applied dental materials

Question 1

What is a composite?

Answer 1

•A composite is a combination of materials in which the individual components retain their identity and which possess different properties to the components acting alone.

Question 2

What does a dental resin composite consist of?

Answer 2

A dental resin composite consists of

–Resin

–Filler

–Most importantly a coupling agent

Question 3

What are fibre reinforeced materials?

Answer 3

• A type of composite
• Consist of

–fibres of high strength and modulus

–Embedded/bonded to a matrix

• Maintain a distinct boundary between the components
• Have properties that cannot be achieved with either the constituents acting alone

Question 4

What legal statement could patients require to see when dental apliance is being placed?

Answer 4

•Statement of Manufacture offered to all patients receiving dental appliance

–Patients name and confirmation made for them

–Prescribers name and registered address

–Technicians name and registered address

–Description of the appliance

–Confirmation meets legal standards

Question 5

What are teeth subjected to in the oral enviroment?

Answer 5

–Loading to 6 Kg

–On/Off cyclical forces – fatigue

–Chemicals

–Temperature fluctuations in microseconds

• Ice Cream -14 °C, Coffee 60 °C
• Teeth suspended in shock absorber

–The periodontal ligament

• Permitted vertical displacement 25 – 100 μm
• Permitted bucco lingual displacement 56 – 108 μm
• A force of 1N intrudes the tooth
• A force of 15N flexes the bone and causes pain
• pH fluctuations 2 – 12

Question 6

What materials are used by the dental team?

Answer 6

• Gypsum materials (plaster)
• Waxes
• Alloys
• Polymers
• Ceramics

Question 7

What is Cohesive failure and Adhesive failure?

Answer 7

Cohesive failure: one material fails as bond strength is greater than the strength of some material

Adhesive failure: bond failure between the adhesive and the adherend

Question 8

What is Thermal conductivity -D- ?

Answer 8

Thermal diffusivity – D – the rate that temperature will rise within a material when heat is applied to its surface

Question 9

What is thermal conductivity -K- ?

Answer 9

Thermal conductivity – K – rate of heat transfer through a material

Question 10

What does R_a stand for?

Answer 10

Ra - Arithmetic mean deviation of the surface profile

I.e tells us how rough surfafce is e.g.bumby line,

want it so be smooth e.g. straight line

Question 11

What is the mechanical Properties?

Answer 11

Dilatant – viscosity increases with applied pressure

Newtonian – viscosity remains constant with applied pressure

Pseudoplastic – viscosity decreases with applied pressure, and unless setting, increases when pressure decreases

Question 12

What are the Physical properties?

Answer 12

Physical properties

• Thermal expansion and contraction
  
  • Match as closely as possible tooth substance being replaced

Question 13

What are the chemical properties?

Answer 13

Chemical properties

• Corrosion
  
  • Defines the chemical reactivity of metals and alloys
  • An electrolytic property
  • Should display good corrosion resistance

Question 14

Boilogicaly what is the ideal material properties?

Answer 14

• non-toxic, non-irritant, harmless to the dental pulp, no carcinogenic potential or irritancy