DENTAL IMPRESSION TRAYS
Second Stage
4. lecture
Dental Impression: It is an negative likeness or replica of the teeth and /or edentulous area and adjacent tissue. Complete dental impression: It is a negative registration of the entire denture bearing, stabilizing and seal area of either the maxilla or the mandible. In complete denture prosthesis, we make two impressions for patient: a) Primary impression. b) Final or secondary impression. To make an impression we should have impression tray. Impression tray: A device that is used to carry, confine, and control impression material while making an impression. Impression tray consists of two main parts: 1. Body. 2. Handle. Types of trays There are two main types:- 1. Stock Trays. . Stock tray for dentulous patient (Perforated). . Stock tray for edentulous patient (Non perforated). 2. Special Trays. Tray Selection 1. Select a tray with 4-5 mm of clearance with soft tissues. 2. Maxillary trays should extend from the labial vestibule to slightly beyond the vibrating line. 3. Mandibular trays should cover the retromolar pad area. 4. Trays can be modified with wax or impression compound to extend the tray if desired. Factors effect in selection of stock tray 1. The type of material use in the primary impression procedure . 2. Size of the arch. 3. Form of the arch. 4. The stock tray should cover all the anatomical landmark needed in the complete denture and this is a most important point. 5. Stock tray should give a sufficient space to impression material in all direction (the stock tray should leave sufficient room or space for impression material (4-5 mm). Special Tray (individual or custom tray) Individualized impression tray made from a cast recovered from primary impression it is used in making a final impression. Advantages of special trays: 1. They are easy to manipulate. 2. Economy. 3. Comfortable to the patient. 4. They accommodate the irregular feature of the mouth. 5. Control the flow of impression material. 6. Help to produce an impression of even thickness, small bulk and correct extension. The material used for making special tray 1. Cold cue acrylic resin (self-curer acrylic resin). 2. Shellac base plate. 3. Impression compound. Some time we can use hot cure acrylic but more common use cold cure acrylic resin, we have two types of special trays: 1. Close fit special tray. 2. Spaced special tray (without stoppers or with stoppers).
