Modification of Cavity Form for Different Materials Flashcards
Describe caries infected dentine
- Deminerlisation of dentine
- Denaturing of collagen
- Irreversible
Describe caries affected dentine
- Demineralisation of dentine
- No denaturing of collagen
- Reversible
What are the aims when removing enamel as you try to remove caries
- Gain/widen access to caries
- Remove unsupported prisms
- Remove demineralised margins
What are the aims when removing dentine as you try to remove caries
- Identify caries infected dentine
- Identify peripheral extent to EDJ
- Excavate CID peripherally then towards pulp (anatomical)
- Excavate CID in depth (histological)
After Caries infected dentine has been removed what is the next step in caries removal
Considering whether more carious dentine removal is necessary
If you do want to remove more carious dentine what reasons might there be to do so
- Poor quality peripheral enamel precluding seal
- Inadequate moisture control at margin precluding seal (e.g. at gingival margin)
- Symptoms of pulpitis
- High caries risk
- Further structural support needed
- CONSIDER DIRECT/INDIRECT PULP CAPPING
Give examples of ways that we can carry out cavity modification
- Rounded internal line angles
- Increase surface area of enamel margins (bevel)
- Chemical modification of cavity walls (acid etch/conditioners)
What reasons might you have to not remove any further dentine after CID removal
- Remaining CAD retained
- Good quality/quantity of peripheral enamel
- Good moisture control at cavity margin
- Further excavation may make tooth unrestorable
Why should 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 factors determine cavity design
- Structure and properties of dental tissues
- Extent and nature of dental diseases
- Properties of proposed restorative material
What can we do to modify a cavity on a macroscopic level
- Created using a bur
- Air rotor for slow handpieve
What can we do to modify a cavity on a microscopic level
- Created chemically
- Tissue conditioning
What is retention
The property of a cavity/restoration that resists displacement of a restoration in the direction of its insertion
What is resistance
The property of a cavity/preparation that prevents displacement of a restoration in apical or oblique directions (other directions)
What is the cavo-surface angle
This is the angle between the internal surface of the cavity of the tooth and the surface of the tooth
What is a line angle
This is the angle between 2 surfaces
What is an internal point angle
This is where 3 sides meet
What kinds of external walls can there be in a cavity
Distal
Facial
What kinds of internal walls can there be in a cavity
Pulpal
Axial
What are direct and indirect restorations
Direct - placed directly into the tooth
Indirect - Placed, but made or fabricated in an external lab
What are the basic properties/features of direct restorations
- Plastic
- Mouldable
- Various physical properties
- Complex restorations
AY BAWS CAN I HABE DE NOTE PLZ
Made in lab and cemented/luted chairside
Why do you want rounded internal line angles for all restorative materials
Reduces internal stresses and risk of crack propagation within restoration
What cavity mods are ideal for amalgam restorations
- Cavity undercuts
- Grooves
- Slots
- Flat surfaces
What do undercuts, grooves/slots and flat surfaces allow in amalgam restorations
Undercuts = give retention
Grooves/slots = Prevent further displacement
Flat surface = improves resistance
What cavity modifications are ideal for composite/GICs
Enamel margin bevel
What does the enamel margin bevel allow for in composite/GICs restorations
- Removes unsupported enamel
- Increases surface for bond/seal
- Sound enamel for optimised bonding
What micro cavity mod is ideal for composite restorations
Enamel acid etch
what does the enamel acid etch do for composite restorations
- Removes the smear layer
- Selectively demineralises prisms giving micro-mechanical retention
What micro cavity mods are ideal for GIC restorations
Dentine conditioner
What does dentine conditioner allow for GIC restorations
- Removes smear layer
- Prepares surface for Ca2+ chemical adhesion
Name some of the basic properties of an amalgam restoration
- High strength (2mm+)
- Electrochemical corrosion = nice marginal seal
- High elastic modulus
- Dimensionally stable
- No inherent bonding to tooth substrate
What angle should the cavo-surface angle be for an ideal amalgam restoration
about 90 degrees
What are some examples of auxillary retention cavity mods for amalgam and dat when there aren’t alot of cusps left to form the undercuts and all
- Slots
- Grooves
- Coves
- Locks
AY BAWS CAN I HABE DE NOTE PLZ
The amalgam slots need to be undercut as well to provide retention as well as resistance
Do coves offer resistance and/or retention
Offers both in almost all directions
What are locks
grooves cut in a vertical direction
Name some basic properties/characteristics of composite restorations
- Good aesthetics
- Bonds to dental substrates
- More conservative tooth preparation
- No corrosion
- Slightly less durable than amalgam
- Lower modulus of elasticity
- Technique sensitive
What macroscopic cavity mods might you need for composite restorations
(undercuts, slots and grooves, cavosurface angle, flat surface)
ENAMEL MARGIN BEVEL
What microscopic cavity mods might you need for composite restorations
- 37% orthophosphoric acid etch + prime/bond
- Removes smear layer in dentine
- Selectively demineralises enamel prisms
- Creates micromechanical undercuts for resin to engage
- Creates one of the strongest bonds in dentistry
What is the purpose of doing the enamel margin bevel for composite cavities
- Removes unsupported enamel
- Increases surface area
- Aesthetics
What does etching do to the enamel in composite cavity mods
Selectively demineralising some enamel prisms that creates a very rough microscopic surface that allow the composite to bond better
What is a hybrid layer of dentine in the composite cavity mods and how is it made
- Demineralised resin-impregnated dentine
- Etching removes smear layer
- Demineralises intertubular dentine, exposing collagen
- Demineralises intratubular dentine
- Allows resin to flow into the tubules
Is the composite-dentine or the composite-enamel layer stronger
Composite-enamel is deffo stronger but the dentine one is still strong
What is the sequence of processes that occur in composite cavity mods
- Acid etch
- Primer
- Bonding
So describe the process of acid etching in composite cavity mods
- Phosphoric acid (37%)
- Demineralises prisms and = rough surface in enamel
- Removes smear layer in dentine and demineralises intertubular dentine and makes collagen scaffold
- Micromechanical mods
Describe the process of priming
- EDTA/Acid based
- Further conditions dentine
- Optimises surface for bonding
What are some of the properties of GICs as a restorative material
- Lower fracture strength vs composite and amalgam
- Less tough (prone to wear)
- Poorer aesthetics
- Inherent (chemical) bond to dental substrates
- Fluoride release
What does a dentine conditioner do for GIC fillings
Removes smear layer and optimises dentin for ion exchange to allow for chemical bonding of GIC
AY BAWS CAN I HABE DE NOTE PLZ
10% polyacrylic/citric acids
Describe how GICs adhere to a tooth
- Ions exchanged between tooth minerals and cement
- On mixing, free polyalkenoic acid penetrates enamel/dentine
- Displaces Ca2+ and PO4-
- Combine with cement matrix to form ion-enriched layer between tooth and cement
- Rich in F-
