Endodontics Flashcards
Pulp capping materials
- calcium hydroxide
- dentine bonding agents
- calcium silicate-based cements
Materials for obturating points
- metal points
- gutta percha
- thermoplastic polymer point
Canal sealer cements
- calcium hydroxide
- ZOE
- resins
- GICs
- polydimethylsiloxanes
- CSCs
CSCs are similar to …
Portland cement
Different constitutions of calcium silicate-based cement
- powder and liquid in a 3:1 ratio
- powder
- liquid
Explain powder version of CSC
- all contain calcium silicate
- some contain other components like calcium aluminate
- CaSO4.2H2O extends WT and ST
- bismuth oxide is a radio-opacifier
Explain liquid version of CSC
- ultra pure-water used in all products
- calcium chloride added to some products to accelerate setting reaction
CSC are acidic/alkaline
Explain
- alkaline
- pH10 rises to around 12.5
- neutralizes acids
- antibacterial/biocompatible
When CSC powder is mixed with water, it forms what?
a sandy mixture
Setting of CSC
- in presence of moisture
- 2(3Ca3OSiO4) +6H2O ->3CaO.2SiO2.3H2O + 3Ca(OH)2
- with 4 waters, makes 1 calcium hydroxide
- this is the bi-product
- initial set takes 15 mins
- final set over 25
Objectives of endodontic treatment
- provide a clean canal
- provide apical seal
- provide coronal seal
Why do we provide a clean canal in endodontics?
- reduce bacteria to non-pathogenic levels
- irrigans include 1-10% NaClO, EDTA, citric acid
Why do we provide an apical seal in endodontics?
- prevent fluid getting into canal - potential bacterial nutrients
- prevent irritants entering periapical tissues
Why do we provide a coronal seal in endodontics?
- prevent recontamination due to ingress of micro-organisms
Current approach to endodontics to reach all goals
- obturating points
- canal sealer
Metals used in metal points
- gold
- silver
- lead
- tin
- copper
- titanium
Which is the most popular metal in metal points?
Why?
Still?
- silver
- bactericidal, rigid
- poor adaption - relies on cement to make seal
- corrosion - tissue discolouration
- not used as much anymore
Explain Gutta Percha points
- used for over 100 years
- form of natural rubber (isoprene)
2 types of isoprene
- cis
- trans
Explain cis-isoprene
(isoprene/ cis-isoprene)
- amorphous, flexible, soft
- needs crosslinks to harden (vulcanisation with sulphur) - thermoset
Explain trans-isoprene
- gutta percha#
- crystalline (around 60%), hard, rigid
- thermoplastic - softens around 60-65 degrees, melts around 100 degrees
- oxidises on light exposure and becomes brittle
Difference between cis and trans isoprene
- CH2-CH2 bond at bottom in cis, H and CH3 on top not bonded
- CH2-CH2 bond in trans on top with 2 H other side not bonded
Explain the beta-phase Gutta Percha
- crystalline
- formed by rapid cooling from high temp
- used for cold packing
Explain alpha-phase of gutta percha
- denser
- formed by slow cooling from high temp
- used for thermal packing
Composition of Gutta Percha
- 19-22% gutta percher
- 59-75& zinc oxide
- 1-17% heavy metal salt
- 1-4% wax/resin
Role of Gutta percha
rubberR
Role of zinc oxide
filler
Role of heavy metal salt
radio-opacifier
Role of wax/resin
plasticiser
Ideal biocompatibility of canal sealers
- no inflam response if contacts vital tissues
- bactericidal/bacteriostatic
Ideal sealing properties of canal sealers
- bacterial barrier more important than physical
- easy to remove in failure
Ideal physical properties of canal sealer
- flow to thin film thickness
- insoluble
- radio-opaque
Non-setting calcium hydroxide cements apear how?
- slurry paste
- calcium hydroxide and water
- add methylcellulose for viscosity
Properties of non-setting calcium hydroxide cements
- can be removed - useful for inter-visit medication, apexifications
- bactericidal - high pH against persistant infection
- inhibits osteoclasts - high pH arrests root resorption
- high viscosity - completely fill canal
How does setting calcium hydroxide cement appear?
- paste-paste system
- many ingredients similar to traditional cement
- long working time
Properties of calcium hydroxide cements
- high pH - bactericidal, biocompatible
- high solubility - low strength
How is zinc oxide eugenol canal sealer similar to traditional cements?
- smaller particle size - improve flow
- porous
- decompose over time (zinc oxide and eugenol leach)
- resins added to decrease solubility
- low strength - effect of pores
- antimicrobial
- inflammatory - prevent leakage beyond apex
Explain zinc oxide eugenol canal sealer as a powder liquid system
- Rickert’s formulation
- contained silver which discolours dentine
- thick film, short working time
- and Grossman’s sealer - replace silver with bismuth or barium, long working time
Explain paste-paste system of zinc oxide eugenol canal sealer
- e.g Tubil-seal
- thin film
- short working time
Resins are formulated to have … properties
Explain
- ideal
- smooth paste with good flow and sealing
- dimensionally stable, low shrinkage
- long WT, short ST
- adhesion to dentine and obturating materials
- good biocompatibility (initially toxic but long term antibacterial)
- potential for allergies however
2 most common resins
- epoxy-amine resin (AH plus)
- polyvinyl resin (Diaket)
Features of epoxy-amine resin
- long working time
- good viscosity
- thin film
Features of polyvinyl resin
- rapid setting
- viscous and sticky
- difficult to manipulate
CSCs are similar to what material?
pulp capping material
Features of CSCs
- biocompatible (tertiary dentine deposition)
- good seal (coronal and apex)
- good WT and long ST (may need subsequent appointments)
- difficult to manipulate (viscosity)
- can lead to tooth staining (metallic adhesives the reason)
- expensive
Features of GICs
- low shrinkage
- short WT
- thick films
Polydimethylsiloxanes are similar to …
- impression material
- addition silicone
Features of polydimethylsiloxanes
- good flow
- thin films
- dimensionally stable
- biocompatible
- no bond to dentine
- not antibacterial
