Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
1999-10-12
2001-05-22
Manahan, Todd E. (Department: 3732)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
Reexamination Certificate
active
06234797
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a dental implant, and more particularly to a dental implant with a thread design and structure which provides for dramatically improved loading to thereby facilitate an immediate load implant or an implant with dramatically reduced healing time. The present invention also relates to a method of installing the above identified implant.
2. Description of the Prior Art
Dental implants of various configurations currently exist in the art. These implants are installed into prepared bone sites and function as a device for anchoring a component such as a tooth or dental appliance in the patient's mouth. Examples of currently available dental implants are shown in U.S. Pat. No. 5,062,800 issued to Niznick, U.S. Pat. No. 5,368,160 issued to Leuschen, et al. and U.S. Pat. No. 5,582,299 issued to Laxnaru. Existing dental implant devices commonly include an implant having external threads for installation into a prepared bone site and a hollow interior with internal threads extending from its superior or top end downwardly into the interior of the main body of the implant. Such internal threads are used for connecting an implant mount during the installation process and for connecting a healing cap or a replacement tooth or other prosthesis when the installation is complete. During installation, the implant mount is connected with the implant via a threaded clamp screw. The implant mount interfaces with the implant through a hex connection which enables the implant to be rotated via rotation of the implant mount. It is common for the implant to be provided to the attending surgeon in a pre-mounted position with the implant mount connected to the implant by the clamp screw.
Installation of a dental implant in accordance with current procedures can be summarized as follows. After preparation of the bone site, a dental hand piece with a placement adaptor is positioned onto the implant mount via a hex or other connection. The implant is then positioned in the prepared bone site and installed by rotation of the implant mount, and thus the implant, in a forward or clockwise direction. The hand piece with attached placement adaptor is then removed from the implant mount and an open end wrench or other tool is positioned onto the hex end of the implant mount to remove the same. Because the interface between the threads of a conventional implant and the surrounding bone or tooth tissue is insufficient to resist the compressive forces resulting from normal chewing or biting action, it is necessary to allow the bone or tooth tissue in contact with such threads to heal before a replacement tooth or other prosthesis can be applied. In most cases, this period can be six months or more. Thus, following installation of a conventional implant and removal of the implant mount, a protective cover or healing screw is screwed into the internal threads of the hollow interior for the duration of the required healing time. In some cases the soft tissue surrounding the implant is extended and sutured over the healing screw, while in other cases the top of the implant is substantially flush with the surrounding tissue and the healing screw remains exposed during the healing period.
After the healing period has passed, the surgeon removes the protective screw and installs a healing cap. This healing cap is nonfunctional and remains in place while the tissue heals, generally 4-6 weeks. After this time period, the restoring doctor installs the replacement tooth or other prosthesis. The replacement tooth or other prosthesis commonly includes a mounting stem with external threads to be received by the internal threads of the hollow interior. Several drawbacks exist with respect to the current procedure. The primary drawback is that current procedures require two surgeries at intervals spaced by the required healing time: one surgery to install the implant, and a second surgery to remove the healing screw and install the healing cap and then later, the replacement tooth or prosthesis. The required healing time can be up to six months or longer. With conventional implants, the six month or more waiting time is needed because the external threads of the implant do not efficiently distribute the load and the bone is not strong enough immediately after installation to be fully loaded or to support the implant with a connected replacement tooth or other prosthesis. Thus, with current implants embodying current external designs, a healing period of up to six months or more is required after the first surgery (installation of the implant) to allow the tooth bone to grow around the implant and to heal.
Prior implant designs have existed that allowed a tooth to be placed on the implant immediately. However, these designs utilized osseointegration rather than the current bone implant connection. A further design utilized a threaded implant in combination with a series of tapping instruments to obtain the required compressive force resistance for immediately loading the tooth. Neither of these designs, however, has been widely accepted.
Accordingly, there is a need in the art for an improved dental implant with an improved thread configuration and an improved implant structure which eliminates the second surgery or dramatically reduces the time interval between the first surgery and placement of the final prosthesis.
SUMMARY OF THE INVENTION
In contrast to the prior art, the present invention relates to a dental implant which facilitates elimination of the second surgery to remove the healing cap and apply the prosthesis or which facilitates significant reduction of the time necessary between the first surgery and placement of the final prosthesis. More specifically, the present invention relates to a dental implant structure in which the ratio of the minor to major thread diameters (the core to thread ratio) is decreased, or the ratio of the major to minor thread diameters (the thread to core ratio) is increased. Specifically, these ratios are decreased and increased, respectively, to increase the thread strength of the implant to the point where healing time is eliminated or substantially reduced, thereby facilitating immediate or reduced time loading. The present invention further relates to a dental implant with an improved external thread design which dramatically improves the resistance of the implant to chewing or compressive forces, and thus similarly eliminates or substantially reduces the time period between implant installation and the loading of the implant. Still further, the implant of the present invention is designed to go into, but preferably not through, the cortical plate. Accordingly, the length of the implants of the present invention is preferably less than 20 mm, more preferably no longer than about 15 mm and most preferably about 10-15 mm in length.
To accommodate immediate loading of the implant of the present invention, the two piece abutment and cap screw of prior art implants are eliminated. Accordingly, in the present invention, the implant is provided with a unitary implant in which the threaded portion and the base or abutment portion for supporting the replacement tooth is a single piece structure in which such portions are integrally joined with one another.
One embodiment of the implant of the present invention is to eliminate the hollow interior of the implant and to significantly reduce the core to thread ratio below the standard 0.75. To accommodate the eliminated interior an outwardly extending top or prosthesis receiving post is provided above the neck of the implant to receive the replacement tooth or other prosthesis. It has been found that the reduction in the core to thread ratio results in an unexpectedly increased resistance to compressive forces such as chewing or biting to thereby facilitate immediate loading of the implant.
A further embodiment of the present invention includes providing the implant with an improved external thread design which includes first and second helical thre
Altiva Corporation
Dorsey & Whitney LLP
Manahan Todd #E.
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