Radiograpy in pediatric dental patient

““RADIOGRAPHY IN PEDIATRIC DENTAL

PATIENT””

CONTENTS Introduction History of X-ray in dentistry Guidelines for prescribing radiographs in

children Behavioural consideration and

management techniques Radiographic techniques Newer digital radiographic techniques Radiation safety and protection Technical errors References

Introduction Definition- radiology

Plays a vital role in the diagnosis and treatment planning .

Plays a significant role in the assessment of growth and development.

At the simplest level, help in the detection of dental caries and at the most complex level, in the diagnosis of cysts, tumors or any other major craniofacial disorders.

History

Wilhelm Conrad

Roentgen1845 - 1923

The first radiograph – Mrs. Roentgen’s hand

Dr. Edmund Kells of New Orleans, Louisiana.

Dr Kells used impression compound to stabilized the film during exposure

Clinical situation for which radiographs are indicated

Positive Historical Findings a. History of painb. history of traumac. Familial history of dental anomalies d. Postoperative evaluation of healing e. Previous periodontal or endodontic

treatmentf. Unexplained tooth mobility

Positive Clinical Signs/Symptoms

Deep carious lesions Swelling Evidence of dental/facial trauma Mobility of teeth Sinus tract (“fistula”) Clinically suspected sinus pathology Growth abnormalities Oral involvement in known or suspected systemic disease Clinical evidence of periodontal disease Large or deep restorations

• Evidence of foreign objects • Pain and/or dysfunction of the temporomandibular

joint • Facial asymmetry • Abutment teeth for fixed or removable partial

prosthesis • Unexplained bleeding • Unexplained sensitivity of teeth • Unusual eruption, spacing or migration of teeth • Unusual tooth morphology, calcification or color • Unexplained absence of teeth • Clinical erosion

Radiographic Examination

Four film series: This series consists of a maxillary and mandibular occlusal radiographs and two posterior bitewing radiographs.

Eight film survey: This survey includes a maxillary and mandibular anterior occlusal radiographs. Four molar periapical radiographs. Two posterior bitewings

Twelve film survey: This survey include maxillary and mandibular

permanent incisor periapical radiographs. Four primary canine periapical radiographs. Four molar periapical radiographs. Two posterior bitewing radiographs

Sixteen film survey: This examination consists of the twelve-film survey and the addition of four permanent molar radiographs.

GUIDELINES FOR PRESCRIBING RADIOGRAPH

Guidelines for prescribing dental radiograhs for infants, children and adolescents and persons with special health care needs ; Ad Hoc committee on pedodontic radiology revised in 2009

Age Consideration Radiograph

3-5 No apparent abnormalities (open contacts)

No apparent abnormalities (closed contacts)

Extensive caries

Deep caries

None

2 posterior bite wings, size 0 film

4-film survey Selected periapical radiographs in addition to 4-film survey

Age Consideration Radiograph

6-7 No apparent abnormalities

Extensive or deep caries

8-film survey (available by 7 years of age)

Selected periapical radiographs in addition to 8-film survey

8-9

10-12

No apparent abnormalities or extensive or deep caries

No apparent abnormalities or extensive or deep caries

12-film survey

12 or 16 film survey depending upon size

Dental X-Ray Machine

Factors controlling X-Ray beam1. Tube Current (mA)2. Tube Voltage (kVp)3. Exposure time

Operating kilovoltage

Milliampere - Seconds

D E

low High Mean Low High Mean

70 6.7 10.9 8.8 3.6 4.8 4.2

90 3.1 10.9 4.6 1.7 2.6 2.2

Exposure time in pediatric patients

Tooth Time in Miliseconds(mS)

Maxillary 2nd molar 5201st molar 440Canine 370Incisor 280

Mandibular 2nd molar 4401st molar 380Canine 310Incisor 280

X-Ray Films

SPECIAL CONSIDERATIONS IN

YOUNG CHILD Introduce him to the “camera” Tell-show-do Careful words to describe the procedure Easiest region first Topical L.A. in case of exaggerated gag reflex Patience for repeated attempts Voice control, firmness & TLC Special handling for alternatively abled

children

If the child, less than three years of age it may be necessary for the child to sit in the parent’s lap while the radiograph is exposed.

Adequately protect the parent and child with lead aprons to reduce radiation exposure.

If the child is uncooperative, then additional restraint by a second adult may be necessary.

A second adult stabilizes the child’s head with one hand while the other hand positions the x-ray holder in the patient’s mouth. 

If a second adult is not available, it may be necessary to place the child in a mechanical restraining device (Papoose Board) to adequately restrain the child. 

If the child is still too uncooperative, it may be necessary to manage the child pharmacologically with inhalation, oral, or parental sedatives.

Older children may also be uncooperative for a variety of reasons. 

These can range from the jaw being too small to adequately accommodate the radiograph, fear of swallowing the radiograph, fear of the procedure itself, or the patient exhibits a severe gag reflex. 

For the child with the small mouth, use the smallest size film available (size 0 film).  Roll the film (do not place sharp bends) to allow the film to accommodate the shape of the jaw and not impinge on the soft tissues.

Positioning the Radiograph

vertical radiograph

By biting on the large positioning device and watching in a mirror they are assured they will not swallow the radiograph

A self sticking sponge tab may also reduce impingement of the radiograph on the intraoral soft tissue.

Desensitization TechniquesDesensitization is defined as gradually

exposing the child to new stimuli or experiences of increasing intensity. 

Another example of desensitization is the “Lollipop Radiograph Technique.”  The child is given a lollipop to lick (preferably sugarless). 

After a few licks, the lollipop is taken from the child and a radiograph is attached to the lollipop using an orthodontic rubber band.  The lollipop with the attached film is returned to the child, who is told to lick the lollipop again. 

After a few licks, the child is told to hold the lollipop in his mouth while we take a tooth picture.  The exposure is made.

Procuring Posterior Radiographs Procuring posterior radiographs can be made more

pleasant by associating it with a pleasurable taste….bubble gum. 

Before placing the radiograph in the patient’s mouth apply bubble gum flavored toothpaste to the film.  The child will be more accepting of the radiograph.

Managing gag patients

The easiest is through diversion and positive suggestion.  The operator suggests to the patient the gag reflex can

be reduced by concentrating on something other than the procedure.

The patient’s palate can be sprayed with a topical anesthetic to reduce the sensation of the radiograph on the palate and tongue.

An alternative is the use of nitrous oxide analgesia. 

Bent film radiographic technique

Used in young children who can not tolerate placement of film inside their mouth

Pt bite on the film that has a sharp right angle bend at the top, bent part serves as a self contained bite tab to hold the film in the place.

Instruct the child to softly bite down to avoid cusp marks and distortion on the film

Stick on foam tabs are also available for use 1 to 2 size films are used Straighten the film for processing

Another alternative is to place the radiograph in such a manner to not come in contact with the palate or tongue. 

This is accomplished by either extraoral placement of the film or placing the film between the cheek and the tooth and exposing the film from the opposite jaw. 

The film side of the packet (the solid color side) is facing the buccal surface of the tooth.

The x-ray head is placed at the opposing side, and the cone is positioned under the angle of the ramus on the opposite side. 

As the x-ray beam is traveling a longer distance to the film than in the typical positioning, it is necessary to double the exposure time.

It is imperative that after mounting radiographs are reversed. 

Incorrect mounting and labeling of the reverse radiograph can result in misdiagnosis and treatment of the wrong tooth.

It is difficult to take intraoral radiographs in patients who are intolerable to place films in their mouth. For these patients , Newman and Friedman recommended a new technique of extraoral film placement.

Extraoral periapical radiography : an alternative approach to intraoral periapical radiography: Rahul Kumar, Neha Khambete; Imaging Science in Dentistry; 2011;41 :161-5

Techniques Paralleling Technique Bisecting Angle Technique

Parallelling Technique

Bisecting angle Technique

Difference Bisecting angle technique Parallel technique

Image shape distortion Slight image size distortion

Superimposition of zygomatic process

Control of shadow of zygomatic process

Anatomical relationship altered Correct anatomical relationship

Crown- root ratio is not preserved

Crown-root ratio is preserved

Poor image standardization and reproducibiliy

High image standardization and reproducibility

Paralleling technique has geometric advantage over the bisecting angle technique It has comparatively less distortion. Errors are more likely to occur in bisecting angle technique and leads to more patient exposure due to frequent retakes. However , bisecting angle technique is more appropriate when it comes to patients comfort and more recommended in pediatric population

Comparison of paralleling and bisecting angle technique in endodontic working length radiography;M Fahim Ibrahim,Malik Salman Azif; Pakistan oral & dental Journal;2013; vol 33 ;160-164

Localization Technique

Is a method to locate the position of a tooth or object in the jaws.

Purpose: to depict the B-L relationship or depth of an object.

Two methods 1. Buccal object rule 2. Right angle technique

Buccal object rule Described by clark in 1910 and refined and amplified

by richards in 1952 and 1980.

According to this rule, when a radiograph is performed at a certain angle, the object closer to the radiographic source – the buccal object – is displaced in the radiograph in the same direction as the x-ray beam

Stated more simply as INGLES RULE(MBD)- always shoot from mesial and buccal root will be to the distal..

With an orthoradial projection (A) the two objects appear superimposed.

With an oblique projection (B,C) the two objects cease to be superimposed and easily become recognizable when the angulation of the X-ray machine is known

The buccal object(the one closest to the radiographic source) is displaced in the same direction as the x-ray source

Right angle technique

Given by Miller The periapical radiograph shows impacted canine lying apical to roots of lateral incisor and first

premolar The vertex occlusal view shows that the canine

lies palatal to the roots of the lateral incisor an premlar

A labially positioned mesiodens: A case report ; Robert J Henry, A Charles Post; Pediatric Dentistry ;March 1989- vol 11:59-62

Radiographic techniques commonly used in children

Intraoral Intra oral periapical Bite wing Occlusal

Intraoral Periapical

RadiographIndications: To evaluate the development of the root end and

to study the periapical tissue To detect alterations in the integrity of the

periodontal membrane To evaluate the prognosis of the pulp treatment

by observing the health of the periapical tissues To identify the stage of development of

unerupted teeth To detect developmental abnormalities like

supernumerary, missing or malformed teeth

Posterior maxillary+30 degree

Posterior mandibular- 10 degree

Anterior maxillary+45 degree

Anterior mandibular-15 degree

Bitewing RadiographIndications : Early detection of incipient interproximal caries To understand the configuration of the pulp chamber Record the width of spaces created by premature loss

of deciduous teeth Determine the presence or absence of premolar teeth To determine the relation of a tooth to the occlusal

plane for possibility of tooth Ankylosis Detect levels of periodontal bone at the interdental area Detect secondary caries

Horizontal or vertical

The baseline examinations and intervals to the next bitewing examination in children.

Baseline bitewing examination

Interval to next bitewing examination

At age: Low caries risk High caries risk5 years 3 years 1 year8 or 9 years 3-4 years 1 year12 to 16 years 2 years 1 year16 years 3 years 1 year

Occlusal radiograph The occlusal technique is used to examine

large areas of the upper or lower jaw. In the occlusal technique, size-4 intraoral film

is used. The film is so named because the patient bites, or “occludes,” on the entire film.

In adults, size-4 film is used in the occlusal examination.

In children, size-2 film can be used.

Indications 1.Determine the presence, shape and position of

supernumerary teeth 2.Determine impaction of canines 3.Assess the extent of trauma to teeth and anterior

segments of the arches 4.In case of trismus and trauma, where the patient

cannot open the mouth completely 5.Determine the medial and lateral extent of cysts and

tumors. 6. To localize foreign bodies in jaws and stones in

ducts of salivary glands.7. To obtain information about the location, nature

extent and displacement of fractures of maxilla and mandible

Extraoral techniqueRADIOGRAPHY OF PARANASAL SINUSES1. Standard Occipitomental Projection2. Modified method (30 degree OM)3. Bregma Menton4. PA Water’s

RADIOGRAPHY OF MANDIBLE1. PA Mandible2. Rotated PA Mandible3. Oblique lateral radiography

I. True lateralsII. Oblique lateralsIII. Bimolars (two oblique laterals on one film).

RADIOGRAPHY OF BASE OF SKULL Submento-vertex projection

RADIOGRAPHY OF ZYGOMATIC ARCHES Jughandle view (A modification of submentovertex

view)

RADIOGRAPHY OF TEMPOROMANDIBULAR JOINT1. Transcranial Projection2. Transpharyngeal projection3. Transorbital projection

RADIOGRAPHY OF THE SKULL

1.Lateral Cephalogram2.True lateral (Lateral Skull)3.PA Cephalogram4.PA Skull5.Towne’s projection6.Reverse Towne’s projection

Panaromic Radiograph Most common.

It is a technique for producing a single tomographic image of facial structures that includes both maxillary and mandibular arches and their supporting structures. This is curvilinear variant of conventional tomography and is also used on the principle of the reciprocal movement of an x-ray source and an image receptor around a central point or plane called the image layer in which the object of interest is located

Indications Diagnose missing and supernumerary teeth, Detect gross pathoses, Asses development of the dentition, Estimate the dental age of the patient, Detect bone fractures, traumatic cysts, Detect anomalies, In some patients with disabilities (if the patient can sit in

a chair and hold head in position).

Periapical radiograph allowed the assessment of periapical status of 87% of teeth whereas only 57.6% and 34% of teeth could be appraised using digital panaromic images displayed on monitor and glossy paper respectively.

Teeth are best viewed on periapical radiographs except maxillary second and third molar which are better viewed on OPG

Radiological assessment of periapical status using the periapical index: Comparison of periapical radiography and digital radiography; william et. Al,International Endodontic journal 2007;Vol 40; 6: 433-440.

Interpretation Raised dot toward your eye

(identification dot on tube side) Imagine the x-ray in your mouth by

keeping the identification dot bucally and decide the side.

First mention the area of oral cavity visible on radiograph.

Followed by area of interest . Identify normal anatomic landmarks Knowledge of normal v/s abnormal Attention to all regions on the film

systematically One anatomic structure at a time

Teeth present -Stage of development -Position Condition of crowns -caries - restorations Condition of root -length -resorption -crown:root ratio The apical tissue - integrity of lamina dura -any radiolucency or radiopacity associated with apical area Periodontal tissue - width -level of quality of crestal bone -vertical and horizontal bone loss -furcation involvement Bone – density, trabecular pattern

Describing the lesion 1. size 2. shape 3. location 4. density 5.internal architechture 6.effect on adjacent structure

Measurements were carried out at 52 X-ray units for all types of intraoral examinations performed in clinical routine. Not all X-ray units have pre-set child exposure settings with reduced exposure time or in some cases lower tube voltage. Child examinations are carried out using adult exposure settings at these units, which increases the exposure values by up to 50%. For example, values for periapical examination ranges from 14.4 to 40.9 mGy cm2 for child settings and 20.6 to 48.8 mGy cm2 when the adult settings are included..

Radiation exposure to children in intraoral dental radiology H. K. Looe,A. Pfaffenberger,N. Chofor ; Radiation protection Dosimetry, vol 121, issue 4,461-465

All the three methods of working length determination used in this study were found to be reliable and accurate for use in deciduous molars.

Overall the three techniques show a greater reliability in mandibular molars. Since all techniques are comparable it may be concluded that weighing the advantages and disadvantages of each technique and based on operator’s preference any of the methods can be used for determining the working length in deciduous molars..

Comparison of Root ZX, RVG and Conventional Radiography to determine working length in roots of primary molars : Archana A Thomas, Dr Shobha Tandon

Total of 320 premolars were examined. Of these, 218 (68%) were maxillary premolars and 102 teeth (32%) were mandibular

premolars. All the premolars in the sample had no obvious caries, occlusal malformations, or any restorations.

1.Diagnodent gave similar sensitivity values but lower specificity compared to visual-tactile examination in diagnosing occult dentinal caries.

2. There were no significant differences between conventional or digital radiography in diagnosis of occult dentin caries.

3. Although the diagnosis of occult dentinal caries may be further enhanced by the Diagnodent, a combination of visual-tactile examination and either conventional or digital radiography should suffice in most cases.

Visual-tactile Examination Compared With Conventional Radiography, Digital Radiography, and Diagnodent in the Diagnosis of OcclusalOccult Caries in Extracted Premolars. Michael J. Chong, BDSc, MDSc, W. Kim Seow, BDSc, MDSc,pediatric dentistry 2003, 25-29

Part 2

Digital radiography and radiation protection

RadioVisiography Xeroradiography Subtraction radiography Computed tomography Cone beam computed tomography Tuned aperture computed tomography Magnetic resonance imaging Ultrasound imaging

DIGITAL RADIOGRAPHY It is a method of capturing a radiographic image using

sensor, breaking it into electronic pieces and presenting and storing the image using a sensor.

DIRECT DIGITAL IMAGING- a digital sensor used CCD CMOS

INDIRECT DIGITAL IMAGING-Uses film like photo phsphor plates that are activated using X-rays, then scanned in special devices that read the images from the plate.

Advantages of digital radiography over

conventional radiography

Working time reduced. Chemical processing is avoided. Exposure to radiation is reduced. Cephalometric meaurements and analyses can

be more easily performed with the aid of task dependent software.

Storage and communication are electronic

Radiovisiography Introduced by Mouyen et al in 1989. Radio part sensor- Exchangeable scintillation screens - A fibre optic miniature CCD device Visio part- stores and converts point

by point into one of 256 gray scales. Graphy Part

This system is capable of rapidly displaying a digital radiographic image on a monitor with a 80% radiation dose reduction when compared with conventional radiography

The major components of the RVG system include an X-ray head with an advanced timer, a radiographic sensor connected to a charged coupling device (CCD), a monitor for image display, and a computer with the appropriate software for image storage and manipulation. One of the software’s features allows the operator to vary the contrast.

Merits

The image processing time is very short being about 5 seconds.

Sensors can be easily moved from operatory to operatory , allowing the operators to work with a minimum number of sensor and within a computer network enviornment.

The problems that can be caused through processing faults are eliminated.

It gives opportunity to enhance the images for more precise viewing.

Demerits

They are thicker than films and cables running off the sensor which some patients don’t tolerate well.

The high cost of sensor Difficulty in placing sensor due to its rigidity.

The periapical areas of 16 teeth from 6 human mandibular jaw specimens were randomly examined by 3 observers using conventional radiography with Kodak E-speed film and radiovisiography (with variable contrast and with fixed contrast).

results showed that conventional radiography and radiovisiography (variable contrast) have opposite strengths. Conventional radiography tended to be more accurate in the no lesion condition, whereas radiovisiography using variable contrast was somewhat more accurate in the smallest lesion condition. The accuracy of radiovisiography with fixed contrast was not significantly different from the other two methods..

RadioVisiography in the Detection of Periapical Lesions ,John E. Sullivan, Jr., DDS, MS, Peter M. Di Fiore, Journal of endodontics,2000 , vol 26:65-69

Xeroradiography Records images without film Consist of images receptor plates- selenium

particles Latent image is converted to a positive image-

process called develpment in processing unit.Advantages Reduced radiation dose Image can be produced in 20 seconds Edge enhancement effect. Ability to have both positive and negative prints

Improves visualization of files and canals. Two times more sensitive than conventional D-

speed films.

Disadvantage Exposure time varies according to the

thickness of plate

Xeroradiography and its application to dentistry Thomas Katsanulas, 'Theodor LambrianidisDepartment of Dental Pathology and Therapeutics, Greece:March 22, 1989.

Digital subtaraction radiography This is a method by which structured noise is

reduced in order to increase the detectability in the radiographic pattern.

“Image – enhancement method” – area under focus displayed aaginst a neutral background

Standard radiographs are produced with identical exposure geometry.

Reference/baseline images Follow up image for comparison. If there is change in the radiographic

attenuation between the baseline and follow up examination, this change shows up as a brighter- if there is gain

And as a darker area , when change represents Loss

The strength of digital substraction radiograph is that it cancels out the complex anatomical background against which this change occurs.

Application Useful in detecting progress of

remineralization and demineralization, pattern of dentinal caries, diagnostic of incipient caries.

Assess success of root canal treatment detecting periapical lesion.

90% accurate in detecting as little as 5% mineral loss as compared to conventional radiograph (30-60% loss)

Computed tomography CT has evolved into an

indispensable imaging method in clinical routine.

Non –invasively acquires images

Not biased by superimposition of anatomical structures

CT yields images of much higher contrast compared with conventional.

Tomographic views used to examine various facial structures:

Tomography of sinuses: - more precise evaluation of sinus pathologies -sphenoidal and ethmoidal sinuses are more clearly visualized Tomography of facial bones, to study facial fractures,

extent of orbital blow out fracture Tomography of mandible Tomography of temporomandibular joint

Advatages

Eliminates the super-imposition of images of structures outside the area of interest.

Because of the inherent high-contrast resolution of CT differences between tissues that differ in physical density by less than 1% can be distinguished.

Very small amount difference in the X-ray absorption can be detected

Excellent differentiation between different types of tissues both normal and diseased

Images can be manipulated

Changes in the linear and volumetric measures can be determined by sequential scans

Images can be enhanced by the use of IV contrast media providing additional information

Disadvantages

Since the pixels that form the image represents discrete subdivisions of space, the effect of blurring is much greater than in conventional radiographs

Tissue non-specificity i.e. Have ability to highlight any particular organ/tissue.

Cost concerns..

Metallic objects , such as restoration may produce streak or star artefacts across the CT image.

Need for contrast media for enhanced soft tissue contrast. Inherent risks associated with IV contrast agents

Cone –Beam Computed Tomography

CBCT is an X-ray imaging approach that provides high resolution 3-dimensional images of the jaws and teeth

CBCT shoots out a cone shaped X-ray beam and captures a large volume of area requiring minimal amounts of generated x-rays.

Within 10 seconds, the machine rotates around the head and captures 288 static images.

Advantages

Precise identification and detection of periapical lesions

Detection of mandibular canal Complete 3-D reconstruction and display from any

angle. Patient radiation dose 5 times lower than normal CT Excellent resolution Require only a single scan to capture the entire

object with reduced exposure time. Less expensive than CT

Phantom, armed with lithium fluoride thermoluminescent dosemeters (TLDs) was exposed using a set of four conventional radiographs (orbital view, modified Waters view, orthopantomography, skull posterior–anterior), two different cone beam computed tomography (CBCT) , and multislice computed tomography (CT) modalities

Results: Multislice CT showed the highest exposure values. Exposure levels of the CBCT systems lay between CT and conventional radiography. Dose measurement for the 16-slice CT revealed nearly the same radiation exposure as the 4-slice system when adapted examination protocols were used..

Radiation exposure during midfacial imaging using 4- and 16-slice computed tomography, cone beam computed tomography systems and conventional radiography; D Schulze, M Heiland, H Thurmann, Dentomaxillofacial Radiology (2004) 33, 83–86

Tuned Aperture Computed Tomography (TACT)

Improve accuracy in caries diagnosis because of its 3-D or pseudo 3-D capabilities.

Principle of TACT TACT slices can be produced from an arbitary

number of X-ray projections, each exposed from a different angle.

Using TACT , it is possible to use one X-ray source and move it through several points in space or use several fixed sources to collect multiple X-ray projections which in turn can be processed to produce TACT slices

Generalized TACT projection applied to a simple cylinrical object

TACT useful in

Detection of caries and recurrent caries Periodontal bone loss Periapical lesion localization TMJbone change

Magnetic Resonance Imaging

Principles Magnetism is a dynamic

invisible phenomenon consisting of discrete fields of forces.

Magnetic fields are caused by moving electrical charges or rotating electric charges.

Images are generated from protons of the hydrogen nuclei.

Essentially imaging of the water in the tissue

When images are displayed ; intense signals show as white and weak ones as black nd intermediate shades of gray.

Cortical bone and teeth with low presence of hydrogen are poorly imaged and appear black.

Role of Magnetic Resonance Imaging in dentistry : C D nayak, S S Pagare, scientific Journal 2009 vol3 :67-69

Application Inflammatory and neoplastic lesion of the

nasopharynx, salivary glands, paranasal sinuses.

Diagnosis of internal derangement of TMJ due to its ability to define cartilaginous disk.

Can differentiate between solid and cystic lesions

Perineural spread of a tumour by branches of trigeminal and facial nerve.

Advatages

It offers the best resolution of tissues of low inherent contrast.

No ionizing radiation is involved with MRI. Direct multiplanar image is possible without

reorienting the patient.

Disadvantages

Long imaging time Potential hazards imposed by the presence of

ferromagnetic metals in the vicinity of the imaging magnet.

Ultra Sound Scanning Ultra high frequency sound waves are used. The reflected sound waves are converted to an

electrical signal that is amplified , processed and ultimately displayed on a monitor.

US waves are generated by a quartz or synthetic ceramic crystal when it is exposed to an altering current of 3-10 Mhz as a result of the piezoelectric effect, the crystals distributes US waves oscillating at the same frequency

US image produced – automatic movement of the crystals over the tissue of interest.

As each movement gives one images of this tissue (depending on its plane) and there is a frequency of 30-50 images per seconds, they appear in a screen as moving images.

Useful adjunct to conventional radiography in the management of extensive periapical lesions , as it provides specific information on the size of the lesion

Any exposure, however small it may be , can produce harmful effects

Radiation safety and Protection

Primary biologic effects of radiation:

Deterministic effects

Stochastic effects

Source of the radiation in dental radiology department

Primary beam- radiation originating from focal spot

Secondary radiation-originating from irradiated tissue of patient.

Leakage or stray radiation-radiation from X-ray tube hea positioning

Scattered radiation – from filters and cones, coming from objects other than patient such as walls and furnitures that the primary beam may strike

Means of protection can be divided into: 1. Protection for operator 2. Protection for patient

Protection for the operator

Effort must be made so that operator can leave the room or can take a suitable position behind a barrier

If there is no barrier operator should use lead aprons

The film should never be held by the operator . Ideally film holding devices should be used . If correct retention or placement is still not possible a parent must hold the film in the position.

There should be no use of fluroscent mirrors in the oral cavity

Operator Location The operator of the dental unit must stand atleast six feet from the useful beam or behinda protective barrier. [Stand at an angle of

from 90 to 135 degrees from the central ray. Do NOT stand in the path of the primary x-ray beam.]

If a protective barrier is used, it must have a viewing window to allow the operator to see the patient.

Personnel Radiation Badges

Use of film badge/ TLD badge / pocket dosimeter , for personnel radiation monitoring to avoid accumulate over exposure.

Protection of others No one but the patient should be in the exam

roomduring x-ray exposures. If a person’s presence

isnecessary for the performance of the

examination,that person must be behind a shield or wearing

a lead apron. He/she must not be in line with the primarybeam, and should stand at least six feet from

thex-ray tube if feasible. He/she must also be at

least18 years of age and not be pregnant.

Protection for the Patient

Required Distances

If the dental unit can operate above 50 kVp,the source to skin distance must be at least18 cm [7 inches].

Use of long source to film distance of 40 cm (16 inches), rather than short distance of 20 cm, decreases exposure by 10 to 25 percent, distances between 20 cm to 40 cm are appropriate, but the longer distance are optimal.

Filtration Requirements

The amount of filtration required varies with theoperating range of the x-ray unit. For example:

For 51 to 70 kVp units* 1.5 mm Al [HVL]

Units above 70 kVp 2.1 or more Al

*Note: Settings below 65 kVp are not recommended

because of higher patient exposure.

CollimatorsCollimators limit the size and shape of the useful beam which reaches the patient.The x-ray field must be limited to a circlehaving a diameter of no more than 7 cm [~3 in].

Rectangular collimators are recommended forperiapical radiographs as their use significantlyreduces the area of the patient’s body thatis exposed to radiationis exposed to radiation

Cones

The ADA discourages the use of short, closed,pointed cones because of the increasedscatter radiation close to the face and adjacentareas of the patient’s body.

System Speed

Faster image receptor systems result in

decreased radiation exposure to the patient

Thyroid

The thyroid gland, especially in children, is among the most radiosensitive organs.

Even with optimum techniques, the primarydental beam may pass near or occasionallythrough the gland. A thyroid shield mayreduce the dose to the gland without interfering with obtaining a diagnostic

image.

Lead aprons and shields

Even though the dose from digital radiography is less than convention radiography, patients should be shielded with lead aprons and thyroid shields.

These shields should have at least 0.5 mm of lead

equivalent.

Do not fold or bend aprons. Hang aprons to prevent damage and loss of protective qualities..

The dentist should use every means to reduce unnecessary exposure to their patients and themselves. This philosophy of radiation exposure is often referred to as principle ALARA- A As s LLow ow AAs s RReasonably easonably AAchievablechievable

The exposure to ionizing radiation should be kept as low as reasonable achievable by considering all economic and social factors

References References McDonald RE, Avery DR, Dean JA. Dentistry for th child and adolescent,

8th edn. Mosby, 2004 :117-28

Tandon S. Textbook of pedodontics, 1st edn. Paras Publishing, 2001 :19-28

Koch G. Pediatric dentistry, 1st edn. Munksgaard, 2001 :99-11

Mathewson RJ, Primosch RE. Fundamentals of pediatric dentistry 3rd edn. Quintessence Publishing Co. Inc 1995: 35-55

Damle SG. Textbook of pediatric dentistry, 1st edn. Arya Publishing House, 2000 : 167-71

Oral Radiology- Principles and Interpretataion - White and Pharoah Textbook of Dental and Maxillofacial Radiology - Freny R Karjodkar Essentials of Dental Radiography and Radiology - Eric Whaites Bramanet CM, Berbert A. A critical evaluation of some methods

of determining tooth length. Oral Surg 1974; 37: 463. Forsberg J. Radiographic reproduction of endodontic “working

length” comparing the paralleling and the bisecting-angle techniques.Oral Surg Oral Med Oral Pathol 1987; 64(3): 353-60.

• Langland OF, Langlais RP, Preece JW. Principles of dental imaging. In: Langland OF, Langlais RP, Preece JW. Intraoral radiographic techniques. 2nd ed. Philadelphia: Lippincott Williams & Wilkins, 2002: 91-97.• •Jhon PR. Essentials of Dental Radiology. In: Jhon PR. Intraoral radiographic techniques and indications of intraoral radiographs.1st ed. New Delhi: Jaypee Brothers, 1999: 75-81.

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