Re: Lead Aprons in Dentistry

[Chris Alston <alstonc@odrge.odr.georgetown.edu>]

>References: <199802201605.IAA06474@www.icnpharm.com>
>Date:         Tue, 24 Feb 1998 09:38:03 -0600
>Reply-To: Medical Physics Mailing List <MEDPHYS@LISTS.WAYNE.EDU>
>Sender: Medical Physics Listserver <medphys@lists.wayne.edu>
>From: Marc Edwards <marcedw@SKY.NET>
>Subject:      Re: Lead Aprons in Dentistry
>To: Multiple recipients of list MEDPHYS <MEDPHYS@LISTS.WAYNE.EDU>
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>The use of lead aprons in dentistry is an artifact of obsolete equipment.
>Many years ago, the plastic pointed cone on a dental x-ray unit was just
>that, a pointer. The x-ray beam was basically uncollimated and the pointer
>was used to help aim the unit. For that equipment, lead aprons made sense.
>For current equipment (i.e. last 20 years or so) the cones and tube
>housing are well shielded, resulting in a well collimated beam. The only
>significant contribution to organ dose outside of the primary beam is from
>scatter within the patient, which would not be affected by a lead apron.
>The dose and associated risk from currrent dental procedures have been
>well studied (see for example S.C. White, Dentomaxillofac. Radiology Vol
>21, 118-26, 1992). The National Radiation Protection Board (UK) in
>Guidlines on Radiology Standards for Primary Dental Care (1994) has no
>mandatory requirement for routine use of lead aprons. The NCRP is
>currently revising Report 35 on Dental Radiation Safety and it is expected
>to contain similar recommendations. Unfortunately, the routine use of lead
>aprons has become so prevalent (indeed mandated by several State
>regulations) that it is likely to continue for some time.
>
>Although lead aprons result in minimal benefit to the patient, there are
>certain dental imaging procedures in which thyroid collars can result in
>lower thyroid dose. This is particulary imporant for children.
>
>The greatest reduction in risk to the dental patient is achieved by the
>use of rectangular collimation (as opposed to circular), the use of
>precise intraoral film positioning devices, and the use of  E speed film
>(as opposed to D speed). These measures have been appreciated by dental
>radiologists for many years, but are only slowly being adopted by the
>general dentist.
>
>Marc Edwards
>
>
>
>Sandy Perle wrote:
>
>>
>>
>> In a dental x-ray, the scatter will come
>> directly from the tube (which is in close proximity to the body,
>> unlike the chest x-ray) and the jaw area, thus irradiations the
>> primary organs, including the gonadal area and long bones in the
>> arm. While it is true that the collimator 'may" be lead lined, the
>> scatter from the tube and jaw area is of the magnitude where
>> measurable dose, in mrem, not microrem, can be detected. Therefore,
>> it is prudent to have the patent wear an apron,. since it will
>> reduce their exposure.
>>
>