INTRODUCTION: Diagnosis “is the determination of the nature of a diseased
condition,
by
careful
investigation
of
its
symptoms and history”. Arriving at a correct diagnosis requires knowledge, skill
and
art;
knowledge
of
the
disease
and
their
symptoms, skill to apply proper test procedures and the art of synthesizing impressions, facts and experience into understanding. Symptoms are the units of information sought in clinical diagnosis. They
are
defined
as
phenomena
or
signs
of
a
departure from the normal and indicative of illness. They are classified accordingly. Subjective
symptoms
–
those
experienced
and
reported by patients. Objective
symptoms
–
those
ascertained
by
the
clinician through various tests. It thus follows that the corners or pillars of a correct clinical diagnosis are A.
Good case history.
B.
A thorough clinical examination.
C.
Relevant investigations / diagnostic tests. In order to obtain a good case history, record of
substantial data with relation to the patient’s medical and dental history is of great importance.
1
HISTORY: Medical history: Although the only systemic contraindications to endodontic therapy are uncontrolled diabetes or a very recent myocardial infarcation, only the patients medical history enables the clinician to determine the need for a medical consultation or premedication of the patient. Additional barrier protection can be provided to all clinical personnel if the patients history reveals infection with communicable disease such as AIDS, hepatitis-B, TB etc. Before rendering endodontic therapy the clinician must know what drugs the patient is using to identify possible adverse drug reaction. Dental history: The primary aim in recording the patient’s dental history is to obtain complete information data of the patient’s chief complaint. Most common chief complaints range from -
Pain
-
Swelling
-
Loss of function
-
Aesthetics
Pain is one of the most common chief complaints encountered. Pain: When patients present with a history of pain careful attention is paid to their description. In order to attain a detailed knowledge regarding pain following questions may be necessary 1)
Type of pain: Grossman
has
stated
pulpal
pain
to
be
of
the
following two varieties i.e. a)
Sharp, piercing and lancinating – A painful response usually associated with the excitation of A-
2
Delta nerve fibres. This pain usually reflects reversible state. b)
Dull,
boring,
gnawing
and
excruciating
–
a
painful response usually associated with the excitation of
C-nerve
fibres.
This
pain
usually
reflects
an
irreversible state of pulpitis. 2)
The duration of pain: When the pain is of a shorter duration (1 minute), it
is considered to be reversible pulpitis, whereas when the pain
is
of
a
longer
duration
it
is
considered
to
be
irreversible pulpitis. 3)
The localization of pain: Sharp piercing pain can usually be localized and
responds to cold. Dull pain usually referred / spreads over a larger area and responds more abnormally to heat. 4)
Factors which provoke / relieve pain (Int. Endo. J. 1990). On response
assessment to
a
of
provoking
pulp
vitality
factor
(e.g.
by on
A.H.
Rowe
mastication)
indicates pulp vitality, but stimulation causing extended severe pain suggests irreversible pulpitis. Different
diagnosis
of
reversible
and
irreversible
pulpitis
1. History 2. Pain
Reversible pulpitis
Irreversible pulpitis
Slight sensitivity or occasional pain
Constant or intermittent pain
Momentary and immediate, sharp in nature and quickly dissipates after.
Continuous, delayed onset, troubling persists for minutes to hours
3
after removal of stimulus.
3. Location of pain
May be localized and is not referred
Pain is not localized. If it is localized only after periapical inv. pain is referred.
4. Lying down (change of posture)
No difference
Marked prolonged
5. EPT
Early response
Early, delayed or mixed response.
6. Thermal test (Heat and cold)
Responds
Marked prolonged
Negative
Negative in early stages, later positive when periapex is inv
Negative
May show widening of PL space.
7. Percussion
8. Radiography
Clinical examination: This phase can be divided as A)
Extraoral examination
B)
Intra oral examination The extra oral clinical examination begins with a
patient’s dental history, while talking to the patient, the clinician should look for facial asymmetry or distensions, which would indicate a swelling of odontogenic origin or a systemic ailment. INTRA ORAL EXAMINATION: This begins with a general evaluation of the oral structures. Several tests have been stated in order to
4
determine
the
condition
of
teeth
and
supporting
structures. Commonly used methods are 1)
Visual and tactile and inspection
2)
Percussion
3)
Palpation
4)
Mobility and depressibility tests
5)
Periodontal tests
6)
Thermal tests
7)
Anaesthetic tests
8)
Test cavity
9)
Transillumination
10)
Biting
11)
Staining
12)
Gutta-percha point tracing
13)
Electric pulp testing
14)
Radiographs
Special methods: 1)
Xero-radiography
2)
Pulse-oximetry
3)
Laser Doppler flowmetry
4)
Computerised tomography
5)
Digital subtraction radiography
6)
MRI
7)
RVG
8)
Computerized expert system
9)
Thermographic imaging
10)
Tact
Commonly used methods
5
Visual and tactile perception The simplest clinical test is visual examination. A thorough visual and tactile examination of hard and soft tissues relies on checking the 3 C’s. Colour Contour Consistency The visual and tactile inspections is usually carried out with a mouth mirror, explorer, and a periodontal probe
under
dry
conditions
with
a
good
illumination
source. The
teeth
and
the
soft
tissues
adjacent
to
the
involved tooth must also be examined for detection of any related swelling and pathologic conditions. Preparation Palpation is a tactile skill acquired through practice and repetition. Before incipient swelling becomes clinically evident, it may be detected by gentle palpation with the index finger. This simple test is done with the fingertip using light pressure to examine tissue consistency and pain response. Its value lies in locating the swelling over the involved tooth and determining the following. i)
Whether
the
tissue
is
enlarged sufficiently for incision and drainage and is fluctuant. ii)
The presence, intensity and location of pain.
6
iii)
The presence and location of adenopathy.
iv)
The
presence
of
bone
crepitus. Percussion: This test enables one to evaluate the status of the periosteum surrounding the tooth. The tooth is struck a quick moderate blow initially with the finger and then by the handle of the mouth mirror. A positive response to percussion indicates not only the presence of inflammation of the PL but also the degree of inflammation. The degree of response is directly proportion to the degree of inflammation. Responses to percussion: Positive response to percussion periodontitis, which could be due to
is
indicative
-
Teeth underlying rapid orthodontic movement.
-
High points in resent restoration.
-
Lateral periodontal abscess.
-
Partial / tooth pulpal necrosis.
of
Negative response to percussion may be seen in cases of -
Chronic periapical inflammation – it has been stated that percussion sounds offer diagnostic clues.
-
Dull Note signifies abscess formation sharpt Note denotes inflammation.
Mobility – Depressibility test: The rationale of mobility test is to evaluate the integrity of the attachment apparatus surrounding the tooth. The test essentially consists of moving the involved tooth laterally in the socket using handles of 2 instruments or more preferably using two index fingers.
7
The test for depressibility is similar and is performed by applying pressure in an apical direction on the occlusal / incisal aspect of tooth and observing vertical movement in any.
8
Grades of mobility (Cohen) (Grossman): 1 s t degree – less than 1mm horizontal movement. 2 n d degree – 1mm of horizontal movement. 3 r d degree – greater than 1mm of horizontal movement accompanied by vertical depressibility. Grades of mobility (Miller) 0 – No mobility within physiologic limits 1 – Mobility within the range of 0-5mm. 2 – Mobility within the range of 0.5 to 1.5mm with lateral movement. 3 – Mobility more than 1.5mm with lateral movements and can be intruded / depressed into the socket. Mobilometers: These are electronic devices / gadgets, which and in determining tooth mobility. Periodontal examination: No clinical examination is complete without careful evaluation of the tooth’s periodontal support. Multirooted teeth should be carefully evaluated to determine whether there is any evidence of furcation involvement. A lateral canal exposed to the oral cavity through a periodontal disease may become the portal of entry for toxins, which may cause pulpal degeneration. Thermal tests: Thermal tests are especially valuable diagnostic aids because in certain types of inflammed pulps pain may be induced or relieved by applying cold or warm stimuli. Reliable response to pulp vitality testing are critical and depend on the teeth being dry. Grossman has stated that a response to cold reflects a vital pulp regardless of whether it is normal or abnormal. A heat test does not confirm vitality. An abnormal response to a heat test however exhibits presence of a pulpal or periapical disorder requiring endodontic treatment.
9
Another
diagnostic
difference
as
pointed
out
by
Grossman is that when a reaction to cold occurs the patient can quickly point out to the painful tooth. Unlike in
a
heat
test
situation
where
the
response
can
be
localized diffused or even referred to different site. Heat test: The
heat
techniques,
test which
can
be
deliver
performed different
using
different
degrees
of
temperature. The preferred temperature for performing a heat test (according to Cohen) is 65.5°C or 150F. Heat test may produce a temperature as high as 150 degree centigrade at the surface of the tooth according to AHR Rowe et al (in an article on assessment of pulpal vitality) (Int End J. 1990 V-23), where temperature upto 150°C according to him are necessary for conducting thermal tests on teeth which are 1 s t coated with Vaseline to avoid gutta-percha sticking to the tooth. The
heat tests can be performed using different
techniques such as 1. Hot air 2. Hot water 3. Hot burnisher 4. Hot gutta-percha 5. Hot compound 6. Polishing of crown with rubber cup For teeth with crowns hot water is better. Here the tooth to be tested is isolated using a rubber dam and immersed in ‘Coffee hot’ water delivered from a syringe.
10
Disadvantage – Limited only to the tooth which is tested. Cold test: Cold application can be performed in any of the following ways (i.e.). A)
A stream of cold air from a 3-way syringe directed against the crown of previously dried tooth.
B)
Use
of
ethyl
chloride
spray
(which
evaporates
rapidly) absorbing heat and cooling the tooth surface. C)
Application of ice sticks (sticks of ice are seldom used because they may warm when applied to the tooth
and
leak
onto
the
gingiva,
causing
a
false
positive response. D)
Cold water bath – They are more time consuming but are clearly superior in their accuracy. Even when the tooth has been restored with a full crown sufficient contact is made to allow cooling or warming of the pulp. In addition the cold water bath prevent excessive
temperature- change damage to the tooth. E)
Carbon dioxide snow (77.7°C or –108°F) (odontotest) and / or
F)
Refrigerant dichlor – diflour methane (-50°C Figen / Frigident). According to Chambers (1982), the advantage of CO 2
show vitality testing are its Ease and speed of application and its reliability. The method has been reported to be more reliable than other methods for testing the vitality of immature developing
permanent
teeth
and
traumatically
injured
anterior teeth – Fulling and Anderson 1976 and Ehimann 1977.
11
The
CO 2
snow
also
produce
a
distinct
vitality
response in teeth covered with metal crowns precluding the use of test drills. In addition, false positive vitality reactions have not been reported in teeth with liquefaction necrosis. Ehrmann
(1977)
has
claimed
that
the
test
is
ineffective in teeth with calcified pulps or in those of elderly patients with large deposits of reparative dentin. However Schroeder (1981) has claimed that even degenerative and atropic pulps will react to cold. Augsburger and Peters (1981) found that intra pulpal temperature, as measured in vitro decreased only by a mean of 15.6째C for non carious teeth. In gold crowned teeth the decrease was 13.2째C after a 5 sec exposure. Their clinical studies indicated that a 2 second exposure produced
a
vital
response.
Histologic
studies
have
indicated that the pulp is not damaged by the application of the CO 2 snow test (Schiller 1937). Fuss and associates in an in vivo study comparing tooth vitality, produced a positive vitality response of 98.7% with dichloro-difluoro methane, 97.4% CO 2 snow, 94.8% with electric pulp tester, 53.2% with ethyl chloride and 32.5% with ice. CO 2 dry ice sticks are extremely cold and may cause infarcation lines in enamel (Cohen) but Ehrmann has stated that if it does occur it will not be of clinical significance. Rickoff reported that CO 2 did not damage the surface of but does cause pitting of the surface porcelain or PFM.
12
Responses to thermal tests: The patient’s response to heat and cold test are identical because the neural fibres in the pulp transmit only
the
sensation
Brannstorm).
of
pain
There are
(Hydrodynamic
4 possible
theory
reactions that
–
the
patients may experience (Cohen) 1.
No response – maybe non-vital or vital but giving a negative
response
due
to
excessive
calcifications,
immature apex, recent trauma, patient medication etc. 2.
Mild to moderate degree of awareness of slight pain that subsides within 1 or 2 seconds after the stimulus has been remove – Normal limits.
3.
Strong momentary painful response subsides when the stimulus in removed – reversible pulpitis.
4.
Painful
response,
which
lingers
after removal of
stimulus – irreversible pulpitis. Modification of techniques for thermal tests: A modified technique for thermal tests is provided by the analytical pulp tester, which has a hot probe tip and a cold probe tip. The heating of the hot probe tip and cooling of the cold probe tip are controlled separately by the membrane switches on the control panel. Selective anesthetic testing: Selective anesthetic refers to administration of a local anesthetic to facilitate identification of the tooth causing a painful episode. If
the
source
of
pain
cannot
be
differentiated,
maxillary block should be given (along with palatal). If the pain vanishes, the maxillary tooth is identified as the causative
agent,
otherwise
the
mandibular
tooth
is
indicated as the source of the problem.
13
The maxillary tooth is selected for the initial injections because of the greater degree deep anesthesia is normally obtainable in the maxillary arch. The likelihood of missing a mandibular block inj is always present (Weine). If teeth in the same arch are to be identified inject the posterior most tooth in the suspected zone. If the pain still persists after tooth has been completely anesthetized, then anesthetize the next tooth mesial to it and continue to do so until the pain disappears. Test cavity: This test allows one to determine pulp vitality. It is performed when other methods of diagnosis have failed. The test cavity is made by drilling through the enamel – dentin junction of an unanesthetized toth. The drilling should be done at slow speed and without a water coolant. Sensitivity or pain felt by the patient is an indication of pulp vitality; no endodontic treatment is indicated. If no pain is felt, cavity preparation may be continued until pulp chamber is reached. If the pulp is completely necrotic endodontic treatment can be continued painlessly in many cases without anesthesia. Transillumination test: Emergence of the fibreoptic as a dental instrument has been a great aid in the use of transillumination for diagnosis. The test requires shining a bright light from the lingual or palatal surface of a tooth, with viewing in a darkened room. In teeth with necrotic pulps the shadow of the pulp canal space appears darker than the rest of the tooth because of the breakdown of the blood cells. Periapical tissue may be similarly transilluminated if the plates of bone are clone to each other as in mandibular anterior teeth. Teeth with radiolucencies reveal a shadow around the apex, whereas normal teeth show no difference.
14
Transillumination may be helpful in diagnosing the presence of a vertical fracture. With the fiber optic shining at right angles to the fracture line, the segment of the tooth on the side of the crack illuminates whereas the segment on the far side remains dark (Weine). Occlusal pressure test (Ingle) (Biting test): A frequent complaint is pain on biting or chewing. A clinical test that stimulates the chief complaint is the occlusal pressure test (or biting test). Different methods are -
Orange wood stick
-
Tooth slooth
-
Burlew disk (rubber
-
Wet cotton roll The 1 s t 3 allow to pin point testing of individual cusp
areas while the wet cotton roll has the advantage of adapting to the occlusal surface allowing for pressure over entire occlusal table. This test is useful in identifying teeth with symptoms of apical periodontitis abscess or cracks. An interesting clinical observation in patients with tooth infarcation (cracked tooth syndrome) is pain is often experienced when biting force is released rather than during the downward chewing motion. Staining: There are 2 methods to stain a tooth 1)
Remove the filling from the suspected tooth and place 2% iodine in the cavity preparation. The iodine stains the fracture line dark.
2)
Mix a dye with ZnOE and place it in the cavity preparation after filling has been removed. The dye will seep out and colour the fracture line.
15
3)
Have a patient chew a disclosing tablet after taking out the filling in the suspected fractured tooth. The line will be stained. Purpose of staining is to detect cracked tooth syndrome.
Gutta-percha point tracing with a radiograph: Purpose: Can localize the endodontic lesion to the specific tooth. In addition, this test aids in the differential diagnosis between a periodontal and an endodontic lesion. Electric pulp testing: The EPT is a valuable tool in differential diagnosis. Historically,
the
E.P.
tester
has
been
used
in
dentistry as early as 1867 and has evolved over the years into the present electronic digital pulp tester. The electric pulp tester is designed to stimulate a response by electrical excition of the neural elements within the pulp. According to Cohen, it is the real determinant of vitality. According to Seltzer, pain elicited by the electric pulp tester is a poor indicator of the status of the pulp. According to Cooley and Robinson 1980 the pulp tester actually helps to determine the pulp vitality or nonvitality and not the condition of the pulp. Advantages of EPT: 1)
Intensity of stimulus is comfortable to the patients.
2)
The
digital
display
of
many
EP
testers
provide
instant, easy and reliable information. 3)
In some GP testers, a red indicator flashes on and off when maximum stimulus is reached.
4)
Gives a quantitative reading and can be compared with the normal reading on the control group.
16
Disadvantages: 1)
Cannot be used on patients having Cardiac pace maker.
2)
Usually cannot be used when gloves are work.
3)
Some EPT equipments are very expensive.
4)
EPT is not useful for recently erupted teeth with immature apex. This may be because the relationship between the odontoblasts and the nerve fibres of the pulp has yet to develop (Nicholls).
5)
Recently traumatized teeth cannot be tested.
6)
The probe tips of some EP tester is removable and falls out easily.
7)
No indication is given regarding state of vascular supply which would give a more reliable measure of the vitality of the pulp.
8)
Readings from posterior teeth with partially vital pulps may be misleading. The results obtained from EPT could be misleading
and these could be grouped as A)
False positive response – when the pulp is necrotic but patient gives a positive response.
B)
False negative - when the pulp is vital, but the patient is unresponsive to the EPT.
Reasons for false positive: 1)
Conductor / electrode in contact with a metallic restoration or gingiva along with the current to reach the attachment apparatus.
17
2)
Patient anxiety.
3)
Liquefaction necrosis.
4)
Failure to isolate or dry the tooth.
5)
In multirooted teeth where the pulp may be partially necrotic.
Reasons for a false negative response: 1)
Patients
heavily
premedicated
with
analgesics,
narcotics, alcohol, tranquilizers. 2)
Inadequate contact with enamel.
3)
Recently traumatized tooth.
4)
Excessive calcification in the canal.
5)
Recently
erupted
tooth
with
an
immature
apex
(Nicholls). Types of pulp testers: 2 main verities are available (Nicholls) i)
Bi-polar
ii)
Monopolar Mono
polar
pulp
testers
are
most
commonly
employed for this purpose. Another method of differentiating pulp testers (Nicholl) 1) Whether current is varied 2) Whether voltage is varied The former is preferable since a given voltage may lead to different amounts of current due to variation in electrical resistance of tissues especially enamel. The common commercially available pulp testers are;
18
1)
Analytic technology pulp tester: In which the wave form has an output in the form of
bursts of 10 high frequency pulses followed by a space. This
is
reportedly
done
to
minimize
the
patient’s
discomfort. The EPT is turned on automatically when the probe touches the tooth and is turned off when the tooth contact is broken (after a delay of 15 seconds). The analytical pulp tester has a special end fitting probe design with which pulp testing of crowned teeth may be achieved. -
Digilog pulp tester
-
Green wood pulp tester
-
Pelton crane tester
-
Parkell pulp tester (Battery operated) a)
Digitest
b)
Gentle pulse (Parkell product)
Analytic technology
-
a)
Vitality scanner
b)
Endonanalyzer
Evident / pulpdent -
Trilite Hygenic corp.
-
Pulppen Sienmens AG
-
Sicotest Mada equip Co.
-
Digipex II
Aamdent -
Neo otest
Dahlin -
Dentometer
19
RADIOGRAPHY: One
of
radiographs,
the permit
most
important
visual
diagnostic
examination
of
aids,
the
oral
structure that would otherwise be unseen by the naked eye. In
the
sequence
of
examination
radiographic
evaluations should come last. Radiograph is a 2 dimensional representation of a 3dimensional object. Normal
landmarks
/
information
observed
on
radiographs. This includes -
Crowns of each tooth.
-
Curvatures of root.
-
Lamina dura of each root.
-
Bony architecture.
-
Quick change of RC colour on the radiograph from dark
to
light
may
indicate
a
bifurcation
or
trifurcation. -
Anatomic landmarks – mental and incisive foramina, mandibular canal maxillary sinus etc.
-
Presence of caries, that involve or threaten to involve the pulp. While observing roots one should look for periapical
lesions and other root defects such as a) Fractures. b) External and internal resorption. c) Pulp stones. d) Linear calcifications. e) Open apices. f) Bony defects.
20
The radiographs have certain limitations. It has been stated
that
lesions
of
the
cancellous
bone
are
not
discrenable on the radiograph until the cortical bone has been reached or penetrated. This has been confirmed by studies by Bender, which state that such lesions are only visible on the radiograph when atleast 6.6% of the cortical bone in the direct path of the x-ray beam has been destroyed. Also the periapical lesions are usually larger than that seen on radiographs. Lesions within the tooth observable by radiographs: a)
Pulp death in a developing tooth is readily apparent as the root ceases to develop.
b)
Pulp stones – inflammation
c)
Internal resorption (after) seen following traumatic injury.
Lesions outside the tooth observable or radiographs: a)
Widening of PL space occurring due to –
Acute apical periodontitis.
–
Acute apical abscess.
–
Occlusal trauma.
b)
Changes associated with chronic periapical abscess.
c)
External root resorption.
Special diagnostic methods: Because of the inadequacies of the electric pulp testers, other modalities have been tried in an effort of correlate
some
parameters
of
disease
processes
with
clinical testing procedures.
21
ULTRASONICS (SELTZERS): Attempts
have
been
made
to
detect
pulpitis
by
ultrasonic means but with little success – (Krisoff and Sharpe 1966). The problem is that little information is available relative to the acoustic properties of dental hard tissues, mainly because of the crudity of the instrumentation. With an improved instrument, the transmission and reflection of sound from the DEJ and from the dentin pulp interface has been recorded (Barber et al 1969). With continued improvement it is conceivable that an ultrasonic diagnostic tooth will be perfected. INFRARED THERMOGRAPHY: Alterations in the temperatures of diseased bodily structures have been detected with sophisticated infrared thermographic equipment. It has been assumed that teeth with vital pulps would have higher surface temperatures than those with necrotic pulps. Crandell and Hill (1966) found that by the use of an infrared thermometer, there were no difference between the surface temperature of teeth with normal pulps and those of pulpless teeth. LIQUID CRYSTAL TESTING: Howell et al 1970 have attempted to employ the colour of cholisteric liquid crystals applied to the surfaces of the teeth as a diagnostic modality. There are 3 types of liquid crystal, termed nematic, smectic
and
cholisteric
according
to
their
molecular
arrangement, (Ferguson 1964). The molecules of cholisteric crystals are arranged in layers. Changes in temperature or pressure alter the pitch
22
and period of the helical structures, so that new colours are produced. Cholisteric
crystals
can,
therefore,
serve
as
the
active elements in devices that map the distribution of temperature. LASER DOPPLER FLOWMETRY: LDF was introduced (1972 – Riva, Ross, Benedek) as a non-invasive method to measure the blood flow. The
crux
of
LDF
is
based
on
the
detection
of
movement of blood cells in the pulpal blood vessels (and not on neural responses) which thus gives a true picture regarding pulp vitality. The technique consists of a laser at 632.8nm and is focused on the tissue study with a fiberoptic probe. As the light hits various components of the tissues it is partially absorbed and partially back scattered. The back scattered light has 2 components 1) Light back-scattered from static tissue which has the same frequency as the light going in 2) The other component is the Doppler shifted light with a different frequency. The back scattered light is processed and an output signal is produced (i.e.) both the shifted and unshifted light is transmitted to a detector by optical fibres where it is converted into electric current and processed. The detected output signal can be fed into an analog printer, or be read from a digital board.
23
Advantages of LDF: 1.
Non-invasive
2.
Simple to apply
3.
Provides a continuous record
4.
Useful to demonstrate establishment of vitality of untreated teeth.
Disadvantages: 1.
Impossible to calibrate the readings in absolute units.
2.
Output may not be linearly related to blood flow.
PULSE OXIMETRY: Text relying on the passage of light through a tooth have been considered as a possible means of detecting pulp vitality with greater objectivity. Pulse oximetry is a relatively recent advancement in non invasive monitoring. It is a non invasive oxygen saturation monitor that also provides continuous pulse rate readings. The
liquid
crystal
display
(LCD)
gives
oxygen
saturation pulse rate (and plethysmographic waves from readings). Concept: wavelengths
in
Pulse order
oximetry to
uses
red
transilluminate
and a
infrared
tissue
and
detects absorbance peaks due to pulsative circulation and uses this information to calculate the pulse rate and oxygen saturation. The tooth being tested is sandwiched between a photoelectric detector and an LED (light emitting diodes) or red and infrared lights. This
method
is clearly superior
to other
vitality
testing methods since it does not rely on sensory nerve response.
24
XERO-RADIOGRAPHY (MARCO 1984): The term xero-radiography is derived from the Greek word
XEROS
differentiates
which
literally
x’radiograhy
means
from
dry
the
which
conventional
photochemical system. Technique: X’ radiography uses a rigid aluminium / selenium coated
photoreceptor
charged,
placed
in
plate. a
The
water
plate
proof
in
electrically
electric
cassette,
positioned in the mouth and exposed to the x-rays at a lower level of radiation. The entire process requires only 25 seconds for dry permanent image. The plates may be reconditioned, recharged and used repeatedly. Advantages: 1.
It produces sharper, clearer and finer details of the image.
2.
Reduced radiation dose is required.
3.
Pronounced
edge
enhancement
is
observed. DIGITAL IMAGING: Digital imaging in dentistry was 1 s t introduced for intraoral imaging. Despite the fundamentally different technology used in film-based imaging and in digital imaging, there are also many similarities between these 2 methods. Instead of silver halide grains, a small number of light sensitive elements is used to record the image data from the x-ray shadow. To display the image, different shades of gray are produced by the amount of light emitted from the monitor screen.
25
The difference between both methods is the fact that in
analog
randomly
radiographic dispersed
image
in
the
the
silver
emulsion,
grains
are
whereas
the
electronic elements of a digital sensor are arranged in a regular
grid
characteristics
of
rows of
the
and
columns.
light-sensitive
The
quantitative
elements
of
the
electronic sensor result in gray shades having discrete value. What is a digital image? The electric signal that is produced by the sensor is a voltage that is varying as a function of time. The sensor is connected to a special board in the computer called a frame grabber. The function of this board is to sample the signals at short intervals, thus converting the analog signal into a digital signal. The output of the measurements is stored as numbers. When the image is captured and digitized by means of an electronic sensor system, the radiation intensities are measured along a rectangular 2-dimensional grid of sensor elements called pixels (20-70mm). The outcome of the measurements of each sensor elements is transformed to the computer and stored as a number between 0-255. To display the image, the numbers are readout and used to control the intensities of the pixels on the monitor screen. The
purpose
of
an
x-ray
image
is
to
provide
radiographic information. The small pixels provide enough resolution to satisfy this requirement. The various methods to acquire a digital image.
26
1.
Conventional radiograph digitized using a flatbed scanner and transparency adapter.
2.
Conventional radiograph digitized using a charged coupled device camera.
3.
Semidirect
digital
image,
acquire
using
photostimulable phosphor plates. 4.
Direct
digital
complementory
image,
metal
acquired
oxide
using
semiconductor
a
CCD,
or
other
electronic device. Advantages: 1. Lower dose 2. Gain of time 3. Image processing – (Makes information more easily accessible for human eye). 4. Reconstruction (used to produce 3-D information. 5. Teleradiology
which
is
not
easily
available
from
conventional radiographs. Teleradiology
–
Is
also
a
good
example
of
the
advantage offered by digital imaging. Transmission of an electronic image over a phone line
or
over
the
internet
is
much
faster
than
the
traditional way of sending the radiograph by mail. Image compression: Digital
image
can
be
compressed
to
reduce
transmission time or storage requirements.
27
Ex traoral digital imaging: Nowadays extra oral digital imaging systems are also available. Similar to the intra oral sensor system, direct and semidirect sensor technology is applied for panaromic and skull radiography. Tomography photostimulable
is
possible
phosphor
only
plate
using
a
system,
semidirect
because
the
image data are collected over an area that is much larger. The 1 s t commercialized digital panaromic system was the Digipan, which was a modification of OPG 100 (CCD). The
1st
FDA
approved
photostimulable
phosphor
system (PSP) available in US was Denoptix system. Selected application for digital imagine in dentistry: Contrast processing: To detect differences in structures in a radiograph. When contrast is not sufficient it may be possible to enhance digital images to disclose pathology that would be undetected e.g. More accurate determination of size of PA radiolucency. For detection of simulated DC under orthodontic brackets. Automated diagnosis: The
movement
toward
artificial
interlligence
for
automated diagnosis has taken a huge step forward with the FDA’s approval of Logicon caries detector. The probability of a true positive for enamel and dentin lesions is indicated. Three dimensional imaging: 3D
imaging
is
not
limited
to
CT
or
magnetic
resonance imaging Webber has developed a new method of producing 3D images from series of 2D images. This system is termed as TACT.
28
Disadvantages: -
Expensive.
-
Rate
of
change
in
the
operating
platforms
and
processing software. Photostimulable phosphor radiography PPR: A new radiographic digital imaging technology (PPR) has potential to improve dental radiography and is likely to become common. The
technique is variously referred to as digital
luminescence radiography,
radiography, computed
storage
radiography
phosphate and
radio
luminography. In 1994 the first dental PPR system become available commercially (Digora). It is used for -
Caries detection
-
Alveolar bone imaging
-
PPR
system
provided
reliable
endodontic
measurements even at low exposure. PPR measurements were more accurate for assessing trial file length than were film based measurements. SUBTRACTION RADIOGRAPHY: It is a procedure in which a time –1 digital image of a specific anatomic area is subtracted from a time – 2 image of
the
same
anatomic
area.
What
remains
are
the
anatomic features that changed between time 1 and time 2. This is an image enhancement method, resulting in the area under focus being clearly displayed against a neutral gray background. It may be used to detect caries, success of RCT and condition of PA lesions.
29
Advantages of PPR: 1.
Storage phosphor plates can be reused indefinitely.
2.
Can be used with existing x-ray sources.
3.
Linear response to radiation is available.
4.
Wide exposure rage and fewer retakes.
5.
Less radiation requirement.
6.
No chemical processing.
7.
Can be processed to enhance features of interest and suppress interfering anatomic structures.
8.
Can be transferred to other site.
9.
Can be easily and inexpensively stored.
10.
Computer – aided diagnosis.
Disadvantages: 1.
Phosphor plates must be packed in sterile envelopes.
2.
Images may initially appear different from film based images.
3.
Display method is not optimal.
4.
Expensive
5.
They are at present time – intensive and may include the time need to make diagnosis.
Tomosynthesis: The principle of tomosynthesis is based on selective focusing
of
an
arbitrary
slice
through
the
object
by
shifting and adding a set of basis projections. LOCALISED COMPUTED TOMOGRAPHY: Localized CT (Micro-CT, radiograph micotomography) is base on the principle of CT, however, sampling volume and reconstruction of cross-sections are more relevant to dental applications.
30
TELERADIOGRAPHY: Definition radiology
–
defined
In
1994
the
American
teleradiology
as
the
college
of
electronic
transmission of radiologic images from one location to another for the purpose of interpretation, consultation or both. They have not been used as extensively in dentistry. RADIOVISIOGRAPHY (DR. FANCOIS MOYER): RVG
digitizes ionizing radiation and provides an
instantaneous image on a videomonitor thereby reducing radiation
exposure
by
80%.
RVG
equipment
has
a
fiberoptic intraoral sensor (with a selemium coated plate). Advantages: 1. Elimination of X-ray film. 2. Significant reduction in exposure time. 3. Instantaneous image display. The RVG has 3 components
a)
-
The ‘radio’ component x-ray unit.
-
The ‘visio’ portion.
-
The ‘graphy’ component. The
RADIO
component
consists
of
a
hypersensitive intraoral sensor and a conventional xray unit. b)
The VISIO portion consists of a video monitor and display processing unit.
c)
The GRAPHY component is a high resolution video printer that instantly provides a hard copy of the screen image using the same video signal. The RVG system appears to be promising for the
future of endodontics. But, the resolution of RVG is slightly lower than that produced with conventional terms,
31
which can however be improved through enhancement procedures. MAGNETIC RESONANCE IMAGING: Recently MRI has been tried out as a diagnostic tool in endodontics. Magnetic fields and radiographic waves are
used
fields
and
radiographic
waves
are
used
to
generate high quality cross-sectioned images of the body. MRI
works
on
electromagnetic
energy.
X-rays
involve
ionization. MRI can distinguish blood vessels and nerves from surrounding soft tissues. However this needs very large equipment. The high electromagnetic waves which are needed have not been approved of for use in scanners. It is believed that MRI machines will be developed for evaluation of odontogenic problems. Disadvantages – Not to be used in patients with cardiac pace makers metallic restoration orthodontic appliances aneurysms. COMPUTERISED TOMOGRAPHY: CT
is
a
radiographic
concept
of
thin
laser
technique
radiography
that
with
blends
the
the
computer
image. Techibana has reported about the used of CT in endodontics. It is possible to determine the buccolingual and mesiodistal widths of teeth and the presence or absence of root canal filling materials and metal posts. Also observable are the carious lesions, extent of the maxillary sinus and its proximity to the root apices. Advantages: Observation
of
structure
which
are
difficult
to
visualize with conventional x-ray. Provides images for 3D reconstruction of roots, root canals and teeth. Disadvantages: -
Expensive
32
-
Skin dose is large Time consuming.
Digital subtraction radiography: The
progress
of
caries
from
an
incipient
lesion
through the DEJ is often difficult to detect. Likewise the assessment
of
healing
or
expansion
of
the
periapical
lesion after RC therapy is a challenge because the subtle changes in the density of the lesion may not be detectable with the naked eye. Subtraction radiography offers a remedy for these problems.
This
is
an
image
enhancement
method,
resulting in the area under focus being clearly displayed against a neutral gray black background or it is super imposed on the radiograph itself (i.e.) required areas are enlarged against the entire background. The DSR may be used
to
assess
periapical
the
lesions
successfulness improved
of
through
RCT
and
also
enhancement
procedures. COMPUTERISED EXPERT SYSTEM – JOHN FIRRIOLA: The COMENDEX (CES) was used for the diagnosis of selected pulpal pathosis (i.e.) -
Normal pulps
-
Reversible pulpitis
-
Irreversible pulpitis due to hyper occlusion.
-
Irreversible pulpitis.
-
Necrotic pulp.
-
Infection due to endodontic failure. Appropriate diagnostic case facts are obtained and
this data is entered into the computer. The computer checks and gives out the diagnosis. With rapid advances
33
being made in the field of computers, we may get many more programmes for efficient endodontic diagnosis.
34
TACT – (TUNED APERTURE COMPUTED TOMOGRAPHY): This is a relatively new type of imaging device that may have advantage over current radiographic modalities in viewing an object while decreasing the superimposition of the overlying anatomical structures. The TACT system uses digital radiographic images and the TACT software correlates the individual images of a subject into a layering of images that can be viewed into slices. The ‘TACT’ image is composed of a series of 8 digital radiographs that are assimilated into are reconstructed TACT image. Preliminary studies have shown that TACT has advantages over conventional film in the visualization of canals in the human molar. The TACT system of imaging has also been proved to be an effective diagnostic tool for evaluating primary simulated recurrent dental caries and simulated osseous defects. With
the
advent
of
this
new
technology
the
practitioners has a new tool to diagnose external root resorption earlier than previous modalities and therefore include the likelihood of a favorable prognosis. REFERENCES: 01.
Endodontic Practice – Grossman.
02.
Endodontics – Ingle.
03.
Endodontic Therapy – Weine.
04.
Pathways of Pulp – Cohen, 7 t h Edition.
05.
Digital Radiography, DCNA -
06.
Recent
Advances
in
Diagnostic
methods
for
endodontic treatment – R.Nageswar Rao. 07.
The Dental pulp – Seltzer.
35