Elastomers Flashcards
what is an elastomer?
an elastomer is a polymer with viscoelasticity (both viscosity & elasticity)
what are the main components of elastomers?
- Polyether (base)
- addition silicones (extra fillers)
what are the ideal properties for impression materials?
- good quality of surface interaction between material & tooth/soft tissue surfaces
- Accuracy
- Dealing with removal & undercuts
- Dimensional stability
what are the ideal viscosity properties for imp materials?
must be able to flow readily
what are the ideal surface wetting properties for imp materials?
MUST make strong contact with teeth/mucosa
(high wettability)
what is the contact angle and whats its relevance?
lower contact angle = better wetting of tooth surface by impression material, more accurate and detailed capture.
Important in dentistry because capturing accurate details with impressions is the goal
what is the tear strength of a material?
the stress a material will withstand before fracturing
what is the rigidity of a material?
the stress (force) needed to cause material to change shape
how do you assess whether a dms material is good enough?
- if evidence shows new material is better = purchase
- if new material is only as good as current one = no specific advantage, just reject
- not enough evidence = review later
- if unconvincing data = reject
what are the key properties and their ideal values (High/Low) for impression materials?
Viscosity
Contact Angle
Wettability
Viscoelasticity
Stiffness
Thermal Expansion
Polymerisation shrinkage
Tear resistance
Viscosity = low (flow across surface)
Contact angle = low (engage with tooth surface)
Wettability = high
viscoelasticity = low (deformation on removal)
stiffness = low (ease of removal from undercuts)
thermal expansion = low (contraction mouth temp)
polymerisation shrinkage = low (contraction during setting)
tear resistance = High (ability to withstand large stresses)
