aims and objectives of rct Flashcards
How does a periapical lesion develop?
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
What are the lines of defence against bacteria?
- Pulp- releases reparatory tertiary dentine forming a bridge
- Periapex- tissue fluids, inflammatory exudate, immune cells
What must be considered before RCT?
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
What is the aim of RCT?
To prevent or cure apical periodontitis by eliminating the source of infection
What are the objectives of RCT?
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)
What does the RCT procedure involve?
Mechanical prep
Chemical prep- irritants (sodium hypochlorite 1-5%) and inter visit medication (non setting calcium hydroxide)
Obturation
What are the mechanical prep stages?
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)
What does chemical prep involve?
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
What does obturation involve?
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
How is local anaesthetic administered?
Maxillary- labial or palatial infiltration
Mandibular molars- inferior alveolar nerve block
Mandibular premolars- mental nerve block and inferior alveolar nerve block
Why might extra coronal restorations be removed?
Caries is extensive
Marginal deficiency=leakage
Difficulty locating canals
New crown planned after RCT
How are canal orifices located?
Magnification- loupes/microscope
Instruments- endo explorer, rose-head, gates glidden drill, stainless steel file, nickel-titanium file
Why is a straight line access important?
Reduces stress on instruments
Reduces chance of procedural errors
Simplifies treatment- clear path
Why is the coronal 2/3 opened?
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
What is the glide path?
Smooth radicular tunnel from canal orifices to apical constriction
Should be a super loose no 10 endo file
How is the working length determined?
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
Why should over instrumentation be avoided?
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
What is a reference point?
Use a rubber stop that touches a reliable, flat and reproducible reference point on the sound tooth for radiographs
How is a paper point used?
If there is blood/fluid on the instrument, you’re past the apex
What is transportation/zipping?
Due to improper shaping, a new apex is formed which is very problematic
Due to a curved root and progressively larger/stiffer files
What is the master apical file?
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
How is a step back preparation performed?
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
What is apical gauging?
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
What is the ideal irrigant?
Antimicrobial, cheap, dissolves pulp, removes smear layer, easy use, long shelf-life, compatible w dentine, tissue-friendly, substantive, non-corrosive for instruments, non-toxic
What is the smear layer?
1-2 microns
Amorphous film of material generated from instruments contacting canal walls
Plugs dentinal tubules
Delays penetration and effects of antimicrobials
What irrigants are used?
- Medical-grade sodium hypochlorite (1%-90 mins) (5.25%- 90s)- effective but doesn’t remove smear layer
- 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
What are problems with hypochlorite?
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
What are the benefits of smear layer removal?
Smear layer harbours bacteria and acts as nutriment for microbes
It acts as a barrier to irrigant
Influences quality of bond with sealer
Why should chlorhexidine not be used with NaOCl?
It forms a cytotoxic precipitate- parachloroaniline which occludes the dentinal tubules
How is the canal dried after irrigation?
Paper points are used which are colour coded the same as the files
What inter-visit medication is used?
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
How is inter-visit medication delivered?
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
Why is cotton wool not used?
No antimicrobial properties
Doesn’t prevent ingress of microbes
Catches bur when temp filling is cut
Binds on bur and ruins it
How is inter-visit medication removed?
All hard material first removed
Flush out CaOH with irrigation and break up w K file
OR
Use ultrasonic scaler w water
How many endo treatment sessions?
1 visit- dry, asymptomatic tooth and if time permits=obturation
Multivisit- not dry, infected or nectrotic tooth, acutely symptomatic, inadequate time=inter visit medication
What are the aims of obturation?
Prevents coronal leakage or periapica fluids from percolating
Entomb residual microorganisms
Completely seal
Prevent reinfection
What are the ideal properties of a root canal filling material and sealer?
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
What does the root canal sealer do?
It takes up voids around the filler
Fills lateral canals
Fills the space between GP points
Lubricates and helps the GP points to move
What types of root canal sealer are there?
ZOE based, e.g. Tubliseal
CaOH based, e.g. Sealapex
Resin based, e.g. AH Plus
What are different obturation techniques?
Cold lateral condensation
Warm lateral condensation
Warm vertical condensation
What is cold lateral condensation?
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)
Why might there be discolouration of the clinical crown?
Endo materials can stain
By-products of pulp tissue breakdown
Subsequent coronal leakage
Staining from filling materials in the access cavity/pulp chamber
How should GIC/composite be placed?
A layer should be applied over GP and floor of access cavity, completing the coronal seal
What should be mentioned in the radiographic assessment?
Over and under extension
Inadequate filling
