CA2224332A1 - Integral guided tissue regeneration barrier for root-form dental implant - Google Patents

Description

INTEGRAL GUIDED TISSUE REGENERATION BARRIER
FOR ROOT-FORM DENTAL IMPLANTS
The present invention relates generally to the field of dental implants.

BACKGROUND OF THE INVENTION
Prec;;clably useful dental implants had their beginnings in Sweden in the 1960's in work done by Per-lngmar Brane",a,k, who discovered that lab animals' bone cells would deposit mineralized bone directly on implanted titanium objects, thereby solidly allaching them to the surrounding bone. He is credited with coining 10 the term osseointegration, which is now in cor"l"on use, to identify this process.
Since his discovery, thousands of titanium implants of mostly screw-type design have been inserted in people's toothless sp~ces to anchor prosthetic teeth. This implantation has been done almost exclusively by elevating the soft tissue, drilling a hole in bone, placing the implant in the hole, slil~,ing the soft tissue back over the implant, waiting a period of months, re-opening the soft tissue, uncovering the implant and attaching a stud to project through the gum. If bone augmentation has been necessAry, yet more operations have been required.
If one counts the extraction surgery that leads to most toothless sp~ces, patients proyressing from having teeth to having a toothless space, then getting an implant and faslei, ng on a prosll,etic tooth, must submit to at least three surgeries.
The total would rise to five surgeries if bone augmentalion was required and done as a separale procedure. The number of surgeries would be reduced to one if an implant inserted on tooth removal would osseoinlegrale. If this could be done, patients would experience fewer painful, eA~e"sive and time-consuming surgeries and avoid bone loss in extraction sites, which is Associ~ted with problems of appearance, co",ro, l and insufficient bone volume for eventual implants. Their periods of wearing te,npGrary prosthetic replacement teeth or doing without teeth would be much shorter.
The unpredictability of sl ~ccess with currently available technology has meant that only a tiny propoi lion of implants have been placed in tooth socketsimmediately after teeth have been removed. C~uses of failure have been presence of bacteria in the sockets implant movement in the tooth socket due to the implant being inadequately fixed in place and soft tissue layers being deposited againsts titanium preventing osseointegration. One can reduce or eliminate bacteria from extraction sockets with antibiotics and surgical instruments. The other two causes of failure can be solved by the present invention: a guided tissue regeneration barrier i"legrated into root-form dental implants.
The invention is intended to make it possible to insert implants in tooth 10 sockets immediately after removal of teeth with pre~ictably successful osseointegration. To permit osseoinlegralion the integrated barrier pe,ror",s two functions: it i"creases the stability of the i",pla.lt and excludes unwanted cells from the extraction socket.
A rigidly d~la~;l,ed titanium mesh barrier will increase implant stability.
Its malleability will permit it to be closely adapted to the surface of the bone of the alveolar crest surrounding the e~cl,a~;tion site. It will retain the form into which it was shaped and allow circulation to be established through it preventing it from becoming ex,.,osed. The thinness of the individual titaniu~n wires making up the mesh will make it easy for a surgeon to cut it to fit around adjoining teeth and within the limits of the surgical site. The fact that it does not cause an inflammatory response will mean that the overlying mucosa sutured tightly over it will be able to prevent it from moving. Its rigid cor,ne~tion to the implant "~e",ber of the i",pla"l-barrier combination will help the implant resist any displacement forces that are applied to it.
Titanium mesh barriers have proven their usefulness in excluding cells that i"te, rere with bone apposilion (Gay et al., Oral Hea/th, May 1997 p 7-18). To increase bone volume where it would otherwise be i"adequate to contain an implant one can put a barrier over the bone to separate it from its overlying periosteum (the fibrous connective tissue enveloping bones) and mucous mer,lL,rane. The barriersfunction is to prevent fibrous tissue or mucous mei~brane from being created in the space in which new bone is wanted. It does this by preventing the migration of cells responsible for the unwanted tissue (fibrobl~sts and epithelial cells) into the space.
With the unwanted cells excluded bone cells (osteoblasts) will fill the space between existing bone and the barrier with new bone. Placing a barrier to achieve these ends iS termed guided tissue regeneration (GTR).
The present invention provides an integral barrier that can be placed directly on the bone of the alveolar crest surrounding the e~l,action socket. The barrier will allow os~eobl-~ts to deposit bone directly on the surface of the implant portion of the invention without having to compete with other cell types which would o otherwise populate the crestal portion of the healing socket. This GTR will thereby permit the blood clot around the implant in the exl,d~;tion socket to become mineralized bone osseoinlegraling the implant into the patient s jaw so that it can a"chor a prosli ,etic tooth.
Bec~use it has pores small enough to prevent cellular migration and lS bec~use it does not provoke i,lna",r"ation expanded polytetrafluoroell,ylene has been the most COilllllGn barrier in use over the iast 20 years. As currently used this material has disadvantages. In coir,r"on with other textiles it cannot be fGr",ed into a 3-dimensional shape that it will retain, so surgeons cannot place it precisely where they want it. It pe"et, ates the overlying gum in a high propol lion of cases bec~ ~se of its tendency to revert to its original flat shape and be~ ~se blood vessels cannot penetrate it. It will not support itself over a void and must therefore be suppo, led by an~tl ,er "~alerial placed on the bone. It must be removed after a few weeks.
Titanium foil and mesh have been tried as aller"dlives (Gay et al. Oral Health, May 1997 p 7-18). Both have successfully per",illed bone growth but foilshares e3tpanded polytetrafluoroetl ,ylene s ~ ru~,ensity to penet, ate the overlying gum and must be removed once the new bone has for",ed. Mesh however has none of the above-mentioned disadvantages and looks to be a useful material for ensuringthat osteoblasts can ",igrale to where they are wanted without having to win a race with faster-moving fibroblasts and epithelial cells. Titanium mesh is being embedded and left per",ane, Illy in place in people s jaws (and other parts of their bodies) during other types of surgery. Like titanium illlplsllls it does not provoke an infla",mdlory respGnse in these situations and is well-tolEraled by the surrounding tissue. Dr Joh Gay and his ~ssoci~tss in Toronto have used titanium mesh barriers to promote bony s infill with GTR. When doing re-entry surgery to remove the barriers they have noted absence of inflsmmalion inti",ale tissue adaptalion to the mesh and a considerable degree of difficulty in removing the mesh. They question whether it is really necess~ry to remove the titanium mesh barrier ",aterial which they and other su, geons do insert permanently when doing orthognathic surgery.
o Since titanium mesh can be left per",aner,lly in place in the body the integral barrier of the present invention is intended to be left in place after insertion making re-entry surgery to remove it Ul ,necessA~. Not only would retrieval of the mesh barrier be unnecessa"~ but uncovering the implant would be as well. It is intel Ide~l that the full-thickness flap elevated to e~l ~se the bony site for mesh barrier S placel"enl be sutured around not over the implant cover screw. The cover screw would guide the gingival tissue to heal around it so that it would be continuously visible. It would be painlessly removable and replaceable without local anaesthetic when the time came to attach a prosthesis to the implant.
Barrier-i",plsnt combinations would be useful not only in fresh 20 extraction sockets but also in toothless sites with insufficient bone volume. Using them bone augmentatiol" implant insertion and implant exposure could be accol"plished with only 2 surgeries 1 or 2 fewer than current techniques require.
The reduction is possible because the mesh barrier would not be removed. The combination would also make the operations easier and faster for the surgeon.
The range of dental sulyeGlls providing implant-barrier combinations immediately on e~l,a-1iGn of teeth would encG""~ass general dentists capable of the limited flap surgery required as well as periodonlis(s and oral surgeons. This range is wider than the range of simple implant providers and could potentially increase the number of patients who could benefit from the invention.

If priced cor, t:ctly, implant-barrier combinations would be found preferable to exl, a.;tion and bridging, complex root canal treatment and toothless spaces. By being low-cost, single-surgery, short-healing-time tooth replacements, implant-barrier combinations, besides being useful in themselves, would be apt to make the public more familiar with the benefits and relative ease of implants ingeneral, and would therefore be apt to increase the number of simple implants being placed in edentulous sites.

SUMMARY OF THE INVENTION
According to the invention, there is provided a dental implant-barrier combination comprising a root-form i""~lanl member of either screw-in or press-fit type, a barrier arranged to exclu~e soft tissue cells and joining means for connecting the barrier to the implant member.
The function of the inteyraled barrier is to make it possible for the implant portion of the implant-barrier co"~.n~lion to becG",e osseoinley, ated after having been i"se,led in a tooth socket i",r"e~ ely after removal of a tooth. It will do this by decreasing the likelihood of movement of the implant in the extraction site and by preventing unwanted cell types from e"teri,lg and proliferating in the socket.
The integrated barrier is to be left per")aner,lly in place, in conl,asl with other guided tissue regeneration barriers used to increase bone volume for implant insertion.
The dental implant-barrier combination, though most useful in fresh exl,a.;tion sockets, could also be used in edentulous areas to induce increased bone volume where bone height or width were inadequate to envelope the implant.
P,~rerably, the barrier is composed of titanium mesh, which possesses both biocompalibility and the malleability necess~fy to allow the barrier to be intimately adapted to the bony surface of the alveolar crest.
The barrier may be pre-formed in order for it to collrol ", to the shape of the bone of the maxillary or mandibular alveolar crest, tl ,erel,y reducing the amount of CA 02224332 l997-l2-lO

manipulation needed during the surgical procedure in which it is inserted.
The joining means may, for press-fit i",plal)ls, comprise welding, bonding with (for example) an epoxy a~l ,esive and press fitting into a groove the width of the thickness of the barrier. For screw-type implants, which must be rotated to be placed, s the joining means would co",p, ise, in addition, a titanium collar or ring which could rotate in a race or groove in the implant, and to which the barrier would be attached so that it could be kept from rotating as the implant was screwed into place.
The above-mentioned collar could be made with a break in its circu",rerence to allow it to be opened enough to be snapped into place in the groove 10 meant to accept it, or the implant could be made in two pieces, with the two being joined after collar and mesh were in place.
Ple~arably, the barrier-implant combination is pre-sterilized and packaged to remain so until removed from its package at the time of surgery.
Plererably, the barrier-implant coi,l~..,dtion includes a removable handle 15 in order for it to be manipulated without actually being touched.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a top view of an implant-barrier combination.
Figure 2 is a side view of a press-fit implant-barrier combination.
Figure 3 is an isGmet, ic view of a press-fit implant-barrier combination in a disposable sterile package.
Figure 4 is a schematic view of a press-fit implant-barrier combination i"se, led in an immediate extraction socket.
Figure 5 is a schematic view of a press-fit implant-barrier combination 25 inse, led in an osleotol"y (drilled out) site with In~de~u~te bone volume and the barrier contoured to permit bone growth to fully imbed the implant.
Figure 6 is a schematic view of an osseoi"le$~raled press-fit implant-barrier combination with an abutment and a prosthetic tooth allached.
Figure 7 is a side view of a screw-type implant-barrier combination.

Figure 8 is a side view of a press-fit implant-barrier combination in a disposabla sterile package.
In the drawings like characters of rererence indicate corresponding parts in the dirrere"t figures.
s DETAILED DESCRIPTION
Referring to the drawings an i",planl-barrier combination 10 is comprised of a root-form implant member 14, a barrier 12 and an implant cover screw 15.
The barrier 12 is ar,~"ged to stabllize the root-form implant member 14 and to act as a barrier to soft tissue cells, as described below. Specifically, the barrier 12 acts to exclude fibroblasts and epithelial cel!s from a tooth extraction socket 16. In this embodiment the barrier 12 is composed of titanium mesh specifically 100 x 100 mesh. It is of note that the titanium mesh is biocompdliL,le and malleable as described below.
s The implant member 14 of the implant-barrier combination 10 is arranged to be inse,led into tooth extraction socket 16 as described below. The details of the implant member 14 are not shown as these are~ known to persons knowled~e~hle in the art.
The dental implant-barrier combination 10 is assembled by connecting the barrier 12 to the implant ",ernber 14 such that the barrier 12 exle"Js outwardly from the i,nplanl ",e,nber 14 as shown in Figures 1-8. In this embodi.~ent the barrier 12 is bonded to the implant ,ner,lber 14 with an epoxy adhesive. Aller"alively the barrier 12 may be cor" lecteJ to the implant member 14 by other means for example by welding the barrier 12 to the implant member 14. It is of note that once assembled the dental 2S implant-barrier coi,lbi"dlion 10 may be sterilized and enclosed in sterile packaging 21 for later use as shown in Figures 3 and 8. This in turn will greatly reduce the risk of bacterial cont i",ination and surface conlar"ination of the titanium surfaces of the barrier 12 and implant member 14.
In an embodiment wherein the implant ~el~lber 14 with ll ,reads 28 is ar, anged to be screwed into the extraction socket 16 the barrier 12 is attached to a collar 24 which is a"anged to be fitted into a circ~""rere"lial groove 26 in the implant me",ber 14. The collar 24, together with the dtlached barrier 12 may rotate in the groove 26 freely about the implant member 14 or aller"~ ely may be stationary while the implant member 14 is rotated while being screwed into the extraction socket 16.
In another embodiment shown in Figure 8 the dental implant-barrier combi"alion 10 may include a removable handle 30 for aiding in manipulating the dental implant-barrier combination 10 during surgery.
In operation before tooth ext,actiGn the surgeon will evaluate the site o clinically and view its radiograph image to deten~ine whether the tooth is replaceable with an implant-barrier combination 10 and if so what implant member 14 size theimplant-barrier combination 10 should have and how to cut and shape the mesh barrier 12. The surgeon will elevate the gum 20 about the tooth remove the toothmechanically Jebride the socket 16 confir", or;modify implant-barrier combination 10 15 choice and cut and contour the mesh barrier 12. The barrier 12 is sufficiently malleable that the barrier 12 may be formed into the necess~ry shape either prior to surgery or during surgery as desired. Thus the barrier 12 may be readily manipulated so as to conror"~ to the desired shape a shape which it will retain. The surgeon will then insert the implant member 14 in the socket 16 and press the barrier 12 against the adjoining bone. The gum 20 will'be sutured in place over the barrier 12 and around the implant cover screw 15 the repositioned gum 20 holding the mesh barrier 12 firmly in place on the bone and the barrier 12 in turn helping to stabilize the implant member 14 by virtue of its rigid ~tlachl"ent to it. . As a result of the barrier 12 preventing migration of fibroblasts and epithelial cells into the extraction socket 16 25 osteoblasts populate the healing blood clot around the implant member 14 achieving osteointegration.
The barrier 12 is composed of titanium mesh is biocol"palil,le and causes little risk of infection as noted above. The titanium mesh will retain the desired shape and circulation can be established through it. Consequently it will not pen~trale the overlying gum 18 as polytetrafluoroethylene and titanium foil tend to do. As a result of its biocor"palibiliy, small risk of infection, shape retention and possibility of establis~""enl of circulation, the barrier 12 does not have to be removed in a subsequent surgical procedure.
s Once osteointegration has occurred, an abutment 17 and a prosthetic tooth 19 can be attached to the implant member 14.
Since various modifications can be made in my invention as herein described, and many apparer,lly widely dirrerenl elllbodilllel ,ls of the same made within the spirit and scope of the claims without departure from such spirit and scope, it is n intended that all matter contained in the acco,,,pa~)ying specification shall be i"lel,ureted as illustrative only and not in a limiting sense.

Claims

1. A dental implant-barrier combination comprising a root-form implant member of either screw-in or press-fit type, a barrier arranged to exclude soft tissue cells and joining means for connecting the barrier to the implant member.