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BDS3 CDS > endodontics > Flashcards

endodontics Flashcards

1
Q

problems that can arise with post crowns - 4

A

perforation
core fracture
root fracture or crack
post fracture

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2
Q

clinical assessment of a RCT treated tooth involves assessing…

A

coronal seal - leakage, caries?

amount of remaining tooth - ferrule

if tooth is restorable

sinus, swelling, TTP, mobility, pocketing

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3
Q

when radiographically assessing a RCT what do you look for

A

Root filling - length, voids?
unfilled or missed canals
shape of canals
bone support
pathology - radiolucency or resorption or perforations

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4
Q

endo complications

A

fractured instrument

perforation

lack or no ferrule after RCT

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5
Q

give a cause of RCT failure

A

coronal micro leakage - ingress of micro-organisms into RC system

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6
Q

restoration option for an anterior tooth with intact marginal ridges

A

veneer or composite restoration

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7
Q

restoration options for an anterior tooth with intact marginal ridges and discoloured crown

A

bleaching
veneer
crown

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8
Q

restoration options for an anterior tooth with intact marginal ridges and discoloured crown

A

bleaching
veneer

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9
Q

restoration options for anterior teeth with marginal ridges destroyed

A

core build up with crown
post crown.

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10
Q

what is the function of a post and a core

A

gains intra-radicular support for a definitive restoration

core provides retention for crown

post provides retention for core

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11
Q

true or false, tooth is weakened when prepared for a post

A

true

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12
Q

what length of GP is required to be left apically for post placement

A

3-5mm

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13
Q

how wide should a post be

A

no more than 1/3 of the width of the narrowest point of root

at least 1mm of circumferential coronal dentine present

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14
Q

minimum post length to crown ratio

A

1:1

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15
Q

what would be sufficient alveolar support for a post and core

A

the alveolar bone is half the length of post at least

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16
Q

what is a ferrule

A

dentine collar - encirclement of 1-2mm of vertical axial tooth structure within walls of crown

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17
Q

what is the purpose of ferrule

A

prevents tooth fracture

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18
Q

for post placement what height and width of ferrule is required

A

at lest 1.5mm height and width

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19
Q

post materials - 3

A

metal - cast metal, stainless steel
ceramic - zirconia
fibre - glass, carbon

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20
Q

what are the two shapes of post

A

tapered
parallel (more retentive)

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21
Q

what is a Nayyar core

A

RCT removed and amalgam packed into the canals, tooth is built up

AVOID

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22
Q

core materials - 2

A

composite - good aesthetics, bonds to tooth

amalgam - retention required and can’t prep straight away, needs to set for 24hrs

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23
Q

what is a core build up

A

internal part of tooth is built up with a restorative material to provide retention and resistance for permanent restoration

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24
Q

advantages of prefabricated posts - 3

A

no impressions or lab visit
immediate prep of core chair side
large selection of design and material

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25
Q

advantage and disadvantage of custom post

A

unified post and core

2 visits required - impression and fit, risk of contamination

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26
Q

advantage of parallel sided post

A

avoids wedging

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27
Q

how to prevent rotation of post in absence of coronal dentine

A

anti rotation notch - small vertical groove in canal

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28
Q

taper of a core

A

6 degrees

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29
Q

why are posts not routinely used in molars

A

disadvantages outweigh advantages
narrow roots - post prep may perforate
core retention can be optioned from undercuts and bonding agents

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30
Q

if there is not coronal tissue on a molar, what canal would you insert a short post into

A

largest and straightest RC

distal mandibular
palatal maxillary

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31
Q

why is cuspal protection important - 3

A

prevents catastrophic fracture
maintains coronal seal
prevents microbial ingress

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31
Q

why is cuspal protection important - 3

A

prevents catastrophic fracture
maintains coronal seal
prevents microbial ingress

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32
Q

design objectives of root canal

A

continuously tapering funnel shape
apical foramen in original position
apical foramen as small as possible

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33
Q

instrument to detect canal orifice

A

DG16 endodontic explorer

34
Q

where should GP be cut

A

orifice or just below orifice level

35
Q

what material are k files made of

A

stainless steel

flexible k files nickel titanium

36
Q

motions you can use an endo file

A

filing
reaming
watch winding
balanced force
envelope of motion

37
Q

which endo file technique can be described as back and forward oscillation of 30 and 60 degrees with light apical pressure

A

watch winding

38
Q

which endo file technique can be described as 90 degree turn clockwise with apical pressure then 180 degree counter clockwise turn with continued pressure

A

balanced force technique

39
Q

what is cyclic fatigue

A

when rotating file in a curvature there is a generation of compression and tension cycles on each side of the file - leads to failure

40
Q

cross section of reciprocal file

A

s shape

41
Q

what angles of rotation does reciprocal use

A

150 CC
then
30 CW

42
Q

signs of RCT failure

A

clinical signs and symptoms

enlargement of existing periradicular lesion

development of new periradicular lesion

persistence of periradicular lesion associated with tooth that had RCT at least 4 years ago

43
Q

indications for non surgical RC re treatment

A

intra radicular infection

new complex restoration with a technically poor RCT

loss of coronal seal

44
Q

solvent that can be used to soften and help remove GP for re treatment

A

eucalyptus oil - more GP and sealer left behind if use solvent though

45
Q

what would you write on a lab prescription for a post and core

A

please contract an post and core

para post - colour

core 6 degree taper and 2mm space in occlusion for crown

46
Q

What factors would you consider when deciding on post options?

A

root canal anatomy - narrow and curved will need a custom post, prefabricated can be used in straight and wider

remaining tooth structure - requires minimum ferrule of 1.5mm

aesthetics - tooth coloured post in aesthetic areas

47
Q

What factors do you consider important when deciding if a tooth is restorable?

A

remaining tooth structure - ferrule

RCT status

fractures

bone levels

48
Q

what is stress in DMS

A

deforming force measures across given area

=F/A

49
Q

what is strain

A

response of a material to stress

50
Q

what is the elastic limit

A

a set valid representing the maximum strain that when applied to a file allows the file to return to original dimensions

51
Q

what is elastic deformation

A

reversible deformation that does not exceed elastic limit

52
Q

what is plastic deformation

A

permanent deformation occurring when elastic limit exceeded - the point that a plastic instrument will fracture

53
Q

two ways Endodontics instrument can fail

A

cyclic fatigue

torsional fatigue

54
Q

what is torsional fatigue

A

instrument in canal binds to dentine and rotated

bound portion does not rotate and the other portion does leading to torsion and elastic limit is exceeded

leads to failure

55
Q

how do you prevent endo instrument fracture

A

create a manual guide path - creates space for tip

straight line access

gentle pressure and constantly moving

56
Q

what component of stainless steel prevents rusting

A

chromium - forms passivation layer of chromium oxide

57
Q

what step in manufacture of endo files does work hardening occur

A

the twisting of the files

58
Q

what is work hardening

A

strengthening of a material by plastic deformation

dislocates crystalline lattice

dislocations create resistance to further dislocations

59
Q

how does NI-Ti not conform to typical properties of metals

A

displays super elasticity - application of stress does not result in usual proportional strain

60
Q

what is the effect of temperature on NiTi crystal structure

A

martensite and austenite are temperature dependent

crystal attic structure is altered by temperature

martensite form is soft, ductile - room temp and below

austenitic form is strong and hard - warmer temperatures

61
Q

what is the taper of an instrument

A

diameter change along working surface

62
Q

taper of a K file

A

2%

63
Q

function of flute on instruments

A

grooves to collect dentine and soft tissues

64
Q

what is the helix angle

A

angle cutting axis forms with long axis of file

65
Q

role of an irritant in Endodontics

A

removal of debris
lubrication
antimicrobial - kill bacteria and viruses

66
Q

primary irritant for endo

A

NaOCL
sodium hypochlorite 3%

67
Q

what is responsible for antibacterial activity in sodium hypochlorite

A

HOCl

hypochlorus acid

68
Q

factors important for hypochlorite function

A

concentration
volume
contact
mechanical agitation
exchange

69
Q

why is it important to remove the smear layer before obturation

A

prevents sealer penetration

interferes with disinfection

70
Q

what is the smear layer

A

organic pulp and inorganic dentine debris

71
Q

what do we use to remove smear layer

A

17% EDTA

72
Q

irritants can interact - give an example of a consequence of irritant interaction

A

interaction with NAOCl forms para chloroaniline

cytotoxic and carcinogenic

73
Q

ideal properties of an obturation material

A

easily manipulated

non irritant

radiopaque

seals canal laterally and apically

impermeable to moisture

74
Q

GP is a trans isomer of what polymer

A

polyisoprene

75
Q

what are the two forms of GP and how are they formed

A

Alpha - naturally occurrent

beta - formed when alpha phase heated above 65 and cooled RAPIDLY - recrystallises as beta

76
Q

what phase of GP is used in dental GP

A

beta

77
Q

components of GP cones

A

20% GP
65% zinc oxide

radio pacifiers and plasticisers

78
Q

what is the function of a sealer - 3

A

lubricate during obturation

seal birds and irregularities in canal - lateral canals

seal space between dentinal wall and core

79
Q

ldeal properties of a sealer

A

easily mixed

no shrinkage on set

insoluble

radiopaque

80
Q

example of sealer used in endo

A

zinc oxide and eugenol

81
Q

disadvantage of ZOE sealers

A

unstable - lose volume with time - can impact apical seal

82
Q

what is MTA used for - mineral trioxide aggregate

A

pulp capping and root end filling

83
Q

disadvantage of MTA

A

tooth discolouration

long set time

BDS3 CDS (11 decks)

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