Determination of working length and inter-visit medication Flashcards
Master apical file
> prep of apex at working length up to size 25 at minimum OR
>/ 2 file sizes above file size which first fitted snugly at working length
Step-back
Prepares apical 1/3 by creating series of steps
Achieved by shortening length of file and reducing length
Continue until you have met up with the prep of coronal 2/3
File size 25 prep length
20mm
File size 30 prep length
19mm
File size 35 prep length
18mm
Apical gauging
Finish prep of RC - MAF size 25
Insert MAF - should meet some light resistance and feel snug in last 2mm - shows there is contact between file and RC wall
Insert size 25 file to working length and ensure it is at your reference point
Apply apical pressure to file with fingers
If file moves apically at all a larger file size is needed
Move up 1 file size and repeat ‘apical gauging’ procedure
If you > size of MAF, refine your step-back prep
Chemical prep
Irrigants
Inter-visit medication
Ideal irrigants
Antimicrobial Cheap Able to dissolve pulp tissue Able to remove smear layer Easy to use Long shelf-life Compatible with dentine Tissue-friendly Substantive (remain in RC for sustained period) Non-corrosive for dental instruments Non-toxic
Smear layer
1-2 microns
Amorphous film or organic and inorganic material generated from instruments contacting RC walls
‘Plugs’ dentinal tubules
Delays penetration and effects of antimicrobials
Action of irrigants
Removal of debris
Lubrication of instruments
Antisepsis
Decomposition and removal of blood and tissues
Irrigants
Medical-grade sodium hyperchlorite (NaOCl, 1% - kill time: 90 minutes// 5.25% kill time 90 seconds)
Ethylendiaminetetraacetic acid (EDTA 17%)
Chlorhexedinegluconate (2%)
Iodine compounds (allergic reaction)
Sodium hyperchorite
Conc 0.5-5.25%
Highly effective antibacterial agent
Dissolve residual pulp tissue & organic matter
Much more effective warmed
Must be frequently replenished for effective cleaning and disinfection
Does not remove smear layer
Hyperchlorite accident
Inadvertent extrusion of hypochlorite into periapical tissue
Percentage, volume and pressure is important
EDTA
Chelating agent Solution and paste Minimum 2 minutes Remove smear layer Aid negotiation of calcified RCs Unable to dissolve organic matter Used in conjunction with NaOCl
How to remove smear layer
Use sodium hyperchlorite throughout access into pulp chamber and complete canal prep
Use EDTA to remove smear layer and open tubules for soaking
The more infected the case, the more disinfection required
Benefits of smear layer removal
Harbours bacteria and may also act as nutriment for microbes
May act as barrier to irrigant and medicament penetration
May influence quality of bond obtainable with RC sealers
If disintegrates after completion of RCT, will affect seal of RC filling material
Chlorhexidine
Anti-bacterial
Unable to dissolve organic or inorganic tissue
Not as effective as NaOCl but suitable alternative
Suggested conc 2%
Should not be used in combination with NaOCl due to formation of cytotoxic PCA
Inter-visit medication
Visible bacteria can still be isolated from approx 60% of RCs following disinfection
Type of material: non-setting calcium hydroxide, odontopaste
Calcium hydroxide
Ca(OH)2 has high initial pH (approx pH12)
Few bacteria can flourish in its presence
21 days for hydroxyl ions to diffuse through dentine to reach maximum pH 9
Optimally, calcium hydroxide should be left in root canal between 2 and 4 weeks but not more
(non-setting, needs to be in contact with bacteria to kill them)
Mode of action of calcium hydroxide - Ca(OH)2
pH ~12
Damages bacterial cytoplasmic membranes
Denatures proteins
Damages DNA
Inactivates bacterial enzymes
Bacterial replication associated with loss of genes and lethal mutations
Hydroxyl ions to induce lipid peroxidation
This results in the destruction of phospholipids and breakdown of lipopolysaccharides
Odontopaste
New, effective therapeutic endodontic dressing (used as a paste instead of calcium hydroxide to help calm a very acute situation)
Antibiotic (5% Clindamycin) - kills bacteria
Corticosteroid (1% Triamclinone) - reduces inflammation
Calcium hydroxide in a zinc oxide paste
Shouldn’t be left for a long time
Delivery of inter-visit medication
Master K-file
Large paper point
Lentulo spiral fillers
Above inter-visit medication
Make sure access cavity is completely clean and dry from ACJ upwards
Temporise tooth:
-CaO2
-Endosponge
-Cavit or coltosol (ZOE)
Coronal seal: GIC/ IRM/ Kalzinol (ZOE)
-optimally, CaOH should be left in root canal between 2 or 4 weeks
Cotton wool
Traditionally used underneath temporary
Has no anti-microbial properties
Does not prevent ingress of microbes from oral environment
Catches bur when it cuts through temporary filling and enters pulp chamber - loud screeching noise
Binds on bur and ruins it
Damages bacterial cytoplasmic membranes
Fibres trapped in cavity margin will wick bacteria and contaminants from oral environment (saliva and nutrients for dormant bacteria)
