Dentistry – Apparatus – Having means to emit radiation or facilitate viewing of the...
Reexamination Certificate
2001-04-26
2003-01-28
Manahan, Todd E. (Department: 3732)
Dentistry
Apparatus
Having means to emit radiation or facilitate viewing of the...
Reexamination Certificate
active
06511317
ABSTRACT:
TECHNICAL FIELD
The present invention relates to photocurable dental compositions generally and more particularly to a hand-held device with a single convergent lens having an axis defined by its focal points wherein a light emitting diode is mounted in the assembly at a position laterally offset from the axis of the lens.
BACKGROUND
Certain polymeric materials useful in the field of dentistry for adhesion, sealing and restoration may be cured or hardened upon exposure to a source of radiation. Such photoactive materials are known as “photo-curable dental compositions” and generally harden when exposed to radiation having wavelengths in the visible range. Photo-cured dental compositions are convenient for use by a dentist because the curing process can be initiated when the dental composition has been accurately placed in its proper position. A source of radiation energy positioned proximate to the material to be hardened, for example an appropriate amount of composition placed inside a tooth cavity, is activated to initiate polymerization and subsequent curing of the composition to secure the repair. Early methods for curing photosensitive dental compositions included dental guns and other apparatuses for producing concentrated beams of UV radiation. See U.S. Pat. Nos. 4,112,335 and 4,229,658, for example. Later, visible-light curable dental compositions were used and dental radiation guns for producing concentrated visible light were provided like that disclosed in U.S. Pat. Nos. 4,385,344 and 6,171,105. However, a relatively high divergence about 25 degrees of the light beam from such visible light sources reduces penetration into the tooth structure, leading to their relative inefficiency and unreliability for photo-curing dental composition that are thicker than about two millimeters.
Photo-curable dental materials have also been developed that are hardened by exposure to radiant energy in a pre-selected spectral range. Typically, a photo-activated chemical reaction in many photo-curable dental materials is initiated by application of a high intensity blue light having a wavelength of 400-500 nanometers. Since the light sources employed typically produce the entire visible light spectrum as well as some non-visible radiation, a reflector is coated to reflect only visible light, and the filters are selected to substantially block non-visible radiation and visible light other than blue light in the range of 400-500 nanometers, in order to produce the desired range of radiation, as shown for example in U.S. Pat. No. 5,147,204. Other high power arc sources, such as the one disclosed in U.S. Pat. No. 5,879,159, produce filtered wavelengths in the 430-505 nanometer range. Laser based radiation sources have also been employed, using for example, an argon-ion laser producing either specific wavelengths or their combinations in the 450-514 nanometer range. See U.S. Pat. No. 5,616,141. U.S. Pat. No. 6,099,520 discloses a portable, cordless, hand-held device that uses a diode-pumped microchip laser emitting radiation at 480 nm.
There are several disadvantages in using light curing apparatuses of the prior art like those discussed above. Commercially available dental light guns that use metal halide or plasma ark lamps often include an elongated, slender light guide such as a bundle of optical fibers having a free end that can be positioned close to the photo-curable material in order to direct light to the material from a light source located outside the oral cavity. The bundle of optical fibers is an added component that reduces the efficiency of the light reaching the curing site. Thus, because of the relatively large size of the dental gun within a patient's mouth, a degree of physical discomfort is introduced to the patient as well as to the dentist who must hold the gun steady for about one minute. These sources produce all visible and some non-visible wavelengths and use band pass filters to admit wavelengths of interest. The result is a heating of the device that must be cooled using a cooling fan or other means.
Second, the area illuminated by conventional blue-filtered metal-halide radiation is usually in the range of about a ½-inch diameter circle and over a typical curing cycle of about 60 seconds. The relatively high energy output and beam divergence of such dental guns leads to the possibility of increased heating of the pulp tissue which is sensitive to small changes in temperature.
The argon laser sources are bulky and transport of laser light from the argon laser source to the curing site can only be accomplished by a long fiber-optic delivery system. The technology of either the argon laser or the diode-pumped microchip laser is complex and prevents inexpensive implementation. Their maintenance and repairs are also expensive Lasers are intrinsically inefficient devices meaning that a very small portion of the electrical energy is finally converted to useful light. Furthermore there is the danger of accidental exposure of coherent laser radiation to the eye of either the dentist or the patient during the dental procedure resulting in a damage that could be greater than that resulting from incoherent radiation.
In addition, when dental compositions are cured in place within a cavity for instance, after curing an amount of shrinkage of about 2.5-3.0% occurs leaving a gap within the area being treated; such shrinkage is so deleterious that any small reduction in shrinkage is desirable.
Furthermore, in tests of cure depth uniformity of standardized compositions, it was found that a high percentage (46%) of curing lights used in private dental offices are unsuitable for use when tested against manufacture's recommendations using a curing radiometer or a heat radiometer, due in part to the loss of output of the light source in use [J Dent 1999 Mar; 27(3):235-41]. Finally, due to the expenses of combining a laser or metal-halide radiation source, focusing elements, power sources, etc., significant expense are involved in purchasing and using dental guns. Conventional dental curing devices are therefore seen to have shortcomings including uncomfortable use, unreliable curing and relatively high expense.
U.S. Pat. No. 4,385,344 discloses a dental gun device for production of light in the low visible range for photo-curing dental compositions, the device comprising a tungsten halogen lamp with a concentrating reflector, which reflects visible light and passes middle and far infrared wavelengths. A dichroic heat reflecting filter which passes light from 400 to 700 nm and reflects energy in the visible red and near infrared wavelengths back to the lamp envelope, enhances lamp halogen cycle efficiency. The dichroic heat-reflecting filter is followed by a dielectric filter, which provides a high efficiency bandpass at the desired visible range. A fiber optic light guide is positioned to receive the focused and filtered light and to transmit it to a reduced surface light-applying tip at the end of the handpiece. The fiber light guide is encased in a specially designed sheathing, which provides protection to the optical fibers and carries two electrical conductors which are connected between a control switch on the handpiece and the power supply for the lamp.
U.S. Pat. No. 5,147,204 is representative of conventional blue-light filtered dental guns. This patent discloses a blue light emitting apparatus for curing photo-curable dental material including a handpick having a housing, a depending handle and a detachable light guide. The light guide is received in a head connected to the housing. A source of tungsten-halogen light is coupled to the housing, and a light guide is detachably connected to the head for communication with the source of light. Since the tungsten-halogen light produces the entire visible light spectrum as well as some non-visible radiation, a reflector is coated to generally reflect only visible light, and a blue-pass filter and a heat filter are selected to substantially block non-visible radiation and visible light other than blue li
Melikechi Noureddine
Pradhan Ranjit D.
Ferrell Michael W.
Manahan Todd #E.
New Photonic, LLC
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