Sir, I have recently had my eyes re-opened to the use of metal rim lock trays in everyday practice. With good management and communication with labs, these can be routinely used on the NHS as it is important to have an impression tray which will allow for more accurate impressions at the first time of asking. This should in turn reduce the need for unnecessary custom-made trays.

The use of plastic trays can be a false economy as the cheapness in cost is outweighed by the clinical loss of time and increased lab fees. The major flaw in these trays lies in their lack of rigidity meaning there is a risk of inaccuracies occurring both on seating and removal of the tray.

Material choice and impression techniques are also important aspects to consider. As the majority of denture impressions are taken in alginate it is even more important to use a rigid tray system as the material is inaccurate and has poor elastic properties. Two-stage wash impressions are at most risk of deformation as the putty induces excess stresses, which the plastic tray cannot handle effectively.

With the added retention present in rim lock trays it means we don't have to routinely use tray adhesives. Adhesives cause a huge number of inaccuracies as it is difficult to get an even spread and they are rarely given enough time to work, not to mention ruining clinical work tops. The presence of an integral metal handle also allows for added pressure to be applied towards the impression taking surface allowing for more accuracy. As metal trays are easily sterilised and if they are labelled correctly, I feel they should be routinely used as primary impression trays to improve the quality of work for patients as well as saving time and money for dentists.