Canal preparation 1

Question 1

List two phases of canal preparation

Answer 1

1. Debridement

2. Shaping

Question 2

Debridement

Answer 2

Removal of all tissue and bacteria from root canal system

Question 3

Shaping

Answer 3

Create shape to facilitate obturation

Question 4

Describe warnings of debridement

Answer 4

• MUST confine instruments within root canal
• Avoid pushing debris out root apex
• Create shape within canal for chemical irrigant

Question 5

Describe warnings of shaping canal

Answer 5

• Maintain special relationship of root canal within dentine
• Establish a “seat/stop” at apical termination
• Create tapering funnel
• Eliminate all surface irregularities along root canal walls

Question 6

Endodontic failure is usually due to?

Answer 6

Colonizing of the filled canal system after treatment.

Question 7

Primary goal of endodontic treatment?

Answer 7

Optimize root canal debridement and disinfection

Question 8

Most favourable prognosis of end of canal instrumentation

Answer 8

Terminate at apical constriction

Question 9

Least favourable prognosis of end of canal instrumentation

Answer 9

Working beyond apical constriction

Question 10

List end of canal instrumentation aim and reference point

Answer 10

• End instrumentation at transition point between pulp and periodontal tissue (cemento-dentinal junction)
• Reference point: 0.5 - 1.5 mm inside apical foramen
• Aim to create smallest wound surface

Question 11

In general, file is _____ to apex than it appears in the radiograph

Answer 11

Closer

Question 12

When file is placed _____ in radiograph, it is actually ______ to apical foramen than it appears.

Answer 12

Short; closer

Question 13

When file is placed __________ in radiograph, it is actually _______ past apical foramen than it appears.

Answer 13

Long; further

Question 14

List landmarks of end of canal instrumentation

Answer 14

• Apical constriction
• Apical foramen
• Radiograph vertex

Question 15

List recommended apical termination points

Answer 15

• 1.0 mm from radiographic vertex where no bone resorption occurs
• 1.5 mm from radiographic vertex where only bone resorption occurs
• 2.0 mm from radiographic vertex where bone and root resorption occurs

Question 16

List goals of preparation

Answer 16

• Create continuously tapering funnel
• Minimize canal transportation
• Apical termination point of canal preparation should be kept as small as possible.

Question 17

Minimizing canal transportation

Answer 17

Position of apical foramen and apical constriction should remain unchanged.

Question 18

File

Answer 18

Tapered and pointed metal instrument with cutting edges used to enlarge the root canal by filing action

Question 19

K-file

Answer 19

• File with square cross-section
• USed in all zones, but mostly in apical zone
• Use “Watch-winding” technique and “push-pull” action

Question 20

H-file

Answer 20

• File with circular cross-section
• Used in coronal and middle zone only
• Use “pulling” action only

Question 21

Flexofile

Answer 21

• File with triangular cross-section
• Flexible
• None-aggressive tip

Question 22

Taper

Answer 22

The increase in file diameter with every 1 mm from the tip.

Question 23

0.02 Taper means?

Answer 23

The filer gets 0.02 mm wider with every 1 mm from the tip

Question 24

Circumferential (perimetre) filing

Answer 24

Repeat filing motion along entire inner perimeter of canal

Question 25

Gates-Gliddens burs used when? Fracture rate?

Answer 25

Used only in Coronal zone. | - Easy to fracture in canal

Question 26

Speed of Gates-Gliddens burs?

Answer 26

Use at low speed

Question 27

Action of Gates-Gliddens burs?

Answer 27

- Passively insert into canal - Withdraw from canal with light "paint-stroke" action along a wall - Keep GG bur spinning until fully removed

Question 28

Only use No. 2 GG bur when?

Answer 28

Only use No. 2 GG bur after #40 H-file has been used. Then sequentially use No. 3 GG bur and No. 4 GG bur (only in large canals)

Question 29

List benefits of crown-down instrumentation

Answer 29

- Most important benefit -> provides a glide path - Facilitates irrigant exchange - Provides coronal escape-way for filing debris - Reduces piston-pump effect - Reduces apical extrusion of debris - Improves instrument and irrigant access to apical canal - Reduces potential for vapour lock

Question 30

Lsit the steps of modified crown-down technique

Answer 30

1. Access cavity preparation 2. Determine working length (allows checking of canal patency and prep. configuration) 3. Coronal one-third preparation 4. Middle one-third preparation 5. Apical one-third preparation

Question 31

Describe file size choice

Answer 31

- 3 sizes bigger than the first file that binds | - Variation depends highly on curvature of root

Question 32

List the preparation zones (only applies when Working length WL < 19 mm)

Answer 32

- Coronal one-third = WL - 8 mm - Middle one-third = WL - 4 mm - Apical one-third = WL

Question 33

Phases of canal preparation: describe access cavity

Answer 33

- Access cavity should mirror the coronal pulp chamber - Follows the long axis of tooth, not just crown long-axis - Law of concentricity = Walls of pulp chamber are concentric to the external outline of tooth at level of CEJ

Question 34

Define "Law of concentricity"

Answer 34

Walls of pulp chamber are concentric to the external outline of tooth at level of CEJ

Question 35

Instrumentation for access cavity

Answer 35

- Pre-curve instrument: Match curvature of radiographic image - ALWAYS have irrigant in the canal during instrumentation (need fluid for lubrication)

Question 36

Define "Stem winding action"

Answer 36

CW/CCW twisting of file no more than 30 deg with positive apical pressure - Pre-curved files can be rotated less or none - Pre-curved files have increased risk of transporting canal

Question 37

Phase of canal preparation: tactile negotiation

Answer 37

- Use Stem-winding action - Stem-winding insertion to working length - Do NOT screw instrument into canal - Only use with K-Files

Question 38

How to establish working legnth?

Answer 38

Use radiograph with file in canal

Question 39

Describe circumferential filling

Answer 39

- Stem winding insertion to working length - Cutting stroke on withdrawal of file - No rotation of file in circumferential filing

Question 40

After each incremental size increase in file, the ___________- is re-introduced for what?

Answer 40

Recapitulation file (i.e. original file used to measure working length) is re-introduced to working length to ensure canal remains patent and check for wall irregularities.

Question 41

Recapitulation purposes?

Answer 41

- checks canal configuration - Reduces vapour lock - Facilitates irrigant transfer to apical zone of canal - Prevents compaction of debris at bottom of canal

Question 42

Apical patency

Answer 42

Technique where apical portion of canal is maintained free of debris by recapitulation with a small file through the apical foramen

Question 43

Never re-use a _____ file and why?

Answer 43

Never reuse a loaded file therefore tooth debris file flutes. - Clean file with gauze - check the length of file

Question 44

Equipment for canal preparation in coronal one-third?

Answer 44

Gates glidden burs or Hedstroem Files

Question 45

Equipment for canal preparation in middle one-third?

Answer 45

Use Hedstroem Files and K Files

Question 46

Equipment for canal preparation in apical one-third?

Answer 46

Use K-files only