Abstract:
A structural/biological implant and method of use. The implant being utilized as a single or multiple staged system that is designed to encourage new alveolar bone growth with or without the need to obtain autologous bone. The implant has an apical portion that is fastened into existing bone, with the remainder of the implant left outside of existing bone. The exposed portion of the implant may have an external shape or configuration with a variety of attached and/or integrally formed mechanical retention and stability elements. Osteotropic/angiotropic material may be associated with the implant to induce and or conduct new bone growth and possible vascularization, thus, rather than fitting the implant into the bone, the bone is grown integratively with the implant. The osteotropic/angiotropic materials may be simultaneously placed with the staged implant to provide consistent stabilization for the materials and to provide an immediately available surface for bone cell adhesion and growth. The invention thus allows implants to be used in location where the volume and/or shape of the bone would not be adequate for existing implant systems.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/478,705, filed Jun. 13, 2003, the content of which is incorporated by reference in their entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [[0002]]     This invention was made with Government support under Grant No. DE14187 awarded by the National Institute of Dental and Craniofacial Research. The Government has certain rights in the invention. 
     
    
     FIELD OF THE INVENTION  
       [0003]     This invention relates generally to a structural/biological implant and method for encouraging bone growth with or without use of graft materials which may include autogenous bone, autologous or engineered cells, mineralized materials, demineralized bone matrix, alginates, collagen materials, and articles useful therein.  
       BACKGROUND OF INVENTION  
       [0004]     Inadequate bone volume is a well recognized problem in the craniofacial and orthopedic fields. For example, ordinarily, a dental implant must be fit into an implant bed within existing bone and corresponding in shape to the implant. Standard implants have a cylindrical or slightly tapered shape in order to allow for a path of placement into bone with the close adaptation needed for stability and to encourage the selective re-population of the implant site with osteogenic potential cells versus being encapsulated within fibrous tissue. In a large proportion of clinical cases, there is inadequate bone height and/or width for the placement of standard endosseous dental implants.  
         [0005]     Dental implants to replace missing teeth are 90-95% successful in clinical practice, when placed under optimal conditions. These conditions include good systemic health of the patient and acceptable bone quality, acceptable bone volume and acceptable bone shape at the implant site. Unfortunately, bone resorbs after tooth loss. Due to this continued bone loss, a substantial segment of the population has insufficient bone volume to benefit from implant placement. Bone grafting is currently the standard method for increasing the height and width of the bone ridge, and thereby maxillofacial bone volume. Current bone graft methods include painful, invasive and sometimes hazardous or prolonged procedures generally requiring an extensive donor site at locations such as the rib, hip or leg bone or blocks of bone from the jaw.  
         [0006]     Tissue engineering methods to augment bone volume, in edentulous regions where standard implant placement is not possible, are under intense development. These methods involve the use of scaffolds, growth factors and cells with osteogenic potential. However, at present there are significant limitations to the dimensions (especially thickness) of material that can be implanted due to issues involving extra-cellular transport of metabolites and products; the lifetime and effective diffusion distance and presentation timing of signaling moieties; and the multitude of support functions provided by a properly distributed vasculature. Thus, for example, many tissue-engineered products are limited to thicknesses of two to three millimeters, likely an inadequate dimension to be clinically meaningful in one surgical step.  
       SUMMARY OF THE INVENTION  
       [0007]     Briefly stated, the invention in a preferred form is a structural/biological implant and a method of use thereof for encouraging bone growth around the implant for structural purposes, with or without the use of autologous bone grafts, cells and/or therapeutic agent delivery. The invention in some forms may also be used with autologous bone grafts.  
         [0008]     Another embodiment of the invention is a bone augmentation dental implant system used where existing jawbone levels are inadequate for the placement of standard dental implants.  
         [0009]     Generally, a portion of the implant is fastened into existing bone, with the remainder of the implant extending outside of existing bone. The extending or exposed portion of the implant has an osteointegrative surface which may include an external shape or configuration including at least one of a variety of attached and/or integrally formed mechanical retention and stability elements. New bone growth occurs around the exposed portion of the implant thereby increasing bone height and volume in the patient.  
         [0010]     Biologic materials which may be osteoinductive, osteoconductive, osteotropic and/or osteogenerative (herein referred to as osteotropic materials) may be used in conjunction with the implant to induce, promote, or enhance new bone growth around the exposed portion of the implant.  
         [0011]     Vascular augmentation and/or enhancement may be achieved through use of angiogenic materials such as chemical agents, proteins and nucleic acids encoding growth factors herein referred to as angiotropic materials. These osteotropic/angiotropic materials include, but are not limited to, conductive and/or inductive scaffolds that support and direct regeneration of bone or vascular endothelium and often may additionally incorporate, growth factors, and progenitor cells. The osteotropic/angiotropic material provides an immediately available surface for bone cell adhesion and growth. Further, these materials may be paired with appropriate osteoinductive factors to provide environmental conditions that advance osteogenesis.  
         [0012]     Thus, rather than fitting the implant into existing bone volume, new bone volume and supporting vasculature, is grown into and around exposed portions of the implant providing a positionally stable and biologically integrated implant. Consistent positional retention and stabilization of the osteotropic/angiotropic material by the implant structure can also be achieved through the close adaptation of the osteotropic/angiotropic material to the implant structure. The implant is amenable to use with tissue engineering techniques. For example, this includes the transplantation of undifferentiated stem cells, progenitor cells for bone or cartilage, or differentiated cells into scaffold materials. This may also include transfection vector therapy to induce growth factor expression from local cells or cells sequestered into or transplanted into scaffold materials at the site of the osseous deficiency.  
         [0013]     The invention allows implants to be used in locations where bone height and/or bone shape is not adequate for existing implant systems. For example, conventional implants typically require ten to twelve millimeters of bone height. However, only four to six millimeters of height are required by the inventive implant at the beginning of treatment. During treatment an additional two to six millimeters of bone can be grown around the implant in one or more surgical procedures.  
         [0014]     Portions of the implant can be made from resorbable or non-resorbable materials, and can be shaped or configured to optimally achieve positional stability since bone is grown integrally with the implant. The resorbable and/or non-resorbable endosseous dental implant may also be utilized with tissue engineered materials used with reduced bone levels and/or to enable segmental osteogenesis.  
         [0015]     In general, the material of the invention may be alternately formulated to comprise, consist of, or consist essentially of, any appropriate components herein disclosed. The material of the invention may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants or species used in the prior art compositions or that are otherwise not necessary to the achievement of the function and/or objectives of the present invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     Other objects and advantages of the invention will be evident to one of ordinary skill in the art from the following detailed description with reference to the accompanying drawings, in which:  
         [0017]      FIG. 1A  is an exploded view illustrating various components of one embodiment of the inventive staged implant system.  
         [0018]      FIG. 1B  is a perspective view of one embodiment of the inventive staged implant system.  
         [0019]      FIGS. 2A-2G  are perspective views illustrating examples of some inventive embodiments of stage I and stage II implant system assemblies.  
         [0020]      FIGS. 3A-3C  are perspective views illustrating examples of some inventive staged implants with osteotropic/angiogenic materials embedded in bone during a stage I surgery process.  
         [0021]      FIGS. 4A-4C  are perspective views illustrating examples of some inventive staged implants with osteotropic/angiogenic materials embedded in bone during stage II surgery process.  
         [0022]      FIGS. 5A-5C  are side views illustrating examples of one embodiment of the inventive staged implant consistent with the present invention.  
         [0023]      FIG. 5D  is a side view of one embodiment of the inventive osteointegrative portion consistent with the present invention.  
         [0024]      FIG. 6A  is a side view of an embodiment of the inventive assembled stage I implant.  
         [0025]      FIG. 6B  is a top view of the inventive embodiment  6 A.  
         [0026]      FIG. 6C  is a side view of a portion of an embodiment of the inventive assembled stage II implant.  
         [0027]      FIG. 6D  is a side view of an embodiment of the inventive stage I assembly implant.  
         [0028]      FIG. 6E  is a side view of a portion of an embodiment of the inventive assembled stage II implant.  
         [0029]      FIG. 7A  is a side view of inventive trans-implant elements used with two stage I implants.  
         [0030]      FIG. 7B  is a top view of the inventive element of  FIG. 7A .  
         [0031]      FIG. 7C  is a side view of inventive trans-implant elements used with two stage II implants.  
         [0032]      FIG. 7D  is a top view of the inventive element of  FIG. 7C .  
         [0033]      FIG. 8A  is a side view of one embodiment of an inventive staged implant.  
         [0034]      FIG. 8B  is a top view of the inventive staged implant of  FIG. 8A . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]     The implant in one embodiment of the invention as illustratively shown in  FIG. 1  has a central axis (not shown) extending between a coronal end  10  and an apical end  12 . The implant includes a level I assembly  10  having an initial implant portion  16  with an anchor portion  18 . The anchor portion  18  may be substantially axially symmetric to the central axis. The anchor portion  18  has an exterior surface. In one embodiment the anchor portion  18  exterior surface has fastening means such as screw threads  20  helically disposed thereon. The threads advantageously have a minimal spacing, for example, less than 1 mm, and are self-tapping for optimal engagement and adaptation to existing alveolar bone. Other fastening means may be disposed on the anchor portion  18  exterior surface to help secure the anchor portion  18  to existing bone. The anchor portion  18  may for example be between about 3 mm and about 6 mm in length. The initial implant portion  16  may also have a transmucosal portion  22  being about 2 mm in length. The transmucosal portion  22  may be integrally formed with the initial implant portion  16  or may be a discrete part separable from the initial implant portion  16 .  
         [0036]     The transmucosal portion  22  may, as illustratively shown in  FIG. 1 , have a connecting surface such as a threaded bore  26 . The walls of the bore may define a slot  28  or other tool engagement surface well known in the art.  
         [0037]     In another embodiment of the invention illustratively shown in  FIG. 6D , the transmucosal portion of the initial implant portion  16  may have a polished collar  24 . The polished collar may be approximately 2 mm in axial length, terminating with a finish line  25 . The finish line  25  may be, for instance, angled relative to the central axis extending between the coronal end  10  and the apical end  12 .  
         [0038]     In some embodiments it is desirable to have a separate transmucosal portion. For example, when multiple stages are to be employed, the initial structural implant has a separate transmucosal portion (not shown) and may or may not include the polished collar.  
         [0039]     The transmucosal portion need not be axially symmetric to the central axis. In some embodiments of the invention (not shown) the transmucosal portion may have a cross-sectional shape designed to provide esthetic, biologic or further mechanical advantages. Such asymmetric shape may, for instance, be in a tooth root form, which would provide esthetic value, or mechanical stability of a prosthetic feature.  
         [0040]     An osteointegrative portion  30  of the implant is disposed apical to the transmucosal portion  22 . The transmucosal portion  22  and the osteointegrative portion  30  may be configured and/or adapted to aid in the installation and positioning of osteotropic/angiotropic material  32 . For example, the transmucosal  22  and osteointegrative  32  portions may have a shape which is complementary to an opening in the osteotropic/angiotropic material  32  to aid in the alignment and passage of the osteotropic/angiotropic material  32  over the transmucosal portion  22  and the osteointegrative portion  30 .  
         [0041]     With reference to  FIG. 1 , the initial implant portion  16  has an osteointegrative portion  30 , which, for example, is about 2 mm in length. The dimension and position of the osteointegrative portion  30  should be understood to be variable depending on osteointegrative potential of the site. The osteointegrative potential may vary depending on, for example, the type(s) of osteotropic/angiotropic material  32  associated with the implant and the location, morphology and physiology of the implant site. The osteointegrative portion  30  is typically located between the transmucosal portion  22  and the anchor portion  18 . However, the osteointegrative portion  30  may be located in other locations. For example, the osteointegrative portion  30  may be located at the apical end  12  of the initial insert portion  16 . It should also be understood that there may be a plurality of osteointegrative portions present on the implant (not shown).  
         [0042]     The osteointegrative portion in any of the embodiments may have, for example, a surface which is bioactive and designed to promote rapid osteointegration or closely adapted new bone growth while being configured to achieve increased stability and retention to the newly grown bone. Bioactivity of the surface may be achieved through, for example, modifying the chemical surface properties of the osteointegrative portion. For example, calcium phosphate may be used to coat the surface of the osteointegrative portion.  
         [0043]     The external shape of osteointegrative portion  30  does not need to be axially symmetric relative to the central axis. The osteointegrative portion  30  may, for example, have any number of projections, undulations, cavities, etchings, and/or other such features designed to resist axial tipping, or torsional loads and/or provide enhanced osteointegration. The osteointegrative portion  30  can be shaped or configured in part to achieve increased retention and stability characteristics for a given osteointegrative portion  30  length. For example, the use of a reverse taper shape (not shown) in which the osteointegrative portion increases in diameter from the coronal end  10  toward the apical end  12  operates to wedge the implant within the newly formed bone. The osteointegrative portion  30  may also have protrusions (not shown) which operate to stabilize the implant as bone forms around the protrusions.  
         [0044]     The osteointegrative portion  29  may be configured in whole or part to increase positional stability of the implant by providing mechanical support as bone grows around the configured area. For example the osteointegrative portion  29  may have an ovate shape  42  as shown in  FIG. 5A  or an undercut shape  44  as shown in  FIG. 5D .  
         [0045]     The osteointegrative portion may also incorporate a resorbable or a non-resorbable porous surface capable of uptake and sustained release of endogenous or exogenous macromolecules associated with the differentiation and proliferation of precursor cells to become osteoblasts and stimulate osseous formation. For example, this surface may be used as a carrier for drugs, proteins or genetic material. In one embodiment of the invention, this surface of the osteointegrative portion may carry drugs or biomolecules that elicit endochondral bone formation as a prelude to cortical bone formation directly adjacent to the implant site.  
         [0046]     An extender  34  may also be present that removably attaches to the coronal end  10 . The extender may, for example, have threads disposed to allow engagement with the threaded bore  26 . The attached extender  34  axially extends in the coronal direction to allow osteotropic/angiotropic material  32  to be engaged with the extender  34 . This engagement allows precise and controlled positioning of the osteotropic/angiotropic material  32  over the transmucosal portion  22  and osteointegrative portion  30  in a surgical environment.  
         [0047]     A preliminary stabilizer  36  may be present which extends laterally outwardly from the outermost surface of the anchor portion  18 . For example, the preliminary stabilizer  36  may extend outwardly about 2 mm. The preliminary stabilizer comes into contact with, for example, a countersunk area in the prepared bone surrounding the embedded anchor portion  18 . The preliminary stabilizer  36  may act to provide lateral stability to the implant as well as retentive stability after formation of new bone around the preliminary stabilizer  36 .  
         [0048]     In one embodiment of the invention, the preliminary stabilizer  36  is a separable part that may not be present when the anchor portion  18  is embedded to a sufficient depth in bone, for example to about 4 mm to about 6 mm. In this embodiment the preliminary stabilizer  36  has a central opening  38  which may be internally threaded. The central opening  38  may be threaded onto the portion of the initial implant, which, for example, extends above the bone. The preliminary stabilizer  36  may be secured against the bone by a preliminary stabilizer nut  40 .  
         [0049]     In another embodiment of the invention, illustratively shown in  FIGS. 5A , and  6 A, the preliminary stabilizer  35  is an integral part of the initial insert portion  16 . In this embodiment the preliminary stabilizer  35  is permanently attached to, or formed with, the initial insert portion  16 . The preliminary stabilizer  35 , in use, comes into contact with the bone as the implant embeds.  
         [0050]     The preliminary stabilizer may also be fixed to the implant in a manner that allows rotation of the preliminary stabilizer about the initial implant portion  16 . For example, there may be a circumferential groove (not shown) formed in the initial implant portion  16  into which a lip (not shown) of the preliminary stabilizer  35  engages, such that the preliminary stabilizer  35  is fixed axially but can rotate about the initial implant portion  16 .  
         [0051]     In one embodiment of the invention, a second stabilizer, termed an osteotropic/angiotropic material stabilizer  46 , shown in  FIG. 1 , may be attached to the structural implant. In other embodiments the osteotropic/angiotropic material stabilizer  47 , as illustratively shown in  FIGS. 8A and 8B  may have a curved or arcuate planar form having one or more cutouts  50  and/or protrusions (not shown). These cutouts  50  provide enhanced stabilization, cell population, and/or vascularization of the biologic material. The osteotropic/angiotropic material stabilizer  46  may have a threaded opening  52 , illustratively shown in  FIG. 1 , to engage, for example, threads on initial implant portion  16 .  
         [0052]     The osteotropic/angiotropic material stabilizer  46  may be positioned on the coronal end  10  of the initial implant portion  16 , as illustratively shown in  FIG. 2D , and be secured in place with a stage I cover screw  54  that engages with a connecting surface such as bore  26 . Alternatively, the osteotropic/angiotropic material stabilizer may be formed integral with the cover screw (not shown) such that the stabilizer extends laterally outwardly from a portion of the cover screw. For example, the head of the cover screw may have a portion that extends radially outwardly about a central axis.  
         [0053]     In any embodiment the osteotropic/angiotropic material stabilizer may be formed of any suitable material known in the implant arts, including resorbable organic and/or inorganic materials, or non-resorbable materials such as metal and ceramic.  
         [0054]     As shown in  FIG. 1  the osteotropic/angiotropic material stabilizer  46  may be disposed with osteotropic/angiotropic material  32  on the initial implant portion  16  in order to further prevent any potential movement of the osteotropic/angiotropic material  32 . The osteotropic/angiotropic material  32  is prevented from moving by, for example, the osteotropic/angiotropic material stabilizer  46  exerting pressure on the osteotropic/angiotropic material  32  such that the osteotropic/angiotropic material  32  is held against the preliminary stabilizer  36  and/or the bone. In one embodiment of the invention, illustratively shown in  FIG. 6B , the osteotropic/angiotropic material stabilizer  45  has a plurality of openings, each  56 . The openings  56  allow vascular in-growth to the area of bone growth to occur therethrough. The openings  56  may also aid in retaining the osteotropic/angiotropic material by, for example, allowing portions of the osteotropic/angiotropic material to protrude into the openings  56  when the osteotropic/angiotropic material stabilizer  45  exerts pressure on the osteotropic/angiotropic material.  
         [0055]     With reference to  FIG. 3C , the osteotropic/angiotropic material stabilizer  46  and/or osteotropic/angiotropic material  37  may also support the mucoperiosteal flaps present around the implant site (not shown). The mucoperiosteal flaps can be used to cover the implants at the conclusion of the surgical procedure placing the implant. In the event that insufficient tissue is present due to the volume occupied by the implant periosteal releasing incisions; a split flap or a soft tissue graft may be used to cover the implant.  
         [0056]     Osteotropic/angiotropic material in any of the embodiments may comprise those materials known as scaffold matrices made from a variety of materials well known in the medical art. Examples of such materials include autogenous bone, bone allograft, synthetic polymers, natural polymers, ceramics, and/or composite materials. These materials generally provide surfaces and conduits which are utilized by osteoblast lineage cells and osteoblasts. In addition, the osteotropic/angiotropic material may allow for such things as retention, stabilization, controlled release, and/or other bioavailability modulation of osteoactive compounds and/or products. For example, the osteotropic/angiotropic material may include resorbable collagen sponges soaked with recombinant human bone morphogenetic protein (rhBMP) and/or VEGF (for vascular potentiation) which may be either covered or uncovered with a non-resorbable barrier membrane  58 , as show in  FIG. 3B . The membrane  58  may act, among other things, as a barrier to the in-growth of epithelial cells and connective tissue fibroblasts. Suitable barrier membrane  58  materials include polytetrafluoroethylene and collagen. It should be understood that the osteotropic/angiotropic material may also have the form and rigidity to aid in stabilization of the implants. For example, the use of osteotropic/angiotropic materials such as polymers, ceramics, composites, cements, autogenous bone, bone allograft, or other rigid material, may add mechanical support to the implants.  
         [0057]     The initial implant portion  16 , as shown in  FIG. 3B , may be used alone or as part of a plurality of adjacent implants, and may incorporate, secure, and/or stabilize such things as the osteotropic/angiotropic material  37 . As illustratively shown in  FIGS. 7A-7D , stabilization may be aided by trans-implant elements such as mesh  60 , or plate  62 . The trans-implant elements such as mesh  60  and plate  62  may provide mechanical stability to the implants. In addition, osteotropic/angiotropic material (not shown in  FIG. 7 ) may be associated with the mesh  60  and/or plate  62  such that the trans-implant elements provide stability and retention of the osteotropic/angiotropic material through mechanical interaction to the osteotropic/angiotropic material.  
         [0058]     As illustratively shown in  FIG. 2D , an osteotropic/angiotropic stabilizer cover screw  54  may be fixed to the implant through engagement of the cover screw threads with the threaded bore  26  of the initial insert  16  to form a stage I assembly  14 .  
         [0059]     In one embodiment of the invention, shown in  FIG. 2G , a stage II assembly  64  may be utilized if, for example, additional bone growth over that available from a stage I assembly is required. It should be understood that more than one additional stage assembly may be utilized if additional bone growth is required. The stage II assembly  64  replaces the cover screw  54  as illustrated in  FIGS. 2F and 2G .  
         [0060]     The stage II assembly  64 , as shown in  FIG. 1A , includes an engagement portion  66 , and a body portion  70 . The stage II assembly  64  also includes an osteointegrative portion  33  which may, as previously discussed, be a resorbable or non-resorbable porous surface material capable of, for example, uptake, release, and sustained release of endogenous or exogenous macromolecules, such as drugs, proteins and genetic material, associated with the differentiation and proliferation of vascular cells or precursor cells to become osteoblasts and stimulate osseous formation.  
         [0061]     In another embodiment of the invention, as shown in  FIGS. 5B , the stage II assembly  65  may have an osteointegrative portion  31  with a shape, configuration or other features that allow for optimal integration and physical stability of the implant with the bone during bone growth, in a manner discussed above with regard to the osteointegrative portion.  
         [0062]     The osteotropic/angiotropic material stabilizer  46 , as shown in  FIG. 1  may in some cases be removed and replaced with an osteotropic/angiotropic material stabilizer  45  similar to the one shown in  FIG. 6B . The osteotropic/angiotropic material stabilizer  45  has several openings, each  56 . As previously discussed these openings  56  may increase the stabilization of additional osteotropic/angiotropic material to permit vascular ingrowth and/or serve as a region through which bone may form.  
         [0063]     The stage II assembly  64 , as shown in  FIG. 2F , may have, for example, a threaded bore  72  on the coronal end  74  of the stage II assembly into which a stage II cover screw  76 , shown in  FIG. 2G , may be threaded. The stage II assembly  64  also has a tool engagement surface such as a slot  78  to allow attachment of the stage II assembly  64  to the stage I assembly  14 .  
         [0064]     The coronal end  74  of the stage II assembly  65 , as shown in  FIGS. 5A and 5B  may have a polished collar  80 , and an angled finish line  82 . The angled finish line  82  has properties similar to those discussed with regard to angled finish line  25 .  
         [0065]     A stage II osteotropic/angiotropic material stabilizer  68 , as illustratively shown in  FIGS. 1B, 2G  and  4 C may be present in the stage II assembly  64 . The stage II osteotropic/angiotropic material stabilizer  68  may have a generally planar shape and be comprised of a material that lessens and/or prevents cellular adhesion. The stage II osteotropic/angiotropic material stabilizer  68  has an opening  84 , illustratively shown in  FIG. 1A . The stage II osteotropic/angiotropic material stabilizer  68  may be retained to the coronal end  74  of the stage II assembly  64  by a stage II cover screw  76  that is engaged within the threaded bore  72 . Alternatively, as shown in  FIGS. 6C and 6D , the stage II osteotropic/angiotropic material stabilizer  68  may be integral with the cover screw.  
         [0066]     In another embodiment of the invention, as illustratively shown in  FIG. 6C , the stage II osteotropic/angiotropic material stabilizer  69  may fit over and around the polished collar  82  of coronal end  74 . Additional osteotropic/angiotropic material (not shown) may be placed in association with stage II assembly  65  and retained in place by the stage II osteotropic/angiotropic material stabilizer  69  in a manner similar to that shown in  FIG. 4C  where additional osteotropic/angiotropic material  39  is placed in association with stage II assembly  64  and retained in place by stage II osteotropic/angiotropic material stabilizer  68 , to further enhance bone growth.  
         [0067]     In another embodiment, for example as shown in  FIGS. 3C and 4C , multiple stage I and/or stage II implant assemblies are utilized adjacent to one another. In this embodiment additional bracing or splinting elements, similar to those shown in  FIG. 7  may be attached from one implant to the next implant to stabilize or further support the implants. This bracing provides added positional stability for the adjacent implants and/or osteotropic/angiotropic material securement.  
         [0068]     The material used for the stage I assembly and the stage II assembly is chosen for with respect to known biocompatibility as implant material and is guided by well-known principals of osseointegration, implant design, and characterization of biomechanical properties. As an illustrative example, materials such as titanium, titanium alloys, steel, steel alloys, cobalt alloys, nickel alloys, metal composites, ceramics, glasses, biologically derived materials, natural polymers and synthetic polymers may be used alone or in combination throughout the invention. Furthermore, the structural implant and components can be made from any of the resorbable and/or non-resorbable materials well known in the art. When the components are made predominantly from a non-resorbable material such as titanium or titanium alloy, the structural implant would remain in place for prosthetic restoration.  
         [0069]     The present invention encompasses a method of promoting the growth of new bone tissue with or without the use of autogenous or non-autogenous graft materials. In one embodiment, with illustrative reference to  FIGS. 2A-2G  and  3 A- 3 C, a section of bone (not shown in  FIGS. 2A-2G ) is surgically exposed or accessed and the anchoring component  18  is fastened into the bone to the level of the preliminary stabilizer  36  by engaging a tool (not shown) with the tool engagement surface  28 . The implant may then be fastened, for example, to a depth of about 4 mm to about 6 mm into the bone. This depth, it should be understood, may be based on the location of the preliminary stabilizer  35  if fixed to the initial implant portion  16  or on the location where a separate preliminary stabilizer  36  will be placed. A preliminary stabilizer  36 , if a separate component, may then be placed over the exposed portion of the initial implant portion  16 . During placement the preliminary stabilizer  16  may be threaded onto, or may pass freely over, the exposed portion of the implant. The preliminary stabilizer  36  may then be secured against the bone by tightening the preliminary stabilizer nut  40 . Osteotropic/angiotropic material  32  may then be placed over the implant. The osteotropic/angiotropic material  32  may also be punched through with the transmucosal portion  22  of the implant, or otherwise associated with the implant. The osteotropic/angiotropic material  32  is then secured in place with an osteotropic/angiotropic material stabilizer  46 .  
         [0070]     Where bone augmentation is desired over a greater area, multiple implants may be used.  FIG. 3  illustrates the use of multiple implants with osteotropic/angiotropic materials during a stage I surgery. Naturally more than two implants may be used in combination. When multiple implants are used, the implants are secured into bone adjacent to one another. This allows new bone growth to be obtained in any number of configurations. For example, the implants may be arranged in a substantially linear pattern or over a circular, or otherwise shaped, area.  
         [0071]     As illustratively shown in  FIG. 3B , osteotropic/angiotropic material  37  may be associated with multiple stage I assemblies  14 . For example, the osteotropic/angiotropic material  37  forms an extended structure which can be installed over the coronal ends  10 . The osteotropic/angiotropic material  37  may then be secured in place, as shown in  FIG. 3C , when the osteotropic/angiotropic material stabilizer  46  and is secured with the closure screw  54  fastened into the coronal end  10  of the implant. In the case of a stage II assembly  64  as shown in  FIG. 4B  osteotropic/angiotropic material  39  may be placed over the coronal ends  74  of two or more stage II assemblies. As shown in  FIG. 4C  the osteotropic/angiotropic  39  material may then be secured in place with the osteotropic/angiotropic material stabilizers  68  and secured with closure screws  76  fastened into the coronal end  51  of the implant. Placement of the osteotropic/angiotropic material  37  and/or osteotropic/angiotropic material  39  between multiple implants, as discussed above, may increase retention and stabilization of the osteotropic/angiotropic material. For example, the osteotropic/angiotropic material may be supported and retained physically at each end by the inserts.  
         [0072]     In another embodiment of the invention, as illustratively shown in  FIGS. 7A-7D  bracing or splinting materials, such as mesh  60  and plate  62  can be associated with the multiple implants. This additional bracing or splinting may connect the implants to further stabilize or support the implants in the bone. This bracing also may function to provide additional positional stability for the osteotropic/angiotropic material (not shown). The implant structure and associated osteotropic/angiotropic material may then be covered with a membrane, similar to membrane  58  as previously discussed with regard to  FIG. 3B , that acts as a barrier to the in-growth of epithelial cells and connective tissue fibroblasts into the osteotropic/angiotropic material.  
         [0073]     The implant site is then closed with, for example, a primary flap closure using techniques well known in the surgical arts. For instance, in the event that insufficient tissue is present to close the implant site, special surgical techniques previously described or additional material may be used. Such additional material can be any material well known in the medical art including autologous, allologous and/or engineered tissue grafts, natural and/or fabrics, and polymers.  
         [0074]     The quantity and quality of bone growth at the implant site is determined after a period of time. This determination may be accomplished either remotely via radiograph or Dual Energy X-ray Absorptiometry (DEXA) scan or through direct observation.  
         [0075]     With reference to  FIG. 3C , after three to six months the site can be reopened and cover screw  54  and osteotropic/angiotropic material stabilizer  46  removed. The bone is then observed and the bone growth is determined. If bone growth is adequate, a transmucosal prosthetic segment (not shown) may then be attached to the implant. The prosthetic connector attachment may utilize, for example, adhesive bonding or mechanical attachment such as on screw-retained abutments well known in the medical arts.  
         [0076]     If additional bone is needed, an additional stage, for example, a stage II assembly  64  is fastened, as shown in  FIG. 1 , with the engagement portion  66  to the connecting portion, such as threaded bore  26  of the initial implant portion  16 . This fastening can be aided through engagement of a tool (not shown) with the tool engagement surface  78 .  FIGS. 4A-4C  illustratively show progressive installation of stage II assemblies (each  64 ) to implanted stage I assemblies (each  14 ) as well as the incorporation of osteotropic/angiotropic material  37  and osteotropic/angiotropic material  39 . After stage II assembly  64  placement and maturation of new calcified tissues around the stage II assembly, the assembled implant composed of the stage I assembly  14  and the stage II assembly  64  may be supported and retained by, for example, approximately 8 mm or more of bone height and be ready for the attachment of the prosthetic segment (not shown).  
         [0077]     Experimental use of one embodiment of the invention included use of the osteotropic/angiotropic material in the form of a bone allograft scaffold. The osteotropic/angiotropic material was used in conjunction with an implant having an osteointegrative portion with a roughened titanium surface, an implant having an osteointegrative portion with an alkaline surface, and an implant having an osteointegrative portion with a calcium phosphate surface. Vertical bone growth was achieved in a range of between 1.67 mm to 2.29 mm for the implant with a roughened titanium surface; in a range of between 1.79 mm to 2.15 mm for the implant with the alkaline surface; and in a range of between 2.09 mm to 2.89 mm for the implant with the calcium phosphate surface.  
         [0078]     It should be understood that while preferred embodiments of the foregoing invention have been set forth for purposes of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations and alternatives may occur to one skilled in the art without departing from the spirit and scope of the present invention.