Dental radiography can give rise to a significant dose of radiation
to the bone marrow in the skull and cervical spine, the oral mucosa,
the thyroid and the eye as well as to any part of any person exposed
to the primary beam.
The utilisation of badly adjusted equipment, and/or poor technique
(e.g. holding an X-ray film in the hand) may unnecessarily increase
the incidence of stochastic effects and could in some extreme cases
give rise to a deterministic effect.
Genetic Effects
Owing to the rapid growth in the use of dental X-rays and the increasing
number of persons undergoing dental examinations the genetic effects
of ionising radiation from dental radiography may also be of concern.
It is important to remember that the number and variety of radiation
sources contributing to the total exposure of the public is increasing.
No user or group of users of ionising radiation has the right to defend
its position simply on the basis that, in comparison with others, it
is producing only a small population exposure. The largest single contributor
of man-made radiation exposure to the population is medical and dental
diagnostic radiology. It is assumed that, for the purpose of establishing
accurate standards of protection from ionising radiation, any exposure,
no matter how small, carries some risk. The magnitude of this risk is
also assumed to be proportional to the magnitude of the does received.
Radiographic procedures which minimise the dose to patients and at the
same time yield the required diagnostic information must, therefore,
be utilised. All users of radiation must take every practical step to
minimise the exposures for which they are responsible.
2. Statutory Controls.
The principal legal documents which apply to the control of sources of
ionising radiation in Ireland are:
- The Radiological Protection Act, 1991 (No. 9 of 1991) establishing
the Radiological Protection Institute of Ireland (RPII)
- European Communities (Medical Ionising Radiation) Regulations, 1988
(S.I. No. 189 of 1988) which implements the EC Directive on the protection
of the patient undergoing medical examination or treatment (84/466/Euratom).
These regulations refer to the need for specialised training of all
doctors/dentists who use or direct the use of ionising radiation for
medical/dental purposes. REVOKED BY S.I. No.
478 of 2002 European Communities (Medical Ionising Radiation
Protection) Regulations 2002
Also revoked by the same S.I. is European Community (Radiological
and Nuclear Medicine Installations), Regulations, 1998 (S.I. No 250
of 1998.)
- European Communities (Ionising Radiation) Regulations, 1991 (S.I.
No.43 of 1991) which implements, in this country, the EC Directives
on the protection of the general public and workers against the dangers
of ionising radiation (80/836/Euratom of 15 July 1980 as amended by
84/467/Euratom of 3 September 1984). In particular these regulations,
stipulate dose limits for both occupational and public exposure, require
the notification and reporting of activities involving ionising radiation
and define what constitutes offences under the said regulations.
- Radiological Protection Act, 1991 (General Control of Radioactive
Substances, Nuclear Devices and Irradiating Apparatus) Order, 1993
(S.I. No. 151 of 1993) under which activities involving exposure to
ionising radiation are prohibited save under licence issued by the
RPII.
- The Safety, Health and Welfare at Work Act, 1989 (No.7 of 1989).
- In addition, the Minister for Health has powers under the Health
Act, 1953 (No. 26 of 1953) to make regulations for the control of
the use, etc. of radioactive substances and irradiating apparatus
in the medical and dental areas.
- The RPII's regulatory policy is also designed to reflect the most
recent 1990 Recommendations of the International Commission on Radiological
Protection [ICRP, 1991].
European Communities (Medical Devices) Regulations, 1994, Statutory
Instrument No. 252 of 1994. These regulations transposed the Medical
Devices Directive 93/42/EEC into Irish law and became mandatory on 14th
June,1998.
RETURN TO TOP
3. Implications for the Practice of Dentistry
The following are the major implications of the above legislation for
the practice of dentistry in this country.
- A licence for the custody of dental radiographic equipment must
be obtained from the RPII. This should be applied for at least 28
days before starting work with equipment. The Dental Council informs
all new entrants to the Dental Register of these requirements. Any
change in the type and use of equipment, ownership or address at which
it is used shall be notified to the RPII.
- All radiographic exposures shall be clinically justified and kept
as low as reasonably achievable and planning of exposures should be
carried out with due regard to the measures outlined in this Code,
- In each practice a named dentist who is appropriately trained is
required to take day-to-day responsibility for radiological protection.
It will be the responsibility of this person to see that the Code
is adhered to and that any staff who are involved in work with radiographic
equipment are properly trained and any female staff employed in the
practice are made aware of the possible hazards of ionising radiation
during pregnancy.
- The dentist must ensure that all radiographic equipment under his
responsibility conforms to the standards outlined in this Code.
- The inspection of dental surgeries may be undertaken by the RPII
to ascertain if adequate radiological protection measures are being
taken.
- If the workload is high i.e. over 350 intra-oral or 40 panoramic
films per week, or when using cephalometric techniques then the possible
use of protective barriers and structural shielding of installations
must be evaluated.
4. Training
Radiographic equipment may
only be used under the direction and supervision of dentists who have
had adequate training in radiological protection and radiographic techniques
as approved by the Dental Council. Persons other than dentists may operate
dental radiographic equipment only under the direction and supervision
of a dentist, as described in in Section 3 (iii) above and if they have
followed a course of training in radiation protection and radiographic
techniques approved by the Dental Council. Persons, other than dentists,
assisting in carrying out dental radiographic procedures must have received
instruction and training in radiological protection measures as appropriate
to their work: it is the responsibility of the licensee to ensure that
this training is provided.
RETURN
TO TOP
5. Responsibility for Radiological Protection
(a) Private Practice. The dentist is the person responsible for all aspects
of radiological protection in private dental practice. Where more
than one dentist is in the practice then a particular dentist shall
be given this responsibility. The dentist with responsibility for
radiological protection is referred to as the Radiological Protection
Officer (RPO)
It is the RPO's responsibility to ensure that the dental facility
complies with the safety requirements outlined in this Code, and
that radiographic equipment works satisfactorily and is operated
only by trained personnel. The RPO shall also establish procedures
so that this code is applied by the staff. Where necessary, for
example when sophisticated equipment such as an OPG unit is being
used, the RPO shall consult with a qualified (person) in radiological
physics, when exercising these responsibilities.
The dentist must hold a licence from the RPII for the custody and
use of all radiographic equipment for which he is responsible.
(b) Health Board and Hospital Based Equipment. Ultimate responsibility
for ensuring the licensing of radiographic equipment and for radiological
protection in Health Board facilities, in hospitals (including dental
hospitals) and other institutions rests with the employing authority.
In the case of equipment located in Health Board facilities the principal
dental surgeon of each administrative area shall be appointed to act
as RPO for that area. One of the RPOs shall also be nominated to act
as the RPII contact person. The contact person shall communicate with
the Institute in regard to such matters as to the licence and the
implementation of repairs and improvements which the Institute may
call for following an inspection.
In each health centre with dental radiographic facilities a named
dentist shall be nominated to act as Radiological Safety Officer.
These Safety Officers shall assist the RPO in carrying out his responsibilities.
Health Boards and other bodies which hold dental X-ray equipment
must hold a licence from the RPII for its custody and use.
Health Boards and other institutions shall also establish or be
party to administrative structures including a Radiation Safety
Committee. This committee shall provide advice on all aspects of
radiological protection in dentistry.
This committee may be one and the same body as that which has responsibility
for general medical radiation safety or, where considered more appropriate,
a separate entity. Membership of the committee should include the
principal dental surgeon in each administrative area, a radiologist,
radiological protection advisor (who shall be a qualified expert
in radiological physics), medical officer and representatives of
both management and clinical staff.
RETURN TO TOP
6. Radiographic Equipment
All X-ray apparatus shall be maintained, serviced and have its performance
checked annually by suitably qualified and competent persons.
A full Quality Assurance inspection to insure compliance with Appendix
2 as well as an assessment of electrical and mechanical safety shall
be carried out on all new equipment, and every two years thereafter,
by a competent expert. The expert shall be independent of the supplying
company. The frequency of inspection may be altered with expert advice.
Particular attention shall be paid to old equipment.
It should be noted that the following equipment features are mandatory
since 1st January 1995.
1. An electronic timer which is capable of terminating an exposure
at a pre-set time (max. 5 seconds).
2. Voltage 'mains on' and 'exposure' warning lights to be fitted on
the control panel.
While the lower limit for kilovoltage shall remain 50kVp, for all units
purchased since 1st January 1995, the kilovoltage shall be in the range
60-75 kVp.
The user shall keep a record of the dates and results of all checks
and servicing. The RPII may require objective evidence that performance
checks and servicing have been carried out before issuing or renewing
a licence.
7. Location of Equipment.
The equipment may be located in the dental surgery or a separate room.
There shall be sufficient space and the exposure cable shall be long enough
to allow the operator and staff to maintain a distance of at least 2 m
from the tube head. In the case of pantomographic or cephalometric equipment,
the unit should be operated from behind a protection screen or wall. Access
to the room shall be limited during a radiographic exposure.
8. Film Processing and Storage
It is essential that meticulous attention shall be given to processing
techniques and the proper use of developing and fixing solutions in order
that repeat X-ray examinations are not necessary. Manufacturers' recommendations
with respect to strength of solutions, temperature and time must be followed
to ensure optimum development. Solutions should be replenished or replaced
as necessary. Even unused developer deteriorates with time. It is important
to note that chemicals and films have limited shelf lives and must not
be used after the manufacturers' specified expiry dates.
Cleanliness is important to reduce film artefacts for both manual and
automatic film processing. Automatic film processors shall be cleaned,
services and have the quality of performance assessed in accordance
with the manufacturers' recommendations.
Storage and processing facilities shall be designed and located so
that films are not exposed to more than 2µGy* prior to development.
A dark room shall be well blacked out to prevent fogging of films and
the safe light equipped with an appropriate filter. The film storage
container shall be adequately shielded to prevent exposure of films
and should be kept in cool and dry conditions (10-200C) * 1 Gray (Gy)
= 1 J/kg (joules/kilogram)
9. Procedures to Minimise Doses to Patients
- Only those X-rays which, after a clinical examination and a careful
consideration of both the dental and general health needs of the patient,
are found to be necessary for patient care shall be carried out. The
routine use of X-rays without a specific dental or associated need
is not warranted. It shall be determined if there are any previous
X-ray examinations which would make further examination unnecessary.
- The operator shall use the minimum exposure time consistent with
obtaining a good quality film. This includes using the fastest film
which will give the necessary contrast and detail and with extraoral
films the use of cassettes with intensifying screens.
- Unnecessary repeat films shall be avoided by using a proper technique
and reliable and consistent processing.
- Films holders and bitewing films should be used to save the patient
having to hold the film
- As it is difficult to differentiate between categories if patient
at a particular risk from radiation, a protective lead apron, preferably
with a thyroid collar, should be worn by all patients having
X-ray examinations, but shall be worn by patients when taking vertex
occlusal films. In panoramic radiography, since the source of the
radiation is coming from the back of the patient, dual (front and
back) lead aprons should be used.
- Particular care should be taken with women who may be or are pregnant.
A protective apron shall be provided to protect the foetus.
- Clinical records shall include details of all X-ray examinations
carried out.
RETURN TO TOP
10. Operator and Staff Protection
- Only those X-rays which, after a clinical examination and a careful
consideration of both the dental and general health needs of the patient,
are found to be necessary for patient care shall be carried out. The
routine use of X-rays without a specific dental or associated need
is not warranted. It shall be determined if there are any previous
X-ray examinations which would make further examination unnecessary.
The operator and other staff shall not stand in the direct beam during
exposure nor shall they hold the tube housing or the cone
- The dental film, wherever possible, should be fixed in position,
otherwise it should be held by the patient. The dental practitioner
or other personnel shall not hold the film in place during exposure.
- The operator and other staff shall stand at least two metres away
from the tube head and patient during exposure and only those people
whose presence is essential should remain in the X-ray room during
exposure.
- The operator should stand behind a protective barrier with a lead
equivalent of not less than 0.0 mm if the workload is high i.e. above
350 intra-oral or 40 panoramic films per week or when using cephalometric
techniques.
- If persons are needed to assist children or weak patients they shall
avoid the direct beam and must be provided with a lead apron. The
same person must not regularly perform these duties.
- Checks shall be made of does received by staff. Monitoring badges
shall be worn continuously by all staff involved in work with ionising
radiation. Badges shall be worn on the trunk between the level of
the shoulders and the hips, and changed every eight weeks. The above
arrangement shall not apply to pregnant staff who should wear the
badge over the abdomen and have them changed fortnightly during the
8-15 week period of the pregnancy and monthly for the remainder of
their pregnancy. Alternatively, it may prove more convenient to change
the badge fortnightly from the date of declaration of pregnancy until
the woman goes on maternity leave. All monitoring badges shall be
obtained from the Dosimetry Service of the RPII, or from another laboratory
approved by the Institute and returned thereto for examination. Records
of doses received by staff shall be kept by the licensee.
- It is the dentist's responsibility to see that all members of staff
involved in work with ionising radiation receive information about,
and training in, the radiological protection measures outlined here.
Special attention should be applied to the protection of women of
childbearing age and of pregnant women. It is the duty of the dentist
to inform any such employee in his practice of the possible hazards
to the foetus of ionising radiation. A protective lead apron must
be worn by pregnant women operating or assisting in radiographic procedures.
- An X-ray room shall not be used simultaneously for more than one
radiological investigation.
RETURN TO TOP
11. Protection of the Public.
- The direct beam shall not be directed through doors or windows or
wooden floors behind which persons may be situated. Normally, the
direct beam will be restricted to certain main directions and the
locations to which the beam is directed shall have adequate thickness
of absorbing materials, i.e. brick or concrete, in order to protect
persons working or living in adjacent locations.
- Normally, only small levels of scattered radiation are detectable
on the inner walls of dental surgeries. There is therefore no need
for heavy structural shielding to protect from scattered radiation.
However, if the workload is high, i.e. more than 350 intra-oral or
40 panoramic films per week or when using cephalometric techniques,
and depending on such factors as the maximum voltage of the machine
and the distance from the source of radiation, the installation of
structural shielding may be necessary. Advice may be obtained from
the RPII or the Radiation Safety Committee where appropriate.
12. Accidents
Any accident involving exposure or suspected exposure to ionising radiation
must be reported as soon as possible (and within 48 hours) by the dentist
or employing authority to the RPII and the Radiation Safety Committee
where one exists.
13. References
International Commission on Radiological Protection, 1991. 1990
Recommendations of the International Commission on Radiological Protection.
ICRP Publication 60, Annals of the ICRP, Vol. 21, No. 1-3, 1991,
Oxford: Pergamon Press.
14. Additional Information
Further advice and information on radiological protection are available
from the Regulatory Service of the RPII. Queries should be addressed to:
Radiological Protection Institute of Ireland
3 Clonskeagh Square
Clonskeagh Road
Dublin 14
Copies of the relevant legal documents are available from:
GOVERNMENT PUBLICATIONS
Sale Office
Sun Alliance House
Molesworth Streer
Dublin 2
APPENDIX 1
Summary of Requirements of Legislation Governing the Control of Sources
of Ionising Radiation
- A licence must be obtained from the RPII for radioactive substances
and irradiating apparatus (including dental X-ray units) in accordance
with the requirements specified in S.I. No. 151 of 1993.
- From the regulations set out in S.I. No. 43 of 1991, it can be seen
that all medical exposures must be clinically justified and the need
to keep such exposures as low as is reasonably achievable in emphasised.
Strict limits on does to workers and members of the public are laid
down. (See Tables 1 and 2)
- Medical/dental procedures involving ionising radiation must be carried
out under the responsibility of qualified doctors/dentists who have
acquired competence in radiological protection and have been trained
in diagnostic radiology techniques.
- Equipment which no longer reaches the criteria laid down by the
RPII must be taken out of service and permanently disabled.
- All radiographic equipment which is in use shall be kept under strict
surveillance with regard to radiological protection and quality control.
Table 1
ANNUAL DOSE
LIMITS FOR OCCUPATIONALLY EXPOSED PERSONS
|
Dose Limit |
Dose Constraint* |
| Effective dose |
20 mSv |
5 mSv |
| Lens of the eye |
150 mSv |
5 mSv |
| Hands and feet |
500 mSv |
50 mSv |
| Skin |
500 mSv |
50 mSv |
*Most applications of ionising radiation in Ireland, including its
use in dentistry, are such that annual doses received by occupationally
exposed persons should be well below the annual limit of 20 mSv. Accordingly,
the Institute requires dentists to constrain doses to occupationally
exposed persons to those in column 3 of the table above. Furthermore,
dentists should carry out an investigation of any practice which in
any 8-week period gives rise to a dose in excess of 1 mSv. In this way,
problems with the use of X-ray units and the radiological protection
of personnel can be detected at a relatively early stage of development.
(The equivalent dose [H] takes into account the effect of the
type of radiation and is measured in Sieverts [Sv]. H = D [absorbed
dose in tissues:Grays] for general dental and hospital applications,
such that 1 Sv = 1 Gy. The Sievert is such a large unit that for medical
applications, dose is measured in milliSieverts [mSv] and microSieverts
[µSv]. The effective dose equivalent (HE) is the dose which,
if given to the whole body would give the same risks of mortality as
the non-uniform dose resulting from the particular examination. For
an intra-oral: 0.01 manSieverts; for an OPG: 0.08 manSieverts.
Table 2
ANNUAL DOSE
LIMITS FOR NON-OCCUPATIONAL EXPOSED PERSONS
|
Dose Limit |
Dose Constraint* |
| Effective dose |
1 mSv |
0.05 mSv |
| Lens of the eye |
15 mSv |
0.05 mSv |
| Skin |
50 mSv |
0.05 mSv |
* The value of 0.05 mSv applies to the "public at large" that is persons
who have no involvement with the clinic - e.g. persons living in an
adjacent dwelling house. In the case of the public who are in the employ
of the dentist or dental clinic, but not as exposed workers, a figure
of 0.5 mSv per year shall apply.
