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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
advantage and disadvantage of custom post
unified post and core 2 visits required - impression and fit, risk of contamination
26
advantage of parallel sided post
avoids wedging
27
how to prevent rotation of post in absence of coronal dentine
anti rotation notch - small vertical groove in canal
28
taper of a core
6 degrees
29
why are posts not routinely used in molars
disadvantages outweigh advantages narrow roots - post prep may perforate core retention can be optioned from undercuts and bonding agents
30
if there is not coronal tissue on a molar, what canal would you insert a short post into
largest and straightest RC distal mandibular palatal maxillary
31
why is cuspal protection important - 3
prevents catastrophic fracture maintains coronal seal prevents microbial ingress
31
why is cuspal protection important - 3
prevents catastrophic fracture maintains coronal seal prevents microbial ingress
32
design objectives of root canal
continuously tapering funnel shape apical foramen in original position apical foramen as small as possible
33
instrument to detect canal orifice
DG16 endodontic explorer
34
where should GP be cut
orifice or just below orifice level
35
what material are k files made of
stainless steel flexible k files nickel titanium
36
motions you can use an endo file
filing reaming watch winding balanced force envelope of motion
37
which endo file technique can be described as back and forward oscillation of 30 and 60 degrees with light apical pressure
watch winding
38
which endo file technique can be described as 90 degree turn clockwise with apical pressure then 180 degree counter clockwise turn with continued pressure
balanced force technique
39
what is cyclic fatigue
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
cross section of reciprocal file
s shape
41
what angles of rotation does reciprocal use
150 CC then 30 CW
42
signs of RCT failure
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
indications for non surgical RC re treatment
intra radicular infection new complex restoration with a technically poor RCT loss of coronal seal
44
solvent that can be used to soften and help remove GP for re treatment
eucalyptus oil - more GP and sealer left behind if use solvent though
45
what would you write on a lab prescription for a post and core
please contract an post and core para post - colour core 6 degree taper and 2mm space in occlusion for crown
46
What factors would you consider when deciding on post options?
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
What factors do you consider important when deciding if a tooth is restorable?
remaining tooth structure - ferrule RCT status fractures bone levels
48
what is stress in DMS
deforming force measures across given area =F/A
49
what is strain
response of a material to stress
50
what is the elastic limit
a set valid representing the maximum strain that when applied to a file allows the file to return to original dimensions
51
what is elastic deformation
reversible deformation that does not exceed elastic limit
52
what is plastic deformation
permanent deformation occurring when elastic limit exceeded - the point that a plastic instrument will fracture
53
two ways Endodontics instrument can fail
cyclic fatigue torsional fatigue
54
what is torsional fatigue
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
how do you prevent endo instrument fracture
create a manual guide path - creates space for tip straight line access gentle pressure and constantly moving
56
what component of stainless steel prevents rusting
chromium - forms passivation layer of chromium oxide
57
what step in manufacture of endo files does work hardening occur
the twisting of the files
58
what is work hardening
strengthening of a material by plastic deformation dislocates crystalline lattice dislocations create resistance to further dislocations
59
how does NI-Ti not conform to typical properties of metals
displays super elasticity - application of stress does not result in usual proportional strain
60
what is the effect of temperature on NiTi crystal structure
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
what is the taper of an instrument
diameter change along working surface
62
taper of a K file
2%
63
function of flute on instruments
grooves to collect dentine and soft tissues
64
what is the helix angle
angle cutting axis forms with long axis of file
65
role of an irritant in Endodontics
removal of debris lubrication antimicrobial - kill bacteria and viruses
66
primary irritant for endo
NaOCL sodium hypochlorite 3%
67
what is responsible for antibacterial activity in sodium hypochlorite
HOCl hypochlorus acid
68
factors important for hypochlorite function
concentration volume contact mechanical agitation exchange
69
why is it important to remove the smear layer before obturation
prevents sealer penetration interferes with disinfection
70
what is the smear layer
organic pulp and inorganic dentine debris
71
what do we use to remove smear layer
17% EDTA
72
irritants can interact - give an example of a consequence of irritant interaction
interaction with NAOCl forms para chloroaniline cytotoxic and carcinogenic
73
ideal properties of an obturation material
easily manipulated non irritant radiopaque seals canal laterally and apically impermeable to moisture
74
GP is a trans isomer of what polymer
polyisoprene
75
what are the two forms of GP and how are they formed
Alpha - naturally occurrent beta - formed when alpha phase heated above 65 and cooled RAPIDLY - recrystallises as beta
76
what phase of GP is used in dental GP
beta
77
components of GP cones
20% GP 65% zinc oxide radio pacifiers and plasticisers
78
what is the function of a sealer - 3
lubricate during obturation seal birds and irregularities in canal - lateral canals seal space between dentinal wall and core
79
ldeal properties of a sealer
easily mixed no shrinkage on set insoluble radiopaque
80
example of sealer used in endo
zinc oxide and eugenol
81
disadvantage of ZOE sealers
unstable - lose volume with time - can impact apical seal
82
what is MTA used for - mineral trioxide aggregate
pulp capping and root end filling
83
disadvantage of MTA
tooth discolouration long set time

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