PERIAPICAL RADIOGRAPH

DENTAL X-RAYS

X-rays are produced by “boiling off” electrons

from a filament (the cathode)and accelerating

the el to the target at the anode. The

accelerated x-rays are decelerated by the

target material, resulting in bremsstrahlung.

History of X-Ray

DISCOVEY

Wilhelm Conrad Roentgen, Bavarian

physicist,

discovered the x-ray on 1895.

In 1895, German dentist Otto Walkhoff

made the 1st dental radiograph.

In 1895, New York physician made the 1st

dental radiograph in the united states using

the skull.

Characteristics of x-rays

•Invisible and undetectable by the senses.

•No mass or weight.

•No charge.

•Travel at speed light.

•Travel in straight line.

•Absorbed by matters.

•Cause ionization.

•Cause certain substances to fluoresce.

•Can produce image on photographic film.

•Cause changes in living cells.

Radiograph in dentistry

X-rays in dentistry serves as the most important diagnostic tool.

Radiograph in dentistry are divided into two:

1. Intraoral radiograph.

2. Extraoral radiograph.

Inrtaoral radiograph

Intraoral X-rays are the most common type of

X-ray

It is used mainly for:

>Detection of caries.

>Check the health of the tooth root

and bone surrounding the tooth.

>Check the status of developing teeth.

>Monitor the general health of your

teeth and jawbone.

Types of intraoral radiograph

Bite-wing X-rays : Bite-wing X-rays are used to

detect decay between teeth and changes in bone

density caused by gum disease.

Periapical X-rays : Periapical X-rays are used to

detect any abnormalities of the root structure and

surrounding bone structure.

Occlusal X-rays show full tooth development

and placement

Extraoral radiograph

Panoramic X-ray

Tomograms

Cephalometric projections

Sialography

Computed tomography,

General guidelines on patient

care

For intraoral radiography the patient should

be positioned comfortably in the dental chair,

ideally with the occlusal plane horizontal and

parallel to the floor.

Spectacles, dentures or orthodontic appliances

should be removed.

A protective lead thyroid collar should be placed.

Intraoral film packets should be positioned

carefully to avoid trauma to the soft tissues.

Indications of periapical

radiography

Detection of apical infection/inflammation

Assessment of the periodontal statue

After trauma to the teeth and associated

Alveolar bone

Assessment of the presence and position of

Unerupted teeth

Assessment of root morphology before

Extractions

During endodontics

Preoperative assessment and postoperative

Appraisal of apical surgery

Detailed evaluation of apical cysts and other

lesions within the alveolar bone

Evaluation of implants postoperatively

Ideal positioning

requirements

The desired tooth and film should be in contact

or as close together as possible.

The tooth and the film should be parallel to

each other.

The film packet should be place vertical for

anterior teeth and horizontal for posterior and

sufficient film space beyond the apices should

be present.

They tube head should be placed so the beam

meets the tooth at right angle.

The positioning should be reproducible.

Radiographic techniques

• The paralleling technique

• The bisected angle technique.

Paralleling technique

The film packet is placed in a holder and

positioned in the mouth parallel to the long

axis of the tooth.

The X-ray tubehead is then aimed at right

angles (vertically and horizontally) to both the

tooth and the film packet.

To prevent the magnification (since the film are

located at distance) a large focal spot to skin

distance, by using a long spacer cone or

beam-indicating device (BID) on the X-ray set.

A) a short cone and a diverging X-ray beam B) a long cone and a near-parallel X-

ray beam.

Positioning techniques

Selection of appropriate holder

Incisor and canine - Anterior holder

- Small film packet

(22*35mm)

Premolars and Molars – Posterior holder

- large film packet

( 31*41mm)

Smooth white surface of the film packet must

face towards the x-ray tube head.

The patient is positioned with the head

supported and with the occlusal plane

horizontal.

Packet film position

Maxillary incisors and canines : positioned

posterior to enable its height to be

accommodated in the vault of the palate.

Mandibular incisors and canines :

positioned in the floor of the mouth,

approximately in line with the lower canines or

first premolars.

Maxillary premolars and molars : placed in

the midline of the palate.

Mandibular premolars and molars : placed in

the lingual sulcus.

The holder is rotated so that the teeth under

investigation are touching the bite block.

A cottonwool roll is placed on the reverse side

of the bite block. This keeps the film and the

tooth parallel .

The patient is requested to bite gently

together.

The locator ring is moved down the indicator

rod until it is just in contact with the patient's

face.

The spacer cone or BID is aligned with the

locator ring. This automatically sets the vertical

and horizontal angles and centres the X-ray

beam on the film packet.

The exposure is made.

Bisected angle technique

The film packet is placed as close to the tooth

under investigation as possible without

bending the packet.

The angle formed between the long axis of the

tooth and the long axis of the film packet is

assessed and mentally bisected.

The X-ray tubehead is positioned at right

angles to this bisecting line with the central ray

of the X-ray beam aimed through the tooth

apex.

Using the geometrical principle of similar

triangles, the actual length of the tooth in the

mouth will be equal to the length of the image

of the tooth on the film.

Vertical angulation of the X-ray tubehead

The angle formed by continuing the line of the

central ray until it meets the occlusal plane

determines the vertical angulation of the X-ray

beam to the occlusal plane.

Horizontal angulation of the X-ray tubehead

The central ray should be aimed through the

interproximal contact areas, to avoid

overlapping the teeth.

Positioning techniques

Using film holders

The film packet is pushed securely into the

chosen holder.

The X-ray tubehead is positioned.

Exposure is made.

Advantages of the paralleling

technique

Geometrically accurate images are produced

with little magnification.

The shadow of the zygomatic buttress appears

above the apices of the molar teeth.

The periodontal bone levels are well

represented.

Periapical tissues shows minimal

foreshortening or elongation.

Crown of the teeth shows approximation of the

caries.

The horizontal and vertical angulations of the

X-ray tubehead are automatically determined

by the positioning devices if placed correctly.

The X-ray beam is aimed accurately at the

centre of the film — all areas of the film are

irradiated and there is no coning off or cone

cutting.

Reproducible radiographs are possible at

different visits and with different operators.

Disadvantages of the paralleling

technique

Positioning of the film packet can be very

uncomfortable for the patient, particularly for

posterior teeth, often causing gagging.

Positioning the holders within the mouth can

be difficult for inexperienced operators.

The anatomy of the mouth sometimes makes

the technique impossible, e.g. a shallow, flat

palate.

The apices of the teeth can sometimes appear

very near the edge of the film.

Positioning the holders in the lower third

molar regions can be very difficult.

The technique cannot be performed

satisfactorily using a short focal spot to skin

distance (i.e. a short spacer cone) because of

the resultant magnification.

The holders need to be autoclavable or

disposable.

Advantages of the bisected

angle technique

Positioning of the film packet is reasonably

comfortable for the patient in all areas of the

mouth.

Positioning is relatively simple and quick.

If all angulations are assessed correctly, the

image of the tooth will be the same length as

the tooth itself and should be adequate (but

not ideal) for most diagnostic purposes.

Disadvantages of the bisected

angle

technique The many variables involved in the technique

often result in the image being badly distorted.

Incorrect vertical angulation will result in

foreshortening or elongation of the image.

The periodontal bone levels are poorly shown.

The shadow of the zygomatic buttress

frequently overlies the roots of the upper

molars.

The horizontal and vertical angles have to be

assessed for every patient and considerable

skill is required.

It is not possible to obtain reproducible views.

Coning off or cone cutting occur.

Incorrect horizontal angulation will result in

overlapping of the crowns and roots.

The crowns of the teeth are often distorted,

thus preventing the detection of approximal

caries.

The buccal roots of the maxillary premolars

and molars are foreshortened.

Positioning difficulties

Mandibular third molars .

Gagging .

Endodontics .

Edentulous alveolar ridges .

Children .

Patients with disabilities .

Digital radiography

Digital radiography is a form of imaging x-ray

where digital X-ray sensors are used instead

of traditional photographic film.

There are two major variants of digital image

capture devices: flat panel detectors (FPDs)

and high-density line-scan solid state

detectors.

Indirect FPDs. Amorphous silicon (a-Si) is

the most common material of commercial

FPDs. Amorphous silicon combines with

caesium iodide(CsI) or gadolinium

oxysulfide (Gd2O2S), and converts X-rays to

light.

Direct FPDs. Amorphous selenium (a-Se)

FPDs are known as “direct” detectors because

X-ray photons are converted directly into

charge.

High-density Line-scan

Detectors

A high-density line-scan solid state

detector is composed of a photo stimulable

barium fluorobromide doped with europium

(BaFBr:Eu) or caesium

bromide (CsBr) phosphor.

Advantage of digital

radiography

Elimination of chemical processing and

associated errors.

Reduction in radiation dose.

Computer storage and archiving of patient

information.

Transfer of images electronically.

Image enhancement and manipulation.

Disadvantage

Cost

Reduced resolution

Quality of hard copy prints

Image storage

Image security

Limited size of sensor available

Lack of sensor flexibility

Lack of training at both undergraduate and postgraduate levels.

Comparison of direct digital and

conventional intraoral radiographs in

detecting alveolar bone loss

Background. Intraoral radiographs are

important diagnostic aids in periodontics. The

authors conducted a study to compare

estimates of bone levels from direct digital and

conventional radiographic under normal clinical

use.

Methods. A full-mouth series of

conventional radiographs was taken for each

of 25 subjects who had periodontitis. A long

cone paralleling technique was used for

periapical, or PA, images, and a paper sleeve

with biting tab was employed for bitewing, or

BW, images. A set of direct

digital radiographs matching the

conventional radiographs was taken for each

subject under the same conditions.

Results. Examiners measured 857 PA image

sites and 315 BW image sites matched on

both radiographic systems. Paired t test

showed significant differences in bone levels

between the two systems.

conventional PA images were higher in all

maxillary sextants (P ≤ .02), and

measurements from digital PA images were

higher in mandibular anterior sextants (P =

.007).

In digital BW images were higher in

mandibular posterior sextants (P = .002)

A χ2 analysis of categorical bone levels

(normal, early-to-moderate loss or advanced

loss) showed significant differences between

the imaging systems in revealing bone levels

in both PA (P< .04) and BW (P < .001) images.

Digital radiographs showed a higher number

of sites with bone loss than the

conventional radiographs.

Conclusions. Under normal clinical use,

alveolar bone levels revealed on intraoral

direct digital radiographs differ from those

revealed on conventional radiographs.

Clinical Implications. Intraoral direct

digital radiographs are not an equivalent

substitute for conventional radiographs in

evaluating alveolar bone levels.