Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-12-10
2002-02-19
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C525S300000
Reexamination Certificate
active
06348518
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
Embodiments of the present invention relate in general to compositions and methods useful in the preparation of an artificial prothesis, whether for medical, dental or cosmetic use. Embodiments of the present invention are more particularly directed to compositions which include ester compounds having high solvency and low volatility.
2. Description of Related Art
Materials science has provided a plethora of compositions that can be transformed from an initial, malleable state to a final, non-malleable state, generally through the process of heating, the application of pressure, and/or the inducement of polymerization. Such compositions may be first molded into a desired shape, then subsequently induced to transform into a final, non-deformable shape identical (or nearly so) to the original molded shape. Such processes may employ heat or pressure (or both) to transform materials into a desired shape by manipulation of the physical properties of the material itself, or may alternatively utilize initiators and/or activators to begin a polymerization reaction throughout the shaped mass.
The class of materials known as acrylics (which, for the purpose of this disclosure, shall mean compositions comprised wholly or in part of acrylate and/or methacrylate monomers and/or polymers, alone or in combination with each other and/or other unsaturated and/or saturated compounds) has gained acceptance as being particularly suited for the formation of prosthetics to be placed into contact with the body. In particular, acrylics have been used to form dental restorative materials, dentures, temporary crown and bridge materials, and artificial fingernails and toenails, as well as having been employed as adhesion promoters at the interface between a biological surface (herein defined as any external or internal surface of a living organism) and a prosthetic (in order to provide the extended wear time required of, for instance, a permanent dental restorative material). Curable acrylic compositions, when properly initiated or catalyzed, undergo free-radical addition reaction polymerization, which is exothermic (generates heats) in character.
A large number of acrylic compositions, such as those finding utility as artificial fingernails and dentures, are formulated in separate phases or parts, one or both of the parts containing an element required for polymerization to occur. It is not until the parts are combined that the composition can undergo a polymerization reaction, and the concentration of the polymerization-inducing elements (for instance a free-radical polymerization initiator and a free-radical polymerization promoter) in each part can determine the rate and extent of polymerization for the entire composition. It is often required that the input of heat or light energy is required after combining all of the composition components in order to effect polymerization.
An example of a multi-component composition includes at least one liquid phase and one solid phase, said phases being combined in a specified ratio just prior to being shaped into, for instance, a prosthetic device or object. Upon combining the liquid and solid phases, and, optionally, exposing the resulting mixture to heat and/or light energy, a free-radical polymerization process is induced and proceeds at a rate relative to the concentration of polymerization initiators and/or promoters contained therein. A light-induced polymerization reaction is initiated by exposing the composition to a particular spectrum of light that overlaps that of a photoinitiator contained in the composition.
A particularly intractable problem presented by currently available multi-component compositions comprising a liquid acrylic monomer and a solid polymer stems from the correlation between a liquid acrylic monomer's solvating capabilities and its volatility. While many liquid acrylic monomers possess the ability to quickly absorb and dissolve the solid polymers intended to be used with them to form a prosthesis or other solid object, these same monomers seem to be highly volatile and have objectionable and possibly unhealthy odors. Most monomers with low volatility, such as the C4 and higher methacrylate monomers, tend to lack the solvency characteristics required to adequately dissolve the solid polymer phase of the composition. It has been reported that insufficient solvation of the solid polymer phase results in a finished cured polymer that lacks desirable physical properties, such as high tensile and flexural strength.
On the other hand, monomers with the required solvency characteristics tend to have high volatilities. The most frequently employed monomer for making dentures, methyl methacrylate, is easily detected by smell in a large room containing but a small volume of liquid. Similarly, ethyl methacrylate, the most commonly employed artificial fingernail liquid monomer, is a bane to nail salons due to its characteristic odor that is detectable at extremely low levels in air (methyl methylacrylate can be detected by humans at a concentration of as little as 750 parts per billion in standing air while ethylmethacrylate can be detected by humans at a concentration of as little as 170 parts per billion in standing air).
There have been attempts to provide alternative liquid monomers for the applications described above. Monomers such as methoxyethyl methacrylate, methoxyethoxyethyl methacrylate, ethoxyethoxyethyl methacrylate, tetrahydrofurfuyrl methacrylate, and hydroxyethyl methacrylate have been employed alone or in combination with other monomers in an attempt to provide odorless or low-odor liquid acrylic monomers for multi-component acrylic systems. Methoxyethyl methacrylate is manufactured from methoxyethanol and thus contains it as a toxic impurity. Methoxyethoxyethyl and ethoxyethoxyethyl methacrylate have a better safety profile, but suffer from a relatively low solvating ability compared to liquid acrylic monomers such as methyl and ethyl methacrylate. Tetrahydrofurfuryl methacrylate possesses a distinct and objectionable odor, and is also limited in its solvating ability. Hydroxyethyl methacrylate, in addition to having limited solvating capabilities, is highly hygroscopic in its polymerized form; its water absorption properties can render polymers containing it highly susceptible to physical degradation from hydrolysis.
A need therefore existst to develop compositions including an acrylic monomer which are useful in forming a polymerized prosthesis while avoiding the problems associated with prior art compositions using highly volatile acrylic monomer compounds. A further need exists to provide an acrylic monomer having a high degree of solvency and a low level of odor for use in a multi-component composition that combines a liquid component and a solid component prior to desired use.
BRIEF SUMMARY OF THE INVENTION
Embodiments of the present invention are directed to compositions useful in making an artificial prosthesis, including a medical, dental or cosmetic prosthesis. Embodiments of the present invention are further advantageously directed to methods using monomeric ester compounds capable of polymerization and having low volatility or low or no odor and/or desirable solvation properties with respect to acrylate or methacrylate based polymers in the manufacture of an artificial prosthesis. According to one embodiment of the present invention, a composition is provided which includes one or more of a polymeric compound, a polymerization catalyst, a polymerization promoter, a solvent and a compound of formula I below:
wherein R
1
is hydrogen or C
1
-C
10
straight or branched chain, substituted or unsubstituted, saturated or unsaturated alkyl, R
2
is C
1
-C
10
straight or branched chain, substituted or unsubstituted, saturated or unsaturated alkyl, R
3
is hydrogen or C
1
-C
10
straight or branched chain, substituted or unsubstituted, saturated or unsaturated alkyl. The monomer compounds of Formula I advantageously exhibit desirable solvency and low volatili
Banner & Witcoff , Ltd.
Michl Paul R.
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