Wei Fan ,DDS MSc ,PhD,* Bing Fan,DDS MSc ,PhD
James L gutmann,DDS ,PhD ,FACD,FADI* and Mingwen Fan, DDS JOE volume 34, number 10, October 2008
Presented by :Francis Prathyusha
Why x-ray ?
Successful root canal treatment is highly dependent on
through management of root canal anatomy.
Radiographs are reliable clinical method of determining
canal anatomy .
Canal anatomy, canal length, quality of obturation , bone
pathology can be identified and monitored
Standard intra oral radiograph using silver halide film is
used widely.
Disadvantages : Exposure to radiation
Complicates radiographic assessment – radiographs
may differ in
1. Brightness
2. Contrast
3. Acquisition geometry
Time consuming
Cannot manipulate
Storage of chemicals
Direct digital systems
Dawn of the digital era in dental radiography came in
1987 when the first digital radiography system called
Radiovisiography, was launched in Europe by the
French company Trophy Radiologie.
The inventor of this system was Dr. Francis Mouyen.
He invented a way to employ fiber optics to narrow
down a large x-ray image onto a smaller size that could
be sensed by a Charge Coupled Device (CCD) image
sensor chip.
Fundamental Principles of Digital Radiography
Digital radiography refers to a method of capturing a radiographic image using a sensor, breaking it into an electronic pieces, and presenting and storing the image using a computer.
In stead of having an analog radiographic image on a film, in digital imaging the sensor is used to receive the analog information and through analog-to-digital converter (ADC) to convert it to a digital image that is an array of picture elements called pixels, with discrete gray values for each one.
Special software is used to store and manipulate the digital image in the computer. The image is displayed within seconds or minutes on the computer screen in front of the clinician and the patient/client..
Equipment
• Computer
• Intra oral sensor
1. Charge-coupled device (CCD)
2. Complementary metal oxide semiconductor/active pixel sensor
(CMOS/APS)
3. Charge injection device (CID)
• X-radiation source
Note: Intraoral sensor is composed of a silicone
chip and a layer that surrounds it. A layer above the sensor chip is the scintillator (material that emits light when particles traverse it), which converts x-ray energy into light and directs it towards the top layer of the chip that is more sensitive to light than x-rays. Top layer of the chip then releases electrons that form the image and send them onto the well in the lower portion of the chip. The energy in each well is then read and digitized with an A/D (analog to digital) converter during the read-out process.
Advantages
Ease and speed of use
Reduction in time between exposure and image
interpretation.
Less radiation to patient
Elimination of chemical waste hazard
Ability to digitally manipulate the captured image
Ability to copy and duplicate without loss of image quality
Colourization , as well as manipulation with contrast,
sharpness, image orientation and pseudocolour alteration
Less physical storage space required
Easy in recording and rapid storage and retrieval
Disadvantages
Cost effective
Sensors are the weak part of the system due to their
relative rigidity and thickness
Sensors are not universal and interchangeable
between different systems.
Digital sensors can’t withstand heat sterilization,
therefore they require complete coverage with
disposable plastic sleeves
Digital radiographs have legal issues because of
their potential for fraudulent use
DSR The efficiency of RVG system lies primarily in the identification of image
features buried in back ground of normal anatomic structures.
Reduction of background noise can be achieved by DSR – which eliminates the identical image regions in series of radiographs obtained in the same exposure position and at different time intervals.
Subtraction radiography is a very sensitive method, because it cancels out the anatomical noise
Note:
Digital subtraction radiography
Anatomical noise are the structures that are in the image, but are not influenced by the pathology that has to be
detected. The irregular trabecular pattern, for instance, will influence the detectability of bone lesions.
Confused ?????
Changed anatomic structures – stand out clearly
Unchanged anatomic structures–eliminated
Image was made immediately after extraction of a maxillary molar
This image was made one month later
The subtraction -reveals areas of bone loss in black and bone deposition in white .
Contrast medium in DSR
To change the radiopacity of some anatomical
structures before DSR
Many methods used to introduce a water soluble
radiographic contrast medium
1. Injecting the medium in to canal
2. Placing the teeth under a vacuum to pull the
medium in to the canal irregularities
MICRO CT SCAN
USE
Evaluate the canal shapes or cross section of teeth
Diagnose or evaluate the location and size of
periradicular lesion
Determining morphologic changes before and after
the instrumentation.
Images obtained could be reconstructed by using
specialized software.
C shape canal
The C refers to distinct pulp chamber anatomy
that contains one or multiple canals connected
by a slit or fin.
Mandibular 2nd molars
It commonly extends from the M-Li extent of the
chamber to the D-Li, but can be the opposite (M-
B to D-B w/ the C inverted).
Study The purpose of this study was to
investigate the ability of DSR to reveal
anatomic features of c shape canal system
in mandibular second molars with the aid
of intra radicular contrast medium
MATERIALS AND METHODS
30 mand.molars – fused roots + deep lingual groove on the
root surface
Stored in 10% formalin solution
Scanned with µCT 20(scanco medical , bruttisellen, Switzerland)
From crown to apex at0.5mm intervals.
3 dimensional canal configuration of each tooth was
reconstructed by using 3D doctor software.( able soft-ware
corp,,lexingotn,MA)
Referred as a gold standard for assessment of subsequent
canal image reading
AFTER SCANNING Pulp chamber accessed – engine driven fissure bur
Unroofed with an Endo Z bur(dentsply surrey ltd, UK) to gain
the unimpeded entry to the canals and to prevent
cutting on the chamber floor.
Pulp extirpation- fine barbed broach
Teeth soaked in 5% of NaOCL solution – 30 mints
Canals irrigated – 20ml distilled water
Jet of water from apical foramen indicated patency
Without visible jet of water not then canals were
instrumented with No.20 light speed ( light speed technology inc
,San Antonio ,TX)
20ml -5% Naocl and 20ml distilled water
IMAGING
Roots were covered with sticky wax to seal the
canals
Teeth were put onto the same radiographic device
RVG digital images taken with mandible plates in
the same way .
The vacum device was used – 76% compound
meglumine distrizoate( xudong haipu pharmaceutical Co Ltd)
Now RVG images were taken
Imaging During exposure- position should be strictly kept
unchanged
1. Teeth
2. Bone plates
3. X-ray tube
4. RVG charged- couple device.
X-ray exposure time – 0.16 sec
A 4mm wide step wedge made of aluminum 1100
was fixed onto the jig 3mm above the occlusal
surface of the teeth as the reference standard of
radiographic density in all images
Hmmmmmmmmmm…
Questions running in your mind
Where is the wedge
Where is the tooth
Where are the bony plates
Position???
An illustration of the radiographic device
X ray tube
Radiograph or CCD
Aluminum wedge
Mandibular bone plates
Charge-coupled device (CCD)
This is one of the most common image receptors in digital
radiography, an old technology and is used in many other
devices like fax machines, video cameras, microscopes
and telescopes. The CCD is a sensitive to x-rays or light, it
is a solid-state detector that contains a silicone chip with an
electronic circuit embedded in.
Imaging
The step wedge – 10 steps with 2mm as step span
All images were stored in a comp
Images before and after - overlapped and subtracted
Subtraction by software 3D doctor
All DSR images and buccal lingual reconstruction
canal images based on CT scanning were classified
by 3 categories.
TYPES
Type I merging Type 2 symmetrical
Type 3 asymmetrical
Classification based on
DSR images & µCT reconstruction
Observation methods Type 1 Type 2 Type 3
DSR 11 11 8
Reconstruction 12 9 9
The kappa value, which was subject to the U test for
significance at p= 0.05, was calculated to be 0.85,
The classification based on reconstructed images were
used as the standard to evaluate the sensitivity (se) and
specificity ( Sp) of DSR image construction
Results were subjected to the wilcoxon statistical test
The statistical significance was considered at p<0.05
RESULTS
The results based on DSR images and reconstruction
There were no significance differences
Se and Sp of DSR images of type 1
High Se and Sp
Only one tooth with a reconstructed type 1 canal image was classified as non type 1 or type 2 on DSR images.
DSR
classification
Reconstruction total
Type 1 Type 2
Type 1 11 0 11
Non-type 1 1 18 19
total 12 18 30
DSR based type 2 has high Se and Sp
Two teeth with reconstructed non type 2 (type 1 & 2 )
canal images was classified as type2 on DSR images
DSR recons Total
Type 2 Non type 2
Type 2 9 2 11
non Type 2 0 19 19
Total 9 21 30
Se and Sp of DSR images type 2
Se and Sp of DSR images in type3
Se and Sp are high
Only 1 tooth with reconstructed type 3 canal image
was classified as non type 3 ( type2).
DSR reconstrcu Total
Type 3 Non type 3
Type 3 8 0 8
Non type3 1 21 22
Total 9 21 30
DISCUSSION
Identifying the potential complexity of the canal anatomy is a major pre requisite for successful canal treatment.
Complicated morphology – image super imposition of hard tissue surrounding it.
CT scan diagnose the canal anatomy -But the dissolution of the image is not yet high enough to show irregular or fine canal and
Exposure to relatively high dosage of x ray radiation .
Discussion
The contrast medium enhance s the radiopacity of target tissue images against surrounding tissues.
Intra radicular contrast medium improved canal identification even when image superimposition existed
The identification was lacking when compared with reconstructed images
DSR applied to get better image
Discussion
DSR has 2 requirements
Contrast variation in serial images
Strict repetition of serial positions
DSR is still a 2 dimensional- angulations
Eg: Reco type 3 – 1 tooth – DSR type 2
Cleaning should be proper – distribution of medium
Eg: Reco type 1 – 1 tooth – DSR type 2
Resolution : Complete emptying of tissue debris from canal via
irrigation and dissolution
Using more effective method of introducing and distributing the medium.
CONCLUSION Some of the most important benefits this technology
offers include patient education, time efficiency,
reduced exposure to radiation and environmentally
friendly set up. Although DSR has been applied in
medical and dental areas - Assessing augmentation
of alveolar bone crest , the variation of periapical
pathosis, canal resorption the application and
related evaluation of DSR in canal anatomy
identification , especially in C shape canal system
have not been yet explored
DSR IS A POWERFUL TOOL FOR DENTAL PRACTICE
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