aims and objectives of rct

Question 1

How does a periapical lesion develop?

Answer 1

Cementum prevents the release of toxins along the dentinal tubules and into the PDL but they’re released through the apical foramen and lateral canals

Question 2

What are the lines of defence against bacteria?

Answer 2

1. Pulp- releases reparatory tertiary dentine forming a bridge
2. Periapex- tissue fluids, inflammatory exudate, immune cells

Question 3

What must be considered before RCT?

Answer 3

Restorability of tooth
Visibility of pulp chamber and canal space
Shape of canal
No of roots and canals
Presence of any periapical lesion
Presence of any previous RCT

Question 4

What is the aim of RCT?

Answer 4

To prevent or cure apical periodontitis by eliminating the source of infection

Question 5

What are the objectives of RCT?

Answer 5

Complete removal of irreversibly damaged/necrosis pulp
Dissolution and debridement of!infected tissue by cleansing, disinfecting and shaping
Create optimal shape to allow well-compacted filling (obturation)

Question 6

What does the RCT procedure involve?

Answer 6

Mechanical prep
Chemical prep- irritants (sodium hypochlorite 1-5%) and inter visit medication (non setting calcium hydroxide)
Obturation

Question 7

What are the mechanical prep stages?

Answer 7

Local anaesthetic
Isolation w oroseal
Access cavity prep
Location of canal orifices
Straight line access
Prepare glide path coronal 2/3
Opening coronal 2/3
Prepare glide path full length
Working length determination
Shape canal to working length
Determine master apical file
Step back prep (every 1mm)

Question 8

What does chemical prep involve?

Answer 8

Flush out remnants of tissue and debris
Dissolve residual pulpal tissue
Kill bacteria and remove bacterial biofilm
Clean parts of inaccessible canals
Facilitate instrumentation and prevent blockages by acting as a lubricant
Remove smear layer

Question 9

What does obturation involve?

Answer 9

Fill canal w 3D filling
Completely seal anatomical parts
Prevent reinfection by denying access to oral bacteria
Resolution of signs and symptoms of disease
Restore integrity of tooth

Question 10

How is local anaesthetic administered?

Answer 10

Maxillary- labial or palatial infiltration
Mandibular molars- inferior alveolar nerve block
Mandibular premolars- mental nerve block and inferior alveolar nerve block

Question 11

Why might extra coronal restorations be removed?

Answer 11

Caries is extensive
Marginal deficiency=leakage
Difficulty locating canals
New crown planned after RCT

Question 12

How are canal orifices located?

Answer 12

Magnification- loupes/microscope

Instruments- endo explorer, rose-head, gates glidden drill, stainless steel file, nickel-titanium file

Question 13

Why is a straight line access important?

Answer 13

Reduces stress on instruments
Reduces chance of procedural errors
Simplifies treatment- clear path

Question 14

Why is the coronal 2/3 opened?

Answer 14

Removes bulk of infected tissue
Reduces risk of pushing debris apically
Eliminates interferences so reduces risk of blockages apically
Early intro of irrigants into apical portion
Easier negotiation of working length
Improved tactile feedback apically

Question 15

What is the glide path?

Answer 15

Smooth radicular tunnel from canal orifices to apical constriction
Should be a super loose no 10 endo file

Question 16

How is the working length determined?

Answer 16

Different morphology, radiographic interpretation
Apical constriction is 0.5-1mm short of apical foramen
1. Measure preop radiograph
2. Tactile feedback (file large enough)
3. Working length radiograph
4. Electronic apex locator
5. Paper point

Question 17

Why should over instrumentation be avoided?

Answer 17

Less damage to apex and tissues
So there’s no extrusion of debris (may contain microorganisms, necrotic pulp, infected dentine chips)
So there isn’t excess root filling in the periapical tissue that might act as foreign matter

Question 18

What is a reference point?

Answer 18

Use a rubber stop that touches a reliable, flat and reproducible reference point on the sound tooth for radiographs

Question 19

How is a paper point used?

Answer 19

If there is blood/fluid on the instrument, you’re past the apex

Question 20

What is transportation/zipping?

Answer 20

Due to improper shaping, a new apex is formed which is very problematic
Due to a curved root and progressively larger/stiffer files

Question 21

What is the master apical file?

Answer 21

The biggest K file that is able to enter the canal to the correct working length
~increase up to #25 at minimum
OR
~at least 2 file sizes above the size which first fit snuggly at working length

Question 22

How is a step back preparation performed?

Answer 22

The apical 1/3 is prepared via a series of steps (1mm intervals)
The length of the file is shortened until you have met up with the preparation of the coronal 2/3
E.g. #25-20mm, #30-19mm, #35-18mm
At each step, you need to recapitulate by going back to the MAF and irrigating

Question 23

What is apical gauging?

Answer 23

It’s important to respect the dimensions of the apical foramen
The apex needs to gauged prior step back-
MAF should have light resistance in the last 2mm
If when pressure is applied, the file moves apically, a larger size is needed
This should be repeated until resistance is achieved

Question 24

What is the ideal irrigant?

Answer 24

Antimicrobial, cheap, dissolves pulp, removes smear layer, easy use, long shelf-life, compatible w dentine, tissue-friendly, substantive, non-corrosive for instruments, non-toxic

Question 25

What is the smear layer?

Answer 25

1-2 microns Amorphous film of material generated from instruments contacting canal walls Plugs dentinal tubules Delays penetration and effects of antimicrobials

Question 26

What irrigants are used?

Answer 26

1. Medical-grade sodium hypochlorite (1%-90 mins) (5.25%- 90s)- effective but doesn’t remove smear layer 2. EDTA (17%-1 min) removes smear layer, aids negotiation of calcified root canals Sodium hypochlorite and EDTA both used Could use- Chlorhexidinegluconate- 2%- unable to dissolve tissue- suitable alternative to NaOCl but shouldn’t be used together Iodine compounds- allergy

Question 27

What are problems with hypochlorite?

Answer 27

Need leak proof isolation BUT ALSO Inadvertent extrusion of hypochlorite in periapical tissue could cause extreme pain and necrosed tissue Due to needle locking and irrigant being pumped through Depends on percentage, volume and pressure Can use a rubber stop to prevent needle from locking

Question 28

What are the benefits of smear layer removal?

Answer 28

Smear layer harbours bacteria and acts as nutriment for microbes It acts as a barrier to irrigant Influences quality of bond with sealer

Question 29

Why should chlorhexidine not be used with NaOCl?

Answer 29

It forms a cytotoxic precipitate- parachloroaniline which occludes the dentinal tubules

Question 30

How is the canal dried after irrigation?

Answer 30

Paper points are used which are colour coded the same as the files

Question 31

What inter-visit medication is used?

Answer 31

Non-setting calcium hydroxide (pH12)- damages bacterial cytoplasmic membranes and DNA, denatures proteins, inactivated bacterial enzymes -hydroxyl ions induce lipid peroxidation so phospholipids destroyed and lipopolysaccharides broken down Odontopaste (5% Clindamycin and 1% Triamcinolone)- reduces bacterial contamination a post-op pain

Question 32

How is inter-visit medication delivered?

Answer 32

``` Master K-file Large paper point Lentulo spiral fillers Calcium hydroxide should be left between 2-4weeks Put in endo sponge Temporise cavity with GIC or IRM ```

Question 33

Why is cotton wool not used?

Answer 33

No antimicrobial properties Doesn’t prevent ingress of microbes Catches bur when temp filling is cut Binds on bur and ruins it

Question 34

How is inter-visit medication removed?

Answer 34

All hard material first removed Flush out CaOH with irrigation and break up w K file OR Use ultrasonic scaler w water

Question 35

How many endo treatment sessions?

Answer 35

1 visit- dry, asymptomatic tooth and if time permits=obturation Multivisit- not dry, infected or nectrotic tooth, acutely symptomatic, inadequate time=inter visit medication

Question 36

What are the aims of obturation?

Answer 36

Prevents coronal leakage or periapica fluids from percolating Entomb residual microorganisms Completely seal Prevent reinfection

Question 37

What are the ideal properties of a root canal filling material and sealer?

Answer 37

Radiopaque, inert, bio-compatible, safe, long shelf-life, easy use, prevent leakage, adapts to irregular shape, dimensionally stable on setting, compatible w other materials, cheap, bactericidal, insoluble in tissue fluids

Question 38

What does the root canal sealer do?

Answer 38

It takes up voids around the filler Fills lateral canals Fills the space between GP points Lubricates and helps the GP points to move

Question 39

What types of root canal sealer are there?

Answer 39

ZOE based, e.g. Tubliseal CaOH based, e.g. Sealapex Resin based, e.g. AH Plus

Question 40

What are different obturation techniques?

Answer 40

Cold lateral condensation Warm lateral condensation Warm vertical condensation

Question 41

What is cold lateral condensation?

Answer 41

Use paper point to paint sealer on the walls Measure GP point by creasing them at the coronal reference Should have good talk back Introduce with a bit of sealer With hand/finger spreader in place, take an accessory point and dip in sealer Repeat using gradually larger spreaders and GP points until the canal is filled Remove excess GP from the canal orifices w a heated instrument and firmly compact remaining to seal (level of CEJ)

Question 42

Why might there be discolouration of the clinical crown?

Answer 42

Endo materials can stain By-products of pulp tissue breakdown Subsequent coronal leakage Staining from filling materials in the access cavity/pulp chamber

Question 43

How should GIC/composite be placed?

Answer 43

A layer should be applied over GP and floor of access cavity, completing the coronal seal

Question 44

What should be mentioned in the radiographic assessment?

Answer 44

Over and under extension | Inadequate filling