Seminar 6: Sealers & Obturation Flashcards by Ani Hsn

Acc to NOUM and CHANDLER 2002 What are the two functions of temp fills?

prevent seepage of canal medicaments
provide adequate seal preventing ingression of bacteria and organic materials from oral cavity

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Acc to NOUM and CHANDLER 2002, what are the benefits of placing cotton wool in access cavities?

-prevents risk of damage to tooth structure upon re-entering
-prevents material being lodged into canals
-

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Acc to NOUM and CHANDLER 2002, what are the disadvantages of using cotton pellets?

reduced thickness of temp material
compromise stability of temp rest as acts as a cushion
compromise adaptation to walls
cotton fibres may adhere to cavity wall acting as a wick causing contamination

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Acc to NOUM and CHANDLER 2002, how should cotton pellets be placed?

-small pellet over orifice only

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What is obturation?

Impermeable seal
Entomb residual bacteria
Prevent re contamination

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What effect does coronal restoration have on success ?

Chu et al 2005
Extra coronal had higher success rate
Swartz et al 1983
Higher success for satisfactory restorations than non satisfactory

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What types of obturating materials are used?

Solid forms:
Historically silver points
GP
Polymer based eg resilon

Pastes/cements:
Historically: RF paste: formaldehyde + resorcinol white crystalline powder. Benefits: destroys infection and ‘resinifies’ residual pulp tissues, but it also obturates the canals as it sets ‘brick’ hard, preventing further reinfection.
advantage: bactericidal effect, is that it permits incomplete pulp tissue removal at the stage of cleaning and shaping
Calcium silicate cements eg MTA

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What is GP?

Polymer

Composite material

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What are the phases of GP

Alpha
Beta
Gamma

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The two crystalline phases of GP are?

Alpha and beta

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What are the organic and inorganic components to GP?

Organic : polymer (cis and trans isomers) and wax/resin (reduces brittleness)
Inorganic : ZNO (enhances cross linking between polymer chains) and Metal sulphate (opacifiers)

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What percentage does GP shrink after heating

1-2%

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Why do you need to ensure constant apical pressure during cooling of heated GP?

To account for volumetric shrinkage

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What is the tolerance allowed for GP?

0.5mm up to ISO 25
0.7mm above ISO 25

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What is an example of polymer based obturating material

Resilon

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How did resilon work?

Combination with a sealer creating a monobloc

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What were the downfalls of resilon

Bonding to root dentine remains difficult

Eventually it would breakdown creating voids

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Why do bioceramics require water ?

To release CaOH ions

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What does the CaOH from calcium silicates react with to form HAP like crystals?

Phosphate ions

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Why are calcium silicates so good at encouraging healing?

Immune cells recognise the HAP crystals and allows bone to stick to it

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What are sealers ?

Radiopaque luting agent
Used in combination with solid or semi solid materials
To fill voids
Berman 2021

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Why do we use sealers ?

Fill voids
Improve seal between filling and root dentine
Lubricate during GP placement
Entomb Bactria

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What are some ideal features of sealers?

Radiopaque 
Bacterial 
Biocompatible 
Good handling features
Low solubility

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According to McMichen et al 2004 what are the main groups of sealers?

Rosin-Chloroform (not used)
ZnO eugenol : antimicrbial activity and good working time (tubliseal)
GIC: adhered to dentine but can dissolve before setting (ketac-endo)
CaOH : uncertain sealing ability, antibac (sealapex)
Polymer based eg AH plus , good flow but can make retreatment Difficult due to low solubility

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What are the advantages of GP

Radiopaque Readily available and inexpensive Softened by heat and solvents Adapts to irregularities

What are the disadvantages of GP?

Cytotoxic No adhesive qualities Can evoke foreign body reaction esp in particulate form

What are the benefits of silver points ?

Dimensionally stable | Radiopaque

What are the risks of silver points

Corrode leading to leakage | Lots of voids and heavily reliant upon sealer

What are the two types of extrusion that can occur in obturating ?

Over filled: well compacted but long | Over extended : voids and long

What are some of the ideal features of sealers set out by Grossman 1981?

BRENNS 11 in total Radiopaque Easy to mix No shrinkage when set Bacteriostatic Non irritant Soluble for common Solvents ```

What are the risks of ZNO sealers ?

May stain Inhibits polymerisation of resins Can have prolonged inflammation

Why was AH 26 stopped?

Release formaledehyde | Now we used AH +

What are the downsides of resin sealers ?

Root canal has a high C factor increasing stresses

What is the benefit of using orifice plugs?

Yamauchi et al 2006 | Orifice plugs in dogs found that least amount of inflam seen in those with IRM plugs

What are the risks of LC GIC over GIC

Less fluoride release and reduced bond strength

What is the benefit of using CaPhosphate eg cavit as a temp?

Easy to manipulate Good marginal seal

What is the risk of using CaPhosphate eg cavit as a temp?

Water sorption leading to poor sealing ability | Better for small cavities

What natural substance is GP made from?

Coagulated sap of tropical trees found in South America, Singapore and Indonesia (amongst others)

Which other material is the structure of GP similar to?

Natural rubber (cis poly isomer of polyisoprene) GP (trans poly isomer of polyisoprene)

What are the names of the chemical groups in the trans GP formation?

CH2 Methylene

What colour is GP naturally ?

White

What crystalline form does GP naturally occur in?

Alpha

What temperature does alpha GP become amorphous and melted?

>65 degrees Celsius

What happens if you cool heated GP quickly ?

B form recrystallises

Most commercially available GP is in what form?

Beta

What happens if you cool heated GP slowly?

Alpha form recrystallises

What temperature does beta form become amorphous?

56 oC

What at the properties of alpha GP?

Brittle at room temp Low viscosity when heated

Which obturation methods work best with alpha GP?

Heated/warm techniques

What are the properties of beta GP?

Flexible at room temp High viscosity when heated

What obturation methods work well with Beta GP?

Cold later compaction

What factors makes GP more brittle?

Light exposure Air exposure

What chemical process happens to make GP more brittle ?

Oxidation

At what temperature does GP begin to degrade ?

95 degrees celsius

What is the benefit of zinc oxide in GP?

Increases brittleness

What physical forms of GP exist ?

-Solid core GP points (ISO and Non ISO) -Thermo-plasticised -Cold flowable GP

How does cold flowable GP work?

Powder form GP and mixed with a resin sealer in a capsule

What specific modifications exist to GP to enhance its sealing and therapeutic effects?

-Non ISO -Surface modified eg resin coated/GI coated -Medicated GP eg CaOH/CHX -Nanoparticles enriched eg Silver

What is the benefit of CHX impregnated GP points ?

-CHX is a positive charged molecule and interacts with the negative charged phosphate groups on bacterial cell walls -CHX can penetrate bacterial cell wall and affect osmotic equilibrium

What two microbial species is CHX impregnated GP points effective against ?

Candida albicans E feacalis

What is the benefit of the silver nano particles in GP?

Silver ions have a long term sustained release which are antibacterial and low bacterial resistance

How does glass ionomer bond with dentine ?

Ionic bond

What is the benefit of using a glass ionomer coated GP cone ?

It is not degraded by any residual NaOCl

Other than obturation what other dental uses for GP are there ?

Pulp tests: heated GP GP tracer Dynamic irrigation Temporisation of access cavity

Define microleakage

clinically undetectable passage of bacteria, fluids, molecules or ions between a cavity wall and the restorative material. Shrethsta et al 2010

What sealer was resilon used in conjunction with?

Epiphany resin Primer which exposed the collagen fibres of dentine Sealer which bonded the dentine to the resilon forming the monobloc

What was the issue with resilon and epiphany?

The bond formed was susceptible to hydrolysis overtime causing voids to form