Session 3

Question 1

What is the estimated working length?

Answer 1

• Estimated length at which instrumentation should be limited. Obtained by measuring pre-operative radiograph to determine distance between coronal reference point and radiographic apex then subtracting 1mm

Question 2

What is the corrected working length?

Answer 2

• Length at which instrumentation and subsequent obturation should be limited. Obtained by the use of an electronic apex locator and/or working length radiograph

Question 3

What is the master apical file?

Answer 3

• The largest diameter file taken to working length and therefore represents the final prepared size of the apical portion of the canal at the working length

Question 4

What are resin sealers made of?

Answer 4

• Epoxy resin

Question 5

What is the mixing of resin sealers like?

Answer 5

• Paste-paste mixing

Question 6

What is the setting of resin sealers like?

Answer 6

• Slow setting - 8 hours

Question 7

What is the sealing ability of resin sealers like?

Answer 7

• Good sealing ability

Question 8

What is the flow of resin sealers like?

Answer 8

• Good flow

Question 9

There is initial toxicity of resin sealers which declines after 24 hours. What can this result in?

Answer 9

This may lead to some post-op sensitivity

Question 10

What % of GP in gutta-percha?

Answer 10

• 20% GP

Question 11

What is gutta-percha?

Answer 11

• Naturally occurring rubber compound

Question 12

What % of Zinc Oxide is in GP?

Answer 12

65%

Question 13

What % of Radiopacifiers is in GP?

Answer 13

10%

Question 14

What % of Plasticizers is in GP?

Answer 14

5%

Question 15

What different types of GP point can you get? (4)

Answer 15

• Standardised
• Non-standardised
• Size-matched
• Thermal obturation

Question 16

What is cold lateral compaction?

Answer 16

This is a means of using multiple points of GP to create a complete obturation with GP and sealer between the GP points

Question 17

Does cold lateral compaction allow good adaptation to canal irregularities?

Answer 17

• No (but with the use of sealer and a good technique we can still manage to obturate some expansions of the canal)

Question 18

Why do we use finger spreaders instead of hand spreaders?

Answer 18

• The problem with hand spreaders is you can apply a great deal of force to a hand spreader and can break a tooth

Question 19

What are we looking for in a ‘cone fit’ radiograph?

Answer 19

• Should reach the position that you have identified as your corrected working length on the radiograph
• If it is long or short would need to modify things to allow it to go to the appropriate length
• If too long then would be determined when place GP cone initially because it would sink below the level that you would have determined it would go to
• If this is the case we can either increase the size of the cone or alternatively can trim off the excess GP so that it sits at the appropriate length
• So if 3mm longer than the corrected working length then trim 3mm and try again and it should fit snugly
• Fit snugly - what you should perceive when you withdraw the GP cone is that you get ‘tug-back’ so the cone provides a little bit of resistance to its displacement from the root canal system

Question 20

How can we alter the fit of a master cone?

Answer 20

• Can trim the cone to fit
• IF cone doesn’t go to length then important to ensure that master cone does go to length
• Can try a different cone so if using size 50 try another 50 or if that doesn’t work should go back in and modify your apical instrumentation, should redefine your apical stop and possibly redefine your apical taper to give a bit more space so cone can fit
• When trying cone in need to make sure the canal is wet at all times - so should have some of our irrigants in the canal

Question 21

Explain briefly cold lateral compaction?

Answer 21

• Have master cone that goes to corrected working length
• Then place a finger spreader alongside the master cone and this is going to require apical and lateral pressure which is going to create space
• This space can be filled with accessory cones
• Important that prior to maser apical cone being inserted that you coat it with a very thin layer of sealer
• Then place your finger spreader to create space for your accessory cone

Question 22

How do we remove excess GP from a root canal?

Answer 22

We should use a heated plugger (alpha unit or heat it with a bunsen burner) and then severe off the GP which then allows us to compact the GP into the space

Question 23

When we finish obturation where do we want to aim to finish it?

Answer 23

• Want to aim to finish it at the level of the ACJ

- So the GP should be seen just below the level of the orifice but should not coat the walls of the pulp chamber

Question 24

Give a summery of cold lateral compaction?

Answer 24

• A = we finish the preparation
• B = we try our finger spreader in - should go to corrected working length or just shy of our CWL by 1-2mm
• C = we then place our mater apical cone with sealer
• D = then laterally condense with our finger spreader
• E = then apply our accessory cone with some additional sealer
• F = spread laterally
• G = Additional rounds of compaction with accessory cone placement
• H = When severe off should severe off at the level of the ACJ which will then allow us space to put a thin layer of vitrebond/RMGIC and then will leave us the opportunity to place the definitive restoration