TOPIC: IMPRESSION MAKING IN REMOVABLE PARTIAL DENTURE
🎯 KEY POINTS :
🔹Dual impression technique is usually indicated in distal extension cases.
🔹Fluid waxes can flow at mouth temperature and be firm at room temperature.
🔹Iowa wax was developed by Dr E.S. Smith.
🔹Zinc oxide eugenol paste is the material of choice for recording edentulous ridges without gross undercut.
🔍 DEFINITION:
👉 Altered Cast Partial Denture Impression: A negative likeness of a portion or portions of the edentulous denture-bearing areas made independent of and after the initial impression of the natural teeth. This technique employs an impression tray(s) attached to the removable dental prosthesis framework or its likeness. (GPT 8th Ed)
🔷 Factors Influencing The Support Of The Distal Extension Partial Dentures
🔺Type of soft tissue covering the edentulous ridge
🔺Type of alveolar bone constituting the denture-bearing area
🔺Type of alveolar bone constituting the denture-bearing area
🔺Design of the partial denture
🔺Magnitude of occlusal force
🔺Amount of tissue covering the denture base
🔺Nature of the denture-bearing area
🔺Fit of the denture base
🔷 Impression Methods Used For Distal Extension Removable Partial Denture
💡There are basically two types of dual impression techniques:
(i) The physiological or functional impression techniques
- McLean and Hindel’s method
- Functional relining method
- Fluid wax method
(ii) The selected pressure impression technique
🔷 Functional Impression Techniques Used In Distal Extension RPD
💡Types of functional impression techniques:
(i) McLean and Hindel’s physiological method
(ii) The functional relining method
(iii) The fluid wax method
✳️ Altered Cast: A final cast that is revised in part before processing a denture base also called corrected cast or modified cast. (GPT 8th Ed)
👉 The altered cast method is composed of the following three main steps:
🔹Step 1: Individual acrylic resin impression base is added to the lattice framework.
🔹Step 2: Final impression is made with zinc oxide eugenol paste, fluid wax or rubber base impression materials.
🔹Step 3: Altering the master cast.