List 4 types of conventional cements
- Zinc oxide eugenol (eg temp bond)
- Zinc phosphate
- Zinc polycarboxylate
- Glass ionomer
Example of a resin based cement
Panavia
What is adhesion?
A molecular or atomic attraction between two contacting surfaces promoted by interfacial force of attraction between molecules or atoms of two different species
List 5 factors which affect adhesion
- Wetting
- Contact angle
- Surface energy
- Surface contamination
- Water
Wettability of a bond is influenced by (2)
- Cleaniness of the surface
- Surface energy
List 4 advantages of adhesive bonding
- Provide retention
- Increase strength
- Reduce microleakage
- Aesthetic
Why are primers needed?
They maintain the expanded collagen network, whilst removing residual water to allow for infiltration of the hydrophobic adhesive monomer
What primer is often used in bond
Hema-hydroxymethyl-methacrylate
It is both hydrophilic and hydrophobic so good intermediate.
What is bond made with usually?
Bis-GMA
3 primary goals of adhesive:
- Fill the interfibriallar space of the collagen network
- Provide a hybrid layer and resin tags
- Provide micromechanical retention once polymerized
What ingredient in bond prevents collagen collapse
HEMA.
It is the primer.
What ingredient in bond chemically bonds to the primer and the composite through MMA bonds
Bis-GMA
List 4 oral environmental factors that influence adhesion to tooth tissue
- Moisture
- Physical stress and chewing
- Changes in temp
- Changes in pH
List 2 prepared cavity related factor which affect adhesion to tooth tissue
- Surface contamination
- Saliva contamination
- Dentine quality
What is the ‘hybrid layer’
A mechanical interface between the tooth and adhesive
What are resin tags?
Adhesive resin which has locked into the microporosities of etched enamel and intertubular dentine, providing micromechanical bonding
List 6 requirements of a successful dentine bonding system
- Removal or dissolution of smear layer
- Maintenance of dentine collagen matrix
- Good wetting
- Efficient monomer diffusion and penetration
- Polymerisation with tooth structure
- Copolymerisation with composite resin matrix-
What is a cement
Substance that hardens from a viscous state to a solid union between two surfaces.
For luting applications, the maximum allowable film thickness is:
24 um
List 10 requirements of an ideal luting cement
- Biocompatible
- Good marginal seal
- Ressitant to saliva dissolution
- Physical properties as required
- Adequate working time and setting time
- Good aesthetics
- Good thermal and chemical resistance
- Radiopacity
- Low film thickness
- Retention - enhanced by adhesive bond between cement and restorative material
Whilst resin cements have greater strength and lower solubility than other cements such as zinc phosphate, polycarboxylate, the trade of is:
More technique sensitive
Why should light cure cements rather than dual cure be used for aesthetic restorations
More colour stable
Why might you want to use GI or RMGIC for cementing zirconia and metal restos compared with resin cement
Less post op sensitivity
