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