Osseointegrative surgical implant

Abstract

Embodiments of the present invention provide an osseointegrative implant and related tools, components and fabrication techniques for surgical bone fixation and dental restoration purposes. In one embodiment an all-ceramic single-stage threaded or press-fit implant is provided having finely detailed surface features formed by ceramic injection molding and/or spark plasma sintering of a powder compact or green body comprising finely powdered zirconia. In another embodiment a two-stage threaded implant is provided having an exterior shell or body formed substantially entirely of ceramic and/or CNT-reinforced ceramic composite material. The implant may include one or more frictionally anisotropic bone-engaging surfaces. In another embodiment a densely sintered ceramic implant is provided wherein, prior to sintering, the porous debound green body is exposed to ions and/or particles of silver, gold, titanium, zirconia, YSZ, α-tricalcium phosphate, hydroxyapatite, carbon, carbon nanotubes, and/or other particles which remain lodged in the implant surface after sintering. Optionally, at least the supragingival portions of an all-ceramic implant are configured to have high translucence in the visible light range. Optionally, at least the bone-engaging portions of an all-ceramic implant are coated with a fused layer of titanium oxide.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The application claims the benefit under 35 U.S.C. §119(e) to Provisional Patent Application No. 61 / 986,242 filed Apr. 30, 2014, the entire contents of which are incorporated herein by reference.STATEMENT RE: FEDERALLY SPONSORED RESEARCH / DEVELOPMENT[0002]Not ApplicableBACKGROUND[0003]The present invention generally relates to osseointegrative implants and related tools and components for surgical bone fixation and dental restoration purposes and improved methods for manufacturing and using the same.[0004]Surgical bone fixation devices such as screws, staples, rods, and plates have been in clinical use for decades. These devices largely evolved from industrial designs for fastening wood, steel, plastic and other materials. Starting in the 1950s Per-Ingvar Branemark and others demonstrated that implanted bone fixation devices made of pure titanium had the ability to become permanently incorporated with living bone tissue. That is, the livin...

AI Technical Summary

Benefits of technology

[0023]In accordance with other embodiments and variations of the invention, detailed surface features may include various unique patterns of dimples, bumps, spikes and / or similar surface features designed to improve primary stability and / or promote healing and osseointegration. Unique surface features may also include one or more frictionally anisotropic bone-engaging surfaces configured to reduce and / or increase friction in a desired direction relative to insertion or removal of the implant. Optionally, at least the bone-engaging portions of the implant are coated with a layer of titanium oxide that is fused to the ceramic surface of the implant via an electric discharge process. Optionally, at least the supragingival portions are densely sintered and annealed in an oxygen atmosphere to produce a ceramic implant having high translucence in the visible light range.

[0024]In accordance with other embodiments and variations of the invention, an all-ceramic implant is formed at least in part by sintering a green body formed by slip casting, powder compacting or injection molding a feedstock comprising 3 mol % yttria-stabilized powdered zirconia having an average particle size of about 0.16 μm. Optionally, the entire implant may be molded or powder compacted in green stage to substantially its final geometry (enlarged to account for shrinkage during subsequent sintering), including finely detailed surface texturing and other desired surface features. The green stage implant may be debinded (if a binder is used) and sintered in one or more sintering operations to produce a finished dental implant product that does not require any grinding or machining operations. The green body may be formed by injection molding a ceramic feedstock comprising powdered 3-mol % yttria-stabilized zirconia (Y2O3)3(ZrO2)97 having an average particle size of less than 0.25 μm and a BET surface area greater than about 8.0 m2 / g. The powdered YSZ is first coated with stearic acid by ball-milling with 3 vol % stearic acid solution. The SA-coated powder is then thoroughly mixed with a water-soluble binder until a solids loading of about 48% is reached.

[0025]In accordance with other embodiments and variations of the invention, a densely sintered zirconia implant may be formed by sintering a debound injection-molded green body. Prior to sintering, the debound green body is fully or partially immersed in an aqueous solution containing ions and / or particles of silver, gold, titanium, zirconia, YSZ, α-tricalcium phosphate, hydroxyapatite, carbon, carbon nanotubes, and / or other particles sufficiently small in size such that at least some of the particles enter and remain lodged in the implant surface after sintering. In an alternative embodiment, the debound green body may be fully or partially immersed in a colloidal solution containing particles of carbon, carbon nanotubes, and / or other carbon-based particles sufficiently small in size such that at least some of the particles enter and remain lodged in the porous surface of the green body and / or diffuse interiorly to a desired depth. The green body is then fully sintered in a vacuum chamber or other oxygen free environment. After sintering the implant is heated in an oxygen environment until substantially all of the carbon-based particles are fully oxidized and / or burned off leaving a porous outer surface having improved biological compatibility and / or osseointegration characteristics.

Problems solved by technology

One drawback of conventional single-stage implants is that there is limited flexibility in the placement of the implant because the supragingival portion is fixed relative to the subgingival portion and extends into the oral cavity typically in fixed coaxial alignment with the implanted subgingival portion.

In certain clinical situations the size, shape and orientation of the native or grafted bone at the osteotomy site can limit or preclude the use of a conventional single-stage implant.

One disadvantage of two-piece implants is that the retaining screw or other mechanical fastening device used to secure the abutment to the anchor can eventually loosen or break.

Furthermore the junction where the abutment seats against the anchor can form a micro gap, which can act as a bacterial trap and lead to infection.

However, too much residual stress can cause bone necrosis and / or recession over time, leading to reduced secondary stability (i.e., reduced osseointegration of the implant and / or long-term loss of securement).

However, primary stability is typically less with conventional press-fit implants because there is typically little or no positive mechanical engagement and interlocking of the implant body with the surrounding bone tissue.

A typical drawback encountered when using a titanium post or abutment to support a porcelain crown is that it generally results in a dark, central rod-like shadow in the restored tooth, particularly when exposed to high-brightness light.

This makes the prosthesis somewhat unattractive and able to be distinguished from a natural tooth, especially when the restoration is located in the upper anterior region of the mouth.

Further, since the materials are different at the bonding interface (porcelain versus titanium) and have different mechanical properties, surface chemistries and coefficients of thermal expansion, problems are frequently encountered when bonding or securing the prosthesis to the supporting abutment.

Clinical studies have also shown that titanium can cause adverse biological reactions when maintained in direct contact with the soft gingivae surrounding the implant site, leading to a higher-than-desired incidence of gum recession around the implant site and further compromising the desired aesthetics of the restoration.

Conventional ceramic abutments, while providing a viable alternative to titanium abutments and a solution to some of the aforenoted problems, do not completely resolve the aesthetic concerns and can also introduce a number of additional problems and challenges.

Aesthetic limitations result primarily from the relative opacity of the ceramic material when compared to a natural tooth and also the need for a metal (e.g., titanium) retention screw to secure the ceramic abutment to the implant.

Other problems and challenges stem from the fact that ceramic materials have a much greater hardness and much more limited flexure than titanium.

When a ceramic abutment is secured to a titanium implant, inevitable rocking of the abutment (due to, for example, chewing action) causes high-stress interactions between the relatively hard ceramic abutment and the relatively soft metal implant.

This can eventually damage the implant severely enough that surgical intervention is required to remove and replace the titanium implant.

However, the use of conventional ceramic materials and fabrication techniques have limited the number of applications due to high production costs, poor mechanical strength, low fatigue stability and tendency to crack or fracture over time.

Conventional ceramic implants have also historically been considered clinically less satisfactory than metal implants, such as titanium or titanium alloys, because of reduced primary stability resulting from inherent material limitations which limit the amount of torque or insertion force that can be applied to the implant body (for threaded implants), and reduced or retarded secondary stability resulting from slower and / or less complete osseointegration.

This makes the resulting sintered body extremely hard and difficult to machine and results in a finished surface having essentially no porosity.

A dental implant made of densely-sintered zirconia ceramic is typically bio-inert and, thus, has only weak osseointegrative properties.

Each of these proposed solutions involve multiple additional processing steps and materials which greatly increase the cost and complexity of manufacturing a finished product.

Despite various improvements over the years, conventional titanium implant designs and attachment components do not fully address the clinical needs for surgical replacement of natural teeth, particularly in clinical applications involving aesthetic regions of the mouth.

Compared with traditional titanium implants, currently-available ceramic implants are costlier to produce, are more limited in their clinical application, are more susceptible to failure via fracture and / or fatigue, and provide less primary and secondary stability.

Currently-available ceramic implants and attachment components also do not completely resolve the aforenoted aesthetic concerns due to the relative opacity of the ceramic materials used relative to the translucence of a natural tooth.

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