RECENT ADVANCES IN CARIES

DIAGNOSIS

INTRODUCTIONINTRODUCTION

A dynamic process; periods of demineralization alternate with periods of remineralization

If destruction exceeds repair, a preclinical, demineralized, subsurface carious lesion becomes a frank clinical cavity characterized by a breakdown of surface enamel and extension of the decay into the dentin

Dental caries is an infectious Dental caries is an infectious microbiological disease of the teeth microbiological disease of the teeth that result in localized dissolution that result in localized dissolution and destruction of calcified tissues. and destruction of calcified tissues. (Sturdevant)(Sturdevant)

Dental caries is an infectious, Dental caries is an infectious, communicable disease resulting in communicable disease resulting in destruction of tooth structure by destruction of tooth structure by acid-forming bacteria found in dental acid-forming bacteria found in dental plaque, in the presence of sugar plaque, in the presence of sugar ((NIH, 2001NIH, 2001))

DIAGNOSTIC TOOLS• VISUAL• TACTILE• VISUAL TACTILE• RADIOGRAPHS - Conventional – IOPAR &

Bitewing

Xeroradiography Digital – 1. Enhancement 2. Subtraction

3. Tuned Aperture Computed Tomography (TACT)

• BASED ON VISIBLE LIGHT Optical caries monitor (OCM) FOTI and DIFOTI QLF & DIAGNODENT, DELF and U.V

• BASED ON ELECTRICAL CURRENT Electric conductance Electric Impedence• ULTRASOUND• ENDOSCOPY, Videoscope• DYES – Enamel & Dentin • Micro air abrasion• Magnetic resonance micro imaging.

• NEWER TECHNOLOGIES:1. Terahertz2. Multi-photon Imaging3. Optical coherence tomography4. Infrared fluorescence5. Infrared thermography

Most currently used diagnostic methods are subjective in nature.

1. Detect lesion only at an advanced level.2. Cannot quantify the mineral loss3. Cannot measure the small changes in

mineral loss (gain) on demineralization. Early detection of carious lesions is an

important and necessary process in order to detect the early stages of demineralization.

DIAGNOSTIC TOOLS FOR DIAGNOSTIC TOOLS FOR CARIESCARIES

Several methods have been employed for caries diagnosis. These includea. Visual methodb. Tactile method (probing)c. Visual Tactile – European system, USA

systemd. Radiographs

· Conventional –IOPAR, Bitewing· Xeroradiography· Digital

Digital enhancementSubtraction RadiographyTACT(Tuned aperture computed tomography)

e. Based on visible Light· Optical caries monitor· FOTI & DIFOTI· Quantitative Light Induced fluorescence (QLF)

f. Based on Laser Light· Laser Auto fluorescence (Diagnodent)· Dye enhanced Laser fluorescence (DELF)

g. Electrical current· ECM (Electrical Conductance Measurement)· Electrical Impedance (ACIST)

h. Ultrasound – Ultrasound caries detectori. Ultravioletj. Endoscope (Endoscopic filteredfluorescence EFF)

k. Dyes – Enamel & Dentinl. Dye penetration method

A) VISUAL METHOD A) VISUAL METHOD

Ranking systems:Criteria for clinical and radiography

scorescore criteriacriteria

00 SoundSound

11 Active, surface intactActive, surface intact

22 Active, surface discontinuityActive, surface discontinuity

33 Active with cavityActive with cavity

44 Active with cavityActive with cavity

55 Inactive, surface intactInactive, surface intact

66 Inactive, surface discontinueInactive, surface discontinue

77 Inactive, cavityInactive, cavity

88 Filled with active lesionFilled with active lesion

99 Filled with inactive lesionFilled with inactive lesion

1010 Extracted due to cariesExtracted due to caries

Criteria for visual examination

scorescore criteriacriteria

00 No or slight change in enamel No or slight change in enamel transparency after prolonged dryingtransparency after prolonged drying

11 Opacity or discoloration hardly visible on Opacity or discoloration hardly visible on wet surface but distinct on air dryingwet surface but distinct on air drying

22 Opacity distinctly visible without air dryingOpacity distinctly visible without air drying

33 Localized breakdown in opaque or Localized breakdown in opaque or discolored enamel and gray discoloration discolored enamel and gray discoloration of dentinof dentin

44 Cavitations in opaque/enamel exposing Cavitations in opaque/enamel exposing the dentinthe dentin

B) PROBING (TACTILE EXAMINATION)B) PROBING (TACTILE EXAMINATION)Disadvantage- It can produce traumatic defects in lesions

arrested by plaque control alone.- Does not improve accuracy of diagnosis.- Inter operative variables.C) VISUAL TACTILE METHOD Makes use of both visual along with tactile

sensitivity with a probe /explorers. European System depends on detailed

visual examination. Subjects clean their teeth before examination, tooth surface dried with compressed air, and examination requires 10 minutes / subject

American Dental Association Criteria (USA) uses the softened enamel that catches an explorer and resists its removal and allows the explorer to penetrate the proximal surfaces with moderate to firm probing pressure. Here teeth are well lit, but neither cleaned nor dried and it takes 3 minutes per subject.

D) RADIOGRAPHICThe purpose of the radiograph is to detect

lesions that are clinically hidden from careful visual examination.

CRITERIA (MEJARE et al 1999)R0 = no radiolucencyR1 = Radiolucency confined to outer half of

enamelR2 = Radiolucency in inner half of enamel +

extending upto but not beyond DEJ.R3 = Radiolucency in dentin, broken DEJ, but

with no obvious spread in dentinR3 = Radiolucency with obvious spread in

outer half of dentin.R4 = Radiolucency with obvious spread in

inner half of dentin (> half way through to the pulp)

(Five point scale for occlusal caries) (Espelidel, 1994)-Based on clinical visual examination + radiographs

Grade 1:Grade 1: Non cavitated white spot /slightly Non cavitated white spot /slightly discolored caries lesion in enamel not discolored caries lesion in enamel not detected in the radiograph.detected in the radiograph.

Grade 2:Grade 2: Some superficial cavitation in the Some superficial cavitation in the fissure entrance, some non cavitated fissure entrance, some non cavitated mineral loss in the surface of the enamel. mineral loss in the surface of the enamel. Surrounding the fissure / and a caries Surrounding the fissure / and a caries lesion in enamel detected on the lesion in enamel detected on the radiograph.radiograph.

Grade 3:Grade 3: Moderate mineral loss with Moderate mineral loss with limited cavitation in the extreme of limited cavitation in the extreme of fissure /lesion in the outer third of dentin, fissure /lesion in the outer third of dentin, detected on radiograph.detected on radiograph.

Grade 4:Grade 4: Considerable mineral loss with Considerable mineral loss with cavitation or lesion into the middle third cavitation or lesion into the middle third of the dentin, detected on the radiograph.of the dentin, detected on the radiograph.

Grade 5:Grade 5: Advanced cavitation or lesion Advanced cavitation or lesion into the inner thirds of dentin, detected into the inner thirds of dentin, detected on radiograph.on radiograph.

Disadvantages- Overlapping of approximal contact- Cavitation not made out- two dimensional representation- Cervical burnout may mimic cervical

caries- False diagnosis of lesion depth

Radiographic appearance of Radiographic appearance of cariescaries

a) Occlusal cariesa) Occlusal cariesradiography are ineffective for detection radiography are ineffective for detection

until it reaches the dentin.until it reaches the dentin.LimitationsLimitations-Super imposition of enamel over fissures, -Super imposition of enamel over fissures,

lesions involving buccal groove can lesions involving buccal groove can simulate an occlusal lesion.simulate an occlusal lesion.

-Difficult to diagnose between occlusal -Difficult to diagnose between occlusal caries and internal resorption.caries and internal resorption.

b) Interproximalb) Interproximal

A considerable loss of mineral content is A considerable loss of mineral content is mandatory before lesion becomes mandatory before lesion becomes visible on radiograph. The actual depth visible on radiograph. The actual depth of lesion is always deeper than on of lesion is always deeper than on radiograph.radiograph.

Root caries / cemental caries / Root caries / cemental caries / senile cariessenile caries

Lesions on root with ill defined saucer Lesions on root with ill defined saucer appearance.appearance.

GradingGrading

Grade I – IncipientGrade I – Incipient

II – Shallow, less than 0.5 mmII – Shallow, less than 0.5 mm

III – DeepIII – Deep

IV – Pulpally involvedIV – Pulpally involvedLimitations of radiographs• Difficult to diagnose between residual

and secondary caries• Cannot be visualized unless it reaches an

additional stage.

XERORADIOGRAPHYImage is recorded on aluminum plate coated with

layer of selenium particles. These particles have a uniform electrostatic charge. When x-rays are passed on the film, this causes selective discharge of particles latent image thus formed is converted to a positive image by a process called “development.”

Advantages: Edge enhancement, no dark tooth processionDisadvantages: The electric charge over the film may cause

discomfort to the patient, exposure time varies

A digital imaging is an image formed and represented by a spatially distributed set of discrete sensors and pixels when viewed from a distance the image appear continuous, but on closer inspection it has individual pixels.

Digital image is simple means where image is recorded in non film receptors. There are 2 types.

-Direct- the direct image receptor that collects the x-ray directly e.g. RVG

-Indirect- E.g. Video camera is used for forming digital images of a radiograph.

DIGITAL DETECTORS• Charged Couple Device (CCD)• Complementary metal oxide semi

conductor (CMOS)• Phosphostimulable phosphorous plates

CCD was the first direct digital image receptor adapted for intra oral imaging and was introduced the dentistry in 1987.

The CCD is a solid state detector array with metal oxide semi conductor structure, such as silicon that is coated with X-ray sensitive phosphorous and is extremely sensitive to electromagnetic radiation whether X-rays / visible light.

These phosphorous converts incoming x-rays to wavelength that match the peak response of silicon. The detector array consists of either a column (Linear detector) or a chip (in which pixels are arranged in row and columns (area detector).

Mechanism of image formationMechanism of image formation When exposed to radiation, the covalent bonds When exposed to radiation, the covalent bonds

between silicon atoms are broken , electron between silicon atoms are broken , electron hole pairs get attracted to the potential to form hole pairs get attracted to the potential to form charge packet. Each packet corresponds to 1 charge packet. Each packet corresponds to 1 pixel .pixel .

The image is read by transferring each row of The image is read by transferring each row of pixel charges form one pixel to the next. As the pixel charges form one pixel to the next. As the charge reaches the end of the row it is charge reaches the end of the row it is transferred to a read out amplifier and transferred to a read out amplifier and transmitted as voltage gets converted to digital transmitted as voltage gets converted to digital image. Voltages from each pixel are sampled image. Voltages from each pixel are sampled and assigned a numerical value on the gray and assigned a numerical value on the gray scale.scale.

CMOSCMOS These detectors are silicon based and are These detectors are silicon based and are

fundamentally different from CCD’s in the way fundamentally different from CCD’s in the way that each pixel charge is read. Each pixel as that each pixel charge is read. Each pixel as connected directly to a transistor.connected directly to a transistor.

Phosphostimulable Phosphor Plate (PSP)Phosphostimulable Phosphor Plate (PSP) PSP absorb and store energy from X rays and PSP absorb and store energy from X rays and

then release this energy as light then release this energy as light (phosphorescence) when stimulated by light of (phosphorescence) when stimulated by light of appropriate wavelength. The material used is appropriate wavelength. The material used is Europeum doped Barium Fluorohalide. Barium Europeum doped Barium Fluorohalide. Barium in combination with iodine, chlorine, bromine in combination with iodine, chlorine, bromine forms crystal lattice. The addition of Europium forms crystal lattice. The addition of Europium creates imperfections in this lattice. When creates imperfections in this lattice. When simulated, valence electrons can absorb simulated, valence electrons can absorb energy and move into conduction band. These energy and move into conduction band. These electrons migrate to nearby (F centers) halogen electrons migrate to nearby (F centers) halogen valencies in the fluorohalide lattice and become valencies in the fluorohalide lattice and become trapped there.trapped there.

When stimulated by Red Light around 600 nm, When stimulated by Red Light around 600 nm, the barium fluorohalide releases trapped the barium fluorohalide releases trapped electrons to the conduction band. When an electrons to the conduction band. When an electron returns to Europium ions, energy is electron returns to Europium ions, energy is released in the green spectrum between 300-released in the green spectrum between 300-500 nm.500 nm.

Fiber optics conduct light from PSP plate to Fiber optics conduct light from PSP plate to photo multiplier tube.photo multiplier tube.

Converts light to electrical energy (A red light Converts light to electrical energy (A red light filter removes the stimulating light, and the filter removes the stimulating light, and the remaining green light is detected and remaining green light is detected and converted to varying voltage – digital image.converted to varying voltage – digital image.

E.g. of Direct digital radiography.E.g. of Direct digital radiography.

RVG (Trophy Japan) 10 x 28 mmRVG (Trophy Japan) 10 x 28 mm

Flash (Villa Italy) 20 x 24Flash (Villa Italy) 20 x 24 Sens – A ray (Regan) 17 x 26Sens – A ray (Regan) 17 x 26 Vixa – (Gendex) 18 x 24Vixa – (Gendex) 18 x 24

AdvantagesAdvantages Instant image, Instant image, no dark room,no dark room, Consistent imageConsistent image Eliminates hazards of film developmentEliminates hazards of film development Radiation dose is decreased Capable of tele transmission

DisadvantageDisadvantage Cost Cost Life expectancy of chipLife expectancy of chip

DIGITAL IMAGE ENHANCEMENTDIGITAL IMAGE ENHANCEMENT It was shown that the resolution of digital image It was shown that the resolution of digital image

is lower than radiographs and the range of gray is lower than radiographs and the range of gray shades is limited to 256, where as in a shades is limited to 256, where as in a radiographic film, over one million shades of radiographic film, over one million shades of gray appear.gray appear.

The diagnostic performance of un enhanced The diagnostic performance of un enhanced digital image does not exceed radiographs. digital image does not exceed radiographs. Therefore, the contract can be digitally Therefore, the contract can be digitally enhanced using a mathematical rule often enhanced using a mathematical rule often decided by the algorithm / filterdecided by the algorithm / filter

Digital image enhancement

Digital subtraction radiography Here, a digital bitewing radiograph is Here, a digital bitewing radiograph is

taken and sometime later a second taken and sometime later a second radiograph of exactly the same region is radiograph of exactly the same region is produced with identical exposure time, produced with identical exposure time, tube current and voltage.tube current and voltage.

By subtracting the gray values for each By subtracting the gray values for each coordinate of the first radiograph from coordinate of the first radiograph from equivalent coordinate of second, a equivalent coordinate of second, a subtraction image is obtained.subtraction image is obtained.

TUNED APERTURE TUNED APERTURE COMPUTED TOMOGRAPHYCOMPUTED TOMOGRAPHY

Better results in detection of Better results in detection of recurrent caries.recurrent caries.

Possible to visually progress through Possible to visually progress through slices of coronal anatomy and slices of coronal anatomy and observe the regions of interest.observe the regions of interest.

Examination of individual projections Examination of individual projections of a region.of a region.

E) DIAGNOSTIC METHODS BASED ON E) DIAGNOSTIC METHODS BASED ON VISIBLE LIGHT :VISIBLE LIGHT :

a) Optical caries monitorThis comprises of light source, measuring

and reference units and a detection part. The light is transported through a fiber bundle to the tip of hand piece. The tip is placed against the tooth surface and the reflected light is collected by different fibers of the same tip.

Disadvantage – used only for smooth surface lesion.

b) Quantitative fiber optic b) Quantitative fiber optic transilluminationtransillumination : FOTI : FOTI works under the principle works under the principle that since an area of carious that since an area of carious lesion has a lowered index of lesion has a lowered index of light transmission, an area of light transmission, an area of caries appears as a darkened caries appears as a darkened shadow. FOTI was initially shadow. FOTI was initially developed for proximal caries developed for proximal caries detection.detection.

Method -Method - A 150 watt halogen A 150 watt halogen lamp and rheostat is used to lamp and rheostat is used to produce a light of variable produce a light of variable intensity. A fiber optic probe intensity. A fiber optic probe of 0.5 mm diameter is used of 0.5 mm diameter is used to place in embrasure area. to place in embrasure area.

DIFOTI

Fiber optic transillumination

AdvantageAdvantage : : No hazards ,No hazards , lesion not diagnosed by radiographs can be lesion not diagnosed by radiographs can be

diagnoseddiagnosedDisadvantage : Subject to inter and intra observer variation. The major problem being low sensitivity. Therefore DIFOTI was introduced. Here instead of

human eye a CCD receptor is used. The receptor with photocells converts photon energy to electrical energy – transmitted to a video processor-converted into colour value and displayed on video monitor.

Advantage initial results indicate that both specificity and

sensitivity are high.

Quantitative Laser or Light Quantitative Laser or Light Induced Fluorescence Induced Fluorescence

(Laser (Laser Fluorescence ) :Fluorescence ) : The use of The use of

Fluorescence for Fluorescence for detection of caries detection of caries dates back to 1929, dates back to 1929, when Benedict when Benedict observed that normal observed that normal teeth fluoresce under teeth fluoresce under ultraviolet ultraviolet illumination. There is illumination. There is a difference in the a difference in the Fluorescence of sound Fluorescence of sound and caries teethand caries teeth..

Recently found that carious tissue Recently found that carious tissue when illuminated with argon laser when illuminated with argon laser light, has a clinical appearance of a light, has a clinical appearance of a dark, fiery , orange-red color .dark, fiery , orange-red color .

Decalcified areas appear as a dull, Decalcified areas appear as a dull, opaque, orange colour.opaque, orange colour.

DIAGNOdentDIAGNOdent

Based on research Based on research Hibst and Gal.Hibst and Gal.

Light source – Light source –

diode laser red diode laser red light 655 nm.light 655 nm.

PRINCIPLE PRINCIPLE :: Red light is transported via an Red light is transported via an

angulated tip with central fiber. angulated tip with central fiber. Reflected light is eliminated by and Reflected light is eliminated by and taken up by the photo-diode and taken up by the photo-diode and processed and presented on displayprocessed and presented on display

OPERATION:OPERATION: InstructionsInstructions – clean occlusal area.– clean occlusal area. Laser probe used to scan over fissure area Laser probe used to scan over fissure area

in a sweeping motion.in a sweeping motion.

Two values are displayed-Two values are displayed- Current value for the probe Current value for the probe

position(moment)position(moment) Maximum value for the whole surface Maximum value for the whole surface

examiner(peak).examiner(peak).

Criteria to assess caries Criteria to assess caries progressionprogression

Initial instructions suggest that, in Initial instructions suggest that, in general, numeric datageneral, numeric data

5-25 initial lesions in Enamel5-25 initial lesions in Enamel 25-35 initial dentinal caries25-35 initial dentinal caries > 35 advanced dentinal lesion.> 35 advanced dentinal lesion.

More recent cut off limits areMore recent cut off limits are

0-13 no caries0-13 no caries 14-20 enamel caries and preventive 14-20 enamel caries and preventive

care advisedcare advised 21-30 dentin caries and preventive or 21-30 dentin caries and preventive or

operative care advised depending on operative care advised depending on the caries assessmentthe caries assessment

>30 operative care advised>30 operative care advised

Photon undulatory non Photon undulatory non linear conversion(PNC)linear conversion(PNC)

Same principle of fluorescenceSame principle of fluorescence System(He-Ne) having a fiber optic System(He-Ne) having a fiber optic

device that delivers radiation to the device that delivers radiation to the tooth and a spectrophotometer device tooth and a spectrophotometer device that detects bacterial porphyrins that detects bacterial porphyrins fluorescence, allowing detection of fluorescence, allowing detection of caries,fillings, and calculus by caries,fillings, and calculus by simultaneous measurement of simultaneous measurement of backscattering and fluorescence backscattering and fluorescence intensity.intensity.

ULTRAVIOLETULTRAVIOLET

: UV light is used to increase the optical contrast between caries region and surrounding sound teeth.Advantage : Sensitive than visual tactile methodDisadvantage : Specificity is a problem as it cannot detect between caries lesionand developmental defect

DYE-ENHANCED LASER DYE-ENHANCED LASER FLUORESCENCE :FLUORESCENCE :

It had higher sensitivity than laser It had higher sensitivity than laser auto Fluorescence alone.auto Fluorescence alone.

Dyes used areDyes used are Pyro methane 556Pyro methane 556 Sodium FluorescinSodium Fluorescin

DIAGNOSTIC METHODS DIAGNOSTIC METHODS BASED ON ELECTRIC BASED ON ELECTRIC

CURRENT :CURRENT :

Electrical conductance Electrical conductance measurementmeasurement

Based on the principle that a Based on the principle that a demineralized tooth has more pores demineralized tooth has more pores filled with water and this is more filled with water and this is more conductive than intact tooth surface. conductive than intact tooth surface.

When current is applied by placing an electrode on tooth surface, the electrical conductance is measured between this electrode and contra electrode.

Electrical impedance Electrical impedance measurementmeasurement

Impedance is a Impedance is a measure of degree measure of degree which an electric which an electric current resists electric current resists electric current flow when a current flow when a voltage is applied voltage is applied across two electrodes. across two electrodes.

Caries tissue has Caries tissue has lower impedance(or lower impedance(or conduct electricity conduct electricity better) than sound better) than sound tooth.tooth.

DIAGNOSTIC METHODS DIAGNOSTIC METHODS BASED ON BASED ON

ULTRASOUNDULTRASOUNDMEASUREMENTSMEASUREMENTS

Ultrasound makes use of sound wave Ultrasound makes use of sound wave with a frequency ranging from 1.6 to with a frequency ranging from 1.6 to 10 MHz. 10 MHz.

Ultrasound interacts differently with Ultrasound interacts differently with different tissues. different tissues.

Ultrasound production – by Ultrasound production – by application of an alternating voltage application of an alternating voltage applied to an piezo electric crystal.applied to an piezo electric crystal.

METHOD:METHOD: To reach the target tissue, a coupling To reach the target tissue, a coupling

agent namely water, glycerin is used.agent namely water, glycerin is used. A flexible probe tip is fit into wedge A flexible probe tip is fit into wedge

shaped inter proximal contours to shaped inter proximal contours to confirm to the shape of the tooth.confirm to the shape of the tooth.

DISADVANTAGES:DISADVANTAGES: Only for superficial enamel lesions.Only for superficial enamel lesions.

ENDOSCOPEENDOSCOPE A blue light (400-500 A blue light (400-500

nm) is used to excite nm) is used to excite Fluorescence with in Fluorescence with in the tooth.the tooth.

Difference seen in Difference seen in fluoresced tooth is fluoresced tooth is viewed through a viewed through a specific broad band specific broad band gelatin filter; white gelatin filter; white spot lesions appear spot lesions appear darker than enamel.darker than enamel.

Advantage : Advantage : 5-10 fold magnification5-10 fold magnification

Disadvantage :Disadvantage : Requires meticulous drying and Requires meticulous drying and

isolation. isolation. Takes 5-10 minutes compared to 3-Takes 5-10 minutes compared to 3-

5minutes for conventional 5minutes for conventional technique.technique.

Additionally a camera can be used to Additionally a camera can be used to store the image. The integration of store the image. The integration of camera endoscope is called camera endoscope is called video video scope. scope.

A miniature colour video camera is A miniature colour video camera is mounted in a custom made metal mounted in a custom made metal holder. Thus image is directly viewed holder. Thus image is directly viewed on a television screen.on a television screen.

DYE-PENENTRATION DYE-PENENTRATION METHODS METHODS

For caries EnamelFor caries Enamel Procion disadvantage - irreversible as Procion disadvantage - irreversible as

dye reacts with nitrogen and dye reacts with nitrogen and hydroxyl groups of enamel.hydroxyl groups of enamel.

Calcein : Complexes with calciumCalcein : Complexes with calcium Fluorescent Dye : i) Brilliant blue ii) Fluorescent Dye : i) Brilliant blue ii)

ZygtoZX - 22ZygtoZX - 22

For Caries DentinFor Caries Dentin

0.5% basic fuschin in propylene glycol0.5% basic fuschin in propylene glycol 1% acid red in propylene glycol1% acid red in propylene glycol

Modified dye penetration method Modified dye penetration method – Iodine penetration method for – Iodine penetration method for measuring enamel porosity of measuring enamel porosity of incipient caries region was developed incipient caries region was developed by Balnos in 1977.by Balnos in 1977.

MICRO AIR ABRASIONMICRO AIR ABRASION

Introduced by the Introduced by the S.S. White S.S. White Company in 1951.Company in 1951.

More conservative More conservative means of means of diagnosing pit and diagnosing pit and fissure caries.fissure caries.

Uses a narrowly focused particle Uses a narrowly focused particle stream that abrades tooth structure stream that abrades tooth structure in proportion to the particle size, air in proportion to the particle size, air pressure and nozzle distance pressure and nozzle distance employed.employed.

Examines darkened areas in bottoms Examines darkened areas in bottoms of pits and fissures.of pits and fissures.

Magnetic Resonance Micro Magnetic Resonance Micro ImagingImaging

Significant for disease of mineralized Significant for disease of mineralized dental tissue.dental tissue.

Non invasive and non destructive.Non invasive and non destructive. Allows a specimen to be re-imaged Allows a specimen to be re-imaged

after further exposure to a clinically after further exposure to a clinically relevant enviornment.relevant enviornment.

PRINCIPLE :PRINCIPLE : When a magnetic field is applied, the When a magnetic field is applied, the

nuclear spins align in a finite number nuclear spins align in a finite number of allowed orientations; if these of allowed orientations; if these orientations are perturbed by a pulse orientations are perturbed by a pulse of radio frequency energy, this of radio frequency energy, this energy is absorbed and then energy is absorbed and then retransmitted. retransmitted.

It is this retransmitted energy that is It is this retransmitted energy that is detected and thus correlated to the detected and thus correlated to the amount of demineralisation.amount of demineralisation.

NEW DIAGNOSTIC NEW DIAGNOSTIC MODALITIES FOR CARIES MODALITIES FOR CARIES

LESIONLESION

Multi photon imagingMulti photon imaging Terahertz imagingTerahertz imaging Transversal wavelength Transversal wavelength

independent microradiographyindependent microradiography Infra red thermography or infra Infra red thermography or infra

red fluorescencered fluorescence Frequency domain photo Frequency domain photo

thermal radio metry and thermal radio metry and Frequency domain luminescenceFrequency domain luminescence

Multiphoton imagingMultiphoton imaging

Advantage :Advantage : 1) Non invasive method – that measures 1) Non invasive method – that measures

the amount of mineral loss as athe amount of mineral loss as a function of fluorescence loss.function of fluorescence loss. 2) Low average level of laser power. 2) Low average level of laser power.

Therefore lower risk of photo toxicity toTherefore lower risk of photo toxicity to the pulp.the pulp. 3) Longer incident wave length results in 3) Longer incident wave length results in

increased penetrationincreased penetration

Disadvantage :Disadvantage : 1) The Micron assay movements 1) The Micron assay movements

required to produce serial tomographic required to produce serial tomographic images over a period of 1 min or so is images over a period of 1 min or so is well beyond the capabilities of most well beyond the capabilities of most dentists.dentists.

2) Can collect information from caries 2) Can collect information from caries lesion up to 500 μmlesion up to 500 μm

3) Currently the technique is performed 3) Currently the technique is performed only on extracted teeth and large laser only on extracted teeth and large laser equipment required to produce such an equipment required to produce such an image will take years to develop.image will take years to develop.

Infra-Red ThermographyInfra-Red Thermography

Method of determining lesion activity Method of determining lesion activity rather than a method of determining rather than a method of determining of presence or absence of disease.of presence or absence of disease.

Principle - thermal radiation Principle - thermal radiation energy travels in the form of energy travels in the form of waves. It is possible to waves. It is possible to measure measure changes in thermal energy when changes in thermal energy when fluid is lost from a lesion by fluid is lost from a lesion by evaporation.evaporation.

Disadvantages :Disadvantages : 1) Not used intra orally1) Not used intra orally 2) Variation will exist in temperature 2) Variation will exist in temperature

of mouth with respiration or fluid of mouth with respiration or fluid evaporation from oral surfaces.evaporation from oral surfaces.

3) The source to specimen distance is 3) The source to specimen distance is unsuitable for posterior teeth.unsuitable for posterior teeth.

4) There is no data that the rate of 4) There is no data that the rate of fluid loss from the lesion is directly fluid loss from the lesion is directly related to the reactivity of the lesion.related to the reactivity of the lesion.

Infra-red Fluorescence :Infra-red Fluorescence :

Method :Method : Tooth is exposed to light with the Tooth is exposed to light with the

wave length between 700 and wave length between 700 and 15,000 nm.15,000 nm.

Barrio filters are used to observe Barrio filters are used to observe any resulting Fluorescenceany resulting Fluorescence

Disadvantages :Disadvantages : 1) Results are not documented.1) Results are not documented. 2) May have potentially damaging 2) May have potentially damaging

effects on the pulp given the increasedeffects on the pulp given the increased penetration and decreased scattering penetration and decreased scattering

of the longer wave length.,of the longer wave length., 3) Sources of such irradiation are 3) Sources of such irradiation are

difficult to acquire.difficult to acquire. 4) Detection involves the use of infra 4) Detection involves the use of infra

red sensitive detectors as CCDs or filmred sensitive detectors as CCDs or film

Optical Coherence Optical Coherence Tomography (OCT)Tomography (OCT)

Method of imaging developed for Method of imaging developed for transparent and semi transparent transparent and semi transparent structures.structures.

Wave length of light 840-1310 nm Wave length of light 840-1310 nm depth 0.6-2 mmdepth 0.6-2 mm

Principle :Principle : Based on interference of light. Based on interference of light. When a light beam is split into two When a light beam is split into two

and then recombine interference and then recombine interference produces a pattern the intensity of produces a pattern the intensity of which is determined by the level of which is determined by the level of light in each beam. light in each beam.

OCT uses super luminescent diodes. OCT uses super luminescent diodes. (SLD) as light source. This type of (SLD) as light source. This type of source produces light with the broad source produces light with the broad range of wave length.range of wave length.

Advantage :Advantage :

1) Non-invasive diagnosis of secondary 1) Non-invasive diagnosis of secondary cariescaries

2) Development of prototype hand 2) Development of prototype hand pieces for intra-oral OCTpieces for intra-oral OCT

Terahertz ImagingTerahertz Imaging

Uses waves with terahertz frequency Uses waves with terahertz frequency (15 μm to 1 mm) (15 μm to 1 mm)

This wavelength form a short enough This wavelength form a short enough to provide a reasonable resolution to provide a reasonable resolution but long enough to prevent a serious but long enough to prevent a serious loss of signal due to scattering.loss of signal due to scattering.

Method :Method :

The object is placed in the path of The object is placed in the path of terahertz beam or the terahertz terahertz beam or the terahertz beam can be scanned over the beam can be scanned over the surface of the object, the image is surface of the object, the image is recorded using CCD imaging.recorded using CCD imaging.

AdvantagesAdvantages

1) Low powers used for imaging.1) Low powers used for imaging. 2) Use of Non-ionizing radiation.2) Use of Non-ionizing radiation. 3) No alteration of electrical charge 3) No alteration of electrical charge

of tissue examinedof tissue examined

Disadvantages Disadvantages ::

1) low spatial resolution due to long 1) low spatial resolution due to long wave length of the source.wave length of the source.

2) Alterations in image interpretation 2) Alterations in image interpretation since terahertz waves are strongly since terahertz waves are strongly absorb by water, a potential absorb by water, a potential complication in the mouth.complication in the mouth.

Thank youThank you