Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
1999-11-29
2001-08-14
Wilson, John J. (Department: 3732)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
C433S173000
Reexamination Certificate
active
06273722
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention concerns a dental implant used as an artificial tooth root for holding a dental prostheses.
Dental implant typically comprises an elongated pin inserted into a hole drilled into the bone beneath a patient's gum tissue. The implants have taken two basic forms, a smooth cylindrical form which is press fit into the drilled hole and bonded to the osseous tissues to be held securely; and, a threaded form which is rotated into the hole which is suitably prepared by special bone tapping techniques.
The geometry of a threaded implant is such that it is immediately securely interlocked with the surrounding bone, the thread form when advanced into the hole creates excessive stresses in the bone tissue, which can cause the bone tissue to react and recede over time, leading to a loss of securement of the implant.
A threaded hole in the top of the implant is used for attachment of the prosthesis to the implant, and removal of a threaded attachment can sometimes result in loosening of the implant by unintended unscrewing of the implant threads when the attachment is loosened.
The press fit cylindrical form of the implant is simpler to install and has more bone attachment due to the absence of stress risers, but is less securely held in the bone tissue at the time that the implant is first driven into the hole since there is no positive mechanical interlock. The threaded form also has the advantage of having a greater surface area in contact with the bone, at least initially, to further increase the bonding forces.
Variations of these two basic forms have been devised, including a threaded form with the addition of a long pitch helical groove and through holes for receiving bone fragments packed into the groove to promote the growth of bone tissue into the groove for increased long term holding ability for the implant, as described in U.S. Pat. No. 5,676,545 issued on Oct. 14, 1997 for a “Method and Apparatus for Implantation”.
U.S. Pat. No. 5,762,499 issued on Jun. 9, 1998 for a “Dental Root Implant” describes a press fit geometry in which the implant body is tapered and has circumferential grooves for receiving bone growth. U.S. Pat. No. 5,195,892 issued on May 23, 1993 for a “Bone-Integrated Dental Implant System” describes longitudinal grooves in the implant sides to promote interlocking bone growth.
U.S. Pat. No. 5,269,686 issued on Dec. 14, 1993 for a “Threaded Drivable Dental Implant” describes a long pitch rounded thread on an implant body which is drivable in the drilled hole and which resists loosening when an attachment screw is removed.
It is the object of the present invention to provide a dental implant which has the advantages of both the press fit and threaded forms while minimizing the disadvantages of each.
SUMMARY OF THE INVENTION
The above object and others which will become apparent upon a reading of the following specification and claims are achieved by a hybrid form of implant, having a smooth cylindrical body sized to be press fit in a drilled hole.
In a first form, a long pitched helical groove is recessed into the smooth cylindrical surface of the implant body. The groove shape promotes rapid bone growth into the groove and the helical shape creates a slight threaded retention as the adjacent bone tissue will protrude slightly into the groove under the pressure of the press fit of the implant.
In the second form, a very shallow height, long pitch thread is added, projecting from the cylindrical surface of the body of the implant, having an opposite helix angle from the helical groove turns but of approximately the same long pitch. The thread turns are interposed between the groove turns so as to cross the groove turns at diametrically opposite points on the implant body. Segments of the thread are removed in the areas where the thread turns cross the grooves to create a flattened shape similar to the oval shape of a natural tooth root.
The very shallow height thread can be easily forced into the surrounding bone tissue as the body is advanced into the drilled hole, with displaced bone fragments guided into the groove. The thread turns increase the retention forces upon initially fitting of the implant. The shallowness of the threads obviates the need for any special hole preparation and avoids imposition of significant stress on the bone tissue to insure long term secure retention of the implant.
In a variation of the second form, the height of the shallow thread is tapered down towards the implant forward or tip end, to more gradually cut into the bone tissue as the implant is advanced into the predrilled hole.
REFERENCES:
patent: 5094618 (1992-03-01), Sullivan
patent: 5194000 (1993-03-01), Dury
patent: 5195892 (1993-03-01), Gersberg
patent: 5269686 (1993-12-01), James
patent: 5316476 (1994-05-01), Krauser
patent: 5366374 (1994-11-01), Vlassis
patent: 5449291 (1995-09-01), Lueschen et al
patent: 5601429 (1997-02-01), Blacklock
patent: 5676545 (1996-04-01), Jones
patent: 5762499 (1996-06-01), Dard et al.
Higgs Fletcher & Mack LLP
Reidelbach, Jr. Charles F.
Swiss Implants, Inc.
Wilson John J.
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