Drug – bio-affecting and body treating compositions – Inorganic active ingredient containing – Phosphorus or phosphorus compound
Reexamination Certificate
2000-07-25
2003-03-25
Dees, Jose′ G. (Department: 1616)
Drug, bio-affecting and body treating compositions
Inorganic active ingredient containing
Phosphorus or phosphorus compound
C424S422000, C424S423000, C424S426000, C424S601000, C424S606000, C424S682000, C424S696000, C424S709000, C424S722000
Reexamination Certificate
active
06537589
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a novel calcium phosphate artificial bone as osteoconductive and osteoinductive, biodegradable substrate material which is highly able to promote biocompatible osteoanagenesis.
Particulary, the present invention relates to the novel calcium phosphate artificial bone promotive of biocompatible osteoanagenesis, which comprises an ordinary calcium phosphate bone cement and a linear polyphosphate comprising 3-200 orthophosphate molecules.
The polyphosphate-containing artificial bone of the present invention can substitute conventional bone cements, allografts and autografts which are used in the treatment of defects and fractures in every bone of the body, the cure of osteoporous, the fillers of implant for dental surgery, the bone substitute for plastic surgery, the substitution of defected bones in the operation on joints, including hip-joint, knee-joint and shoulder-joint, and the operation on the vertabra.
BACKGROUND
Bony tissues are connective tissues comprised of bone cells and extracellular matrices, but are different from other connective tissues in that the ossified connective substances within the extracellular matrices are inorganic. The inorganic substance consists mainly of calcium phosphate which exists as hydroxyapatite crystals(Ca10(PO4)(OH)2).
Bony tissues are hard enough to support and defend against physical stresses of the body, and their fracture or their density reduction or damage attributed to pathogenic changes may cause the body to suffer from deformity. When damaged or removed owing to any reasons, a bone has to be regenerated naturally or needs to be substituted with a prosthesis or a bone material from another body part by surgery. In addition, healing a physically broken(fractured) bone or a surgically damaged bone requires using various prosthetic tools, including artificial bones, for artificially relaying and immobilizing the bone. In this case, however, it takes a significantly long period of time for the bone to recover to its original figure and function while the patient suffers from serious physical and metal stresses. Further, as the healing procedure becomes long, the damaged part is increasingly apt to be under the danger of the infection with germs, so that a perfect curing effect may be not expected.
In the case of teeth, when an osseous tissue of maxillofacial parts is fractured or damaged pathogenically or physically, its substitution or regeneration is important in many aspects.
Particularly, alveolar bones, which support teeth, are not only easily infected with bacteria, but also difficult to recover naturally to the original condition if they are infected with bacteria or broken by other factors. In one of the most prevalent treatment methods of compensating for a damaged bony tissue of a tooth, a titanium-based metal graft is inserted into the jaw bone to construct an artificial tooth. However, this graft method is disadvantageous in that the inserted graft exerts excessive occlusal on neighboring alveolar bones and the grafting surgical operation cannot be allowed if the bone supports around the site of interest are not sufficient.
There remains an urgent need to develop methods of facilitating the healing process(regeneration) of damaged bony tissues or inducing the morphogenesis of new bony tissues, or materials suitable for use in this purpose. In connection, there have been developed selective materials for bone increase and reconstruction, such as bioceramics, composite materials and bone derivatives, as well as artificial fillers for bone recovery, such as natural or synthetic polymers.
At present, demineralized bone, hydroxyapatite and other graft substitutes were developed and have been used to facilitate osteoanagenesis at damaged bony tissue parts, but do not bring about a satisfactory accomplishment in the regeneration of bony tissues, in practice. Recently, growth factors, such as bone morphogenic factors(BMF), platelet-derived growth factors(PDGF) and insulin-like growth factors(IGF), and cytokines have been reported to be very useful in the regeneration of bony tissues. Also, it has been reported that, in order for the growth factors and cytokines to act for the regeneration of bony tissues, it is most important to express their cellular receptors. When associated with the cellular receptors, the growth factors and cytokines trigger the normal wound healing of bony tissues. The mechanisms in which the growth factors and cytokines are involved in wound healing and tissue regeneration, however, have not yet been clearly revealed. Since the growth factors and cytokines are synthesized at trace amounts in different types of cells, recombinant techniques are required to produce the growth factors and cytokines at sufficient amounts for application for the wound healing of damaged bony tissues. However, the recombinant techniques are not broadly utilized on account of an economical reason of high production cost.
Besides induction of natural osteoanagenesis, substitution of damaged bony tissues is also being undertaken by facilitating osteogenesis with various bone onlays and bone graft substitutes. Application of bone onlays and bone graft substitutes is conducted largely by two methods: an autograft method and an allograft method. Both of the two methods utilize patients' own bones to induce osteogenesis. The bones to be grafted must be similar in elastic modulus to bones adjacent to the graft area because graft materials greatly different in elastic modulus, e.g., metal grafts generate excess stresses.
However, grafting methods utilizing bone onlays also suffer from several problems. When adopting an autograft method, the grafts to be available are quantitatively limited. In addition, while a surgical operation is conducted to extirpate a necessary bone for autograft, there always exist the dangers of bacterial infection and blood loss. In addition, the areas from which grafts are extirpated become poor in structural stability. The grafting technique, including the surgery operation, may force some patients to endure pain for a longer period of time than does fusion surgery. Over the autograft method, the allograft method has an advantage in that supply of allografts can be relatively achieved because they are obtained from allo-donators, but allogenic bones are far inferior in osteoinductive potential to autogenous bones and thus, can be used as only temporary supports.
Additional problems are also found in both the autograft and the allograft methods. For instance, since the grafts alone, used in the above graft methods, cannot offer stability large enough to endure the spinal marrow, an internal fixing method needs to be conducted concurrently. In this case, metal fixing means is used, requiring a more complicated surgical operation. In addition, the operator must repeatedly trim the graft into a precise size to fit into a targeted bony tissue, which results in extending the time it takes for the surgical operation. Further, in general, a smooth surface of a graft cannot provide a frictional force necessary for the graft to fix between adjacent bony tissues. Thus, the trimming always has the danger that the trimmed graft might slip out of the bony tissues, breaking the structure of the grafted bony tissue and causing damage to the nerve system and the vascular system near the bony tissue.
In order to circumvent these problems, active research has been directed to the development of bone graft substitutes which possess the excellent biomechanical properties of metal grafts and the superb biological properties of bone grafts, simultaneously as well as have not the disadvantages of the metal and bone grafts. As a result, various spinal marrow grafts which are comprised of hydroxyapatite and bovine collagen have been developed and are commercially available. In addition, such research has elicited the development of bioactive substitutes for cellular expression of the osteoanagenesis which is amplified in a cascade manner within cytoplasm, leading to the develo
Chae Soo Kyung
Kim Hong Yeoul
Lee Chang Hun
Lee Ho Yeon
Seo Kang Moon
Bachman & LaPointe P.C.
Choi Frank
Dees Jose′ G.
Kyung Won Medical Co., Ltd.
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