CA2107262C

CA2107262C - Dental implant

Info

Publication number: CA2107262C
Application number: CA002107262A
Authority: CA
Inventors: Milan Somborac; Stefan Charles Somborac
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-09-29
Filing date: 1993-09-29
Publication date: 2006-12-19
Anticipated expiration: 2013-09-29
Also published as: WO1995008963A1; CA2107262A1; US5636989A; AU7737294A

Abstract

A dental implant for installation into a mouth is disclosed. The implant includes a one piece implant body to which is attached an abutment portion for anchoring a denture or tooth replacement. The implant body includes a tapered apical portion and a coronal portion having a keyway. The abutment portion includes a key which mates with the keyway to form a non-rotational point. In one aspect of the invention, the abutment portion is cemented into the keyway. In another aspect of the invention the key is tapped in to the keyway to form a cold weld. There is also shown a method of installing a dental implant which includes press fitting the implant body into a preformed tapered bore at the implant site.

Description

RFSP File No. 7405-001 ~~.~ ~~b~

Title: DENTAL IMPLANT
FIELD OF THE INVENTION
This invention relates to dental implants of the type used in the mouth to stabilize dentures or support dental crowns and bridges.
BACKGROUND OF THE INVENTION
Dental implants used to stabilize dentures or support dental crowns and bridges have been known and have been used fairly extensively in the recent past. Such prior art devices are typically comprised of three components, namely, an implant component for anchoring to the bone, a transgingival component and a separate support component. The support component usually attaches to the transgingival component which, in turn attaches to the anchoring component at about the level of the bone. An artificial tooth or bridge may then be attached to this separate support component. This support component is sometimes referred to as an abutment portion, the transgingival component is sometimes referred to as an abutment connection or the transgingival collar or the transepithelial connection and the implant is sometimes referred to as a fixture.
An example of such a prior device may be found in Canadian Patent No. 1,313,597. This patent describes an implant for insertion into bone through an epithelial and fibrous connective tissue layer to which a prosthesis may be attached. This implant comprises a top portion for supporting a mechanical component to which the prosthesis may be connected and a body comprising an upper bone attachment region which tapers to a lower bone engagement region having a porous surface. The upper bone attachment region comprises a substantially non-porous but bioreactive surface and this patent teaches that this results in an upper bone attachment region which is claimed to be capable of enhancing bone attachment.

2~~'~2~2 However, several problems develop with an implant of this type. In particular, the patent teaches use of a collar 14 that is adapted to be coupled to the implant 12. However the interface between the collar 14 and the implant 12 occurs at a level below the gingiva in the installed position. Further, although the patent teaches providing recesses 40 on the lower surface 42 of the collar 14 to compliment projections 32 of the implant 12 to prevent rotation between the two components, in practice this is not effective. The attachment between the collar and the implant is accomplished by means of a threaded screw identified as 46 in Figure 1. Such a screw has a natural tendency to become loose during the vigorous stresses to which an implant of this type is subjected.
To avoid problems associated with the loosening of the threaded screw 46,.practitioners have resorted to insertion of cement into the threaded portion to ensure a locked and non-loosening joint between the implant component and the support component. Unfortunately, because the interface between the collar and the implant is below the gum level, any excess cement will be squeezed out at the interface and may not be noticed by the practitioner since it is hidden from view. Such excess accumulation of cement can create irritation of the gum and the bone and can result in infection and/or implant failure.
In addition, all implant systems, (fixture, abutment connection, abutment) which have this type of arrangement have a microgap between the fixture or implant and the abutment connection or the transgingival collar at the level of the bone. This microgap has been called an "endotoxin generator" by some authorities because it is a region for potential bacterial growth.
Other prior art devices include implants with threaded exteriors which require extensive and complicated methods for preparation of the gum and bone to accept the insert. As a result, such implants are difficult and ~~~~~~7~
_ 3 _ expensive to insert and the surgery is most often done by specialists. In any event they are not practical and result in excess discomfort for the patient and unnecessary difficulties for the dentist making the installation. For example, some require incising the gum to gain access to the bone; multiple drilling and reaming steps; installation of the implant; reattachment, by suturing or the like, of the gum over the implant site to promote healing; a return visit several months later to the dental office to have the gum again incised to allow access to the implant; insertion and attachment of the abutment portion; and final attachment of the prosthesis to the abutment portion. The first incision into the gum can promote scaring, making the second incision difficult.
SZJMMARY OF THE INVENTION
What is required is an implant which may be installed in an easy one-step method and yet which is secured to the bone and provides a firm anchor.
Preferably such an invention would also minimize the risk of infection or irritation of the bone and the gingiva and would provide for easy attachment with standard components. Further, such an implant would not require an excessive number of steps for installation, or excessive patient discomfort and would be quickly and efficiently installed in various types of installation conditions.
Therefore, according to the present invention there is an implant far anchoring a prasthetic device in bone, said implant comprising:
(a) a one piece body having:
(i) a root portion having a surface conducive to bone ingrowth;
(ii) a tapered emergent portion having a smooth biocompatible surface which is non-irritating to living tissue, and (iii) a coronal portion having a keyway; and (b) an abutment portion for insertion into said keyway, '-' said abutment portion including a key at one end for insertion into said keyway and a head for retention of said prosthetic device at the other end.
In a further aspect of the present invention there is provided a method of inserting a dental implant comprising:
incising through a gingival layer;
drilling a pilot hole, at an appropriate position into a bone located below said gingival layer;
drilling a recess, about said pilot hole, into the bone with a second drill bit to form a tapered recess of appropriate diameter;
positioning a one piece dental implant in the tapered recess;
gently tapping said implant into surface engagement with said bone wherein said step of tapping includes wedging a smooth emergent portion against a hard cortical bone portion and wedging a root portion coated with a material conducive to bone ingrowth into a cancellous region of the bone;
allowing said bone to grow into said root portion;
and securing an abutment portion to said implant.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference will now be made to preferred embodiments of the invention by reference to the attached drawings which are by way of example only and in which:
Figure 1 is a side view showing an implant according to the present invention;
Figure 2 is a front view of the implant of Figure 1;
Figure 3 is a front view of an abutment portion for an implant of Figure 1 adapted to act as an anchor for overdenture retention;
Figure 4 is a front view of an abutment portion for an implant of Figure 1 adapted to act as an anchor for a false tooth cap;
Figure 5 is a cross-sectional view through the 2~~'~~~~

abutment portion along the lines 4-4 of Figure 4;
Figure 6 is a side view of a healing cap for use in association with the implant of Figure 1;
Figure 7 is a view of the implant partially inserted;
Figure 8 is a view showing the implant of Figure 1 in an installed position; and Figure 9 is a view of a drill for inserting the implant of Figure 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1 shows a one piece body or implant 10 having a coronal portion 12 and an apical portion 14. Beginning at the bottom of the one piece body 10 there is shown a tapered section 16 above which is a cylindrical section 18. The tapered section 16 and the cylindrical section 18 are suitably coated with a material which is conducive to bone ingrowth and which is identified as 20. These sections 16, 18 together may be considered as a root portion. The preferred form of bony ingrowth material is of the type which creates a multitude of tiny passageways.
This can be accomplished, for example, by fine wire mesh screens or the like, but the preferred form is to use discrete particles of titanium alloy which are bonded to the outside of the implant in a random fashion. The preferred method of bonding is by sintering, as will be known by those skilled in the art. The preferred size of particles is between 45 to 3.50 microns although other sizes may also be appropriate for bony ingrowth, as will be known to those skilled in the art.
The one piece implant consisting of the coronal portion 12, the body 10, with the apical portion 14, is preferably made of titanium alloy, Ti6A14Va, and the coating material is made of commercially pure titanium.
Above the cylindrical section 18 coated with bony ingrowth material 20 is a tapered, smooth-walled portion 22. The taper of portion 22 may be referred to as the "fourth taper". The smooth wall is an important aspect of the present invention. To avoid gum and bone infection it 2~.~'~?62 is important to have a relatively smooth nonporous surface which is biocompatible at the emergent portion. In particular, it is preferred if the emergent region is machine polished rather than highly polished. Also it is preferred if the emergent cylindrical portion 18 and the tapered portion shown as A in Figure 1 is preferably 176 degrees. The preferred length of the smooth walled portion 22 is .06 in. (1.50 m.m.).
The coronal portion 12 begins with a tapered section 24 increasing in diameter towards the end of the coronal portion 12, and which ends at a generally horizontal top portion 28. Between tapered section 24 and the top 28 are located two further tapered sections, identified as 25 and 26 respectively. The preferred total length of the coronal portion 12 is .16 in. (4.00 m.m.), of which the axial length of tapered section 24 is .12 in. (3.00 m.m.) and of each of sections 25, 26 is .02 in. (0.50 m.m.).
Located within the coronal portion is a keyway identified as 30 which includes a tapered section 32 and a part cylindrical section 34. The taper on section 32 may also be referred to as the "first taper". Located between these two sections is a toroidal section 36 which may be formed in a part circular shape with cross-section having a .O1 in. (0.30 m.m.) diameter.
Located at the top of the coronal portion 12 is a cross groove 38 which is shown more clearly in Figure 2.
The purpose of this groove is to provide an additional keyway to resist rotation of the parts of the present invention with respect to each other as will be appreciated from the following description.
Turning to Figure 3, an abutment portion indicated generally as 40 is shown. The abutment portion is formed with a key 42 (also referred to as a keyway insertion portion) for insertion into the keyway 30 of the implant 10 and a head 42 which is in the form of a common anchor for overdenture retention. As can be seen in Figure 3, a locking bar 46 is provided which mates with groove 38 on the coronal portion of implant 10. Also, it can be seen that a tapered section indicated at 48, also referred to as a second taper, is provided on the key for the purpose of locking the abutment portion 40 into the implant 10.
Figure 4 is a view of a second abutment portion 50 of the type used to act as an anchor for a single false tooth cap. The key portion 52 is identical to the key portion 42 of abutment 40 and includes a locking bar 56 which is identical to locking bar 46. The head portion 44 is in the form of a standard anchor for a single tooth cap.
Again, a tapered portion 58 is provided which is identical to the tapered portion 48.
Figure 5 shows a cross-sectional view along line 4-4 of Figure 4. As will be appreciated this view is identical for abutment portions 40 and 50, which according to the present invention have the same key portion. As can be seen, one face of the key portion 52, 42 is flat and is indicated as 60. Also shown is the underside of the head 44 which is shown as 62 as well as the locking bar which is shown as 56. The main portion of the key is shown as represented by the line 52 and the taper is represented by the area shown as 58. It can now be appreciated that the taper runs around the perimeter of the key except for at the plane surface 60.
It can now be appreciated how the abutment portions 40, 50 may be securely retained in the implant 10. The first aspect is that there is a non-rotational feature, namely the locking bars 46, 56 and the groove 38. This feature prevents the rotation of the abutment portion relative to the insert, when the abutment portion is fully inserted into the insert. It is preferred to use this feature to achieve secure non-rotational attachment.
It can now be appreciated that two types of locking are present between the abutment and the implant. The taper of the portion shown as 48 and 58 is preferably less than seven degrees and more than two degrees. Most 2~.0'~~~~
_8_ preferably this degree of taper is about four or five degrees. This degree of taper is desired to take advantage of a metallurgical phenomenon known as~cold welding which occurs between relatively smooth metal surfaces which have an interference fit and which are closely angled to each other. It is a feature of the present invention that a cold weld be formed between the mating surfaces of the key and the keyway. The weld can be effected by gently tapping the abutment portion into the implant portion. As will be appreciated, to achieve this weld the surfaces between which the weld is to be formed need to be carefully and properly finished, such as by sandblasting or the like.
The second manner of attaining secure attachment is the use of standard dental cement. It will be understood of course that this is an alternative to the cold welding method outlined above. In this method the cement can be inserted into the implant prior to the abutment portion key 52, 42 being inserted. The cementable abutment portions 40, 50 are about .001 in. (.035m.m.) smaller in radius than the keyway 30 to allow for cement space. The cement then forms a solid bond between the metal surfaces.
It is preferred in this approach to roughen the metal surfaces by serrating or the like to ensure a good bond with the cement. The toroidal section 36 can now be more fully understoad. Its purpose is to provide a reservoir into which excess cement may be driven upon insertion of the key into the keyway. Suitable cements for the metal to metal bonding are composite cements commonly used in clinical dentistry. Even in the Qvent that there is excess cement present, according to the present invention it will be forced out at an interface between the underside 62 of the head of the abutment portion and the top of the coronal portion, shown as 37 above the gum line and thus will be clearly visible to the practitioner and readily removed while still soft.
Figure 6 shows a healing cap which may be used to ~~~~2u2 _ g _ protect the keyway 30 while the bone is healing and growing into the implant prior to an abutment portion 50 or 40 being inserted. The healing cap is identified generally at 70 and includes a coronal portion 72 which is gently curved and a keyway portion 74 which is intended to be press fit into the keyway 30. The keyway portion 74 is comprised of two limbs 76 and 78 separated by a groove 80.
By means of the groove, the portion 76 and 78 may be compressed inwardly into the keyway 30 and securely retained in position.
It will be also noted that the healing cap 70 includes an insert portion 82 which accommodates the upper part of the coronal portion 12 of the one piece implant. The surfaces 84, 86, 88, and 90 are intended to cover and capture the coronal portion of the implant. By means of the inward angle of the portions 84, the healing cap snaps into place over top of the coronal portion of the one piece implant 10. In this manner, the healing cap is securely held in place in addition to the compression of the keyway portions 76 and 78. Preferably the healing cap 70 is made of a polymer material for flexible retention in the coronal portion:
With reference to Figures 7-9, it can now be appreciated how the implant of the present invention may be installed. The first step is to identify the site into which installation is to occur. As will be understood by skilled practitioners, the necessary ground work to prepare for installation will involve the obtaining and careful analysis of X-rays or other suitable imaging techniques to enable a full understanding of the implant site to be gained. Once the location has been identified then it becomes necessary to identify the appropriate insert. It will now be appreciated that by forming the preferred implant with a cylindrical section 18 above the tapered apical gortion 14 the implant length can be varied according to site conditions. While the preferred axial length of the tapered apical portion 14 is .12 in. (3.00 ~~.0'~~62 - to -m.m.), the cylindrical section 18 can be made .14, .26, .37 or .49 in. (3.50, 6.50, 9.50 or 12.5 m.m.) This can then provide to the practitioner a range of implant depths to choose from again according to site specifics. In general, providing there is adequate integral bone the larger depths axe preferred.
Block et al. writing in J. Oral Maxillofac. Surg. 48:
174-178, 1990 and Stultz et al. writing in Compered.
Contin. Educ. Dent., Vol XTV, No.4, 478-486, and Walmsley have shown that implant success is directly proportional to implant length.
Once the proper implant length has been selected it is then necessary to prepare the gingiva 92 and bone 90 for the implant 10 (see Figure 7). This is accomplished by, after adequate anaesthetic of the patient, drilling a single recess 89 into the installation site. It is noted that the bone 90 of the installation site is generally composed of a soft cancellous portion 90A and a hard cortical portion 90B, and the gingiva 92 is generally composed of a gum 92A and a sub-gum or derma 92B.
According to the present invention only a single final drill bit 93 need be used as shown in Figure 9. The drill bit 93 has a tapered section 94 and a cylindrical section 95. It will be appreciated that the shape and dimension of sections 94, 95 of the drill bit should closely correspond to 'that of the selected implant 10. However, it is preferable for the tapered section 94 to be just slightly longer than the carresponding implant, for example by .03in. (0.75 m.m.), for ease of fit.
The cylindrical section 94 has opposed cutting edges 96 (only one of which is shown). A tapered coronal portion 97 has one or more discrete, protruding cutting teeth 98 thereon. The taper on the coronal portion 97 may be referred to as the "third taper". Reference numeral 99 indicates another set of cutting edges on the tapered section 94 (which has three or four sets of such edges, as desired). A smaller diameter upper portion 100 of the drill 93 has a keyway adapter 101 at its top end for engaging a drive mechanism of a dentist's drill (not shown). A hollow stem or bore 102 extends through the drill 93 along its length, as shown. A saline coolant is delivered from the drill to an opening 103 through the bore 102 to cool the drill bit and prevent heat build up, which heat could damage the living cells being drilled into.
The use of the single final drill bit 93 is preceded by the use of a conventional smaller pilot drill (not shown). The pilot drill also has a hollow stem or bore to allow internal irrigation with normal saline solution.
Additionally, external irrigation maybe used (for both drills) to cool the site being drilled to prevent damage to the bone tissue during the site preparation.
The drill 93 of the present invention differs from prior art systems which use a parallel sided final drill, either with a hollow stem or with a solid stem (which permits external irrigation only). The tapered portion of the surgical site is prepared after, by a separate drill, thus allowing no control over the length of the midsection portion of the bone hole.
Once the recess 89 in the bone has been drilled, it will have a tapered apical portion. Referring back to Figure 7, an implant 10 according to the present invention is shown being installed into the recess 89 in the bone 90 and the gingiva 92 after the bone has been drilled. As can be seen, the lower section of the recess 89 tapers slightly, preferably in an amount less than 5°, over the depth of .12 in. (3.00 m.m.).
Figure 8 shows the implant in the fully installed position. To attain this position it is necessary to press the implant into the bone 90, by reason of the interference fit between the bone 90 and the implant 10.
This is preferably accomplished by gently tapping the coronal portion 12 of the implant to firmly seat the implant into the bone. Thereafter the healing cap 70 is 2~.0'~~'~2 installed and the patient is allowed to leave. A suitable period of a few months is allowed to elapse and then the patient can return for installation of an appropriate abutment portion. Those skilled in the art will appreciate that the two styles of abutment portions provided according to the present invention are conventional above the gum line and thus will be readily understood and used by practitioners.
At this point an important aspect of the invention can be better appreciated, namely how the implant 10 of the present invention and the bone 90 interact.' When the implant 10 is tapped into the recess 89 as shown in Figure 8, the smooth-walled (i.e. emergent) portion 22 causes the implant to initially be wedged into the hard cortical portion 90B of the jaw bone 90 to stabilize the implant in the recess 89. This wedging arises because of the taper of emergent portion 22 and because the diameter of the emergent portion 22 is slightly larger than the diameter of the recess, and is not due to any surface effects between the cortical bone 90B and the smooth biocompatible surface on emergent portion 22. During the ensuing months, the soft cancellous portion 90A of the jaw bone gradually grows into the coating 20 and attaches to the cylindrical section 18 of the implant. In the meantime, the cortical portion 90B slowly subsides away from the smooth biocompatible surface of the emergent portion 22.
Hence, the biocompatible surface of the emergent portion 22 only temporarily helps hold the implant 10 in place while the cancellous portion 90A bonds to the cylindrical section 18. It is believed that the stress induced into (i.e. the displacement of) the cortical portion 90B by the taper of the emergent portion 22 is insufficient to prevent the cortical portion 90B from subsiding and remoulding away from the implant.
It will be appreciated by those skilled in the art that the foregoing description is in respect of preferred embodiments and that various modifications can be made to the invention without departing from the broad scope of the appended claims. Some of these modifications have been suggested above, and others will be apparent to those skilled in the art. Fox example, the head portion 44, 54 may be angled relative to the key portion 42, 52, respectively, to allow the location of the implant to be varied based on site conditions without displacing the overdenture or bridge. The angle by which the head portion and the key portion may be angled is between 15° -35°. Also, the precise dimensions may be modified without changing the operation of the invention. And finally, while the invention has been described in association with overdentures and bridges, it will be appreciated that it can be used to secure other cosmetic devices, such as artificial ears or eyes.

Claims

1. An implant for anchoring a prosthetic device in bone, said implant comprising:
(a) a one piece body having:
(i) a root portion having a surface conducive to bone ingrowth;
(ii) a tapered emergent portion having a smooth biocompatible surface which is non-irritating to living tissue, said emergent portion having a tapered end connected to said root portion and increasing in diameter to an opposing end, wherein, in the installed position, the tapered emergent portion is wedged against a hard cortical bone portion to stabilize the one-piece body;
and (iii) a coronal portion connected to said opposing end of said emergent portion, said coronal portion having an unthreaded keyway; and (b) an abutment portion for insertion into said keyway, said abutment portion including a key at one end for insertion into said keyway and a head for retention of said prosthetic device at the other end.

2. An implant as claimed in claim 1 wherein said implant is a dental implant for installation into a mouth and said abutment portion meets said coronal portion at an interface, and in the installed position, said interface is beyond a gingival layer to allow a visual inspection of said interface.

3. The dental implant of claim 2 wherein said root portion is comprised of a straight walled section which ends in a tapered apical tip.

4. The dental implant of claim 3 wherein said coronal portion comprises at least one taper and said coronal portion is of greater average diameter than said straight walled section of said root portion.

5. The dental implant of claim 2 wherein said keyway is asymmetrical in cross-section to prevent rotation of said abutment portion relative to said one piece body.

6. The dental implant of claim 1 or claim 2, wherein said keyway includes a first taper and a planar surface opposite to said first taper, and said key includes a second taper and a mating planar surface opposite said second taper, the relationship between said first taper and said second taper being such as to cause a cold weld to form between the abutment portion and the one piece body.

7. The dental implant of claim 1 or claim 2, wherein said key is slightly smaller than said keyway, to facilitate the retention of a setting adhesive between said key and said keyway.

8. The dental implant of claim 6 wherein the difference between the first taper and the second taper is four degrees, with the first taper being larger than the second taper.

9. The implant of claim 1 further including a healing cap for sealing said keyway before insertion of said abutment portion into said keyway.

10. The implant of claim 9 wherein said healing cap is made from a polymer material which is flexibly retained on said coronal portion.

11. The dental implant of claim 3 wherein said straight walled portion may be made of different lengths to accommodate different conditions present in the location of installation of the implant.

12. The dental implant of claim 11 wherein the straight walled portion is between about 14 in (3.5 m.m.) and .49 in. (12.5 m.m.) long.

13. The dental implant of claim 2 wherein said abutment portion may be cemented into said one piece body portion and wherein any excess cement may be easily removed prior to hardening upon a visual inspection of said interface.

14. The dental implant of claim 13 wherein said key of said abutment portion has a surface, and said surface is roughened to promote a good bond with said cement.

15. The dental implant of claim 14 wherein said keyway includes a reservoir for accommodating excess cement.

16. The dental implant of claim 7 wherein at least a portion of said key is circular in cross section and has a first radius, and at least a portion of said keyway is circular in cross section and has a second radius, said first radius being about .035 m.m.
smaller than said second radius to allow for cement space.

17. An implant for anchoring a prosthetic device in bone, said implant comprising:
(a) a one piece body having:
(i) a root portion having a surface conducive to bone ingrowth, the root portion comprising a tapered apical portion and a generally cylindrical portion, the tapered apical portion having an increasing diameter from an end of said root portion to said generally cylindrical portion;
(ii) a tapered emergent portion having a smooth biocompatible surface which is non-irritating to living tissue, said emergent portion having a tapered end connected to said generally cylindrical portion and increasing in diameter to an opposing end, and (iii) a coronal portion connected to said opposing end of said emergent portion, said coronal portion having a keyway; and (b) an abutment portion for insertion into said keyway, said abutment portion including a key at one end for insertion into said keyway and a head for retention of said prosthetic device at the other end.

18. An implant as claimed in claim 17 wherein said implant is a dental implant for installation into a mouth and said abutment portion meets said coronal portion at an interface, and in the installed position, said interface is beyond a gingival layer to allow a visual inspection of said interface.

19. An implant as claimed in claim 18 wherein said coronal portion comprises at least one taper and said coronal portion is of greater average diameter than said generally cylindrical portion of said root portion.

20. An implant as claimed in claim 18 wherein said keyway is asymmetrical in cross-section to prevent rotation of said abutment portion relative to said one piece body.

21. An implant as claimed in claim 17 or claim 18, wherein said keyway includes a first taper and a planar surface opposite to said first taper, and said key includes a second taper and a mating planar surface opposite said second taper, the relationship between said first taper and said second taper being such as to cause a cold weld to form between the abutment portion and the one piece body.

22. An implant as claimed in claim 17 or claim 18, wherein said key is slightly smaller than said keyway, to facilitate the retention of a setting adhesive between said key and said keyway.

23. An implant as claimed in claim 21 wherein the difference between the first taper and the second taper is four degrees, with the first taper being larger than the second taper.

24. An implant as claimed in claim 17 further including a healing cap for sealing said keyway before insertion of said abutment portion into said keyway.

25. An implant as claimed in claim 24 wherein said healing cap is made from a polymer material which is flexibly retained on said coronal portion.

26. An implant as claimed in claim 17 or claim 18 wherein said generally cylindrical portion may be made of different lengths to accommodate different conditions present in the location of installation of the implant.

27. An implant as claimed in claim 11 wherein the generally cylindrical portion is between about .14 in (3.5 m.m.) and .49 in. (12.5 m.m.) long.

28. An implant as claimed in claim 18 wherein said abutment portion may be cemented into said one piece body portion and wherein any excess cement may be easily removed prior to hardening upon a visual inspection of said interface.

29. An implant as claimed in claim 28 wherein said key of said abutment portion has a surface, and said surface is roughened to promote a good bond with said cement.

30. An implant as claimed in claim 29 wherein said keyway includes a reservoir for accommodating excess cement.

31. An implant as claimed in claim 22 wherein at least a portion of said key is circular in cross section and has a first radius, and at least a portion of said keyway is circular in cross section and has a second radius, said first radius being about .035 m.m.
smaller than said second radius to allow for cement space.