CUSTOM MADE (SPECIAL) TRAYS.

1. CUSTOM MADE (SPECIAL) TRAYS. A aid for the client (Dentist, DCP) to obtain more accurate impressions of the soft and hard tissues in the oral cavity.

2. Stock Trays. Stock trays are made from either plastic or metal and come in all shapes and sizes. Careful selection of the stock tray can lead to accurate impressions if slight modifications are carried out. Plastic trays can be heated, then bent. Metal trays can be altered using a pliers.

3. Stock Trays. Silicone putty, composition, and wax can also be added to provide better sulcus or palatal fit. In general, they fit where they touch and rather than utilise precious chairside time, custom made (special) trays are prescribed.

4. The materials and techniques used in the manufacture of these aids are introduced in this lesson.Following a Staff demonstration, you will make a lower custom tray for an edentulous mouth with finger stops and an upper custom made tray for a partially dentate mouth. Custom Made (Special) Trays.

5. Laboratory Competencies.At the end of the lesson and following self directed study, you will:-Know the uses of special trays and the principles underlying the construction of special trays.Consolidate knowledge of the properties and types of materials used in special tray construction.Fabricate partial and edentulous special trays.

6. Performance Criteria.Evaluate the casts and theprescription to determine what needs to be incorporated into the design of the special trays.Apply appropriate spacermaterials (wax or wet cloth)to the cast to :- eliminate undercuts- provide the correct amount of space for the subsequent impression material to be used by the client e.g. elastomers – minimal, alginate - 3mm.Apply a separating medium (Cold Mould Seal) to the cast that is appropriate for the cast material and the processing method to be used.

7. Select materials that are appropriate to the nature and construction requirements of the special tray and prepare them in the correct manner and quantity (Pmma - heat cure, self cure, visible light cure or Thermoformed – shellac, pull down).Form the tray over the cast to predetermined peripheral outline, fix appropriate handles (tray material, wire or preformed), and finger rests. Process materials using the correct method for the material concerned. Preform retention if necessary.

8. Separate the special tray from the cast in a manner that prevents damage and remove any spacing materials that remain.Smooth the periphery, handle and other surfaces of the special tray and perforate the tray surface if this is prescribed.

9. Confirm that the finished special tray: - is clean - is free of defects - conforms to the prescription.Effectively clean and disinfect the special tray, correctly identify it with the patients unique reference and date of production and return it to the client at the correct time. Make complete, accurate and up-to-date records relating to the identification, components and manufacture of the special tray and store the records in the correct location consistent with relevant legislation.

10. Summary. Custom Made (Special) Trays must be:- Clean and smooth, rigid and strong, Biocompatible Permit the correct thickness of impression material to be used, Handle shaped correctly and attached so that it does not displace the lip when impression is taken, Hold the impression material in the correct position in the mouth and cover the whole area required, Support the impression material during setting and removal, thereby preventing distortion.