L2- Cleaning and Shaping Flashcards
what are the shaping principles
- a constantly 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 “deep space” for proper obturation
what is the 9 step prep
- scouting (#10 hand file)
- patency (#10 hand file)
- working length (#15 hand file) TIGHT file
- glide path (#15 hand file) Loose file
- shaping of coronal 1/3 of canal (wave one gold)
- shaping of middle 1/3 of canal (wave one gold)
- perfect straight line access to mis root (.25/.12 carefully)
- shaping of apical 1/3 of canal (wave one gold)
- final shaping objective (vortex blue or SSB with hand files
what is the motion in scouting
watch winding- move right and left rocking motion
how many degrees each way does the watch winding motion move in
30 degrees
the canal is patent when:
a #10 file goes slightly beyond the canal exit (.5mm) = long = into the PDL
what helps find the canal exit clinically
apex locator
when do you measure patency in lab
before you mount
patency is maintained by:
recapitulation
if it is a tight resistance to apical advancement:
you probably have a small canal which must be enlarged carefully to reach patency
if it is loose resistance to apical advancement:
you have encountered a canal curvature and you must bend the terminal flute of your file and search for the path to negotiate the curve
what is the reference point for working length on anteriors
incisal edge
what is the reference point for working length for posteriors
cusp for which canal is named, flatten cusp when possible
what file number do you take to patency
10 only
how do you tell if canals converge or are simply 2 canals in close proximity
the 2 file technique
what is the 2 file technique
- establish working length of each canal separately
- attempt to place 2 files to WL in each canal at same time
- if both go to working length = 2 canals
- if one goes and the other is short reverse the placement sequence and if it is still short then you have a converging class II canal
what is the purpose 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
what is the glide path created using
hand files that are pre-curved to match or slightly exceed the curvature of the canal
- using watch wind entry followed by pull strokes directed in a circumferential manner to enalrge the canal to a size #15 at the WLd
in creating a smooth glide path the #15 file should end up:
sloppy loose
why do you not want to take a working file short of WL
youll have blockage and ledging
how many times should you revist patency during cleaning and shaping
2-3
describe the small wave one gold reciprocal file
.20mm at tip
0.7 overall taper
- maximum flute diameter 0.8mm
describe the primary wave one gold reciprocal file
0.25mm at tip
0.07 overall taper
MFD = 0.9mmd
describe the large wave one gold reciprocal file
0.45mm at tip
0.05 overall taper
MFD = 0.8mm
wave one gold files are used only with:
the dentsply motor on the wave one setting
what is the operator action for a wave one reciprocal file
a light pecking motion
what is a downside of the wave one gold reciprocal files
they push debris ahead of the file so stop action at 1/3 and 2/3 of the operation approaching the apex to clean the file and to irrigate thoroughly at these stages of shaping
what do you choose the size of wave one file based on
the diameter of the canal you are treating
if a 10 K-file was very resistant to movement what wave one gold file would you choose
small
if a 10 K-file moves easy to length, is loose or very loose what wave one gold file do you choose
primary - 85%
if a 20 hand file or larger goes to length what wave one gold file do you use
large
wave one gold files come in what lengths
21,25, and 31mm
the crown is usually about how long
10mm
what are the 1/3s of the canal divided into and about how long are each
coronal (13-15mm)
- middle (16-20mm)
- apical (19-25mm)
how do you perfect straight line access to mid root
place a 0.25/0.12 vortex orifice opener in the pro-mark motor and adjust the action to vortex and leave the speed at 500 rpm
MFD is 1.2mm
describe the action used with the .25/.12 straight line access to mid root
allow the .25/.12 to mill to the depth of mid root only. any lateral motion should be away from the furcal area
how do you shape the apical 1/3 of the canal
set the wave one gold file at the confirmed WL and reset the pro-mark motor to reciprocal action and guide it to advance to the WL
what is the MAF for small roots
30-#35
what is the MAF for medium roots
40-#45
what is the MAF for large roots
45-#50
teeth with moderate to severe curvature require ___ MAF to avoid transportation of canal
smaller
younger teeth will have _____ canals and required ____ MAF to clean
larger; larger
what are examples of teeth with small MAFs
mandibular incisors, 2 canal premoalrs, mesial canals of madnibular molars and buccal canals of maxillary molars
what are examples of teeth with medium MAFs
palatal canals of maxillary molars, single distal canals of mandibular molars
what are examples of teeth with large MAFs
maxillary anteriors, M/M cuspids, single canal M/M premolars
what is used for final shaping
vortex blue files sizes 0.30/0.04 through 0.50/0.04
describe final shaping with the vortex blue files
it needs to keep moving and go completely to WL on each of 10 strokes
- they should be flexed while rotating and being drawn out to increase the flare of the canal n an appropriate direction away from furca or towards the greater dimension of the canal
final shaping is complete when:
dentinal filings are on apical 1/3 of instrument
when is serial step back used
with big canals larger than the .45/0.4 vortex blue file and need to open in the middle
how are ledges and blockages created
when we place a straight SS hand file in a curved canal
- tends to gouge and lean against the outside wall of the canal creating a ledge which can be the first step to blockage or transportation
as our shaping proceeded to the larger sizes of SS hand files above #15:
- increase in stiffness
- decrease in flexibility
what is a zip
when transportation of apex occurs within the root
what is an apical strip perforation
if the zip occurs through the apex to the exterior of the root
hand files are generally no larger than ______ because mainly of ______
15; transportation
what does it mean when there is loose resistance to apical advancement
you are encountering a ledge or a possibly abrupt bend or curve
what do you do if you find loose resistance to apical advancement
- do not force file
- stop irrigate and bend a #10 file at the tip- approximately 2mm
- the most apical flutes of the file must be bent and rotated to track the inside wall of the canal
- gently enter canal rotate and advance the file a little at a time through the full 360 degrees until you fall into a tight area
- this is the canal and the file can now often advance and bypass the obstruction/ledge to join the true canal
the curved file is to be oriented correctly to:
coincide or slightly exceed the curvature of the canal
how is the curved file used in a bend in a canal
in a watch winding motion and then flexed in a rasping pull motion with circumferential filing after the path is negotiated
when does strip perforation occur
when files used are either too large or too aggressively used for a small or thin walled canal
where is strip perforation common
the distal of the mesial root of lower molars
- MF of upper molars
- 2 canal maxillary premolars
how do you fix strip perforation
gutta percha and PC sealer
how can transportation occur with wave one gold file
if there is a curve in the apical 1/3 and the glide path is not smooth and the operator tries to push or force the wave one gold file to WL
how can transportation occur with vortex blue files and how can it be avoided
allowing them to rotate at or slightly short of WL for more than 1 moment
- must keep moving using a smooth in-out motion in the canal while flexing it on the out stroke to smooth and further flare the walls
