Clinical Dental Sciences Flashcards
What shape of cavity is required for an amalgam restoration and why?
a large cavity that tappers out at the ends, amalgam doesnt bind to the tooth, requires mechanical strength to hold it in place
what shape of cavity is required for a composite resin restoration and why?
A smaller cavity, starts wide and tappers in at the bottom, the composite binds to the tooth so less mechanical strength required
Describe the acid etch technique
once cavity prepared, phosphoric acid is put on to the surface, a bond is then put on, composite resin is then used to fill the cavity, by binding to the bond
what is creep
when small, low level forces build up over time (eg biting), cause the amalgam to rise above the tooth surface, which can then be fractured
why is the thermal expansion of materials important
ideally want the same thermal expansion as the tooth, after exposure to cold, if the tooth and material expand at different rates, there will be a gap between allowing for microleakage, can result in secondary caries
how can impression materials differ
in viscosity
when are more viscous impression materials used
initially, to gain an overall impression, less likely to be distorted due to its rigidity
when are less viscous impression materials used
too gain more accuracy, can be put around specific areas and then the initial tray inserted to produce one impression with both materials
why do impression materials need to be elastic
for removing from the mouth, needs to be able to retain shape after
what must be considered when selecting a tray for impression taking
extend past the last standing tooth
cover all the sulci
not be in contact with buccal or lingual surfaces
how are impression trays disinfected
rinse under the cold tap, place in bath with disinfectant for 10 minutes, rinse under cold tap, place gauze on impression and place into a sealed bag
what is a high speed handpiece used for
removing carious enamel and preparing the cavity
why is water used with the high speed handpiece
due to the amount of heat produced, this cools it down
what burs are used with high speed handpiece
diamond shaped round or fissure bur - preparing and extending cavity
what is the slow speed handpiece used for
for increasing the depth of cavity, being careful not to extend into non-carious dentine
what bur is used with the slow speed handpiece
round bur
what is intercuspal position
when the mandibular teeth are maximally braced with the maxilla
what is the position of teeth relative to the opposing arch in ICP
mandibular buccal cusps lie in fossae of maxillary teeth, maxillary palatal cusps lie in fossae of mandibular teeth, lower incisal edge in contact with cingulum of upper
