Extensive Amalgam Restorations Flashcards
3 reasons to restore cavities
- restore integrity of tooth surface
- restore function of tooth
- restore aesthetics of tooth
what method of retention does amalgam use
macromechanical
define retention and resistance
retention: ability to withstand forces in long axis of tooth
resistance: ablility to withstand dislodgement in all other directions
what is meant by auxillary retention?
other aids used to aid retention
3 methods of auxillary retention used in EARs
- cavity design features
- pins
- adhesives
4 elements of cavity design which offer additional resistance form
BAPS: Boxes Axial grooves Pits Slots
maximum size of slots and pits
depth no greater than 1mm
width little more than instrument used to prepare them
name a disadvantage of slots and pits
sharp internal form –> increases stresses within tooth and material but necessary to provide resistance form
3 types of pins
- cemented
- friction grip
- self-threading
which type of pin is the most retentive and most common?
self-threading pins
how many pins should be used per
a) missing cusp
b) missing line angle
c) missing proximal surface
1 for each
measurements for placement of self-threading pins
1-2mm inside DEJ/CDJ
2mm in to dentine, amalgam
2mm from opposing tooth
why should pins be used with caution?
weaken tooth and restoration
what are EARs used instead of?
cast restorations (crowns, inlays, onlays etc)
2 possible outcomes of incorrectly placed pins
- insert in to pulp –> pulpitis, post-op sensitivity
- insert in to periodontal tissues –> post-op sensitivity
2 adhesives used with pins in EAR
4META (AmalgamBond)
MDP (methacryloyloxydecyl dihydrogen phosphate, Panavia)
advantages of adhesives
-conserve tooth structure
-increase retention
BUT no evidence that it increases survival
2 ways restorations fail
- new disease (secondary/recurrent caries, pulpal problems)
- technical failure
4 possible routes to technical failure of EARs
- defective contact points
- overhanging restoration
- non-retentive (falls out)
- fractured restoration
outcome of technical failure of EAR
secondary caries, periodontal disease
is repair of replacement of EAR preferable and why
repair: conservative, quicker, cheaper, less traumatic, poss no LA
not replacement: inadvertent removal of tooth tissue, increase in cavity size, pulp damage, development of clinical symtoms
BUT depends on clinician, circumstance, pt preference
