27. Comparative characteristics of silicone impression materials
Compares condensation (C-silicone) and addition (A-silicone) impression materials, starting with how they set and the by-product each releases. A table sets out their polymers, catalysts, mixing, working and setting times, contact angles, field conditions and pouring, followed by shrinkage figures shown in a bar chart. It then contrasts putty and light-bodied consistencies, offers guidance on choosing between the two families, and closes with properties they share.
Topic 27 of 52 in the MU Sofia syllabus for Dental Materials (Dental Medicine, Year 1). The free AceMed note covers it in 6 sections, about 135 words (2 min of reading), with 14 flashcards.
In this note
Introduction
C-silicones against A-silicones
Shrinkage
Which consistency does what
Choosing between them
Shared properties
Introduction
The two silicone families differ in how they set, and this explains nearly every other difference between them. Condensation silicones release a by-product, and addition silicones do not.
Shrinkage
Fillers limit shrinkage in both families, so the thick forms shrink least. A two-phase impression with C-silicone shrinks by about 0.3%. A-silicones have the lowest shrinkage of all impression materials.
Choosing between them
C-silicone suits everyday work where cost matters and the model can be poured quickly.
A-silicone suits precise work, because it is the most accurate and most stable, but it costs more, has a shorter shelf life, and needs care to avoid contamination.
Shared properties
All silicones keep their shape in storage, tolerate disinfecting solutions, resist tearing, and can be poured more than once. Neither family sticks to trays by itself, so trays are perforated, taped or coated with adhesive.
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