The alginate impression material cannot be used as muco-compressive material. This material does not have consistency enough to apply pressure on mucosa. Therefore, muco-compressive impressions cannot be taken by alginate.
The muco-compressive impression can only be taken by impression compound or heavy duty (putty) rubber base impression materials as they both have thick consistency.
What is a muco-compressive impression?
A Muco-compressive impression of the mouth is an impression that takes the negative replica of mucosa in a compressed state. This impression is poured by a plaster of Paris mix to make the primary cast (die). From this cast, a special tray is made to make an impression that contains records of the mucosa of load bearing area in a compressed state. Rest of the area of the impression contains the records of the mucosa that are not under pressure.
This impression technique is used to enable the transfer of masticatory force (chewing force) to the area of the oral mucosa that can bear the load and the non-load bearing area can be spared.
The areas that can bear the masticatory load are divided into two types: They are
- Primary stress bearing areas
- Secondary stress bearing areas
Primary supporting areas
They are the main load bearers. They are
- Hard palate
- Posterior-lateral slopes of residual ridge
Secondary stress bearing areas
They bear less load. They are
- Residual ridge
- Rugae area
- Maxillary tuberosity
The area that cannot bear load, and if overloaded, can dislodge the denture or become sore. They area
- Incisive papilla
- Median palatine raphe
- Torus palatinus
- Sharp spiny processes
- Cuspid eminence
- Zygomatic process
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