Resorbable implant

Details Resorbable implant Resorbable implant

1998-11-24

2001-06-26

Lucchesi, Nicholas D. (Department: 3732)

Dentistry

Prosthodontics

Holding or positioning denture in mouth

C433S201100, C623S016110

Reexamination Certificate

active

06250923

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to the field of implants, and more specifically relates to implants that are biocompatible and resorbable by bone.
BACKGROUND OF THE INVENTION
The references listed in this specification, to the extent that they provide exemplary procedural or other details supplementary to those set forth herein, are specifically incorporated herein by reference.
Dental implants used to stabilize dentures or support dental crowns and bridges have been known and have been used fairly extensively in the recent past. Such prior art devices are typically comprised of three components, namely, an implant component for anchoring to the bone, a transgingival component and a separate support component. The support component usually attaches to the transgingival component which, in turn attaches to the anchoring component at about the level of the bone. An artificial tooth or bridge may then be attached to this separate support component. This support component is sometimes referred to as an abutment portion, the transgingival component is sometimes referred to as an abutment connection or the transgingival collar or the transepithelial connection and the implant is sometimes referred to as a fixture. An example of such a prior device is found in Canadian Patent No. 1,313,597. This patent describes an implant for insertion into bone through an epithelial and fibrous connective tissue layer to which a prosthesis may be attached. This implant comprises a top portion for supporting a mechanical component to which the prosthesis may be connected and a body comprising an upper bone attachment region, which tapers to a lower bone engagement region having a porous surface. The upper bone attachment region comprises a substantially non-porous but bioreactive surface and this patent teaches that this results in an upper bone attachment region which is claimed to be capable of enhancing bone attachment.
However, several problems develop with an implant of this type. In particular, the patent teaches use of a collar
14
that is adapted to be coupled to the implant
12
. However the interface between the collar
14
and the implant
12
occurs at a level below the gingiva in the installed position. Further, although the patent teaches providing recesses
40
on the lower surface
42
of the collar
14
to compliment projections
32
of the implant
12
to prevent rotation between the two components, in practice this is not effective. The attachment between the collar and the implant is accomplished by means of a threaded screw identified as
46
in FIG.
1
. Such a screw has a natural tendency to become loose during the vigorous stresses to which an implant of this type is subjected.
To avoid problems associated with the loosening of the threaded screw
46
, practitioners have resorted to insertion of cement into the threaded portion to ensure a locked and non-loosening joint between the implant component and the support component.
However, a basic problem with this structure and method still remains. Substantial forces are exerted upon a very small region where the screw is affixed within the jaw. These forces are focused about a small region about point rather than being distributed. Using a plurality of closely set screws disadvantageously lessens the amount of material to which the implant may be affixed.
Unfortunately, screws eventually become loose, and damage to the bone into which they are affixed is permanent. Thus repeated re-tightening or insertion of new screws is limited and not practicable.
It is an object of this invention to provide a “snowshoe-like” effect wherein an implant is securely affixed becoming joined to bone at a multiplicity of points over a large region.
In the aforementioned prior art implant, unfortunately, because the interface between the collar and the implant is below the gum level, any excess cement will be squeezed out at the interface and may not be noticed by the practitioner since it is hidden from view. Such excess accumulation of cement can create irritation of the gum and the bone and can result in infection and/or implant failure. In addition, all implant systems, (fixture, abutment connection, abutment) which have this type of arrangement have a microgap between the fixture or implant and the abutment connection or the transgingival collar at the level of the bone. This microgap has been called an “sendotoxin generator” by some authorities because it is a region for potential bacterial growth.
Other prior art devices include implants with threaded exteriors, which require extensive and complicated methods for preparation of the gum and bone to accept the insert. As a result, such implants are difficult and expensive to insert and specialists most often do the surgery.
This invention provides an implant and method of fabricating such which obviates difficulties and associated problems with prior art implant systems.
An aspect of this invention relates to the use of a resorbable biocompatible material such as coral, to provide the overall implant structure.
The use of these biocompatible materials is well known to assist in the regeneration of bone defects and injuries. In 1926, DeJong observed the similarities between the powder X-ray diffraction pattern of the in vivo mineral and the hydroxyapatite (Ca
5
B(OH)(PO
4
)
3
, (CHA). Calcium compounds, including calcium sulfate (Nielson, 1944), calcium hydroxide (Peltier, 1957), and tricalcium phosphate (TCP) (Albee et al., 1920), have been observed to stimulate new bone growth when implanted or injected into bone cavities (Hulbert et al., 1983). These materials also exhibit good biocompatibility and compositional similarities to human bone and tooth and can serve as resorbable or non-resorbable implants depending on their degree of microporosity.
Some TCP implants are known to be readily resorbable. For example, sintered TCP plugs with pore sizes between 100-200 microns have been implanted in rats (Bhashar et al., 1971). Very rapid bone formation was reportedly observed at three days after implantation, and highly cellular tissue, consisting of osteoblastic and fibroblastic proliferation, was found within the pores. At one week, the size of the implant was reduced, and new bone formation was extensive. After two weeks, connective tissue had infiltrated throughout the ceramic. During the next four weeks, the bony material within the ceramic continued to mature. Electron micrographs indicated that within clast-like cells, ceramic could be depicted in membrane-bound vesicles. The authors concluded that TCP implants were biodegradable, via phagocytosis, the ceramic did not elicit a marked inflammatory response, and connective tissue grew rapidly within the pores. Similar results have also been reported by Cutright et al. (1972) who also implanted TCP in rat tibiae. In this study, the ceramic cavities were filled with osteoid and bone after 21 days and the TCP implant was no longer detectable after 48 days.
Larger implants in dogs are reported to elicit slower responses. Cameron et al. (1977) found that TCP implants in dog femurs were completely infiltrated with new bone by four weeks. However, after six weeks, the rate of new bone growth had slowed as the TCP was resorbed. Additionally, only 15% of a 2 cm×2 cm iliac TCP implant in dogs was resorbed after 18 months (Ferraro et al., 1979). Koster et al. (1976) reported the testing of the calcium phosphate formulations monocalcium phosphate, dicalcium phosphate, tricalcium phosphate, tetracalcium phosphate, and combinations consisting of 20% monocalcium phosphate and 80% of either di-, tri- or tetracalcium phosphate as implant materials in dog tibiae. These investigators tested both dense ceramics and porous ceramics with pore sizes between 800-1000 microns. They reported that tissue compatibility is dependent on the CaO/P
2
O
5
ratio. All materials with ratios between 2/1 and 4/1 are compatible with the optimum ratio being about 3/1 for TOP. After 10 months, Koster et al. (1977) found that tetracalcium phosphate was

Affiliated with

Also associated with

Rating

Resorbable implant does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Resorbable implant, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Resorbable implant will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2538050