Connection between a dental implant and an abutment

Details Connection between a dental implant and an abutment Connection between a dental implant and an abutment

2001-09-17

2003-12-16

Wilson, John J. (Department: 3732)

Dentistry

Prosthodontics

Holding or positioning denture in mouth

Reexamination Certificate

active

06663388

ABSTRACT:

FIELD OF APPLICATION OF THE INVENTION
The present invention relates to a connection arrangement which comprises a dental implant known per se, which can be inserted into the jaw bone, and an abutment to be fixed on the implant. At the top, on the head of the implant, an axial, downwardly extending receiving hole, which is preferably widened conically upward, opens out within an encircling implant shoulder. The lower root part of the abutment, which, when there is a conical inner configuration of the receiving hole, has a complementary conical outer contour, can be inserted into the receiving hole. For the reproducible positioning of the abutment, a non-rotationally-symmetrical receiving contour may be advantageously provided in the receiving hole and have relating to it a corresponding, non-rotationally-symmetrical outer mating contour on the root part of the abutment. The non-rotationally-symmetrical contours complementing one another likewise represent a rotational securement for the inserted abutment, the rotational securement in fact already being brought about by the cone-cone connection between the inner cone of the implant and the conical root part on the abutment.
From the bottom of the receiving hole there extends further downward a coaxial. internally threaded hole for the engagement of a base screw disposed axially in the abutment, so that the abutment is fixed on the implant by screwing in of the base screw. The base screw is introduced into the abutment, the head of the base screw being supported in the abutment, while the threaded shank of the base screw protrudes out of the abutment at the bottom and engages in the internally threaded hole in the implant. Connection arrangements of this type are used both for straight abutments and for angled abutments. The base screw secures the abutment axially on the implant and—if the implant and abutment have non-rotationally-symmetrical contours engaging in one another—also against rotation in addition to the cone-cone connection. The selectable rotational positions in which the abutment can be fixed are limited by the shaping of the non-rotationally-symmetrical contours, for example the number of corners of polygons used.
PRIOR ART
The basic structure of the implant—but still without a non-rotationally-symmetrical receiving contour, preferably an internal polygon—is known for example from the monograph by SCHROEDER/SUTTER/BUSER/KREKELER: Oral Implantology, Georg Thieme Verlag Stuttgart, 2nd edition 1996, page 127. Such an implant has the implant head at the top and the shank part at the bottom, the implant head terminating at the very top with the radially encircling implant shoulder and it being possible, depending on the type of implant, for there to be an external thread on the shank part. The implant shoulder surrounds the mouth of the receiving hole conically narrowing axially downward, whereby the inner cone is produced. At the bottom of the hole, the receiving hole merges into a coaxial internally threaded hole of reduced diameter, which extends apically into the shank part and has the internal thread.
WO 94/09717 and WO 97/14371 disclose implants of the type described above which have within the receiving hole an internal polygon arranged at a distance from the implant shoulder. Complementing this, there are external polygons on the respective abutments. The internal polygon in the implant brings with it considerable advantages as a positioning aid for the reproducible positioning of the inserted abutment in conjunction with the superstructures which are adapted by the prosthetist or dental technician, and possibly as rotational securement. The angle of rotation with respect to the longitudinal axis of an inserted abutment whose neck part protruding above the implant shoulder is not rotationally symmetrical must be transferred to a dental model in relation to the anatomy surrounding the implantation site. In the case of the implant according to U.S. Pat. No. 4,960,381, the internal polygon is additionally used beforehand for screwing into the bone, in that a socket wrench is inserted into the internal polygon.
WO 97/14371 discloses a connection arrangement between an implant with an internal polygon in the conical receiving hole and an abutment with a corresponding, apically extending root part. In the case of this design, there is in the root part of the abutment, close to the lower outlet of the passage, a radial groove for receiving a spreading ring. The spreading ring is pushed onto the shank piece of the base screw and comes to lie under the screw head. The base screw can then be pushed with the screw head first into the root part, until the spreading ring slides into the radial groove. The abutment preassembled to this extent with the base screw and the spreading ring is inserted into the receiving hole of the implant. In the case of a straight abutment, the passage is axial. In the case of an angled abutment, the passage is likewise angled and may have an additional vertically oriented lateral opening for the perpendicular insertion of the screwing implement. The screwing implement is inserted through the passage or the lateral opening and the threaded shank of the base screw is thus screwed into the internally threaded hole of the implant. The screw head of the base screw presses on the spreading ring, which introduces the tensile force into the abutment, so that the latter is drawn into the receiving hole.
The connection arrangement according to WO 97/14371 has the major advantage that the screw head of the base screw does not have to be introduced from above into the passage of the abutment. This allows the passage at the coronal end, in which an internal thread for an occlusal screw may be provided, to be shaped such that it is dimensioned smaller than the diameter of the screw head of the base screw. The space available on the superstructure, for example on the artificial tooth crown, limits the size of the insertable occlusal screw. In the interests of the strength of the screw connection, however, a base screw which is not reduced in diameter in relation to the occlusal screw but has the same diameter may be used. The main resultant advantage is that screws of the same diameter as the base screw and as the occlusal screw that can be screwed into the coronal end can be used; i.e. the internally threaded hole in the implant and the internally threaded hole in the coronal part of the abutment have the same diameter. This serves for the reliability of the screw connections and simplifies the system which forms the implants of various configuration with the variety of structural parts and the set of implements.
With the connection arrangement according to WO 97/14371, significant progress was achieved in comparison with the previously applicable state of the art. The forming of the internal radial groove in the abutment and the use of the spreading ring disposed on the base screw and received in the radial groove cannot, however, be regarded as the ultimate, complete solution. The mechanical working of the radial groove in the abutment and a radial groove on the shank of the base screw in which the spreading ring is seated during the pushing of the base screw into the abutment must take place with high precision and altogether requires a not inconsiderable outlay in terms of working and inspection. Bearing in mind the relatively small dimensions of the connection arrangement, the relatively high forces to be absorbed under alternating loading and the enormous requirements for reliability, there is the need to retain the basic advantages of the connection arrangement but to lower the production outlay and, in particular, further increase the reliability. The head of the base screw presses on the relatively narrow annular surface at the top of the spreading ring and the spreading ring is for its part seated in a pressing manner on a likewise narrow horizontal annular surface within the radial groove.
OBJECT OF THE INVENTION
In view of the need to improve the functional reliability of the previously known c

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