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`(19) United States
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`(12) Patent Application Publication (10) Pub. No.: US 2011/0123951 A1
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` Lomicka (43) Pub. Date: May 26, 2011
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`US 20110123951A1
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`(54) POROUS IMPLANT DEVICE WITH
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`IMPROVED CORE
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`(75)
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`Inventor:
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`Matthew Lomicka, Fort Wayne, IN
`(US)
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`(73) Ass1gnee:
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`Zimmer Dental, Inc., Carlsbad, CA
`(US)
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`(21) Appl. No.:
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`12/624,608
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`(22)
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`Filed:
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`Nov. 24, 2009
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`Publication Classification
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`(51)
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`Int. Cl.
`(2006.01)
`A61C 8/00
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`(2006.01)
`A61C 13/08
`(52) US. Cl. ....................... 433/174; 433/173; 433/201.1
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`ABSTRACT
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`An implant device has an exterior portion forming an exterior
`surface of the implant. The exterior portion is made of a
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`porous material defining passages through the exterior por-
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`tion. An inner portion has an outer surface with a treated area
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`sages. The treated area has a treatment for direct attachment to
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`bone or soft tissue.
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`US 2011/0123951A1
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`May 26, 2011
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`POROUS IMPLANT DEVICE WITH
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`IMPROVED CORE
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`BACKGROUND
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`1. Field of the Invention
`[0001]
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`[0002] The present invention relates to porous implants
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`in particular,
`to an implant with a porous material
`and,
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`mounted on a core.
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`2. Description of the Related Art
`[0003]
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`[0004] Dental implants are commonly used to anchor den-
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`tal restorations or prosthetic teeth at one or more edentulous
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`sites in a patient’s dentition at which the patient’s original
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`teeth have been lost or damaged. The dental implant is typi-
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`cally threaded or press-fit into a bore which is drilled into the
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`patient’s mandible or maxilla at the edentulous site. Typically,
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`a dental implant device is provided in one or two pieces. For
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`a two piece device, an anchoring member or implant supports
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`a separate coronal dental abutment, which in turn provides an
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`interface between the implant and a dental restoration. For a
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`one piece integral device, the device has an abutment section
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`coronal to an implant section of the device. In either case, the
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`restoration is typically a porcelain crown fashioned according
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`to known methods.
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`[0005]
`For a two-piece device, there are two-stage surgery
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`implants (also called endosseous implants) that only rise to
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`the crest of the mandible or maxilla. In this case, the surgery
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`is often performed in two stages. In the initial stage, an inci-
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`sion is made in the patient’s gingiva at an edentulous side, and
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`a bore is drilled into the patient’s mandible or maxilla at the
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`edentulous site, followed by threading or impacting a dental
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`implant into the bore using a suitable driver. Thereafter, a cap
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`is fitted onto the implant to close the abutment coupling
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`structure of the implant, and the gingiva is sutured over the
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`implant. Over a period of several months, the patient’s jaw
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`bone grows around the implant to securely anchor the implant
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`in the surrounding bone, a process known as osseointegration.
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`[0006]
`In a second stage of the procedure following
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`osseointegration,
`the dentist reopens the gingiva at
`the
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`implant site and secures an abutment and optionally, a tem-
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`porary prosthesis or temporary healing member,
`to the
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`implant. Then, a suitable permanent prosthesis or crown is
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`fashioned, such as from one or more impressions taken of the
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`abutment and the surrounding gingival tissue and dentition.
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`The temporary prosthesis or healing member is removed and
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`replaced with the permanent prosthesis, which is attached to
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`the abutment with cement or with a fastener, for example.
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`[0007] Alternatively,
`a one-stage
`surgery,
`two-piece
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`implant, also called a transgingival implant, is placed in a
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`single stage because it extends through the gingiva for attach-
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`ment to an abutment. The one-piece implant also is placed in
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`the jaw in a single stage.
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`[0008] Although the osseointegration of existing dental
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`implants into surrounding bone has proven adequate, further
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`improvements in osseointegration of dental
`implants are
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`desired. For example, patients would prefer the shortest heal-
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`ing time from surgery to the time the implant can be fully
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`impacted by occlusal forces. Also, a desire exists to provide
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`strongly osseointegrated implants for high risk patients, such
`as smokers, diabetics and/or abnormally slow bone growth.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`FIG. 1 is a side perspective view of a dental implant
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`[0009]
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`device;
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`Page 6 of 11
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`[0010]
`FIG. 2 is an exploded perspective view of the dental
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`implant device of FIG. 1;
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`FIG. 3 is a bottom, cross-sectional view ofthe dental
`[0011]
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`implant device of FIG. 1 taken along the line 3-3 shown on
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`FIG. 1;
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`FIG. 4 is a close-up, fragmentary view ofa porous
`[0012]
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`material on the dental implant device of FIG. 1;
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`[0013]
`FIG. 5 is a side, cross-sectional view of an altema-
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`tive dental implant device;
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`[0014]
`FIG. 6 is a side, partially cross-sectional view ofyet
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`another alternative dental implant device; and
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`FIG. 7 is a side, cross-sectional view of a further
`[0015]
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`alternative dental implant device.
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`DETAILED DESCRIPTION
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`[0016] Referring to FIGS. 1-3, to improve osseointegration
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`onto the implant, an implant device 10 for placement in bone
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`has an exterior portion 12 made of a porous material 14 that
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`bone can grow into to improve long term stability of the
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`implant device. Such a porous material may also increase
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`short term stability for immediate loading because of its large
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`friction coefficient with surrounding bone as explained in
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`greater detail below. The exterior portion 12 may be placed on
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`or around an interior portion or core 16 that supports the
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`exterior portion and adds strength to the implant device 10.
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`The core 16 may have a surface treatment 18 to further
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`improve osseointegration with bone that has grown through
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`the exterior portion 12 and onto the core 16. Alternatively, or
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`additionally, the core 16 may also have an outer shape or
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`periphery 19 configured to limit rotation of the exterior por-
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`tion 12 relative to the core 16 for proper placement of the
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`implant 10 in a bore in bone and to increase both long term
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`and short term stability.
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`[0017] Now in more detail, in the illustrated example, the
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`implant 10 is a dental implant for insertion into a mandible or
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`maxilla. The implant 10 is used to anchor one or more dental
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`prostheses, and includes a coronal head portion or head 20.
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`The interior portion or core 16 extends apically from the head
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`20. In one form, the head 20 and core 16 are integrally formed
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`but may be separate pieces secured to each other by threading,
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`friction fit, welding (laser or e-beam), and so forth. A separate
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`anchor 22 (also referred to as the stem or apical portion) is
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`configured to engage the core 16 so that the head 20 and the
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`anchor 22 cooperatively retain the porous exterior portion 14
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`therebetween on the implant 10.
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`[0018]
`For the illustrated example, the coronal end 24 ofthe
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`head 20 is configured with male or female engagement struc-
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`ture that receives corresponding structure from a separate
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`abutment. It will be appreciated, however, that instead of the
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`two-stage implant 10 shown,
`the head 20 may have an
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`extended height to extend through gingiva and form a single-
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`stage implant, or may have an integral abutment to form a
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`one-piece implant.
`[0019] The head 20 has an outer cylindrical or tapering
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`surface 26 that extends to an apical end surface 28. The core
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`16 has a reduced outer diameter compared to the diameter of
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`the outer surface 26 and extends apically from an apical end
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`surface 28 of head 20 so that apical end surface 28 forms a
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`shoulder to abut and retain exterior portion 12 on the core 16.
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`In one specific form, the exterior portion 12 is a sleeve or
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`collar with a bore 30 that receives the core 16. In one form, the
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`collar 12 has a radial thickness of about 0.03 inches (about
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`0.75 mm). A coronal end 32 of the exterior portion 12 faces
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`US 2011/0123951A1
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`May 26, 2011
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`and/or abuts the apical end surface 28. An apical end 34 ofthe
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`exterior portion 12 faces and/or engages the anchor 22.
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`[0020] The anchor 22 may be secured to an apical end
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`portion 56 of the core 16 to secure the exterior portion 12
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`between the head 20 and the anchor 22. The anchor 22 may
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`have a bore 36 for receiving the core 16, and the two pieces
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`may then be welded together thereby permanently securing
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`the exterior portion 12 on the core 16. It will be understood
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`that many alternative configurations are contemplated such as
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`the core 16 and anchor 22 being held together by threads or
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`press-fit, or the core 16 being integral to the anchor 22 or
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`entirely separate instead of integral to the head 20 as men-
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`tioned above, and as long as the porous exterior portion 12 is
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`maintained adjacent the core 16.
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`[0021] The core 16, head 20, and anchor 22 (whether or not
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`one or more of the pieces are separate or integrally formed)
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`are made of a suitable biocompatible material such as tita-
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`nium, titanium alloy, stainless steel, zirconium., cobalt-chro-
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`mium molybdenum alloy, polymers such as polyether ketone
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`ketone (PEKK) for one example, ceramic, and/or composite
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`material.
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`[0022] The outer surfaces 26 and 37 of the head 20 and
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`anchor 22 may have threads 38 for threading the implant 10
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`into a bore in bone or may be press-fit into the bore instead.
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`Thus, the outer surfaces 26 and 37 may alternatively or addi-
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`tionally have surface treatment for promoting cortical bone
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`and/or cancellous bone growth. The head outer surface 26
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`may additionally or alternatively be treated to promote an
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`epithelium or soft tissue barrier and/or promote soft tissue
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`growth if the head 20 extends into the gingival layer. In this
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`case, barrier or soft tissue growth treatments can be placed
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`adjacent to soft tissue or the interface between bone and soft
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`tissue. Such treatments may include macro or micro thread-
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`ing, or circumferential or annular grooves, other patterned or
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`random recesses caused by etching (such as acid etching),
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`blasting (such as with sand, with or without HA particles, for
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`example), or also coating of titania (titanium oxide) or other
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`materials that create some adhesion between soft tissues and
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`biomaterials. The surface treatment of outer surfaces 26 and
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`37 may or may not be the same as the surface treatment of the
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`core 16 described below.
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`[0023] Referring to FIG. 4, the porous material 14 forming
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`the exterior portion 12 may include metal, and in one form, is
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`a porous tantalum portion 40 which is a highly porous bio-
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`material useful as a bone substitute and/or cell and tissue
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`receptive material.An example of such a material is produced
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`using Trabecular MetalTM technology generally available
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`from Zimmer, Inc. ofWarsaw, Indiana. Trabecular MetalTM is
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`a trademark of Zimmer Technology, Inc. Such material may
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`be formed from a reticulated vitreous carbon foam substrate
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`which is infiltrated and coated with a biocompatible metal,
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`such as tantalum, etc., by a chemical vapor deposition
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`(“CVD”) process in a manner disclosed in detail in US. Pat.
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`No. 5,282,861, the disclosure of which is fully incorporated
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`herein by reference. Other metals such as niobium, or alloys
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`of tantalum and niobium with one another or with other
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`metals may also be used.
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`[0024] As shown in FIG. 4, porous tantalum structure 40
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`includes a large plurality of interconnected members, liga-
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`ments, or beams 42 defining open spaces 44 there between,
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`with each member 42 generally including a carbon core 46
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`covered by a thin film of metal 48 such as tantalum, for
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`example. The open spaces or passages 44 between members
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`42 form a matrix of continuous channels having no dead ends,
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`Page 7 of 11
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`such that growth of cancellous bone entirely through porous
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`tantalum structure 40 is uninhibited. In other words, the bone
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`can grow from an exterior surface 50 ofthe implant 10 formed
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`by the exterior portion 12, generally radially through the
`passages 44 of the exterior portion 12, and onto the core 16.
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`[0025] The porous tantalum may include up to 75%-85% or
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`more ofvoids therein. Thus, porous tantalum is a lightweight,
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`strong porous structure which is substantially uniform and
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`consistent in composition, and closely resembles the struc-
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`ture of natural cancellous bone, thereby providing a matrix
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`into which cancellous bone may grow to anchor implant 10
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`into the surrounding bone of a patient’s jaw which increases
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`stability. The rough exterior surface of such porous metal part
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`12 has a relatively high friction coefficient with adjacent bone
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`forming the bore that receives the implant 10 to further
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`increase initial stability as alluded to above. This structure can
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`produce superior aesthetic results by restricting movement of
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`the implant. These implants can be placed without supple-
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`mentary surgical procedures, such as bone grafting, and can
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`be placed in areas where traditional implants have been less
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`successful, such as with reduced or decayed alveolar sections,
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`or with patients that have abnormally slow or reduced bone
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`growth.
`[0026] More specifically, the high level of friction between
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`the porous material and the bone provides immediate stability
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`post surgery. The tantalum struts that extend from the surface
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`ofthe material create a rasping action that may stimulate bone
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`growth and anchor the implant at the time of placement. The
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`extremely biocompatible tantalum metal
`that the porous
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`material is made from allows bone to directly oppose the
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`material. The tantalum forms a porous scaffolding that allows
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`bone to grow into the material providing a rapid osseointe-
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`gration response that quickly augments the initial mechanical
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`fixation to secure the implant. The implant with in-grown
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`bone may have stability greater than a comparably sized
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`implant with only on-grown bone. Finally, the composite of
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`in-grown bone and such a porous material has elastic proper-
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`ties much closer to bone than a solid metal implant, creating
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`a loading environment that is conducive to maintaining bone
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`near the implant.
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`[0027] Regarding the initial stability, as an implant with the
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`porous material is inserted into the bore or cavity in bone, the
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`porous material will bite into the bone by grating, chipping
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`and/or flaking bone pieces off of the bone sidewalls against
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`which the implant device is being placed. When the implant is
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`inserted into the bore or cavity, this “rasping” action may
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`form slight recesses or indents within the sidewall. This may
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`restrict rotational or twisting motion of the implant device
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`within the bore or cavity since the implant device does not
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`have the clearance to rotate out of the indents and within the
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`bore.
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`[0028] The rasping action also accelerates osseointegration
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`onto the implant device and into the pores of the porous
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`material due to the bone compaction into the pores. First, the
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`grating of the bone structure causes the bone to bleed which
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`stimulates bone growth by instigating production of benefi-
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`cial cells such as osteoblasts and osteoclasts. Second, the
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`bone pieces that fall into the pores on the porous material
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`assist with bone remodeling. In the process of bone remod-
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`eling, osteoblast cells use the bone pieces as scaffolding and
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`create new bone material around the bone pieces. Meanwhile
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`osteoclast cells remove the bone pieces through resorption by
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`breaking down bone and releasing minerals, such as calcium,
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`from the bone pieces and back into the blood stream. The
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`Page 7 of 11
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`US 2011/0123951A1
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`May 26, 2011
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`osteoblast cells will continue to replace the grated bone
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`pieces from the pores and around the implant device with new
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`and healthy bone within and surrounding the extraction site.
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`Thus, the porous material has increased resistance to twisting
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`or rotation, allows for immediate or very early loading, and
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`increases long-term stability due to the improved osseointe-
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`gration. Such an implant with ingrown bone has stability
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`greater than a comparably sized implant with only on-grown
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`bone. For instance, loads that typically require a 16 mm long
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`implant may be adequately impacted by an 8 mm long
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`implant. These advantages may be realized no matter the form
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`of the porous implant.
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`[0029]
`Porous tantalum structure 40 may be made in a
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`variety of densities in order to selectively tailor the structure
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`for particular applications. In particular, the porous tantalum
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`may be fabricated to virtually any desired porosity and pore
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`size, whether uniform or varying, and can thus be matched
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`with the surrounding natural bone in order to provide an
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`improved matrix for bone in-growth and mineralization. This
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`includes a gradation ofpore size on a single implant such that
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`pores are larger on an apical end to match cancellous bone,
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`and smaller on a coronal end to match cortical bone, or even
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`to receive soft tissue ingrowth. Also, the porous tantalum
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`could be made denser with fewer pores in areas of high
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`mechanical stress. Instead of smaller pores in the tantalum,
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`this can also be accomplished by filling all, or some of the
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`pores with a solid material.
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`[0030]
`To provide additional initial mechanical strength
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`and stability to the porous structure, the porous structure may
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`be infiltrated with a filler material such as a non-resorbable
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`polymer or a resorbable polymer. Examples of non-resorb-
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`able polymers for infiltration of the porous structure may
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`include a polyaryl ether ketone (PAEK) such as polyether
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`ketone ketone (PEKK), polyether ether ketone (PEEK), poly-
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`ether ketone ether ketone ketone (PEKEKK), polymethy-
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`lacrylate
`(PMMA),
`polyetherimide,
`polysulfone,
`and
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`polyphenolsulfone.
`[0031] Examples of resorbable polymers may include
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`polylactic co-glycolic acid (PLGA), polylactic acid (PLA),
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`polyglycolic acid (PGA), polyhydroxybutyrate (FHB), and
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`polyhydroxyvalerate (PFIV), and copolymers thereof, poly-
`caprolactone, polyanhydrides, and polyorthoesters. By pro-
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`viding additional initial mechanical strength and stability
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`with a resorbable filler material, a titanium reinforcing
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`implant core may not be required through the entire length of
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`the porous material. The resorbable material would resorb as
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`the bone grows in and replaces it, which maintains the
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`strength and stability of the implant.
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`[0032] Referring again to FIG. 1, the surface treatment 18 is
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`applied to a treated area 54 on an outer surface 52 of the
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`interior portion or core 16 for direct attachment to bone. Such
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`strong attachment of the core 16 to bone increases stability.
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`Alternatively, or additionally, the type of surface treatment
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`may be selected to promote an epithelium barrier, soft tissue
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`barrier, or soft tissue growth when a core on the implant is
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`extending through the gingiva as explained below for
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`implants 200 and 300 (FIGS. 6-7).
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`[0033] The treated area 54 is covered by the exteriorportion
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`12 so that the treated area 54 is accessible for direct contact
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`with bone that grows generally radially through the exterior
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`portion 12. In one form, the treated area 54 aligns or corre-
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`sponds to the exterior portion 12 such that the treated area 54
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`only extends underneath the exterior portion 12 and does not
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`extend beyond the exterior portion 12 where it is :covered. In
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`Page 8 of 11
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`this case, the surface area and outer periphery of the treated
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`area 54 are the same or about the same as that of the exterior
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`portion 12. By another approach, the treated area 54 may be
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`disposed on locations on the core 16 that is not directly
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`covered by the exterior portion 12. For example, the treated
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`area 54 may cover the entire core 16 while the exteriorportion
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`12 only extends in a coronal-apical direction over a part ofthe
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`core 16. Otherwise, the treated area 54 may have a smaller
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`surface area than that of the exterior portion 12 so that it only
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`extends under the exterior portion 12 whether or not the
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`periphery ofthe treated area 54 is the same shape as the outer
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`periphery of the exterior portion 12. At a minimum, treated
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`area 54 has at least some part extending underneath the exte-
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`rior portion 12 and accessible from the exterior surface 50 of
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`the implant 10 through the passages 44.
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`[0034]
`It will be appreciated that instead of a sleeve or
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`collar, the exterior portion 12 may only form part of the
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`circumference of the implant 10, or may only be located on
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`one or more sides of the implant 10. In that case, the treated
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`area 54 of the core 16 may or may not be configured to align
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`only with the area covered by the exterior portion 12.
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`[0035]
`In one form, the treated area 54 is at least roughened.
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`This may be performed by gritblasting or sandblasting the
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`treated area 54 to create a random pattern of pits on the outer
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`surface 52 of the core 16 with an average roughness (Ra) of
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`about 20 to 50 pm. The blasting may be performed by spray-
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`ing Hydroxyapatite (HA) or other bio-compatible materials.
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`By one approach, the treated area 54 has only been treated
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`with sandblasting but alternatively could have a variety of
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`different treatments instead of or in addition to, the sandblast-
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`ing. This includes acid etching of the treated area 54 to create
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`random or patterned roughening.
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`[0036]
`In another example of a treatment 18, the treated
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`area 54 may have at least one coating of a bio-compatible
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`material. The coating may include a bio-reactive material
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`such as HA, collagen, peptides, or other growth factors to
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`promote bone growth onto the core 16 (and/or promote soft
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`tissue growth if the core extends through gingiva). The coat-
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`ing could alternatively or additionally be anti-bacterial and
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`include transition metal ions such as Ag, Cu, or Zn, other
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`bactericidel polymers, antibiotics and/or nanoscale rough-
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`ness to prevent bacterial colonization on the treated area 54.
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`Other coatings may be applied to form a porosity into the
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`coating for better attachment. This may include Cancellous
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`Structure Titanium (CSTi) provided by Zimmer, Inc. that
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`includes Titanium powder sintered to the core 16 which forms
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`pores through the coating and a roughness to provide
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`improved fixation to the bone or soft tissue. The treated area
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`54 may alternatively, or additionally, have other roughening
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`treatments such as a circumferentially oriented roughness
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`like threads or annular grooves, or other patterns ofroughness
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`(whether on a macro, micro, or nano scale) as long as it
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`intentionally relates to direct attachment to bone (or soft
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`tissue when the core extends near or into the gingiva).
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`[0037] Typically an implant is treated with sandblasting
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`and so forth after the implant is fully assembled so that treat-
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`ment to exposed areas of an implant can take place in a single
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`step. In this case, however, since the outer surface 52 of the
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`core 16 is treated and then covered, the pieces of implant 10
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`are treated separately before assembly. Thus, first the head 20
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`with the core 16, the porous exterior portion 12, and the
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`anchor 22 are shaped as described above. The head 20 and, in
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`turn, the core 16 are then sandblasted or otherwise treated as
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`described above for direct engagement with bone or soft
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`Page 8 of 11
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`

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`US 2011/0123951A1
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`May 26, 2011
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`tissue. The head 20 and core 1 6 are treated separately from the
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`anchor 22, before the exterior portion 12 is mounted on the
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`core 16, and before the head 20 is attached to the anchor 22.
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`[0038]
`In one form, the entire head 20 including the apical
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`end portion 56 of the core 16 are blasted. It will be appreci-
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`ated, however, that the core 16 could be the only area treated
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`or blasted while the rest of the head 20 is masked from the
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`treatment. This may be desired if the other exposed areas of
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`the implant 10 receive a different type of treatment that could
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`be damaged by the treatment performed at the core 1 6, such as
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`coatings, blasting with different particles or particles of dif-
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`ferent sizes, patterned etching, and so forth. Also, the sidewall
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`57 of the apical end portion 56 could be masked since it is
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`unexposed within anchor 22 when the implant 10 is
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`assembled, or to provide a smooth connection surface if
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`needed.
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`[0039] Once the treated area 54 is complete, the exterior
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`porous portion 12 is mounted on the core 16, and then the
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`anchor 22 is mounted to the core 16 and secured thereon by
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`laser welding, threading, or other permanent connection. In
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`the illustrated form, after the apical end portion 56 ofthe core
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`16 is placed in the bore 36 on the anchor 22, the two are laser
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`welded together along a seam 58 at the apical end portion 60
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`of the anchor 22. When the head 20 and anchor 22 are laser
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`welded together, the welding process may also undesirably
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`smooth the roughening treatment on the anchor 22 such that
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`sandblasting may need to be reapplied to the anchor 22 on the
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`areas affected by the welding.
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`[0040]
`In another aspect of implant 10, the core 16 is
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`shaped to limit rotation between the head 20 and the exterior
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`portion 12. If the exterior portion 12 is able to rotate relative
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`to the core 16 and head 20 while the implant 10 is being
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`inserted into a bore in bone, the exterior portion 12 may
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`undesirably bind with the bo