Crowns/onlays Flashcards
what is an inlay
an indirect intra-coronal restoration that does not provide cuspal coverage, proximal and occlusal surfaces are replaced
what are the preparation principles of an inlay
isthmus 1.5-2mm, flat pulpal floor, 4-6 degree tapered walls, no undercuts, contact points clear, rounded internal line angles, ceramic: butt-joint (90 degrees) cavosurface angle, metal: 20-30 degree bevel on cavosurface margins
what are the indications of inlays
occlusal and/or proximal cavities, failed direct restoration replacement
what are onlays
an indirect intra and extra coronal restoration that incorporates cusps and provides cuspal coverage
what are the preparation principles of onlays
isthmus - follow restoration pattern, flat pulpal floor, 4-6 degree tapered walls, no undercuts, 90 degree cavosurface margins, contact points clear, rounded internal lines angles, axial shoulder or chamfer 1mm reduction, ceramic: functional cusp 2mm reduction, non-functional cusp 1.5mm reduction, gold type III: functional cusp 1mm reduction, non-functional cusp 0.5mm reduction
what are the indications of onlays
cusp fracture, toothwear, caries weakening the tooth structure, pre-exisiting failed restoration with a large isthmus, restoration of root treated teeth
what are crowns
an indirect restoration that fully covers the coronal aspect of a tooth
what are the preparation principles of crowns
flat pulpal floor, 4-6 degree tapered walls, no undercuts, rounded line angles,
ceramic: functional cusp 2mm reduction, non-functional cusp 1.5mm reduction, PFM: buccal 1.5mm shoulder, porcelain palatal/lingual 1.5mm shoulder, all ceramic 1mm rounded chamfer
gold type III: functional cusp 1mm reduction, non-functional cusp 0.5mm reduction, palatal/lingual 1mm chamfer
what are the indications of crowns
cusp fracture, toothwear, caries weakening the tooth structure, pre-exisiting failed restoration with a large isthmus, restoration of root treated teeth, high aesthetic demand, onlay not possible
what are the three planes that anterior teeth are prepared for during crown prep
cervical third, middle third, incisal third
what are the different materials used to make temporary crowns
bis-acryl composite or poly-n-butyl methacrylate
when is a double cord method preferred over a single cord method
for thick gingival biotypes
what is the one stage impression technique
syringe light body silicone or medium body polyether around the preparation, into the gingival crevice and across all the occlusal surfaces on the same arch, take the impression with a medium/heavy body silicone or medium body polyether
what is the two stage impression technique
prior to starting preparation use a heavy body silicone with a plastic separator to take an impression of the arch, proceed with prep, syringe light body silicone around the prep and into the gingival crevice and into the heavy body impression taken before and seat the tray
what are the advantages of immediate dentine sealing
- less bacteria leakage/contamination of dentine during temporisation
- reduced post-operative sensitivity due to less polymerisation shrinkage
- increased bond strengths as bonding to fresh cut dentine
- better fitting restorations as uniform bonding surface
