Chapter 46 Flashcards
Three classifications of impressions
- Preliminary
- Final
- Occlusal (bite) registration
Five things preliminary impressions are used for
– Diagnostic models
– Custom trays
– Provisional coverage(temporary fixed bridge or crown)
– Orthodontic appliances
– Pre-treatment and post treatment records
Impression trays must be sufficiently rigid to:
– Carry the impression girl into the oral cavity
– Hold the material close to the teeth
– Avoid breaking during the removal of the impression
-Prevent wrapping the complete impression
The three ways Impression trays are supplied:
Quadrant tray – only covers one quadrant at a time
Sectional tray – only covers the anterior teeth
Full arch tray – covers the whole arch
Four things the correct size of the tray must accomplish:
– Comfortable for the patient
– Extend slightly beyond the facial services of the teeth
-Extends approximately 2-3 mm on the third molar, retromolar, or tuberosity area of the arch
-is sufficiently deep enough to allow the material 2-3 mm between the tray and the incisal or occlusal edges of the teeth
Two types of impression trays
Stock trays and custom trays
Three types of custom trays
- acrylic resin custom tray
- light cured resin custom tray
- thermoplastic custom tray
Three ways Alginate can be purchased
Containers, pre-measured packaging and Bulk
Water and powder ratios for impression material
ADULT: mandibular 2 water 2 powder
ADULT: maxillary 3 water 3 powder
CHILD: mandibular 2 water 2 powder or 1 water 1 powder
CHILD: maxillary 2 water 2 powder
ADULT XLARGE ARCH: mandibular 3 water 3 powder
ADULT XLARGE ARCH: maxillary 4 water 4 powder
Explaining the procedure to patient
Breathe through your nose No taste or smell Cold to the touch Raise hand if you need anything Take one to two minutes to set
Evaluating an Alginate impression
- impression should be centred
- complete “peripheral rolls” which includes the vestibular areas
- free of tear and voids
- Sharp anatomical portions of all teeth
- Retromolar pads and tuberosites are reproduced
- Hard palate is reproduced ( maxillary)
3 compartments of conditioning bath
- Liquefying
- storage
- Tempering
3 different forms of elastomeric materials
- Light bodied
- Regular bodied
- Heavy bodied
Elastomeric materials are supplied in 3 different ways
- Paste system (tube) base and catalyst
- Cartridge base and catalyst
- Putty ( containers)
A bite registration with an elastomeric material provides the lab tech and dentist the following benefits
- Material is fast setting
- Paste has no odour or taste to the patient
- gains dimensional stability over time
- Convenient to use
Tray set up
- Mirror
- Alginate
- water
- water measure
- mixing bowl
- spatulas
- impression tray
- utility wax
- Baggie
- paper towel
- mouthwash (Dixie cup)
- air/Wyler syringe
- saliva ejector
- Pts mirror
- PPEs
- Pts glasses
- bib
- bib clips
- chart
Impressions
Impressions are negative reproduction of those structures. Once an impression is poured with plaster or stone it becomes a positive.
Perforated stock trays
Most commonly used stock tray because the material has an opportunity to ooze out instead of going into the patients mouth
Final Impression are used for
Produce the most accurate reproduction of the patients teeth and surrounding tissues
Essential info needed to create indirect restoration such as fixed bridges, crowns, partials, full dentures and implants