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What are teh 4 steps in RCT?
- 1. Diagnosis
- 2 Access
- 3. Instrumentation
- 4. Obturation
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What is the goal of obturation?
- Create complete seal along the length of the root canal
- From coronal opening to the apical termination
- Includes Apical seal, Coronal seal, Lateral seal
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How does obturation create apical seal of the root canal?
- Prevents percolation: movement of fluid through small spaces, like a leakage
- Percolation leads to endodontic failure
- Bacteria lose viability after obturation
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How does obturation create a coronal seal?
- Permanent restoration needs to be placed within reasonable time frame
- Coronal leakage can communicate oral cavity and periradicular tissues
- A main reason for RCT failure
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How do we achieve a lateral seal?
- A void in mid root can sometimes be acceptable
- Lateral canals communicate periodontium and RC space
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What are the requirements for obturation
- Asymptomatic (not on sore tooth)
- Cleaned and shaped canal to optimal size
- Dry canal
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How do we do lateral condensation?
- Select and place master gutta percha cone
- Achieve correct length and tug-back
- Place RC sealer in the canal
- Laterally place, then condense accessory gutta percha cone
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What is the master cone?
- Standardized gutta percha point that is the same size as the final apical file
- Fits to full working length with tug back
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What is tug back?
- Tightness or resistance to withdrawal of the master cone
- Created by fit of master cone to flare of apical 1-2mm of the cavity preparation
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What is the function of the apex locator?
- Apex locator can establish where the constriction is
- Should be slightly short of the apical foramen
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How short of the apical foramen do we want to be?
From .5-1.5mm of the anatomical length
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How do we use the accessory files?
- We use multiple tips to take the full canal to length
- Push them with the plugger to the CEJ and then establish coronal seal
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Why do we need to reduce the gutta percha past the CEJ?
The sealer can stain the tooth, turning it gray
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What are the two types of filling materials?
- Gutta Percha- Sap of Malaysian sapodilla
- Silver points
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What is Gutta percha?
- Beta dental form from the tree
- Expands on heating, shrinks on cooling
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What are silver points?
- A filling material
- corrosion leads to failure and staining: limited use today
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What are the components of gutta percha?
- Zinc oxide (primary ingredient)
- Gutta percha (plasticity)
- Wax/resin (pliability)
- Metal sulfates (radiopacity)
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What are the two types of gutta percha points
- 1. Standardized: master cone
- 2. Non-standardized: accessory cones
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What are standardized gutta percha points?
- Match standardized files in size and taper #25-100
- Match master cone to master apical file
- Fits snugly with tugback into apical preparation
- Sanitize master cone in NaOCl for 1 minute
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What are non-standardized gutta percha points
- Greater flare and feather tips than standardized
- Fills flared portion of canal around the master cone
- 5 types of taper (M, FM, MF, FF, etc)
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The ideal master cone
- Goes to the working length (WL)
- Gives you tug-back
- Most important and difficult portion of root canal obturation
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What are the 4 ways master cone can go wrong?
- 1. Debris at apex: short working length
- 2. Cone too big: short working length, tug-back
- 3. Cone too small: full working length
- 4. Good cone: full WL, tug-back, obturate
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What are the 5 root canal sealers
- 1. Zinc-oxide Eugenol (Roth)
- 2. Epoxy resin (plastics)
- 3. N2; RC2B (formaldehyde)
- 4. CaOH Sealers (w/ ZOE)
- 5. Glass ionomer(bonds dentin)
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Zinc-oxide-eugenol root canal sealers
- Good seal, easy to handle
- Can decompose in water
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Epoxy Resin root canal sealer
- Antimicrobial, long working time, good seal
- Toxicity and insolubility possible
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N2; RC2B root canal sealer
- Formaldehyde is active ingredient
- Cytotoxic
- No longer used
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Calcium hydroxide sealers
- CaOH2 incorporated into ZOE sealer
- Potential osteogenic effect at the apex
- antimicrobial activity
- Questional long-term stability and toxicity
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Glass Ionomer Root canal sealers
- Dentin-bonding agent
- Adequate apical and coronal seal
- Insoluble, retreatement difficult
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Worry about post-operative discomfort?
No. It's usual and doesn't indicate obturation success
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How do we use radiographs to evaluate obturation?
- Radiolucency: voids
- Denstiy: uniformity
- Continuous taper
- Lateral canals leading to radiographic lesion
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What will happen to extruded sealer?
It will be gone in 6 months, along with any lucencies
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Places to lose seal and fail RCT
- Cracked root
- Leaking temp
- Over/underextended and over/underfilled canal
- Multiple portals of exit
- undetected major canals (like MB2)
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