Properties of a Lining Material Flashcards
What materials are placed in tooth cavities
Composite resin Glass ionomer Amalgam Precious metal Ceramic
What are the disadvantages of restorative
They may not make intimate contact with the tooth surface allowing ingress of fluids and bacteria
Heat released during setting/curing
Release of chemicals that may be pulp all irritants and lead to pain or pulpal damage
How can microleakage be prevented
By using a lining material to prevent gaps and act as a protective barrier
Describe a cavity base
Thick mix placed in bulk
Dentine replacement used to minimise the bulk of the material or block out undercuts
More common in metal restorations
Describe a cavity lining
Thin coating (<0.5mm) over exposed dentine
What is the purpose of a liner in pulpal protection
To protect the pulp from:
Chemical stimuli from unreacted chemicals in the filling material or the initial high pH of the filling
Thermal stimuli such as the exothermic setting reaction of composite or heat conducted through metal fillings
Bacteria and endotoxins through microleakage
What are the other purposes of a liner
Therapeutic - to calm down inflammation within the pulp and promote pulpal healing
Palliative - to reduce patient symptoms prior to definitive treatment being carried out - most common in patients with reversible pulpitis
What are the different types of properties of a lining material (9)
Ease of use Thermal properties Mechanical properties Radiopaque Marginal seal Solubility Cariostatic Biocompatible Compatible with restorative materials
What is the desirable ease of use of a lining material
Easy to mix
Working time should be long to allow easy placement
Setting time short - ideally command set
What are the desirable thermal properties of lining materials
Low thermal conductivity
Thermal expansion coefficient similar to dentine
Thermal diffuse its similar or lower to dentine
What is thermal conductivity and what are its units
How well heat energy is transferred through a material
Units are W/m-1/*C
What is the thermal expansion coefficient and what are its units
Change in length per unit length for a temperature rise of 1C
Units are ppmC-1
What is the desirable thermal expansion for a lining material and give some examples for
Ideally a liner should match the thermal expansion coefficient of tooth Enamel - 8.3ppm*C-1 Dentine - 11.4ppm*C-1 GIC - 11ppm*C-1 RMGIC - 20ppm*C-1 Composite - 25ppm*C-1 Amalgam - 25ppm*C-1
What are the desirable mechanical properties of lining materials
High compressive strength to allow placement of filling without it breaking
Modulus similar to dentine so that as the tooth bends. And flexes, the lining material will bend and flex with the tooth
Why should a lining material be radiopaque
So it is easy to see the difference between the lining material and the tooth
This makes it easier to see if there is any leakage or secondary caries
