What is a spaced tray?
Introduction. Spaced trays (Figure 2.3. 1) are used with alginate and elastomeric impression materials when undercuts are to be recorded. The material must be adequately thick to allow elastic deformation on removal from an undercut and avoid permanent distortion.
What is special tray in dentistry?
A special tray is an impression tray custom made for an individual patient by a denturist (dental technician), usually made from acrylic, such as polymethyl methacrylate, or shellac. A stock tray is used to make a preliminary impression, from which a model can be cast.
What is spacer design?
The spacer design for the selective pressure is directly governed by the knowledge of the stress-bearing and relief areas. Selective pressure can be achieved either by scraping of the primary impression in selected areas or by fabrication of a custom (special) tray with a proper spacer design and escape holes (relief).
What are the design considerations for the different types of special trays?
The dentist should consider the following key aspects of design when prescribing special trays in a given clinical situation:
- The material from which the tray is to be made.
- The desired extension of the tray.
- The thickness of any spacer to be placed on the cast.
- The location of any tissue stops.
What is special tray?
Special Tray A special tray is defined as, “A custom made device prepared for a particular patient which is used to carry, confine and control an impression material while making an impression”.
Why are special trays perforated?
Impression trays are used to hold the impression material, allowing the operator to place it into the patients’ mouth. They may be perforated for better retention of the impression material. Adhesives may be indicated with the use of some trays to aid in the retention of the impression materials.
What is a special tray?
Why do people make special trays?
Special tray provides even thickness of impression material. This minimizes tissue displacement and dimensional changes of impression material and produce impression with correct extension. 4. The work with special tray is easier and quicker than modifying stock tray to provide accurate impression.
What is the buccal shelf?
buc·cal shelf (bŭkăl shelf) Broad flat surface of the posterior mandible buccal to the teeth or alveolar ridge that provides denture support.
What is stopper in prosthodontics?
SPACERS WITH TISSUE STOPPERS: Tissue stoppers/ windows are made bilaterally at the canine and the molar region mostly 2mm in width. They help in proper vertical seating of the impression tray, they and control the thickness of the impression material.
What is beading and boxing?
Beading is done to preserve width and height of sulcus in a cast and boxing is done to obtain a uniform smooth well shaped base of the cast. Boxing can be defined as the enclosure (box) of an impression to produce the desired size and form of the base of the cast and to preserve desired details.
What are the characteristics of a special tray?
Ideal characteristics of special tray: A special tray should be 1. well adapted 2. dimensionally stable 3. free of voids and projections 4. 2-3 mm thick 5. with a handle. 6. 6. Rigid even in thin section. Special tray should not 7.
Where should a spacer be adapted in the special tray?
C. Adapting the spacer: A spacer should be adapted throughout the extent of special tray ( coincide with the second line), except posterior palatal seal area in maxilla and buccal shelf area in mandible. 34. Function of spacer: a.
What is a custom tray cavity?
➢Custom Tray Cavities Custom tray cavities formed to exactly match part or made to contact part only in certain areas building in clearance (areas of no contact) for fragile or areas requiring optical clarity. More information below. ➢Material Options Material options depending on part and application.
What are the requirements of an impression tray?
Requirements Of Impression Trays 1. The tray should be rigid and strong but not too thick. 2. The tray should simulate the finished denture in size and shape. 3. The border extension of the tray should be 2mm short of the vestibular depth with no interference with muscle or frenal attachment.