Endodontics

Question 1

Endo objectives

1. Design objectives
2. Clinical objectives

Answer 1

1. Create a continuously tapering funnel shape, maintain apical foramen in original position, keep apical opening as small as possible
2. Remove canal contents, eliminate infection

Question 2

1. What improves success

2. Function of dam in endo

Answer 2

1. Hypochlorite irrigant, dam

2. Protect airway, improve access, efficacy and vision, prevent contamination, protect soft tissues

Question 3

Endo diagnoses

1. 5 pulpal diagnoses
2. 6 apical diagnoses

Answer 3

1. Normal - asymptomatic, normal thermal response (mild/short sensitivity), vital
   Reversible pulpitis - inflamed, pain to stimulus, resolves with treatment
   Symptomatic irreversible pulpitis - lingering pain to stimulus, pain with postural changes
   Asymptomatic irreversible pulpitis - no symptoms, usually normal thermal test
   Pulpal necrosis - negative pulp test, TTP, radiographic osseous breakdown, can be asymptomatic
2. Normal - not TTP, uniform PDL space
   Symptomatic apical periodontitis - TTP, pain with biting, PA radiolucency
   Asymptomatic apical periodontitis - asymptomatic, PA radiolucency
   Acute apical abscess - rapid, swelling, TTP, spontaneous pain, systemic symptoms
   Chronic apical abscess - gradual, asymptomatic, PA radiolucency, sinus ± pus discharge
   Condensing osteitis - localised bony reaction to low-grade inflammatory stimulus, diffuse PA radiopacity

Question 4

Biofilm

1. Development stages
2. 3 resistance features of biofilms

Answer 4

1. Adhesion, colonisation, accumulation to form complex community, dispersal
2. Antimicrobials cannot penetrate beyond surface layer, trapped/destroyed by enzymes, inactive against non-growing organisms, expression of biofilm-specific resistance genes

Question 5

Mechanical prep

1. 2 aims
2. Stages

3 What determines apical prep

Answer 5

1. Create space to allow irrigants and medicaments to more effectively eliminate micro-organisms, remove infected hard and soft tissues
2. Tooth prep, access cavity, confirm straight line access, initial negotiation, coronal flaring, WL determination, apical preparation
3. Apex size (largest passive ISO file taken to WL - ideally, passive gauging to ISO 25)

Question 6

Irrigation

1. 3 irrigants (and %) and final irrigations steps
2. 3 ideal irrigant properties
3. NaOCl 3 pros/2 cons
4. NaOCl accident management and 3 ways to prevent

Answer 6

1. 3% NaOCl, 17% EDTA, 0.2% CHX
   10 mins NaOCl, 1 min EDTA, 10 mins NaOCl
2. Disinfect canal (remove micro-organisms), dissolve organic and inorganic material, remove smear layer, cheap, non-toxic to PA tissues
3. Dissolves organic material, disrupts smear layer, effective antimicrobial; doesn’t remove smear later, dissolve fabrics, accident
4. Copious irrigation, analgesia, review
   Bib/eyewear, slow flow rate (1ml/15s), depress with index finger, don’t lock needle in canal, use side-vented Leur-Lock 27G needle, avoid excessive pressure

Question 7

Smear layer

1. Define
2. How removed

Answer 7

1. Superficial (1-5um) layer of organic pulpal and inorganic dentinal material formed during preparation, with packing into dentinal tubules. Prevents/interferes with disinfection and sealer penetration
2. 17% EDTA, 10% citric acid, MTAD

Question 8

Intra-canal medicament

1. What
2. 2 reasons why

Answer 8

1. nsCaOH

2. Antibacterial, reduces inflammation, kills micro-organisms in canal, effective at removing tissue debris

Question 9

Cleaning/shaping

1. 3 purposes of chemomechanical prep
2. 3 instrumentation essentials
3. Name and describe instrumentation technique

Answer 9

1. Irrigate to remove microbes, remove smear layer, prepare shape for obturation to WL, flush out debris, remove infected hard/soft tissues, allow delivery of irrigants to WL
2. Copiuous irrigation, recapitulation, patency filing
3. Modified-double flare technique
   Enlarge/flare coronal part of root canal, negotiate narrower apical part, flare apical and middle parts using ‘step-back’ technique (apex-1mm = file at apex - 1 size, etc.)

Question 10

Define:

1. EWL
2. CWL
3. MAF

Answer 10

1. Estimated length at which instrumentation should be limited. Usually 1mm short of radiographic apex
2. Actual length at which instrumentation should be limited
3. Largest file taken to working length. Represents final prepared size of apical portion of canal

Question 11

Instruments motion

1. 5 types, describe 2
2. ISO sizes and colours
3. Hand-files – 3 cons
4. NiTi main feature
5. Rotary 2 pros/2 cons,
6. 3 ways to prevent fracture
7. ProTaper sizes and taper %

Answer 11

1. Filing, reaming, envelope of motion
   Watch-winding - 30-60 degree oscillation movement with light apical pressure
   Balanced force - engage file, 1/4 turn CW, 1/2 turn CCW, repeat x2, irrigate, patency file, irrigate, recapitulate, irrigate, repeat
2. 6 (pink), 8 (grey), 10 (purple), 15/45 (white), 20/50 (yellow), 25/55 (red), 30/60 (blue), 35/70 (green), 40/80 (black)
3. Time-consuming, less predictable, ledges, apical zipping, perforations, blockages
4. Super-elasticity
5. Quicker, more predictable, increased flexibility and cutting efficiency, easier to use, safer
   Limited posterior access, # potential, expensive
6. Create glide path, crown down technique, ensure straight line access, gentle pressure
7. F1 - 20/7%, F2 - 25/8%, F3 - 30/9%, F4 - 40/6%, F5 - 50/5%

Question 12

Glide path

1. Define
2. Describe process
3. Purpose of early coronal flaring

Answer 12

1. Use of smaller files (to working length) before introducing larger files to prevent #
2. Confirm straight line access, explore anatomy, introduce ISO files 10-25 to resistance only (coronal only), early coronal flaring (S1), ISO 10 WW to WL to establish apex, irrigate, recapitulate, repeat with ISO 15 (WW) and ISO 20 (BF)
3. Reduce hydrostatic pressure in canal during irrigation, provide reservoir for irrigants

Question 13

Obturation

1. 3 ideal properties
2. 3 reasons to obturate
3. GP composition
4. 3 sealer functions
5. 3 properties
6. 3 ways to place
7. 3 obturation methods (describe one)

Answer 13

1. Non-staining, bacteriostatic, radiopaque, biocompatible, non-irritant, inert
2. Fluid-tight apical seal, kill remaining microbes, prevent microbial reinfection, seal off lateral canals
3. 20% GP, 65% ZnO, 10% radio pacifiers, 5% plasticiser
4. Seal lateral canals, fill voids/seal spaces that GP doesn’t fit, seal between GP points and GP point and dentinal walls, lubricates during obturation
5. Non-staining, bacteriostatic, radiopaque, biocompatible, low viscosity (able to flow), non-irritant, inert
6. Via master cone, files, accessory points
7. Warm lateral compaction, carrier-based obturation, continuous wave obturation
   Cold lateral compaction - remove access, patency filing, recapitulate to final prepared size, irrigate, dry, place corresponding GP cone, tug-back with locked tweezers at WL, cone-fit radiograph, dry, coat in sealer, fit master cone, finger spreader to 2mm from apical stop forcing GP to fit apical collar and force to side of canal, accessory points inserted until full, excess GP removed (melted), points drilled together (slow speed) to 1-2mm below ACJ, RMGIC coronal seal, definitive restoration

Question 14

RCT treatment

1. 3 risks
2. 3 outcomes
3. 4 management options of failure
4. RCT steps

Answer 14

1. Perforation, instrument separation, failure, pain
2. Success - asymptomatic, normal PDL
   Uncertain - a/symptomatic, PAP same size/reduced but not gone after 4yrs
   Unfavourable - symptomatic, continuing root resorption, PAP larger/new after 4yrs
3. Monitor, re-treatment, periradicular surgery, extraction
4. Coronal access, instrumentation, chemomechanical preparation, obturation, coronal seal, final restoration

Question 15

9 endo laws

Answer 15

1. Centrality - floor of pulp is always located in centre of the tooth at the level of ACJ
2. Concentricity - walls of pulp chamber are always concentric to external surfaces of tooth at level of ACJ
3. ACJ - ACJ is most consistent, repeatable landmark for locating position of pulp chamber
4. Symmetry 1 - orifices of canals are equidistant from line drawn in the mesio-distal direction through pulp chamber floor (except U6s)
5. Symmetry 2 - orifices of canals lie on a line perpendicular to line draw in mesio-distal direction across the centre of the floor of the pulp chamber (except U6s)
6. Colour change - colour of pulp chamber floor is always darker than the walls
7. Orifice location 1 - orifices of root canals are always located at junction of walls and the floor
8. Orifice location 2 - orifices of root canals are always located at the angles in floor-wall junction
9. Orifice location 3 - orifices of root canals are located at terminus of root development fusion lines

Question 16

1. Mechanical prep stages
2. Glide path steps
3. Obturation functions
4. Sealer functions
5. Instrumentation technique

Answer 16

1. Tooth prep, access cavity, confirm straight line access, initial negotiation, coronal flaring, WL determination, apical preparation
2. Confirm straight line access, explore anatomy, introduce ISO files 10-25 to resistance only (coronal only), early coronal flaring (S1), ISO 10 WW to WL to establish apex, irrigate, recapitulate, repeat with ISO 15 (WW) and ISO 20 (BF)
3. Fluid-tight apical seal, kill remaining microbes, prevent microbial reinfection, seal off lateral canals
4. Seal lateral canals, fill voids/seal spaces that GP doesn’t fit, seal between GP points and GP point and dentinal walls, lubricates during obturation
5. Modified-double flare technique
   Enlarge/flare coronal part of root canal, negotiate narrower apical part, flare apical and middle parts using ‘step-back’ technique (apex-1mm = file at apex - 1 size, etc.)