lecture 2: cleaning and shaping Flashcards
the 9 step prep
- scouting
- patency
- working lengths
- glide path
- shaping of coronal 1/3 of canal
- shaping of middle 1/3 of canal
- perfecting straight-line-access to mid-root
- shaping of apical 1/3 of canal
- final shaping objective
step 1: scouting file
- locate and negotiate canals
- once pulpal access is achieved you locate canals using endo explorer
what do you look for with the endo explorer
you look for a ‘stick’ in the canals
what file do you use for step one
scouting file #10
if you don’t irrigate what will happen
if you don’t irrigate you will almost certainly block yourself out and never reach patency
what is watch winding
a gentle right and lock rocking motion which causes the instrument to cut while inward pressure
step 2: obtain patency
finding patency using the #10 file going slightly beyond the canal exit and use the apex locator.
how it patency maintained
by recapitulation (irrigating and revisiting patency occasionally with the patency file only)
if you have a tight resistance to apical advancement then
you probably have a small canal which must be enlarged carefully to reach patency
if you have a loose resistance to apical advancement then
you have encountered a canal curvature and you must ben the terminal flute of your file and search for the path to negotiate the curve
during recapitulation what is very important:
you need to irrigate the canal and revisit patency
step 3: working length
ALL shaping is done at WL which is 1mm short of the canal exit.
confirm with a #15 SS File
is WL critical to RCT success
yes
what are your reference points
ant: incisal edges
post: cusp for which canal is named, flatten cusp when possible
step 4: create a smooth “glide path”
- its created using hand files (pre-curved to match or slightly exceed the curvature of the canal)
- enlarge the canal to a size #15
the purposes of creating a smooth glide path
- to smooth curves and make sure there are no canal obstructions
- to create space for rotary instruments to be used safely without excessive torque requirements
- to relieve stress on tip of rotary file to minimize fracture
step 5 to 8: shaping the canals by thirds
- coronal, middle and apical
- use the machine driven file to begin canal shaping.
what lengths do wave one files come in
21, 25, and 31 mm.
select the appropriate length for your tooth
you choose the size of wave one file to be used based on the
diameter of the canal you are treating
a 10 K file was resistant to movement so you use
a wave one gold small file
if a 10 k-file moves to length easily, is loose or very loose, use
a wave one gold primary file
if a 20 hand file or larger goes to length, use
a wave one gold large file
you will be shaping the canal 1/3 at a time:
you will shape around 3-5mm at a time for each section
wave one gold reciprocal files sizes are
small: 0.2mm at tip
primary: .25mm at tip
large: .45mm at tip
step 7: straight line access to mid root
- use a .25/.12 vortex orifice opener
- mill to the depth of mid root only.
- any lateral motion should be away from furcal area
- recapulate: irrigate
step 8: shaping apical 1/3
- confirm patency and WL
- then irrigate
step 9: final shaping objective
- pick MAF at the WL
- each canal is different and allows for a certain cleaning and shaping
MAF =
master apical file
MAF for small, medium and large roots
small: #30-35
medium: #40-45
large: #45-50
final shaping objective
- using vortex blue file keep moving and go completely to WL.
- they should be flexed while rotating and being drawn out to increase the flare fo the canal in an appropriate direction .
vortex blue files automatically give you a __ taper
0.06 taper
how long should the vortex blue be there when taken to WL
no longer than 1 sec at WL or short of WL
if you rotate the vortex blue file short of the WL what will it create
it will ALWAYS create a ledge
primary etiologies of pulpa and periapical ds
- caries or other injuries
- infected dentin and soft tissue (pulp)
- microorganisms and their toxins invade
- substrate in canal system fuels micro-organisms
- result is peri-radicular lesion
primary objectives of rct
- remove all caries
- remove infected dentin and pulp
- remove micro-organisms and toxins
- remove substrate from the canal system
- create a shape encouraging proper obturation
- seal the root canal system and all portals
what are the 5 shaping principles
- a constant tapering funnel from crown to WL
- curves of canal respected w/o transportation
- retention of the apical constriction
- enlargement of the canal system to create clean white fillings (adequate cleaning)
- adequate “deep space” for proper obturation
what shapes do we want:
- constantly tapering funnel
- that is a better deep shape
- and follows the natural shape of the canal
shaping techniques
shaping: the files do the shaping
- removes of all caries and infected dentin
- allows convenience form for effective irrigation
- creates a resistance form to facilitate effective obturation
- conserve tooth and root structure to minimize VRF
cleaning techniques
- irrigation cleans
- 8.3% NaOCl and 17% EDTA
- it dilutes and neutralizes toxins
- dissolves and removes substrates
- flushes out debri
- edta removes the smear layer
what removes the smear layer
edta
results of early RCT attempts by students
- over-enlarging
- strip-perf
- transportation
- inadequate flair
WL key points
- critical to success
- 1mm short of canal exit
how is the WL measured
at a reproducible reference point
usually use the cusps for which the canal is named.
if the WL is too short what will it result in
a blockage
if the WL is too long what will it result in
a blow out
finding the WL: ETL
estimated total length
if tooth in mount, ETL
use the apex locator in clinic
what is a “serial step back”
- aka SSB
- a process to create an apical resistance form when rotary instruments are not available due to very large canal diameter
is it difficult to blow out lots of sealer with a large apical foramen
NO, it is EASY
especially with hydraulic obturation
when should SSB be used
- when a canal requires enlargement larger than a size #.50, it will be necessary to employ SSB
- when a blow out has been created and you need to create a new and larger apical control zone and taper to contain the GP within the root
ACZ is
apical control zone
how does SSB work
- initial apical gauge = #50 file
- take MAF to #60 hand file at ACZ to retain (GP)
- SSB at 1mm to #70, #80, #90, #100, #110, creates a taper using essentially straight hand files
- SSB creates a taper coronal to ACZ to facilitate obturation in the absence of appropriate tapered files
- final apical gauging
- now have a good shape for GP
what is final apical gauging
- using hand files for SSB
- it should show a #45 goes patent, after MAF, a #60 file binds to ACZ and a #70 binds 1mm short
what type of shape will you end up with in a SSB
- a “stepped” preparation
