Access and Instruments for RCT in posteriors

Question 1

What makes up the pre-treatment RCT assessment?

Answer 1

Clinical assessment

• Caries
• Restorations
• Status of remaining tooth structure - cracks, structural durability
• Rotation/tilting of tooth
• Mobility
• Pocketing
• Status of mucosa
• TTP
• Colour change

Radiograph assessment - PA
Can rubber dam be used?
Is tooth restorable following the endo tx?

Question 2

What is parallax?

Answer 2

Determines the difference between canals which overly eachother on a radiograph
Used before tx or during

Question 3

What is the MBD rule?

parallax method

Answer 3

MDB rule - when the X-ray tube moves Mesially, the Buccal canal moves to the Distal in the image

Question 4

What is the SLOB rule?

parallax method

Answer 4

Same = Lingual
Opposite = buccal
X-ray tube moves mesially so the lingual (palatal) canal moves in the same direction (mesially) and the buccal canal moves in the opposite direction (distal)

Question 5

Preliminary RCT tx?

Answer 5

Ensure tooth is adequately restored - caries, replace defective restorations
Dismantle coronal restorations and replace them with a new core build up or a provisional indirect restoration

Question 6

Access cavity prep features?

Answer 6

No undercuts
Smooth axial walls
All coronal orifices visible

Question 7

Objectives of an access preparation?

Answer 7

Forms a funnel to allow instruments straight line entry into the canal orifices and into the apical 3rd
Allows safe irrigation and ease of shaping
Straightens out curves to allow more accurate working length determination

Question 8

Number of root canals and features of them in upper premolars?

Answer 8

Upper premolars - Often have deep pulp chambers
2 root canals, upper 5s might only have 1
4s sometimes have 3

Question 9

Lower premolars root canals?

Answer 9

1 but 30% have 2
Lingual canal often missed due to access
To find lingual canal curve file and move it down the lingual aspect of the access - it will catch

Question 10

Upper molar root canals?

Answer 10

3 but may have 2nd mesio-buccal root canal (=4) = more palatal and mesial
MB2 more common in a 6 than 7

Question 11

Lower first molar root canals?

Answer 11

3 canals - 2 mesial and 1 distal

Distal can be 2 root canals or 1 that splits into 2

Question 12

What bur to use to remove the roof of the pulp chamber?

Answer 12

Endo-Z bur

Question 13

What should each root have?

Answer 13

It’s own reference point on the occlusal surface and its own working length

Question 14

What is strip perforation?

Answer 14

Curved canal - part of canal wall will be overprepared = more risk of perforation
Avoided by anti-curvature filing: preferential filing away from the high risk areas