Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
2001-12-03
2003-12-02
O'Connor, Cary E. (Department: 3732)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
C433S174000
Reexamination Certificate
active
06655961
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to dental implants, and more specifically to a dental implant having an improved configuration to take advantage of the bone topography that is often present following tooth extraction.
Dental implants are used in place of missing and/or extracted natural teeth as the base of support for an abutment and final prosthesis in the attempt to restore normal oral function. Once teeth have been extracted, the alveolar bone at the extraction site heals and begins to undergo resorption. The resorption process is halted by restoring loading forces with a dental implant. The topographic changes of the alveolar bone have been described in the dental literature and are time dependent with regard to the amount of bone resorption. While implants are designed to replace natural teeth, they also must be designed to consider this natural healing of bone as well.
The implant body is surgically inserted in the patients jaw and becomes integrated with the bone. More specifically, the implant body is screwed or pressed into holes drilled in the respective bone. The surface of the implant body is characterized by macroscopic and microscopic features that aid in the process of osseointegration. Once the implant is fully integrated with the jaw bone, the abutment is ready to be mounted. For two-stage implant designs, the abutment passes through the soft tissue that covers the coronal end of the implant after healing and acts as the mounting feature for the prosthetic device to be used to restore oral function. Implants of the single-stage design extend through the tissue at the time of surgical insertion. The coronal end of the implant body acts as part of a built-in abutment design with the margin of the coronal collar usually used as the margin for the attachment of the prosthesis used to restore oral function. These components, the implant and abutment, are typically fabricated from titanium or an alloy of titanium as well as zirconia based, alumina based or sapphire based ceramics. In some instances, ceramics and metals are combined to make a single component, though this is usually limited to the abutment component of the implant system.
One of the major problems associated with dental implants stems from the failure to provide for the ideal alignment of implant fixtures in bone. Misalignment often results in the implant being positioned lingual to the ideal placement. Loosening or fracture of the abutments and even the implant body can result due to the adverse forces involved. Restorative dentists complain that the implants are not properly aligned by the surgeons, and the surgeons complain that the restorative dentists do not understand the challenges associated with the alignment process.
One of the most commonly placed fixture designs is the Branemark type implant. These implants are ideally positioned in the approximate center line of the space where the extracted tooth was previously position. As with most traditionally designed implants, the Branemark type fixture relies on a flat surface perpendicular to the long axis of the implant body for strength when joining the implant and the abutment together. This design usually displays a bone loss pattern described as a cupping of the bone at the coronal end of the implant once loaded with occlusal forces. This cupping pattern usually stabilizes after about one year of function with vertical bone loss of approximately 2 mm but, by that time, loss of bone critical to the predictable support of overlying soft tissue is lost.
Other implant systems often used are of the so called Astra Tech and ITI Straumann type implants. These implant designs have an internal conical connector and do not rely on perpendicular orientation of a flat surface for strength at the implant/abutment interface. Astra implants, due to or in combination with the rigid conical abutment connection and the presence of coronal stress reducing micro threads on the implant body, greatly reduce, and in some instances do not display the aforementioned bone loss patterns. However, the problem still exists as to the misalignment of such implants due to the flat topped coronal feature of the implant body in its present configuration.
Astra Tech has addressed coronal bone loss by introducing micro threads at the coronal portion of the implant body to distribute forces transferred to the surrounding bone. Other attempts to enhance implant designs have addressed bone loss patterns and lack of soft tissue support by focusing on the coronal aspect of the implant body in hopes of mimicking natural CEJ (cemento-enamel junction) anatomy or shaping the implant body to be more root line in character. Implants duplicating tooth anatomy in some way, shape or form have not had the same level of success as the Astra Tech concept. Unfortunately, once the tooth has been extracted, the bone does not remember what the tooth looked like, or what function it provided. Still, even with the Astra's success, the design of the implant fixture and how that design interacts with the bony anatomy at the surgical site has not been addressed correctly. To date, no design has considered the anatomy of how bone heals in the human jaw following tooth extraction.
Accordingly, it is a general object of the present invention to provide an improved implant such that many of the problems related to implant placement are eliminated.
It is a more specific object of the present invention to enable implants to be placed in surgical sites of sloping bony anatomy more predictably.
Another object of the present invention is to preserve lingual bone by having the coronal aspect of the implant being compatible with the bony anatomy that is higher on the lingual side of the surgical site.
It is another object of the present invention to provide for increased strength of the implant/abutment system.
Yet another object of the present invention is to reduce the amount of time required by the restorative dentist to prepare and idealize the abutment.
Another object of the present invention is to reduce the number of abutment orientation surfaces, thereby reducing the size requirement for the implant body.
Still another object of the present invention is to make the use of snap on impression caps more useful and resulting in the final prosthesis being more functional and cosmetic in appearance.
Yet another object of the present invention is to allow for a single implant to be placed in the anterior region of the human jaw with predictable soft tissue contours supported by bone.
Still another object of the present invention is to allow multiple implants to be placed more predictably next to one another in the anterior region of the human jaw.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a dental implant for implanting within a human jawbone, the jawbone having lingual and buccal sides. The implant includes a generally cylindrical longitudinal body having apical and coronal ends and an outer surface. The length of the body is defined by the ends along the outer surface. The coronal end is contoured such that the length of the body is greatest on the lingual side of the jaw when positioned within the bone.
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Cawood and Howell,Reconstructive Preprosthetic Surgery, I. Anatomical considerations. Int. J. Oral Maxillofac. Surg. 1991: 20; 75-82.
Cook, Alex, McFarron, Manzo Cummings & Mehler
O'Connor Cary E.
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