Posts Flashcards
what is a post
peg or pin for fastening artificial crown or core to a natural tooth root
(required if 3 or 4 preparation walls lost )
what is a ferrule
ring of remaining coronal dentine after tooth preparation that protects against root fracture
ideally 2-3mm, minimum 1.5mm
optimum dimensions of a post
- length and width
as long as possible whilst leaving 4-5mm apical GP (at least 1/2 to 2/3 root length)
no more than 1/3 diameter of root
increasing what dimension of a post increases retention
increasing length
increasing diameter does NOT increase retention
what are the different post types (4 categories)
- metallic or non metallic
- parallel or tapered
- pre fabricated or custom made
- smooth, serated or threaded
pros and cons of cast metal posts
pros: conserve tooth tissue, custom made so follows canal shape, useful in flared canals
disadvantages: room for error as lab and extra clinical stages
pros and cons of fibre posts
pros: tooth coloured so good aesthetics, can be placed immediately, elastic modulus similar to tooth, compatible with adhesives
cons: difficult retrieval
pros and cons of tapered posts
pros: max remaining coronal dentine
cons: wedging effect
pros and cons of parallel posts
pros: uniform stress distribution along length, more retentive and resistant to dislodging
cons: more dentine removal
smooth vs serated vs threaded
smooth - less stress generated but minimum retention
serated - increases SA for retention but less stress generated
Threaded - very retentive but high stress and creation of fracture lines
discuss the ideal post
- 5mm apical GP
- 3mm ferrule
- 1/3 root diameter width
- parallel sided (avoid wedging forces)
- non threaded (avoid installation stresses that would later be relieved by root fracture)
- cement retained (distribute masticatory forces evenly)
3 options for cement for posts
resin
GIC
RMGIC
what cement would be used for fibre posts
dualcure composite resin
self adhesive composite resin
what cement would be used for metal posts
zinc phosphate
GIC
RMGIC
dualcure composite resin
