Seminar 5: CHEMICAL PREP

Question 1

By what two methods do Ultrasonic irrigation and sonic irrigation work?

Answer 1

Acoustic micro streaming

Hydrodynamic Cavitatation

Question 2

What is Cavitatation?

Answer 2

Formation and implosion of vapour bubbles

Question 3

What is acoustic microstreaming?

Answer 3

Generation of shear forces in a liquid

Question 4

What are the two types of cavitation?

Answer 4

Transient and Stable

Question 5

What is transient cavititation?

Answer 5

Violent collapse of bubbles

Question 6

What is stable cavitatation?

Answer 6

This involves more volumetric oscillations

Question 7

What did the results of the study by Macedo et al 2014 show with regards to the use of sonic and ultrasonic irrigation activation?

Answer 7

• 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.

Question 8

What was a limitation of study by Macedo et al 2014?

Answer 8

• 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

Question 9

What is a biofilm?

Answer 9

Community of micro-organisms, adhering to walls and held together by ECM

Question 10

What is LPS?

Answer 10

Lipopolysaccaride which lines the cell membrane of gram negative bacteria.
It is the most potent endotoxin

Question 11

What are endotoxins?

Answer 11

They are pyrogens and can induce fevers

Question 12

Bacteria that are free floating are known as?

Answer 12

Planktonic

Question 13

Apart from the bacteria cell membrane where can LPS be found?

Answer 13

It can be found to have penetrated the dentinal tubules

Question 14

What areas within the root canal are less susceptible to mechanical debridement?

Answer 14

Isthmuses
ribbons
lateral and accessory canals
oval canals

Question 15

BY what method to bacteria communicate with each other?

Answer 15

Quorum sensing

Question 16

What is one of the risks of not completing apical preparation and then temporising?

Answer 16

Medicament cannot reach the apical areas and this leaves more virulent strains e.g. persister cells

Question 17

How does the cell structure differ between gram positive bacteria and gram negative?

Answer 17

Gram pos: thicker peptidoglycan wall

gram Neg: thin peptidoglycan call wall AND outer membrane containing LPS

Question 18

In broad terms how do we eliminate biofilms?

Answer 18

Mechanical prep
Chemical prep
Obturation
Coronal seal

Question 19

What is apical periodontitis ?

Answer 19

Inflammation of the periradicular tissues caused by an interaction of the host immune system usually due to pulpal inflammation but sometimes by occlusal trauma

Question 20

What is the main purpose of mechanical prep?

Answer 20

This is to facilitate a path for you chemical agents to reach areas which are inaccessible by mechanical instruments

Question 21

Broadly speaking, according to Gulabivala 2010-what are the three main aims of irrigation?

Answer 21

• Lubricate canal and files
• Dissolve /Disrupt biofilms
• Flush out debris

Question 22

What are the mechanical goals of irrigation?

Answer 22

-Flushing out debris

Question 23

What are the biological goals of irrigation?

Answer 23

• Dissolve organic debris (biofilm/pre-dentine/pulp tissue)

- Dissolve inorganic: dentine and smear layer

Question 24

What are the three phases of irrigation?

Answer 24

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

Question 25

What are the components of the Smear layer in RCS?

Answer 25

Dentine shavings+ Bacterial cell debris + pulp remnants

Question 26

On average how thick is the smear layer?

Answer 26

1.5µ

Question 27

What type of canal areas do you find the smear layer?

Answer 27

Prepared canal walls

Question 28

What are the two view points regarding the smear layer importance?

Answer 28

1. 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

Question 29

What are the two layers of the biofilm called?

Answer 29

loose superficial layer | Attached stratum which attaches to dentine forming plugs

Question 30

What is the difference between gram -ve and gram pos bacteria ?

Answer 30

-ve: thin peptidoglycan cell wall and outer layer as LPS | +ve: thick peptodogclycan cell wall

Question 31

What methods of eradicating biofilm do we have ?

Answer 31

Mechanical prep Chemical prep Obturation Coronal seal

Question 32

According to Gulbivala 2002 how much of the canal remains un-instrumented following mechanical prep?

Answer 32

30-50%

Question 33

What are the challenges to overcome with irrigation ?

Answer 33

Delivering to narrow apical regions | Reaching full thickness depth of biofilm

Question 34

How many layers to the smear layer are there?

Answer 34

2 Superficial layer Deeper layer which extends into dentinal tubules with occluding plugs

Question 35

What are the two schools of thought behind smear layer?

Answer 35

1. Can act as a substrate for residual bacteria | 2. Provides a physical blockage preventing bacteria from re entering main canal

Question 36

Commonly used irrigants include

Answer 36

NaOCl EDTA CHX

Question 37

What is the pH of NaOCl?

Answer 37

pH > 11 | Strong alkaline

Question 38

What is the mode of action for NaOCl?

Answer 38

Saponification : this is where tissue dissolution occurs Neutralisation: enzymes are denatured Chloramination: chlorine acts as an oxidant oxidising bacterial sulphydryl group

Question 39

Why does naocl require frequent replenishment during RCT?

Answer 39

Because it reacts with organic matter depleting available chlorine reducing the bacteriacidal effects

Question 40

What concentration of NaOCl is the minimum for inhibiting bacterial activity ?

Answer 40

Estrela et 2002 | 1%

Question 41

What NaOCl concentration is sufficient for antibac and tissue degradation ?

Answer 41

3%

Question 42

What are the benefits of NaOCl?

Answer 42

Anitbac Cost effecting Dissolves organic debris Penetrates tubules if smear layer removed

Question 43

What are the cons of NaOCl?

Answer 43

Corrosive Damaging to patient Does not remove smear layer

Question 44

What is the mode of action for EDTA?

Answer 44

Breaks down biofilms by sequestering heavy metal ions which bind bacteria to biofilm NaOCl can then break down the separate components

Question 45

What effect does EDTA have on dentine ?

Answer 45

Chelates inorganic components

Question 46

At What depth does EDTA decalcify dentine to?

Answer 46

50 microns | Needs to be used for 30-60 seconds

Question 47

What benefit does EDTA have?

Answer 47

Remove smear layer Penetrate tubules Dissolved inorganic debris

Question 48

What disadvantages does EDTA have?

Answer 48

Corrosive Harmful to patient Does not dissolve organic debris

Question 49

What concentration range of NaOCL is typically used ?

Answer 49

1-5.25%

Question 50

What concentration of EDTA is typically used ?

Answer 50

15-17%

Question 51

What concentration range of CHX is typically used ?

Answer 51

0.12-2.5%

Question 52

What are the advantages of CHX?

Answer 52

Substantive

Question 53

What are the disadvantages of CHX?

Answer 53

Does not dissolve organic or inorganic debris Stains Forms precipitate which can block tubules Does not penetrate tubules

Question 54

What are the types of canal lubricants?

Answer 54

EDTA eg file eze | Carbamide peroxide eg glyde

Question 55

What is carbamide peroxide ?

Answer 55

An oxidising agent

Question 56

What type of flow is there in regular irrigation?

Answer 56

Laminar flow

Question 57

What type of flow is there in active irrigation?

Answer 57

Turbulent flow

Question 58

How do chemical agents reach the apical regions after canal prep ?

Answer 58

Diffusion gradient or bulk flow via agitation

Question 59

What 2 categories exist to overcome irrigation challenges?

Answer 59

Gu et Al 2009 Manual methods Machine assisted

Question 60

What are some manual irrigant activation methods ?

Answer 60

Gu et Al 2009 Syringe irrigation with needles (side venting) Brushes e.g endobrush Manual dynamic eg GP pumping

Question 61

What are some machine assisted irrigant activation methods ?

Answer 61

Sonic eg endoactivator Ultrasonic eg smoothwire Pressure alternation devices eg Endovac

Question 62

What are the risks of using brushes to activate irrigation ?

Answer 62

Bristles can break off and push debris apically | Gu et Al 2009

Question 63

What are the two phenomena posing a challenge to irrigant delivery ?

Answer 63

Stagnation plane Vapour lock

Question 64

What is the stagnation plane?

Answer 64

Fluid exchange is limited to 1-1.5mm beyond the needle tip beyond this is the stagnation plane

Question 65

How can we avoid the stagnation plane?

Answer 65

Agitate and recapitulate

Question 66

What zone lies beyond the stagnation plane ?

Answer 66

Stagnation zone

Question 67

What happens if you do not agitate during preparation ?

Answer 67

The stagnation zone becomes saturated with debris forming dentine mud

Question 68

Which type of needles have longer stagnation planes?

Answer 68

Flat open ended eg plane is longer than 1.5mm

Question 69

What is Vapor lock?

Answer 69

Trapping of air due to liquid entering a narrow closed channel and release of gaseous byproducts from reacting with hypochlorite

Question 70

What is the depth of needle penetration dependant upon?

Answer 70

Taper Apical size Curvature

Question 71

What are the most common irrigation need gauge size ?

Answer 71

27G

Question 72

What size is a 27G needle?

Answer 72

0.4mm

Question 73

What type of of needles do we use?

Answer 73

Side venting

Question 74

What are the biological aims of root canal medicaments?

Answer 74

Host: hard tissue genesis, eliminate exudate, analgesic effect Microbial: kill bacteria and prevent regrowth of bacteria

Question 75

What are the ideal feature of medicaments ?

Answer 75

No detriment to dentine No interaction between root canal filling materials Biocompatible Antibacterial

Question 76

What types of inter-visit medicaments exist ?

Answer 76

``` CaOH Antibiotic Steroid based Phenol based Halide ```

Question 77

Name an example of CaOH intervisit paste?

Answer 77

Hypocal

Question 78

What are the benefits and risks of CaOH pastes

Answer 78

+Good for weeping canals +Degraded residual organic material - caustic if extruded - may have detrimental effect on dentine

Question 79

What are the benefits and risks of antibiotic pastes for intervisit medicaments

Answer 79

+Non toxic +antibac -need a combination of AB -may get resistance

Question 80

What are the benefits and risks of steroid pastes for intervisit medicaments

Answer 80

+analgesic +anti inflam -risk of bacteriamia as dampens immune response

Question 81

What are the benefits and risks of phenol based pastes for intervisit medicaments and name an example.

Answer 81

E.g Eugenol +antibac -short acting

Question 82

What are the benefits and risks of Halides pastes for intervisit medicaments

Answer 82

Eg vitapex , IKI + antibac -staining -may interact with temp fills

Question 83

What is the pH of CaOH?

Answer 83

12.8

Question 84

What are the components of CaOH pastes?

Answer 84

CaOH >50% Barium sulphate >15% Water / methyl cellulose and antiseptic = remainder

Question 85

Why is CaOH so effective ?

Answer 85

- 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

Question 86

What is the best way to remove CaOH from a canal?

Answer 86

Irrigate with EDTA | since edta is a chelating agent

Question 87

What is quorum sensing?

Answer 87

Communication method where Bacteria produce and respond to autoinducers impacting gene expression creating an environment that improves longevity of the community as a collective

Question 88

What are endo brushes?

Answer 88

They are tapered brushes Bristles on Able to get into canal irregularities and move debris into the canal to be removed