Flashcards in dental material science Deck (21)
what determines the type of restorative material to be used?
shape of cavity
what holds an amalgam filling in place?
shape of cavity
what holds an composite filling in place?
what is amalgam creep?
deformation of amalgam due to constant stress
what technique is used to bond composite to the tooth?
acid etch technique
how is acid-etching carried out?
- 30% phosphoric acid is applied to tooth for 20 secs, this creates grooved surface
- after 20 secs etch is rinsed away
- bonding agent is then applied to tooth, this seeps into the grooves
- bonding agent is then cured using light, locking it onto the surface of the tooth
- composite can then be built up on the tooth
what does composite renin consist of?
mostly resin with small amounts of glass filler particles (composite)
what is the function of the glass filler particles (composite) in composite resin?
(resin-modified) glass ionomer cement is a type of composite, what are the benefits of this?
contains fluoride which increases enamel resistance to caries
what causes enamel and dentin to contract?
contraction of the restorative material may cause what?
microleakage as saliva and bacteria can ingress the tooth
what is the benefit of low viscosity impression material?
provides the most accurate record of tooth surface detail
what is the benefit of high viscosity impression material?
most dimensionally stable after setting and removing
how is low viscosity impression material applied?
placed around the individuals teeth then tray is inserted
how is high viscosity impression material applied?
placed in tray, tray inserted and patient bites
why do you never get a 100% accurate impression?
no impression material is fully elastic
what is viscosity?
ability to flow
what is elasticity?
ability to return to original shape on removal of applied force
what is rigidity?
measure of how much force is needed to cause temporary change in shape of material
what is compressive strength?
ability to withstand compressive forces without fracturing