Access and instruments for posterior teeth Flashcards
What is included in the radiographic assessment
Remove composite and caries, assess whether extends gingival margin, can you acheive isolation?
Furcal lesion reduces the prognosis, may respond but very guarded prognosis
If have subgingival restoration which extends into root chamber - contraindication for RCT
If have a subgingival restoration why may this be a reason to not do RCT?
Need to stop any irrigant coming out and ensure it wont leak in the future
What are the 2 questions you need to ask before doing the RCT after the assessment?
Can the tooth be isolated with RD
Is the tooth restorable following RCT treatment
When doing an endodontic clinical assessment, what is included in the clinical assessment?
Caries Restorations Status of remaining tooth structures - cracks, structural durability Rotation or tiliting of tooth Mobility - can only do if grade I Periodontal pocketing Status of mucosa TTP Colour change
What is parallax used for?
To determine the difference between the canals which overlap each other on a radiograph e.g. premolars, mesial canals in lower molars
What is the MED rule?
When the X-ray tube moves to the mesial, the buccal canal moves to the distal of the image
What is the SLOB rule?
The xray tube moves mesially, so the lingual canal moves in the same direction and the buccal canal moves in the opposite (distal) direction
What is preliminary treatment?
Ensure the tooth is adequately restored - restore caries, replace defective restorations
Dismantle coronal restorations
Any suspect indirect restorations should be removed and replaced with either a new core build up or provisional indirect restoration
Remove suspect restorations and caries, restore the tooth prior to access
What is needed in the access prep?
No undercuts
Smooth axial walls
All canal orifices visible
what are the objectives of an access prep?
Forms a funnel to allow instruments straight entry into the canal orifices and into the apical 1/3
Allows safe irrigation
Allows ease of shaping
To straighten out curves to allow more accurate working length determination
What are the 3 access preparation guidelines?
Access prep - into the pulp chamber
Radicular shaping - coronal 2/3rds
Canal preparation
What is the problem with accessing the upper premolar?
Deep pulp chambers
Access cavity not deep enough to remove all of the pulp chamber
The pulp horns are very circular
What % of lower premolars have 2 canals?
Which one is normally missed?
How do you test for this?
30%
Lingual is often missed due to access - shelf of dentine stops access into lingual
To test: Curve the file drag down lingual, if have one will flick into it
Where are the different root canals in the upper molars?
Big palatal is the widest - find this one first, then go more buccal
MB1 towards the corner
DB more palatal
Draw a line between MB1 and DP and find MB2
What are the essential basics for instrumentation of the canals?
DG16 probe
Long shank burs - allow access deeper into RC
Goose neck burs - shaft very thin, cant put same amount of pressure
Small mirror easier to use
Magnification
For the multirooted teeth, what should each root have?
It’s own reference point on the occlusal surface and it’s own working length
See which cusp the file naturally wants to lay against
Why is there a risk fo perforation when filing the canal?
File follows the curve but wants to straighten up, the inside of the curve will be prepared the most
More dentine removed, greater risk of perforation
What can be done to prevent perforating while filing?
Anti-curvature filing: Preferential filing away from high risk areas
Curve the file to the same direction of the canal, prepare outer curve as well as inner
Why do you need to beware of gates glidden drills?
What is an alternative?
They give a circular prep in the canal,
Use special files, SX files in the pre-taper method follows the RC better
What can you do to get rid of the pulp stones/
Pop them out with a probe or use a bur to loosen them out
What can be used in a sclerosed canal?
EDTA gel - use small file to get in, make sure use Kfile then use Hedstrom to widen the canals
What happens to the length of the canal as it straightens?
The working length shortens
