Where is alginate used?
Alginate sets in 1–2 minutes and accurately conveys the shape of the teeth, but is unstable during storage: a model is cast on it within an hour. Therefore, it is used where submicron precision is not needed - for diagnostic models, the manufacture of mouth guards, retainers, temporary crowns and as an auxiliary impression of the opposite jaw.
Why are the stages counted separately?
Orthopedic treatment consists of clinical and laboratory stages. Some of them - taking impressions, making an individual tray, gum retraction, fixing or removing a crown - are performed independently and are not always included in the main work.
The result directly depends on the quality of these stages: an inaccurate impression or an under-opened edge of the ledge will lead to the fact that the crown will not fit, no matter how well it is made in the laboratory.
What affects accuracy
- selection of impression material for a specific task
- dry field and lack of blood in the ledge area
- correctly opened gingival sulcus
- no deformation of the impression during removal