Session 5

Question 1

What are the 3 design objectives for endodontics?

Answer 1

• Create a continuously tapering funnel shape
• Maintain apical foramen in original position
• Keep apical opening as small as possible

Question 2

Once we have identified the orifice of the root canal system we must carry out some early or initial opening. What does this enhance?

Answer 2

• This enhances straight line access

Question 3

Once we have identified the orifice of the root canal system we must carry out some early or initial opening. How do we do this?

Answer 3

• Can use our GG Bur

- GG can be used to remove overhanging dentine

Question 4

What material are protaper files made from?

Answer 4

Nickel Titanium

Question 5

What property does nickel titanium have that is useful for the files?

Answer 5

• Superelasticity
• This allows for accessibility whilst in the root canal system
• Allows us to create variable tapers

Question 6

When creating straight line access, what do we want to remove and why?

Answer 6

Want to remove the lip of dentine (this could lead to displacement of the file which could lead to risk of perforation)

Question 7

Which protaper file can we rely on to produce straight line access?

Answer 7

S1 file

Question 8

What is the diameter of the S1 protaper file?

Answer 8

0.17mm

Question 9

What is the diameter of the S2 protaper file?

Answer 9

0.20mm

Question 10

What is the diameter of the Sx protaper file?

Answer 10

0.19mm

Question 11

How does the shape of the S1 protaper file help produce straight line access?

Answer 11

• Minimal taper apically but significant taper towards the handle of the instrument which, leads to a very wide portion of the instrument at the handle end

Question 12

What are the differences in shape of the S1 and S2 protaper files?

Answer 12

• S1 has minimal taper apically but significant taper towards the handle of the instrument which, leads to a very wide portion of the instrument at the handle end
• This is in comparison to the S2 which has a slightly bigger tip size and the taper leads to an enhanced diameter of the instrument in the middle portion and a slightly smaller diameter at the more coronal portion of the instrument

Question 13

What is the file shape like on the Sx protaper file?

Answer 13

• Really short cutting blade but a significantly increasing taper over a short space
• Not typically use din routine endodontics although it can be used to pre-flare or used in very short canals
• The instrument allows us to modify the diameter of the root canal very rapidly can also be used to enhance the coronal flaring before further instrumentation occurs

Question 14

How do we create some coronal flaring of the canal of a posterior tooth?

Answer 14

• Initially pass a 10 or 15 file about 2/3 of the working length then we would use the S1 which would only go to about 2/3 of the EWL
• This would create some coronal flaring of the canal because of the rapidly increasing taper
• Only going to instrument coronally

Question 15

Do we use the Sx protaper to produce coronal flaring?

Answer 15

• Can use this but it is not commonly used

Question 16

When measuring working length, where should preparation end?

Answer 16

• Preparation should end at the junction of pulpal and periapical tissue

Question 17

Where should working length be as close to as possible?

Answer 17

• Should be as close as possible to the CDJ

Question 18

What is the narrowest part of the canal?

Answer 18

• The apical constriction

Question 19

What can we use to determine the corrected working length of a root canal?(2)

Answer 19

• Radiograph

- Electronic apex locator (more accurate)

Question 20

How do we create a glide path?

Answer 20

• Confirm straight line access
• Explore anatomy
• Always introduce files 10-25 to resistance only (coronal only)
• Coronal flare - S1
• Size 10 with watch winding establish apex
• Irrigate and repeat using sizes 15 (WW) and 20 (BF)

Question 21

What is a glide path?

Answer 21

• It is a preparation of the root canal that allows subsequent instruments to move freely and safely within the canal

Question 22

When creating a glide path we need to use a size 10 then size 15 file using a watch winding motion to expand the apical portion of the root canal system. Why do we need to do this?

Answer 22

• This ensures that when we take our S1 and S2 to CWL the tip of the instrument which is rather delicate is not overloaded and therefore limits the risk of instrument failure

Question 23

What technique do we use when using the S1 protaper file?

Answer 23

• Use a balanced force technique

Question 24

What technique do we use when using the S2 protaper file?

Answer 24

• Use a balanced force technique

Question 25

Remember recapitulation and patency filing with copious irrigation. What will happen if we fail to irrigate?

Answer 25

- If fail to irrigate we increase the risk that we will create blockages - Blockages will lead to shortage of WL, possibly ledges and possibly instrument separation and perforations

Question 26

What files do we use to finish the apical preparation in posterior teeth?

Answer 26

- We finish the preparation using F files - Finishing files - Going to use F1 using BF and then move on until we reach the apical diameter that we want to reach

Question 27

What is the K file equivalent to the F1 finishing file?

Answer 27

20 k file

Question 28

What is the K file equivalent to the F2 finishing file?

Answer 28

25 k file

Question 29

What is the K file equivalent to the F3 finishing file?

Answer 29

30 k file

Question 30

What is the K file equivalent to the F4 finishing file?

Answer 30

35 k file

Question 31

What is the K file equivalent to the F5 finishing file?

Answer 31

40 k file

Question 32

What is the apical taper in the last 3mm of an F1 finishing file?

Answer 32

7%

Question 33

What is the apical taper in the last 3mm of an F2 finishing file?

Answer 33

8%

Question 34

What is the apical taper in the last 3mm of an F3 finishing file?

Answer 34

9%

Question 35

What is the apical taper in the last 3mm of an F4 finishing file?

Answer 35

6%

Question 36

What is the apical taper in the last 3mm of an F5 finishing file?

Answer 36

5%

Question 37

- Historically apical diameters have been dictated by guides where we have a range of suggested apical sizes - Truth is we can't dictate given the apical diameter for every tooth Apical diameter has to reflect a few things. What are these things? (3)

Answer 37

1. It has to reflect the original size of the root canal - want to prepare to 2 or 3 sizes larger than the size that binds apically 2. Need to look for what the dentine looks like - if the dentine that ha been removed looks nice and white it is probably clean and there fore the size is probably sufficient 3. Have to bear in mind the ability to irrigate Because the F files have quite a large apical taper an F2 does provide sufficient space for irrigation to be effective

Question 38

What is apical gauging and how do we do it?

Answer 38

- How do we know if we have control? - One way of doing this is by doing something called apical gauging - This is when we take a file to the corrected working length and it won't advance any deeper - Use an apex locator at this point and it should be able to reach 0 with light apical pressure - Problem when we use an F2 is that not only will it potentially bind apically but it might also bind more coronally because of the flare there - What we do in apical gauging following the use of the nickel titanium file system is that we put in an equivalent K file - So if using an F2 we want to place a 25 K file into the root canal at CWL we then want to place light apical pressure and this file should not advance beyond the corrected working length - The reason we want to use a 25K file is that because of the taper we have created with the S1, S2, F1 and F2 the K file will generally only bind apically, will not bind more coronally because of the 2% taper - In a very curved canal it may bind in the curvature but mostly will get binding only apically - If we get control at this point we can determine that an F2 is sufficiently large to create apical control? And so that when we come to place our obturation material, the material is less likely to loose control and be placed apically - If 25K file slips beyond the CWL then we will need to make the apical portion bigger using larger F files until we determine control

Question 39

Briefly explain the protpaer sequence for preparing a root canal in posterior teeth?

Answer 39

- Going to use a 10 and 15 file for scouting and then to create a glide path that will be 2/3 of the WL - Then going to use S1 for early coronal shaping (balanced force technique) - Can then use an Sx if we need to but often not required - Then irrigate - Then take our 10 file to EWL with apex locator to determine a reading - Possible that we may need to use a larger file if our apical diameter is big so may go to a 15 or bigger - Once got CWL (which is 0.5mm-1mm shorter than the 0 reading) we are ready to create our glide path to at least a size 15 but maybe a size 20 - We will then take our S1 to CWL followed by a series of irrigation, recapitulation and patency filing - Can then take our S2 to length and can irrigate, recapitulate and patency file - Then want to move on to F1 (balanced force) until we reach CWL - Then typically we will want to go bigger - this will be determined by apical gauging - IF canal is exceptionally curved we may only be able to expand the canal apically to an F1 then may need to accept some degree of compromise