Setting Expansion
The dimensional increase that occurs in a dental material as it transitions from a plastic to a rigid set state, commonly measured in investment and gypsum materials.
Full Definition
Setting expansion refers to the slight volumetric or linear increase that some dental materials — particularly gypsum products and phosphate-bonded investment materials — undergo during the chemical setting reaction. In dental casting, controlled setting expansion is desirable to compensate for the thermal shrinkage of the metal alloy during solidification. There are two components commonly distinguished in investment materials: normal setting expansion and hygroscopic setting expansion (the latter occurring when the material sets in contact with water). Editors should be alert to authors conflating 'setting expansion' with 'thermal expansion,' as these are mechanistically and clinically distinct phenomena.
Usage
Usage note: Always specify whether reported values are for normal or hygroscopic setting expansion. Conflation with thermal expansion is a common author error requiring editorial query.
In Context
- "The authors reported setting expansion values for the investment material but failed to specify whether normal or hygroscopic expansion was measured." — Research article methodology review
- "Setting expansion must be distinguished from thermal expansion in casting investment manuscripts, as each is measured and utilised differently." — Editorial annotation for dental materials journal