1. Why use a custom tray? Better fit than stock trays
Less impression material needed
More accurate impression because of better fit

2. Are there any disadvantages to using custom trays?
Yes
Cost of laboratory processing
Staff time
Staff training

3. What types of procedures warrant the use of a custom tray?
Final impressions for full dentures
Final impressions for partial dentures
Final impressions for multiple crowns
Final impressions for bridgework
Final impressions for multiple implants

4. What procedures do not require a custom tray?
Orthodontic evaluation
Bleaching tray construction
Sports guard construction
Night guard construction
Treatment planning
Single crown construction (Dr’s option)

5. Criteria for an acceptable custom tray:
Tray must be sufficiently rigid to hold and support materials needed during tray placement and removal
Tray must fit and adapt well to the arch and must maintain patient comfort without impinging on surrounding tissues.
Tray must provide accurate adaptation to an edentulous or a partially edentulous arch.
Tray must maintain an even distribution of 3 to 4 mm of impression material between itself and teeth.

6. Criteria for an acceptable custom tray:
The completed maxillary tray must cover the teeth and hard palate and extend slightly beyond the gingival margin (but not into muccobuccal fold).
The primary materials used to construct custom trays are self-curing acrylic resin, light-cured resin, and thermoplastic material. Regarless of the material used in construction of the tray, a diagnostic model must be prepared first, in accordance with specific guidelines.

7. Common custom tray materials
Self cure resin
Light cure resin
Thermoplastic (Tak balls)
Thermoplastic (Easy Tray)
Thermoplastic (Vacuum former sheets)

8. Steps in construction of custom tray?
*Some steps will vary depending on material used in construction
Outlining – pencil where the margins of the tray will go

9. Filling up undercuts
Undercuts – recessed areas on a model must be filled in prior to making a custom trays or it will be difficult to remove or place impression tray

10. Spacer/ Wax Relief
Spacer/ wax relief – material used to hold space for impression material, baseplate wax or tissue. When using wax, soften wax over flame or in water bath. Then adapt to model, keep within outline, using wax knife trim excess, when happy with wax use a hot instrument to lute wax to model
Spacer stops- prevent tray from overseating, cut 3mm ● or ▲ holes out of spacer. For edentulous place one stop on each 1st molar area and cuspid area. For tray on natural teeth, place stop near tooth but not on it

11. Spacer/ Wax Relief

12. Steps continued:
Separator- placed on spacer and model to allow easy removal of tray. Petroleum jelly, Coe-sep and Al-cote can be used as a separator. All these materials can be placed with a cotton tipped applicator

13. Self curing resins steps:
Prepare resin material – read instructions for each material before using it
For self curing resin: measure out full tray amount of liquid and powder, mix in wax cup or glass jar with tongue depressor
Lubricate hands with petroleum jelly
When mix has reached doughy stage, remove from cup

14. Self curing steps continued:
For upper tray form the resin into a patty shape (approx. size of spacer) adapt to cast, extend slightly posterior from spacer, trim excess with lab knife
For lower model form material in a hot dog shape and proceed as above
Use excess material to form handle, place a drop of monomer on handle and on tray, attach handle so it extends out of mouth in center of tray and is parallel to occlusal surfaces, hold handle until material becomes firm.

15. Finishing custom trays:
Some materials require extended curing time for final cure to take place
Rough areas can be adjusted using sandpaper rolls on the lathe or acrylic burs on the lab handpiece
All areas should be checked for sharpness; and eliminated to prevent tissue injury
Final smoothing is done with rag wheel, pumice and water on the lathe