A REVIEW OF MODERN NON-INVASIVE METHODS FOR CARIES DIAGNOSIS

1. 168
A REVIEW OF MODERN NON-INVASIVE METHODS FOR
CARIES DIAGNOSIS
N.K.Prabhakar*
, Kiran kumar .N*
, M.Kala*
ABSTRACT
This paper details the current techniques for the detection of caries using non-invasive techniques, namely Caries
Detection Methods Based on Changes in Optical Properties between Healthy and Carious Tissue. To create opportunity
for a preventative approach to the management of caries, it is important to keep abreast of developments in diagnostic
systems. This article is intended to assist practitioners in developing their knowledge and understanding of the
modern management of caries by providing an update on emerging diagnostic systems, techniques, description as to
how each of the modalities function, consideration is given to recent advances and changes in the relevant technologies,
and review of the same.
AOSR 2011;1(3):168-177.
KEYWORDS: Dental caries, Fluorescence, Transillumination, Optical coherence.
* Department of Conservative Dentistry and Endodontic, Govt. Dental College & Research Institute, Bangalore-560002,
INDIA.
INTRODUCTION :
Dental caries continues to be a common chronic disease
among various population groups. Patient care can be
improved with detection at the earliest stage. However,
current techniques like visual, tactile and radiographs
do not have sufficient sensitivity and specificity. The
visual method cannot help in detecting the caries in
its very early stage and discoloration of pits and fissure
can be misinterpreted as caries. The tactile method holds
the potential to transmit cariogenic bacteria from
one site to another and also may produce irreversible
traumatic defects in potentially remineralizable defects.
The commonly used methods of radiographs is a two
dimensional image of a three dimensional object.
Because of this sometimes interpretation becomes
difficult. Many of these limitations have been overcome
by subtraction radiography but still correct projection
geometry is mandatory. The difficulty of reliably
diagnosing early lesions of caries is well documented,
let alone more extensive lesions.1,2
The profession has
for too long relied on good vision and clinical acumen
for the clinical and radiographic diagnosis of caries. The
use of new systems and techniques in the diagnosis of
caries, if properly applied, can improve reliability, let
alone aid in the detection of early demineralisation,
which may not be apparent clinically. In addition, new
diagnostic modalities allow early lesions of caries to be
quantified, thereby creating the opportunity to monitor
caries progression, or resolution by remineralisation. Such
developments reduce the reliance on subjective visual
examination, although this is still a key skill, supplemented
from time to time by radiographs, and create opportunities
for a preventative rather than the now outdated “drill
and fill” approach to the management of caries.3,4
This
paper reviews optical caries detection methods and these
systems for the diagnosis of caries.
Optical caries detection methods:
Optical caries detection methods are based on observation
of the interaction of energy which is applied to the tooth,
or the observation of energy which is emitted from
the tooth.5
Such energy is in the form of a wave in the
electromagnetic spectrum. The caries detection methods
described in this paper use light in the visible and
near-infrared range (NIR). In its simplest form, caries
can be described as a process resulting in structural
changes to the dental hard tissue. The diffusion of
calcium, phosphate, and carbonate out of the tooth, the
demineralisation process, will result in loss of mineral
content. The resultant area of demineralised tooth
substance is filled mainly by bacteria and water. The
porosity of this area is greater than that of the surrounding
structure. Increased scattering of incident light due to
this structural change appears to the human eye as a so-
called white spot. Hence, the caries process leads to
distinct optical changes that can be measured and
quantified with advanced detection methods based on
light that shines on and interacts with the tooth.
Scattering: Scattering is the process in which the direction
of a photon is changed without loss of energy. The incident
Archives of Oral Sciences & Research

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light is forced to deviate from a straight path when it
interacts with small particles or objects in the medium
through which the light passes. In physical terms scattering
is regarded as a material property. A glass of milk is seen
as white because incident light on the milk is scattered
in all directions, leaving the milk without absorption.6
Snow appears white because light incident in the snow is
scattered in all directions by the small ice crystals. Light
of all visible wavelengths exits snow without suffering
absorption. Scattering is highly wavelength sensitive,
shorter wavelengths scatter much more than longer
ones.5
Therefore, caries detection methods employing
wavelengths in the visible range of the electromagnetic
spectra (400 nm to 700 nm) are highly limited by scattering.
An early enamel lesion looks whiter than the surrounding
healthy enamel because of strong scattering of light within
the lesion.6
Methods measuring lesion severity are based
on differences in scattering between sound and carious
enamel.
Absorption with Fluorescence: Absorption is the
process in which photons are stopped by an object and
the wave energy is taken in by the object. The energy
lost is mostly converted into heat or into another wave
which has less energy and hence longer wavelengths. In
physical terms absorption is also regarded as a material
property. The previous analogy of the glass of milk
appearing white can be extended to a cup of tea; the tea
is seen as transparent because it does not scatter light,
but it looks brown because much of the light is absorbed
by the tea.5
Likewise, mud and pollution in white snow
can be seen as dark spots because certain wavelengths
are absorbed by these polluted spots. Absorption of
light in tissue is strongly dependent on the wavelength.
Water is an example of a strong absorber in the infrared
range. After absorption the energy can be released by
emission of light at a longer wavelength, through the
process of fluorescence. Fluorescence occurs as a result
of the interaction of the wavelength illuminating the
object and the molecule in this object. The energy is
absorbed by the molecule with subsequent electronic
transition to the next state, to a higher level state where
the electrons remain for a short period of time. From
here the electrons may fall back to the ground state and
release the gained energy in terms of longer wavelength
and colour, which is related to the energy given off
and fluorescent light can be emitted. Autofluorescence,
the natural fluorescence of dental hard tissue without
the addition of other luminescent substances has been
known for a long time.7
Demineralisation will result in
loss of autofluorescence which can be quantified using
caries detection methods based on the differences
in fluorescence between sound and carious enamel.8
Optical coherence tomography (OCT): OCT can be
defined as optical inferometric technique to create cross
sectional images of scattering media. There are various
functional techniques developed in OCT. They are 1)
Polarisation sensitive Optical coherence tomography (PS-
OCT) 2) Doppler OCT 3) Wave length dependent OCT
among these PS-OCT is popular
Studies of light propagation in dental tissue using PS-OCT
revealed strong birefingence in enamel and anisotropic
light propagation through dentinal tubules.9
Amaechi et
al10
used the area under the LCI signal as a measure of
the degree of reflectivity of the tissue and showed that
this area is related to the amount of mineral loss,
and increases with increasing demineralization time.
Hence, OCT could possibly be used to quantitatively
monitor the mineral changes in a caries lesion. In the
early investigations, birefringence induced artefacts in
the enamel OCT image.11
These were eliminated by
measuring the polarization state of the returned light.
Birefringence detected by PS-OCT, however, has been
shown to be useful as a contrast agent indicating pre-
carious or carious lesions in both enamel and dentin.9
Baumgartner et al showed that PS-OCT can provide
additional information related to the mineralization status
and/or the scattering properties of the dental materials.12
The studies demonstrated that PS-OCT is well suited for
the imaging of interproximal and occlusal caries, early
root caries, and for imaging decay under composite
fillings. Longitudinal measurements of the reflected light
intensity in the orthogonal polarization state from the
area of simulated caries lesions linearly correlated with
the square root of time of demineralization indicating that
PS-OCT is well suited for monitoring changes in enamel
mineralization over time.13
OCT provides high resolution morphological depth
imaging of incipient caries. With OCT, early lesions
can be readily identified as regions of high light
backscattering with depth into the enamel as compared to
healthy sound enamel. From the OCT images, the lesion
depth can be approximated to provide clinically useful
information to guide treatment decisions. In addition,
there is a derived parameter known as the optical
attenuation coefficient in order to distinguish sound from
carious enamel non-subjectively. OCT is being combined
with Polarized Raman Spectroscopy (PRS) since regions
of high light backscattering not related to caries
development can lead to false-positive results. PRS
provides biochemical specificity along with molecular
structural/orientational information. With PRS, the
Raman depolarization ratio calculated from the main
phosphate vibration at ~959 cm-1
from parallel- and cross-
polarized Raman spectra allows discrimination between
sound and early developing caries. In combination,
OCT and PRS have potential for detecting and monitoring
early lesions with high sensitivity and high specificity.14
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Polarized Raman Spectroscopy (PRS): OCT imaging
in regions of hypocalcification can sometimes show
increased light back-scattering at the surface, which
could be misinterpreted as signs of early caries. To
help rule out such false-positive readings and increase
the specificity of this method, OCT and PRS have been
coupled to obtain biochemical information for
confirmation of caries. PRS provides details on the
molecular composition (e.g., collagen in dentin vs.
predominantly inorganic apatite in enamel) and molecular
structure of cells and tissues.
Like OCT, PRS measures light scattering. Although
most scattered photons have the same energy and
wavelength as the incoming excitation light, about 1
in 107
photons scatter at energy different from that of
the incoming light. This energy difference is proportional
to the vibrational energy of the scattered molecules
within the sample and is known as the Raman Effect.
As with other emerging optical methods, the properties
of the scattered light within sound or porous carious
regions are being explored to determine their use in
caries detection.15
In fluorescence-based techniques, there are a limited
number of intrinsic fluorophores that can provide
diagnostic information without the addition of
external dyes. In contrast, PRS can provide information
not only about bacterial porphyrins leached into
carious regions, but also about the primary mineral
matrix and, thus, the state of demineralization or
remineralisation of the tooth. This information is
gathered without the need to add extrinsic dyes or
agents. PRS provides information on the composition,
crystallinity and orientation of the mineral matrix,
all of which are affected in caries formation or
remineralization.15
Fibre Optic Transillumination (FOTI and DIFOTI):
FOTI :
The diagnosis of approximal carious lesions has been
primarily through visual clinical examination. However,
in situations where the teeth are normally in anatomical
contact with others, it is a very difficult task for the
dentist to detect caries in posterior teeth by that
exam, resulting in a high proportion of false negative
decisions.16,17
Conventional bitewing radiography remains the most
common diagnostic aid because it has been shown
to enhance the detection of approximal lesions.17-19
However, there are some problems associated with this
technique, for example, if the horizontal angulation is
incorrect, overlapping of approximal surfaces will occur
on the radiograph. Other problem is the incapacity
of method to distinguish noncavitated from cavitated
lesions.
Fibre-optic transillumination (FOTI) has been investigated
as an alternative method for the detection of approximal
carious lesions.20
In this method, a white light from a
cold-light source is passed through a fiber to an intra-
oral fiber-optic light probe that is placed on the buccal
or lingual side of the tooth and the surfaces are
examined through transmitted light, which is viewed
from the occlusal surface. A carious lesion has a
lowered index of light transmission and so appears as
a darkened shadow when transilluminated.20
FOTI is a
simple, non-invasive, and painless procedure that can
be used repeatedly with no risk to the patient. In the
literature, the validity of diagnoses made with FOTI
has usually been assessed by comparison with the
radiographic diagnosis of the same surface, although it
is well known that radiography itself is not an accurate
method.17-20
Little information is available about
the performance of FOTI in the detection of early
approximal carious lesions in vivo using validation
methods other than radiographic examinations.21,22
Fibre optic consists of a halogen lamp and a rheostat
to produce a light of variable intensity. The 150 watt
lamp generates a maximum light intensity of 4000 lX
at the end of 2.0 mm diameter cable. Two attachments
are used; a plane mouth mirror mounted on a steel
cuff and a fibreoptic probe of 0.5 mm diameter so that
it can be placed in embrasure region. It produces a
narrow beam of light for transillumination. The rheostat
is set to give a light of maximum intensity.
For examination the tip of the probe is placed in
the embrasure immediately beneath the contact point of
the proximal surface to be examined either on the buccal
or lingual surface depending on the tooth. The marginal
ridge is viewed from the occlusal surface.
A shadow extending to the dentinoenamel junction
beneath the marginal ridge may be evident if there is a
break in the integrity of the enamel of marginal ridge.
The Midwest Caries I.D.™*
:
DENTSPLY Professional presents the Midwest Caries
I.D.™ Detection Handpiece, a portable, handheld device
designed to aid in the detection of caries in non-restored
occlusal pits and fissures and interproximal areas on
adult posterior teeth. The combination of LED and
fiber optic technologies enables Clinicians to quickly
and easily detect up to 92% of occlusal caries and
80% interproximal caries. The Midwest Caries I.D.™
Detection Handpiece provides clinicians with an
accurate, easy-to-use instrument. One probe detects
N.K.Prabhakar et al.
*
DENTSPLY Professional Division, York, PA.

4. 171
both interproximal and occlusal caries while providing
clinical access and enhanced visibility, and the visual and
audible caries detection signals provide an ideal end-
user interface. The probe must be used in wet environments
The Midwest Caries I.D.™ system comes complete
with the probe, shell, and detection module. It also
includes a custom cassette, ceramic calibration target,
fiber optic cleaning swabs, polishing papers , AAA lithium
batteries, and directions for use.
DIFOTI :
This is a relatively new methodology that was adopted in an
attempt to reduce the perceived shortcomings of FOTI
by combining FOTI and a digital charge-coupled
device (CCD) camera. Digital Imaging Fiber-Optic
TransIllumination (DIFOTI) has been introduced to
improve early detection of carious surfaces. DIFOTI
uses fiber-optic transillumination of safe visible light to
image the tooth. Light delivered by a fiber-optic is
collected on the other side of the tooth by a mirror
system and fed to a digital electronic CCD. Then the
acquired data are sent to a computer for analysis with
dedicated algorithms, which produce digital images that
can be viewed by the clinician and patient in real time or
stored for later use.23
DIFOTI uses visible light and not the ionising radiation
and is approved by US food and drug administration
for caries detection on approximal smooth and occlusal
surface as well as recurrent caries. DIFOTI uses
scattering of light by carious tissue as a method of
distinguishing it from healthy enamel the carious part of
the tooth appears to be dark against the light background
of healthy tooth.
Schneiderman et al.24
found that DIFOTI technique
has superior sensitivity over conventional radiographic
methods for detection of approximal, occlusal, and
smooth surface caries, and specificity was slightly less
in general. It has all the advantages of FOTI and also
it has overcome the disadvantage of FOTI as images in
this technique can be stored for future reference.
Quantitative Light-induced Fluorescence:
Another dental diagnostic tool for detection of early
carious lesions is quantitative light-induced fluorescence
(QLF), which is based on auto-fluorescence of teeth.
When the teeth are illuminated with high intensity
blue light, the resultant auto-fluorescence of enamel
is detected by an intraoral camera which produces
a fluorescent image. The emitted fluorescence has a
direct relationship with the mineral content of the
enamel.25–27
Thus, the intensity of the tooth image
at a demineralised area is darker than the sound area.
The software of QLF systems can process the image
to provide user quantitative parameters such as lesion
area, lesion depth, and lesion volume. These parameters
can detect and differentiate the lesions at very early
stages, and make the QLF system more sensitive to
changes of caries over time. The image can be stored
for longitudinal study and be used as patient motivators
in a preventative practice.28
QLF uses a blue light (488 nm) to illuminate the
tooth, which normally fluorescence a green colour.
Teeth should be dried before its application.29
Hafström-Björkman et al found a sensitivity of 0.72-
0.76 and a specificity of 0.79-0.81 for this technique.30
This can also be used to image plaque and calculus,
and therefore be useful in identifying active caries. This
technique has found many applications in clinical trials,
research, patient education, and preventive clinical
practice it can effectively monitor demineralization and
remineralisation of teeth invitro and a good correlation
has been reported with other techniques measuring
mineral loss, such as transverse microradiography
analysis.31
Also it can be used to measure erosive
potential of a range of mouth washes invitro and
to see early secondary caries beneath the amalgam
restorations.32
However it cannot differentiate between
decay and hypoplasia; has inability to detect or monitor
interproximal lesions and is limited to measurement of
enamel lesions of at most several hundred micrometers
depth.
Laser-induced Fluorescence:
Recently a compact hand held device has been
marketed, DIAGNODENT.†
This device makes use of
laser autofluorescence technology,33
but instead of
using blue light it uses red light, of wavelength
655nm, output <1mW. This red laser light identifies
caries as having an increased fluorescence over sound
tooth, whereas blue light highlights caries as a reduced
fluorescence compared to sound tooth. These differences
are attributable to the characteristics of light of
different wavelength, and the effects of light of
different wavelength in teeth and lesions of caries.
The science behind this phenomenon appears to be
the increased fluorescence exhibited by cariogenic
bacterial metabolites within the lesion, as well as
the changed fluorescent nature of the lesion itself.34
The DIAGNODENT unit (KaVo) comprises a pen like
device with detachable tips of different diameter. The
central core fibre running through the pen grip and tip
is a red laser, with the surrounding fibres being
detectors to measure the returned fluorescent light
from the tooth surface. A reading is provided on a
digital display accompanied by an audible tone. The
higher the digital reading and pitch of the audible
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†
KaVo Dental, Germany

5. 172
tone, the greater the potential for caries involvement
of the amelodentinal junction and the underlying dentine.
Each patient must be individually calibrated, by setting
a base level on a healthy tooth. No definite value can be
given as to when caries is present and when prevention
or intervention is indicated, but scores above 25 are to
be considered to suggest a high probability of caries.
Monitoring can therefore be carried out without the
need for exploratory cavity preparation or radiographs.
Indeed, the level of the earliest detected caries may relate
to a lesion that may not be apparent radiographically.35
The device performs best on smooth surfaces and in
occlusal pits and fissures. Limitations of this device
include the need for the tooth surfaces and fissures
being assessed to be clean and dry. To date there is no
evidence to support the use of DIAGNODENT for the
detection of approximal or secondary caries adjacent
to existing restorations, let alone recurrent caries
subjacent to a restoration, whether metallic or tooth-
coloured. The presence of an existing restoration or
fissure sealant may adversely affect the accuracy of the
device.
Experience, over a one-year period with DIAGNODENT,
both clinically and with extracted teeth in the
laboratory lends support to the views of Ross.36
The
device is relatively straightforward to apply and with
a short familiarisation period can be used to quickly
assess teeth with a high degree of accuracy. Ross reports
that he became less reliant on only clinical visual
examination, and of being more confident as to the exact
location and extent of occlusal caries. This allowed
his management of such caries to become more
conservative. The DIAGNODENT provides a quantitative
measurement to supplement the subjective information
from clinical examination, in reaching a decision as to
when intervention is appropriate.
Transillumination with Near-Infrared light:
The caries lesion may also be examined by shining
white light through the tooth. Wavelengths in the
visible range (400–700 nm) are limited by strong light
scattering, making it difficult to image through more
than 1 mm or 2 mm of tooth structure.37
Therefore,
methods employing wavelengths in the visible range
of the electromagnetic spectra (400–700 nm) such as QLF
(λ > 520 nm), LF (λ = 655 nm), and Digital Imaging
Fiber-Optic Transillumination (DIFOTI)38
which
uses high intensity white light, are highly limited
by scattering. Methods that use longer wavelengths,
such as in the NIR spectra (780-1550 nm), can penetrate
the tissue more deeply. This deeper penetration is
crucial for the transillumination (TI) method. Research
has shown that enamel is highly transparent in the
NIR range (750 nm-1500 nm) due to the weak
scattering and absorption in dental hard tissue at
these wavelengths.39-41
Near-Infrared reflectance imaging:
In this technique, the tooth is exposed to light (irradiation)
with a wave length of between 700 and 1500 nm. Light
scattering in sound dental enamel decreases markedly
in the NIR region and studies have shown that enamel
has the highest transparency near 1310 nm.41,42
At this
wavelength, the attenuation coefficient is only 2 to 3
cm−1
, which is a factor of 20 to 30 times lower than in
the visible region. At longer wavelengths, water
absorption increases significantly and reduces the
penetration of the NIR light. Even though the light
scattering for sound enamel is at a minimum in the NIR,
the light scattering coefficient of enamel increases by
2-3 order of magnitudes upon demineralization due to
the formation of pores on a similar size scale to the
wavelength of the light that act as Mie scatterers.41
Therefore, caries lesions can be imaged with optimal
contrast at 1310 nm.43
And detection is done by infrared
sensitive detectors as CCD or film. According to Christian
Zakian et al 44
a sensitivity of > 99% and a specificity of
87.5% for enamel lesions and a sensitivity of 80% and a
specificity > 99% for dentine lesions. The nature of the
techniqueofferssignificantadvantages,includingtheability
to map the lesion distribution rather than obtaining single-
point measurements, it is also non-invasive, noncontact,
and stain insensitive. These results suggest that NIR
spectral imaging is a potential clinical technique for
quantitative caries diagnosis and can determine the
presence of occlusal enamel and dentin lesions.
Infrared fluorescence:
This technique has seldom been reported. In theory,
the tooth is exposed to light (irradiation) with a
wavelength of between 700 and 15,000 nm. Barrier
filters are used to observe any resulting fluorescence.
Studies by Alfano et al. mention exposure of teeth to
wavelengths exceeding 700 nm, but the results were
not presented.45
Unpublished reports commented upon
by Longbottom suggest that the technique is able
to discriminate between sound and carious enamel
and dentin.46
Further work is required to determine if
the fluorescence signal from exposure to infrared
irradiation is greater than that from other wavelengths.
Additionally, any heating effects from absorption
of infrared irradiation may have potentially damaging
effects on the dental pulp, given the increased
penetration and decreased scattering of the longer
wavelength. Specific coherent sources of such irradiation
have been relatively difficult to acquire, and detection
involves the use of infrared-sensitive detectors as CCDs
or film.
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6. 173
Terahertz Pulse Imaging: This method uses waves
with tetrahertz frequency(=1012
Hz or a wavelength
of approximately 30µm) for an image to be obtained
by tetrahertz irradiation, the object is placed in the
path of the beam. It is possible to record tetrahertz
images using CCD detector. It has no adverse thermal
effects, it is non ionising low signal to noise ratio, but
the cost of equipment is high, and careful interpretation
is required. Dental Applications for this technique
have been limited but promising. Longitudinal sections
through three teeth have demonsrated increased
terahertz absorption by early occlusal caries and an
apparent ability to discriminate dental caries from
idiopathic enamel hypomineralisation. Work in progress
to image intact teeth with early carious lesion.47
Multiphoton Imaging: Infra red light of 850 nm has
been used for multiphoton imaging of teeth. In
conventional fluorescence imaging (QLF), a single blue
photon is used to excite a fluorescent compound in the
tooth. In the multiphoton technique two infrared photons
(with half the energy of blue photon) are absorbed
simultaneously. With this technique, sound tooth
tissue fluoresces strongly, whereas carious tooth tissue
fluoresces to a much lesser extent. In practice, by using
motors with micron accuracy, one can move the plane
of focus through the tissue and record the sectional
images from the tooth to form a 3D image. Caries will
appear as a dark form with in a brightly fluorescing
tooth. To highlight the diseased tissue, the image may
be displayed in its negative form so that caries appear
bright with in dark tooth.
Time-Correlated Single-Photon Counting Fluorescence
Lifetime Imaging:
It has also been demonstrated that fluorescence lifetime
imaging microscopy (FLIM) has the ability to distinguish
the carious region from sound dental tissue.48-50
Optical
bandpass interference filters were then applied to this
broad-bandwidth source to select the 488 nm excitation
wavelength required to perform TCSPC FLIM of dental
structures. The white-light generation source provides a
flexible method of producing variable-bandwidth visible
and ps-pulsed light for TCSPC FLIM. The results from the
dental tissue indicate a potential method of discriminating
diseased tissue from sound, but stained tissue, which could
be of crucial importance in limiting tissue resection during
preparation for clinical restorations.
CONCLUSION :
Current research and new technologies have extended
the dentists’ armamentarium to detect early lesions
of caries. It is suggested that laser fluorescence is the
leading technology there is, At the current state of
development, early caries detection tools such as QLF,
Electronic caries monitor, DIAGNODENT, DIFOTI or
FOTI should be used as an adjunct to clinical decision
making and serve primarily as a support tool for making
preventive treatment plan decisions in conjunction
with caries risk assessment. It is important that all these
tools be used as diagnostic adjuncts to aid in early
caries detection and not as a justification for premature
restorative intervention. However, a need to further
extend knowledge and understanding of other techniques
Diagnostic method Advantages Disadvantages Clinical application
Optical
coherence tomography
(OCT)
1)Canbeusedtoquantitatively
monitor the mineral changes
in a caries lesion.
2) Can determine depth of the
lesion.
Regions of high light
backscattering not related
to caries development
can lead to false-positive
results.
Imaging of interproximal and
occlusal caries, early root caries,
and for imaging decay under
composite fillings.
Polarized Raman
Spectroscopy (PRS)
1) PRS is a noninvasive
spectroscopic method that
provides details on the
biochemistry and molecular
structure of white spot
lesions.
2) There is no need for
external dyes.
However, factors in the
oral environment such as
calculus,hypocalcification,
and stain could lead to
false-positive results.
Used in conjuction with OCT
for better result.
Fibre Optic
Transillumination
1)Non ionising.
2) Gives instant images.
1) Subject to intra and
interobserver variations.
this is overcome by The
Midwest Caries I.D.™
2) Calculus and hypoca
lcifications are major
confounding factors.
For detection of approximal,
occlusal and smooth surface
caries.
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7. 174
Quantitative Light-
induced Fluorescence
1) can provide quantitative
parameters such as lesion
area, depth, and volume.
2) The image can be stored
for longitudinal study.
1) It cannot differentiate
between decay and
hypoplasia.
2) It has inability to detect
or monitor interproximal
lesions.
3)Has Limited depth
measurement.
Has applications in clinical
trials, research, patient
education, and preventive
clinical practice. Can effectively
monitor demineralization and
remineralisation of teeth invitro
Also can be used to measure
erosive potential of a range of
mouth washes in vitro. To see
early secondary caries beneath
the amalgam restorations.
Laser-induced
Fluorescence:
1) Easy and quick to use.
2)Safe and no x-ray exposure.
1)Tooth surfaces and
fissures being assessed
should be clean and dry.
2)No evidence present
for the detection of
approximal or secondary
caries adjacent to existing
restorations.
The device performs best on
smooth surfaces and in occlusal
pits and fissures.
Transillumination with
Near-Infrared light:
1)Less amount of back
scattering
2) Can be easily differentiated
from stains, pigmentation,
and hypomineralization
(fluorosis).
More studies over the
damaging effects on the
pulp needed.
A promising imaging technique
for detecting
the presence of caries and
measuring its severity
Near-Infrared reflectance
imaging
1)The ability to map the
lesion distribution rather
than obtaining single-point
measurements,
2)Non-invasive, noncontact,
and stain insensitive.
More studies over the
damaging effects on the
pulp needed.
For quantitative caries diagnosis
and can determine the presence
of occlusal enamel and dentin
lesions.
Infrared fluorescence Non-invasive, noncontact,
and stain insensitive.
More studies over the
damaging effects on the
pulp needed.
For quantitative caries
diagnosis.
Terahertz Pulse Imaging 1)Relative transparency of
human tissue to terahertz
rays.
2) Adverse thermal effects
are thought to be unlikely.
Care is require in image
interpretation since
terahertzwavesarestrongly
absorbed by water.
Dental applications for this
technique are limited but
promising.
Multiphoton Imaging Able to collect information up
to 500 microns in depth.
It can cause harm to tissues
but it is over come by
using ultra short pulses.
Currently the technique has been
performed only on the extracted
teeth.
Time-Correlated Single-
Photon Counting
Fluorescence Lifetime
Imaging
Relatively safe compared
to two photon excitation
method.51
To obtain high-quality data
acquisition, times up to 30
minutes have been used.
It is possible to differentiate
between carious and sound
regions by time-resolved
fluorescence and that, although
the origin of enamel fluorescence
is still uncertain, the lifetime
values seem to be typical of
fluorophores like collagen I.50
N.K.Prabhakar et al.

8. 175
in the field of dentistry is needed. Unfortunately no
one device has all the advantages and can be called as
ideal. But with the available information following
conclusions can be drawn as presented in table
New devices do offer promise in the monitoring of early
incipient lesions of caries, and therefore preventive
dentistry techniques may be more appropriately targeted
and assessed.
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Correspondence:
Dr.N.K.Prabhakar,
Room no.4, Department of Conservative Dentistry and Endodontics,
Government Dental College and Research Institute,
Bangalore, Karnataka, India.
Email id:prabhakar.naik0000@gmail.com
Non-Invasive Methods For Caries Diagnosis