Stabilizers for polymerizable biocompatible materials

Abstract

The present invention provides polymerizable biocompatible materials stabilized by amino acids or reducing salts to improve shelf life. Methods of stabilizing a polymerizable biocompatible material are also provided that inhibit auto polmerization of the material over time.

Description

FIELD OF THE INVENTION [0001] The present invention relates to stabilizers for polymerizable biocompatible materials and polymerizable biocompatible materials with stabilizing amounts of amino acids or reducing salts. Also provided are methods of stabilizing such materials. BACKGROUND OF THE INVENTION [0002] The need for biomaterials in orthopaedic and dental applications has increased as the world population ages. A significant amount of research into biomaterials for orthopaedic and dental uses has attempted to address the functional criteria for orthopaedic and dental reconstruction within the human body. Biomaterials useful for orthopaedic and dental reconstructions must have high strength, must be able to be immediately affixed to the situs for reconstruction, must bond strongly to bone, and must give rise to strong, highly resilient restorations. [0003] Among the materials used for orthopaedic and dental restorative purposes are bone cements based upon acrylic species such as ...

AI Technical Summary

Benefits of technology

[0013] In some embodiments, stabilizers, such as an amino acids or reducing salts, are added to polymerizable orthopedic compositions in order to improve their shelf life. It is believed that the stabilizer acts as an oxygen scavenger, reducing the degradation of amines and accelerators without affecting constituents of the composition that allow for proper polymerization of the composition. The stabilizers of the present invention also help prevent further degradation of aged material and inhibit auto polymerization of the material over time while maintaining properties such as degree and rate of functional group conversion upon curing.

[0016] The present invention also provides stabilizers for orthopaedic compositions that are non-toxic and may enhance the biocompatibility of these materials. Amino acids are naturally occurring in the body. Their presence may influence the growth of bone when near or adjacent to an orthopedic composition.

[0027] The filler may be comprised of an inorganic or organic material, which may be bioactive. In certain embodiments, the filler is comprised of an inorganic material. The filler added to the paste enhances the mechanical or the rheological properties of the paste composition. Examples of suitable fillers include, but are not limited to, barium glass, barium-boroaluminosilicate glass, sodium borosilicate, silica, 45S5 glass, bioactive glass, ceramics, glass-ceramics, bioactive synthetic combeite glass-ceramic, e-glass, s-glass, iron phosphate, or combinations thereof. The filler or fillers are generally pre-dried prior to blending with other fillers. One or more fillers can be coated with silane prior to sterilization.

[0029] Relatively low viscosity, syringable pastes are suited for the filling of bony defects, fracture repair, and implant fixation and revision. Syringable pastes flow to fill voids, and crevices, and adhere tightly to the surface of the bone, tissue, or implant. Rheology can be important for tight adherence and removal of micromotion when implant securing is being achieved. The lack of implant motion can reduce inflammation and determine the success of the implant system over time. Higher viscosity pastes are desirable for larger, load bearing bone defects and easily accessible fracture sites. A putty can be manipulated, sculpted and cured in place with immediate high strength capability. Oncological bony defects are well suited for highly loaded, highly bioactive composites. The use of hand mixed pastes can also facilitate the addition of medicaments, antibiotics, or bone growth factors.

[0036] Plasticizers may be added to the composition to facilitate processing and increase the flexibility of the final product. Examples of plasticizers include TEGDMA, hydroxyethyl methacrylate (HEMA), and phthalates such as diethyl phthalate, benzylbutyl phthalate, dibutyl phthalate, and dibenzyl phthalate.

Problems solved by technology

In general, however, the materials that are added to the composition to initiate polymerization under room temperature conditions, such as peroxides, photoinitiators, other free radical generators (azo compounds, persulfates, phosphines, etc.), and certain reducing agents (amines, ascorbates, metal salts, etc.) can prematurely initiate polymerization.

Decomposition can result if the materials are stored too long or exposed to heat and / or light.

However, oxidation of the accelerating agents decreases the efficiency of the system and ultimately can result in the failure of the system to polymerize upon mixing.

Unfortunately, the addition of most commercial antioxidants will further inhibit polymerization.

Hallock does not teach the use of these amino acids alone or without the aid of hydrotalcite to stabilize polymerizable materials.

However, it is not used to stabilize and prolong the shelf life of a polymerizable system.

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