GB1583234A

GB1583234A - Enossal dental half implants

Info

Publication number: GB1583234A
Application number: GB2394379A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-09-04
Filing date: 1977-07-06
Publication date: 1981-01-21
Also published as: FR2368933B1; FR2368933A1

Description

(54) ENOSSAL DENTAL HALF IMPLANTS (71) I, HANS SCHEICHER, a German citizen of D 8 Munich 19, Rondell Neu wittelsbach 4, Western Germany (BRD), do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is performed, to be particularly described in and by the following statement: The present invention relates to enossal dental half-implants.

The half-implants of the present invention may be particularly easilly inserted with the aid of the drill head and drills which are described and claimed in the co-pending application No. 28397/77 (Serial No.

1,583,233).

Since the exact physiological relationships are not yet fully clear, a large number of enossal dental half-implants have already been developed and put forward, over whose suitability, however, opinions vary strongly. Above all, the success quotas are very different also for the single implant types. A general review of these familiar enossal dental half-implants is given in a dissertation by Johannes Randzio of the Medizinische Hochschule Hannover (clinic and outpatient department for jaw surgery), excerpts from which are also to be found in the Zeitschrift Orale Implantologie, journal 4 1976, pages 9 ff. The present application also uses the nomenclature used there.

With respect to the definitions of the individual concepts reference is made to the explanations given in the dissertation.

The dental half-implants currently most in use are the screw implant, especially according to Dr. S. Sandhaus (exemplified in a prospectus from the firm Maret with the title: "Implant endo-osseux CBS"), the so-called "Tubinger Sofortimplantat" or immediate implant (described in the magazine "Quintessenz" 27. volume June 1976, journal 6, pages 17 ff), the vitreous carbon implants (e.g. the Vitredent-Implant developed by the University of Southern California and described in a brochure put out by them), and the laminar implants according to Linkow and consisting of an elongated leaf-like endostructure furnished with perforations and having a projection at the top for the fitting on of the tooth superstructure. Implantation of the laminar implants made of titanium alloy is carried out in two stages. There is a series of further developments of laminar implants, e.g. the so-called "Zylinderimplantat" (article by Werner Lutz in "Die Quintessenz", 27.

volume, February 1976, journal 2, page 23 ff) and laminar implants which are coated with a porcelain layer in order to avoid metallosis (DT-OS 24 21 951).

The present invention has the task of creating an enossal dental half-implant with a large surface and good retention of the endostructure in the bone tissue, being free of sharp edges, at which centers of force are transmitted to the bones, opposing any distortion, tilting or loosening through any forces acting asymmetrically on it, especially shearing forces, and which can also be used where the bone tissue is in parts bad or receding, especially at points on the lower jaw where the jawbone above the nerves or vessels is not thick.

Accordingly, the present invention consists in an enossal dental half-implant with a tapering endostructure constructed as a dental root substitute, comprising at least two cone-like regions separated from one another at their pointed ends and overlapping at their bases, such that in use the endostructure exhibits a dumbbell-shaped cross-section (as hereinafter defined) in the region where the endostructure projects from the jawbone. More particularly the cone-like regions may overlap such that in ues the endostructure also exhibits a dumbbell shaped cross-section in a region located within the jawbone adjacent the region where the endostructure projects from the iawbone.

The enossal dental-half-implant (abbreviated to EDH in the following) according to the invention is stably anchored in the jaw by the senaration of its lower ends and by the constrictions in and below (i.e. within the jawbone) the area where the endostructure projects from the jawbone, these constrictions resulting from the overlapping of the conelike regions, so that the implant is not loosened even by shearing forces arising from non-uniform loading, but without the individual areas of the bone having to accommodate too great forces.

In addition the EDH according to the invention offers the possibility to bypass nerves or vessels by means of a corresponding orientation in the jawbone, so that these are between the separated lower ends of the conelike regions. It is also possible to bypass bad or weak points of the bone tissues in this way. The shaping of the EDH according to the invention in the upper region where it projects from the jawbone makes it possible to leave the implant in nosition also in the case of shrinkage of the jawbone and of the gum, without any cosmetic problems arising.

Should it at some time become necessary to remove the implant from the jawbone, no large lesions are created when it is taken out.

The endostructure exhibits a dumbbellshaped cross-section, at least in the area of projection from the jawbone. Surfaces of cut of the EDHs which have planes running approximately normal to the longitudinal axis of the tooth substitute borne by the endostructure are designated here as cross-section.

The longitudinal axis coincides approximately with the direction of the force applied to the tooth during the normal chewing process.

Under the designation "dumbbell-shaped cross-section" such cross-sectional shapes are to be understood to be those shapes which arise from the overlapping of two, or three or more circles, ovals or ellipses; those points at which the circles, ovals, or ellipses intersect are preferably rounded off in order to avoid sharp edges.

It is particularly advantageous if the conelike regions of the endostructure, there being at least two such regions, are elliptical, oval, or circular in cross-section, and if the edges and/or the points arising where the individual regions overlap are rounded off. The last mentioned measure prevents very high pressure forces from acting on discrete bone regions; these forces could cause the bone to recede.

The centre points of the cross-sectional areas of the cone-like regions, there being at least two such regions, preferably lie on straight lines which form the axes of the conelike regions. The cone-like regions are usefully limited at the sides by conical surfaces. This construction is particularly favourable since by means of meshing drills and drill heads, which drills and drill heads are the subject of the co-pending application No. 28397/77 (Serial No. 1,583,233) bone cavities, which correspond to the shapes of the EDHs can be produced in the jaw through simple drilling.

This effects not only a lodgement being stable against any distortion of the EDHs, but also reduces the danger of infection.

The bone cavities are especially easy to make if the axes of the cone-like regions run parallel to one another. For special cases of application and for adapting to peculiarities of the jawbone it can however be useful to let the axes of the cone-like regions run inclined to each other. If, however, the EDH consists of only two cone-like regions, then the axes preferably lie in one plane.

If the axes of two cone-like regions intersect beneath the endostructure in an acute angle a1, especially if the angle a1 is so chosen that an overlapping of the cone-like regions occurs shortly above their lower ends, one obtains EDHs which are particularly suitable for use as incisors or eye-teeth.

If on the other hand the axes of two conelike regions intersect above the endostructure in an acute angle a > , one obtains EDHs which are particularly suitable fqr cheek tooth implants since they have several largely independent "tooth roots" as in the natural cheek teeth. This construction makes possible a substantial bifurcation between the cone-like regions, so that the implant can have its lower ends led deep into the bone, even when there is a nerve strand lying high up, the nerve strand coming to lie in the bifurcation between the two cone-like regions in this case.

With respect to a production of bone cavities by simple~drilling by means of a suitable tool, it is particularly useful if the angle aa, which incorporates the two outermost cone-like regions with each other, fits the following relation: aa < ss 1 ss2 where p1 and 62 represent the angles which the cone-shaped shells of the cone-like regions enclose with the axes of same.

It is particularly favourable for the transmission of force to the bone structure if the angles ssl and ss2 are between about 4" and about 150.

The overlapping t between two cone-like regions in the EDHs according to the invention preferably satisfies the following relation: 0,15 x DtO,75 x D where D is the largest diameter of the conelike regions forming the endostructure. The degree of overlap tF is the distance over which the cone-like regions overlap along the lines connecting the points where the axes of the cone-like regions cut through the cross sectional area at the region of the endostructure's projection from the jawbone. By keeping to these relations bone cavities can still be produced in one operation by drilling using corresponding special drills and cutting heads.

According to a particularly useful structure of the EDHs according to the invention, the cone-like regions of the endostructure taper conically over some three quarters to some two thirds of their length, then being shaped cylindrically at their lower ends over some 4 to 9 of their length.

For most fields of application one obtains excellent results if, for the conical part of a cone-like region, the relation of the greatest diameter to the smallest diameter is from about 1.4:1 to about 4.0:1, preferably from about 1.6:1 to about 1.8:1.

For some areas of application, particularly when it is not possible to produce deep bone cavities in the jaw, one is recommended to arrange three cone-like regions lying in a triangle beside each other in such a way that two of these regions touch each other whilst each at the same time intersecting with the third. Using a special drill head and three special corresponding drills a bone cavity for this EDH can also still be produced in one operation by drilling, so that one obtains a very accurately-shaped and exact form which corresponds to the outer contour of the EDH to be implanted.

The individual cone-like regions of the EDHs according to the invention can fundamentally be of varying length and/or exhibit varying diameters in any one cross-sectional plane. Through the use of corresponding drill combinations suitable bone cavities can be produced in these cases too by simple drilling.

In general, however, unless there are special circumstances in the jaw to be considered, EDHs are preferable where all the cone-like regions are of the same formation. This simplifies insertion and helps to avoid errors occurring when using the corresponding drills.

The longitudinal extension of the EDHs is usually measured such that on insertion into the jaw the upper edge of the endostructure is flush with the upper edge of the jaw ridge.

The endostructure is provided on its upper side with some kind of conventional attachment for fixing on the artificial tooth superstructure. In a special modification of the EDHs according to the invention, the endostructure contour is continued or extended upwards in the region of the exostructure.

When inserting these EDHs the bone cavity is drilled to the desired depth and the EDH inserted by trial. The area projecting above the bone ridge is then trimmed in such a way that it forms the basis for the conventional construction of an artificial tooth, such as, for example, a jacket crown or a metal ceramic construction. The implantation of the EDHs according to the invention can follow in one or in two stages.

In a further refinement of the EDHs according to the invention the endostructure and/or the suprastructure are furnished with consecutive markings, in the longitudinal direction, so that they can be used, for example by means of an X-ray picture, as template when drilling the bone cavity.

To improve retention in the case of the EDH according to the invention, the endostructure is provided with undercuts and/or grooves and/or perforations and/or slight depressions and/or with a porous surface layer. This structuring of the surface can be carried out in any familiar way. In addition, the EDH can consist of any material exhibiting an adequate rigidity, so long as this is tolerated by the tissues or else is coated with another material which may be tolerated by the tissues. A particularly good retention is obtained with the porous surface layer, which, as dental periosteum substitute, guarantees an optimal growing together of bone and implant.

The chances of the implant not being pushed out are thereby improved.

A porous surface layer for implants is exemplified in the DT-OS 2 419 080. One obtains this surface layer by adding incinerated bone or dentine dust to a ceramic substance at 8000 C; on burning the ceramic substance at a temperature of about 10000C carbon dioxide is given off, so that pores are formed whose individual diameters are on the average at least 100 am.

An optional retention of the EDHs according to the invention is obtained however if this is provided with a porous surface layer as is described in our co-pending British Patent Application No. 10908/77 (Serial No.

1,573,130).

In the case of the EDH according to the invention the porous surface layer may cover the entire endostructure up to the protrusion of same from the jaw edge. The EDH is preferably covered with a glazing in the upward-bonding area, so that the part extending through the mucous membrane tissue exhibits a surface as smooth as possible, on which no bacteria can reside.

Further details and advantages of the invention become evident from the accompanying drawings of preferred embodiments.

Figure 1 shows a lateral view of a first version of the enossal dental half-implants according to the invention, whereby the endostructure consists of two cone-like regions partly overlapping in the upper areas.

Figure 2 shows a top view of the arrangement shown in Figure 1, in the direction of the arrow II.

Figure 3 shows a lateral view of a further version of the enossal dental half-implants according to the invention, in which case the endostructure comprises three serially-arranged cone-like regions, intersecting at the top.

Figure 4 shows a top view of the enossal dental half-implant shown in Figure 3, in the direction of the arrow IV, which shows that the three cone-like regions are arranged along a slight curve.

Figure 5 shows a top view of a further version of the enossal dental half-implant according to the invention, the three conelike regions being arranged as a triangle in this case.

Figure 6 shows in the upper part, in lateral view, a variant of the enossal dental halfimplant according to the invention and shown in Fig. 1, whereby the cone-like regions are so inclined to one another that they overlap for most of their length, and in the lower part a schematic section through a bone cavity provided in a jaw ridge for the insertion of this implant.

Figure 7 shows in the upper region, in lateral view, a further variant of the enossal dental half-implant shown in Fig. 1, whereby the two cone-like regions are so inclined to one another that their outer edges run almost parallel to one another, meaning that a large V-shaped recess is created between them, and in the lower part a schematic section through a bone cavity provided in a jaw ridge for the insertion of this implant.

The Figures 8-10 show longitudinal sections along the line VIlI-VIlI from Fig. 2 through various versions bf the cone-like regions comprising the endostructure.

Figures lli14 show in a perspective presentation various versions of the enossal dental half-implant according to the invention for clarification as to some possibilities for the attachment of the tooth superstructure to be attached onto the endostructure.

Figure 15 shows a longitudinal section through one of the cone-like regions of the endostructure of an enossal dental halfimplant according to the invention, with uniformly constructed exostructure which for eaxmple's sake is shown as an incisor crown.

Since the EDH according to the invention has basically to do with the endostructure, while as exostructure any sort of conventional tooth or bridge construction matching the neighbouring teeth in each case can be used, the Figs. 1-10 show in each case only the endostructure of the EDHs. The length L of the endostructure corresponds to at least the depth of the bone cavity bored in the jawbone and being intended to accommodate it. It is generally larger than this, since it is possible to reduce the EDHs by removal of material on the top side to the desired length or to trim it with a diamond-grinding body such that at least a pin or a peg for the mounting of the tooth substitute remains.

The endostructure 1 of the EDH shown in Figure 1 consists of two cone-like regions 2 and 3 over-lapping in the upper 1 of the regions. The cone-like regions 2 and 3 consist in the case shown of two similar circular cones, which in the region where the endostructure projects from the jawbone - ie.

at the upper end - as can be seen from Fig.

2, exhibit the diameter D and overlap there by an amount t measured along the connecting line through the exit points of their axes 4 and 5. The circular cones are rounded at their lower ends in such a way that the cone-like regions taper conically for approximately 9 to approximately 3 of their length, then being shaped cylindrically at their lower ends over some 42 to 9 of their length. In the case shown the overlap tF fits the relation: tf = 0,17 x D .

The relation between D and L is approximately 1:2,5. The axes 4 and 5 of the conelike regions lie in one plane and run parallel to one another. The inner edges 6 and 7 formed where the cone-shaped shells of the two cone-like regions intersect are rounded off, as is also the point 8 created at the lower end of the over-lapping regions. The brokenlined circles 9 and 10 in Fig. 2 indicate the lower ends of the circular cone stumps at the point where the rounding off of the lower ends of the cone-like regions begins. It can be seen from Fig. 2 that for the diameter d of these circles 9 and 10 the relation: d=D-2t approximately fits. The diameter d of the circles 9 and 10 corresponds also essentially to the axis diameter of the special bone drills (described in the co-pending Patent Application No. 28397/77 (Serial No. 1,583,233).

These are held pairwise and at a distance corresponding to that between the axes 4 and 5 in a corresponding mounting of a matching drill head in such a way that their cutting areas overlap. By means of this arrangement it is possible through simple drilling to produce a bone cavity in the jaw bone for the insertion of the EDH, the outer contour of the bone cavity corresponding exactly to the outer contour of the EDH. The endostructure shown in the Figs. 3 and 4 corresponds essen- tially to the versions shown in the Figs. 1 and 2, whereby in addition to the two overlapping cone-like regions 2 and 3 a corresponding similar third cone-like region 11 is provided, this being positioned in line with the other two cone-like regions. In the case shown, the axis 12 of the third cone-like region 11 is parallel to the axes 4 and 5 of the first two cone-like regions 2 and 3. However the axis 12 no longer lies in the plane formed by the axes 4 and 5, being laterally displaced from this, so that the cross section of the endostructure - seen from Fig. 4 - curves slightly downwards. This curving of the endostructure enables the EDH to be adapted to the curve of the mandibular arch.

Figure 5 shows a top view of a further development of the version shown in Figs. 3 and 4, whereby a third cone-like region 13 with an axis 14 is arranged laterally to the overlapping cone-like regions 2 and 3 with the axes 4 and 5 in such a way that it overlaps with the second cone-like region 3 whilst just touching the first cone-like region 2 at a point laterally or along a straight line. The edges and points formed at the intersections and the contact points are rounded off. In principle one can also position the third conelike region 13 in such a way that an additional overlap with the first cone-like region 2 results, so that the exit points of the axes 4, 5 and 14 can possibly form an equilateral triangle. However the version shown in Fig.

5 is preferable for practical reasons, since in this case the production of a corresponding bone cavitv in one operation is still possible, through drilling, by means of three drills overlapping in their cutting regions and being held in a corresponding drill head. This is not possible for an endostructure where the center points of the three mutually overlapping cone-like regions correspond to the corner points of an equilateral triangle, since in this case the three drills for the production of the corresponding bone cavity would in each case have to interlock pair-wise with their cutters, this only being possible when the two drills of a pair are driven in contra-rotation.

The endostructure shown in the Figures 3-5 can be extended by the addition of further cone-like regions, this occurring in a corresponding manner and not being depicted more closely in the drawings. Such an endostructure consisting of four or more cone-like regions is suitable for the insertion of bridge constructions in largely toothless jaws. In normal cases however endostructures with two or three cone-like regions are sufficient for a safe retention of the EDH.

The parallel alignment of the axes 4, 5, 12 and 14 as used in the previously-described versions effects in the case of the cone-like regions with conical outer surfaces an approximately uniform transmission of force to all areas of the wall of the jawbone surrounding the endostructure. In some cases it is useful however to deviate from this arrangement being for reasons of the force transmission seemingly favourable, and to incline the axes of the individual cone-like regions with respect to each other, as is for example, shown in the Figures 6 and 7.

The endostructure 15 shown in the upper part of Figure 6 contains two cone-like regions 16, 17, whose axes, 18, 19 are so inclined that they intersect at an acute angle a1 beneath the endostructure. This means that the two cone-like regions 16 and 17 overlap until shortly above their lower ends. To accommodate this endostructure being particularly suitable as tooth root substitute for incisor and eye teeth, bone cavities 21 whose outer contour eaxctly matches the outer contour of the endostructure 15 can be made in a jawbone 20 by simple drilling, as shown in the lower part of Fig. 6, using a corresponding drill pair, whose axes of rotation also enclose an angle a1. The arrows 22 indicate the direction with which the drills are sunk into the bone, as well as the direction with which the implant is subsequently embedded in the bone cavity 21.

In the arrangement of the endostructure 23 shown in Fig. 7, the two cone-like regions 24 and 25 are so inclined with respect to each other that their axes 26, 27 intersect above the endostructure at an acute angle c.

Thus the two cone-like regions 24 and 25 overlap only silghtly in the upper region, meaning that between their lower ends a deep V-shaped space 28 is formed. The endostructure 23 is intended in particular for those cases, where, as shown underneath in Fig. 7, a nerve or a vessel 29 runs in the bone tissue 20 of the jawbone at such a shallow depth that an implant according to previously known methods could not be inserted there at all, and an implant according to the Fig. 1-3 only with some risk. Even if the bone tissue under the middle of the implant to be inserted is cancellous, the use of an endostructure according to Fig. 7 can be of advantage.

Since it is of particular advantage when implanting the respective EDils if the accompanying bone cavity 30 can be made by simple drilling with a corresponding special tool, the angle aa between the axes 26 and 27 should not be chosen larger than the sum of the angle P, and 2 which the cone-shaped shells 31 and 32 enclose with the accompanying axes 26 and 27. This means, as seen from Fig. 7 that the outermost shell contours run approximately parallel to one another, when the angle aa is approximately equal to the sum of the angles 1 and 29 In the endostructure 15 and 23 the intersection edges and points have been rounded off.

The axes 18 and 19, and 26 and 27 of the cone-like regions lie in each case in a plane which coincides with the plane of the drawing of the Figs. 6 and 7. This is useful although not absolutely necessary. One can orientate the cone-like regions at such angles to one another that their axes intersect with the plane of the drawings. (This applies also for the versions of Fig. 1-5. The lines 4, 5, 12 or 18 and 19 or 26, 27 would then be projections of these axes, which run forwards or backwards out of the plane of the drawing when one puts the exit points of the axes in this plane.) The endostructures shown in the previous figures were formed in each case from similar, rotationally symmetric cone-like regions. It is however possible using methods already described, to combine varying cone-like regions into the endostructure, whereby the diameters D, the lengths L and the angle p between the axes and the cone-shaped shell can vary. Also in these cases a production of exactly-matching bone cavities through simple drilling is possible using a choice of corresponding drills.

It is finally also possible to design the cross section of the cone-like region oval or ellip tidal instead of circular, as in the previously' described examples, although in this case it is no longer possible to produce corresponding bone cavities through simple drilling with simple tools. The angle , between the axial direction and the shell walls should preferably however always lie between 40 and 150, whatever cross sectional surface is chosen for the cone-like regions.

The Figures 8, 9 and 10 show in longitudinal section different variants of the cone like regions with varying lengths L, diameters D and angles ,,B. The indices to the letters L, l', D, d given in brackets indicate examples of measurements in mm for a set of conelike regions of endostructures which are suitable for EDHs in the human field. The angle ,6 bounded by the cone-shaped shells and the axes is given in each case in degrees.

The following table gives a further example for a set of such EDHs. The top line with the values D indicates the maximal diameters in mm. of the cone-like regions of the endostructure while in the fins underneath, the lengths L in mm are given in each case for the type of endostructure as indicated on the left.

r r Type of D 3,0 3,5 4,0 4,5 5 6 8 endostructure ..

Figs. 1 and 2 ~ L 5 13 .L = 15 L = 15 L = 15 and and L = 20 L = 20 Figs. 3 and 4 L = 15 L = 15 I. = 15 L = 15 Fig. 5 L = 15 L= 15 L= 15 and L = 20 The Figures 11-14 exemplify some possi bilities for the attachment of which by means of conventional porcelain techniques or metal ceramic techniques dental prosthetic elements are produced.

When seen from the interior to the exterior, the EDH 42 consists of a core substance 43, in which a reinforcement element can if necessary be embedded. The core substance is surrounded on the exterior by a dentine substance 45, onto which in the region of the endostructure a porous surface layer 46 is applied.

The layer 6, being preferably about 0.3-0.5 mm thick, is permeated by a large number of vacuoles which enable an ingrowth of bone tissue when the endostructure 47 is implanted in a synthetic tooth cavity of the jaw.

Along the length of the endostructure 47 there are equidistant markings 48 provided in the porous surface layer 46, these markings consisting in the case shown of encircling grooves.

The suprastructure 49 forming the crown region of the EDH corresponds in its internal make-up essentially to the make-up of the endostructure 47. It differs from this only in that in place of the porous surface layer 46, a layer 50 consisting of an enamel substance and possibly a layer 51 consisting of a glazing substance is applied. Naturally the EDH 42 can also be furnished in the region of the exostructure 49 in familiar ways with substances and/or with colouring materials which enable the EDH to be optimally matched with the neighbouring natural teeth in the dentition The production of the EDH follows according to methods common in the dental field, whereby the porous surface layer 46, and if necessary with the enamel and glazing layers, is applied last of all. It is however also possible to fire the layer 46 on at the same time as the layer 45. The use of a porcelain technique is also possible (see eg. the magazine "Zahnärztliche Welt/Rundschau", journal 15, 78. vol. 1969, pages 682-687, and the magazine "Das Dentallabor" journal 8/1970 as well as the urofessional journal of the schweizerischen Zahntechnikvereinigung "Die Zahntechnik" Nr. 1t1969).

Examples for the porous surface layer 46, for the make-up of the EDHs using different materials and press techniques are also described by the same applicant in the patent application No. 10908/77 (Serial No.

1,573,130), to which reference is here made.

WHAT WE CLAIM IS: 1. An enossal dental half-implant with a tapering endostructure constructed as a dental root substitute, comprising at least two conelike regions separated from one another at their pointed ends and overlapping at their bases, such that in use the endostructure exhibits a dumbbell-shaped cross-section as hereinbefore defined in the region where the endostructure projects from the jawbone.

2. An enossal dental half-implant according to claim 1, wherein the cone-like regions overlap at their bases such that in use the endostructure exhibits a dumbbell-shaped crosssection in a region located within the jawbone adjacent the region where the endostructure projects from the jawbone.

3. An enossal dental half-implant according to claim 1 or 2, characterised in that the conelike regions of the endostructure are elliptical, oval or circular in cross-section.

4. An enossal dental half-implant as claimed in any of the preceding claims, characterised in that the sides of the cone-like regions are limited by conical surfaces.

5. An enossal dental half-implant as claimed in any of the preceding claims, characterised in that the edges and/or the points arising where the individual cone-like regions overlap are rounded off.

6. An enossal dental half-implant as claimed in any preceding claim, characterized in that the axes of two or more of the cone-like regions are parallel.

7. An enossal dental half-implant as claimed in any of claims 1 to 5, characterized in that the axes of the cone-like regions are not parallel.

8. An enossal dental half-implant as claimed in any of claims 1 to 7, characterized in that the axes lie in a plane.

9. An enossal dental half-implant as claimed in any of claims 1 to 5 or 7 or 8, characterized in that the axes of two cone-like regions intersect at a point outside of the cones and in a region next to the pointed ends of the cones.

10. An enossal dental half-implant as claimed in claim 9, characterized in that the angle formed by the axes is so chosen that the overlapping of the cone-like regions begins near their pointed ends.

11. An enossal dental half-implant as claimed in any of claims 1 to 5, or 7 or 8, characterized in that the axes of two cone-like regions intersect outside the cones in a region netx to the bases of the cone-like regions.

12. An enossal dental half-implant as claimed in claim 11. characterized in that the angle subtended between the two axes is less than or equal to the sum of the angles between the axis and side of each of the cone-like regions.

13. An enossal dental half-implant as claimed in any of claims 1 to 12, characterized in that each of the angles between the axis and side of each of the cone-like regions is between about 40 and about 150.

14. An enossal dental half-implant as claimed in any of the preceding claims, characterized in that the overlap between two conelike regions is such that the overlap of the cones when measured at the base of the cones and by theoretically extending the overlapping sides of the cones to the base is equal to between 15% and 75% of the diameter of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

which by means of conventional porcelain techniques or metal ceramic techniques dental prosthetic elements are produced.

When seen from the interior to the exterior, the EDH 42 consists of a core substance 43, in which a reinforcement element can if necessary be embedded. The core substance is surrounded on the exterior by a dentine substance 45, onto which in the region of the endostructure a porous surface layer 46 is applied.

The layer 6, being preferably about 0.3-0.5 mm thick, is permeated by a large number of vacuoles which enable an ingrowth of bone tissue when the endostructure 47 is implanted in a synthetic tooth cavity of the jaw.

Along the length of the endostructure 47 there are equidistant markings 48 provided in the porous surface layer 46, these markings consisting in the case shown of encircling grooves.

The suprastructure 49 forming the crown region of the EDH corresponds in its internal make-up essentially to the make-up of the endostructure 47. It differs from this only in that in place of the porous surface layer 46, a layer 50 consisting of an enamel substance and possibly a layer 51 consisting of a glazing substance is applied. Naturally the EDH 42 can also be furnished in the region of the exostructure 49 in familiar ways with substances and/or with colouring materials which enable the EDH to be optimally matched with the neighbouring natural teeth in the dentition The production of the EDH follows according to methods common in the dental field, whereby the porous surface layer 46, and if necessary with the enamel and glazing layers, is applied last of all. It is however also possible to fire the layer 46 on at the same time as the layer 45. The use of a porcelain technique is also possible (see eg. the magazine "Zahnärztliche Welt/Rundschau", journal 15, 78. vol. 1969, pages 682-687, and the magazine "Das Dentallabor" journal 8/1970 as well as the urofessional journal of the schweizerischen Zahntechnikvereinigung "Die Zahntechnik" Nr. 1t1969).

Examples for the porous surface layer 46, for the make-up of the EDHs using different materials and press techniques are also described by the same applicant in the patent application No. 10908/77 (Serial No.

1,573,130), to which reference is here made.

WHAT WE CLAIM IS:

1. An enossal dental half-implant with a tapering endostructure constructed as a dental root substitute, comprising at least two conelike regions separated from one another at their pointed ends and overlapping at their bases, such that in use the endostructure exhibits a dumbbell-shaped cross-section as hereinbefore defined in the region where the endostructure projects from the jawbone.

2. An enossal dental half-implant according to claim 1, wherein the cone-like regions overlap at their bases such that in use the endostructure exhibits a dumbbell-shaped crosssection in a region located within the jawbone adjacent the region where the endostructure projects from the jawbone.

3. An enossal dental half-implant according to claim 1 or 2, characterised in that the conelike regions of the endostructure are elliptical, oval or circular in cross-section.

4. An enossal dental half-implant as claimed in any of the preceding claims, characterised in that the sides of the cone-like regions are limited by conical surfaces.

5. An enossal dental half-implant as claimed in any of the preceding claims, characterised in that the edges and/or the points arising where the individual cone-like regions overlap are rounded off.

6. An enossal dental half-implant as claimed in any preceding claim, characterized in that the axes of two or more of the cone-like regions are parallel.

7. An enossal dental half-implant as claimed in any of claims 1 to 5, characterized in that the axes of the cone-like regions are not parallel.

8. An enossal dental half-implant as claimed in any of claims 1 to 7, characterized in that the axes lie in a plane.

9. An enossal dental half-implant as claimed in any of claims 1 to 5 or 7 or 8, characterized in that the axes of two cone-like regions intersect at a point outside of the cones and in a region next to the pointed ends of the cones.

10. An enossal dental half-implant as claimed in claim 9, characterized in that the angle formed by the axes is so chosen that the overlapping of the cone-like regions begins near their pointed ends.

11. An enossal dental half-implant as claimed in any of claims 1 to 5, or 7 or 8, characterized in that the axes of two cone-like regions intersect outside the cones in a region netx to the bases of the cone-like regions.

12. An enossal dental half-implant as claimed in claim 11. characterized in that the angle subtended between the two axes is less than or equal to the sum of the angles between the axis and side of each of the cone-like regions.

13. An enossal dental half-implant as claimed in any of claims 1 to 12, characterized in that each of the angles between the axis and side of each of the cone-like regions is between about 40 and about 150.

14. An enossal dental half-implant as claimed in any of the preceding claims, characterized in that the overlap between two conelike regions is such that the overlap of the cones when measured at the base of the cones and by theoretically extending the overlapping sides of the cones to the base is equal to between 15% and 75% of the diameter of

the base of the largest of the overlapping cones.

115. An enossal dental half-implant as claimed in any of-the preceding claims, characterized in that the cone-like regions of the endostructure taper conically over some i to some i of their length, then being shaped cylindrically at their lower ends over some 4 to some t of their length.

16. An enossal dental half-implant according to claim 15, characterized in that the ratio of the diameter of the base of a conically tapering region to the diameter at the narrowest point of the said conically tapering region is in the range of approximately 1.4:1 to approximately 4:1 and preferably in the range approximately 1.6:1 to approximately 17. An enossal dental half-implant as claimed in any of the preceding claims, characterized in taht there are provided three conelike regions lying in a triangle beside each other, and arranged in such a way that two of these regions touch each other whilst each at the same time they each intersect with the third.

!18. An enossal dental half-implant as claimed in any of the preceding claims, characterized by all the cone-like regions being of the same shape and/or size.

19. An enossal dental half-implant as claimed in any one of the preceding claims, characterized in that the contour of the endostructure is continued or extended upward in the region of the exostructure.

20. An enossal dental half-implant as claimed in any of the preceding claims, characterized in that the endo and/or the exostructure is furnished with consecutive markings in the longitudinal direction.

21. An enossal dental half-implant as claimed in any of the preceding claims, characterized in that the endostructure is provided with undercuts and/or grooves and/or perforations and/or slight depressions and/or with a porous surface layer.

22. An enossal dental half-implant substantially as hereinbefore described with reference to any one or any combination of the accompanying drawings.

23. An artificial tooth including an enossal dental half-implant as claimed in any of the preecding claims.