Clinical
form of rough handling. All staff who handle PSPs should be aware that they must not bend or scratch them, since even normal handling can damage the surface. This marking can degrade the image significantly and is irreversible for any future image production. If the scanning system does
not have an integral white light clearer, then the plates should be placed on an X-ray viewing box to erase the latent image. Problems can occur when the plate is lifted off after clearing. If the plate is slid across the surface of the box, the plate can be scratched (Fig ı). To minimise the possibility of this occurring, the box can be covered with cling film or see-through bubble wrap, allowing the plate to be lifted off rather than slid across the surface. Custom-made mats are
available that resemble a rubber bubble wrap on which the plate can be placed prior to and after scanning, allowing the plate to be lifted off any work surface without scratching. To ensure that PSPs are
not marked beyond what is acceptable for image reading, the serial number should be taken and regular checks should be done to monitor for marks. To do this, the plate should be placed on a surface in its protective packet. No step wedge should be used. Next, the spacer cone should
be lined up with the plate at a distance of 20cm (the usual focal skin distance used in parallelling technique). The exposure given is very small (tiny flash exposure) and, when scanned, any marks will be visible. Each surgery should be responsible for its own plates. The time frame between these checks will vary in relation to the number of images captured and the quality of sensor handling by the staff.
2. Fogging limitation As the PSPs are very sensitive to radiation, even background radiation can base fog them. To limit this, the plate should be cleared every day by placing on a light box for a few minutes
before use. If this is done in the morning, the plate should be fine until the end of the day. Once again, to avoid marking,
cling film can be stretched over the viewing box or see-through bubble wrap placed on the box before placing the sensors, blue side down, on the surface to clear. Alternatively, if the scanner has an integral light clearer, the sensors can be cleared first thing every morning in the scanner.
3. Sensor positioning Problems can occur in relation to the image receptor not being firmly held by the bite blocks in paralleling technique holders, if the same bite blocks are used with the phosphor plates that were being used with X-ray film. An X-ray film packet is much thicker than a phosphor plate. Whereas an X-ray film has black paper around it, lead foil behind it and a thick waterproof cover, the phosphor plate is usually the only item in the waterproof packet and is consequently much thinner. The difference in thickness
of the sensor in the bite block compared to a film packet makes accurate positioning in the mouth very difficult, as the plate tends to slip off the holder. To avoid this happening, thicken the phosphor cover with a white cardboard bitewing tab (Fig 2). This tab also doubles as a “target” when checking the position of the sensor in the mouth before aligning with the spacer cone (Fig 3). The sensor now stays securely in the holder. This cardboard tab also protects the plate at the point where it is placed in the bite block and where it can easily be damaged.
4. Endodontic X-ray holders Due to the lack of back support on the endodontic holder, many image receptors bend in the roof of the mouth and the apex of the root is missed or elongated. Also, the image receptor also often moves in the holder making accurate imaging difficult. Use two
Continued » Ireland’s Dental magazine 41
Fig 3
Bitewing tab being used to thicken the PSP to prevent the sensor moving and provide a “target”
Fig 4
Bitewing tabs being used to support the upper part of the endodontic PSP to stop bending in the roof of the mouth and secure the sensor in the holder
Fig 5
Bitewing tab around the front edge of the waterproof cover to allow exact positioning
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