Seminar 6: Sealers & Obturation Flashcards
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
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
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
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
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
What is GP?
Polymer
Composite material
What are the phases of GP
Alpha
Beta
Gamma
The two crystalline phases of GP are?
Alpha and beta
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)
What percentage does GP shrink after heating
1-2%
Why do you need to ensure constant apical pressure during cooling of heated GP?
To account for volumetric shrinkage
What is the tolerance allowed for GP?
0.5mm up to ISO 25
0.7mm above ISO 25
What is an example of polymer based obturating material
Resilon
How did resilon work?
Combination with a sealer creating a monobloc
What were the downfalls of resilon
Bonding to root dentine remains difficult
Eventually it would breakdown creating voids
Why do bioceramics require water ?
To release CaOH ions
What does the CaOH from calcium silicates react with to form HAP like crystals?
Phosphate ions
Why are calcium silicates so good at encouraging healing?
Immune cells recognise the HAP crystals and allows bone to stick to it
What are sealers ?
Radiopaque luting agent
Used in combination with solid or semi solid materials
To fill voids
Berman 2021
Why do we use sealers ?
Fill voids
Improve seal between filling and root dentine
Lubricate during GP placement
Entomb Bactria
What are some ideal features of sealers?
Radiopaque Bacterial Biocompatible Good handling features Low solubility
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
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
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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
