What are teh 4 steps in RCT?
- 1. Diagnosis
- 2 Access
- 3. Instrumentation
- 4. Obturation
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
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
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
How do we achieve a lateral seal?
- A void in mid root can sometimes be acceptable
- Lateral canals communicate periodontium and RC space
What are the requirements for obturation
- Asymptomatic (not on sore tooth)
- Cleaned and shaped canal to optimal size
- Dry canal
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
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
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
What is the function of the apex locator?
- Apex locator can establish where the constriction is
- Should be slightly short of the apical foramen
How short of the apical foramen do we want to be?
From .5-1.5mm of the anatomical length
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
Why do we need to reduce the gutta percha past the CEJ?
The sealer can stain the tooth, turning it gray
What are the two types of filling materials?
- Gutta Percha- Sap of Malaysian sapodilla
- Silver points
What is Gutta percha?
- Beta dental form from the tree
- Expands on heating, shrinks on cooling
What are silver points?
- A filling material
- corrosion leads to failure and staining: limited use today
What are the components of gutta percha?
- Zinc oxide (primary ingredient)
- Gutta percha (plasticity)
- Wax/resin (pliability)
- Metal sulfates (radiopacity)
What are the two types of gutta percha points
- 1. Standardized: master cone
- 2. Non-standardized: accessory cones
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
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)
The ideal master cone
- Goes to the working length (WL)
- Gives you tug-back
- Most important and difficult portion of root canal obturation
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
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)
Zinc-oxide-eugenol root canal sealers
- Good seal, easy to handle
- Can decompose in water
Epoxy Resin root canal sealer
- Antimicrobial, long working time, good seal
- Toxicity and insolubility possible
N2; RC2B root canal sealer
- Formaldehyde is active ingredient
- No longer used
Calcium hydroxide sealers
- CaOH2 incorporated into ZOE sealer
- Potential osteogenic effect at the apex
- antimicrobial activity
- Questional long-term stability and toxicity
Glass Ionomer Root canal sealers
- Dentin-bonding agent
- Adequate apical and coronal seal
- Insoluble, retreatement difficult
Worry about post-operative discomfort?
No. It's usual and doesn't indicate obturation success
How do we use radiographs to evaluate obturation?
- Radiolucency: voids
- Denstiy: uniformity
- Continuous taper
- Lateral canals leading to radiographic lesion
What will happen to extruded sealer?
It will be gone in 6 months, along with any lucencies
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)