7. Composition and preparation of condensation silicone impression material - putty form
Covers the composition of condensation silicone putty, a heavy-bodied C-silicone, with a table of its base and catalyst parts, including the polymer, filler content and cross-linker. Walks through the mixing steps by measured spoon, catalyst drops or paste, and kneading, with a note on not altering the dose, and explains how polycondensation and ethanol release cause shrinkage. Includes a table of working and setting times, shrinkage, elastic recovery, hardness and contact angle, and closes with its use in a two-phase impression.
Topic 7 of 52 in the MU Sofia syllabus for Dental Materials (Dental Medicine, Year 1). The free AceMed note covers it in 6 sections, about 192 words (2 min of reading), with 14 flashcards.
In this note
Introduction
Composition
Preparation
Setting
Properties
Use
Introduction
Condensation silicone putty (heavy-bodied C-silicone) is the thick form of this impression material. It gives bulk and strength, and it is usually combined with a thinner silicone in a two-phase impression.
Composition
The putty comes in a box, with a dosing spoon.
Preparation
Measure the putty with the supplied spoon.
Add the catalyst as the maker directs: a set number of drops, or a fixed length of paste.
Knead between the fingers for one minute, or mix with a wide spatula on a hard surface, in latex gloves.
Stop when the color is completely even, without going over the given time.
Place the putty in the impression tray.
The dose must not be changed. To gain working time, the packages can be cooled, without changing the amount of catalyst.
Setting
Mixing starts polycondensation. The chains cross-link and ethanol is released, which causes shrinkage. Because the filler does not shrink, the putty changes least of all the C-silicones.
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