lecture 4: cleaning and shaping with curved canals Flashcards
are there any straight lines in human anatomy
no, all canals are curved. that is why you should curve your SS files before placement in a canal.
new shaping and electric torque control motors should
eliminate ledging and canal transportation
hand files are still necessary to appreciate and develop
- scouting the canal to patency and establishing WL
- negotiating severe curves, blockages and ledging
- creating a smooth #15 glide path
- SSB in larger canals
when should you refer
basically if greater than 30 degrees
radiographs will show which types of curves
M and D curves
F and L curves will NOT generally be seen
what should you do to XR to try to see F and L curves
- SLOB
- look for “bulls eye”
- see if your #10 SS scouting file bends
NA and some other Asians have a higher chance of having what
D-L md 1M (3rd root)
as our shaping proceeded to the larger sizesof ss hand files above #15
we have increase in stiffness and decrease of flexibility
which means that it can straighten out the canal and result in
ledges and blockages
canal transportation
what is a zip
the result of transportation of apex occurs within the root
what is one of the main reason we do not have hand lives larger than #15
because of transportation
what is a elbow
the smaller part of the funnel created by the apical failure to follow the curved canal
can a zip occurs through the apex to the exterior of the root, what is this called
apical strip perforation
with the ss hand files increasing in diameter and stiffness it resists what
resists adaptation to the natural curve of the canal
if you develop resistance when approaching a curve what should you do
stop and call an instructor.
can transportation still occur with vortex blue files
yes.. by leaving it rotating for more than a moment, YOU NEED TO KEEP THE VORTEX MOVING while flexing it on the out stroke to further flare the walls.
can transportation still occure with wave one gold file
yes.. if the operator tries to push or force the wave one gold file to WL because a very smooth glide path was not perfected.
why did we change to modern Ni-Ti files, new technique and expensive motors
because of ledging and transportation
Ni-Ti are straight but-
- EXTREMELY FLEXIBLE but will transport if inattentive and pushed
- SUPER-ELASTIC AND EXPENSIVE will only follow a smooth glide path
to avoid blockage
irrigate
to avoid ledging
curve and insert files correctly and irrigate
to avoid file separation
single use files inspect and don’t skip sizes or force
once a ledge or blockage is created it is…
very difficult and time consuming to regain the canal
if a ledge is created or if we encounter loose resistance to apical advancement, we modify the curvation to include what
the very terminal flute of the SMALL FILE to about 45 degree curve to bypass the curve toward the inner wall or to scout for the direction of the curve
a simple ledge which is ignored will soon create what
sufficient debris in the canal to create a blockage
most common causes of blockages:
- failure of recapitulate
- failure to gain and maintain patency
- failure to recognize loss of length ledge/blockage/curve
what is dentin mud
it can rapidly become harder than dentin especially in vital cases
when do we use strip - perforation
when files used are either too large or too aggressively used for a small or thin walled canal
in maxillary molars how many canals are there
MB1 and MB2 95% of the time
mandibular molars have what type of canals
DF and DL about 60% Type II
MF and ML 40% type II
what type of canals do max 1PM have
85% have two roots
types of canal configurations
I, II, III, IV
i, o, u, y
what is the 2 file technique
how you tell if canals converge or are simply 2 canals in close proximity?
- establish WL of each canal
- attempt to place 2 files to WL in ea canal @ same time
in the 2 file technique if both go to WL then what does that mean
2 canals
in the 2 file technique if one goes and the other is short what does that mean
reverse the placement sequence if still one is short then it is a converging Class II canal
the “high cervical break” what is it
- using .25/.12 to create a smooth glide path in the MB canal,
- insert it about 3 to 4mm into the canal
- the purpose is to remove the dentin triangle and align the access to a more advantageous path to the canal
which teeth can benefit from the high cervical break
- MB canals from max molars
- both mesial canal of md molars
- any time that we can eliminate/minimize a cervical curve it will give better access to mid root and make apical curves easier and file separation will be less likely
why do files break aka separate
- judgment erros
- cyclic fatigue (inside)
- torsional stress (outside)
what is torsional stress
the larger the instrument or the tighter the curve, the greater the stretching on the outer diameter of the curved instrument and the greater the compression on the inner diameter of the curve
what is cyclic fatigue
greater acceleration of the curve results in increased stress from stretching and compressing resulting in increased cyclic fatigue
if you feel that you need to push the rotary file what should you do
go back and smooth or carefully enlarge the glide path with a small properly curved hand file
anytime obturation is not yet accomplished what should you do
place intracanal medication
any time a temp restoration is placed, it a good idea to do what
medicate and seal with proper interim temporization
what is the most popular intra-canal medication to use for between RCT visits
CaOH
where should you place the interim placement
-2mm short of the WL (do NOT allow to BIND) and then CaOH is expressed as the syringe is retracted from the canal
- fill the canal to cervical line
- clear excess CaOH from chamber
- place sterile cotton pellet in chamber to prevent clogging of the canal with temp filling material after the cotton pellet
what do you place over the cotton
cavit, IRM, amalgam or composite
what is cavit
and when is it best used
comes from the tuber or jar ready to place in the tooth. No mixing. Seals better than IRM (1-2 weeks) but deteriorates rapidly
best used for 1 surface access
what is IRM
1-4 week duration of seal = stronger = use when 2 or more surfaces are missing
what is composite, amalgam and temp crowns
when considerable tooth structure is compromised of a greater delay to next tx visit is anticipated.
temporization following obturation
use “vitrebond”
what is vitrebond
a resin modified glass ionomer
it is recommended to seal the obturated canal against leakage following successful RCT completion while awaiting perm restoration.
if saliva remains in contact with GP for 72 hours what will happen
re tx will be required
follow “vitrebond” with what
composite, amalgam, temp crown etc, as a base for crown to follow or as directed by restorative faculty
if your tx plan calls for a post what should you do
place cotton over obturation
no vitrebond.
instead place substantial IRM/amalgam/composite or temp crown over cotton –> XR –> Completed RCT film without rubber dam
place rubber dam, remove IRM/amalgam/composite and cotton and proceed with post and planned restoration
if your tx plan calls for a crown
- DO NOT PLACE COTTON over obturation
- place amalgam or vitrebond and composite as a build up –> XR –> RCT without rubber damn
restorations of RCT ant teeth that need to be done ASAP
minimal structural loss –> vitrebond and composite
significant structural loss –> crown or post and crown
restorations of RCT post teeth that need to be done ASAP
minimal structural loss: Crown ALL POST
significant structural loss: post and crown
2 things to remember about posts
- posts do NOT strengthen tooth (they weaken it)
- posts provide ONLY RETENTION of coronal restoration
