impressions Flashcards
What is an impression?
A negative imprint of an oral structure used to produce a positive replica of the structure.
What is an impression used for?
As a permanent record or in the production of a dental restoration or prosthesis.
How is an impression identified?
By the type of material used, such as “Alginate impression”.
What is a study model?
A positive, life-size production of the teeth and adjacent tissues.
How is a study model formed?
By pouring dental plaster or stone into an impression.
What is a study model used for?
It is used in the study of the patients oral condition in preparation for treatment planning and patient instruction.
What is a study model also known as?
A diagnostic cast.
Before taking an impression, what should you do?
Assemble the materials and equipment, then select and prepare the impression trays.
In what order to you take impressions?
The mandibular impression first, then the maxillary.
What must be done after the impressions have been taken?
An interocclusal record for occluding the casts should be taken.
What 6 things must you do when preparing the patient?
- Review the patients medical and dental history
- Explain the procedure
- Position the patient
- Remove any appliances
- Examine the oral cavity
- Remove any debris
Name the 7 items of materials and equipment to collect.
Alginate Trays Fix Wax Disinfectant Plastic bag Lab card
What is alginate impression material?
An irreversible hydrocolloid.
What are the chemical constituents?
Carboxylated polysaccharide based on alginic acid, sodium alginate, calcium phosphate, sodium phosphate (retarder).
Fillers - eg. Zinc carbonate
pH indicators that change colour, pH drops as it gels.
How does the impression material gel?
It gels by cross-linking formation with calcium ions.
