Lab Course - Session 1 Flashcards
How are dentures classified in terms of support?
Mucosa borne
Tooth borne
Mixed
What is a mucosa borne RPD?
Made primarily from acrylic - relatively cheap
Metal components can be added for strength/ clasping
Easily modified
What is a tooth borne RPD?
Metal framework - teeth attached acrylic/composite
Support gained from rests
To be purely tooth borne - must be bounded saddles
Complex, time consuming, expensive
Can’t be modified
Need good OHI
What is a tooth/mucosa borne?
When no distal supporting teeth
Acrylic fitting surface = support saddle ares
Support gained from rests
Complex and expensive - challenging to provide adequate support and retention
Requirements of RPD?
Aesthetic Mastication Comfort Distribute occlusal forces appropriately Retention Maintain space and OVD
Advantages of RPD?
Aesthetic
Function
Tooth movement prevention
Maintain OVD
Disadvantages RPD?
Tooth loss greater > other methods
Increased plaque accumulation -caries/ gingivitis
Damage tooth tissue
Forces on teeth may impact on supporting structures
What is Kennedy classification?
Pattern of tooth loss
Class I - bilateral edentulous area posterior to remaining teeth
Class II - unilateral edentulous area posterior to remaining teeth
Class III - edentulous area between teeth
Class IV - edentulous area anterior to remaining teeth
What dental hx should you consider when assessing pt for RPD?
Is pt suitable? - perio condition etc
Does pt want/ need RPD?
Is RPD going to be destructive
Clinical need for further tx?
What should study model be used to assess?
- Edentulous area
- Undercut on remaining teeth
- Occlusion - study cast will need to be articulated
How is an RPD designed?
Something Really Complicated is Best Resolved in Many Stages
- Saddles
- Rest
- Clasp
- Indirect retention
- Bracing
- Reciprocation
- Major/minor connector
- Simplify
What is saddles?
The edentulous area -number and extent
Decide in denture tooth borne or tissue borne
What teeth need to be replaced - can reduce occlusal table?
What are rests?
Resist vertical force and transmit occlusal load down vertical axis of tooth
Cingulum or occlusal
What are clasps?
Provide mechanical retention and support
Resist displacement
Occlusally (L) or gingivally (T) approaching
Where should clasp engage?
Terminal 1/3 should engage within undercut - survey
What are indirect retention?
Clasps, rests, connectors
Resist rotation about clasp axis by acting on opposite site of displacing force
What is bracing?
Resist horizontal (lateral) forces
Rigid components
Clasp arm/ plates
What is reciprocation?
Clasps will always have sideways load during function - reciprocation opposes force
What are connectors?
Major link saddle areas - create rigidity
Minor - connect small component to major
Contribute to support, bracing, direct and indirect retention
Should finish 3mm away gingival margin or above survey line
How is support provided in mucosa borne denture?
Make acrylic footprint as large as possible
How is support provided in tooth borne denture?
By bounded saddles and occlusal rests - ensure loads transmitted
How is support provided to tooth/mucosa borne denture?
Free-ended saddles - position occlusal rest distal to saddle areas
- Load transmitted down long axis of tooth
What does model surveyor do?
Shows undercut area relative to path of displacement
How can path of insertion be used to create retention?
Path of insertion differs to path of displacement = resistant to displacement and therefore retention
Do this by blocking out undercut when making RPD
