Date post: | 03-Jul-2015 |
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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.