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Processes for forming dental materials and deviceRelated Patent Categories: Dentistry, Apparatus, Having Means To Emit Radiation Or Facilitate Viewing Of The WorkProcesses for forming dental materials and device description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070054234, Processes for forming dental materials and device. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of U.S. Ser. No. 10/185,431, filed Jun. 28, 2002, now U.S. Pat. No. 7,134,875, the disclosure of which is incorporated by reference in its entirety herein. TECHNICAL FIELD [0002] This invention relates to processes for forming dental materials from hardenable dental compositions involving generally sequential hardening. BACKGROUND [0003] Hardenable polymeric materials are used in a wide variety of dental applications, including composites, filling materials, restoratives, cements, adhesives, and the like. Often, such materials shrink upon hardening. This is particularly problematic when the material is in a constrained environment, as in a dental filling or restorative, for example. Dimensional changes upon shrinkage while in a constrained environment can generate a strain within the material that is typically converted into a stress on the surrounding environment (e.g., tooth). Such forces can result in interfacial failures between the tooth and the polymeric material resulting in a physical gap and subsequent microleakage into the tooth cavity. Alternatively, such forces can lead to fractures within the tooth and/or the composite. [0004] Generally, conventional processes of hardening polymeric dental materials involve a composite held in place on an oral surface with an adhesive and involve hardening the adhesive and then subsequently hardening the composite material. More specifically, conventional methods utilize one or more of the following steps: surface treatment of the tooth (e.g., etching, priming), application of a hardenable adhesive to the tooth surface, curing of the adhesive, placement of a composite material (e.g., restorative) on the hardened adhesive, and curing of the composite material. Such methods also typically utilize a blue light source emitting between approximately 380 nm to 520 nm to induce hardening. Photocurable dental compositions are preferably polymerized within a range of about 380 nm to 520 nm for the following reasons: 1) photoactivation utilizing UV photoinitiators or sensitizers (such as benzoin alkyl ethers, acetophenone derivatives, benzophenone and the like) that absorb light at wavelengths less than about 380 nm are generally considered to be unsafe due to the shortwavelength radiation; 2) photoinitiators or photosensitizers (such as eosin dyes, rose bengal, methylene blue and the like) that absorb light at wavelengths greater than about 520 nm are generally unsuitable due to their highly colored nature (red to blue in color) in a spectral region which is esthetically unsuitable for teeth which are generally white to slightly yellow. 3) the preferred sensitizers and initiators for dental compositions which absorb blue light between about 380 nm to 520 nm are typically pale yellow to yellow in color which provides clinically acceptable materials in terms of the esthetics of the hard tissues. Therefore, the practical limitations described have led to nearly exclusive usage of blue light. Thus, there is a need for methods of hardening dental materials, e.g., dental adhesives and dental composites, that reduce the amount of stress placed on the dental material and the surrounding environment during or after hardening. SUMMARY OF THE INVENTION [0005] The present invention provides processes for hardening (e.g., curing by polymerization, crosslinking, ionic reaction, or other chemical reaction) hardenable compositions involving a generally sequential hardening of the compositions. Such processes are particularly useful in dental applications, such as dental sealants, dental adhesives, dental cements, dental composites, dental restoratives, and dental prostheses, for example. The processes of the present invention typically result in a reduction in the amount of stress placed on the dental material and surrounding environment during and/or after hardening of the material. [0006] Generally, the processes of the present invention involve a first step of initiating hardening of a second composition that is in contact with a first composition that is in contact with a dental surface (e.g., tooth surface or bone). Subsequently, either while the second composition is hardening (e.g., polymerizing) or after it is substantially completely hardened, the processes involve a second step of initiating hardening of the first composition. Typically, the hardening steps can be carried out through a chemical curing mechanism or a photopolymerization mechanism, for example. [0007] In one embodiment, the present invention provides a process for forming a dental material adhered to a surface that includes: applying a first hardenable dental composition to the surface, wherein the first hardenable composition includes a first photoinitiator that absorbs radiation within a range of about 380 nm to about 520 nm (blue light); applying a second hardenable dental composition to the first hardenable composition on the surface, wherein the second hardenable composition includes a second photoinitiator that absorbs radiation within a range of about 380 nm to about 520 nm; irradiating the second hardenable composition with radiation within a range of about 380 nm to about 520 nm to selectively harden the second composition; and subsequently irradiating the first hardenable composition with radiation within a range of about 380 nm to about 520 nm to harden the first composition and adhere the second composition to the surface; wherein neither the first photoinitiator nor the second photoinitiator absorbs radiation above about 520 nm. As used herein, "selectively harden" means that the second composition is hardened while the first composition remains substantially unhardened. [0008] In certain embodiments, the first hardenable composition is a dental adhesive and the second hardenable composition is a dental composite. In certain embodiments, the surface is an oral surface, typically a surface of a tooth or bone. In certain embodiments, the first photoinitiator is a phosphine oxide and the second photoinitiator is a diketone. Preferred phosphine oxides are acyl and bisacyl phosphine oxides, with the more preferred being bisacyl phosphine oxides. The photoinitiators of this invention preferably absorb light between about 380 to about 520 nm and are either nearly colorless, pale yellow, or yellow in coloration. [0009] Examples of phosphine oxides include the acyl phosphine oxides of the formula: (R.sup.1).sub.2P(.dbd.O)C(.dbd.O)R.sup.2 wherein: each R.sup.1 is individually a hydrocarbyl group, wherein optionally two R.sup.1 groups can be joined to form a ring along with the phosphorous atom; and each R.sup.2 is independently a hydrocarbyl group, an S--, O--, or N-containing five- or six-membered heterocyclic group, or a -Z-C(.dbd.O)P(.dbd.O)(R.sup.1).sub.2 group, wherein Z represents a divalent hydrocarbyl group. [0010] Examples of phosphine oxides also include the bisacyl phosphine oxides of the formula: R.sup.1P(.dbd.O)(C(.dbd.O)R.sup.2).sub.2 wherein: R.sup.1 is a hydrocarbyl group; and each R.sup.2 is independently a hydrocarbyl group, an S--, O--, or N-containing five- or six-membered heterocyclic group. [0011] In another embodiment, a process for forming a dental material adhered to an oral surface includes: applying a hardenable dental adhesive to an oral surface, wherein the hardenable adhesive includes a first photoinitiator that absorbs radiation within a range of about 380 nm to about 450 nm; applying a hardenable dental composite to the hardenable dental adhesive on the oral surface, wherein the hardenable dental composite includes a second photoinitiator that absorbs radiation within a range of about 450 nm to about 520 nm; irradiating the hardenable dental composite with radiation within a range of about 450 nm to about 520 nm to selectively harden the hardenable dental composite; and subsequently irradiating the hardenable dental adhesive with radiation within a range of about 380 nm to about 450 nm to harden the adhesive and adhere the dental composite to the oral surface; wherein neither the first photoinitiator nor the second photoinitiator absorbs radiation above about 520 nm. [0012] In yet another embodiment, a process for forming a dental material adhered to an oral surface includes: applying a hardenable dental adhesive to an oral surface, wherein the hardenable dental adhesive includes a phosphine oxide that absorbs radiation within a range of about 380 nm to about 450 nm; applying a hardenable dental composite to the hardenable dental adhesive on the oral surface, wherein the hardenable dental composite includes a diketone that absorbs radiation within a range of about 450 nm to about 520 nm; irradiating the hardenable dental composite with radiation within a range of about 450 nm to about 520 nm to selectively harden the dental composite; and subsequently irradiating the hardenable dental adhesive with radiation within a range of about 380 nm to about 450 nm to adhere the dental composite to the oral surface; wherein neither the first photoinitiator nor the second photoinitiator absorbs radiation above about 520 nm. [0013] Each of the above embodiments includes at least two compositions, each of which includes at least one photoinitiator. Other embodiments in which only one or no photoinitiators are used are also included within the scope of the present invention. [0014] In one such embodiment, the present invention provides a process for forming a dental material adhered to a surface that includes: applying a first hardenable dental composition to the surface; applying a second hardenable dental composition to the first hardenable dental composition on the surface; and hardening the first and second hardenable dental compositions to adhere the second composition to the surface, wherein the second hardenable composition is substantially completely hardened prior to complete hardening of the first hardenable composition; wherein at least one of the first or second hardenable compositions is chemically hardenable. [0015] In another embodiment, the present invention provides a process for forming a dental material adhered to an oral surface that includes: applying a hardenable dental adhesive to the oral surface; applying a hardenable dental composite to the hardenable dental adhesive on the oral surface; and hardening the hardenable dental adhesive and hardenable dental composite to adhere the composite to the surface, wherein the hardenable dental composite is substantially completely hardened prior to complete hardening of the hardenable dental adhesive; wherein at least one of the hardenable adhesive or hardenable composite is chemically hardenable. [0016] The present invention also provides devises that can be used to harden dental compositions, such as those of the present invention. In one embodiment, there is provided a dental composition hardening light that includes: a housing; a first light source located within the housing, the first light source emitting light in a first wavelength range; a second light source located within the housing, the second light source emitting light in a second wavelength range; and a controller operably connected to the first light source and the second light source, the controller controlling emission of light from the first light source and the second light source. Processes of hardening dental compositions using such lights are also encompassed by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS [0017] FIG. 1 is a perspective view of one illustrative device according to the present invention. [0018] FIG. 2 is a block diagram of components in one illustrative hardening device according to the present invention. [0019] FIG. 3 is a block diagram of components of another illustrative hardening device according to the present invention. Continue reading about Processes for forming dental materials and device... Full patent description for Processes for forming dental materials and device Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Processes for forming dental materials and device patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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