Surveying Flashcards
What is the purpose of surveying the casts?
To determine the optimum path of insertion
Identify undercuts that can be used for clasping
Identify unwanted undercuts to be blocked out
Which casts are surveyed?
Primary
Why is it ideal to have one POI?
Equalises retention on all abutments
Allows denture to be removed without interferences
What type of machine is a surveyor?
A parallelelometer
It allows vertical arm to be bought into contact with teeth and ridges
What are the components of a surveyor?
Analysing rod
Graphite marker
Undercut gauge
Trimming knife
What is the analysing rod?
Used to be placed against teeth in initial analysis to identity undercut areas and parallelism before marking
What does the marker do,
This is moved around the teeth along alveolar ridge and identify areas of maximum bulbosity
What is the undercut gauge ?
This measures the horizontal undercut depth
What is the trimming knife used for?
When wax is added to the undercut areas this knife is used to trim it back
Then need a duplicate all plaster cast
How do you survey?
Prelim assessment of study cast: eyeball by holding cast in hand and inspect from above and this enables you to gain an overall view of the tissues and decide whether or not to do a tilted surgery
Initial survey: place cast with occlusal plane horizontal and assess whether there is enough undercut in horizontal plane to be used for retention, use graphite marker to mark areas of undercut
Analysi: before marking permanently use the rod again to look at the position of the undercuts with the cast tilted
Final surgery: once tilted, change to a red marker, and mark these areas
What can happen with survey lines where teeth are to be tclasped?
Can often be that there are two surgery lines that intersect each other
How does tilting the cast AP affect the undercuts?
This will eliminate labial undercuts
How will tilting the cast laterally affect the undercuts?
Enough deoth for clasping
What is the desirable inclination for a maxillary cast?
Labial contour as a guide plan
Posterior border lower than anterior
What is the desrable contour for the lower cast?
Lingual surface as a guide plane to accommodate lingual bar
Align distal surface of abutments on free end saddle as guide planes
What should you record on the cast?
Record POI
Which surgery line should be marked first?
Upper
What is the purpose of the three armed clasp?
Active arm engages undercut terminal 1/3
Occlusal rest is for support and distributed loads through teeh
Reciprocal arm: prevents active arm displacing the tooth
How long do direct retainers need to be ?
Minimum of 1cm
What factors will affect clasp flexibility?
Material
Cross section
Clasp shape
Taper of clasp profile
He this the depth for the various material for clasps?
- 25mm CoCr
- 5mm SS and cast Gold
- 75mm Wrought Gold
What is the carbon marker held in?
Reinforcing sheath
