Overview of Impression Trays in Dentistry
Impression trays in dentistry are crucial tools used to create negative imprints of dental structures for various procedures. They come in different types such as stock trays and special trays, each serving specific purposes. The requirements for an effective impression tray include rigidity, proper sizing, smooth borders, and a well-angled handle. Understanding the classification, types, and advantages of impression trays is essential for dental professionals to ensure accurate and successful impressions in prosthodontics.
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SIBAR INSTITUTE OF DENTAL SCIENCES Department of Prosthodontics Related image Impression Trays Dr. Ramya. Sr.lecturer
IMPRESSION TRAYS DR. G. PHANI KRISHNA
DEFINITION A receptacle into which suitable impression material is placed to make a negative likeness; or A device that is used to carry, confine and control impression material while making an impression.
PARTS OF IMPRESSION TRAY Body Flange Handel
REQUIREMENTS OF IMPRESSION TRAY 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. 4. The entire borders of the tray should be smooth and rounded. 5. The tray should retain its shape throughout the impression procedure and pouring of impression. 6. The handle of the tray should be angulated.
CLASSIFICATION OF IMPRESSION TRAYS Impression trays are of two types: 1. Stock tray or Pre-fabricated tray 2. Special tray or Custom tray
Types of Impression trays: Maxillary / Mandibular Dentulous / Edentulous Various sizes: 1, 2, 3, 4 Various materials: Metal or Plastic or Acrylic
STOCK TRAY OR PRE-FABRICATED TRAY Fit to many patients Approximate shape of the arche various sizes Maxilla/ Mandible Used for Diagnostic or Primary impressions.
TYPES OF STOCK TRAY: (Dentulous or edentulous) Perforated Non perforated Rim-lock tray Segmental trays
ADVANATGES Rigid and support the set impression material. Dimensionally stable Tray is smooth, so injury to oral tissues is avoided. Multiple set in several patients.
DISADVANTAGES Dimensionally accurate impression is difficult to make with stock tray Uniform space is not available for impression material. Flanges of stock trays may be over extended or under extended
SPECIAL TRAY Fits only for a specific patient Used for secondary of final impression
TYPES OF SPECIAL TRAY Tray with spacer Tray without spacer/ Close fit
MATERIALS USED FOR FABRICATION OF SPECIAL TRAY Tray compound Tray acrylic Shellac Vacuum formed thermoplastic resin sheet Wax Old denture
ADVANTAGES Dimensionally accurate impression can be made Uniform space available for impression materials Over and under extension of tray flanges can be avoided Non stress bearing area can be relived with the use of spacer
DISADVANTAGES Can be used only for individual patient. Fabrication of custom trays is time consuming based on the material selected Rigidity is less when compared to metallic stock tray. Dimensional stability is less when compared to metallic stock tray
SPECIAL TRAY/ CUSTOM TRAY/ INDIVIDUALIZED TRAY
DEFINITION An individualized impression tray made from a cast recovered from a preliminary impression; it is used in making a final impression. BORDER BORDER MOULDING AND MOULDING AND SECONDARY SECONDARY IMPRESSION IMPRESSION PRIMARY PRIMARY IMPRESSION IMPRESSION PRIMARY CAST PRIMARY CAST SPECIAL TRAY SPECIAL TRAY
STEPS IN THE FABRICATION OF SPECIAL STEPS IN THE FABRICATION OF SPECIAL TRAY: TRAY: Outline Block out and relief Wax spacer adaptation
STEPS IN THE FABRICATION OF SPECIAL TRAY STEPS IN THE FABRICATION OF SPECIAL TRAY 1. 1. OUTLINE OUTLINE: : Extensions of the tray is outlined in the diagnostic cast, 2mm short of the vestibular depth to provide space for border moulding material.
2 2 BLOCK BLOCK OUT OUT AND AND RELIEF RELIEF: : Block out is done in those areas which prevent placement and removal of the custom tray. Wax relief is placed over tissues that are easily displaced and relief areas in the maxilla and mandible.
3 3 WAX SPACER ADAPTATION: WAX SPACER ADAPTATION: Wax spacer which 4mm short of the vestibular depth is adapted on the diagnostic cast before the adaptation of special tray material.
SPACER Use Use of of spacer spacer: : 1. Provides space for the secondary impression material in the special tray. 2. Provides relief for the easily displaced tissues and relief areas.
Spacer Designs Spacer Designs Based on the type of impression technique and type of impression material used, the design of the spacer varies. Based Based on on the the impression impression technique technique: : i. Mucocompressive technique No wax spacer is used ii. Mucostatic technique: Full wax spacer is used iii.Selective pressure technique: a) Maxilla: Full wax spacer with cut back in PPS, umbrella shaped, I shaped and T shaped spacers are used. b) Mandible: Full wax spacer with cut back in Buccal shelf Area.
OCCLUSAL STOPS OR TISSUE STOPS They are made by removing 4mm square or 2x4mm rectangle blocks of wax to expose the cast on the ridge region. Location: Located at canine and 1st molar teeth region as they have more periodontal surface area for wider distribution of forces. Purpose Purpose of of occlusal occlusal stops stops: : i. Prevent the tray from coming into intimate contact with the tissues. ii. Helps in proper orientation of the tray. iii.Helps in equal distribution of pressure
