Seminar 5: CHEMICAL PREP Flashcards
By what two methods do Ultrasonic irrigation and sonic irrigation work?
Acoustic micro streaming
Hydrodynamic Cavitatation
What is Cavitatation?
Formation and implosion of vapour bubbles
What is acoustic microstreaming?
Generation of shear forces in a liquid
What are the two types of cavitation?
Transient and Stable
What is transient cavititation?
Violent collapse of bubbles
What is stable cavitatation?
This involves more volumetric oscillations
What did the results of the study by Macedo et al 2014 show with regards to the use of sonic and ultrasonic irrigation activation?
- Cavitation does not occur around sonic tips
- Smaller taper file is required as this will affect the a amplitude of the waves produced.
- NaOCl can aid cavitation by acting as a surfactant
- Cavitation was seen up to 2mm away from the file tip even in places where th file makes contact with the wall i.e. file making contact with the canal wall does not affect cavitation in UAI.
What was a limitation of study by Macedo et al 2014?
- in this study all preps had a taper of 6% and apical diameter of 0.35mm
- Also they used irritate files and not K files and this would assume as a practitioner you are going to have to get these files in addition to K files
What is a biofilm?
Community of micro-organisms, adhering to walls and held together by ECM
What is LPS?
Lipopolysaccaride which lines the cell membrane of gram negative bacteria.
It is the most potent endotoxin
What are endotoxins?
They are pyrogens and can induce fevers
Bacteria that are free floating are known as?
Planktonic
Apart from the bacteria cell membrane where can LPS be found?
It can be found to have penetrated the dentinal tubules
What areas within the root canal are less susceptible to mechanical debridement?
Isthmuses
ribbons
lateral and accessory canals
oval canals
BY what method to bacteria communicate with each other?
Quorum sensing
What is one of the risks of not completing apical preparation and then temporising?
Medicament cannot reach the apical areas and this leaves more virulent strains e.g. persister cells
How does the cell structure differ between gram positive bacteria and gram negative?
Gram pos: thicker peptidoglycan wall
gram Neg: thin peptidoglycan call wall AND outer membrane containing LPS
In broad terms how do we eliminate biofilms?
Mechanical prep
Chemical prep
Obturation
Coronal seal
What is apical periodontitis ?
Inflammation of the periradicular tissues caused by an interaction of the host immune system usually due to pulpal inflammation but sometimes by occlusal trauma
What is the main purpose of mechanical prep?
This is to facilitate a path for you chemical agents to reach areas which are inaccessible by mechanical instruments
Broadly speaking, according to Gulabivala 2010-what are the three main aims of irrigation?
- Lubricate canal and files
- Dissolve /Disrupt biofilms
- Flush out debris
What are the mechanical goals of irrigation?
-Flushing out debris
What are the biological goals of irrigation?
- Dissolve organic debris (biofilm/pre-dentine/pulp tissue)
- Dissolve inorganic: dentine and smear layer
What are the three phases of irrigation?
Phase 1: Canal negotiation: lubricate the files and flushing-aided by pre flaring
Phase 2: Mechanical shaping./canal enlargement: preventing formation of dentine mud
Phase 3: Delivery of irrigant to un-instrumented surfaces via dynamic irrigation
What are the components of the Smear layer in RCS?
Dentine shavings+ Bacterial cell debris + pulp remnants
On average how thick is the smear layer?
1.5µ
What type of canal areas do you find the smear layer?
Prepared canal walls
What are the two view points regarding the smear layer importance?
- It may provide a substrate for bacteria to feed off
2. May act as a blockade to bacteria trapped in the dentinal tubules so they cannot re enter the pulp space
What are the two layers of the biofilm called?
loose superficial layer
Attached stratum which attaches to dentine forming plugs
What is the difference between gram -ve and gram pos bacteria ?
-ve: thin peptidoglycan cell wall and outer layer as LPS
+ve: thick peptodogclycan cell wall
What methods of eradicating biofilm do we have ?
Mechanical prep
Chemical prep
Obturation
Coronal seal
According to Gulbivala 2002 how much of the canal remains un-instrumented following mechanical prep?
30-50%
What are the challenges to overcome with irrigation ?
Delivering to narrow apical regions
Reaching full thickness depth of biofilm
How many layers to the smear layer are there?
2
Superficial layer
Deeper layer which extends into dentinal tubules with occluding plugs
What are the two schools of thought behind smear layer?
- Can act as a substrate for residual bacteria
2. Provides a physical blockage preventing bacteria from re entering main canal
Commonly used irrigants include
NaOCl
EDTA
CHX
What is the pH of NaOCl?
pH > 11
Strong alkaline
What is the mode of action for NaOCl?
Saponification : this is where tissue dissolution occurs
Neutralisation: enzymes are denatured
Chloramination: chlorine acts as an oxidant oxidising bacterial sulphydryl group
Why does naocl require frequent replenishment during RCT?
Because it reacts with organic matter depleting available chlorine reducing the bacteriacidal effects
What concentration of NaOCl is the minimum for inhibiting bacterial activity ?
Estrela et 2002
1%
What NaOCl concentration is sufficient for antibac and tissue degradation ?
3%
What are the benefits of NaOCl?
Anitbac
Cost effecting
Dissolves organic debris
Penetrates tubules if smear layer removed
What are the cons of NaOCl?
Corrosive
Damaging to patient
Does not remove smear layer
What is the mode of action for EDTA?
Breaks down biofilms by sequestering heavy metal ions which bind bacteria to biofilm
NaOCl can then break down the separate components
What effect does EDTA have on dentine ?
Chelates inorganic components
At What depth does EDTA decalcify dentine to?
50 microns
Needs to be used for 30-60 seconds
What benefit does EDTA have?
Remove smear layer
Penetrate tubules
Dissolved inorganic debris
What disadvantages does EDTA have?
Corrosive
Harmful to patient
Does not dissolve organic debris
What concentration range of NaOCL is typically used ?
1-5.25%
What concentration of EDTA is typically used ?
15-17%
What concentration range of CHX is typically used ?
0.12-2.5%
What are the advantages of CHX?
Substantive
What are the disadvantages of CHX?
Does not dissolve organic or inorganic debris
Stains
Forms precipitate which can block tubules
Does not penetrate tubules
What are the types of canal lubricants?
EDTA eg file eze
Carbamide peroxide eg glyde
What is carbamide peroxide ?
An oxidising agent
What type of flow is there in regular irrigation?
Laminar flow
What type of flow is there in active irrigation?
Turbulent flow
How do chemical agents reach the apical regions after canal prep ?
Diffusion gradient or bulk flow via agitation
What 2 categories exist to overcome irrigation challenges?
Gu et Al 2009
Manual methods
Machine assisted
What are some manual irrigant activation methods ?
Gu et Al 2009
Syringe irrigation with needles (side venting)
Brushes e.g endobrush
Manual dynamic eg GP pumping
What are some machine assisted irrigant activation methods ?
Sonic eg endoactivator
Ultrasonic eg smoothwire
Pressure alternation devices eg Endovac
What are the risks of using brushes to activate irrigation ?
Bristles can break off and push debris apically
Gu et Al 2009
What are the two phenomena posing a challenge to irrigant delivery ?
Stagnation plane
Vapour lock
What is the stagnation plane?
Fluid exchange is limited to 1-1.5mm beyond the needle tip beyond this is the stagnation plane
How can we avoid the stagnation plane?
Agitate and recapitulate
What zone lies beyond the stagnation plane ?
Stagnation zone
What happens if you do not agitate during preparation ?
The stagnation zone becomes saturated with debris forming dentine mud
Which type of needles have longer stagnation planes?
Flat open ended eg plane is longer than 1.5mm
What is Vapor lock?
Trapping of air due to liquid entering a narrow closed channel and release of gaseous byproducts from reacting with hypochlorite
What is the depth of needle penetration dependant upon?
Taper
Apical size
Curvature
What are the most common irrigation need gauge size ?
27G
What size is a 27G needle?
0.4mm
What type of of needles do we use?
Side venting
What are the biological aims of root canal medicaments?
Host: hard tissue genesis, eliminate exudate, analgesic effect
Microbial: kill bacteria and prevent regrowth of bacteria
What are the ideal feature of medicaments ?
No detriment to dentine
No interaction between root canal filling materials
Biocompatible
Antibacterial
What types of inter-visit medicaments exist ?
CaOH Antibiotic Steroid based Phenol based Halide
Name an example of CaOH intervisit paste?
Hypocal
What are the benefits and risks of CaOH pastes
+Good for weeping canals
+Degraded residual organic material
- caustic if extruded
- may have detrimental effect on dentine
What are the benefits and risks of antibiotic pastes for intervisit medicaments
+Non toxic
+antibac
-need a combination of AB
-may get resistance
What are the benefits and risks of steroid pastes for intervisit medicaments
+analgesic
+anti inflam
-risk of bacteriamia as dampens immune response
What are the benefits and risks of phenol based pastes for intervisit medicaments and name an example.
E.g Eugenol
+antibac
-short acting
What are the benefits and risks of Halides pastes for intervisit medicaments
Eg vitapex , IKI
+ antibac
-staining
-may interact with temp fills
What is the pH of CaOH?
12.8
What are the components of CaOH pastes?
CaOH >50%
Barium sulphate >15%
Water / methyl cellulose and antiseptic = remainder
Why is CaOH so effective ?
- Antibac due to OH ions which damaged bacterial walls/enzymes
- Damages LPS
- tissue dissolved in cases of resorption
- physical barrier
- Stimulation of hard tissue genesis
- hygroscopic : absorbs water from exudate which further aids release of OH ions to eliminate exudate
What is the best way to remove CaOH from a canal?
Irrigate with EDTA
since edta is a chelating agent
What is quorum sensing?
Communication method where Bacteria produce and respond to autoinducers impacting gene expression creating an environment that improves longevity of the community as a collective
What are endo brushes?
They are tapered brushes
Bristles on
Able to get into canal irregularities and move debris into the canal to be removed
