental prosthesis in the process of being mounted extra-orally onto an abutment sleeve; and Figure 11 is a schematic side view of the second temporary single-tooth dental prosthesis-abutment sleeve assembly in the process of being secured intra-orally to a fixture with an abutment screw. Description of the Exemplary Embodiments of the Invention In Figures 1 to 6 there is shown a dental implant component 10 on which a dental prosthesis or a core part thereof is intended to be fabricated in accordance with the invention. The dental implant component 10 has a metal, e.g. titanium, or plastic body 1 having a proximal end 2 and a distal end 6 which is formed by a peripheral wall structure comprising a side wall section 3 which extends from the proximal end 2 of the body 1 to a roof wall section 5 at the distal end 6. The inner surface of the peripheral wall structure bounds a channel or cavity 7 in the body 1 having a proximal opening 9 in the proximal end 2. As shown in Figures 2 to 4, the inner surface of the side wall section 3 at the proximal opening 9 defines an octagonal cross-section 11 for anti-rotational engagement and indexing with a complementary octagonal cross-section on a coronal end of a sleeve part of an abutment which is, or will be, anchored to a fixture implanted in the jaw bone, as will be described in more detail hereinafter. As will be appreciated by those versed in the art, other complementary forms for the anti-rotational engagement of the body 1 to the abutment sleeve could easily be adopted. The outer surface of the side wall section 3 adjacent the proximal opening 9 defines an annular shoulder 4 for supporting the dental prosthesis, for example an artificial tooth formed from acrylic resin, or a core part of the dental prosthesis, for example a cast inner framework formed by the lost-wax process, as will also be described in more detail hereinafter. The roof wall section 5 of the body 1 of the dental implant component 10 has a base part 12 and a projection part 13 which comprises a shaft portion 15 and a transversely-extending flange portion 17. As shown in Figure 2, an inner or proximal surface of the base part 12 has a recess 18 over a region thereof and the projection part 13 has a central channel 8 formed therein which extends above an outer or distal surface of the base part 12 of the roof wall section 5. Referring now to Figures 2, 5 and 6, an annular V-shaped grooved track 19 is provided in the outer surface of the roof wall section 5 in' registration with a peripheral edge 21 of the recess 18 in the inner surface of the base part 12 of the roof wall section 5. The dental implant component 10 provides the practitioner with two different methods for fabricating a dental prosthesis or core part, as will be elucidated hereinafter with reference to Figures 7 to 11 in which common elements are assigned common reference numerals. Figures 7 to 11 illustrate the fabrication of an acrylic artificial tooth 32 on the body 1 to form a temporary single-tooth dental prosthesis 30; 40 which is to be mounted onto the coronal end of a sleeve part 34 of an abutment which is screw retained, or will be screw retained, by an abutment screw 36 to the coronal end of a fixture 38 implanted in the bone of a partially edentulous jaw of a patient at a site where a natural tooth has been lost. Common to both methods is the preparation of a model of the partially edentulous jaw of the patient in which an analogue structure 42 having an end 44 which is an analogue or replica of the coronal end of the abutment sleeve 34 - called an "abutment analogue" or "abutment replica" - is incorporated to accurately reproduce the disposition and orientation that the coronal end of the abutment sleeve 34 adopts, or will adopt, in the jaw bone with respect to the surrounding dentition. In the first and more simple method illustrated in Figures 7 and 8, the body 1 is mounted onto the analogue end 44 of the abutment analogue 42 and acrylic resin applied over the surface of the body 1 including the roof wall section 5 with the acrylic resin being supported on the shoulder 4. The acrylic resin is shaped into a natural-looking tooth 32 which fits in with the representation on the model of the existing dentition of the patient adjacent the fixture site and then hardened by curing. The transversely-extending flange 17 acts to prevent axial displacement of the acrylic tooth 32 relative to the body 1 and anti-rotational locking of the acrylic tooth 32 on the body can be achieved through roughening provided on the outer surface of the body 1, for example pitting caused by blasting of the outer surface. Referring to Figure 8, before the prosthesis 30 is secured to the abutment sleeve 34 the abutment sleeve 34 is mounted to the fixture 38 and screw retained thereto by the abutment screw 36 (not shown) which passes through the abutment sleeve 34 so that the threaded shank thereof can screw into an internally-threaded socket in the coronal end of the fixture 38 and cause a head of the screw to bear against an internal surface in the abutment sleeve 34 to lock the abutment sleeve 34 to the fixture 38. The prosthesis 30 is then cemented to the abutment sleeve 34 intra- orally with the octagonal cross-sectional feature 11 at the proximal opening 9 in the body 1 of the dental implant component 10 engaging with a complementary octagonal cross-sectional feature 33 on the abutment sleeve 34 to lock the prosthesis 30 against rotation on the abutment sleeve 34. The mating octagonal cross-sections also act as indexing means to ensure the correct orientation of the prosthesis 30 in the jaw. Referring now to Figures 9 to 11, in the second method a distal opening to the channel 7 is formed in the roof wall section 5 of the body 1 by firstly cutting through the shaft portion 15 of the projection part 13 to remove the transversely- extending flange portion 17 and expose the central channel 8. The base part 12 is then ground away radially outwardly to the annular grooved track 19. In this connection, t e central channel 8 provides an access passage for a grinder to gain access to the exposed edges of the base part 12 and grinding away of the base part 12 is facilitated by the recess 18 in the inner surface of the roof wall section 5 reducing the wall thickness of the base part 12. The annular grooved track 19 acts to define the boundary line to which grinding is to end at, that is to say, it defines the cross-sectional area of the distal opening to be created in the distal end of the body 1, the reason for which will become apparent shortly. As shown in Figure 9, after the distal opening has been formed in the roof wall section 5 the body 1 is mounted on the abutment analogue 42. A threaded post 50 is then inserted through the open-ended channel in the body 1 created by the formation of the distal opening and into an internally-threaded socket 54 in the analogue end 44 of the abutment analogue 42. The cross-sectional area of the distal opening in the body 1 is such that it forms a close fit with the post 50. The acrylic tooth 32 is then formed on the body 1 around the post 50 with the result that the prosthesis 40 formed has an axially-extending open-ended channel 56, as shown in Figure 10. The advantage of the prosthesis 40 having the open-ended channel 56 is that the prosthesis 40 can now be cemented to the abutment sleeve 34 extra-orally, as will be understood from Figure 10. As will be further understood from Figure 11, the cemented prosthesis-abutment sleeve assembly 40, 34 is then mounted to the coronal end of the fixture 38 and the abutment screw 36 passed through the assembly to secure the assembly to the fixture 38 after which the channel is filled in. As the abutment sleeve 34 is cemented extra-orally to the dental prosthesis 40, it is possible for the abutment sleeve 34 to be releasably incorporated in the model in place of the analogue 42 thereby dispensing with the need for use of an additional component in the fabrication process. The advantage of forming the distal opening to the channel 7 of the dental implant component 10 such that a close fit is formed with the post 50 is that acrylic resin is prevented, at least to a major extent, from leaking into the channel 7 during the preparation of the acrylic tooth 32 and thereby (i) affecting the surface features at the proximal end 2 of the body 1 and making it difficult for the prosthesis 40 to seat properly on the abutment sleeve 34, and /or (ii) blocking the channel 7 and making it difficult for the abutment screw 36 to be inserted into the fixture 38. As can be seen, the dental implant component 10 in accordance with the invention gives the practitioner two different methods in which to form a temporary single- tooth dental prosthesis 30; 40 and concomitantly two different ways for anchoring the prosthesis 30; 40 to the jaw bone. It will be appreciated that the present invention has been illustrated with reference to exemplary embodiments and that the scope of the invention can be varied in many different ways within the scope of the appended claims. For example, although the use of a dental implant component in accordance with the present invention has been described with reference to the fabrication of a temporary single-tooth dental prosthesis it will be appreciated by those in the art that the present invention also has application for forming permanent single-tooth dental prostheses and for dental prostheses for replacement of a plurality of lost natural teeth, e.g. a bridge. Finally, the inclusion in the appended claims of reference numerals used in the accompanying drawings is purely for illustration and not to be construed as having a limiting effect on the scope of the claims.

Claims: Claims: 1. A dental implant component (10) on which a dental prosthesis (30; 40) or core part thereof is intended to be fabricated having a proximal end (2), a distal end (6) and a channel (7) which extends from a proximal opening (9) in the proximal end to the distal end, characterised in that the dental implant component is provided with a roof wall structure (5) at the distal end of which a predetermined area (18) is adapted to be removed to provide a distal opening to the channel of predetermined dimension for enabling a post (50) to be positioned in the channel during fabrication of the dental prosthesis or core part thereof with a close fit being formed between the post and the distal opening. 2. A dental implant component according to claim 1, characterised in that the predetermined area of the roof wall structure is a predetermined portion of the roof wall structure. 3. A dental implant component according to claim 2, characterised in that the predetermined area is of reduced wall thickness. 4. A dental implant component according to claim 3, characterised in that the predetermined area of the roof wall structure is a recessed area (18) of the roof wall structure. 5. A dental implant component according to claim 4, characterised in that the recessed area of the roof wall structure is formed by the provision of a recess (18) on a proximal surface of the roof wall structure. 6. A dental implant component according to any one of claims 2 to 5, characterised in that the predetermined area of the roof wall structure is delimited by a boundary marking (19) on a distal surface of the roof wall structure. 7. A dental implant component according to claim 6, characterised in that the boundary marking is in the form of a grooved track (19). 8. A dental implant component according to any one of the preceding claims, characterised in that the predetermined area of the roof wall structure consists of a first sub-area which is adapted to be removed to provide a pilot distal opening to the channel which is of a dimension less than the predetermined dimension and a second sub-area juxtaposed with the first sub-area which is adapted to be removed by grinding away of a peripheral edge of the pilot distal opening whereby the pilot distal opening is enlarged to the distal opening of the predetermined dimension. 9. A dental implant component according to claim 8, characterised in that the predetermined area of the roof wall structure consists of a transverse base (12) and a distally-extending projection (13) on the base into which the channel extends to define a cavity (8) in the projection of dimension less than the predetermined dimension whereby removal of the projection or a distal portion thereof to expose the cavity provides the pilot distal opening to the channel. 10. A dental implant component according to any one of claims 1 to 5, characterised in that the predetermined area of the roof wall structure is presented by a distally-extending projection (13) into which the channel extends to define a cavity (8) in the projection of the predetermined dimension whereby removal of the projection or a distal portion thereof to expose the cavity provides the distal opening to the channel of the predetermined dimension. 11. A dental implant component according to any one of the preceding claims, characterised in that an outer surface of the component is provided with a surface structure (17) for inhibiting proximal-distal movement of the dental prosthesis or core part fabricated thereon. 12. A dental implant component according to claim 11 when appendant on claim 9 or claim 10, characterised in that the projection presents a transversely- extending flange (17) at a distal end thereof for inhibiting proximal-distal movement of the dental prosthesis or core part fabricated thereon. 13. A dental implant component according to claim 1 or claim 2, characterised in that the predetermined area of the roof wall structure is a releasably securable portion of the component. 14. A dental implant system comprising a dental implant component (10) according to any one of claims 1 to 13 and a post (50) adapted for insertion in the channel (7) of the dental implant component through the distal opening to an operational position in which the post forms a close fit with the distal opening. 15. A method of forming a dental prosthesis (30; 40) for mounting on a coronal end (33) of a dental prosthesis support structure (34) comprising the steps of :- (i) providing a dental implant component (10) having a proximal end (2) for engagement with the coronal end of the dental prosthesis support structure, a distal end (6) capped by a roof wall structure (5) and a first channel (7) which extends from a proximal opening (9) in the proximal end to the roof wall structure; (ii) providing a post (50); (iii) providing a distal opening to the first channel through the roof wall structure of a size sufficient for the post to be inserted into the first channel; (iv) positioning the post in the first channel such that the post projects from the distal opening; and (v) forming the dental prosthesis by:- (a) fabricating an artificial tooth-presenting structure on the dental implant component with the projecting post being used such that an open-ended second channel is formed in the artificial tooth-presenting structure which communicates with the first channel, or (b) fabricating a core part of the dental prosthesis on the dental implant component with the projecting post being used such that an open-ended second channel is formed in the core part which communicates with the first channel and providing an artificial tooth-presenting structure on the core part. 16. A method according to claim 15, characterised by the step of providing a distal opening of dimension which produces a close fit with the post when inserted into the channel. 17. A method according to claim 16, characterised in that the dental implant component and post are a dental implant system according to claim 14. 18. A method according to any one of claims 15 to 17, characterised by the provision of an open-ended third channel in the artificial tooth-presenting structure which communicates with the second channel in the core part. 19. A dental implant component on which a dental prosthesis or core part thereof is intended to be fabricated substantially as herein described with reference to and illustrated by the accompanying Figures of drawings. 20. A method of forming a dental prosthesis substantially as herein described with reference to and illustrated by the accompanying Figures of drawings.

Inventors: BERGSTROEM NILS GUSTAF, BROBERG LEIF, CARISCH HANSRUEDI, HOLMEN ANDERS, BERGSTROEM, NILS, GUSTAF, BROBERG, LEIF, CARISCH, HANSRUEDI, HOLMEN, ANDERS
Applicants: ASTRA AB, BERGSTROEM NILS GUSTAF, BROBERG LEIF, CARISCH HANSRUEDI, HOLMEN ANDERS, ASTRA AKTIEBOLAG, BERGSTROEM, NILS, GUSTAF, BROBERG, LEIF, CARISCH, HANSRUEDI, HOLMEN, ANDERS
Application year: 1999
Main classification: A61C8
IPC codes: A61C8, A61C13