Dental implant system and method

An abutment has a central portion between a post portion receivable in a dental implant and a head portion having a selected configuration. A shelf extending from the head portion outwardly to the central portion forms an angle alpha between approximately 0 and 30 degrees with an imaginary plane perpendicular to a longitudinal axis of the head portion to form a confluent joint with a crown of various emergence profiles thereon. A crown is fabricated, in certain embodiments, utilizing a sleeve having a negative image closely matching that of the selected head portion configuration. The finished crown is attached to the abutment, as by cement, polished and then inserted into the osteotomy site, angularly adjusted and locked in place using a seating device made by means of a seating jig.

FIELD OF THE INVENTION
 This invention relates generally to restorative dentistry and other medical
 procedures and more particularly to surgical implementation in the mouth
 of a patient and to prosthesis systems and methods used with such
 prosthesis systems.
 BACKGROUND OF THE INVENTION
 The natural teeth of an individual may be lost as a result of dental
 disease or trauma, making it desirable to replace such teeth with one or
 more prosthetic devices. An example of a prosthetic device is the dental
 implant which is surgically positioned within the mandibular or maxillary
 alveolar bone.
 One type of dental implant has a first implant member for placement in an
 osteotomy site in the alveolar bone of a patient. Following healing, a
 head member, commonly called an abutment, is mounted in or on the first
 implant member and a tooth simulating prosthesis or crown is then mounted
 on the abutment. A successful system of this type is disclosed in U.S.
 Pat. No. 4,738,623. In that patent, a first implant or root member having
 a first or outer end formed with a female socket circumscribed by a
 shoulder and having a suitable anchoring means, such as outwardly
 extending fins, is placed in an osteotomy site or implant receiving cavity
 formed in the alveolar bone with suitable surgical instruments and
 techniques. The first implant member is inserted into the cavity with the
 upper portion of the member a selected distance below the opening of the
 cavity, that is, below the crest of the bone, e.g., two or three
 millimeters. A healing plug is inserted into a female socket of the first
 implant member and particles of a natural and/or synthetic bone growth
 stimulating grafting material are then packed within the cavity around the
 shoulder of the implant member and the wound is then closed.
 Following healing, the dentist accesses and removes the plug and replaces
 it with an abutment. The abutment has a male portion received within the
 female socket and an intermediate, outer generally hemispherical surface
 portion which may extend through the surface of the gingiva and preferably
 through the surface of the crest of the bone which may have been
 previously reamed to form a complimentary configuration when forming the
 cavity. A prosthetic device can then be attached to the abutment forming a
 smooth continuous surface with the hemispherical surface portion of the
 abutment with the interface between the prosthetic device and the abutment
 being supragingival or, for best aesthetics, subgingival, that is, being
 covered by the gingival tissue. Fabrication of the prosthetic device
 typically involves making an impression, generally a full arch impression,
 and pouring a model forming, inter alia, a positive replica, or die, of
 the abutment head. A laboratory technician then burnishes platinum foil
 over the die which then serves as a core on which a prosthesis is built.
 Upon completion and firing of the prosthesis, the platinum is scratched
 away. Although this procedure has been acceptable, the efficacy of the
 result is dependent upon the skill of the technician and is highly labor
 intensive and time consuming. Alternatively, the technician could
 fabricate the prosthesis by a lost wax technique utilizing a central core
 of metal, usually a gold palladium alloy, onto which porcelain powders are
 added and fused in a firing oven. Still other techniques for prosthesis
 fabrication include the use of implant and abutment analogs, acrylics or
 composite resins. However, such methods are also highly labor intensive
 and time consuming.
 SUMMARY OF THE INVENTION
 It is an object of the invention to provide an implant system and method
 which minimizes laboratory procedures and concomitant expenses and time
 delays. Another object of the invention is the provision of an improved
 implant system and method in which consistent accuracy of the component
 parts, as well as the implant as a whole, is enhanced. Another object of
 the invention is the provision of a system and method for overcoming the
 above noted prior art limitations.
 Briefly stated, a first embodiment of the invention comprises an abutment
 having a central portion between a post portion and a head portion, the
 post portion being receivable in the bore of a dental implant and the
 central portion being formed with a smoothly curved, convex outer surface
 extending from a relatively large periphery progressively down to a
 smaller periphery which joins the post portion. The head portion has a
 smaller outer periphery than that of the relatively large periphery of the
 central portion with a shelf formed between the base of the head portion
 and the central portion which forms an angle with a plane perpendicular to
 the longitudinal axis of the head portion within a range of approximately
 0-30 degrees to facilitate the forming of a confluent joint with a
 prosthesis received on the head portion which is compatible with a human
 body, i.e., one which the body will not try to reject. The shelf slopes
 downwardly toward the post portion end with respect to a direction going
 radially outwardly from the longitudinal axis. More preferably, the angle
 is approximately 15 degrees. The provision of the angled shoulder permits
 the use of a prosthesis having a matching shoulder at the entrance to a
 head receiving cavity and having any one of various emergence profiles,
 that is, the interface of the prosthesis and the abutment can be on the
 shelf either flush with or inboard of the outer periphery thereof and
 still be compatible with the human body. Generally, the curved surface of
 the central portion of the abutment is generally spherical however it can
 also be of other smoothly curved configurations, such as ellipsoidal.
 Preferably, the implant is formed with a bore having a self-holding taper
 of less than 5 degrees and the post is formed with a matching self-holding
 taper. However, if desired, the bore and post could be threaded or the
 post could have no taper and be attached to the implant by cement or the
 like.
 According to another feature of the invention, an integrated crowned
 abutment is formed by providing a sleeve of suitable material, such as
 porcelain, metal, resin or the like, having an internal head seat with a
 negative image closely matching that of a head portion of an abutment
 having a selected configuration so that the sleeve can be fitted precisely
 onto such a head portion. The sleeve is placed on the head portion of a
 temporary abutment having the selected configuration and having a post
 removably inserted in the bore of an implant positioned in an osteotomy
 site. An impression of moldable material is taken of the removable
 abutment and the area adjacent to the osteotomy site. The impression is
 removed from the patient's mouth with the sleeve remaining in the
 impression. A transfer abutment having a head portion with the same
 selected configuration is placed within the sleeve and the transfer
 abutment is inserted in an implant analog. Molding material is then poured
 into the impression to form a model or replica of the area adjacent to the
 osteotomy site with the implant analog locked in the model. The model is
 removed from the impression and the sleeve is removed from the impression
 and positioned on the transfer abutment in the model. A prosthesis is then
 built on the sleeve by adding suitable material such as porcelain, metal,
 resin and the like, and shaping the material within the available space
 between teeth or prostheses contiguous with and opposing the osteotomy
 site. The prosthesis is then attached to a permanent abutment having a
 head portion with the selected configuration by any suitable means, such
 as cementing, clipping, frictionally engaging as with a self-holding
 taper, or the like, to form an integrated crowned abutment. The integrated
 crowned abutment can be polished extraorally to remove extraneous cement
 when cement is used as the means of attachment and then the finished
 abutment can be inserted into the implant with the angular position being
 adjustable to any desired orientation and then locked in place.
 Preferably, the implant is provided with a bore having a self-holding
 taper of less than 5 degrees and the post of the abutment with a matching
 self-holding taper so that attachment is obtained by tapping the abutment
 into the implant with a selected force in a manner to be described. It
 will be understood, however, that it is within the purview of the
 invention to employ posts with no taper which can be cemented into the
 implant.
 When using the self-holding attachment system a special jig is provided for
 ensuring that the locking force is imparted to the integrated crowned
 abutment by a force which is essentially collinear with the longitudinal
 axis of the post portion and in a way that will not mar the surface of the
 crown portion. The jig comprises a telescoping two part generally U-shaped
 frame having a seating cup in one leg of the frame with a post receiving
 orifice formed through the center of the seating cup, and a depression
 formed in a second leg of the frame extending below the plane in which the
 bottom surface of the second leg lies and aligned with the longitudinal
 axis of the orifice and the seating cup. The post of an integrated crowned
 abutment is placed through the orifice and the curved portion of the
 central portion of the abutment is seated in the seating cup. Suitable
 parting material, such as Vaseline or Saran wrap, is placed on the crown
 portion of the integrated crowned abutment to prevent adhesion of resin,
 such as epoxy, to be injected thereabout. The vertical position of the
 second end of the frame member is adjusted and doughy epoxy or other resin
 is placed between the integrated crowned abutment and the second leg of
 the frame including the portion extending below the plane in which the
 bottom surface of the leg lies. After the resin cures and hardens the
 frame is removed and the seating device is trimmed of flash and the like
 leaving a crown portion replicated bottom surface which will be aligned
 with the longitudinal axis of the post of the integrated crowned abutment
 when the seating device is placed on the crown. In use, the integrated
 crowned abutment is placed in the implant and the angular orientation is
 adjusted as desired either before or after the seating device is placed on
 the crown portion. Force is then imparted through the indentation in the
 epoxy which is aligned with the longitudinal axis of the post to ensure
 that the imparted force is collinear therewith.
 According to a modified embodiment, a prefabricated crown element may be
 selected for placement on the head of the removable abutment, either with
 or without the use of a sleeve core. A cavity is provided, or is formed,
 in the prefabricated element and adapted to receive the head portion of an
 abutment, or the sleeve as described above, and the outer configuration is
 adapted to fit between contiguous and opposing teeth or prostheses
 relative to the osteotomy site to form a finished crown. The finished
 crown is then attached to an abutment having a self-holding tapered post
 extraorally to form an integrated crowned abutment for subsequent
 insertion into an implant having a matching self-holding taper positioned
 within an osteotomy site. The integrated crowned abutment is polished
 extraorally and inserted into the implant and its angular position
 adjusted and finally it is locked in place.
 Additional objects and features of the invention will be set forth in part
 in the description which follows and in part will be obvious from the
 description. The objects and advantages of the invention may be realized
 and attained by means of the instrumentality's, combinations and methods
 particularly pointed out in the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 FIG. 1 shows a prior art system comprising an implant 10 disposed in an
 osteotomy site in the jaw of a patient. Implant 10 has a bore 12 formed
 with a self-holding taper and mounts therein an abutment 14 having a post
 portion 16 formed with a matching self-holding taper so that the abutment
 can be locked in place by tapping the abutment along the longitudinal axis
 of the post portion with at least a selected force. Abutment 14 has a
 central portion or base 18 formed with a smooth curved outer surface
 configuration and a head portion 20 which serves to mount a prosthesis
 thereon. Further details can be obtained by reference to U.S. Pat. No.
 4,738,623, referenced above, the subject matter of which is incorporated
 herein by this reference.
 As mentioned above, a crown or other prosthesis is typically fabricated by
 a relatively labor intensive and time consuming process involving the
 burnishing of platinum foil on the head of an abutment which is then built
 upon and shaped to fit within the space available between contiguous
 teeth, as shown in FIG. 1, or prostheses, and the opposing teeth or
 prostheses (not shown). After completion of the prosthesis the foil has to
 be carefully removed, as by scraping, before the prosthesis can be
 permanently attached to the abutment mounted in the implant. If cement is
 used in attaching the abutment, care must be exercised to avoid having
 extraneous cement on the outer surface which would irritate the gingiva.
 According to an embodiment of the invention, fabrication of a prosthesis is
 greatly simplified by first forming the crown utilizing an abutment analog
 and then integrating the crown and a permanent abutment so that the
 prosthesis can be finished and polished extraorally. This facilitates the
 subgingival placement of the cement interface since there will be no flash
 or excess cement to irritate the gingiva tissues. The finished integrated
 crowned abutment, preferably having a post portion with a self-holding
 taper, is then inserted into the implant, its angular orientation is
 adjusted as desired and then it is tapped into locking engagement in the
 implant as a single unit utilizing a customized seating device to be
 described infra.
 With reference to FIG. 2 an abutment analog 30 has a post portion 32, a
 generally cylindrical portion with a longitudinal axis 33, formed with a
 longitudinally extending slot 34 so that the post can be removably
 received in the bore of an implant having a self-holding taper. Abutment
 analog 30 has a central or base portion 36 formed with a smooth, convex,
 outer surface configuration 38, such as spherical, ellipsoidal or the
 like. A head portion 40 having a selected configuration, such as
 frusto-conical, extends along a longitudinal axis, in the embodiment shown
 axis 33, from central portion 36 on a side removed from post 32 and with
 the larger end of the frusto-conical configuration disposed at the central
 portion. Head portion 40 is preferably formed with retention means such as
 annular groove 40a, vertically extending serrations to prevent relative
 rotation (not shown), a flat (not shown), or the like. A shelf 42 extends
 from the junction of head 40 with central portion 36 out to the outer
 configuration 38. Shelf 42 preferably forms an angle alpha with an
 imaginary plane perpendicular to the longitudinal axis of head portion 40
 in the range of approximately 0-30 degrees, and more preferably
 approximately 15 degrees, for a purpose to be discussed below.
 After an implant, such as implant 10 of FIG. 1, has been inserted into an
 osteotomy site, or after it has been allowed to heal for a certain period
 of time, it is uncovered and a removable abutment analog, or, if desired,
 a permanent abutment is placed into the newly uncovered implant along with
 a sleeve core member 44 having an internal head seat 44a being a negative
 image of and closely matching that of head portion 40 and preferably
 formed with a retention means such as annular groove 44c on its outer
 periphery for a purpose to be described. An impression using conventional
 moldable material is taken of the area adjacent to the osteotomy site
 along the alveolar crest with sleeve 44 remaining in the impression with
 the aid of retention means 44c. An abutment analog or transfer abutment
 having a head with the same selected configuration is then placed within
 the sleeve and a slotted post of the abutment analog is inserted into an
 implant analog and then a positive model is made of the outer surface of
 the sleeve and the adjacent area with the implant locked in the model. A
 prosthesis is then built on the sleeve by adding and shaping the
 prosthesis material within the available space between teeth and/or
 prostheses contiguous with and opposing the osteotomy site. Prosthesis
 material can be any suitable material such as porcelain, metal, resin or
 the like.
 When the building and shaping has been completed prosthesis 46 is removed
 from abutment analog 30 and is then attached to permanent abutment 50
 (FIG. 3), having the identical head portion configuration, by any suitable
 means, such as cementing, clipping, welding, frictional engaging, or the
 like, to provide an integrated crowned abutment. The integrated crowned
 abutment is then polished to ensure a smooth outer surface and, if the
 crown was attached by cement, to remove any extraneous cement material.
 Post 52 of abutment 50 is preferably formed with a self-holding taper of
 less than 5 degrees and diameter matching that of the bore of the implant
 with which it is intended to be used. The post portion of the finished
 integrated crowned abutment can then be inserted into the bore of the
 implant disposed in the osteotomy site and the angular orientation
 adjusted as desired by use of a customized acrylic jig or indexing
 alignment device fabricated on the laboratory model so that the crown is
 properly positioned within the available space and then locked in place.
 It will be appreciated that abutments having angled heads relative to the
 post, as indicated by abutment 50' in FIG. 3a, can be employed in
 practicing the invention. Further, although a self-holding taper is
 preferred for post 52, other configurations could be used, e.g.,
 cylindrical with no taper, and could be attached to the implant by means
 of cement or the like.
 Shelf 42 forms an angle alpha (FIG. 2) of from approximately 0-30 degrees
 with an imaginary plane perpendicular to the longitudinal axis of the head
 portion as noted above. This feature enables the use of crowns having
 various emergence profiles as noted by 46 and 46' shown in dashed lines in
 FIGS. 2 and 3. This results in a confluent joint between crown 46, 46' and
 either the shelf 42 or outer surface 38 of the abutment which is
 compatible with the human body, that is, the body will not react
 negatively to the presence of a step between the crown and the abutment as
 long as the step forms an angle alpha, as defined.
 It should be noted that the end surface 44b of sleeve 44 is preferably
 formed having a matching angle to that of shelf 42 to provide a closely
 conforming mating surface.
 In accordance with another embodiment of the invention, a prefabricated
 crown element or blank may be used with abutment 50 in fabricating an
 integrated crowned abutment. A blank crown having the particular desired
 characteristics of color and general configuration of the desired
 simulated tooth is selected and a head receiving cavity is then formed in
 the crown blank, if not already provided. The blank crown is then placed
 on the head portion of an abutment analog having the same head portion
 configuration with the abutment analog positioned in a model analog of the
 type described above and then material is added to, removed from and the
 crown blank is otherwise shaped to fit in the space between contiguous and
 opposing teeth and/or prostheses relative to the osteotomy site to form a
 finished crown. The finished crown is then attached extraorally to an
 abutment and, after suitable polishing, is inserted into the implant
 positioned within the osteotomy site. Alternatively, the fabricated crown
 could be attached to the permanently seated abutment intraorally by
 cement, friction or chemical bonding.
 An integrated crowned abutment, made in accordance with the invention,
 having a sleeve core 44 is shown in FIG. 5 in which a crown 46" is
 attached to abutment 50 and in which post 52 is formed with a self-holding
 taper of less than 5 degrees. As shown in the drawing, crown 46" may form
 a slight step 42a which is compatible with the human body. An integrated
 crowned abutment, made in accordance with the invention, utilizing a
 preformed blank crown without the use of a sleeve core, which is custom
 fitted to abutment 50 as well as to contiguous and opposing teeth, is
 shown as crown 46'" in FIG. 6. The crowns formed in accordance with FIGS.
 5 and 6 both have an end surface 46c having an angle which matches that of
 shelf 42.
 Completed integrated crowned abutments having self-holding tapers on their
 post portions are locked in place by being tapped into the implant with at
 least a given minimum force. However, it is important that the prosthetic
 crown restoration not be damaged during this procedure. Such integrated
 crowned abutments may be installed using an alignment and indexing jig
 arrangement shown in FIG. 4. A generally U-shaped, telescoping, two part
 frame 70 is shown comprising a first L-shaped part 72 having a leg 72a
 formed with a cupped seat 72b having a concave configuration matching that
 of the outer convex surface configuration 38 of the base or central
 portion 36 of abutment 50 and having a post receiving orifice 72c, or
 other suitable opening, such as a fork, formed in the center of seat 72b.
 Second L-shaped part 74 has a leg 74a formed with an indentation 74b
 aligned with the longitudinal axis of orifice 72c and cupped seat 72b
 which is collinear with longitudinal axis 33 of the post 52 when the post
 is received in the cupped receptor. Second part 74 has a tubular second
 leg 74d which telescopically receives leg 72d. Preferably, a release agent
 such as Vaseline jelly or Saran wrap is placed over the surface of the
 crown portion to avoid sticking of epoxy to be discussed. Frame part 74 is
 then placed over crown portion 46"" and a suitable doughy epoxy is packed
 into the space between leg 74a and the crown portion 46"" including the
 protruding portion 74c of leg 74a opposing indentation 74b and allowed to
 cure into a hardened state. Frame part 74 is then removed and the
 integrated crown abutment and seating device 76 is removed from frame part
 72. The seating device is timed of any excess flash so as not to interfere
 with adjacent teeth or implants in seating the integrated crowned
 abutment. Seating device 76, as formed, has a bottom surface 74a
 replicating the top surface of crown 46"" and a top surface having an
 indentation 76b formed by protrusion 74c which will be aligned with the
 longitudinal axis of the post portion of the integrated crowned abutment
 when seating device 76 is received on the integrated crowned abutment.
 The integrated crowned abutment can then be inserted into an implant with
 the seating device 76, the angular orientation of the abutment adjusted as
 desired along with the seating device which conforms to the outer surface
 configurations of the crown portion and is movable therewith, and then by
 using a conventional seating instrument which fits into the indentation
 76b and a conventional mallet, a locking force can be delivered which will
 automatically be directed along the longitudinal axis 33 of the post
 portion and without damaging or marring the crown portion.
 Seating device 76, along with abutment shelf 42, as described above, makes
 practical the extraoral fabrication of integrated crowned abutments.
 A method for fabricating a prosthesis such as a crown, utilizing a sleeve
 core 44 comprises placing an abutment analog 30, that is, an analog which
 is removably receivable within a self-holding tapered bore of an implant,
 into the bore of an implant positioned within an osteotomy site. The head
 portion of the abutment analog is formed with a selected configuration. A
 sleeve core formed of suitable material having an internal head portion
 seat which is a negative image closely matching the selected head portion
 configuration of the abutment analog is placed on the head portion of the
 abutment analog. An impression using conventional moldable material is
 taken of at least the area adjacent to the osteotomy site along the
 alveolar crest with the sleeve remaining in the impression. An abutment
 analog serving as a transfer analog, having the same selected head portion
 configuration, is placed within the sleeve and the abutment analog is
 inserted into the implant A model is then made by pouring conventional
 dental stone material into the impression and, after hardening, is
 separated from the impression. The sleeve is removed from the impression
 and positioned on the abutment analog in the model and then the crown
 portion is built, for example by conventional techniques and shaped to fit
 within the available space between teeth contiguous with and opposing the
 osteotomy site.
 The registration or removal of the removably receivable abutment can be
 accomplished at the time of implant surgery, i.e., the first stage, or
 after osseointegration of the implant, i.e., the uncovery or second stage
 surgery. If done at the first stage then the finished crown could be
 fabricated during the healing time and completely ready at the uncovery
 stage thereby resulting in time convenience for the patient as well as the
 clinician.
 When the crown is completed it is then attached to an abutment having the
 same selected head portion configuration using any suitable attachment
 mechanism. The integrated crowned abutment is placed in jig 70 and a
 seating device is fabricated. After trimming of excess flash, and after
 polishing, the finished integrated crowned abutment is inserted into the
 implant in the osteotomy site and seating device 76 is positioned on the
 crown, the angular orientation of the prosthesis is adjusted as desired
 and then it is locked in place.
 As noted supra, if desired, a preformed crown blank may also be utilized
 either with or without a sleeve core in forming an integrated crowned
 abutment in accordance with the invention, however, the sleeve core not
 only facilitates the subgingival placement of the cement interface as
 noted above, it also can minimize the need for angular abutments, or
 reduce the angularity thereof, since the trajectory through the sleeve
 core could accommodate different angulations of the prosthesis. An
 elliptical sleeve core, for example, would enhance the aesthetic and
 function particularly of anterior teeth. Different trajectories of the
 orifice in the sleeve core would accommodate the need for different
 alignment angulations of the crown relative to the implant. This is
 particularly the case in the buccal-lingual (front to back) direction. The
 side to side or mesio-distal direction would also be accommodated by the
 angulation of the abutment. The use of the sleeve having the negative
 image of head portion 40 obviates the labor intensive platinum burnishing
 process without sacrificing precision fitting. The sleeve can be formed of
 any suitable material by molding, machining or any other suitable means
 which will replicate the image of the head.
 In view of the above, it will be seen that an abutment sleeve comprised of
 ceramic material attachable to a titanium alloy abutment can provide for
 an aesthetic tooth color material as an integral part of the abutment on
 which a conventional prosthesis can be cemented with the tooth colored
 material being subgingival even if the prosthesis/abutment interface is
 supragingival. Although the sleeve is shown with an open top end it will
 be understood that it could have a closed top end as well. Further, if
 desired, an opening in the side wall of the sleeve could be provided to
 accommodate direct contact of the metal abutment for seating purposes.
 Although not shown, a seating depression could be provided in the top
 surface of integrated crown abutment, if desired.
 Although the invention has been described with regard to specific preferred
 embodiments thereof, variations and modifications will become apparent to
 those skilled in the art. It is therefore, the intention that the appended
 claims be interpreted as broadly as possible in view of the prior art to
 include all such variations and modifications.