Modification of Cavity Form for Different Materials Flashcards
What is the state of collagen in caries infected dentine?
Is it reversible?
- Denaturing of collagen
- Irreversible
What is the state of collagen in caries affected dentine?
Is it reversible?
- No denaturing of collagen
- Reversible
When removing caries what do you need to do to when dealing with enamel? (3)
- Gain access to caries
- Remove unsupported prisms
- Remove demineralised margins
When removing caries what do you need to do to when dealing with dentine? (3)
- Identify caries infected dentine (CID)
- Identify peripheral extent to EDJ
- Excavate CID peripherally then towards pulp and in depth
In removing caries when may you need to carry out further carious dentine removal? (5)
what could preclude a seal? (2)
- Poor quality peripheral enamel precluding seal
- Inadequate moisture control at margin precluding seal
- Symptoms of Pulpitis
- High caries risk
- Further structural support needed
What are some reasons for why we restore teeth?
- To remove diseased tissue
- To restore integrity of tooth structure
- To restore function of tooth
- To restore appearance of tooth
- To prevent recurrence of caries (microleakage)
- To provide durability and longevity
What are some factors that determine cavity design? (3)
- Structure and properties of dental tissues
- Extent and nature of dental disease
- Properties of proposed Restorative Material
How do you macroscopically modify a cavity?
Using your bur (hand piece)
How do you microscopically modify a cavity?
Chemically with tissue conditioning
Explain the concept of retention in cavity placement
The property of a cavity that resists displacement of a restoration in the direction of its insertion
Explain the concept of resistance in cavity placement
The property of a cavity that prevents displacement of a restoration in apical or oblique directions (other directions)
What is the Cavo-surface angle?
Angle between the cavity that’s been cut in the tooth and the surface of the tooth
What macroscopic modification of the cavity is carried out for all restorations?
Rounding of internal line angles
Why do internal line angles of a cavity need to be rounded?
Reduces internal stresses and risk of crack propagation within restoration
What additional 4 macroscopic modifications may you need to carry out for amalgam cavities?
Why would you need to do this?
- Cavity undercuts, grooves, slots, flat surfaces
- Undercut give retention
- Grooves/slots prevent displacement
- Flat surface improves resistance
What is the ideal Cavo-surface angle for amalgams?
90 degrees
What may occur if the Cavo-surface angle of a amalgam is greater than 90 degrees?
Amalgam near tooth surface may be too thin and crack
What may occur if the Cavo-surface angle of a amalgam is less than 90 degrees?
Enamel surrounding cavity may be unsupported and weak and enamel may fracture
What are some modification techniques that provide auxiliary retention? (5)
- Slots
- Grooves
- Coves
- Locks
- Dentine pins
What microscopic cavity modification do you need to perform for composites?
Enamel acid etch
What microscopic cavity modification do you need to perform for GIC?
Dentine conditioner
How does the enamel acid etch modification for composites benefit the tooth?
- Removes smear layer
- Selectively demineralises prisms giving it micro-mechanical retention
Why would you need to carry out an enamel margin bevel for composites? (3)
- Removes unsupported enamel
- Increases surface area
- Aesthetics
Explain GIC adhesion (3)
- On mixing free polyalkenoic acid penetrates enamel/dentine
- This displaces Ca2+ and PO4-
- These combine with cement matrix to form ion-enriched layer between tooth and cement that is rich in F-
