(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2007/0021670 A1
`(43) Pub. Date:
`Jan. 25, 2007
`Mandelis et al.
`
`US 20070021670A1
`
`(54)
`
`(76)
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`(21)
`(22)
`
`(60)
`
`METHOD AND APPARATUS USING
`NFRARED PHOTOTHERMAL
`RADIOMETRY (PTR) AND MODULATED
`LASER LUMINESCENCE (LUMD FOR
`DAGNOSTICS OF DEFECTS IN TEETH
`
`Inventors: Andreas Mandelis, Scarborough (CA);
`Stephen Abrams, Toronto (CA);
`Jin-Seok Jeon, Vaughan (CA); Kiran
`Kulkarni, Toronto (CA); Anna
`Mativenko, Toronto (CA)
`Correspondence Address:
`Ralph A. Dowell of DOWELL & DOWELL P.C.
`2111 Eisenhower Ave
`Suite 406
`Alexandria, VA 22314 (US)
`Appl. No.:
`11/488,194
`
`Filed:
`
`Jul. 18, 2006
`
`Related U.S. Application Data
`Provisional application No. 60/699,878, filed on Jul.
`18, 2005.
`
`Publication Classification
`
`(51) Int. Cl.
`(2006.01)
`A6IB 6/00
`(52) U.S. Cl. .............................................................. 6OO/473
`
`ABSTRACT
`(57)
`There is provided a high-spatial-resolution dynamic diag
`nostic instrument which can provide simultaneous measure
`ments of laser-induced frequency-domain infrared photo
`thermal radiometric and alternating-current (ac) modulated
`luminescence signals from defects, demineralization, rem
`ineralization and caries in teeth intraorally. The emphasis is
`on the abilities of this instrument to approach important
`problems such as the detection, diagnosis and ongoing
`monitoring of carious lesions and or defects on the occlusal
`pits and fissures, Smooth Surfaces and interproximal areas
`between teeth which normally go undetected by X-ray radio
`graphs or visual examination. The instrument is also able to
`detect early areas of demineralized tooth and or areas of
`remineralized tooth as well as defects along the margins of
`restorations. This capability of inspecting a local spot can be
`extended to a modulated imaging of Sub-Surface of target
`tooth by using a multi-array infrared camera. Two configu
`rations of the instrument are presented.
`
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`Patent Application Publication Jan. 25, 2007 Sheet 1 of 9
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`US 2007/0021670 A1
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`50
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`18
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`
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`16
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`12
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`20
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`22
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`To laser
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`32
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`14
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`Figure 1
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`Patent Application Publication Jan. 25, 2007 Sheet 2 of 9
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`US 2007/0021670 A1
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`Figure 2a
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`Patent Application Publication Jan. 25, 2007 Sheet 3 of 9
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`US 2007/0021670 A1
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`
`
`PTR amplitude
`
`...
`
`10°
`
`
`
`
`
`
`
`
`
`LUM amplitude
`Aaaaaaaaaa.
`S888&ss
`
`ox ox 688:XXxxxxxx-xx
`
`$ii
`
`Frequency (2)
`
`1000
`
`1
`
`
`
`
`
`Frequency (2)
`
`1OOO
`
`1
`
`1O
`1OO
`Frequency (Hz)
`
`1OOO
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`10
`1OO
`Frequency (Hz)
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`Figure 2b
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`Patent Application Publication Jan. 25, 2007 Sheet 4 of 9
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`US 2007/0021670 A1
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`Figure 3a
`
`
`
`PTR amplitude
`
`10
`
`LUM amplitude
`-- before drilling
`-O- after drilling a hole on left
`-- after drilling a hole on right
`
`
`
`172
`
`Position (mm)
`
`Position (mm)
`
`FIGURE 3b
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`Patent Application Publication Jan. 25, 2007 Sheet 5 of 9
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`US 2007/0021670 A1
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`LUM amplitude
`-H before treating
`-O- after 16hrs
`-A- after 80hrs
`-- after 100hrs
`X- after 170hrs
`
`
`
`|PTR amplitude
`
`10
`
`S.
`o
`
`E
`g
`
`-5
`10
`
`230
`
`22O
`
`1
`210
`
`as
`is 200
`
`190
`
`S.
`o
`
`E
`c
`
`10
`
`118
`
`117
`
`N 116
`Yue
`115
`8
`114
`
`113
`112
`
`Position (mm)
`
`Position (mm)
`
`Figure 4
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`Patent Application Publication Jan. 25, 2007 Sheet 6 of 9
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`0.01
`
`S.
`
`C)
`2
`s
`S 1 E-3
`C
`
`
`
`PTR amplitude
`
`LUM amplitude
`at 5Hz
`# of samples: 14
`treated for 6a720hours
`
`1
`
`10
`
`1OO
`
`1000
`
`1
`
`10
`
`100
`
`1000
`
`175
`
`1
`
`10
`100
`Treating time (hour)
`
`172
`
`1000
`
`1
`
`10
`1OO
`Treating time (hour)
`
`1000
`
`Figure 5a
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`Patent Application Publication Jan. 25, 2007 Sheet 7 of 9
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`1 E-3 PTR amplitude
`
`LUM amplitude
`
`at 500Hz
`# of samples: 14
`treated for 6-720hours
`
`ana
`2
`s
`Os
`3. R
`Ol
`E
`CC
`
`1E-4
`
`1
`
`10
`
`100
`
`1000
`
`1
`
`10
`
`100
`
`1000
`
`PTR phase
`=t-SN.
`
`S
`S-1E-4
`CD
`O
`
`o
`S
`CC
`
`
`
`i
`
`1
`
`10
`100
`Treating time (hour)
`
`1000
`
`1
`
`10
`100
`Treating time (hour)
`
`1000
`
`Figure 5b
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`Patent Application Publication Jan. 25, 2007 Sheet 8 of 9
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`Patent Application Publication Jan. 25, 2007 Sheet 9 of 9
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`US 2007/0021670 A1
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`164
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`162 -
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`160
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`166
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`168
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`Figure 7
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`METHOD AND APPARATUS USING INFRARED
`PHOTOTHERMAL RADIOMETRY (PTR) AND
`MODULATED LASER LUMINESCENCE (LUM)
`FOR DAGNOSTICS OF DEFECTS IN TEETH
`
`CROSS REFERENCE TO RELATED U.S.
`PATENT APPLICATIONS
`0001. This patent application relates to U.S. utility patent
`application Ser. No. 60/699,878 filed on Jul. 18, 2005
`entitled SIMULTANEOUS FREQUENCY-DOMAIN
`INFRARED PHOTOTHERMAL RADIOMETRY (PTR)
`AND MODULATED LASER LUMINESCENCE (LUM)
`APPARATUS FOR DIAGNOSTICS OF DEFECTS IN
`TEETH, filed in English, which is incorporated herein in its
`entirety by reference.
`
`FIELD OF INVENTION
`0002 The present invention relates to an apparatus based
`on laser-frequency-domain infrared photothermal radiom
`etry (henceforth referred to as FD-PTR or simply PTR) and
`frequency-domain luminescence (henceforth referred to FD
`LUM, or simply LUM), for detection of dental defects,
`demineralization and or remineralization of hard tissues,
`defects around restorations and caries intraorally.
`
`BACKGROUND OF THE INVENTION
`0003) Nowadays with the widespread use of fluoride, the
`prevalence of caries, particularly smooth surface caries has
`been considerably reduced, but the development of a non
`invasive, non-contacting technique which can detect and
`monitor early demineralization on or beneath the enamel,
`dentin or root Surface or dental restorations is essential for
`the clinical management of this problem. A novel biother
`mophotonic technique has been introduced, based on the
`modulated thermal infrared (black-body or Planck radiation)
`response of a turbid medium, resulting from radiation
`absorption and non-radiative energy conversion followed by
`a small temperature rise.
`0004 Thus, PTR has the ability to penetrate, and yield
`information about, an opaque medium well beyond the
`range of optical imaging. Specifically, the frequency depen
`dence of the penetration depth of thermal waves makes it
`possible to perform depth profiling of materials. In PTR
`applications to turbid media, such as hard dental tissue,
`depth information is obtained following optical-to-thermal
`energy conversion and transport of the incident laser power
`in two distinct modes: conductively, from a near-surface
`distance (50-500 um) controlled by the thermal diffusivity
`of enamel; and radiatively, through blackbody emissions
`from considerably deeper regions commensurate with the
`optical penetration of the diffusely scattered laser-induced
`optical field (several mm).
`0005 Trends in improved diagnostic capabilities,
`coupled with significantly higher optical damage thresholds
`for tissue, point toward the use of frequency-domain tech
`niques as the next-generation technologies to Supplement or
`replace pulsed laser photothermal or photoacoustic detection
`with due attention to the physics of the photon propagation
`in the scattering medium. The use of laser biothermopho
`tonics for dental diagnostics, detection and ongoing moni
`toring is considered as a promising technique, complemen
`tary to the phenomenon of laser-induced fluorescence of
`
`enamel or to the fluorescence caused by porphyrins present
`in carious tissue R. Hibst, K. Konig, “Device for Detecting
`Dental Caries”, U.S. Pat. No. 5,306,144 (1994). The first
`attempt to apply the depth profilometric capability of fre
`quency-domain laser infrared photothermal radiometry
`(PTR) toward the inspection of dental defects was reported
`by Mandelis et al.A. Mandelis, L. Nicolaides, C. Feng, and
`S. H. Abrams, “Novel Dental Depth Profilometric Imaging
`Using Simultaneous Frequency-Domain Infrared Photother
`mal Radiometry and Laser Luminescence'. Biomedical
`Optoacoustics. Proc SPIE. A. Oraevsky (ed), 3916, 130-137
`(2000) and Nicolaides et al.L. Nicolaides, A. Mandelis,
`and S.H. Abrams, “Novel Dental Dynamic Depth Profilo
`metric Imaging Using Simultaneous Frequency-Domain
`Infrared Photothermal Radiometry and Laser Lumines
`cence”, J Biomed Opt, 5, 31-39 (2000). More recently this
`technology has been used for occlusal pit and fissure R. J.
`Jeon C. Han A. Mandelis V. Sanchez S. H. Abrams “Diag
`nosis of Pit and Fissure Caries using Frequency Domain
`Infrared Photothermal Radiometry and Modulated Laser
`Luminescence” Caries Research 38,497-513 (2004) smooth
`Surface and interproximal lesion detection.
`
`SUMMARY OF THE INVENTION
`0006 The present invention provides an apparatus with
`frequency-domain infrared photothermal radiometry (FD
`PTR) and modulated laser luminescence (FD-LUM), as
`complementary dynamic dental detection and diagnostic
`tools, for inspecting sound and defective (cracked, carious,
`demineralized) spots on side Surface (Smooth Surface), top
`(biting or occlusal) Surface,nterproximal contact region
`between neighboring teeth intraorally and on root surfaces.
`The device is capable of monitoring ongoing demineraliza
`tion and or remineralization of various areas of the tooth
`surface whether in vivo or in vitro. This method can be
`extended to a modulated imaging of Sub-Surface of target
`tooth by using a multi-array infrared camera. In addition this
`method would include a conventional visible spectral range
`camera to capture and store images of the tooth Surface for
`ongoing reference. All this information can be stored on a
`computer hard drive or other types of memory devices
`including paper print out for retrieval during ongoing moni
`toring of the patient. In addition, the present technology can
`be used in conjunction with conventional spectral techniques
`for dental inspection, such as QLF or OCT in order to
`expand the range and resolution of Subsurface and near
`Surface detection.
`0007. In one aspect of the invention there is provided
`an apparatus for photothermal radiometry and modu
`lated luminescence for inspection of dental tissues of a
`patient, comprising:
`0008 at least one laser light source for irradiating a
`portion of a surface of a dental tissue with an effective
`wavelength wherein modulated photothermal radio
`metric signals and modulated luminescence signals are
`responsively emitted from said portion of the dental
`Surface;
`0009 detection means for detecting said emitted
`modulated photothermal signals and said modulated
`luminescence signals;
`0010 a hand held probe head, and a flexible optical
`fiber bundle having a distal end connected to said hand
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`held probe head, said optical fiber bundle including a
`first optical fiber having a proximal end in optical
`communication with said light source and a distal end
`terminated at said hand held probe head for transmit
`ting light from said light source to a patient’s dental
`tissue by a clinician handling said hand held probe
`head, said optical fiber bundle including a plurality of
`multi-mode optical fibers having distal ends terminated
`at said hand held probe head and proximal ends opti
`cally coupled to said detection means, a first pre
`selected number of said multi-mode optical fibers being
`near-infrared-transmitting optical fibers for transmit
`ting said modulated luminescence signals to said detec
`tion means, and a second pre-selected number of said
`multi-mode optical fibers being mid-infrared-transmit
`ting optical fibers for transmitting said photothermal
`radiometry signals;
`0011 demodulating means for demodulating said
`emitted modulated photothermal signals into photo
`thermal phase and amplitude components and said
`modulated luminescence signals into luminescence
`phase and amplitude signals; and
`0012 processing means for comparing said photother
`mal phase and amplitude signals to photothermal phase
`and amplitude signals of a reference sample and com
`paring said luminescence phase and amplitude signals
`to luminescence phase and amplitude signals of a
`reference sample to obtain differences, if any, between
`said portion of said dental tissue and said reference
`sample and correlating said differences with defects in
`said dental tissue.
`0013 The present invention also provides a method for
`detection of defects in dental tissue including erosive
`lesions, pit and fissure lesions, interproximal lesions,
`Smooth Surface lesions and or root carious lesions in
`dental tissue, comprising the steps of:
`0014) a) illuminating a portion of a surface of a dental
`tissue with at least one wavelength of light using a hand
`held probe head which is attached to a distal end of a
`flexible optical fiber bundle, said optical fiber bundle
`including a first optical fiber having a proximal end in
`optical communication with a light source which emits
`at said at least one wavelength, and a distal end
`terminated at said hand held probe head for transmit
`ting light from said light source to a patient’s dental
`tissue by a clinician handling said hand held probe
`head, said optical fiber bundle including a plurality of
`multi-mode optical fibers having distal ends terminated
`at said hand held probe head and proximal ends opti
`cally coupled to said detection means, a first pre
`selected number of said multi-mode optical fibers being
`near-infrared-transmitting optical fibers for transmit
`ting said modulated luminescence signals to said detec
`tion means, and a second pre-selected number of said
`multi-mode optical fibers being mid-infrared-transmit
`ting optical fibers for transmitting said photothermal
`radiometry signals, wherein upon illumination of said
`portion of a surface of a dental tissue with at least one
`wavelength of light modulated photothermal radiomet
`ric signals and modulated luminescence signals are
`responsively emitted from said portion of said Surface
`of the dental surface;
`
`0015 b) detecting said emitted modulated photother
`mal signals and said modulated luminescence signals;
`0016 c) demodulating said emitted modulated photo
`thermal signals into photothermal phase and amplitude
`components and demodulating said modulated lumi
`nescence signals into luminescence phase and ampli
`tude signals; and
`0017 d) comparing said photothermal phase and
`amplitude signals to photothermal phase and amplitude
`signals of a reference sample and comparing said
`luminescence phase and amplitude signals to lumines
`cence phase and amplitude signals of a reference
`sample to obtain differences, if any, between said
`portion of said dental tissue and said reference sample
`and correlating said differences with defects in said
`dental tissue.
`0018. The present invention also provides an apparatus
`for imaging dental tissue using modulated photother
`mal radiometry and luminescence for inspection of
`dental tissues of a patient, comprising:
`0019 at least one modulated laser light source for
`irradiating a portion of a surface of a dental tissue with
`a beam of light of an effective wavelength wherein
`modulated photothermal radiometric signals and modu
`lated luminescence signals are responsively emitted
`from said portion of the dental surface;
`0020 imaging detection means positioned with respect
`to said dental tissue for detecting images of said
`emitted modulated photothermal signals and said
`modulated luminescence signals;
`0021
`demodulating means for demodulating said
`images of emitted modulated photothermal signals into
`images of photothermal phase and amplitude compo
`nents and said images of modulated luminescence
`signals into images of luminescence phase and ampli
`tude signals; and
`0022 processing means for comparing said images of
`photothermal phase and amplitude signals to images of
`photothermal phase and amplitude signals of a refer
`ence sample and comparing said images of lumines
`cence phase and amplitude signals to images of lumi
`nescence phase and amplitude signals of a reference
`sample to obtain differences, if any, between said
`portion of said dental tissue and said reference sample
`and correlating said differences with defects in said
`dental tissue; and
`0023 image display for displaying said images.
`0024. The present invention also provides a method for
`imaging dental tissue for detection of defects in the
`dental tissue of a patient, comprising the steps of
`0025 a) illuminating a portion of a surface of a dental
`tissue with a beam of light of an effective wavelength
`wherein modulated photothermal radiometric signals
`and modulated luminescence signals are responsively
`emitted from said portion of the dental surface;
`0026 b) detecting images of said emitted modulated
`photothermal signals and said modulated luminescence
`signals:
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`0027 c) demodulating said images of emitted modu
`lated photothermal signals into images of photothermal
`phase and amplitude components and demodulating
`said images of modulated luminescence signals into
`images of luminescence phase and amplitude signals;
`0028 d) comparing said images of photothermal phase
`and amplitude signals to images of photothermal phase
`and amplitude signals of a reference sample and com
`paring said images of luminescence phase and ampli
`tude signals to images of luminescence phase and
`amplitude signals of a reference sample to obtain
`differences, if any, between said portion of said dental
`tissue and said reference sample and correlating said
`differences with defects in said dental tissue; and
`0029 e) displaying images representative of defects, if
`any, of the dental tissue on a computer display.
`In one aspect, the present method comprises
`0030)
`0031) irradiating the tooth surface with an excitation
`Source (laser) of Suitable emission wavelength in the
`near-ultraviolet—visible—near infrared spectral range;
`0032 providing rotational degrees of freedom to the
`excitation source for inspecting dental or tooth Surfaces
`at various angles;
`0033 producing periodic frequency pulses of the laser
`beam in the range including (but not confined to) dc to
`100 kHz:
`0034 delivering the radiation and collecting the emis
`sion by means of optical fibers or off-axis mirror
`configuration,
`0035 generating a baseline signal transfer function,
`H(f), by obtaining the frequency-scan data from a
`reference sample with well-known radiometric and
`dynamic (ac) luminescence properties and frequency
`response.
`0036 comparing by means of amplitude ratios and
`phase differences healthy, defective, erosion, deminer
`alized or carious dental tissue at various frequencies
`(e.g. 10 Hz and 1 kHz) for optimal contrast and
`cancellation of the instrumental frequency response.
`0037 performing depth-profilometric caries, deminer
`alized and erosion diagnostics and detection through
`frequency-scan data acquisition.
`0038 storing the data on the area examined to allow
`comparison of changes in the future,
`0039 providing a print out or hard copy of the status
`of the area examined,
`0040 if the data and clinical expertise indicates the
`presence of pathology, providing the ability to treat the
`tooth by using lasers to:
`remove the decayed or carious tooth material,
`0041)
`0042 remove tooth structure for the placement of
`materials,
`0043 prepare the tooth using known principles of
`tooth preparation design using conventional burs,
`ultrasonic energy, lasers or other devices for tooth
`preparation,
`
`0044 cure or set a filling material in the tooth
`preparation restoring the tooth to form and function,
`using Suitable laser-fluence delivery protocols
`through pulse-waveform engineering, for precise,
`optimized control of optical radiation delivery and
`thermal energy generation.
`0045 if the data and clinical expertise indicates the
`presence of demineralization, providing the ability to
`treat the tooth by using lasers to:
`0046)
`alter the Surface or Subsurface using a laser,
`0047 alter the surface or subsurface to allow the
`uptake of various media to enhance remineralization,
`0048 apply a medium that will either seal the sur
`face or promote remineralization of the Surface
`0049 cure or set a material on the tooth surface
`restoring the tooth to form and function, using Suit
`able laser-fluence delivery protocols through pulse
`waveform engineering, for precise, optimized con
`trol of optical radiation delivery and thermal energy
`generation.
`0050 monitor said interventional alterations in the
`condition of the tooth by means of combined PTR
`and LUM
`0051 monitor the tooth surface for ongoing changes
`prior to any intervention.
`0052 Monitor the tooth surface to demonstrate
`demineralization in vitro and remineralization after
`application of various therapies and solutions.
`0053 A further understanding of the functional and
`advantageous aspects of the invention can be realized
`by reference to the following detailed description and
`drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0054 The apparatus for defect detection in teeth accord
`ing to the present invention will now be described by way of
`example only, reference being had to the accompanying
`drawings in which:
`0055 FIG. 1 shows a schematic diagram of a first
`embodiment of a simultaneous frequency domain infrared
`photothermal radiometry and frequency domain lumines
`cence instrument for teeth defect detection with added
`rotational degrees of freedom for the excitation source for
`inspecting tooth surfaces at various angles according to the
`present invention;
`0056 FIG. 2a shows top (biting or occlusal) surface and
`cross sectional pictures at each measurement point, F1, F2,
`F3 and F4 of a typical carious lesions in the pits and fissures
`of a human tooth sample;
`0057 FIG.2b illustrates typical PTR and LUM responses
`in the frequency-domain for healthy and carious spots on a
`human tooth shown in FIG. 2a using 659-mm, 50 mW
`semiconductor laser excitation;
`0058 FIG. 3a illustrates a spatially scanned line across
`the interproximal contact points of two teeth;
`0059 FIG. 3b shows graphs illustrating PTR and LUM
`responses of spatial scan across the interproximal mechani
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`cal holes at a fixed frequency, 5 Hz. The excitation source is
`a 670 nm, 450 mW semiconductor laser;
`0060 FIG. 4 shows graphs illustrating PTR and LUM
`responses of spatial scan across the interproximal artificial
`carious lesion which is created by a demineralization-rem
`ineralization solution (2.2 mM potassium phosphate,
`monobasic (KHPO), 50 mMacetic acid (NaOAc), 2.2 mM
`of 1 M calcium chloride (CaCl), 0.5 ppm fluoride (F), and
`potassium hydroxide (KOH) for balancing the pH at 4.5) at
`a fixed frequency, 30 Hz. The excitation source is a 670 nm,
`450 mW semiconductor laser;
`0061 FIG. 5 shows PTR/LUM signals vs. treatment time
`for multiple samples with treatment time intervals from 6
`hours to 30 days at 5 Hz (a) and at 500 Hz, (b):
`0062 FIG. 6 illustrates a schematic diagram of hand held
`apparatus for simultaneous frequency domain infrared pho
`tothermal radiometry and frequency domain luminescence
`instrument for detection of defects in teeth which allows for
`improved compactness and access to occlusal or interproxi
`mal, buccal or lingual (Smooth Surface) or root surface
`geometries, as well as for Substantially enhanced infrared
`emission collection efficiency using fiber optic light delivery
`and IR radiation collection instead of the rigid limited-solid
`angle collection configuration of off-axis paraboloidal mir
`rors; and
`0063 FIG. 7 illustrates a schematic diagram of two
`dimensional lock-in imaging system by means of modulated
`infrared cameras.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`0064. The current invention is based on low-fluence
`photothermal radiometric detection and modulated lumines
`cence microscopy, which detects the emission of infrared
`radiation from a heated region of the sample without ther
`mally altering it. A temperature oscillation due to modulated
`heating causes a variation in the thermal emissions, which is
`monitored using an infrared detector. The temperature
`modulation allows for thermal energy to reach the Surface
`diffusively (or conductively) from a depth , (f)=2tvo/tf
`approximately equal to a thermal wavelength, where C. is the
`material thermal diffusivity cm/s) and f is the laser beam
`modulation frequency. In addition, black-body (Planck)
`radiation is emitted from all depths down to the inverse of
`the optical attenuation coefficient at the wavelength of laser
`excitation; the non-reabsorbed portion of this radiation is
`back-propagated out of the Surface of the photo-excited
`tooth and into a Suitable infrared detector carrying informa
`tion from those depths.
`0065. A schematic diagram of the apparatus is shown
`generally at 10 in FIG. 1. Semiconductor laser 12 with
`wavelength 659 nm (e.g. Mitsubishi ML120G21, maximum
`power 50 mW:) or with 830-nm (e.g. Sanyo DL-7032-001,
`maximum power 100 mW) is used as the source of both PTR
`and LUM signals. A diode laser driver 14 (e.g. Coherent
`6060) is used for the laser 12 and is triggered by the built-in
`function generator 16 of the lock-in amplifier 18 (e.g.
`Stanford Research SR830), modulating the laser current
`harmonically. The laser beam 20 is focused on the tooth
`sample 22. The modulated infrared PTR signal from the
`tooth is collected and focused by two off-axis paraboloidal
`
`mirrors 26 (e.g. Melles Griot 02POAO 19, Rhodium coated)
`onto an infrared detector 30 such as Mercury Cadmium
`Telluride (HgCdTe or MCT) detector (e.g. EG&G Judson
`J15D12-M204-S050U). Before being sent to the lock-in
`amplifier, the PTR signal is amplified by a preamplifier 32
`(EG&G Judson PA-300). For the simultaneous measurement
`of PTR and LUM signals, a germanium window 36 is placed
`between the paraboloidal mirrors 26 so that wavelengths up
`to 1.85 um (Ge bandgap) would be reflected and absorbed,
`while infrared radiation with longer wavelengths would be
`transmitted.
`0066. The reflected luminescence is focused onto a pho
`todetector 38 of spectral bandwidth 300 nm -1.1 um (e.g.
`Newport 818-BB-20). A cut-on colored glass filter 40 (e.g.
`Oriel 51345, cut-on wavelength: 715 nm) is placed in front
`of the photodetector 38 for luminescence to block laser light
`reflected or scattered by the tooth or root surface or inter
`proximal contact surfaces of the teeth 22. No luminescence
`data were possible under 830-nm excitation, since photolu
`minescence emission requires irradiation with higher pho
`tons than the peaks of luminescence at ca. 636, 673 and 700
`nm R. Hibst, K. Konig, “Device for Detecting Dental
`Caries.” U.S. Pat. No. 5,306,144 (1994). We tested 695-nm
`and 725-nm filters as well as a 715-nm filter and found the
`715-nm filter is optimal for cutting off the laser source (659
`nm) and cutting on the luminescence with negligible leakage
`signal (ca. 190 times less than the minimum dental LUM
`signals we obtained).
`0067. Therefore, the 715-nm cut-on filter 40 is used to
`measure the luminescence for only the 659-nm laser. For
`monitoring the modulated luminescence, another lock-in
`amplifier 42 (e.g. EG&G model 5210) is used. Both lock-in
`amplifiers 18 and 42 are connected to, and controlled by, the
`computer 50 via RS-232 or other equivalent ports. A pair of
`teeth 22 are mounted on LEGO bricks 52. This set up
`allowed the teeth 22 to be separated and remounted onto the
`exact position after creating artificial lesions.
`0068. The modulated PTR and LUM emissions are then
`demodulated into photothermal phase and amplitude com
`ponents and said modulated luminescence signals into lumi
`nescence phase and amplitude signals by a lock-in amplifier
`and processed to compare the photothermal phase and
`amplitude signals to photothermal phase and amplitude
`signals of a reference sample and comparing the lumines
`cence phase and amplitude signals to luminescence phase
`and amplitude signals of a reference sample to obtain
`differences, if any, between the portion of the dental tissue
`and the reference sample and correlating these differences
`with defects in the dental tissue. Further details are disclosed
`in U.S. Pat. No. 6,584,341 issued Jun. 24, 2003 to Mandelis
`et al. which is incorporated herein in its entirety by refer
`CCC.
`0069. The apparatus in FIG. 1 provides an optomechani
`cal design which allows for approximal tooth scans with
`three rotational (angle of the tooth and the mirror, angle of
`the laser and the tooth, and angle of the incident laser to the
`tooth) degrees of freedom.
`0070 FIG. 2 shows a mandibular second premolar illus
`trating the typical diagnostic and detection ability of PTR
`and LUM. The tooth had a DIAGNOdent reading of maxi
`mum 10 and average visual inspection ranking of 2.2
`indicating that a clinician would need to watch or monitor
`
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`OMNI 2025 - IPR20-00209
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`US 2007/0021670 A1
`
`Jan. 25, 2007
`
`the fissures. There was no indication on the radiographs of
`any caries being present. Nevertheless, PTR and LUM
`signals, including all information from the amplitude and
`phase responses over the entire frequency scan (1 HZ-1
`kHz), indicated that measurement spots F2 and F3 have
`caries into dentin. Histological observation results showed
`that this is, indeed, the case for these two points, as well as
`for point F1.
`0071. The signals from fissure F1 show the influence that
`fissure geometry, angle of the mouth of the fissure or the
`direction of the fissure base may have in the generation of
`PTR and LUM signals. The PTR amplitude of F1 in FIG.2b
`is above the healthy band and the PTR phase also shows
`clear departure from the healthy band in the high frequency
`range. This case illustrates the depth profilometric abilities
`of PTR. In the case of the slanted, curved carious fissure F1
`was illuminated by the incident laser beam in Such a way
`that the carious region formed a thin Surface layer, suc
`ceeded by a much thicker healthy subsurface enamel layer.
`0072. In response, the phase of the PTR signal for F1, in
`FIG.2b, falls within the healthy band at low frequencies as
`expected from the long thermal diffusion length which
`mostly probes the healthy enamel sub-layer with the carious
`Surface layer as a perturbation to the signal. At high fre
`quencies, however, the (short) thermal diffusion length lies
`mostly within the carious Surface layer and, as a result, the
`PTR phase emerges below the healthy band above ca. 50 Hz
`and joins the phases of the carious spots F2 and F3. In
`principle, the frequency of departure from the healthy band
`can be used to estimate the thickness of the carious Surface
`layer. PTR and LUM curves of the healthy fissure F4 are
`located within the healthy band confirming the histological
`observations.
`0073. In order to assess PTR and LUMascaries detection
`and diagnostic techniques and compare them (combined and
`separately) to other conventional probes, sensitivities and
`specificities were calculated at two different thresholds (D)
`and (D) as defined in Table 1 for all the diagnostic methods.
`While the PTR and LUM signals were taken from all 280
`occlusal measurement points, only 1 or 2 points on each
`tooth were assessed by the other examination methods.
`0074 Therefore, each calculation only used the corre
`sponding measurement points. To create Suitable criteria for
`assessing the carious state via PTR and LUM, the general
`characteristics of the respective signals and their converting
`equations, listed in Table 2 were used. Those characteristics
`were established from the experimental results of the fre
`quency scans with carious and healthy tooth samples. In the
`case of the PTR amplitude, the shape of the frequency scan
`curve for the healthy spot on a log-log plot is almost linear
`from low frequency (1 Hz) to high frequency (1000 Hz).
`while unhealthy spots (demineralized Surface, enamel caries
`or dentin caries) exhibit larger amplitude than healthy spots
`over the entire frequency range and a pronounced curvature
`with a “knee' at certain frequency ranges on the logarithmic
`plot.
`0075) The PTR phase shape for the healthy mineralized
`spot on a linear (phase)-log (frequency) plot