Purpose: This article introduces a method of taking impressions accurately through the use of inner stoppers on a custom tray in order to fabricate precise prostheses.
Materials and Methods: The location of the stoppers is marked on the study cast with black or blue ink. Paraffin wax is placed on the study cast as spacers. The wax is perforated with a sharp hand instrument at the location of the stoppers in a cone shape at the posterior area and as four inclined planes at the anterior area. The custom tray material is mixed and placed on the study cast. The stability of the tray on the cast should then be checked.
Discussion: A cone-shaped stopper at the occlusal pit can guide the tray to the desired location. A stopper with an internal quadrangular pyramid can also guide the tray to its location.
Conclusion: The recommended shape and the location of stoppers stabilized the custom tray in the mouth, thus achieving an accurate impression.