The ADAPT Evaluation - Transform impression trays

Chairman Howard Stean and Robert Brody of ADAPT, present the group’s clinical evaluation of Transform mouldable plastic impression trays.

Transform impression trays by Astek Innovations, are marketed as part of the Pegasus range of dental products. The advantage of the trays is that they are adaptable for situations where standardshaped trays would not be suitable. The trays may be moulded by immersion in hot water at 70 °C for 20 seconds, which softens the plastic prior to reshaping the edges and general shape. On cooling the tray hardens and will retain its shape. They may also be trimmed or added to marginally as normal. ADAPT has been asked to evaluate these trays in dental practice. ADAPT evaluators used the trays for a variety of clinical applications and also undertook some laboratory testing. The laboratory testing was designed to monitor such alteration in shape, principally for stability of the change, as any rebound will distort the impression and ruin the subsequent laboratory items made from the resultant work model. The immediate feel of the trays was that they are strong and firm and inflexible. The trays come in sets of six sizes, for each of dentate and edentulous impressions.

Basic design

The retention perforations seem very adequate whilst not weakening the rigidity of the tray. There is a ridge along the edges The ADAPT Evaluation Transform impression trays evaluators made use of an electrically heated water bath set to 70°C. No problems were found with results from the impressions, and there were no complaints from patients about ill-fitting trays. One evaluator commented that a tray was successfully adapted to avoid a bony torus, which was considered to be an advantage to the extent that a special tray was not needed. Another evaluator used a tray for the pick-up of an implant impression coping. It is usual to drill a hole in a tray to permit the coping to be undone after setting of the impression material. It was found that some ‘healing’ of the plastic occurred when the position of the hole was somewhat varied by drilling laterally. This was also thought to be an advantage. ADAPT opinion Overall the trays performed well, with no problems noted over a period of several weeks’ use. ADAPT can recommend use of the Transform trays to colleagues. that may have been designed to enhance the edge-strength although the trays may be trimmed if overextended at any point. One evaluator felt that if the ridge had been rather than on the external surface, on the inner surface it may have further enhanced retention of the impression material, as is the virtue of the rim-lock tray design. Perhaps patent aspects are involved in this. There is an excellent video describing the use of the tray on Astek Innovations website.

Laboratory test

A lower dentate tray was used in this test. Each end of the tray in turn was immersed in hot water and became softened within 20 seconds. One end was squeezed together and the other end was expanded. After 10-15 seconds the tray had cooled and felt rigid again. There are regular indentations in the edge-ridge. These were marked to reference the measurement points and immediate measurements were noted. The initial width of the tray was 20mm at point of measurement. Following the adaptation as described above, one side was reduced to 14mm and the other expanded to 27.5mm, measured with a digital caliper/micrometer. The measurements were repeated daily for one week and again after two weeks. The trays remained exactly stable throughout the test period and completely reliable following heat modification. The developers of this tray have found a plastic that has excellent thermoplastic qualities that are ideally suited to their purpose.

Clinical evaluation procedure

A team of ADAPT dentists agreed to use the trays in general practice. They were for a selection of treatment impressions including alginate and also synthetic elastomeric materials. No adhesives were routinely applied, as the perforations are designed to retain materials securely. Where applicable tray margins were altered using the correct procedure. Some evaluators made use of an electrically heated water bath set to 70°C. No problems were found with results from the impressions, and there were no complaints from patients about ill-fitting trays. One evaluator commented that a tray was successfully adapted to avoid a bony torus, which was considered to be an advantage to the extent that a special tray was not needed. Another evaluator used a tray for the pick-up of an implant impression coping. It is usual to drill a hole in a tray to permit the coping to be undone after setting of the impression material. It was found that some ‘healing’ of the plastic occurred when the position of the hole was somewhat varied by drilling laterally. This was also thought to be an advantage.

ADAPT opinion

Overall the trays performed well, with no problems noted over a period of several weeks’ use. ADAPT can recommend use of the Transform trays to colleagues

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