Dentistry – Apparatus – Having means to emit radiation or facilitate viewing of the...
Reexamination Certificate
2000-11-15
2002-11-26
Lucchesi, Nicholas D. (Department: 3732)
Dentistry
Apparatus
Having means to emit radiation or facilitate viewing of the...
Reexamination Certificate
active
06485300
ABSTRACT:
This invention relates to a novel apparatus for the detection of biological deposits, in particular deposits of plaque, on the surfaces of teeth. In particular the invention relates to apparatus for this purpose which use fluorescence measurements to detect such deposits. In particular the invention relates to apparatus for this purpose which may be incorporated in a hand- or electrically operated toothbrush.
The term “biological deposits” used herein refers generally to deposits of material of biological origin, e.g. plaque, bacteria, tartar, calculus etc. which are generally regarded as undesirable for dental hygiene. Dental plaque is a complex organic deposit generated in part by the activity of bacteria on the teeth or contamination, e.g. food deposits on the teeth, and is an undesirable precursor to tooth decay and the development of dental caries.
It is desirable to detect such deposits on the teeth before removing them, for example by toothbrushing, as detection indicates the areas at which dental cleaning effort should be concentrated. Such deposits can be difficult to detect in situ in vivo on the teeth. It is especially important to detect dental plaque. For detection of plaque it is known to use fluorescence measurement. In the state of the art there are two general methods for detecting dental plaque using fluorescence, secondary fluorescence and auto fluorescence. In secondary fluorescence teeth suspected of bearing plaque are treated with a fluorescent label material which preferentially binds to dental plaque, and after excess of the unbound material has been washed away from the teeth, the fluorescence emission, in response to illumination by exciting radiation, of the label material at areas of the tooth at which it has bound to plaque is detected to indicate the presence of dental plaque. WO 92/06671 and WO 25 97/01298 disclose typical methods based upon secondary fluorescence and apparatus which exploit such methods.
Auto fluorescence methods do not use a fluorescence label but instead detect the fluorescence emission from dental plaque itself in response to illumination by exciting radiation. U.S. Pat. No. 5,382,163, DE 29704185, DE 29705934, EP 0774235, and also WO 97/01298 disclose methods of this type and apparatus for performing these methods. Typically in these disclosures auto fluorescence emission by dental plaque at emission wavelengths above ca. 600 nm is detected and associated with the presence of dental plaque.
Optical methods are also known for the detection of dental caries, i.e. the tooth disease which can result from the non removal of plaque. Typical methods of this type are disclosed in for example U.S. Pat. No. 4,290,433, EP 0862897 and WO 97/42869, but these methods do not detect plaque deposits themselves.
These methods and apparatus disclosed in the state of the art for the detection of plaque have not proved to be optimum, especially when there is relatively little plaque present—a state at which tooth cleaning is best carried out to remove early deposits of plaque before they can build up. Plaque deposits have different characteristics which vary from person to person, so it is desirable to provide a system which can be “personalised”. Methods which require the application of fluorescent label materials to teeth are prima facie inconvenient.
It is therefore an object of this invention to provide an apparatus and a method for detecting biological deposits on teeth in vivo, which in part at least solves the problems of the state of the art.
According to a first aspect of this invention, an apparatus for detecting biological deposits on the surface of a tooth comprises;
illumination means to direct exciting radiation onto a test tooth surface,
detection means to detect fluorescence emission from the test tooth surface at a wavelength associated with that of auto fluorescence emission from a substantially biological deposit-free tooth surface,
means to make a comparison of the intensity of the said fluorescence emission from the test tooth surface with an intensity of auto fluorescence emission, at a wavelength associated with that of auto fluorescence emission from a substantially biological deposit free tooth surface, from a tooth surface known to have less biological deposit thereon than is present at the test tooth surface,
means to associate the comparison thus obtained with the presence of biological deposits on the test tooth surface, and,
indicator means to indicate the presence of such biological deposits to a user of the apparatus.
The test tooth surface may be any tooth surface in the user's mouth which is believed or suspected to have a biological deposit such as plaque thereon, or which the user desires to test for the presence of plaque, usually with the intention of removing such deposits e.g. using a toothbrush.
For convenience a tooth surface known to have less biological deposit thereon than is present at the test tooth surface is termed hereafter a “clean” tooth surface. A clean tooth surface may have biological deposit thereon but quantitatively less than is present at the test tooth surface, or preferably is free or substantially free of biological deposit.
The apparatus of this aspect of the invention is based upon the discovery that a tooth surface which is free of biological deposit, when illuminated with exciting radiation, emits a strong and easily detectable auto fluorescence emission, generally peaking in intensity at ca. 450 nm, but having a considerable intensity at higher wavelengths, and that this auto fluorescence emission is strongly attenuated by the presence of even small quantities of biological deposits such as dental plaque on the tooth surface, so that the intensity of this auto fluorescence is reduced if biological deposits are present on the tooth surface. It has also been discovered that this characteristic auto fluorescence is relatively unaffected by other features of the tooth surface, for example the colour or natural reflectivity of the teeth whether due to natural variations, age, sex, deposits from tobacco smoking etc. so that the apparatus and the method it employs are sufficiently unaffected by variations between the teeth of individual persons using the apparatus. Also the majority of commercial toothpastes are believed to emit no fluorescence in response to illumination by radiation which causes fluorescence emission from tooth surfaces or biological deposits thereon, and to differ in their spectra from natural enamel, so are not believed to interfere with the operation of the device of this invention.
Although for the purpose of exciting fluorescence a preferred wavelength for the exciting radiation is below 420 nm, radiation of this, short wavelength may in some circumstances be harmful to dental tissues. Consequently for safety reasons the exciting radiation is preferably at a wavelength 470±40 nm. Suitable and preferred illumination means are discussed in more detail below.
A tooth surface free of biological deposits emits a fluorescence emission in the wavelength region above 420 nm, typically as shown in
FIG. 1
, peaking in intensity above ca. 450 nm. Therefore the detection means may detect the fluorescence emission at such wavelengths above 420 nm.
Suitably, inter alia to differentiate the exciting radiation from the fluorescence emission, the detector means detects fluorescence emission radiation at a wavelength of above 520 nm. At these wavelengths the auto fluorescence emission from the surface of teeth which are free or substantially free of biological deposits is still strong. It is preferred to measure the fluorescence emission radiation at a wavelength above ca. 530 nm, for example over the region 530-630 nm.
The means to make the comparison of the relative intensities of the auto fluorescence emission from the test tooth surface with that from a clean tooth surface may comprise an electronic signal/data processing system processing an electronic signal corresponding to the auto fluorescence emission. Preferably the system measures the area under the inten
Muller Werner
Schopplein Michael
Helmut Hund GmbH
Lucchesi Nicholas D.
Stein-Fernandez Nora
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