Prosthodontics Flashcards
What saddle determines the Kennedy class?
The most posterior
Define Kennedy Class I
Bilateral free end saddles
Define Kennedy Class II
Unilateral free end saddle
Define Kennedy Class III
Unilateral bounded saddle
Define Kennedy Class IIII
Anterior bounded saddle across the midline
What can Kennedy class IIII arches not have?
Modifications
What are modifications in arches?
Additional saddle areas (more than 1 saddle in an arch)
Most posterior saddle defines the Kennedy class.
Then do not count the saddle used to classify the arch in the modifications.
Define denture support.
Describes the resistance of a denture to occlusally directed load
Define Craddock classifications?
Tell you which type of support is used in the denture
Define Craddock Class 1.
Tooth borne support - forces directed through the PDL of the adjacent teeth
Define Craddock Class 2.
mucosa borne support
Large area is required to prevent resorption of the alveolar bone. (resorption occurs when large forces are applied over smaller areas)
Define Craddock Class 3.
Tooth and mucosa borne support
What is advised when placing a mucosally supported denture (class 2 or 3)
That the base is > 3mm from the gingival margin.
since mucosal tissues can compress
What is the preferred option for support?
Tooth support
What are the advantages of a tooth supported denture?
Gives patient a more natural feel since the load is directed down the PDL of the adjacent teeth. PDL contains mechnoreceptors whihc can gauge forces and texture.
More comfortable
Likely to stay in close contact with the supporting structures.
What are the disadvantages of a mucosally supported denture?
Have to cover a large area - reduces the occlusal table. (reduces natural sensation)
Can cause damage to the adjacent gingival margins
List the best teeth for support.
Best to worse;
Molars, canines, premolars and anteriors
What denture components provide support?
Rests
What kinds of rests are there?
Cingulum, incisal and occlusal
Where can cingula rests be used?
On canines and typically upper anteriors (cingulum more pronounced)
What are the disadvantages of incisal rests?
Interfere with occlusion
Not aesthetically pleasing
If there is a heavy contact with an opposing tooth, can an occlusal rest be used?
Yes if a rest seat is cut into the enamel.
How deep should a rest seat be?
Between 1mm - 2mm
What can happen if an occlusal rest is too small?
Can cause torking
Compromises the supporting tooth - could tilt.
What is retention?
Resistance of the denture to vertical dislodging forces
What are the two types of retention?
Direct
Indirect
What is indirect retention?
Resistance to rotational displacement.
How is direct retention achieved?
Mechanical means - i.e. engaging undercuts.
Muscular mean - the action of the patients musculature on the denture
Physical means - i.e. adhesion, cohesion, atmospheric pressure.
What is the main form of retention?
Mechanical - Clasps engaging undercuts
Where should the terminal end of a clasp be situated?
In the undercut you want to engage.
Usually;
Lingual aspect engaged - lower
Buccal aspect engaged - upper
What are the types of clasps?
Occlusally approaching
Subdivides into occlusally approaching self reciprocating.
Gingivally approaching
When are occlusally approaching clasps used?
In molars
When are gingivally approaching clasps used?
Canines
Premolars
How many clasps do you need in an arch?
1 on each side
However 3 is ideal to create the triangle of retention.
What is the function of reciprocation in a denture?
It prevents continuous horizontal pressure of a tooth used for retention (clasped tooth)
If there was no reciprocation the tooth would move.
What are the components of an RPI?
Mesial rest
Proximal plate
Gingivally approaching i-bar clasp
When are RPIs typically used?
In mandibular free-end saddles
What components can be used as indirect retainers?
Rests
Major connector/base
Minor connector
Is a clasp required on every abutment tooth with a rest?
NO
What is the function of minor Connectors?
Unite components of the denture, i.e. rests, to the major connector.
What should be avoided when adding minor connectors and why?
Creating lots of windows.
Acts as a food/plaque trap
What is the function of a major connector?
Joins components of one side of the arch to the other side of the arch.
List examples of major connectors used in the lower arch.
Lingual bar
Lingual plate
List examples of major connectors used in the upper arch.
Anterior posterior bar (ring design)
Mid palatal strap
Horseshoe bar
List the guidelines for a successful major connector.
Avoid coverage of the gingival margins - can cause dragging and irritation.
Cover as little tissue as possible - keep natural sensation for the patient
Have as little edges as possible - uncomfortable for the patients tongue.
What are the additional functions of a major connector?
Can extend on to the surfaces of teeth to act as indirect retention (prevent rotational displacement)
Can extend on to the surface of teeth to act as reciprocation - useful when there is limited crown height/ no significant undercuts
What are the advantages of using a plate (major) connector ?
Thinner
Usually less edges
What are the disadvantages of a plate (major) connector?
May cover gingival margins
Coves mucosa - patient loses natural sensation.
What is the MINIMUM casting thickness of a plate connector?
0.45/0.5mm
What is an advantage of using a bar (major) connector?
Less mucosal coverage - patient maintains natural sensation.
What are the disadvantages of using a bar (major) connector?
Thicker
More edges for the tongue to explore = uncomfortable.
How much space is required for a lingual bar?
8mm from the gingival margin to the functional floor of the mouth.
4mm for the bar
3mm from the gingival margin
1mm from the functional floor of the mouth
What are the advantage of an open denture design?
Best option for oral health - clearing can occur.
Reduced gingival coverage = Less irritation to tissue
When are occlusally approaching self reciprocating clasps used?
In lone standing molars
If there is a limited length between the undercut and the rest (go the other way around the tooth to achieve 15mm length)
