Impression material thickness in stock and custom trays.

This study did not examine the accuracy of the resultant impressions. Rather, the impression material thickness in impressions made using both the highly advocated custom acrylic resin tray and in the highly used manufactured stock tray was examined. Comparison between the material thickness at the prepared tooth area revealed a mean difference in material thickness of less than 1 mm. The question of the significance of this difference remains to be answered. If the difference is not significant in the success of the impression and the resultant casting, then there are several advantages in using the manufactured stock tray; the first is economy. The average cost of a custom acrylic full arch impression tray is $3.65, compared with an average cost of slightly over $0.30 for the stock tray. The second advantage is the convenience factor. Making a custom tray requires planning, study models, laboratory time, curing interval, and finishing time. In contrast, the stock tray can be selected, adapted, and used in a single visit for both anticipated and unanticipated situations. If the difference in material thickness is significant, the custom tray is indicated. However, attention to detail in making and inserting the tray in the mouth must be observed to maximize the benefits of the custom tray.