Dental implant and method of insertion
A one-piece dental implant for endosteal and combined endosteal/subperiosteal osseointegration includes a force-transferring foot part for insertion into a jaw, the foot part including a frame in a closed geometric form having an interior open area and at least one bar connected with the frame and extending into the interior open area of the geometric form, said geometric form including at least a partial ring shape; a post that projects out of the jaw, said post connected with the foot part through the bar; and wherein a profile of the bar has a first height at a first transition region where it connects with the closed frame and a second height, which is greater than the first height, at a second transition region where it connects with the post, the height of the bar tapering from the second height to the first height. A method of inserting the disclosed one-piece dental implant for endosteal and combined endosteal/subperiosteal osseointegration into an alveolar bone with a vestibular side and a palatal side includes the steps of providing a one-piece dental implant having a force-transferring foot part for insertion into the alveolar bone and a post that projects out of the alveolar bone; inserting the dental implant into the vestibular side of the alveolar bone; securely engaging the dental implant in the palatal side of the alveolar bone, leaving a part of the dental implant protruding from the vestibular side of the alveolar bone; bending and adapting the protruding part of the dental implant to the vestibular side of the alveolar bone; and trimming extraneous parts of the dental implant.
This application is a continuation of U.S. application Ser. No. 10/163,034, filed Jun. 5, 2004, Ser. No. 09/829,351 filed 9 Apr. 2001, now U.S. Pat. No. ______, which is a continuation of U.S. application Ser. No. 09/437,643 filed Nov. 10, 1999, now abandoned, which claimed priority of German Application No. 298 20 487.8 filed on Nov. 11, 1998, German Application No. 299 08 207.5 filed on May 4, 1999, and European Application No. 99 250 289.8 filed on Aug. 25, 1999. This application also claims priority of German Application No. 202 02 424.5 filed on 14 Feb. 2002.
TECHNICAL FIELD OF THE INVENTIONThe invention relates generally to dental prosthetics and, more particularly, to a dental implant for endosteal and combined endosteal/subperiosteal basal osseointegration and to a method of inserting such an implant.
DESCRIPTION OF THE RELATED ARTDental screw, blade, and cylinder implants which osseointegrate along the vertical axis of the implant are already known. Basally osseointegrated implants developed from box and disk forms. For instance, U.S. Pat. No. 3,925,892 (Juillet) describes an implant having a rectangular base part and a post screwed into the base part. A one-piece implant with a separate abutment and a thread on the vertical portion of the implant is known from FR 2,302,715 (Clune-Cost). According to U.S. Pat. No. 4,722,687, Scortecci later developed a cutter as an osteotomy instrument for such an implant type, or an implant which serves as its own insertion instrument (U.S. Pat. No. 4,815,974). Symmetrically designed lateral implants as described in U.S. Pat. No. 4,344,757 (Streel) are less important, as is the development described in U.S. Pat. No. 4,964,801 (Kawahara), which offers an interrupted, preferably perforated, surface of a base part designed as a disk.
Because of the limited number of implants per jaw, special requirements are increasingly being placed on the material and design of the implants to be used. These requirements include:
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- that the properties of the implant material be as similar as possible to those of the bone, with corrosion resistance and biocompatibility;
- that the mechanical strength of the implant be very high with the smallest possible implant dimensions, the small dimensions being necessary to attain good defense against infection by good blood supply, and to give the smallest possible uninterrupted implant surface;
- that the forces applied be distributed evenly to the cortical bone of the jaw;
- that there be no force transfer directly to the jaw bone through the vertical part of the implant; and
- that the range of different implant sizes, which must be stocked, be as small as possible.
It is advantageous to transfer the masticatory forces into bone areas which are farther away from the post. In addition, the elastic properties of the implant should match the elasticity of the part of the facial skeleton treated with this implant. At the same time, though, the forces increase in the vicinity of the horizontal implant part, especially in the vicinity of the post. Increasing leverage produces this increase in force. In very unfavorable cases, this can cause fractures and breaks in the implant due to peak stresses, especially in the base part.
The present invention is directed to overcoming one or more of the problems set forth above.
SUMMARY OF THE INVENTIONAn aspect of the present invention is to provide a dental implant having implant geometry which allows rapid, low-stress isoelastic integration of the implant into the jaw bone while assuring that the basally osseointegrated implant is highly resistant to fatigue and breakage.
In accordance with an aspect of the invention, there is provided a one-piece dental implant for endosteal and combined endosteal/subperiosteal osseointegration that includes a force-transferring foot part for insertion into a jaw, the foot part including a frame in a closed geometric form having an interior open area and at least one bar connected with the frame and extending into the interior open area of the geometric form, said geometric form including at least a partial ring shape; a post that projects out of the jaw, said post connected with the foot part through the bar; and wherein a profile of the bar has a first height at a first transition region where it connects with the closed frame and a second height, which is greater than the first height, at a second transition region where it connects with the post, the height of the bar tapering from the second height to the first height.
A method of inserting a one-piece dental implant for endosteal and combined endosteal/subperiosteal osseointegration into an alveolar bone with a vestibular side and a palatal side includes the steps of providing a one-piece dental implant having a force-transferring foot part for insertion into the alveolar bone and a post that projects out of the alveolar bone; inserting the dental implant into the vestibular side of the alveolar bone; securely engaging the dental implant in the palatal side of the alveolar bone, leaving a part of the dental implant protruding from the vestibular side of the alveolar bone; bending and adapting the protruding part of the dental implant to the vestibular side of the alveolar bone; or trimming extraneous parts of the dental implant.
While crestal implants, i.e., screws and cylinder implants, are made rigid by the manufacturer according to the specifications, and so, together with the bridges mounted on them, give rigid implant prosthetic systems, the one-piece, basally osseointegrated implants according to an embodiment of the present invention make possible an approximately isoelastic connection between the compact jaw bone and the denture. Thus the bending forces that arise are better accepted because of the geometry of the base part and are distributed more evenly over the whole base part with lower peak stresses.
It has been found that the assumption that the implant must be rigid and fixed in the bone to prevent osteolysis is not correct. If the implant is in a region of bone subject to functional flexion, then the load transferring surfaces of the implant must follow that movement to remain attached to the bone on all sides.
Because of the implant geometry described, it is also possible to provide approximately isoelastic connections between bone and implant, in which the bone adapts to the elasticity of the implant by altering the matrix, changing the degree of mineralization and enlarging load transferring areas by bone induction. That happens extraordinarily successfully with the implant described.
The implant geometry described and the implants produced using it allow an isoelastic bond to the compact and spongy jaw bones. That avoids both force peaks with osteolytic effect and excessive movement of the implant with the potential consequences of osteolyses due to mobility, and inflammation of the connective tissue. That, though, requires a special distribution of stress from the forces being absorbed by the implant and transferred to the jaw in the vicinity of the framework, of the post, of the transition between the post and the framework, and in the transition to the abutment or bridge.
These aspects are merely illustrative of the innumerable aspects associated with the present invention and should not be deemed as limiting in any manner. These and other aspects, features and advantages of the present invention will become apparent from the following detailed description when taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGSReference is now made more particularly to the drawings which illustrate the best presently known mode of carrying out the invention and wherein similar reference characters indicate the same parts throughout the views.
FIGS. 6 to 8 are plan views of one-piece, basally osseointegratable dental implants according to various other embodiments;
The first truly basally osseointegrated implants have been proposed in EP 0 935 949 A1, the disclosure of which is hereby incorporated by reference. They are different from implants, which either have a totally rigid design or transfer forces through expanded surfaces along the vertical post (e.g., FR 2,302,715). On the basis of these basally osseointegrated implants, it is possible to provide strategic implant positioning independently of the presence of a vertical bone supply and to provide basally osseointegrated implant prosthetic systems. For example, the annular design of the base part and the connection of the base part to the post through bars has the advantage that, if high forces are applied, the post can deflect slightly into the spongiosa, while the annular base remains solidly anchored in the compacta, supporting a lasting solid seating of the implant in the jaw bone. Further, the positioning of the post outside the center of the base part, in the center of the semicircular ring, as well as the placement of the bars, preferably in the transition region between the semicircular ring and the rectangular outer frame of the base part not only allow acceptance and transfer of greater forces but, in particular, provide matching of the implant being used to the anatomy of the jaw bone and to the implant bed which is prepared surgically by milling.
The basally osseointegratable implant 1 shown in the figures comprises a base part 2, which is inserted into an implant bed prepared surgically, by milling into the jaw bone, and a post 3, on which a crown or some other type of dental prosthesis is mounted after the implant has healed. The post 3 is connected to the outer frame 8 of the base part by bars N, 4, 5, 6 and 16. Bars N, 4, 5, 6 and 16 join the profile of the outer frame 8, with the thickness H3, D3, through radii R1. As shown in
Depending on the forces to be introduced into implant 1 and the hardness of the selected implant material, the design of the implant, for a given diameter D of post 3, is determined by the radii R1 and R3 and by the thicknesses H1 and H3.
Post 3 is itself connected to the bars N, 4, 5, 6 and 16 through radii R3 at its foot region. It has a constricted section 15, which takes on the function of a deformation zone and is the place where any breakage should occur. In one embodiment, the constricted portion 15 is about ⅓ the length of the post, with expanded surfaces 17, hereafter described in detail, below this constricted portion 15. When the bending forces are very high, deformations occur particularly in this region, protecting the base part of the implant from possible fracture. The constricted region is dimensioned, in relation to the base, so that, if peak forces occur, there will be a fracture in the vicinity of the constricted region, while the base part remains undamaged. Thus replacement of the base part can be avoided. A fracture is generally the result of a prosthetic overload, which can be corrected after repairing the implant. In case of a fracture, for example, the implant can be repaired by affixing a replacement piece to the stump of the post as by cutting a thread on the remaining stump of the post, or by welding, or otherwise adhering the replacement piece. As the constricted region is more elastic and therefore moves more, a surface expansion would result in more irritation of the bone and even inflammation, with the known bad consequences. As mentioned previously, then, there are surface expansions 17 below the constricted region 15, while the remainder of the post 3 is given a polished surface.
Careful selection of the implant material is important for the isoelastic connection to the compact and spongy jaw bone. Implants may be made from pure titanium, which is available in four degrees of hardness. The softer the implant material is, the more closely its elasticity matches that of the jaw bone and the more easily the bone grows around the inserted implant 1. For instance, if one uses titanium with a higher degree of hardness because of the forces, which must be transferred, one can compensate for the bad effect on the elasticity by appropriately dimensioning the base part 2. Harder titanium needs a larger support.
With pure, softer titanium having a tensile strength of 250-450 MPa, for example, the profile height (i.e. thickness H1) of the framework for the base part 2 should be selected relatively thin, but no less than 0.6 mm. If the thickness H1 of the framework of the base part 2 is excessive, the implant 1, or the implant material, will not be elastic enough. On the other hand, if the areas of the implant, which transfer the forces, are too small, osteolysis will occur because the load per unit area is too great. Bone damage can also occur if the uninterrupted foreign body surface introduced into the body is too large.
While soft titanium can adapt to and bond well with the bone, it is also possible to produce very elastic implants with an alloy comprising about 85 parts titanium and 15 parts of molybdenum. It is advantageous to select such an alloy if the implants must be unusually delicate. Other ratios of titanium to molybdenum give similarly good results.
At the same time, elasticity zones are produced by the radii R1 and R3 and the thicknesses H1 and H3, together with the external thread 19 and a suitable choice of material for an abutment A at the distal end of post 3. In particular, an elastic zone is formed in the region of the contact between the abutment A and the post 3. A softer material, preferably Delrin, is used instead of the titanium previously described for the abutment A. The Delrin remains stable with respect to retention of a crown cemented onto it. Each of the elasticity zones is optimized such that the implant 1 has the highest possible elasticity with simultaneous assurance of load transfer into the jaw bone. In this manner, it makes possible and helps assure isoelastic osseointegration of the implant 1 into the jaw bone. In practice, the implants 1 have a vertical transition profile determined by the radii R3 and the thicknesses H1, H3; and a horizontal transition profile formed by the radii R1. The two thicknesses are matched to each other so as to give a final three-dimensional implant profile optimized for load transfer.
The cutouts in the base part 2, indicated as cutouts 9, 10 and 11, are selected so that, on one hand, they are as large as possible to assure optimal blood supply which promotes healing of implant 1 into the jaw bone. On the other hand, bar N and crossbars 12, 13 have as nearly as possible a round and stress-free profile. In this design, the force transfer in the vicinity of the post is completely independent of the form and design of the cutouts in base part 2, while the radii R3 between post 3 and the bars N likewise do not affect the shape and design of the cutouts.
Because of the thickened region at the foot of post 3, the forces applied are taken up more reliably by foot part 2 and transferred to the compacta of the jaw bone. At the same time, the design assures that if any extremely high forces occur, post 3 can deflect easily into the spongiosa, thus acting against a potential fracture of the implant 1. Furthermore, as explained above, the design of the bars N, 4, 5, 6 and 16 improves the blood supply. That also promotes bone growth and healing of the implant 1 into the jaw bone.
In one embodiment, base part 2 is made up of a semicircular ring 7 and a rectangular outer frame 8 which transition into each other without any discontinuity. As a deviation from that configuration, base part 2 can also have a round shape, as shown in
As is further apparent from
To promote rapid healing of the implant and to get better and more solid mounting in the jaw bone, base part 2 and the lower part of the post 3 enclosed by the compacta are given the previously mentioned surface increase 17 which enlarges the surface, while the region of the post 3 near the alveolar ridge has a smooth, preferably polished, surface. In this manner it is possible, by simple means, to counter abacterial inflammation caused by surface enlargements, especially in the connective tissue in the vicinity of the alveolar ridge. For implants with multiple base parts arranged in the axial direction of the post 3 (see
It has been found, especially for implants having numerous base parts separated from each other, that restructuring of the bone and forming of connective tissue occurs because of mechanical irritations in the vicinity of the post near the alveolar ridge and the crestal base part 29. This new structure initially includes no bacteria. Only at a later time does it become populated with bacteria so that, under some circumstances, resection of the crestal base part may become necessary. The mechanical irritations are due primarily to surface extensions that have previously been provided. Irritations can be limited to a large extent if those regions of the implant have a smooth, highly polished surface, contrary to state of the art practice.
In the embodiment shown in
The
With basally osseointegrated implants having round base parts, such as shown in
With respect to the insertion of implants 1 into the implant bed, it is advantageous to have a bar arrangement in which bars 5, 6 and 16 are aligned at 120° to each other, as shown in
Forces applied at a right angle to bars 4 of implant 1 shown in
In implants with bars 6, 16 and 20 arranged as shown in
However, if there should happen to be greater force introduced onto the section of base part 2 with the rectangular outer frame 8, two bars 6 and 16 should also be oriented in the direction of that segment in the interest of even force distribution, as shown in
Still better force distribution is attained by a crosswise arrangement of bars 21, 22, 23 and 24, as shown in
Selection of the inner and outer radii R6 and R4 of the frame part (base part 2) can affect the deformation of the ring, which depends on the transverse loading. If the inner radius R6 is smaller than the outer radius R4, then the peak stresses occur at the nose of the rounded part and near the guide bevel. That can help to lead the peak stresses away from the vicinity of the post to the bone. According to another feature, there is a guide bevel 14 at the insertion side of base part 2, which makes insertion and positioning implant 1 in the implant bed easier.
The configuration of the disclosed dental implant allows for a particularly advantageous method of insertion into the jaw illustrated in
As shown in
Using the disclosed method, it is possible to treat an entire jaw with only four implants positioned in the areas of the canines and the second molars. In cases of extraordinary atrophic mandibles, treatment with only three implants in the areas of the canines and one molar is possible. The disclosed method promotes correct functional loading of the mandible, which leads to bone growth. This bone growth may allow insertion of additional implants later.
It is possible to insert the implant through the sinus cavity 38 into the alveolar bone as illustrated by
In summary, the method of inserting the disclosed one-piece dental implant for endosteal and combined endosteal/subperiosteal osseointegration into an alveolar bone with a vestibular side and a palatal side may include some of the following steps: providing a one-piece dental implant having a force-transferring foot part for insertion into the alveolar bone and a post that projects out of the alveolar bone; inserting the dental implant into the vestibular side of the alveolar bone; securely engaging the dental implant in the palatal side of the alveolar bone, leaving a part of the dental implant protruding from the vestibular side of the alveolar bone; bending and adapting the protruding part of the dental implant to the vestibular side of the alveolar bone; and trimming extraneous parts of the dental implant. The step of inserting the dental implant may include inserting the dental implant through the sinus cavity or inserting the dental implant with the foot part of the implant below a nerve canal in a spongiosa region of the alveolar bone and with the post at the side of the nerve canal.
In the alternative slightly differently shaped cuts are contemplated. For example, a single longer cut 190 can be milled at about a right angle to cut 160 so that the combination of cut 160 and 190 is generally J-shaped; or the two cuts 190 may be substantially aligned so that the combination of cut 160 and cuts 190 is generally T-shaped. Such shaped cuts are especially adaptable for use with implants with an elongate foot or base part 2 such as shown in
In some cases it turns out to be a problem that the sinus is penetrated by the vertical impant part. Pressures building up inside the sinus (e.g. by strong breathing, nose-blowing) immediately after implant placement may cause an unwanted communication between the oral cavity and the maxillary sinus. This may also lead to an infection of the maxillary sinus which may then lead to a situation where the newly placed implants gets infected and has to be removed and placed again later.
Preventing this is by placing a fibrin clot around the implant, inside the maxiallary sinus and/or closing the t-shaped slot in the bone with the fibrin clot or a firbrin membrane as shown in
Other objects, features and advantages will be apparent to those skilled in the art. The invention in its broader aspects is not limited to the specific steps and embodiments shown and described but departures may be made therefrom within the scope of the appended claims without departing from the principles of the invention and without sacrificing its chief advantages.
Claims
1-28. (canceled)
29. A method of inserting a one-piece dental implant for endosteal and combined endosteal/subperiosteal osseointegration into an alveolar bone with a vestibular side and a palatal side, including the steps of:
- providing a one-piece dental implant having a force-transferring foot part for insertion into the alveolar bone and a post that projects out of the alveolar bone;
- inserting the dental implant into the vestibular side of the alveolar bone;
- securely engaging the dental implant in the palatal side of the alveolar bone, leaving a part of the dental implant protruding from the vestibular side of the alveolar bone;
- bending and adapting the protruding part of the dental implant to the vestibular side of the alveolar bone; and
- trimming extraneous parts of the dental implant.
30. A method of inserting a one-piece dental implant according to claim 29, wherein a part of the dental implant also protrudes from the palatal side of the alveolar bone and further including the step of bending and adapting the protruding part dental implant to the palatal side of the alveolar bone.
31. A method of inserting a one-piece dental implant according to claim 29, wherein the step of inserting the dental implant includes inserting the dental implant through the sinus cavity.
32. A method of inserting a one-piece dental implant according to claim 29, wherein the step of inserting the dental implant includes inserting the dental implant with the foot part of the implant below the canal of the nervus mentalis with the post at the side of the nerve canal.
33. A method of inserting a one-piece dental implant for endosteal and combined endosteal/subperiosteal osseointegration into an alveolar bone, including the steps of:
- providing a one-piece dental implant having a force-transferring foot part for insertion into the alveolar bone and a post that projects out of the alveolar bone;
- milling an implant bed into the alveolar bone by making a straight cut into one side of the alveolar bone then making a diverging cut further into the alveolar bone at an angle from the straight cut;
- inserting a first end of the dental implant into the alveolar bone through the straight cut and into the diverging cut; and
- inserting a second end of the dental implant into the alveolar bone by rotating the dental implant and placing said second end of the dental implant into the diverging cut.
34. A method as set forth in claim 33, wherein the step of milling an implant bed includes milling first and second diverging cuts in the alveolar bond at angles from the straight cut and extending away from one another; and the step of inserting the second end of the dental implant includes rotating the dental implant and placing said second end of the dental implant into the second diverging cut.
35. A method of preventing communication between an oral cavity and the maxiilary sinus of a dental implant patient, the method comprising:
- centrifuging venous blood from the patient;
- isolating a fibrin portion of the blood; and
- placing a fibrin clot into the sinus around transsinusally placed implants.
Type: Application
Filed: Apr 14, 2005
Publication Date: Dec 8, 2005
Inventor: Stefan Ihde (Uetliburg)
Application Number: 11/105,944