Dentistry – Apparatus – Having means to emit radiation or facilitate viewing of the...
Reexamination Certificate
2000-03-31
2001-12-04
Manahan, Todd E. (Department: 3732)
Dentistry
Apparatus
Having means to emit radiation or facilitate viewing of the...
Reexamination Certificate
active
06325623
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to a dental light curing device, and more particular, to a multi-functional dental light curing device that can be used for curing and detecting oral abnormalities by viewing fluorescence emissions from oral disease sites to assist in the diagnosis of the site.
2. State of the Art
The light curing technique has been used in dentistry for many years. In fact, every dental office has at least one dental light curing device because light cured composite fillings are considered the best in the dental industry. A number of different designs of dental light curing devices have been proposed. A typical dental light curing device comprises a hand-held device which includes an enclosure with a light source, focusing optics, delivery optics and an attenuation filter. The light source is typically a halogen or metal halide lamp with a power from 30 to 100 watts. The focusing optics concentrate the lamp emission on the delivery optics which is typically a fiber optic bundle or a glass rod. The dental composite materials are cured under the blue-green light (wavelengths from 400 up to 520 nm, maximum close to 460 nm). For this reason, the focusing and delivery optics can cut the red and infrared emission that is generated by the polychromatic light sources mentioned above and can overheat the tooth. Instead of a lamp, powerful light emitting diodes can be used. The minimum light intensity required at the distal output end of the delivery optics is 200 mW/cm
2
; however, the desirable light intensity is twice as high, about 400 mW/cm
2
. The delivery optics is applied to the tooth by its distal output end and illuminates the tooth until the composite filling is cured (typically about one minute). Due to the high intensity of the light delivered to the tooth and high light scattering in the tooth, strongly reflected and scattered back light is suppressed an the attenuation filter. This suppression is provided in order not to overexpose the dentist's eyes to the blue-green light. The attenuation filter is located around the delivery optics. Typically, it is made of orange-red plastics that intensively absorbs the blue-green light while still making the contact zone viewable for the dentist.
Therefore, the prior art uses the powerful light from the dental curing device for strengthening dental materials only. It is useful to expand the functionality of the dental light curing device by adding the possibility to detect neoplastic abnormalities in a patient's oral cavity during the regular observation by the dentist. Such abnormalities include dysplastic or malignant lesions that are typically undetectable with white light illumination, particularly in their early stages. Dentists are instructed to perform a regular visual examination of patient's oral cavity. During such examination, the dentist examines the patient's gingiva, tongue, buccal mucosa, floor, palate, and labial mucosa paying attention to signs such as leukoplakia (white lesions) or erythropakia (red lesions) that could be precursors to cancer. Unfortunately, often such precursors became visible in the later stages of cancer when a radical means is required (surgery, chemo-or-radiotherapy) or the disease is already noncurable. It has been proven that early detection of neoplastic changes may have the greatest potential for improving a patient's quality of life and survival rates.
A fluorescence technique is able to detect neoplastic lesions in epithelial tissue in the very early stages. The prior art proposed for fluorescence tissue differentiation used special powerful light sources, such as lasers, high pressure mercury lamps, xenon lamps, etc. It often requires special conditions (cooling, ventilation) and space, is expensive, and thus, is not suitable for a regular dental office. Another prior art is based on selective accumulation of certain dyes in the neoplastic lesions, such as toluidine blue. The dye is applied to the tissue by rinsing the oral cavity. However, this prior art is still not used in dental practice because the visibility of the stained thin lesions in the oral cavity is very low, particularly, when early small lesions must be diagnosed. At the same time, toluidine blue has an intensive fluorescence emission in the red range of the visible spectrum. Also, a variety of photosensitizers have been developed to enhance the contrast between the fluorescence of abnormal and normal tissue. The tissue is sensitized by injection of the photosensitizer or by its topical application. However, this prior art also requires special light sources with maximum light intensity at the absorption band of the photosensitizer and a specific imaging technique. This requirement prevents use of such prior art in dental practice mainly due to the price.
The present invention aims to overcome the difficulties with detecting the oral abnormalities mentioned above by expanding the functionality of the existing dental technique.
SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to expand the functionality of the existing dental light curing devices by adding the possibility to detect neoplastic lesions in oral cavity by fluorescence means.
It is another object of the invention to provide the detection of neoplastic lesions in oral cavity by a dental light curing device and fluorescent dyes applyed to the oral cavity.
It is also an object of the invention to provide better viewing conditions while observing the oral cavity with the dental light curing device.
The foregoing objects of the invention are achieved by adding an optical assembly to the distal output tip of the dental light curing device. The assembly provides filtration of the output light at the desirable spectral range. Preferably, this range is from 400 to 480 nm if an autofluorescence (native fluorescence) is used. If any fluorescent dye or photosensitizer is applied (stimulated or induced fluorescence), the filtered range corresponds to the long wavelength maximum absorption of the dye. The optical assembly is applied to the surface of the oral cavity (mucosa, tongue, gingiva). The fluorescence light from the tissue is observed by the dentist through a long pass filter. Preferably, this filter is applied to the existing attenuation filter that suppresses short wavelength light. The filter blocks all light having wavelengths shorter than 520 nm, in case of native fluorescence, and shorter than a specific wavelength that corresponds to a maximum fluorescence emission for fluorescence stimulated with a dye. Preferably, the fluorescent dyes are toluidine blue (maximum absorption around 620 nm, fluorescence from 640 nm), dihematoporhyrin ether or Photofrin (maximum absorption around 630 nm, fluorescence from 640 nm), 5-aminolevulenic acid (the same wavelengths as for Photofrin), hypericin (maximum absorption around 590 nm, fluorescence from 610 nm), fluorescein (maximum absorption around 450 nm, fluorescence from 520 nm).
The tissue emits fluorescence due to endogenous fluorophores existing there. The amount of these fluorophores is different for normal tissue and a neoplastic lesion (dysplasia or malignant lesion). This provides a difference in the fluorescence spectra; typically the fluorescence spectrum from a neoplastic lesion has a shift in the red region (lesion looks reddish in comparison to the light orange background) or it is substantially suppressed (lesion looks darkish under fluorescence even if it is not recognizable under white illumination). The contrast in the fluorescence can be enhanced by applying fluorescent markers or dyes that are able to accumulate in abnormal cells while almost completely releasing from normal ones. Some dyes (such as hypericin, for example) provide so high a fluorescence emission that it can be seen even with a quite bright ambient light.
The illustrations and description below provide more details explaining the present invention.
REFERENCES:
patent: 4666406 (1987-05-01), Kanca, III
patent: 5759032 (1998
Kowalski Pawel
Melnyk Ivan
Rawicz Andrew H.
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