Crowns Flashcards
when should extra-coronal restorations be provided
when being used as a retainer for fixed bridge work
improve/ restore aesthetics
protect weakened tooth structure
what are the 6 principles of tooth preparation
preserve tooth structure
retention and resistance
structural durability
marginal integrity
preserve the periodontium
aesthetics
what occurs when tooth structure is not preserved
weakening the tooth
damage to pulp
what does under preparation of a tooth result in
poor aesthetics
over-built crown with periodontal and occlusal consequences
what does over preparation of the tooth result in
pulp and tooth strength compromised
what are the four factors involved in retention and resistance when preparing a tooth
taper
length of walls
extra means of retention (grooves/ slots)
path of insertion
why do you want long walls for a tooth preparation for a crown
prevents tipping displacement
what is the ideal inclination of opposing walls for a crown preparation
6 degrees
with reference to path of insertion, how is retention improved
limiting number of paths of insertion
how is structural durability of a tooth ensured when preparing for a crown
occlusal reduction
functional cusp bevel
axial reduction
what are the five finish line configurations that ensure marginal integrity
knife edge
bevel
chamfer
shoulder
bevelled shoulder
to preserve the periodontium of the tooth to be crowned, how should the margins of the restoration be
smooth and fully exposed to cleansing action
placed where dentist can finish them and patient can clean them
placed at gingival margin where possible
what is the axial reduction required for a metal crown
0.5mm
what is the occlusal reduction required on teeth prepped for metal crowns
1.5mm on functional cusps
0.5mm on non-functional cusps
what finish line should be used for a metal crown
chamfer - 0.5mm
what is the axial reduction for traditional porcelain ceramic crowns
1mm
what is the occlusal reduction on a tooth to be prepped for a traditional porcelain ceramic crown
1.5mm functional cusps
1mm non-functional cusps
what finish line should be used when prepping a tooth for a traditional porcelain ceramic crown
shoulder 1mm
what is the axial reduction required for MCCs
1.3mm
what is the occlusal reduction required for MCCs
1.8 - functional cusps
1.3mm - non-functional cusps
what finish line should be used when prepping a tooth for a MCC
chamfer 0.5mm where only metal is required
shoulder 1.3mm (0.4mm for metal and 0.9mm for porcelain)
what is the axial reduction required for all ceramic crowns
1.5mm
what is the occlusal reduction required for all ceramic crowns
2mm - functional cusps
1.5mm - non-functional cusps
what finish line should be used for an all ceramic crown
chamfer 1-1.5mm
