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BDS3 DMS > 8 - Endodontic materials > Flashcards

8 - Endodontic materials Flashcards

1
Q

What are endodontic instruments?

A
  • used in mechanical phase of chemomechanical disinfection
  • metal files are used to remove soft and hard tissues
  • removes micro-organisms
  • creates space to the disinfectants and medicaments
  • create the shape for obturation
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2
Q

What causes stress to endodontic files?

A

Abrupt changes in shape causes higher stress at that point

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3
Q

What is the elastic limit?

A

The maximum amount of strain that can be applied to the file and it will still return to its original shape

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4
Q

What is plastic deformation?

A

The file will not return to its original shape as the elastic limit has been exceeded

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5
Q

What is plastic limit?

A

The point at which the already deformed file breaks

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6
Q

What is cyclic fatigue?

A
  • work hardening of the file when used in a curved canal
  • generation of tension and compression cycles
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7
Q

What are the different classifications of endodontic instruments?

A
  • manually operated
  • low-speed
  • engine driven NiTi rotary
  • engine driven instruments that adapt to canal shape
  • engine driven reciprocating
  • ultrasonic
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8
Q

What makes up stainless steel?

A
  • alloy of iron, carbon and chromium (can contain nickel)
  • chromium prevents rusting
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9
Q

How are stainless steel files manufactured?

A
  • machined stainless steel wire cut to cross-sectional shape of file
  • twisted (work hardening)
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10
Q

What is nitinol?

A
  • alloy of nickel and titanium
  • super-elasticity stops usual metal properties and proportional strain
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11
Q

What is shape memory?

A

Material scan be deformed and then heated/cooled to return to their original shape

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12
Q

Describe the crystal structure of NiTi.

A
  • has shape memory
  • crystal lattice is affected by temperature
  • in martensite form it is ductile
  • in austenite form it is strong and hard
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13
Q

Define taper.

A

Diameter change along working surface of instrument

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14
Q

Define flute.

A

Groove to collect dentine and soft tissues

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15
Q

Define leading edge.

A
  • aka cutting edge
  • forms and deflects dentine chips
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16
Q

Define land.

A

Surface extending between flutes

17
Q

Define relief.

A

Reduction in surface of land (modifies friction)

18
Q

Define helix angle.

A

Angle cutting axis forms with long axis of file

19
Q

What are irritants used for?

A
  • facilitate removal of debris
  • lubrication
  • dissolution of organic and inorganic material
  • penetration to canal periphery
  • antimicrobial
  • biofilm disruption
20
Q

What is used as an irritant in endodontic treatment?

A

Sodium hypochlorite

21
Q

What factors affect the function of sodium hypochlorite?

A
  • concentration
  • volume
  • contact time
  • mechanical agitation
22
Q

What is the smear layer?

A
  • organic pulpal material and inorganic dentinal debris
  • superficial and packing into tubules
  • the contamination interferes with disinfection
  • prevents sealer penetrating into tubules
23
Q

How do you remove the smear layer?

A
  • 17% EDTA
  • 10% citric acid
  • sonic and ultrasonic irrigation
24
Q

What happens if irritants are mixed?

A
  • can interact and become cytotoxic and carcinogenic
  • EDTA and sodium hypochlorite should never mix and the canal should be rinsed between use
25
Q

What are the ideal properties of an obturation material? (9)

A
  • easily manipulated
  • dimensionally stable
  • seal canal laterally and apically
  • nonirritant
  • unaffected by tissue fluid
  • inhibit bacterial growth
  • radiopaque
  • sterile
  • doesn’t cause discolouration
26
Q

What is gutta-percha?

A
  • obturation material
  • produced from juice of tress of sapodilla family
  • natural rubber of monomer isoprene
  • beta phase is used commonly in dentistry
27
Q

How is beta phase GP produced?

A
  • alpha phase is naturally occurring
  • heated to 65 degrees
  • cooled rapidly to recrystallise to beta phase
28
Q

What makes up the GP cones?

A

20% GP
65% zinc oxide
10% radiopacifier
5% plasticiser

29
Q

What is the role of sealer material?

A
  • seals space between dentinal wall and core material
  • fills voids and irregularities in canal and lateral canals
  • lubricates during obturation
30
Q

What are the ideal properties of a sealer? (9)

A
  • tackiness to provide good adhesion
  • slow set
  • no shrinkage on setting
  • hermetic seal
  • radiopacity
  • easily mixed
  • non-staining
  • bacteriostatic
  • insoluble in tissue fluid
31
Q

What are different sealers?

A
  • zinc oxide and eugenol
  • GI
  • resin
  • calcium silicate
  • medicated
32
Q

Describe zinc oxide and eugenol as a sealer material.

A
  • can be modified with germicides and corticosteroids
  • antimicrobial effects
  • free eugenol can act as irritant
33
Q

Describe GI as a sealer material.

A
  • dentine bonding properties
  • removal for retreatment is difficult
  • minimal antimicrobial activity
  • not widely used
34
Q

Describe resin sealers.

A
  • epoxy resin or dual cure resin
  • 2 pastes mixed together
  • slow set of 8 hours
  • good sealing ability
  • good flow
  • initial toxicity subsides after 24 hours
35
Q

Describe calcium silicate sealers.

A
  • high pH during initial 24 hour set
  • hydrophilic
  • good biocompatibility
  • no setting shrinkage
  • v good seal
  • quick set 3-4 hours
  • difficult to retreat
36
Q

Describe medicated sealers.

A
  • not used
  • contain paraformaldehyde, lead and mercury
  • severe and permanent toxic effects
37
Q

What can pulp capping materials be used for?

A
  • pulp cap
  • pulpotomy
  • furcation perforation repair
  • root resorption repair
  • lateral perforation repair
  • apexification
  • apicoectomy
38
Q

What is MTA?

A
  • mineral trioxide aggregate
  • bioceramic cement
  • encourages tissue response and hydroxyapatite formation
39
Q

Give an example of MTA.

A
  • tricalcium silicate
  • bismuth oxide

BDS3 DMS (9 decks)

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