Pregnancy Dental Care
Regular visits
to the dentist both before, and during pregnancy, is recommended
to ensure that your gums and teeth are healthy. As many women
experience bleeding gums during pregnancy, visiting your dentist
regularly for a scale and clean, together with good oral hygiene
which includes brushing with a fluoride toothpaste at least
twice a day and flossing regularly, is imperative.
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Rubber Latex Allergies
Overview
Natural rubber latex is a common ingredient
found in many consumer products, such as balloons, balls,
appliance cords, hoses, hot water bottles, pacifiers, swimwear,
toys, tires, condoms, rubber bands and shoes. Latex also can
be found in many medical or dental supplies and devices, such
as masks, gloves, syringes, catheters, dressings, tape and
bandages.
Unlike
some consumer goods made from synthetic (manmade) latex, such
as house paint, natural rubber latex is derived from a milky
substance found in rubber trees (Hevea brasiliensis).
While many people come in safe contact with latex-containing
products every day, some susceptible individuals have developed
hypersensitivity to proteins derived from natural rubber latex,
which can cause allergic reactions.
Causes
and Symptoms
Latex allergy generally develops after
repeated exposure to products containing natural rubber latex.
When latex-containing medical devices or supplies come in
contact with mucous membranes, the membranes may absorb latex
proteins. The immune system of some susceptible individuals
produces antibodies that react immunologically with these
antigenic proteins.
This
is a concern particularly for health care workers who are
constantly exposed to latex examination or surgical gloves
and other latex-based health care products. The powder used
on latex gloves can absorb the gloves' latex proteins and
cause increased exposure to latex. In addition, as the gloves
are removed, the powder may become airborne, coming in contact
with the eyes, nose or mouth.
When
exposed to latex proteins, a latex-sensitive individual, whether
a health care worker or a patient, may experience minor symptoms,
such as hives or nasal congestion. Severe cases may result
in anaphylaxis, a dangerous systemic reaction that causes
a drop in blood pressure, difficulty breathing, swelling of
the throat, tongue and nose, and even loss of consciousness
and could be life-threatening if unattended. Emergency medical
attention is needed at the first sign of anaphylactic reaction.
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Digital
Radiography
Introduction
Digital radiography
has been used widely in medicine, but it was only in the 1980s
that the first intra-oral sensors were developed for use in
dentistry. Unfortunately, the early systems could not capture
panoramic and cephalometric images, and this made it impossible
for surgeries to abandon film processing and adopt digital
technology. Recently, the development of cost-effective intra-
and extra-oral digital technology coupled with an increase
in computerization of practices has made digital imaging a
superior alternative in many respects to conventional film
imaging.
Advantages
of this type of system for the orthodontist and the patient
include the ability to gain cephalometric analysis and superimposition
quickly on the chairside computer, manipulation of images
to aid diagnosis, dose reductions, and the ease of storage.
Principles
Conventional
imaging
Conventional
intra-oral radiographic film consists of silver halide grains
in a gelatine matrix. When this film is exposed to X-ray photons
the silver halide crystals are sensitized and are reduced
to black during the developing process. The film acts as both
the radiation detector and the image display.
With extra-oral
films indirect action receptors are used to help record the
image. This type of film is sensitive to light photons which
are emitted by adjacent intensifying screens. Although the
film is constructed of silver halide crystals these are primarily
sensitive to light rather than X-rays. The use of intensifying
screens reduces the dose and can be used where fine detail
is not required.
Digital
imaging
In digital
radiography, instead of the silver halide grain 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.
Image
acquisition
There are
two ways to acquire a digital image.
Indirect
acquisition
A digital
image can be produced by scanning conventional radiographs
using a flatbed scanner and a transparency adaptor, or by
using a charged coupled device camera instead of the flatbed
scanner. This image can then be manipulated using software
packages or be passed on to a second party via a modem.
Direct
digital imaging
There are
two systems available, one produces the image immediately
on the monitor post-exposure and is therefore called Direct
Imaging. The second has an intermediate phase, whereby the
image is produced on the monitor following scanning by laser.
This is known as semi-direct imaging.
Semi-direct
image plate systems. The image plate method involves the use
of a phosphor storage plate (PSP). This plate stores energy
after exposure to radiation and emits light when scanned by
a laser. The scanner stimulates the phosphor plate and stores
a record of the number of light photons detected.
Loading of
the scanners generally only requires subdued
lighting as the plates are slightly sensitive to visible light.
However, some products are more light sensitie than others.
The lasers used are centred around the 600-nm band and are
usually of the helium-neon variety. Scanners, the size of
a breadmaker, can accommodate multiple image plates at any
one time. The exact numbers varies between manufacturers.
There is a
delay while the image is ‘developed’ before it appears on
the monitor. Up to eight bitewing radiographs take about 90
seconds and a panoramic image can take approximately 3 minutes
to be scanned. Again, the scan times do vary between manufacturers.
Although the plate can store energy for a number of days,
information starts to be lost within minutes after exposure
and it is advised to scan the plates quite quickly to optimize
the image recovered. To fully remove the latent image the
plate should be exposed to high intensity light (as found
on viewing boxes).
Image plates
are available in exactly the same sizes as conventional film
and come with disposable plastic barriers. They have no wires
attached and are reusable for thousands of exposures, but
do need careful handling to avoid surface damage. Current
systems have a spatial resolution of 6–8 LP/mm.
Direct
sensor systems. The sensor for the radiation
image is usually a Charge Coupled Device (CCD). It consists
of silicon crystals arranged in a lattice and converts light
energy into an electronic signal. This technology is widely
used in video cameras. The sensor cannot store information
and must be connected via fibre optic wires to the monitor,
which can make the sensor bulky and awkward to use.
The greatest
advantage of the direct sensor system is the gain in time.
The image is directly projected onto the computer screen.
Originally, the active areas of the sensors were smaller than
conventional film, which increased the incidence of ‘coning
off’ and required repeat exposures to capture all the desired
information. Recent innovations have produced sensors approaching
or equal to standard film sizes.
Extra-oral
digital imaging
Extra-oral
digital imaging is available using both systems. However,
the larger CCD sensors are extremely expensive and usually
requires the purchase of new X-ray generators, although a
‘retro-fit’ system has been developed in the USA. These constrictions
effectively mean that the PSP method is the one most commonly
used.
Panoramic
radiography
The PSP method
of panoramic digital imaging is very similar to conventional
film. The film and intensifying screen are replaced by a storage
phosphor plate. The plate is scanned after exposure, which
can take up to 3 minutes or longer depending on the product
used. The resolution of these systems is greater than 4 LP/mm.
Cephalometric
radiography
Naslund et
al. investigated the effect of dose reduction obtained with
PSP on the identification of cephalometric landmarks and concluded
that dose reductions of up to 75 per cent did not effect the
localization of cephalometric landmarks.1 It is also worth
noting that with CCD sensors the image is acquired over 15
seconds as the sensor and narrow X-ray beam move up the facial
bones and could lead to an increase in the incidence of movement
artefact.
Advantages
of digital imaging
Dose reduction
Dose reductions
of up to 90 per cent compared to E-speed film have been reported
by some authors in the diagnosis of caries.2 Although some
researchers do claim dose reductions compared with conventional
extra-oral film, in practice the background noise rises 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. This can effectively compensate for
over or under exposure of the digital image. It has been shown
that contrast enhancement of CCD devices were more accurate
than E-speed film for detecting simulated caries under orthodontic
bands.3
Measurements.
Digital callipers, rulers and protractors are some of the
many tools available for image analysis. Many authors have
reported on their application in cephalometric analysis.4,
5 The images can also be superimposed onto each other and
onto digital photographs.
3-D
reconstruction. This application can be theoretically
used to reconstruct intra- and extra-oral images. The uses
range from profiling root canals to visualizing facial fractures
in all three dimensions.
Filtration.
The addition of filters to the airspace around the face can
clarify the soft tissue profile if the original soft tissue
image was poor.
Time
Much time
is gained especially with the CCD system where the image is
displayed at the chairside immediately post exposure. Although
a lag time between scanning and the appearance of an image
exists with the PSP method it is still substantially faster
than conventional developing processes in general use.
Storage
Storage was
initially a problem before the development of DVDs and CD
ROMs as three peri-apical images would fill a floppy disc.
However, now a CD ROM can hold over 30,000 images. This means
that images can be stored cheaply and indefinitely.
Teleradiology
The digital
image file can be further reduced in size by compression techniques,
and sent via a modem and telephone line to colleagues for
review. This had the advantages of not losing radiographs
in the post and saving time if an urgent appointment is required.
The operator at the other end can also manipulate the image
if desired.
Environmentally
friendly
No processing
chemicals are used or disposed of. Both CCD sensors and the
PSP plates are capable of being reused for many thousands
of exposures. They can, however, become scratched and damaged
if not handled carefully.
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Disadvantages
of digital imaging
The majority
of the disadvantages are associated with the CCD system.
Cost
Currently,
the cost of converting from intra-oral film to digital imaging
is approximately 6600 Euros. This initial outlay should be
offset against the time saved and the efficiency of storage
of the images.
Sensor dimensions
These are
still quite bulky for the CCD system and awkward to position
due to trailing fibre optic wires. The original problem of
small sensor active areas has been rectified and the same
amount of information can be captured as conventional film.
Cross-infection
control
Each intra-oral
sensor and plate must be covered by a plastic bag, and this
bag is changed between patients. However, if they become directly
contaminated there is no way of sterilizing them and they
should be discarded regardless of expense.
Medicolegal
Concerns have
been raised in the past about the ability to manipulate the
images for fraudulent purposes. Manufacturers of software
programmes have installed ‘audit trails’, which can track
down and recover the original image. Many insurance companies
in Australia are accepting digital images as valid attachments
when the claims are electronically claimed.
Conclusions
The technology
is now available to run a practice almost paper free. It is
theoretically possible to store clinical notes, photographs,
radiographs, and study models on disc, and refer or consult
online. The future of digital imaging could include the testing
and upgrade of X-ray equipment and software on-line. Research
is also continuing into the development of a credit card sized
‘smart card’, which could carry a patient's medical and dental
notes along with their radiographic images. It is important
that advances in technology are accepted and the benefits
that they produce utilized in order that clinical practice
and patient care continue to improve.
