Access and instruments for posterior teeth

Question 1

What is included in the radiographic assessment

Answer 1

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

Question 2

If have a subgingival restoration why may this be a reason to not do RCT?

Answer 2

Need to stop any irrigant coming out and ensure it wont leak in the future

Question 3

What are the 2 questions you need to ask before doing the RCT after the assessment?

Answer 3

Can the tooth be isolated with RD

Is the tooth restorable following RCT treatment

Question 4

When doing an endodontic clinical assessment, what is included in the clinical assessment?

Answer 4

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

Question 5

What is parallax used for?

Answer 5

To determine the difference between the canals which overlap each other on a radiograph e.g. premolars, mesial canals in lower molars

Question 6

What is the MED rule?

Answer 6

When the X-ray tube moves to the mesial, the buccal canal moves to the distal of the image

Question 7

What is the SLOB rule?

Answer 7

The xray tube moves mesially, so the lingual canal moves in the same direction and the buccal canal moves in the opposite (distal) direction

Question 8

What is preliminary treatment?

Answer 8

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

Question 9

What is needed in the access prep?

Answer 9

No undercuts
Smooth axial walls
All canal orifices visible

Question 10

what are the objectives of an access prep?

Answer 10

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

Question 11

What are the 3 access preparation guidelines?

Answer 11

Access prep - into the pulp chamber
Radicular shaping - coronal 2/3rds
Canal preparation

Question 12

What is the problem with accessing the upper premolar?

Answer 12

Deep pulp chambers
Access cavity not deep enough to remove all of the pulp chamber
The pulp horns are very circular

Question 13

What % of lower premolars have 2 canals?
Which one is normally missed?
How do you test for this?

Answer 13

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

Question 14

Where are the different root canals in the upper molars?

Answer 14

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

Question 15

What are the essential basics for instrumentation of the canals?

Answer 15

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

Question 16

For the multirooted teeth, what should each root have?

Answer 16

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

Question 17

Why is there a risk fo perforation when filing the canal?

Answer 17

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

Question 18

What can be done to prevent perforating while filing?

Answer 18

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

Question 19

Why do you need to beware of gates glidden drills?

What is an alternative?

Answer 19

They give a circular prep in the canal,

Use special files, SX files in the pre-taper method follows the RC better

Question 20

What can you do to get rid of the pulp stones/

Answer 20

Pop them out with a probe or use a bur to loosen them out

Question 21

What can be used in a sclerosed canal?

Answer 21

EDTA gel - use small file to get in, make sure use Kfile then use Hedstrom to widen the canals

Question 22

What happens to the length of the canal as it straightens?

Answer 22

The working length shortens