FLOW CHART 1. Introduction. 2. Ideal Requirements of diagnostic tests 3. Traditional methods for diagnosing caries: a.
Visual examination.
b.
Tactile evidence of caries-probing
c.
Tooth separation.
d.
Dental floss.
e.
Conventional radiography.
4. Newer methods: a.
Xero radiography.
b.
Digital imaging.
c.
Computer image analysis.
d.
Subtraction radiography.
e.
Electrical resistance.
f.
Fiberoptic transillumination.
g.
Digital FOTI.
h.
Laser auto fluorescence.
I.
Ultraviolet illumination.
j.
Endoscopy.
k.
Ultrasonic detection.
l.
Dye penetration method.
5. Conclusion. CARIES DIAGNOSIS
INTRODUCTION
Dental caries: social & financial health problem
Loss of minerals from sub surface zone of enamel & ends
in cavitation.
Accurate diagnosis of very incipient stage of carious
lesion-reversal by proper interventional measures.
Diagnosis of occlusal caries: increase in usage of
fluoridated dentifrice
Surface enamel remaining intact overlying a slowly
progressing “occult” lesion.
Need of better diagnostic methods for occlusal caries.
Ideal requirements of diagnostic tests: 1. Accurate. 2. Sensitive. 3. Specific. 4. Reproducible. 5. Reliable. 6. Not transfer S. Mutans or other bacteria from affected area to unaffected areas. 7. Cost effective. Traditional Methods
2
Visual Examination:
Looking for cavitation, surface roughness, opacification
& discoloration.
Problem: discoloration of the pits & fissures may be a
universal finding in normal healthy adult teeth, which may be mistaken for the presence of caries. Tactile Evidence of Caries: Explorer.
Determining roughness or softness of tooth surface with
a sharp explorer. Both penetration & resistance to removal of an explorer tip have been interpreted as an evidence of demineralization
Probing has been criticized & questioned because of
several reasons: 1. May transmit cariogenic bacteria from one site
to
another. 2. May
produce
irreversible
traumatic
defects
in
potentially remineralizable enamel. 3. May not be able to add any information to the visual examination. 4. Mechanical binding of an explorer tip not be because of caries but
in a fissure
may
because of other causes like:
a.
Shape of the fissure.
b.
Sharpness of an explorer.
c.
Force of application.
3
Dental Floss: disadvantage is that overhanging restorations on the proximal side also give the same features. Conventional Radiographs: ď Ž
An examination of dental caries cannot be considered adequate
without
a
proper
radiograph.
The
use
of
radiograph must be interpreted with caution as it presents a 2 dimensional picture of a 3 dimensional object. Another aspect is that net mineral loss must exceed atleast 20%30% in order to be radiographically visible. Other problems encounter with radiographic methods
ď Ž
are: 1. Overlapping of approximal contacts. 2. False diagnosis due to overestimation of which may appear to be increased
due
lesion to
depth
change
in
angulations. 3. Radiolucency on a radiograph cannot be judged that is because of caries or
whether
resorption or any other defect
i.e. wear, etc. 4. A superficial demineralization in the buccal surfaces may be imaged on the
&
radiograph
lingual as
an
approximal carious lesion. 5. Fracture of one lingual cusp may appear as
radiolucent
approximal cavity. 6. Tilt of maxillary lateral incisors appears as caries mesial side of lateral incisors. 4
on
the
7. Cervical burnout may mimic cervical caries. Radiographic interpretation of occlusal caries is always associated with limitations such as: 1. Caries in enamel becomes more difficult to detect because of superimposition of enamel over the fissures. 2. Lesions
involving
buccal
grooves
of
molars
are
superimposed over the occlusal area & can simulate occlusal lesions. 3. A thin radiolucency appears at the DEJ in occlusal caries, which, many a times, is missed considering it to be a normal difference of radiolucency in enamel & dentin. 4. It becomes difficult to distinguish between occlusal caries & internal resorption. Problems in diagnosis of secondary caries : 1. Lesions on the occlusal surface, between restoration & enamel cannot be visualized until reached to an advanced stage.
Discoloration
of
margins
as
an
evidence
for
secondary caries may not be applicable to all restorative materials as discoloration can be due to extrinsic stains or corrosion products also. ď Ž
Radiographs can diagnose the cervical portion of the interproximal lesions, which is a prime site for secondary caries,
but
careful
comparison
with
radiographs is a must before concluding.
5
the
previous
3. It is often difficult to differentiate between secondary caries & caries which has been left during restoration ( residual caries).
NEWER METHODS Xeroradiography:
Simulates the photocopying machine.
Image is recorded on an aluminium plate coated with a
layer of selenium particles.
Selenium particles are given a uniform electrostatic
charge and are stored in a unit called conditioner.
When X-rays are passed on to the film, it causes
selective discharge of the particles
Xeroradiography is twice as sensitive as conventional
D-speed films and a phenomenon of 'Edge Enhancement' is possible with this technique.
Edge enhancement means differentiating areas of
different densities especially at the margins or edges. Disadvantages of this technique are: The electric charge over the film, many a times, causes discomfort to the patient since the oral cavity has a humid environment, which acts as a medium for flow of current. The process of development can't be delayed and Is to be completed within 15 minutes.
6
Although Xeroradiography technique seemed to be promising, but features of edge enhancement etc. were soon taken over by fast developing digital imaging systems.
DIGITAL IMAGING
A digital image is an image formed and represented by a
spatially distributed set of discrete sensors and Pixels. When viewed from a distance, the image appears continuous, but closer inspection reveals individual pixels.
Image that has been recorded with non film receptors.
Digital Image Receptor works on a charged couple
device
(CCD),
which
is
electronically
connected,
to
a
computer.
CCD is a semiconductor made up of metal oxides such as
silicon that is coated with x -ray sensitive phosphorous.
CCD is sensitive both to x-rays and visible light. The
intraoral DIR is placed in the mouth instead of the x -ray film.
The image area is limited by the size of the CCD present
in the digital image receptor.
Once the image is captured by the CCD, (like an image
of silver halide crystals in an X -ray film) it can be can be stored in the computer memory for image processing and can be displayed for viewing.
Digital radiography systems available commercially.
Radio-Visio-Graphy (RVG) (Trophy -Japan)
7
Flash Dent (Villa -Italy)
Sens-A-Ray (Regarn -Sweden)
Advantages: 1. Darkroom is not required, instant image is viewed. 2. The quality of image is consistent. 3. Elimination of the hazards of film development. 4. Radiation dose is decreased. 5. Capability for teletransmission Disadvantages 1. High cost of system 2. The life expectancy of CCD is not fixed.
Contrast can be enhanced by digital mode. Digital mode can enhance density and contrast upto
70%.
Digital method is 50% more sensitive in detecting
occlusal caries as compared to conventional films.
Wenzel et al-compared (CCD based units):
Trophy RVG
Sens-A-Ray
Visualix
Phospor storage plate (PSP) based units
8
Detection of occlusal caries: performed almost equally
well.
Radiography is of no value in detection of initial enamel
lesions or for detection of approximal dentinal lesions, however, especially for lesions known to be confined to enamel. COMPUTER IMAGE ANALYSIS
Softwares
have
been
developed
for
automated
interpretation of digital radiographs in order to standardize image assessment.
These programs are based on the "expert system" which
contains facts about the pathologic conditions.
The clinician enters the patient's data and the programme
compares the patient's data with the basic knowledge of the pathology. Advantages 1. Automated analysis may provide
sensitive and objective
observation of smaller lesions which otherwise are not perceptible to naked eye. 2. It is possible to monitor the lesion. Disadvantages 1. There is always a need for standardization of exposure geometry. 2. Sensitivity is higher but specificity is lesser.
9
3. Time consuming and less economical. Subtraction Radiography
Structured noise is reduced in order to increase the
detectability of changes in the radiographic pattern.
Structured noises are the images, which are not of
diagnostic value and interfere in routine interpretation of radiographs.
Digital Subtraction Radiography has overcome many of
the limitations of photographic images.
Digitization is, achieved by taking a picture of the
radiograph using high quality video - camera. This is fed to computer-imaging
device,
termed
as
digitizer.
Two
standardized radiographs produced with identical exposure geometry are used.
The
first
one
is
the
‘Reference
Image’
and
the
subsequent images are for comparison.
The reference image is displayed on the screen.
Then the subsequent images are superimposed.
The difference between the original and the subsequent
images will show as dark bright areas, which can be interpreted readily.
Digitization does not increase the information available
in the original radiograph. Only, it turns the image into a form, which can be read by the computer.
Digital Subtraction Radiography is 90% accurate in
detecting as little as 5% mineral loss of bone compared to the 10
30-60% of the mineral content of the bone that has to be lost before a radiographic lesion could be seen on a conventional radiograph.
Electrical resistance
1878-Magitot.
Sound tooth enamel is a good electrical insulator due to
its high inorganic content.
Caries / enamel demineralization results in increased
porosity.
Saliva fills these pores and forms conductive pathways
for electric current.
The electric conductivity is hence directly proportional
to the amount of demineralization that has occurred.
Electrical
resistance
is
measuring -
the
electrical
conductivity) through these pores.
2 instruments (1980s):
1. Vangaurd electronic caries detector.
2. Caries Meter L.
Measured electrical conductance between tip of probe
placed in fissure & a connector attached to an area of high conductivity.(gingiva or skin)
Measured conductance –continuous variable-converted to
an ordinal scale:0 to 9 for Vangaurd system. 4 colored lights for caries mater L:
Green-no caries 11
Yellow-enamel caries.
Orange-dentin caries.
Red-pulpal involvement.
Vangaurd: 25 Hz.
Caries meter: 400 Hz.
Vangaurd: moisture & saliva removed by continuous
stream of air to prevent surface conductance.
Caries meter L: pits & fissures moistened with saline-to
assure a good electrical contact & to minimize effect of saliva. Advantages 1. Very effective in detecting early pit and fissure caries. •
It can monitor the progress of caries during caries control programme.
•
Verdonschot et diagnosing
al: high sensitivity & specificity
occlusal
caries.(compared
to
in
clinical,
radiographic, FOTI) •
Amount of airflow-level of sensitivity & specificity. 7.5L/M, ensitivity-92% & specificity-82%.
Disadvantages
It can only recognise demineralization and not caries
specifically.
The
hypomineralization
areas
may
be
of
developmental origin or carious origin will give similar type of readings.
12
Presence of enamel cracks may lead to false positive
diagnosis. A sharp metal explorer is utilized which is pressed into the fissure causing traumatic defects.
Separate measurements are required for different sites
making full mouth examination quite time consuming.
A modified form of the Instrument 'Electronic Caries
Monitor' not only detects caries at a single point on tooth but also can screen whole of the occlusal surface for caries by covering the surface Fibre Optic Trans Illumination (FOTI) Fibre optic Trans Illumination (FOTI) works under the principle that since a carious lesion has a lowered index of light transmission , an area of caries appears as a darkened shadow that follows the spread of decay through the dentine.
Fiberoptic consists of a halogen lamp and a rheostat to
produce a light of variable intensity.
Two attachments are used; a plane mouth mirror mounted
on a steel cuff and a fiberoptic probe of 0.5 mm diameter so that it can be placed in the embrasure region.
It produces a narrow beam of light for transillumination.
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
13
lingual surface depending on the tooth. The marginal ridge is viewed from the occlusal surface.
A shadow extending to the 'dentino -enamel junction
beneath the marginal ridge may be evident if there is a break in the integrity of the enamel of marginal ridge. Advantages * No hazards of radiations. * Simple and comfortable for the patients. * Lesions, which cannot be diagnosed radiographically, can be diagnosed
by this method.
* Not time consuming. Disadvantages * Permanent records are difficult to maintain as can be kept in radiographs. * It is subjected to Intra and Inter observer variations. * Difficult to locate the probe in certain areas. Digital FOTI
Resultant changes in light distribution as light traverses
the tooth –recorded as an image for analysis.
FOTI- high level of intra & inter examiner variability.
Reduced
shortcomings
of
digital CCD camera.
14
FOTI-combining
FOTI
&
In
vitro
comparison
of
DIFOTI
to
conventional
radiographs: DIFOTI twice sensitive in detecting approximal lesions & 3 times as sensitive in detecting occlusal lesions.
Buccal-lingual lesions: sensitivity 10 times that of
conventional radiographs.
Detect incipient or recurring caries before they are
visible on radiographs. LASER AUTO FLUORESCENCE (LAF)
Light scattering: measure of observed whiteness of a
carious lesion –correlated with degree of mineral loss.
Benedict-fluorescence of organic components of human
teeth-differential in fluorescence between sound & carious enamel.
In this, visible light has been used as the light source for
the detection of smooth surface and fissure caries at an early stage. (Bjelkagen et al., 1982).
Tooth is illuminated with a broad beam of blue green
light of 488 nm wavelengths from an argon ion laser and the fluorescence observed in the 540 nm range.
This fluorescence of enamel occurring in the yellow
region (540 nm) is observed through a yellow high pass filter to exclude the tooth scattered blue light.
Vaarkamp et al: HeNe laser (633 nm) –light scattering in
enamel :hydroxyapatite crystals;in dentin: tubules.
In vitro caries model: LF good correlation with LMR. 15
Demineralized areas appear darker. Healthy tooth fluoresces differently from that of carious
tissue impregnated with fluorescent dyes.
Demineralized tissues absorb dyes like Fluorol TGA,
Sodium fluorescein etc and fluoresce strongly. This is referred to as dye enhanced laser fluorescence. Advantages
It is convenient and a relatively fast method. Carious lesions can be detected and their mineral loss
measured.
Lesions with a diameter of less than 1 mm and a depth of
5 10 mm have been
detected
and
measured
with
this
technique.
Preventive measures can be evaluated.
It is developed for quantification of enamel changes.
Diagnodent:
A laser diode provides pulsed light of a defined
wavelength that is directed onto the tooth.
When the incident light meets a change in tooth
substance,
it
stimulates
fluorescent
light
of
different
wavelength.
This is translated thro the hand piece into an acoustic
signal, & the wavelength is then evaluated by appropriate electronic system in the diagnodent control unit.
16
Ultraviolet Illumination
Ultraviolet light (UV) has been used to increase the
optical
contrast
between
the
carious
region
and
the
surrounding sound tissue.
Natural fluorescence of tooth enamel, as seen under UV
light illumination is decreased in areas of less mineral content such as in carious lesions, artificial demineralization or developmental defects.
Carious lesion appears a dark spot against a fluorescent
background. Advantages It is more sensitive method than the visual tactile method. Disadvantage The specificity is a problem between the carious lesion and the developmental defect. Endoscope/Videoscope
Endoscopic
technique
is
based
on
observing
the
fluorescence that occurs when tooth is illuminated with blue light in the wavelength range of 400 -500 nm.
Difference is seen in the fluorescence of sound enamel
and carious enamel.
When this fluoresced tooth is viewed through -a specific
broadband gelatine filter, white spot lesions appear darker than enamel 17
Similarly a white light source can be connected to an
endoscope by a fiberoptic cable so that the teeth can be viewed without a filter. This technique is referred to as white light endoscopy. It has been demonstrated in vitro that this technique
allows visualization of small carious lesions in the enamel that are difficult to detect with the naked eye or with radiographs. Additionally, a camera can be used to store the image. The integration of the camera with the endoscope is called a videoscope. A
miniature
colour
video
camera
is
mounted
in
a
custom-made metal mirror holder. This is designed in such a way that the image of the surface of enamel can be viewed directly over a television screen. The videotapes are viewed by expert ind1pendent examiners who
had
also
examined
the
teeth
visually
and
conventional methods. Advantages It provides a magnified image. Clinically feasible. Disadvantages Requires meticulous drying and isolation of teeth. Time consuming. Very costly. 18
by
Ultrasonic imaging Ultrasonic imaging was introduced for detecting early carious lesions in smooth surfaces. The demineralization of natural enamel is assessed by ultrasound pulse echo technique . It is observed that there is a definite correlation between the mineral content of the body of the lesion and the relative echo amplitude changes. The ultrasonic probe is used which sends longitudinal waves to the surface of the tooth and also serves the function of receiving the waves. Initial white spot lesions, which extend only upto enamel, produce no or weak surface echoes. The sites with visible cavitation produce echoes with substantially higher amplitude. Dye Penetration Method
The observation of the colouring can be qualitative or
quantitative.
For a qualitative assessment, it is sufficient to observe
for colour or differentiate coloured objects from the non coloured ones.
For a quantitative assessment, the intensity of colour is
to be determined.
The total area, which is coloured, can be compared with
the uncolored area. 19
The Intensity of colour can be determined by absorption
or fluorescence.
Absorption can be measured by quantitating the decrease
of light intensity at a particular wavelength
Fluorescence
can
be
measured
by
quantitating
the
increase of light intensity at a particular weave length.
In caries diagnosis, qualitative examination is sufficient;
observation of coloured dye signifies presence of caries.
Dyes should fulfill the following criteria before being
recommended for clinical use. I. Dyes should be absolutely safe for intra oral use. II. Dyes should be specific and stain only the tissues it is intended to stain. III. Dyes should be easily removed and not lead to permanent staining. Dyes for detection of carious enamel
'Procion' dyes stain enamel lesions but the staining
becomes irreversible because the dye reacts with nitrogen and hydroxyl groups of enamel and acts as a fixative.
'Calcein' dye makes a complex with calcium and remains
bound to* the lesion. 'Fluorescent dye' like Zyglo ZL -22 has been used in vitro which is not suitable in vivo. The dye is made visible by ultraviolet illumination.
'Brilliant blue' has also been used to enhance the
diagnostic quality of fiberoptic transillumination.
20
Dyes for detection of carious dentin
Histopathologically, carious dentin is divided into two layers- outer layer of decalcification, which is soft and cannot be remineralized and the inner decalcified layer, which is hard and can be remineralized.
Dyes have been tried to differentiate between then two zones of dentin caries. 0.3% Basic Fuchsin In propylene glycol has proved to be successful for the purpose.
Demineralized dentin in which the collagen has been
denatured is stained while the inner one remains unstained.
This method is recommended as a clinical guide for
complete removal of the outer carious zone in dentin caries as it contains denatured collagen.
Basic Fuchsin dye was considered to be carcinogenic;
therefore it has been replaced by acid red and methylene blue.
Methylene blue is also slightly toxic so acid red is
preferred. A modified dye penetration method
'The Iodine penetration method' for measuring enamel
porosity of the incipient carious lesions was developed by Bakhos et al. (1977).
Potassium iodide is applied for a specific period of time
to a well-defined area of the enamel and thereafter the excess is removed.
21
The
iodine,
which
remains
in
the
micropores,
is
estimated and that indicates the permeability of enamel.
Sensitivity & specificity of caries detection methods
CONCLUSION
At a cross roads in caries detection.
Older methods of caries detection are no longer adequate
but newer methodologies are still being developed or are not yet widely disseminated.
Development of newer methodologies of caries detection
are critical to reduce the possibility of incorrect diagnosis, which will ultimately lead to an incorrect decision.
Without newer methods of caries detection, people who
are at low risk for caries progression may receive needless treatment.
Where as other high risk groups may be overlooked,
resulting in an undue waste of manpower, time & money.
22