Impression Flashcards
What’s the acceptable impression ?
- An exact record of all aspects of the prepared tooth
2.Include sufficient unprepared tooth structure
adjacent to the margins
3.Dentist and laboratory technician must identify
the contour Of the tooth and all prepared surfaces
What’s the crucial informations from the impression ?
- The contour of the unprepared tooth structure cervical to the preparation margin
2.Line, where tooth and future restoration meet
3.Fabricating the restoration with proper contours must be possible
What will happen if we take impression in moist enivoroment ?
Void.
What’s retraction methods ?
- Mechanical displacement -placement of a cord and paste systems
2.Chemical - as aluminum sulfate or epinephrine
3.Surgical - through curettage, excision with a scalpel, or electrosurgery
Why we do gingival retraction ?
**Enlarging the gingival sulcus through mechanical, chemical, or surgical means
**Improper manipulation of impression material and poor tissue displacement technique - permanent soft tissue damage
What’s cord placement steps ?
- Best to start in the interproximal area
- The instrument should be angled toward the tooth
- A second instrument may aid placement
4.Tissue must be displaced gently - the cord just apical to the margin
How to evaluate the impression from occlusal aspect ?
- The entire preparation margin should be clearly visible and remain directly accessible for about a minute
- The uninterrupted cord, with no soft tissue folded over it should be seen
What should we see on impression tray ?
- Clear finish line
- Gingival contour
- Clear neighboring teeth ( to adjust contact point )
- Good soft and hard tissue appearance
- No pressure areas ( uniform thickness ) espicially on finish line
- Homogeneous mix appearance ( to avoid shrinkage that lead to inaccurate result )
- No voids of bubbles espicially on finish line
- Free of debris or food
Which factors affect the impression ?
- Tray selection
- Tissue management
- Impression material selection
- Impression mixing
- Impression technique
- Well performance of the steps
- Impression taking for both arches and bite registration
Which surgical procedure for soft tissue management ?
Gigivectomy by laser removal some part of sulcus
In which situations of supragingival finish line we do retraction ?
To show the gingival sulcus = emergence profile
The contour of the tooth or restoration as it emerges from the gingival
What’s. The double cord technique ?
Insertion 2 cords into sulcus depth
1. Small cord , #0 , #00 , #000 which will decrease bleeding , cervical fluid , remove of remains impression material when taken out .
- Large cord #1,2,3 inserted above the 1st one
In what 1st cord serve ?
1.Can be used during finish line preparation to decrease fluid and bleeding.
- During second cord removal keep it to maintain long time gingival elevation to prevent reattachment.
- For good retraction placed it and after 5 minutes place the second one
- Remove it after complete impression
How to deal with second retraction cord ?
- More movable gingiva or for posterior use large cold
- 5 sec after first
- Remove before light injection
- 30 sec after removal the gingiva reattach
What should be the field wishlist insertion and removal the cord ?
- Should be inserted on dry filed more easy
- Remove on wet to avoid gingival ulceration
What’s astringent reataraction paste ?
Paste that placed in the sulcus to retract and hemostasis.
Can replace the double cord or over the first cord as second
How to deal with impression material ?
- The manufacturer’s recommendation time should be followed!!!
- Maximum working and minimum setting time
- Difficult to judge clinically
- Any delay in seating the tray results in a distorted impression
- Premature impression removal is a common cause of impression distortions
What’s Alginate uses ?
diagnostic and preliminary purpose
What should we consider while taking alginate impression ?
- The thickness of the alginate impression between the tray and the tissues should be at least 3 mm
- The compressive strength of alginate doubles during the first 4 min after gelation
- Most alginate materials improve in elasticity over time
How the water and overmixing affect alginate consistency ?
- If too much or too little water is used in mixing, the final gel will be weakened, making it less elastic
2.Overmixing breaks up the formation of the calcium alginate network and reduces its strength
What’s preliminary impression ?
Diagnostic casts are made from preliminary impressions
Are often very accurate representations of the hard and soft tissues of the ridges
With poor detail of the depth and width of the vestibules and surrounding muscular attachments
**Stock impression trays are used (lack the accuracy)
Which material used for preliminary impression ?
Irreversible hydro-colloids are the materials of choice (Alginate)
These materials will often displace the soft tissues of the vestibules, resulting in an overextended impression and resulting cast
What’s costume trays used for ?
For each patient individually, through the use of diagnostic casts
Improves the accuracy of an elastomeric impression
Custom (Final) Impression Trays uses ?
The goal is to make as exact a replica of the soft and hard tissues as possible
Maximum coverage of supporting tissues and minimal extension onto movable tissues and muscle attachments
How to evaluate impression ?
The impression must be inspected for accuracy when it is removed
If bubbles or voids appear in the margin, the impression must be discarded
An intact, uninterrupted cuff of impression material should be present beyond every margin
Streaks of base or catalyst material indicate improper mixing and may render an impression useless
