Dentistry – Apparatus – Having means to emit radiation or facilitate viewing of the...
Reexamination Certificate
1998-01-20
2001-03-13
Lewis, Ralph A. (Department: 3732)
Dentistry
Apparatus
Having means to emit radiation or facilitate viewing of the...
C433S215000, C606S113000, C362S800000
Reexamination Certificate
active
06200134
ABSTRACT:
FIELD OF THE INVENTION
This application is related to the curing of materials with radiation and, more specifically, to curing dental coating and filling compounds with light.
BACKGROUND OF THE INVENTION
Curable adhesive compounds and bonding or filling compounds are widely used for structurally connecting object surfaces together or for filling gaps or other openings and cavities in an object surface. Such curable compounds are generally manipulated and positioned in a semi-solid state and are then hardened or cured in position to a more solid state. Such curing or hardening is a chemical process which is promoted and driven by one or more curing conditions or factors. For example, the curing process may be the result of exposure of the semi-solid compound and components thereof to air or from exposure of such a compound and its components to an energy source, such as a heat source.
Other curable adhesive and filling compounds are cured by exposure to radiated energy, such as visible light energy. Such compounds, referred to as light-curable compounds, are manipulated in a semi-solid form into or onto the work surface and radiation, preferably in the form of a visible light beam, is directed at a specific wavelength or band of wavelengths onto the compound. The compound includes light-sensitive chemical components therein which, when exposed to the light at the specific wavelength, promote the hardening of the compound in the desired position on the object surface to bond, fill, or coat the surface.
Specifically, light-curable compounds are widely used in dental procedures. Dentists use light-curable dental compounds for coating and sealing tooth surfaces, filling caries and other cavities in the tooth surface, and securing crowns and various other dental structures to a tooth surface. The dental compounds are generally cured by exposure to visible light in the blue range of the spectrum. Once cured, the dental compound reduces further tooth decay, bonds the dental structure, and/or provides additional structure to a tooth.
For curing light-curable dental compounds, visible blue light, and particularly a blue light beam from a hand-held curing light device, is directed onto a tooth surface containing the desired compound layer. The blue light penetrates into the compound layer on the tooth surface for complete curing. The duration of the exposure to blue light for proper curing of the compound layer depends upon the type and thickness of the compound layer, as well as the power and characteristics of the blue light from the curing light device. For example, a thin tooth surface coating or veneer will require less radiated light power, while thicker, deeper fillings for caries and other cavities will require a greater amount of radiated power.
Light-curable compounds have shown very beneficial results in the dental field. However, existing techniques and dental curing light devices utilized to deliver the blue light to the tooth surface have exhibited various drawbacks. For example, it is known that certain wavelengths of blue light are harmful to human tissue. While attempts are made to direct the light beam only on to the tooth surface, a certain amount of oral tissue exposure to the light is inevitable. Therefore, curing light devices for curing dental compounds must have their output radiation limited to within a suitable wavelength band for patient safety. Furthermore, the light-curable compounds are usually sensitive to light having a specific wavelength, such as a blue light wavelength. Therefore, a dental curing light device must be tuned to emit light at the proper wavelengths for patient safety and proper curing.
As a result, current dental curing light devices require special complicated filtering devices or filters which receive broad spectrum light from a lamp element, such as a halogen lamp bulb, and then filter the light to provide only the light at the desirable blue wavelengths. Because of the wide spectrum of radiation delivered by available lamp elements, including visible light, UV light, and infra-red light, prior art curing techniques and light devices have generally been very inefficient. That is, a large amount of the radiated light power is lost due to filtering. For example, the input power to a conventional halogen bulb may typically be around 80 Watts, whereas the output power of light from the dental light device at the desired blue wavelength, for example 400-500 nanometers, is typically less than one-half of a Watt.
Additionally, the efficiency of the prior art dental curing light devices is further degraded by the power loss due to the angle of incidence of the radiated light upon the filtering element. For example, many prior art curing light devices utilize reflective filters which reflect only the desirable blue light onto the tooth surface and dental compound, but transmit light at the undesirable wavelengths to a light absorbing component where it is dissipated. If the angle of incidence of the light from the halogen bulb varies significantly from the desired angle of incidence for the filtering element surface (e.g., 45°), then a reduced amount of the desirable blue light is reflected to the tooth surface. This further decreases the light power which is available for curing the dental compound. Conversely, a higher amount of the undesirable, non-blue light may be reflected onto the tooth surface, rather than being transmitted through the filtering element to be dissipated.
Another drawback with prior art devices is that they require complicated cooling systems to operate within the proper temperature range. The significant amount of light energy at undesirable wavelengths which is generated by the halogen bulb must be filtered or otherwise captured. The captured energy is then dissipated in the form of heat. Therefore, power absorbing and dissipating elements are required within conventional curing light devices. Thermal shields are often utilized in conjunction with reflective filters to absorb and dissipate the unreflected, unused light energy in the form of heat. The high power output required for the halogen bulb to produce the desired blue light power for curing, creates a significantly, high thermal load on the shields. The shields must then be cooled. Generally, fan elements are used in the dental light device to provide such cooling. The additional cooling elements increase the size of the light device and complicate its design. As will be appreciated, it is desirable to keep the light device as small and maneuverable as possible, since it is used in a patient's mouth.
Additionally, a thermal load is placed on the reflective filter element, and it must also be cooled, such as by heat sinks and fans. The absorption devices and heat dissipating systems not only complicate the operation of the light device, but also make it more expensive to produce, and more subject to operational failure.
Another drawback of prior art dental curing light devices is the limited operational life of the lamp element, such as a halogen bulb. The bulbs frequently burn out and must be replaced. Furthermore, the heat generated inside the light device shortens the effective operational lifespan of the bulb.
Attempts have been made in the prior art to address some of these drawbacks. For example, Japanese Patent Applications No. 6-30275, 6-285508, 7-163863, and 8-194786 disclose various devices using solid state semiconductor elements, such as LEDs, to provide a curing light source in the blue range. However, various of these devices require complicated internal designs for focusing of the curing light. Furthermore, as illustrated in the Figures of those applications, the solid state elements utilized would require a somewhat large housing for generating the intensity of light which is necessary for practical use.
Accordingly, it is an objective of the present invention to provide a simple, durable curing light device for hardening or curing light-curable compounds. Particularly, it is an objective to provide such a curing light device for curing denta
Knox Raymond L.
Kovac Jozef
Kerr Corporation
Lewis Ralph A.
Wood Herron & Evans L.L.P.
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