Paediatric Radiology

Dr. Regina Revuelta Perez
Authored by:
Dr. Regina Revuelta Perez

INTRODUCTION

Exposure to x-radiation is often of major concern to parents who may question you with regards to the necessity and safety of taking dental radiographs. It is important that you are aware of radiation hygiene and develop the ability to relate your clinical findings to the minimum number of radiographs required for an optimal treatment plan for each patient. You must individualize the number of radiographs necessary for each patient.

Your goal should be to exercise discretion in exposing patients to x-radiation while at the same time taking sufficient radiographs to ensure the patient receives optimal treatment.

Generally the operator can expect excellent cooperation from the three to three-and-a half year old child when attempting to take a radiographic survey. Below the age of three years, the operator and child may experience great frustration in taking radiographs and the future behaviour of the child in the dental environment may be impaired. In the very young child it is usually preferable to limit radiographs to assist in the assessment of infected teeth or trauma where it may be necessary to enlist the assistance of the parent in holding the child's head and film in position.

Techniques in Patient Management

The most successful approach to gain cooperation with the young child is to TELL them what you are going to do, SHOW them how it is done, and then proceed to DO it. Avoid talking down to the child, and use words that they can understand. The use of ANALOGIES is always helpful and in radiography the concept of photography is most apt. Thus, the x-ray machine becomes the camera and the film (or sensor in the case of digital radiography) a piece of card to bite on so that the camera can be pointed in the right direction. Allow the child to handle a film and bend it so that he or she is aware of what is being placed in their mouth.

Small children have a short attention span so that an efficient, time saving approach to exposing x-ray films is an advantage. This may be achieved in the following ways:

  1. Select adequate film size: if the first permanent molars have not erupted, bitewing and posterior periapical views are taken with size 0 film. If the first permanent molars have erupted, use standard periapical film. This is only a rule of thumb and discretion should be used by the operator as mouth size varies. Standard periapical film should be used for all anterior views. Always remember for what purposes the particular view is being taken and position the film and x-ray head accordingly.
  2. Select adequate film speed. Currently, the use of F – speed films  reduces radiation exposure by around 60% compared to D-speed films, and by around 20- 25% compared to E-speed films.
  3. Preset exposure factors.
  4. Patient protection: ALWAYS PROTECT THE CHILD'S GONADAL AND THYROID REGIONS WITH A LEAD APRON AND COLLAR. If the parent is to be in the room with the patient to assist in positioning, place a lead apron and collar on them as well.
  5. Film placement: the accommodation of x-ray film in the mouth is at best an uncomfortable experience, so that the less time the film is left in the mouth the better for patient comfort.
  6. Position the child's head.
  7. Position x-ray head.
  8. Expose the film.

Dental radiographs are a necessary tool when performing an adequate diagnosis and therefore an adjuvant in treatment planning. The number of radiographs taken will depend not only on the patient’s chronological age, but also the dental age. At no point should radiographs be prescribed as a screening method only. The amount of radiographs required must be INDIVIDUALIZED and based on several factors which include dental age, the development of occlusion on the patient, assessment of exfoliation of primary teeth or eruption of permanent teeth, caries risk, number of restorations present, as well as incidence or presence of dental pathologies/anomalies.

RADIOGRAPHIC SURVEY FOR PEDIATRIC PATIENTS

Primary Dentition:
(Before the eruption of the first permanent molars.)

  •  X-ray films required
    • 2 standard periapicals  [for views (a) and (b) listed below]
    • 6 size 0 films
  • Views
  1. Maxillary anterior occlusal
  2. Mandibular anterior occlusal
  3. Right and left posterior maxillary periapicals
  4. Right and left posterior mandibular periapicals
  5. Right and left bitewin
  • Mixed Dentition
    • X-ray films required
    • 8 or 10 standard periapicals (where possible) depending on the views required
  • Views

8 film series

  • Maxillary anterior occlusal
  • Mandibular anterior occlusal
  • Right and left posterior maxillary periapicals
  • Right and left posterior mandibular periapicals
  • Right and left bitewings

10 film series: indicated if maxillary permanent lateral incisors have erupted

  • Periapical of maxillary central incisors
  • Right and left periapical of maxillary cuspids
  • Mandibular anterior occlusal
  • Right and left posterior maxillary periapicals
  • Right and left posterior mandibular periapicals
  • Right and left bitewings

Orientation of the Film

The plain surface of the periapical film should face the x-ray tube.

  • The Snap-a-Ray (RINN Holder)
  1. The Snap-a-Ray holder allows the film to be held firmly in the mouth by using the patient's biting pressure.
  2. The broad side of the Snap-a-Ray holder should project towards the cheek and be placed between the occlusal surfaces.
  3. The handle of the Snap-a-Ray holder allows a more accurate orientation of the x-ray tube with respect to the film.
  • Head Position
  1. The patient's head should be orientated in the Frankfurt Horizontal position, (a line joining the external auditory meatus and the inferior border of the orbit is parallel to the floor).
  2. With the head in this position the operator can accurately use the angles to be described for the x-ray tube, based on the principle of the bisecting angle technique.
  3. The "Principle of the Bisecting Angle Technique" states, "the x-ray tube should be at right angles to the bisector of the angle the film makes with the long axis of the tooth root."

MAXILLARY ANTERIOR OCCLUSAL VIEW

  1. Head in Frankfort Horizontal position
  2. Place standard size periapical film between the teeth with:
    1. Long axis of film directed towards the corners of the mouth.
    2. Anterior edge of film is to be placed 1/8 of an inch anterior to the labial surface of the upper incisors.
    3. Film is placed equidistant on either side of maxillary dental arch.
  3. Instruct child to close the teeth on the film with a gentle, but firm pressure.
  4. Direct central ray at a vertical angulation of +60o to the horizontal with the central ray directed through the tip of the nose.

MANDIBULAR ANTERIOR OCCLUSAL VIEW

  1. Tilt the child's head gently backwards so that the chin is elevated.
  2. Place the standard size film between the teeth as described for the maxillary anterior occlusal view (though the film will be turned over so that the correct side faces the cone).
  3. Instruct the child to close gently on to the film.
  4. Place the x-ray cone so that its lower edge sits in the angle formed at the junction of the external lip and chin with the underside of the cone resting against the chin protuberance; this provides a guide for  the vertical angulation of the cone.
  5. Draw the cone backwards and downwards, without altering the vertical angulation, so that the central ray passes through the centre of the mandibular symphysis.

MAXILLARY POSTERIOR PERIAPICAL VIEW

  1. Head in Frankfort Horizontal position.
  2. Place film horizontally in Snap-a-Ray holder and position film firmly in the palate; ask the patient to close (jiggling of the film during placement may elicit the gag reflex.)
  3. Direct the central ray 3/4 of an inch in front of the outer canthus of the eye and 3/4 of an inch below it at an angle of +40o.
  4. The central ray should make a right angle with the handle of the Snap-a-Ray holder in the horizontal plane.

MANDIBULAR POSTERIOR PERIAPICAL VIEW

  1. Head in the Frankfort Horizontal position.
  2. Place film in Snap-a-Ray holder and gently position the lower edge of the film against the lingual surfaces of the mandibular teeth in the buccal segment.
  3. Instruct the patient to close; as the patient closes, the muscles of the lingual sulcus relax allowing the film to be accommodated in a more apical position. The film may be gently rolled, not bent, over the operator's forefinger to allow more comfortable accommodation in the mandibular cuspid region.
  4. Set the central ray at 0o with the tip of the cone gently touching the cheek just above the lower border of the mandible.
  5. The central ray should make a right angle with the handle of the Snap-a-Ray holder in the horizontal plane.

BITEWING VIEWS

  1. Attach removable paper bitewing tab at the centre of the film. Choose a film size adequate to patient’s mouth. Film should be placed in a horizontal position.
  2. Carefully curl the corners of the film to avoid impingement on the gingivae if the mouth is very small. Do not make acute bends in the film.
  3. Grip film by tab and position packet lingual to the posterior mandibular teeth.
  4. The tip of the index finger should support the film in the vertical position and guide it into the palatal vault as the child is instructed to close gently.
  5. Withdraw the finger as the top of the film slides palatal to the maxillary teeth.
  6. Guide chin into the most retruded position.
  7. Aim central ray towards the centre of the film and occlusal surfaces of the teeth at +10o to the horizontal and right angles to the film with the tip of the cone gently in contact with the cheek.

MAXILLARY CENTRAL INCISOR PERIAPICAL VIEW

  1. Head in the Frankfort Horizontal position.
  2. Place a standard size film in the mouth, with a vertical orientation, against the palatal surfaces of the incisors with the inferior edge of the film extending 1/8 inch below the incisal edges of the anterior teeth (the film may be held in the mouth by the patient's thumb or a film holder occluded on by the teeth.)
  3. Direct the central ray at a vertical angulation of +60o to the horizontal with the central ray directed towards the centre of the film, through the tip of the nose.

MAXILLARY CUSPID VIEW

  1. Head in the Frankfort Horizontal position.
  2. Place a standard size film in the mouth with a vertical orientation, against the palatal surfaces of the cuspid tooth with the inferior edge of the film extending 1/8 inch below the cusp tip of the canine (the film may be held in the mouth by the patient's thumb or by a film holder.)
  3. Direct the central ray at +60o so that it passes just lateral to the ala of the nose on the side that is being imaged.

PANORAMIC RADIOGRAPHY

The panoramic radiograph has recently become very popular amongst practising dentists because all of the patient’s teeth can be shown on one radiograph. This makes the view extremely useful if a practitioner wishes to assess the presence or absence of unerupted permanent teeth or the extent of pathology. However, there are many distortions and superimpositions that occur when a panoramic radiograph is taken, particularly in the maxillary incisor region. There is also a lack of fine detail at contact points and in the appearance of the lamina dura and cancellous bone. Therefore, the limitations of this film type need to be recognised and supplemental images may be required for accurate diagnosis.

DIGITAL DENTAL RADIOLOGY IN CHILDREN

In digital radiography, instead of the silver halide grain of film, the image is constructed using pixels or small light sensitive elements. These pixels can be a range of shades of grey depending on the exposure, and are arranged in grids and rows on the sensor, unlike the random distribution of the crystals in standard film. However, unlike film the sensors are only the radiation detector and the image is displayed on a monitor.

The signal that is produced by the sensor is an analogue signal, i.e. a voltage that varies as a function of time. The sensor is connected to the computer and the signal is sampled at regular intervals. The output of each pixel is quantified and converted to numbers by a frame grabber within the computer. The range of numbers is normally from 0 to 256 with 0 representing black, 256 representing white and all others are shades of grey.

The number of grey levels relates to contrast resolution and the size of the pixels is related to spatial resolution. Together these determine the overall resolution (i.e. the ability to distinguish between small objects close together) of the image. Resolution can also be expressed in line pairs per millimetre. Most conventional E speed films have a resolution of 20 LP/mm whereas with digital images the resolution ranges from 7–10 LP/mm. The reduced resolution should not interfere with clinical diagnosis.

Advantages of digital imaging

There are several advantages to digital images, which include:

  • Dose reduction. Dose reductions of up to 90 per cent compared to E-speed intra-oral film have been reported by some authors in the diagnosis of caries. Although some researchers do claim dose reductions compared with conventional extra-oral film, in practice the background noise raises to unacceptable levels. It is now accepted that there is no appreciable reduction compared with films used in conjunction with rare earth intensifying screens.
  • Image manipulation. This is perhaps the greatest advantage of digital imaging over conventional film. It involves selecting the information of greatest diagnostic value and suppressing the rest. Manufacturers provide software programmes with many different processing tools, however some are more useful than others and these include: contrast enhancement, measurements, 3-D reconstruction, filtration, image displayed immediately without any processing (time-saving), easier storage, possibility of teleradiology, environmentally friendly.

Disadvantages of digital imaging

Despite all the advantages, there are also some disadvantages that include: cost of equipment and maintenance, cross-infection control, medico-legal concerns since images can be altered.

One of the biggest disadvantages in the case of paediatric patients is the size and bulkiness of some digital sensors. In some instances it can make the technique challenging, particularly in very young patients (smaller mouths) or patients with limited opening. In this situations, behaviour management techniques such as Tell-Show-Do or verbal/visual distraction can be helpful.

Remember the hazards of radiation are cumulative. You have a long practising life ahead of you and, therefore, YOU MUST NEVER BE IN THE DIRECT PATH OF AN X-RAY BEAM.

Always remember that a radiographic survey never takes the place of a CLINICAL ORAL EXAMINATION, it only COMPLIMENTS it by confirming , negating, or adding to your original clinical examination.

 

References: 

Pediatric Dentistry Manual, Univeristy of Toronto, 2010

J. Brennan, An Introduction to Digital Radiography in Dentistry, Journal of Orthodontics, Vol. 29, No. 1, 66-69, March 2002

Article Reviewed By

Dr. Susanne Perschbacher & Dr. Michael Sigal