Orthodontic Radiograph guidelines

By Issacson, 2007

Damaging effects on human tissue are currently divided into three major categories:

1. Somatic deterministic (certainty) effects when the threshold dose reached

a. Direct effects: abnormal mitosis; degeneration and death of cells

b. Indirect effects: change in tissue due to damage to blood supply (endarteritis)

c. Constitutional effects: malaise, nausea, vomiting, decrease blood pressure,

peripheral vascular failure (radiation shock)

2. Somatic stochastic (random) effects: Neoplastic change: e.g. skin, bone sarcomas,

leukaemia

3. Genetic stochastic (random) effects, effect shown in offspring of recipient

NB:

Unnecessary radiation from diagnostic R/Gs causes 100-250 UK cancer fatalities.

25% of all X-ray examinations are dental

The main effect of x-ray is by ionization. When an electron passes through a cell, it releases its

energy along its path (called a track) by interacting with the electrons of nearby molecules. The

released energy is absorbed by atoms near the track, resulting in either excitation (a shift in the

orbit of an electron to a higher energy level) or ionization (release of an electron from the atom).

There are currently two sets of legislation in the UK, based on European directives,

following international community of radiation protection (ICRP) recommendation is,

namely:

1. The Ionising Radiations Regulations 1999 (IRR) which are primarily concerned with the

safety of worker and the general public.

2. The Ionising Radiation (Medical Exposure) Regulations 2000 (IRMER) which are

concerned with the protection of patients.

Essential legal requirements of IRR 1999

1. The Health and Safety Executive must be notified the routine use of dental X-ray

equipment.

2. A prior risk assessment must be undertaken before radiography commences and be

subject to regular review.

3. X-ray equipment, particularly all safety features, must be maintained.

4. A `controlled area' should be designated around each piece of X-ray equipment.

5. Local Rules are required.

6. A Radiation Protection Adviser (RPA) and a Radiation Protection Supervisor (RPS) must

be appointed and consulted.

7. All employees have and should be aware of their specific duties and responsibilities.

8. Information, instruction and training must be provided for all staff.

9. A quality assurance programme is required.

10. There is an over-riding requirement to restrict radiation doses to staff and other persons

as low as reasonably practicable (ALARP).

The IRMER includes three important measures:

A. Justification

B. Optimization (keeping the dose as low as possible ALARP with high benefit to the pt.by

increase KV, digital sensitive film, fast speed film, collimator , film holder, staff training,

quality assurance)

Essential legal requirements of IRMER 2000

New positions of responsibility are defined:

1. The Employer (Legal Person)

2. The Referrer

3. The Practitioner

4. The Operator

IRMER Employers

They are responsible for providing

The overall safety and radiation protection framework

Ensuring that staff and procedures conform with the regulations

Providing 'Written Procedures' for all medical exposures.

IRMER Referrers

They are responsible for supplying the IRMER Practitioner with sufficient information to

justify an appropriate exposure.

IRMER Practitioners

They are clinically responsible for justify all medical exposure. Justification must be based on

consideration of:

1. The aim of the exposure

2. The total potential benefit to the patient

3. The risk to the patient

4. The efficacy, benefits and risks of alternative techniques.

In private clinic, all general dental practitioners and specialist orthodontists in practice

are IRMER Practitioners and are therefore required by law to justify every radiograph that

they take.

In hospitals, orthodontists are IRMER Referrers as they refer their patients to an X-ray

Department to be imaged. As such they are responsible for supplying sufficient clinical

information so that the IRMER Practitioner within the X-ray Department can justify the

exposures.

IRMER Operators

They are responsible for conducting any practical aspect of a medical exposure including

exposing the radiograph or processing the film. IRMER Operators and IRMER Practitioners

must have received adequate training and education.

Radiation dose delivered by diagnostic imaging and the magnitude of the risks involved

Radiation dose is complicated by the fact that several different measurements of 'dose' exist.

The main terms are:

1. Radiation absorbed dose

2. Equivalent dose

3. Effective dose.

RADIATION ABSORBED DOSE (D)

This is a measurement of the amount of energy absorbed from the X-ray beam per unit mass

of tissue. It is measured in Joules/kg. The Standard International (SI) unit is the Gray (Gy).

EQUIVALENT DOSE (H)

This is a measurement of radiation dose that takes into account the radiobiological

effectiveness and damage caused by different types of radiation.

Each type of radiation is allocated a different radiation weighting factor (WR).

X-rays and gamma rays have a weighting factor of 1, while the more damaging protons

and alpha particles have a weighting factor of 2 and 20 respectively.

The equivalent dose is calculated by multiplying the radiation absorbed dose (the amount

of energy absorbed by the tissue) by the radiation weighting factor (RW) for the type of

radiation being used.

The Standard International unit is the Sievert (Sy).

EFFECTIVE DOSE (E)

This is a measurement which allows doses from different parts of the body to be compared, by

converting all doses into an equivalent whole body dose.

The most radiosensitive organs and tissues in the body are given tissue weighting factors.

When an exposure involves one of these tissues the equivalent dose is multiplied by the

appropriate tissue weighting factor (TW) to give an effective dose.

The Standard International unit is same as above the Sievert (Sy).

Effective doses and risks from exposure to x-rays in orthodontic practice

NB:

The annual global per capita effective dose due to natural background radiation sources

alone is estimated to be about 2400 mSv at sea level, and may be of wide range between 1000

and 3000 mSv. Consequently, the natural background radiation is estimated to be about 8

mSv per day.

In case of i-cat there is 5msv for each 1cm if the voxel size is 0.4mm. keeping in mind

that we need exposure area of 4-5cm for each jaw and for the whole skull we need 22cm

(Chung 2013)

Radiographs that used in IO

1. PA is size is large 31*41 or small 22*35

2. Occlusal size 57*76, for vertex occlusal we need to use intensifying screen to increase

radiographical exposure and the beam should be perpendicular to OP at hairline level

3. For oblique occlusal in the UA the angle is 65-70 while in the lower is -45 degree

4. Lateral oblique size 130*180 and we can use normal dental x-ray machine after removing

the rectangular collimator

5. OPT , size 130*240. Its problems are artefact, ghost image from other side of the mouth

and cervical spine, air shadow may simulate caries, magnification,

6. Cephaolgram, siz 180*240,

Practical and physical methods available for reducing or limiting the dose to patients

1. The equipment

2. Radiological technique

3. Clinical judgement in justification and interpretation.

4. Quality Assurance

1. EQUIPMENT

X-ray units should:

Operate at high kV (60-70kV for intra-oral equipment)

Incorporate adequate aluminium filtration

Incorporate appropriate beam collimation

Be both critically examined and acceptance tested

Incorporate warning signals.

Conventional image receptors should:

Be the fastest available film speed — typically F speed

Involve rare-earth intensifying screens for extra-oral radiography.

Digital image receptors should:

Be used with exposures that have been optimised in consultation with the Radiation

Protection Advisor

2. Radiographic techniques

1. Intra-oral periapicals and bitewings should:

accurate film positioning

film holders

Be taken using rectangular collimation

Be chemically or digitally processed correctly.

2. Intra-oral upper occlusal radiographs should:

Be taken using rectangular collimation

Include the use of a thyroid shield or collar if the thyroid gland lies in the primary beam.

3. Panoramic radiographs should:

Ensure accurate patient positioning assisted by light beam markers

Allow field limitation techniques and appropriate collimation of panoramic images such

as 'dentition only', which results in a 50% dose reduction.

4. Lateral cephalometric radiographs should.

Ensure accurate patient positioning assisted by light beam markers

Include triangular collimation, facilitated by a light beam diaphragm, so as not to

irradiate the whole of the cranium and neck

Include an aluminium wedge filter, ideally at the X-ray tube head, to facilitate the

imaging of the soft tissue

5. Cone beam imaging should:

Ensure accurate patient position assisted by light beam markers

Use the smallest field of view compatible with the clinical situation.

The indication according to Issacsson 2007

I. For diagnosis and TP

a. Other than Cephalometric

For a patient under 9 years

For patient above 9 years

b. Cephalometric

Below 10 years

Age 10-18 years

age above 18 years

II. Monitoring of treatment

Unerupted teeth

Iatrogenic factors

Treatment progress

III. End of active tooth movement

IV. Growth and post-treatment changes

In details

1. For diagnosis and TP

c. Other than ceph

1. For a patient under 9 years

If incisors or molar are overdue and there is a clinical triggers to have a problem

If the incisors are rotated or crowded severely then consider x-ray

If the OJ increases or reversed severely then consider x-ray

Delayed eruption

2. For patient above 9 years

If the incisors are rotated or crowded severely then take x-ray

If the OJ increases or reversed severely then consider x-ray

Submerged teeth then take x-ray

Canine not palpable then take x-ray

Delayed eruption

d. Cephalometric

1. Below 10 years

Only if the condition is sever class II or class III which need early treatment

2. Age 10-18 years

The condition should be:

class II or class III, Bimaxillary

and

Treatment for both arch

and

will start soon

and

functional or U and L FA for both arches or extraction with change in the incisor position

3. age above 18 years

CL2 D1 , Cl2D2 , Cl3 , Bimax and

Treatment for both arch and

will start soon and

surgery or U & L FA

or extraction with change in the incisor position

History of previous orthodontic treatment may need investigation, but localised intra-oral

radiographs may be sufficient

1. Only 4-20 % of treatment plan can be changed after radiograph examination

compared with no radiograph taken (Brukes 1999, Whaite 1992).

2. Devereux & Cunningham 2011 showed that the use of ceph will not change the TP

3. Study model: Han and Vig 1991showed that in class II cases, the study model alone

in a majority of cases (55%), provided adequate information for treatment

planning, and incremental addition of information from other types of diagnostic

records made small differences.

4. Cephalometric: Nijkamp 2008, that cephalometrics are not required for orthodontic

treatment planning, as they did not influence treatment decisions for patient with

class II malocclusion.

2. MONITORING OF TREATMENT

A. Unerupted teeth

1. It is important to ensure that the repeat images are taken in an identical position to the

original to ensure a reliable comparison.

2. Intra-oral views (periapical or occlusal), should be considered

3. A panoramic radiograph (with appropriate field limitation) can be used to monitor the

changes in position of several unerupted teeth

B. latrogenic factors

1. If there is evidence of excessive tooth mobility during treatment.

2. where there is abnormal delay of tooth movement

3. an indication of apical disease,

4. a risk of resorptions E.g Root apices, which are blunt or pipette-shaped.

C. Treatment progress

1. Where orthodontic treatment precedes implant or other restorative procedures, localised

periapical radiographs to show root angulations may be required

2. End of functional appliance and before starting FA to determine incisor position and the

need for extraction, anchorage and treatment mechanics.

3. Few months before appliance removal will allow the orthodontist to carry out any

necessary adjustments to achieve the treatment targets.

3. End of active tooth movement

1. Should be assessed carefully for each patient and is unlikely to be indicated except for

patients with severe malocclusions.

2. It is used as baseline to check future changes.

4. Growth and post-treatment changes

1. It is difficult to define and has to be assessed for each patient.

2. They may be indicated in patients where stability is uncertain either as a result of a

specific type of treatment or because unfavourable growth is anticipated.

There are no orthodontic indications for the following:

1. Radiographs before a clinical examination

2. A set of routine radiographs for all orthodontic patients

3. Cone beam CT for all orthodontic patients

4. Prediction of facial growth

5. Hand and wrist

6. Temporomandibular joint (myofascial) pain dysfunction

7. Prospective radiographs for medico-legal reasons

8. Research purposes, professional examinations or for clinical presentation unless

approved.

Radiography equipment

a. DENTAL X-RAY EQUIPMENT:

The operating range should be in the range of 60-70kV.

1.5-2.5mm almunium filter

Should ideally include rectangular collimation (40 x 50mm), but if circular beams are

used they should not exceed 60mm in diameter.

The focus-to-skin distance (fsd) should be 20 cm

Uses

I. Periapical views:

Assess root morphology

Assess root resorption

Assess apical disease

In combination with a standard occlusal or second periapical to localise unerupted teeth

by parallax

II. Upper standard occlusal radiograph:

Confirm the presence of unerupted teeth

Parallax localisation either with a panoramic or periapical

To identify supernumerary teeth

Identification of developmental anomalies

III. Bitewings

Identification and assessment of severity of caries

Demonstration of periodontal bone levels

Assessment of existing restorations

b. PANORAMIC UNITS:

tube potential settings, preferably from 60 to 90 kV.

Beam height (normally 125mm or 150mm).

Equipment needs to be provided with patient positioning aids, incorporating light beam

markers.

Uses

Identification of the developing dentition

Confirmation of the presence/absence of teeth

Alveolar bone level

Root conditions

Caries (general idea)

Periapical and bone pathology

Should not be used for TMJ diagnosis

c. CEPHALOMETRIC EQUIPMENT:

The equipment must be able to ensure the precise alignment of the X-ray beam, image

receptor and the patient.

The focus to film distance should be in the range of 1.5-1.8m to minimise magnification

effects

Uses

1. diagnosis and treatment planning

a. detection and localization of unerupted teeth

b. allows assessment of AP

c. vertical Sk pattern,

d. incisor positions and angulations (e.g lip trap behind incisors, lopwer lip line in cl2d2,

upper centroid to LI, ,

e. To assess the reliability of functional appliance

f. soft tissue profile

g. Orthognathic surgery planning and VTO

h. Baseline to monitor treatment

i. Airway assessment

2. During active treatment (Broadbent, 1937)

to determine the final treatment plan and if exo is selected or not

Pre-space closure to check L1 position and anchorage

In orthognathic to determine the goals are met

Postfunctional to assess skeletal and dental relationship

3. end of treatment

To check arch relationship

To check that target met

Plan retention

Baseline to monitor changes in postretention phase

4. During retention to assess relapse and unfavourable growth specially in orthognathic

5. To assess and monitor growth by using series of radiograph or compare it to norms

6. Research purposes (Bjork, 1954)

d. NEW IMAGING TECHNIQUES—CONE BEAM COMPUTED TOMOGRAPHY

(CBCT)

Low dose cone beam CT technology has recently been developed specifically for use in the

dental and maxillofacial regions.

Equipment and theory

1. The equipment employs a cone-shaped X-ray beam rather than the flat fan shaped beam

used in conventional CT. and a special detector — typically a flat panel (either amorphous

silicon or CMOS).

2. The equipment orbits around the patient, taking approximately 10-40 seconds

3. The patient must remain absolutely stationary throughout the exposure.

4. Having obtained the data, then the computer collates the information, in about 2-5

minutes, into cubes or isotropic voxels (volume pixel, the smallest distinguishable box-shaped

part of a three-dimensional image.)(typically 0.2mm x 0.2mm x 0.2mm)— referred to as the

primary reconstruction (one scan contains over 100 million voxels)

5. Computer software allows the operator to select whichever voxels are required in the

orthogonal sagittal, coronal or axial planes — referred to as secondary (or multiplanar)

reconstruction

6. also allows the creation of panoramic and lateral cephalometric style images as well as

cross-sectional or transaxial images of any part of the jaw, the Ceph or OPT which is

produced from the CBCT are reliable with no magnification if we compare it to 2 D ceph.

7. The equipment typically employs a high kV (85-120 kV) pulsed beam to minimize soft

tissue absorption. For example, during a scan lasting 20 seconds, the patient is only exposed

to ionizing radiation for about 3.5 seconds.

8. The overall effective dose has been estimated to be in the order of 50-500 MSv,

9. One exposure is equivalent to approximately 2-8 conventional panoramic radiographs.

Uses of CBCT

1. No formal selection criteria are established. According to BOS guidelines (Issacson

2008) and the eurpean commission (SEDENTEX 2011) the use of CBCT should be indicated

only if the plain conventional view didn't show enough information like

A. Impacted teeth (Botticelli 2011 showed that 3D will help the surgeon to determine the

best approach to the impacted tooth and will help the orthodontist to determine the mechanics

and force direction,

B. Supernumerary teeth (Sarah Merit 2013),

C. Root resorption, Dobbyn and Chung 2013 found that root resorption was present in 39%

of cases where the resorption was cited as a reason for CBCT request. (this means that plain

radiograph miss around 39% of resorption)

D. Orthognathic

E. CLP

2. Orthodontists are advised to use CBCT with caution and always ask themselves whether

the question for which the imaging is requested could be answered adequately by

conventional radiography. Routine use of CBCT, as suggested by Chaushu cannot be justified

3. Cleft palate patients

4. Orthognathic surgery planning. 3D superimpositions, assessment of treatment outcome,

and growth change evaluation in three dimensions can be performed. Surgical outcomes can

be evaluated, and this can be of great value for the orthodontist and the patient. Lastly, soft

tissue change can be visualized and evaluated in the short- and long-term in cases of

orthognathic surgery.

5. Planning for TAD placement (Noar 2013)

6. Assessment of RME (Khambay 2011)

7. Airway analysis (Benington 2010)

8. In case of transplantation, it might be used to prepare a template in the receiver site.

9. Assessment of dilacerations or developmental anomalies like the number of roots or

dense evagnination.

10. Assessment of root fractures

11. Implant (bone height, width, quality, relation with adjacent structures, Implant born

frameworks and abutments can also now be produced using CAD/CAM technology)

12. Endo-perio lesion (no of roots, size of lesion, association with other structures)

Disadvantages

1. High cost

2. High radiation dose

It is correct that a certain CBCT effective dose of 50 mSv is equivalent in magnitude to 6

or 7 days of background radiation; however, the effect is entirely different because the acute

nature of CBCT exposure of few a seconds is unlike the very low, continuous, and chronic

exposure of background radiation. Radiation heresies concept suggests that very low doses of

continuous and chronic ionizing radiation that are equivalent to natural background levels are,

in fact, beneficial. This is because they stimulate the activation of repair mechanisms that

protect against the disease process

Some claims that the radiation of CBCT is equal to full mouth bitewing but in growing

orthodontic patient we do not need full mouth bitewing since pd is not compromised except in

very limited number of cases.

3. Low quality of the view unless high resolution is used which cause higher dose.

4. No evidences that it improve outcome of treatment. A study in Cardiff in 2013 showed

that the incidental finding of the CBCT that changed the treatment plan is only less than 1%

(Sheela Roger 2013).

5. Need experience interpretation since the examination of the whole radiated area is

responsibility.

6. There is an error in Cephalometric linear measurement using the cephalometric

constructed from CBCT. Shaw and McIntyre 2013 validate the use of 3D cephalometric in the

comparison to 2 D cephalometric. They mentioned that conventional cephalometric is similar

to cephalometric developed by the CBCT.

e. OTHER VIEWS

I. Posteroanterior views of the skull may be of use in those patients who present with

facial asymmetry,

II. The vertex occlusal view which has few, if any, indications, is no longer recommended

and is only of historical interest.

III. Hand or wrist radiographs

In orthodontics it is no longer considered necessary to take hand or wrist radiographs to

assess skeletal maturation.

The method reported by Bacetti using stages of calcification of the cervical vertebrae has

been shown to substitute for hand wrist radiographs.

IV. IMAGING OF THE TEMPOROMANDIBULAR JOINT

CT scan

CBCT

MRI for disc problem

It has been argued that the absence of pre-treatment radiographs could be considered

negligent when TMJ pain dysfunction symptoms develop during or after orthodontic

treatment. As already stated, conventional radiographs are no longer recommended for

investigating TMJ pain dysfunction so the need to have any radiographs taken in advance of

treatment in order to avoid possible later claims of negligence cannot be justified.

Image receptors — film and digital

1. Radiographic film

a. Direct action or packet film (intra-oral).

b. Indirect action film used in conjunction with rare-earth intensifying screens in a cassette

(extra-oral).

2. Digital receptors

a. Solid-state sensors (SSS) (which connected to cable to PC).

b. Photostimulable phosphor plates (PPP) following exposure the plates are read by a laser

scanning device before the image appears on the computer monitor.

Benefits

1. Image storage and transmission

2. Processing

3. Reduced radiation exposure of upto 30-50% in some systems

4. Environmentally friendly: no processing chemicals, sensors and plates can be re-used

thousands of times, so long as not scratched or damaged

5. image enhancement is possible to improve diagnostic quality of digital images

Image enhancement consists of:

Contrast improvement

Smoothing

Edge enhancement

Disadvantages of digital imaging:

Cost

Bulky

Cross infection control

Medico legal concerns from manipulating images: manufacturers of software

programmes have installed 'audit trails' which can track down and recover original images

Reduced resolution