Dentistry – Prosthodontics – Holding or positioning denture in mouth
Reexamination Certificate
2001-01-22
2003-06-24
Prebilic, Paul (Department: 3738)
Dentistry
Prosthodontics
Holding or positioning denture in mouth
C623S023560, C623S002220, C427S002240
Reexamination Certificate
active
06582228
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The instant invention relates to surgical implants and related systems for use with surgical implants, inclusive of orthopedic and dental implants for the purpose of enhanced osseo-integration of the implant into the surgical site to further post-operative efficacy of the implant-related procedure. The present invention is particularly of interest in use with metallic implants such as those of titanium, titanium alloy, titanium/aluminum/vanadium alloy, zirconium and tantalum and metallic implants coated with an osseo-simulative material such as hydroxyapatite.
2. Dental Implants
There exist many implants; each designed for a specific function. Most are made of titanium, an inert metal which has been proven to be effective at fusing with living bone, a process known as “osseointegration.” The cylindrical or screw type implant called “root form” is similar in shape to the root of a tooth with a surface area designed to promote good attachment to the bone. It is the most widely used design and generally placed where there is plentiful width and depth of jawbone. Where the jawbone is too narrow or short or immediate placement of root form implants the area may be enhanced with bone grafting to allow for their placement.
When the jawbone is to narrow and is a good candidate for bone grafting, a special narrow implant, called “ plate form,” can be placed into the bone, i.e., in cases of advanced bone loss, such a subperiosteal implant may be prescribed. It rests on top of the bone but under the gums.
The actual implant procedure involves the surgical placement of an implant, a healing period (osseointegration), and implant restoration to replace the missing tooth or teeth. The treatment may be a cooperative effort between a surgical dentist who actually places the implant and a restorative dentist who designs, prescribes and inserts the final replacement teeth. Some dentists having advanced training provide both of these services.
Root form implants are the closest in shape and size to the natural tooth root. They are commonly used in wide, deep bone to provide a base for replacement of one, several, or a complete arch of teeth. After application of an anesthetic, the dentist will expose the area of the jawbone to be implanted and prepare the bone to accept the implant. The number of incisions and manner of bone preparation depends upon the number of implants (and teeth) to be replaced. The implant is carefully set into place and the gums are closed with several stitches. The healing period usually varies from three to six months. During this time osseointegration occurs. The bone grows in and around the implant creating a strong structural support. In fact, this bond can be even stronger than the original tooth's. When healing is complete, the implant is uncovered and an extension or abutment is attached to it. At that time, the implant and abutment act as a solid unit ready to support the patient's new tooth or teeth.
3. Orthopedic Implants
Owing to the rapid development of surgery, it is now possible to carry out operations to bones and joints which were recently inconceivable. For example, it is now possible to carry out surgical removal of cysts, foci of suppuration in bone, and several of malignant tumors from bones. This results in defects in the bone, which need to be filled since normal bone repair processes are no longer able to compensate them. Some defects of this type may have a volume of up to 600 cm to be filled.
For filling cavities of this type use is made of bone replacement materials in liquid, pasty or a solid form such as granules or implants for implantation. If the cavities which are to be filled are not too large, then the purpose of the bone replacement materials is to temporarily fill the cavities in the bone and to allow the body itself to compensate, in the course of time, for the defect with living bone material.
4. Bio-compatible Materials
Bone implants are frequently used in surgical procedures, which are implanted in the bones of the body of a recipient and permanently replace parts of the skeleton or roots of teeth. The outer layer of the bone implant, which comes into contact with the living substrate bone, is termed the bone-contact layer. At the present time, metals, such as, for example, special steels, noble metals, titanium, ceramic materials, such as, for example, alumina,. glass-ceramics, hydroxy-apatite ceramics and synthetic materials are used as bone implants and as bone-contact layers.
These substances are classified as biocompatible and bioactive according to the tissue compatibility. Biocompatible substances are tolerated by the body in the long term without rejection. Bioactive substances become rigidly incorporated like endogenous tissue, the tissue compatibility determined by the chemical composition, the crystalline structure, the surface structure and the mechanical properties.
The metals and some ceramic materials such as, for example, alumina ceramics, are biocompatible. Ensheathing by connective tissue always takes place in the body. This connective tissue layer allows the implant to be held relatively rigidly, but does not allow frictional connection to the mineral framework of the substrate bone.
Because of the absence of primary integration into the substrate bone, a biocompatible implant of this type can be exposed to only slight mechanical stress since otherwise it is held poorly, which is associated with pain and, finally, the loss of the implant. This is found, for example, with hip joint prostheses which are always subject to great stress and for which more than one quarter of the operations are carried out are because of loosening of an implant which had previously been inserted.
Thus, additional undercutting such as, for example, a screw thread is necessary for permanent mechanical anchoring of biocompatible implants in bone. With all metallic implants it is still an unanswered question of whether they release toxic metal ions into the surroundings and thus may have adverse effects in the long term. Even when bone cement is used, despite the initially better mechanical connection to the substrate bone, the loosening above described takes place, although with some delay.
In about the last twenty (20) years, implant techniques that employ many artificial hard tissue materials have been used surgeons. Among these materials, bioglass and bioceramics, such as hydroxyapatite and beta-tricalcium phosphate, have excellent biocompatibility. Most of the bioglass and bioceramics for medical applications are prepared either in granule or block form. The granule form has mobility problems and relatively poor manipulation characteristics, while the block form is quite brittle and difficult to shape. Many other techniques have been attempted to solve the above-noted problems. Various of these techniques have employed other materials such as: plaster of paris (calcium sulfate), CS hemihydrate, collagen, different types of calcium phosphate grout or cement, polylactates and polyacrylate cement compositions. None of these have been completely acceptable.
5. Desired Parameters
The surgeon is often interested in implant techniques that employ materials that can be shaped and hardened in situ. Ideally, an effective implant technique should employ a surgical cement or binder system for hard tissue applications, having the following characteristics: good biocompatibility, a suitable resorption rate, moldable at the surgical site, and controllable setting time and characteristics.
Most currently techniques employing available surgical cements and binder composition system have disadvantages. For example, collagen-hydroxyapatite and polylactate-hydroxyapatite composites can only be made as premolded shapes and cannot be molded at the surgical site.
Generic plaster of paris, which is derived from gypsum, has reasonable setting characteristics but its resorption rate is too fast. Polyacrylate cement is non-resorbable. Polyacrylic acid-calcium phosphate cement is not resorbable and the
Alexander Harold
Hollander Bruce
Kozak Ingo
Ricci John L.
Gilpin Crystal
Li Yi
Prebilic Paul
Silverman M. K.
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