Endodontics

Question 1

Aetiology of endodontic disease

Answer 1

• Bacterial invasion
• Development of bacterial ecosystem
• Biofilm formation

Question 2

What radiograph do we require and what are we assessing on the radiograph?

Answer 2

• Undistored PA to show all root and 2-3mm surrounding peri-radicular tissue
• Any PA pathology
• Anatomy of root canal system
• Canal calcifications
• Angulation of root
• No. length and moprphology or roots
• Prox of vital structures

Question 3

Why must all caries be removed prior to endo?

Answer 3

• Allows assessment of restorability
• Creates environment suitable for obtaining adequate iso
• No active disease to tampre with root canal system

Question 4

Why might it be beneficial to build up walls of tooth pre-endo?

Answer 4

• Clamp placement
• Four walled access cavity
• Control irrigant
• Control saliva

Question 5

Why place a dental dam?

Answer 5

• Eliminate bacterial contamination
• Prevent inhalation of instruments
• Retracts tongues and protects ST and tongue
• Prevents pt rinsing , chatting
• reduces chairside time and operator stress

Question 6

What endo instruments are utilised?>

Answer 6

• Mirror front facing
• Locking tweezers
• Probe
• DG 16
• Excavator
• Flat plastic
• Burnisher

Question 7

Objective of Access cavity Preparation

Answer 7

• Remove entire roof allowing complete removal of pulpal tissue
• Allow visualisation of root canal orifices
• Produce smooth walled prep with no overhangs
• Allow unimpeded straight-line access of instruments
• Reservoir for canal irrigant
• Conservative as poss

Question 8

What are the design objectives for RCT?

Answer 8

• Create continuously tapering funnel shape
• Maintain apical foramen in orig pos
• Keep apical opening as small as poss

Question 9

Describe the Watch winding techqniue

Answer 9

• Back and forward oscillation of 30-60degrees
• Light apical pressure
• Use with K files

Question 10

Describe the balanced force technique

Answer 10

• Useful for instrumenttaion of curved canals
• Insert file and engage CW into dentin 1/4 turn
• With continued P go CC 1/2 turn to strip dentin away
• Done 1 to 3 times before removing file to remove debris and check file
• Remove , clean , reintroduce to WL

Question 11

Objectives of Root canal irrigants

Answer 11

• Disinfect root canal
• Dissolve organic debris
• Flush out debris
• Lubricate root canal instruments
• Remove endodontic smear layer

Question 12

What syringe is used for root canal irrigants?

Answer 12

• Luer lock syringe
• 27 gauge endodontic tipped needle
• Press with forefinger not thumb
• Ensure correctly labelled

Question 13

Why do we do coronal flaring before apical prep?

Answer 13

• Avoids hydrostatic pressure in canal
• Early removal of heavily contaminated contents
• Improved straight line access to apical 1/3rd

Question 14

Give the methods of Coronal flaring

Answer 14

• Step down technique
• Double flare technique
• Crown down Pressureless technique

Question 15

Describe how to Canal Access

Answer 15

• PA
• Outline cavity design and use diamond fissure bur
• Rubber dam
• Penetrate pulp chamber at single point above canal orifice
• Use safe ended endo access bur to remove entire pulp chamber
• Flush chamber and coronal aspect with 2% sodium hypochlorite
• Use DG 16 endo probe to locate canal orifice
• Modify to allow straight line access

Question 16

Describe the Modified Double flare (Stepback) technique

Answer 16

• Size 10k file to gently negotitate canals
• Coronal pre flaring using size 2 or 3 Gates Glidden burs in coronal few mm only
• Establish WL (0.5-1mm short of apex via apex locator)
• Establish glide path using size 10K file
• Prepare coronal 2/3rds using hand or rotary NiTi instruments
• Use thorough irrigation recapitulation and patency checked
• Prepare the canal to 3 sizes larger than the first file that binds to the apex
• Step back using next file size up 0.5-1mm from that length
• Copious irrigation, recapitulation and patency re established
• Consecutively keep working the next hand file size up 0.5-1mm short prev length to join apical prep to coronal prep (use watch winding technique and wipe any debris with gauze)
• If abscess/ uncontrolled bleeding/ weeping canals dress with non setting CaOH for 2-4 weeks prior to obturation

Question 17

Describe the Crown Down technique

Answer 17

• sod hypo to remove bacteria
• Introduce pre curved size 10K file to negotiate canals and use gates glidden 2 or 3 to gently flare upwards and outwards in coronal few mm (Coronal flaring)
• Prepare coronal 2/3rds using hand instruments or rotary NiTi instuments
• Establish WL with apex locator (0.5-1mm short)
• Establish glide path with size 10K file
• Copious amounts of irrigation , recapitulation and patency re established
• Using Reciproc 25 prepare apical 1/3rd to WL in brushing pecking motion being careful not to place pressure on the file
• If file feels loose after prep then prep to R40 then R50 if still loose
• Deemed apical gauging
• If abscess of uncontrolled bleeding or weeping canals place non setting CaOH 2-4 weeks prior to obturation

Question 18

Management of hypochlorite accident

Answer 18

• Stop , inform and reassure pt
• Irrigate with copious amounts of saline
• Leave tooth open for drainage
• For pain administer long acting infiltration anaesthesia
• Prescibe NSAIDs
• Reduce risk of secondary infection prescribe Pen V/ Amoxicilin or Met
• Advise cold compression for analgesia initial days
• Then warm compress for circulation in next days
• Review after few days and place temp seal
• Refer to secondary care if swelling on affected side more than 30% compared to contralateral side

Question 19

Estimated WL definition

Answer 19

• Estimated length at which instrumentation should be limited
• Use pre op radiograph to determine coronal reference point and radiographic apex then substract 1mm

Question 20

Corrected WL definition

Answer 20

• 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 21

Master apical file definition

Answer 21

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 22

Properties of AH plus resin sealer for obturation

Answer 22

• Slow setting 8 hrs
• Good sealing ability
• Good flow
• Initial toxciity declining after 24hrs

Question 23

Components of GP

Answer 23

20% Gutta-percha
65% Zinc Oxide
10% Radiopacifiers
5% Plasticizers

Question 24

Describe cold lateral compaction

Answer 24

• Rinse with 17% EDTA for 1 min to remove smear layer
• Rinse with NaOCl
• Dry canal with paper points
• Select master GP cone and mark at CWL with locking tweezers (can take PA to confirm this)
• Check for tug back and undistorted apical portion
• Lightly coat master cone in AH plus sealer resin
• Seat in canal ensuring goes to CWL
• Use finger spreader set to 2mm apical stop and place along GP cone
• Dip accessory points in sealer and insert into canal whilst simultaneously removing finger spreader
• Reinsert spreader and repeat if needed
• Remove excess GP with Super endo alpha at level of canal orifice
• Clean with slow speed and cotton pledget dipped in alchol to allow better bonding for rest
• Seal with RMGIC
• Restore

Question 25

What are the angles for Reciproc?

Answer 25

150 CC then 30 CW

Question 26

When would you use consider using Reciproc Blue ?

Answer 26

- Suitable for strongly curved canals or bypassing ledges - Has higher flexibility due to better centering in the canal

Question 27

What downside can occur with Reciproc files?

Answer 27

- They are freely roatting in a curvature - Leads to generation of tension and compression cycles - Lead to cyclic fatigue - Failure and instrument in canal

Question 28

Complications of endo txt

Answer 28

- Blockage - Ledges - Apical damage (zipping / transportation / enlargement) - Perforation - Fractured instrument

Question 29

Give the two stress that may lead to instrument separation

Answer 29

Torsional stress - Instruments encounters excessive friction on canal walls Flexural stress - repeated cyclic metal fatigue

Question 30

Post op complications

Answer 30

- Pain - Swelling - Need for analgesia - Failure - Prosthetic replacement

Question 31

What are ledges and how to avoid them?

Answer 31

- Internal transportation of canal , occurs when working short or length - Enlarge canal short 1mm of ledge - Place small sharp kink in ISO size 8 file - Feel drop in the canal and do not exit - File and smooth ledge with up and down gentl movement - Once it can glide and feels loose move up to 10, 15, 20 - Continue with canal prep

Question 32

When does Apical Zipping / transportation occur? What can it lead to?

Answer 32

- Tendency of instrument to straighten inside curved canal - Tear drop or hour glass shape due to over prep outer side curve and under prep inner aspect at apical end Avoid by pre curving hand instruments and work chronologically upwards and don't rotate instruments in curved canals

Question 33

What to do if perforation?

Answer 33

- Persistent bleeding into canal - Stop inform and reassure - should have properly consented - Place CaOH and cotton pledget and dress with GIC and refer with location and cause of perforation in letter