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Exam > Endodontics > Flashcards

Endodontics Flashcards

1
Q

dental pulp

A

low compliant CT lined by odontoblasts

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2
Q

causes of pulpal damage

A

caries
microleakage
trauma
traumatic occlusion
attrition, abrasion, erosion
ortho
radiotherapy
periodontal pathology

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3
Q

causes of pulpal damage in relation to cavity prep

A

heat generation
dehydration of dentine
cutting of odontoblast processes
direct injury to pulp
remaining dentine thickness

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4
Q

causes of pulpal damage in relation to restoration material

A

toxicity
pH of water
water absorption
heat of reaction
poor marginal adaptation
cementation
impression making
agents for treating dentine

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5
Q

dentine permeability

A

dentinal tubules increase in number & diameter as they get closer to the pulp
there are more tubules at the coronal aspect as opposed to roots which means deep occlusal cavities will have a lot of communication with the pulp

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6
Q

dental pain

A

in sub odontoblastic layer there is an extensive nerve plexus called rachow’s plexus - will transmit only pain from teeth
when there is inflammation these nerves will be stimulated & produce pain
nerves in this plexus inc
- a delta fibres (myelinated & stimulation causes sharp pain)
- c fibres (cause increased pulpal blood flow & pressure in pulp so dull aching pain)

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7
Q

EPT stimulates what fibres in pulp

A

a delta nerve fibres

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8
Q

healthy pulp

A

vital & free from inflammation
traumatic exposure treated within 30hrs will also be healthy

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9
Q

reversible pulpitis

A

a vital pulp that is inflamed
chance it can revert back to healthy pulp
diagnosed with pain to cold which lasts a short time, mediated by a delta fibres & no change in pulpal blood flow

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10
Q

irreversible pulpitis

A

pulp inflamed & vital but it cannot heal so only tx options are pulpectomy / RCT
diagnosed with spontaneous pain which is intermittent & may keep ptx awake at night, negative to cold but pain to hot with C fibre activation & there is increase in pulpal blood flow

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11
Q

necrotic pulp

A

pulp is non vital
RCT indicated
signs inc - discolouration, sinus present, gross caries, large restoration, radiographic evidence

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12
Q

infected pulp

A

radiographically diagnosed chronic radicular periodontitis
signs of inflammation will be absent due to lack of vitality
sometimes infection can be in only 1 root of multirooted tooth

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13
Q

when doing sensitivity tests

A

compare with adjacent & contralateral teeth

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14
Q

EPT (electric pulp test)

A

stimulates sensory nerves at pulp-dentine junction
a delta fibres tested
tooth should be dried, probe tip placed on incisal edge / cusp tip adjacent to pulp horn with conducting medium
circuit complete by holding handle
tingling or heat sensation should be felt
+ test = vital pulp tissue present but no indication of reversibility of inflammation
- test = reliable indicator for pulpectomy in 98% cases apart from immature pulps where it is unreliable

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15
Q

thermal tests

A

work by hydrodynamic forces where fluid movement in dentinal tubules will activate sensory nerve receptor units in pulp - either by hot or cold tests
cold = spraying ethyl chloride onto cotton pellet & placing on tooth; - response indicative of pulp necrosis
hot = vaseline on tooth then hot GP; - response indicates pulp necrosis but if too hot this can cause irreversible pulpitis

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16
Q

removal of necrotic pulp

A

only in incomplete root development should necrotic pulp be removed to a non-inflamed level

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17
Q

impact of age on dentine & pulp

A

dentine encroaches on pulp throughout life thus reducing size & volume of pulp
number of cellular components, blood vessels and nerves will also be decreased
increased calcification & fibrous components
all of this leads to pulp that is less likely to reverse in inflammatory response

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18
Q

cavity sealers

A

e.g. varnish, liner, base material
can protect cut dentine & underlying pulp from bacteria
may also protect from toxic effects of restorative material in setting phase of reaction
whole exposed pulpal dentine must be covered & it should adhere to dentine rather than restorative material but not reduce strength of restorative material or dissolve in biological liquids

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19
Q

varnish

A

material dissolved in organic solvent which will evaporate on application to dentine
must be applied twice
leaves a layer of synthetic resins that reduce permeability of dentine by 69% but is now rarely used

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20
Q

liners

A

varnish that contains fillers & additives & will be applied as thin layer
intended to have beneficial effect on pulp so will contain additives i.e. CaOH

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21
Q

cavity base

A

thicker sealer that will protect pulp from thermal effects from restorative material
usually CaOH or RMGI

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22
Q

CaOH

A

bacteriocidal & bacteriostatic
produces high pH that stimulates fibroblasts & reparative dentine formation; will also stimulate recalcification of any demineralised dentine & neutralises low pH from acidic restorative materials
*** weak cement & very soluble if not protected so if used close to pulp then it should be covered with RMGI then restorative material of choice

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23
Q

DBA

A

both dentine primers with or without adhesives are tolerated by pulp & there will be marked reduction in microleakage when DBA used; very technique sensitive though

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24
Q

periradicular disease

A

disease around root of tooth, not in the root
aetiology = gross caries // severe perio disease // trauma // cracks or fractures
this can cause:
- bacterial infiltration of root canal
- leading to pulpal necrosis

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25
Q

bacteria involved in periradicular disease

A
  1. necrotic untreated cases - gram neg anaerobic
  2. failing RCT & persistent infection - gram pos anaerobic
  3. non healing cases - enterococcus faecalis
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26
Q

3 processes to successful endo tx

A
  1. shaping
  2. irrigation
  3. 3D obturation
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27
Q

what information will a PA give

A
  • extent of caries
  • periapical pathology
  • periodontal pathology
  • no, morphology, length of roots & canals
  • calcification of pulp chamber & root canals
  • proximity of anatomical structures
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28
Q

common variations of root canal

A

upper molars - 90% have 4 canals
lower incisors - 40% have 2 canals
lower canines - 14% have 2, sometimes 3 canals
premolars - canal will frequently divide
radiographic clues - if canal very noticeable but suddenly disappears then it probably divides into 2 or 3

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29
Q

after producing access cavity (of straight line access)

A

EDTA is used to remove inorganic debris and to lubricate canals in preparation for obturation

30
Q

why shape canals

A
  • allows access of irrigants
  • allows sufficient obturation materials to fit into canal effectively
  • allows for significant pressure to allow sealer into accessory canals
    if inadequate shaping there will be inadequate obturation
31
Q

how to shape canals

A

shaping should produce early flaring at coronal part of root canal; this is to avoid a high hydrostatic pressure in canal
coronal 1/3 will be heavily contaminated so it will remove contents first to stop further contamination of canal system
this should also improve straight line access of apical 1/3
this shape to coronal part of RC is produced using step down technique
apical shape should be more of a tapering funnel to allow for obturation in 3 dimensions; however apical stop should form at natural apical constriction

32
Q

irrigants & lubricants

A

must be used during cleaning & shaping process, main ones used:
1. NaOCl 1-5%; gross debridement, elimination of microbes & dissolution of pulpal remnants
2. CHX 0.2-2%; elimination of microbes
3. EDTA 17%; removal of smear layer so tubules in dentine left open for entry of irrigants
4. lubrication gel
must be prepared to size 30 file to allow for 30 gauge needle

33
Q

length determination of root canal

A

measurement must be take from reference point which must not change
optimal length is around 1mm from radiographic apex as this is the apical constriction
electronic / radiographic methods can be used to determine this

34
Q

modified double flare technique

A

used to shape canals & uses stepback
apical 1/3 instrumented then canal is instrumented further ack
canal orifice is first shaped using gates-glidden bur then K files are used to instrument to working length until fitting snugly; this is the master file
use K file 1 size larger 1mm back, recapitulate using master file then use K file 1 size larger 1mm back again
continue this until near coronal 1/3
to cut dentine using K file the balanced force technique is used; the file inserted by rotating 60o clockwise, cut by rotating 120o anticlockwise then loaded with clockwise rotation

35
Q

problems with modified double flare technique

A
  • majority of bacteria in coronal 1/3 which can become inoculated towards apex & there is often poor penetration of irrigant to the apex
  • if ss files are used it can straighten canals & possibly block them all at apex
  • can cause some debris to be extruded through the apex
  • straightened canals can cause loss of working length too
  • must not excessively flare coronal 1/3
  • as apex is shaped first, ape will cause resistance to shaping causing non straight line axis
36
Q

advantages of crown down technique using NiTi shaping

A
  1. better shaped canal
  2. less extrusion of debris
  3. more predictable results
37
Q

types of NiTi rotary instruments

A
  1. constant taper - can have tendency of screwing in past apex
  2. variable taper - do not have this tendency, allow for increased apical taper & uses less files
    must be done at set torque & ratio so they cannot be used in normal handpiece
38
Q

errors in canal prep

A

main cause of error may be loss of working length caused by dentine or other debris being packed apically, ledge formation, broken instruments in canal or perforation
as canal is instrumented it is bound to become a bit straighter at least causing a loss in WL

39
Q

inter appointment intracanal medicament

A

2 options =
1. non setting calcium hydroxide -> open apex immature tooth, transverse root #, apical resorption, internal resorption, apical inflammatory resorption, large periapical lesions, control of apical exudate
2. antibiotic / steroid paste -> only used if pulp vital or else should never be used

40
Q

what is obturation and why do we do it

A

process of obturation is to fill root canal with material i.e. GP
even though most important part of RCT is a good coronal seal, if canal is well obturated the ingress of bacteria will be prevented or slowed despite a poor seal
2 types used in GDHS:
1. carrier based thermal obturation
2. cold lateral compaction

41
Q

pros of CBTO

A
  • carrier placed into heated machine then added to canal to working length
  • GP will flow into accessory canals dentinal tubules & other areas cold GP would not reach
  • excellent apical & lateral canal sealing
  • easy to obturate long curved & narrow canals
  • easy to use
42
Q

cons of CBTO

A
  • difficult to get adequate apical control & keep GP confined to canal
  • difficult to produce space for post with thermafil & it must be drilled so CLC may be easier
  • more difficult to retreat these teeth and in tooth with apical resorption the GP is likely to leak
43
Q

technique of CBTO

A

verify WL
sterile paper point used to dry canal
sealer coated thinly on canal wall
AH+ used
will fill voids present
thermafil carrier put to CWL & heated & placed in canal to WL, packed in with plugger & carrier device is removed

44
Q

why use AH+ (4)

A
  1. excellent dimensional stability
  2. low toxicity
  3. self adhesive nature
  4. very high radiopacity
45
Q

when not to use AH+

A

if ptx is hypersensitive to amines or epoxy resins

46
Q

cold lateral compaction

A
  • master point used (corresponding to k file or protaper file) at WL & inserted into canal
  • plenty of sealer should be used
  • check master cone for tug back
  • radiograph taken to ensure correct size
  • accessory points added using finger spreaders
  • should be inserted to 2mm from apical stop & master point forced to side of canal
  • first size A then B etc
  • care must be taken not to use excessive pressure with finger spreaders
  • GP excess should be removed using heated instrument (super endo alpha) then plugged with plugger
  • thin layer of GI then added over pulp chamber to seal canals & for retention of final restoration
47
Q

success rates of endo tx

A

if no PA lesion there is 96% chance of success
in teeth with PA lesions there is 86% chance of success
and just 62% with re treatment
however RCT more successful than implants & should be 1st choice

48
Q

reasons for RCT failure

A
  1. pre tx = tooth not restorable & should be XLA, wrong root filled
  2. during tx = missed canals, ineffective cleaning/shaping/filling, iatrogenic damage
  3. post tx = recurrent caries, damage when producing post hole, coronal leakage
    main problem is poor coronal seal
49
Q

options following failure of RCT (4)

A
  1. monitor if non symptomatic & ptx is happy
  2. attempt retreatment
  3. periradicular surgery
  4. XLA
50
Q

orthograde retreatment

A

GDHS uses protaper instruments (D1, D2, D3)
depends on type of filling material; if insoluble resins used, ultrasonic devices should be used or if GP used protaper D without solvents (use eucalyptus oil) or if soluble pastes used then solvent with protaper D
protaper D should be sued at 350/400rpm very gently
- D1 & clean flutes frequently
- continue until all obturation material removed from coronal 1/3
- D2 used for middle & D3 for apex
- stop 2-3mm from apex to remove risk of pushing GP out
- final 2-3mm should be cleaned using hand instrumentation with C+ hand files of 08/10/15 to avoid extrusion of debris

51
Q

periradicular surgery

A

part of root most infected i.e. apical 3mm removed
used a lot in retreatment

52
Q

indications for periradicular surgery

A

if orthograde retx has failed and/or is inappropriate

53
Q

root end fillers in periradicular surgery

A

MTA (mineral trioxide aggregate)
sealing ability is good & is biocompatible, has a high pH with a 5min working time, radiopacity is greater than that of IRM & super EBA

54
Q

when should definitive restoration be placed

A

if root filled tooth has not had definitive restoration placed coronally in 3mths generally it should be re treated due to no proper coronal seal

55
Q

requirements for post & core in root treated teeth

A

must be adequate shape, length, diameter, health of periradicular & periodontal tissues, quality RC obturation and suitable ferrule for post crown
(core provides retention for crown)

56
Q

direct v indirect posts

A

direct = bonded fibre posts which are prefabricated & can be placed in certain canals only
indirect = cast metal
posts can be threaded, serrated, smooth (each lowering in their retention) and can be parallel / tapered

57
Q

how to decide what post to use

A
  • size of RC; if increased diameter it does not significantly improve retention so often prep for smaller post is better than larger one
  • retention increases with post length & this must be as long as the crown if not longer
  • should be between 1/2-3/4 of the root with at least 3-5mm obturation material remaining
  • curvature must be considered when placing posts
58
Q

ferrule

A

this is the encirclement of 1-2mm around the vertical axial tooth structure within the walls of the crown (circular band of tooth structure left after crown prep to support & stabilise overlying crown)
this dictates what post is used as if there is not an adequate ferrule then fibre post MUST NOT BE USED - crown margin will not be placed on solid tooth & chance of root # significantly increased

59
Q

post space prep

A

after post chosen, must prep
unsupported tooth structure must be removed
coronal GP should be removed immediately after obturation using chemical softening agent e.g. chloroform, eucalyptus oil, xylene or turpenine & mechanical removal such as gates glidden
post space then prepared following long axis of tooth & by adding anti-rotation groove for indirect posts

60
Q

fibre v cast posts

A

fibre
- high bond strength allows it to absorb & dissipate stress
- more biocompatible
- low modulus of elasticity which is similar to dentine & will help resist root #
- chemically compatible with adhesives & composites
- 2 separate tapers to adapt root canal well
- can be removed & replaced in minutes making it much more hassle free than metal posts
- just 3 sizes required which lowers cost on inventory
- aesthetic & can transmit light to cure primer & cement through post

61
Q

cautions with post crown on root treated tooth

A

technique sensitive
rubber dam must be used for moisture sensitivity
must be adequate ferrule i.e. 1.5mm remaining dentine on more than 75% of tooth surface

62
Q

process of placing fibre post

A
  • prepare canal
  • space irrigated with 0.2% CHX
  • etched
  • both post & canal are primed then light cured
  • cement then added to canal & post inserted then light cured for 60s
63
Q

cast core & post

A

useful in flared roots
custom made posts which follow shape of root canal
however may be less retentive that parallel sided posts & may cause wedging
for round canals, anti-rotational notch should be placed coronally

64
Q

placing cast posts

A

must be an escape vent to allow excess cement up canal
post then has trial insertion & if tight fit then shiny spots should be removed
cement made up of RMGI & applied to both post & wall of canal with endodontic file
if cement is just applied to post there is significant reduction of bond strength

65
Q

failures of posts

A
  • tapered metal posts most likely to fail as they can act as wedges being pushed further into canal & causing #
  • if post too threaded the screwing into dentine may create more pressure on dentine
  • diameter of post has no effect on retention so smallest post within reason should be used
  • if post parallel & retained only by cement then it will distribute masticatory forces more evenly throughout as cement acts as buffer between post & tooth
  • ss posts less likely to fail than titanium posts are their modulus of elasticity is most like that of dentine
  • most common failure if due to crown # and least common due to RCT failure so post itself causes good seal
66
Q

other causes of failure

A

instrument failure
vertical root #
resorption
crown factors i.e. untreatable caries
root # at post level not due to trauma
traumatic # & furcation perforation

67
Q

adv of overdenture on RR/reduced crown

A
  • retention of supporting alveolar bone
  • continued periodontal proprioception
  • improved support
  • retention of dentures
  • denture better able to resist occlusal forces than tissue borne
  • psychological advantages
68
Q

restoration of anterior endodontically treated tooth

A

intact marginal ridge = RMGI liner & CR
discoloured teeth with intact marginal ridge = RMGI liner essential & bleaching or else veneer/crown
marginal ridge destroyed = post & core

69
Q

restoration of posterior endodontically restored tooth

A

post disadv will outweight adv as narrow endodontic canals mean a strip / lateral perforation more likely
core can often be produced in molar teeth via undercuts, dentine pins or bonding agents so post not usually needed
if no coronal tissue a short post into the largest straightest canal is indicated
1mm ferrule should be used for definitive restoration unless all porcelain restoration is used

70
Q

if post indicated for posterior tooth

A

should be placed in distal roots of mandibular molars or palatal roots of maxillary molars as they are usually the largest with the straightest canals for easier post insertion

71
Q

options for restoration of posterior root filled tooth

A

amalgam
CR/GIC/RMGI
gold inlay
ceramic inlay
cusp covered indirect restoration
full veneer crown
post core crown

72
Q

to increase retention of crown

A

use of dentine pins & cuspal overage increases retention

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