Endodontics Flashcards
what are the steps of RCT
- diagnosis - with radiographs
- access
- extirpation
- debridement + irrigate
- drying
- obturate + seal
- restoration
what is working length
distance from the coronal reference point to the point at which the canal prep and obturation should terminate (1-2mm short of apex ideally)
what is the master apical file
it is the largest diameter file taken to WL
it represents the final prepared size of the apical portion of the canal at WL
what is tug back when using the master apical file
the cone provides little resistance to its displacement or withdraw from root canal system
what are some reasons for carrying out obturation of prepared root canal
- prevent bacteria ingress at apical foramina
- prevent coronal microleakage of bacteria
- prevents any bacteria remaining in the root canal system from multiplying and spreading
which part of the root canal filling is the most important in ensuring long term success
coronal seal (2-3mm from apex)
how do you decide b/w conventional vs post+core crown placement
conventional
= used when the tooth as a ferrule of a min 1.5-2mm (collar of dentine extending supragingivally 360deg around circumference of tooth)
post+core
= lack of ferrule for the crown to bond to - last resort
what are the functions of a post
a post gains intra-radicular support for a restoration
it is present to retain the core
what are the materials used for core + post
Core
= composte, amalgam, GI
Post
metal - cast gold, SS, brass, titanium
ceramic - alumina/zirconia
fibre - gladd, quartz, carbon
what are types of Posts
prefabricated threaded parallel
prefabricated smooth tapered
indirect custom made
what is a disadvantage of using a prefabricated smooth tapered POST
causes wedging
what are 3 ways to determine POST LENGTH
LENGTH - should be 1/2 to 1/3 length of root or at least equal to the length of the crown
DIAMETER - should be no more than 1/3 of the root width at the narrowest point
APICAL - should have at least 4-5mm of GP left apically
what are the problems associated with POSTS that are inserted that are too wide/too narrow
length is more important than width
BUT the longer/ narrow the post length there is an increased risk of perforation as root gets narrower
tooth is also weakened if root dentine is removed to place a larger post
what are features of CaOH
gold standard intra-canal medicament. has pH 12.5
- provides prolonged anti-bacterial activity
- effective in removing tissue debris
- reduces inflammation via hydrolysis of liposaccharides
- easy to remove
ideal properties of good sealer
exhibits tackiness + provides good adhesion
easily mixed
no shrinkage on setting
bacteriostatic
insoluble in tissue fluids
soluble on re- treatment
radiopacity
components of GP
20% gutta percha
65% zinc oxide
10% radiopacifiers
5% plasticisers
reasons for using sealer during cold compaction (obturation)
there is a limit to how much obturation that be be achieved laterally
- sealers will infiltrate dentine tubules the GP cannot pack into
- seals space between dentinal wall and core
- fills voids of canals, lateral canals and space b/w GP points
- provides lubrication for GP point insertion
what are Herb Schilder’s endo principles
- access should be continuously tapered funnel shape
- apical foramen should be maintained in original position
- apical foramen should be kept as small as possible
other than disinfection why is irrigation important
- provides lubrication
- removal of the smear layer
- dissolves pulp remnants + collagen
what is the irrigant of choice in RCT
sodium hypochlorite 3%
features to take in account when using irrigant
- ensure low pressure (lower than venous pressure in neck)
- slow irrigation
- needle short of WL (never pass deeper than few mm short of WL)
what is the communication called between pulpal space and peri-radicular tissues
lateral canals
what are potential causes of CWL changing during course of endo
root curvature
residual GP left in canal
what are materials used for crowns
metal - gold , platinum, nickel, titanium, chromium
metal ceramic - porcelain fused metal
