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What are the objectives of endo?
- eliminate pain
- locate/access all canals
- remove smear layer
- obturate or fill
- restore for max stability of remaining structure & seal
Which GV Black operative principles apply to endo?
- prep: outline, convenience, removal of carious dentil, finish enamel walls, toilet of cavity
- instrumentation: resistance, retention, toilet of cavity
What chemical is used for endo to handle complex canal systems?
Sodium Hypochloride (30 mins) dissolves tissues
What is the most important phase of the technicals of RCT?
- access cavity preparation (1st step)
- 1. straight line access: flare toward line angle, (removes some dentin)
- 2. conserve tooth structure: know pulpal anatomy, avoid marginal ridges
- 3. unroof pulp chamber
Why is straight line access necessary?
- 1. instrument control
- 2. convenience form
- 3. better cleaning/shaping
- 4. decreased errors
- 5. easier obturation
Why and how should tooth structure be conserved?
- 1. weakens tooth (both overremoval or enamel and dentin)
- 2. outline follows pulpal anatomy
- 3. leave marginal ridges intact
- 4. overprep leads to complications
- 5. prevent accidents
How is outline form prepped?
- 1. measure distance to pulp
- 2. set bur to length (#2 or #4)
- 3. visualize outline form
- 4. unroof chamber
- 5. locate canals
- 6. make walls parallel or slightly DIVERGENT
- 7. finalize with Endo Z bur
What is the importance of unroofing the pulp chamber?
- max visibility
- straight line access
- ease of canal location
- locate & remove pulp horns
What are the common errors of access preparation?
- misorientation: excess dentin removal, weak structure, penetrating bifurcation
- mistaken canal:
- bur separation
What is the most common error for access in anterior teeth?
- perforating the labial/buccal area
- posterior: penetrate bifurcation
What are the pulpal charateristics of maxillary anteriors?
- triangual pulp chambers: 1.5-1.75 mm wide
- less than 10% have 2 roots, most have 1
- exceptions: dens invaginatus (2 roots, 3 possible canals)
What are the pulpal charateristics of mandibular anteriors?
- oval generally but varies
- 40% have 2 canals (maybe only 1 exit orifice)
What are the pulpal charateristics of mandibular canines?
- 1.7% 2 canals
- may be bifurcations
What are the pulpal charateristics of maxillary premolars?
- may have 1,2 or 3 canals (could be tiny)
- 1st: 70-90% 1 canal, 20% 2 canals
- 2nd: 50% 1, 50% 2, 1% 3
What are the pulpal charateristics of mandibular premolars?
- oval w/buccal extension
- 1st: 1,2,3
- 2nd: 1>>2
What are the pulpal charateristics of maxillary molars?
- triangular or rhomboid w buccal angle of external tooth parallel to top of outline form
- 2 foramina 49%
- 1MB or 2MB about 50:50
What are the pulpal charateristics of mandibular molars?
- maintain 2-2.5mm tooth structure
- line over bucco-lincgual goove stops 2mm distal
- C-shaped: wraps around the buccal tooth surface from mesial to distal
- MB and distal usually join
- ML is generally separate
- C-Shaped molars have a lower success rate
- C-Shaped molars are more difficult to instrument
What is working length determination?
- Establish the length or distance from the apex at which the canal preparation and subsequent obturation are to be completed
- Cemento-dentinal junction
- Histologic not a clinical position
- Not always the most constricted place in the canal
- Dependent on
- 1. amount of cementum deposition
- 2. Resorption
- 3. Influenced by age, trauma, ortho movement, periradicular pathology, periodontal disease
- Can exist from slightly short of the radiographic apex to 3-4mm coronal to the radiographic apex
- Average is 0.3mm to 1mm from the radiographic apex
What are the techniques for length determination?
- Conventional radiographs
- Electronic apex locators
- Feeling the apical constriction-unreliable!
- Patient response-painful!
How do electronic apex locators work?
- Based on electrical resistance
- Older units based on direct current-more errors
- Newer units are impedence based - 80 to 95% accurate
- Newer devices use alternating current of two frequencies
- Provide a positive reading when the file tip reaches the PDL or apical foramen
- Decreased resistance results in a sound or visual reading that the apex has been reached
- Should not eliminate the use of radiographs
What are the limitations of radiographs?
- Unable to see root apex due to splinted maxilla
- Zygoma superimposed over maxillary molar
- Mandibular or maxillary tori
- Inability to take radiographs due to anatomic limitations
Do canals always Exit .5mm Short of the Radiographic Apex
No, could cause overinstrumentation/perforation