Abstract:
There are provided systems, methods and apparatuses related to bone augmentation shells. In particular, in accordance with an aspect, there is disclosed an apparatus for bone augmentation. The apparatus includes a biocompatible body being shaped to fit over basal supporting bone structure. The body has an interior surface defining a cavity into which bone growth material may be inserted. Additionally, the body includes a rib portion located at an apex of the body, a first surface extending downward on a first side from the rib portion and a second surface extending downward on a second side from the rib portion. At least a portion of the first and second surfaces is roughened to have a micro-topography conducive to soft tissue attachment.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is related to and claims priority to U.S. Provisional Patent Application No. 61/178,040, filed on May 13, 2009, entitled “Rapid Prototype Titanium Shell,” the contents of which are hereby incorporated by reference herein in their entirety. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    Aspects of the present disclosure relate generally to biocompatible shells for bone treatment and, more specifically, to methods for manufacturing biocompatible shells and techniques for implementing biocompatible shells as a bone graft strategy. 
         [0004]    2. Background Discussion 
         [0005]    Bones are the basic structural unit of the human body. Among other things, they provide protection for organs and support the weight of the body. Bone strength and size maybe negatively impacted by disease, trauma, and/or atrophy. With respect to the jaw bone, any reduction in size and strength may result in tooth loss as well as possible reduction in the size of the basal supporting bone which forms the basic dental skeletal structure. 
         [0006]    There is a need in the art for improved bone treatment techniques and apparatuses that may be implemented with high precision to allow for bone regeneration and augmentation. In particular, there is a need for an integrated bone augmentation and dental implant strategy that allows for secure and precise positioning of dental implants. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a flowchart for creating a biocompatible shell for bone growth. 
           [0008]      FIG. 2  is a block diagram of a system for creating biocompatible shells. 
           [0009]      FIGS. 3A and 3B  illustrate stereolithographic modeling of a jaw bone and shell, respectively. 
           [0010]      FIG. 4  illustrates a cross-sectional view of a biocompatible shell. 
           [0011]      FIG. 5  illustrates a side view of the biocompatible shell installed on the jaw bone. 
           [0012]      FIG. 6  illustrates a longitudinal cross-sectional view of the installed biocompatible shell with dental implants. 
           [0013]      FIG. 7  illustrates a top view of the installed biocompatible shell. 
           [0014]      FIG. 8  illustrates a cross-sectional view of the installed biocompatible shell taken along line AA of  FIG. 7 . 
           [0015]      FIG. 9  illustrates a perspective cross-sectional view of a segment of the installed implant taken along line BB of  FIG. 7 . 
           [0016]      FIG. 10  is a flowchart illustrating steps for installing the biocompatible shell of  FIGS. 4-8 . 
       
    
    
     SUMMARY 
       [0017]    In accordance with an aspect of the disclosure an apparatus for bone augmentation is provided. The apparatus includes a biocompatible body being shaped to fit over basal supporting bone structure. The body has an interior surface defining a cavity into which bone growth material may be inserted. Additionally, the body includes a rib portion located at an apex of the body, a first surface extending downward on a first side from the rib portion and a second surface extending downward on a second side from the rib portion. In some embodiments, at least a portion of the first and second surfaces is provided with a micro-topography conducive to soft tissue attachment. 
         [0018]    In accordance with another aspect of the disclosure a method for manufacturing a biocompatible shell is provided. The method includes determining a bone structure to which the biocompatible shell will be attached and designing the biocompatible shell based on the determined bone structure using a computer graphics program. Additionally, the method includes creating the biocompatible shell from the design by providing computer readable data to a shell generation device and roughening an outer surface of the shell. 
         [0019]    In accordance with yet another aspect of the disclosure a rapid prototype shell assembly for bone augmentation and dental implant placement is provided. The shell includes a shell body having a generally arcuate cross-sectional shape. The shell body includes a rib portion located at an apex of the body and lingual and labial surfaces extending from the rib portion to form a cavity. 
       DETAILED DESCRIPTION 
       [0020]    Generally, there is disclosed an apparatus and method for bone graft strategy implementing biocompatible shells (also referred to as “bone forms”) that provide a structure and form for bone growth. In particular, embodiments set forth herein generally include a printable (e.g., rapid prototype) biocompatible shell that provides structure and shape for bone augmentation where bone has been resorbed, damaged, or atrophied. In some embodiments, the biocompatible shell may be implemented as a titanium shell, a titanium alloy shell, a titanium mesh shell, a titanium alloy mesh shell, a shell made of resorbable material such as a polylactate, or other shell of suitable material. In some embodiments, the biocompatible shell may be made of a titanium mesh or titanium alloy mesh formed mechanically or by hand into a desired shape and utilized in the same manner as the printed shell. 
         [0021]    In some embodiments, a combined bone graft-dental implant strategy implements a biocompatible shell and dental implants. For a combined graft-implant strategy, the biocompatible shell may be based on stereolithographic designed alveolar jaw bone augmentation and includes fastening capacity for high profile dental implant placement. Bone Morphogenetic Protein-2 (or bone graft) may be implemented to provide a bone structure within the shell to secure the dental implants and allow for eventual removal of the biocompatible shell. 
         [0022]    In some embodiments, computer assisted design (CAD) technology is employed to fabricate the biocompatible shell and/or the dental implants. Additionally, CAD technology may be used for creation of physical models for use in model surgery. Specifically, models of existing bone, a biocompatible shell, and implants may be created directly from computer aided drafting (CAD) source data. The models and the biocompatible shell may be fabricated in a suitable method, such as a printable method by adding material in layers. 
         [0023]    Rapid prototyping is a common name given to a host of related technologies that are used to fabricate physical objects directly from CAD data sources. The rapid prototyping methods add and bond materials in layers to form objects such as the biocompatible shells. Such methods may also be referred to as additive fabrication, three dimensional printing, solid freeform fabrication and layered manufacturing. Stereolithography is the most widely used method of rapid prototyping technology and may be used in the production of anatomic models that are useful for tactile hands on treatment planning for alveolar surgical modification of edentulous sites for dental implants. As used herein, reference to stereolithography, printing, rapid prototyping, or the like, should be understood to include any of the class of printable techniques and use of such terms is not intended to be exclusive. Further, it should be appreciated that other techniques may be implemented to create the models and/or shells and dental implants. For example, in some embodiments, a milling technique, such as computer numerical controlled (CNC) milling, may be implemented. Additionally, in some embodiments, the shell may be mechanically and/or manually formed with titanium or titanium alloy mesh. 
         [0024]    In some embodiments, a titanium shell made via stereolithography to shape bone augmentation is implemented. When surgically placed, the shell guides and secures dental implants into appropriate positions. Design and placement planning of both the shell and the implants may be performed in a graphical computer environment and may be based on radiographic images of existing bone. Hence, graphical computer planning software and print technologies such as stereolithography are implemented to fabricate the titanium shell to prescribed dimensions. 
         [0025]    The shell may be secured to the existing bone by trans-osseous fastening screws. Bone Morphogenetic Protein (BMP) or bone graft material is injected into an interior space of the shell to fill the augmentation requirement. Dental implants are also installed into the shell. Surgical application of dental implants, placed in high profile are secured by the biocompatible shell at a rigid spine that has specific perforating holes (at the alveolar crest) through which cover screws pass to secure the implants. Following a bone-healing period (e.g., six months time), the titanium shell is removed and bone and osseo-integrated implants remain. To prevent dehiscence, the titanium shell may be laser etched on an outer surface to promote soft tissue attachment. 
         [0026]    Turning to the figures and referring initially to  FIG. 1 , a flow chart illustrating a method  100  of manufacturing a titanium shell that may function as a bone graft mold and as a dental implant stent is illustrated. The method  100  includes obtaining a radiographic image of bone that has been damaged, deteriorated, or otherwise will be constructed or re-constructed (Block  102 ). In some embodiments, a CT scan is taken of bone that has been damaged and/or resorbed. For example, a CT scan image of a damaged or demineralized jaw bone may be taken if reconstruction of jaw bone and placement of dental implants are desired. 
         [0027]    The radiographic image is used to determine the contours of the existing bone structure (Block  104 ). In some embodiments, the determination of contours may be automated (i.e., computer software evaluates the radiographic image and determines the dimensions of the existing bone). In other embodiments, a user may determine the contours of the existing bone based on viewing the radiographic image. A biocompatible shell is designed to fit the existing bone (Block  106 ). Specifically, using computer software and the radiographic image, a user may design the shape of the biocompatible shell to achieve a desired amount of bone augmentation and/or to sufficiently secure dental implants. A doctor, such as an orthopedic surgeon or a maxillofacial surgeon, may design the biocompatible shell using the computer software. In other embodiments, a technician may design the biocompatible shell under supervision of a doctor. In some embodiments, the designing of the biocompatible shell may be automated or semi-automated. That is, software may be provided that determines the shape of the existing bone and provides a suggested shell design. A user may then fine-tune the shape and design of the suggested shell design. In some embodiments, the user may accept the shell suggested and designed by the software. 
         [0028]    Once the biocompatible shell has been designed, the biocompatible shell is created (Block  108 ). The biocompatible shell may be created through a rapid prototyping process or a milling process. In some embodiments, the biocompatible shell may created by manually or mechanically forming titanium or titanium alloy mesh into a desired shape, such as by molding the shell over a model. 
         [0029]    An outer surface of the biocompatible shell may be roughened, etched or imprinted (Block  110 ). The roughening, etching or imprinting of the outer surface helps to encourage tissue attachment to the shell to prevent dehiscence after the shell has been installed. The process may include one or more of the following techniques: imprint etching and acid perforation, laser imprinting, mechanical alteration, chemical surface alteration, embossing, or other suitable technique. Ionization techniques, Acetate mineralization, and/or blasting techniques may also, or alternatively, be implemented. In addition to the etching the outer surface, an inner surface of the shell may be polished, or otherwise made smooth, in some embodiments. 
         [0030]    With respect to laser etching, the etching may be performed at a suitable wavelengths and powers for etching titanium or titanium alloy. The depth of the etching may vary based on the material used for the shell and the power and wavelength of the laser used for the etching. Appropriate wavelengths and power levels may be empirically determined. In some embodiments, the etching may include perforations through the shell. 
         [0031]    The perforations may be distributed across the entire shell or may be located in specific locations on the shell, such as in locations that will be in contact with soft tissue. 
         [0032]    In some embodiments, the perforations may be randomly distributed and in other embodiments the perforations may be uniformly spaced and/or arranged in lines and/or columns or other patterns. The perforations extend through the shell and may have diameters ranging from approximately less than 0.1 mm to 1.5 mm. In some embodiments, each of the perforations may have approximately the same size diameter, such as 0.25 mm, for example. 
         [0033]    Apertures may also be created through the shell for fastening members, such as fastening screws, and for the installation of dental implants if the shell is to be implemented in a combined bone augmentation/dental implant strategy (Block  112 ). The fastening members are used to attach the shell to existing bone structure. As such, the apertures for fastening members may generally be located about a lower periphery of the shells. The apertures of the dental implants may be generally located at or near an apex or crest of the shell, as the dental implants are generally installed near the alveolar crest. 
         [0034]    In some embodiments, a radiographic image of bone that is to be augmented may be digitally stored and uploaded to a remote network accessible site. The network accessible site may be accessed via the Internet, a local area network, a wide area network, or other network connection. Once uploaded, the image may be used to design the biocompatible shell and/or the dental implants. Specifically, a doctor or technician may access the image and design the biocompatible shell based on the image. Thus, the network accessible site may be configured to run image processing and graphics software. In some embodiments, the site may provide computer aided drafting software for use in designing the shell. In some embodiments, the site may allow for design of the shell using a first program and export the design to a second program for creation of the shell. In some embodiments, the shell may be designed at a computer workstation local to the technician or doctor and, subsequently, the design may be uploaded to the site. 
         [0035]    Once the design is created and received at the site, the doctor, technician or other individual may place an order to have the designed shell manufactured. The shell may be manufactured and then shipped to the doctor for installment. Thus, the shell is made according to custom specifications set forth by the doctor or technician. 
         [0036]    Optionally, in some embodiments, a model of the bone structure and a model of the biocompatible shell may be created to aid in designing and properly positioning the biocompatible shell and/or dental implants relative to the existing bone. The creation and use of models may be optionally implemented in addition to the previously described steps. In particular, as illustrated in  FIG. 1 , a model of the existing bone may optionally be created from the radiographic image (Block  120 ). Additionally, once the shell has been designed (Block  106 ), a model shell may be created (Block  122 ). In one embodiment, both the model shell and the model bone may be created through CAD modeling and the stereolithic process. 
         [0037]    A model surgery may be performed by installing the model shell on the model bone (Block  124 ). Through the model surgery, it is determined if the model shell fits the model bone (Block  126 ). Determining whether the model shell fits the model bone may help to determine if the designed shell will fit with the existing bone structure. If the model shell does not fit the model bone, the design of the model shell (and the design of the shell) may be adjusted (Block  128 ). 
         [0038]      FIG. 2  illustrates a block diagram of a system  200  that may be used for the manufacture of the biocompatible shell. The system  200  includes an imaging device  202  that obtains images of the existing bones structure in the area where a bone graft is to occur. As described above, the imaging device  202  maybe a radiographic device such as a CT scanner or other suitable device. The imaging device  202  provides the images to a computing device  204 . The computing device  204  may be local to the imaging device  202  in some embodiments. In other embodiments, the computing device  204  may be remotely located from the imaging device  202  and images may be provided to the computing device  204  via a network connection, a computer readable medium, such as a DVD, a flash drive, or other suitable means. 
         [0039]    The computing device  204  includes a processor  206  and a memory  208 . The processor  206  is coupled to the memory  208  and is configured to run software, programs, applications, etc., stored in the memory  208 . For example, the memory  208  may store computer aided drafting programs may be executed by the processor  206  to allow for rendering, creation and manipulation of images, such as images of the shell. The computing device  204  may also include I/O devices (not shown) to provide output to a user (such as images via a display) and a to receive input from a user (such as via a keyboard and a mouse). 
         [0040]    The images of existing bone structure may be stored in the memory  208  and read by the processor  206 . Additionally, images of the shell may be stored in the memory  208  and provided to a shell generator  210  for creation of the shell. In some embodiments, the shell generator may be a stereolithography device, a CNC mill, or the like, and may be configured to automatically form the shell, or models from the information (i.e., images) provided from the computing device  204 . In some embodiments, computing device  204  may provide the images to the shell generator  210  via a network connection. It should be appreciated that the system  200  shown in  FIG. 2  is simplified and an actual implementation may include more devices. For example, each of the imaging device  202  and the shell generator  210  may have dedicated computing devices with which the computing device  204  may communicate. 
         [0041]      FIG. 3A  illustrates a profile view of an example model  250  of demineralized bone. As mentioned above, the model  250  may be created using a stereolithic process from radiographic images. Generally, the stereolithic process may include selective solidifying of a photo curable, clear liquid acrylic resin, layer by layer, using an ultraviolet laser beam to produce a transparent, high precision anatomical facsimile model that includes thin bony layers and closed cavities. 
         [0042]      FIG. 3B  illustrates a model shell  252  placed on the model bone  250 . The model shell  252  may be modified as needed to achieve the desired shape and dimensions based on the modeled bone  250 . 
         [0043]    To facilitate modifications and analysis during the model surgery, the model bone produced by the stereolithic process may be mounted on an articulator with an appropriate vertical dimension and bite relation to allow a surgical prosthetic team to identify and address aveolar deficiency or malrelation. The model includes the hard tissue elements and, as such, can be used to determine any deviation from the alveolar plane. 
         [0044]    The model surgery using stereolithographically generated bone structure allows for visualization of key anatomic structures. For example, the model surgery may allow for visualization of the alveolar plane, inferior alveolar nerve, pneumatization of maxilla, and dental roots, among other things. 
         [0045]    The model surgery also allows for modeling surgical guides for implant placement may be made by a rapid prototyping machine using a vat of photo-polymerizing resin from which a laser moves in segmental cross-sectional increments to polymerize an approximately 1 mm layer of resin based on the format of the CT image. Subsequent layers are polymerized on top of this layer until the entire CT image has been polymerized in resin, creating a completed model of the bone. The stereolithographic machine also reads CT planned cylindrical guides corresponding to each implant such that it polymerizes resin around each site for subsequent placement of guide tubes which are then fitted inside the cylindrical tubes. 
         [0046]    In some embodiments, once the optional model surgery has been completed, and the model shell fits the model bone, the biocompatible shell may be created (Block  108 ). In particular, the biocompatible shell may be created of titanium, titanium alloy, or any other suitable material based on the designed and modeled shell. In some embodiments, the shell may be made of a resorbable material such as a polyactate, or other such material. The shell may be created through a suitable process. In some embodiments, the shell may be machined. In other embodiments, a stereolithographic process may be implemented to create the shell, in accordance with known stereolithographic techniques. 
         [0047]      FIG. 4  illustrates a cross-sectional view of a biocompatible shell and guide. The general shape of the cross-section of the shell  300  may be arcuate and in some cases similar to a horseshoe shape. In some embodiments, the width of the shell  300  is thicker near a top ridge  302  (or rib) and tapers narrower on both lingual and labial sides  304  and  306 , respectively. Specifically, the ridge  302  may be approximately 1.5 to 3.0 mm (e.g., 2.3 mm) thick while the ends of the lingual and labial sides  304  and  306  may be approximately 0.5 to 2.6 mm (e.g. 1.3 mm) thick. 
         [0048]    Surgical guides may be created concurrently with the manufacture of the shell  300  using the same process as used for the shell. A guide  308  is illustrated in  FIG. 4 . The guide  308  may be made of a suitable material, such as a metal, and in some embodiments may have a cylindrical shape with a hollow center through which tools, biomedical implants, or devices may pass. For example, dental implants may pass therethrough, the guide directing the positioning of the dental implants. The surgical guides can be tooth, soft tissue or bone supported. Additionally or alternatively, the guides may be supported by the shell  300 . 
         [0049]    After placement of the dental implants, the guide  308  is removed and may be discarded. One study determined these types of guides were accurate to within 0.95 mm in the maxilla and 1.28 mm in the mandible in 110 implants placed clinically. Tooth supported guides were slightly more accurate than bone supported guides with an angular deviation of 2 to 4 degrees in tooth born and 3 to 7 degrees in bone guides. This was only slightly less accurate than found in vitro. 
         [0050]      FIG. 5  is a profile view of the shell  300  installed on a jaw bone  320 . The shell  300  may be held in place with shell fastening screws  322  which screw into atrophic bone  324  of the jaw bone  320 . The shell fastening screws  322  may be installed in pre-drilled apertures through the shell  300 . In some embodiments, the apertures may be uniformly spaced about a lower periphery of the shell  300 . In other embodiments, the placement of the apertures (and hence the placement of the fastening screws) may be customized according to existing bone structure as determined by the radiographic image of the existing bone. For example, the apertures may be located on the shell in locations that will allow the shell to be securely positioned relative to the bone rather than in regions that may have reduced strength, density, and/or structure. 
         [0051]    Additionally, apertures may be located along the ridge  302  for installing dental implants. In  FIG. 5 , cover screws  340  on the dental implants  326  may be seen.  FIG. 6  shows a longitudinal cross-section view of the shell  300  so that the dental implants  326  may better be seen. The shell  300  functions as a stent for the dental implants  326  to provide proper placement and angulation for the implants  326 . Although the dental implants  326  are illustrated as being installed vertically in  FIG. 6 , it should be appreciated that the implants may be installed at various angles. For example, the implants  326  may be installed at angles between 17 degrees to 30 degrees. Additionally, in some embodiments, there may be more or fewer dental implants. For example, in some embodiments an “All on 4” strategy may be implemented where all teeth are supported by 4 dental implants. 
         [0052]    In some embodiments, when installed, the dental implants  326  may extend into the existing bone  324 . As such, the existing bone  324  and the shell  300  support the dental implants. In some embodiments, the dental implants  362  may be installed into portions of the existing bone  324  that allows for secure fixation of the dental implants. That is, in areas where the existing bone  324  is sufficiently strong to help support the dental implants  326  until the bone graft may help support the implant. The determination as to strength of the existing bone and structure of the existing bone may be extracted from the radiographic images of the existing bone  324 . 
         [0053]      FIG. 6  also shows the interior of the shell  300  filled with bone graft material  330  may be seen. The bone graft material fills the interior of the shell  300  and surrounds the dental implants  326 . As the bone graft material  330  hardens to form bone, the dental implants become secure in the newly formed bone and the newly formed bone supports the dental implants. 
         [0054]      FIG. 7  illustrates a top view of the shell  300  installed on the jaw bone  302 . Cover screws  340  may cover the dental implants  326 . Additionally, the cover screws  340  provide structural support to the dental implant to hold the implants in a desired location and/or orientation while the bone graft heals. As may be seen, the shell  300  may have a generally arcuate shape that generally conforms to the shape of the jaw bone  302 . It should be appreciated that in some embodiments the shell  300  may have different shapes depending need for bone growth and/or implants. For example, in some embodiments, the shell  300  may have a generally straight shape (such as a short segment of the shell  300  that extends across the front of the jaw bone  302 ). 
         [0055]    The cover screws  340  may more easily be seen in  FIG. 8  which is a segmental cross-sectional view of the installed shell  300  along line AA of  FIG. 7 . Additionally,  FIG. 8  shows shell fastening screws  322  installed on both sides of the shell  300  to secure the shell to the atrophic bone  324 . In some embodiments, the lingual side  304  of the shell  300  may have a different length from the labial side  306 . 
         [0056]      FIG. 9  is a segmental perspective cross-sectional view of the installed shell  300  taken along line BB of  FIG. 7  showing the spacing of the dental implants  326  (and cap screws  340 ) and the fastening screws  322 . The cap screws  340  run along the top ridge of the shell  300 . When the bone has healed into the shape of the shell  300  and the shell is removed, the dental implants allow for placement of teeth along an alveolar crest of the newly formed/augmented bone structure (i.e., may be longer or shorter). 
         [0057]    A technique  600  for installing the shell  300  is illustrated as a flowchart in  FIG. 10 . The technique  600  includes installing the shell  300  on the atrophic bone  324  (Block  602 ). High profile dental implants  326  are installed into the atrophic bone  324  (Block  604 ). The shell  300  acts as a guide for implant placement and helps hold the implant in place. Bone growth material is then injected into the shell  300  (Block  606 ). In each of the above-described cross-sectional views of the installed shell  300  ( FIGS. 6 ,  8  and  9 ), bone growth material  330  may be seen. Specifically, bone growth material such as BMP-2 is injected into the space between the shell  300  and the atrophic bone  324 . The bone growth material is allowed to heal for a period of time (e.g., approximately six months) after which the shell  300  is removed (Block  608 ). The removal of the shell  300  reveals an augmented bone that secures the dental implants  326  in place. 
         [0058]    Although the present subject matter has been described with respect to particular embodiments, it should be appreciated that changes to the described embodiments and/or methods may be made yet still embraced by alternative embodiments of the invention. For example, one alternative embodiment, may include milling the titanium shell rather than producing the shell through a rapid prototyping process. Specifically, a computer numerical control (CNC) milling machine may be use to mill a titanium, titanium alloy (or other material) blank to achieve the desired shape, contours and size of the shell. The CNC milling machine may operate based on CAD drawings of the shell, similar to the operation of the rapid prototype. 
         [0059]    Additionally, although each of the drawings illustrating the biocompatible shell show a solid construction made from a unitary piece of material, in some embodiments, the biocompatible shell may be made of a mesh, such as a titanium mesh. The titanium mesh may be mechanically or manually manipulated to conform with a desired shape. The titanium mesh may serve the same functions as the biocompatible shell having a solid construction. 
         [0060]    Further, although several embodiments were directed to a combined bone graft and dental implant strategy, it should be appreciated that the biocompatible shell and the method of manufacturing the shell may be implemented in accordance with various bone graft strategies. For example, a biocompatible shell may be used in bone graft strategies for an orbital bone, a zygomatic bone, a femur bone or other bone. Accordingly, the proper scope of the present invention is not to be limited by the embodiments described above but, rather, defined by the claims herein.