Canal preparation II Flashcards
1
Q
It is essential that canal preparation does ___________ within the root structure.
A
NOT transport canal
2
Q
Effects of canal curvature
A
- Increased frictional resistance
- Increased compressive forces
- Increased torsional stress
3
Q
Ability of K-file to follow canal curvature is determined by:
A
- Flexibility
- Tip design
- Instrumentation technique
4
Q
List file properties for canal preparation
A
- Rotating flexible files under compression cause them to bend in direction of least resistance (i.e. natural canal curvature)
- Rotating a file that’s too stiff will cause it to fracture in root canal
5
Q
Describe balanced force technique
A
- Rotation of flexible, straight files to prepare curved root canals: can only use K-files, not Hedstrom files
6
Q
What is wet-field instrumentation
A
Everything must be wet with irrigant
7
Q
Describe irrigation role
A
- Tissues solvent
- Suspends debris particles (prevents formation of debris sludge)
- Anti-bacterial activity
- Elimination of smear layer
- Facilitates shaping of canal: chelating effect, lubricant effect
8
Q
Effectiveness of irrigation depends on:
A
- Volume of irigant
- Duration of contact (there are different irrigant for different purposes: e.g. disinfected and chelating agents, don’t alternate between agents)
- Number of solution exchanges: dentine releases a buffer; irrigant only active for couple of minutes in canal
9
Q
List four common irrigants
A
- Sodium hypochlorite (NaOCl)
- chlorohexidine (CHX)
- Ethylene diamine tetra-acetic acid (EDTA)
- RC Prep
10
Q
Describe sodium hypochlorite
A
Primary irrigant
- Dissolves vital and necrotic tissue
- alkaline irrigant - pH 11-12
- Anti-bacterial activity - releases chlorine gas to produce hypochlorous acid: superior anti-bacterial activity to other intra-canal irrigant
- As low as 1.0% NaOCl was effective at removing pulpal remnants and predentine from walls. Higher concentrations (5.25%) showed better anti-bacterial properties (i.e. penetrated deeper into dentine tubules)
- e.g. Miltons solution
11
Q
Describe chlorohexidine (CHX)
A
- Cannot dissolve necrotic tissue
- Anti-fungal
- Can NOT use with NaOCl (forms toxic precipitate)
- Rarely used today
12
Q
Describe EDTA (ethylene diamine tetra-acetic acid)
A
- Chelating agent -> removes calcium ions to demineralized dentine
- Removes smear layer
- Usually combined with ammonium compound (e.g. centrimide)
- Centrimide provides a lubricating effect by reducing surface tension
13
Q
Describe RC Prep
A
- Viscous chelating agent
- Holds debris in suspension
- Use for lubrication
- Contains EDTA, peroxide and lubricant
14
Q
Describe irrigation sequence
A
- EDTA if canal calcified
- NaOCl to remove pulp tissue and disinfect canal
- EDTA periodically to remove accumulated smear layer (do NOT alternate NaOCl and EDTA)
15
Q
What is effective irrigant use?
A
- Employ crown-down technique
- Saturate canal with NaOCl
- EDTA used to only to access and remove smear layer
- Final irrigant with NaOCl or CHX (after final rinse with EDTA)
- NEVER irrigate with irrigating needle tip under pressure
