Rest seats and guide planes Flashcards
What are rests named after?
where they are placed and ideally fit into prepared depressions called rest seatd
Cingulum
Incisal
Occlusal
what are the different rests?
Occlusal
Cingulum
Incisal
What are rest seats?
Prepared depressions
Where are cingulum rests usually placed?
On the palatal surface of canines
Avoid placing on lateral incisors
keep minimal
Where are incisal rests placed?
Prepared on the incisal surface of anteriors
Poor aesthetics
What should rest do/have?
Not interfere with opposing tooth/teeth
Normally be placed within a prepared depression to provide direct and indirect retention - the rest seat
Be placed onto horizontal tooth surfaces
Have rounded internal line angles
Transfer occlusal loads from the denture alon the long axis of the supporting tooth
What shape are occlusal rests?
Spoon/saucer shaped - no sharp line angles
What are occlusal rests made out of?
CoCr
What are the size of occlusal rests?
2mm mesio-distally
2mm bucco-lingually
How thick are occlusal rests?
1-1.5mm thick
Where are occlusal rests placed in the mouth?
Next to bounded saddles and away from free end saddles?
What is the role of guide planes?
limits the path of insertion Increases stability Provides reciprocation for clasps Prevents clasp deformation Improves appearance on anterior saddles May occur naturally
What different ways can guide planes be created?
Can be included in crown - wax pattern precision carved on a surveyor - trimming knife can be used to prepare guide planes on wax patterns
or prepared directly
What is the aim of surveying when creating a guide plane?
To plan the tilt of the case before construction so that the guiding planes of the teeth allow the saddle to be displaced in one path only
e.g. if the saddle of the denture fills the edentulous space exactly as a cube fits a box - there is only one path of displacement
Where are the guide planes placed?
2 or more parallel axial surfaces
