Endodontics

Question 1

dental pulp

Answer 1

low compliant CT lined by odontoblasts

Question 2

causes of pulpal damage

Answer 2

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

Question 3

causes of pulpal damage in relation to cavity prep

Answer 3

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

Question 4

causes of pulpal damage in relation to restoration material

Answer 4

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

Question 5

dentine permeability

Answer 5

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

Question 6

dental pain

Answer 6

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)

Question 7

EPT stimulates what fibres in pulp

Answer 7

a delta nerve fibres

Question 8

healthy pulp

Answer 8

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

Question 9

reversible pulpitis

Answer 9

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

Question 10

irreversible pulpitis

Answer 10

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

Question 11

necrotic pulp

Answer 11

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

Question 12

infected pulp

Answer 12

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

Question 13

when doing sensitivity tests

Answer 13

compare with adjacent & contralateral teeth

Question 14

EPT (electric pulp test)

Answer 14

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

Question 15

thermal tests

Answer 15

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

Question 16

removal of necrotic pulp

Answer 16

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

Question 17

impact of age on dentine & pulp

Answer 17

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

Question 18

cavity sealers

Answer 18

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

Question 19

varnish

Answer 19

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

Question 20

liners

Answer 20

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

Question 21

cavity base

Answer 21

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

Question 22

CaOH

Answer 22

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

Question 23

DBA

Answer 23

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

Question 24

periradicular disease

Answer 24

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

Question 25

bacteria involved in periradicular disease

Answer 25

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

Question 26

3 processes to successful endo tx

Answer 26

1. shaping 2. irrigation 3. 3D obturation

Question 27

what information will a PA give

Answer 27

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

Question 28

common variations of root canal

Answer 28

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

Question 29

after producing access cavity (of straight line access)

Answer 29

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

Question 30

why shape canals

Answer 30

- 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

Question 31

how to shape canals

Answer 31

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

Question 32

irrigants & lubricants

Answer 32

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

Question 33

length determination of root canal

Answer 33

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

Question 34

modified double flare technique

Answer 34

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

Question 35

problems with modified double flare technique

Answer 35

- 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

Question 36

advantages of crown down technique using NiTi shaping

Answer 36

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

Question 37

types of NiTi rotary instruments

Answer 37

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

Question 38

errors in canal prep

Answer 38

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

Question 39

inter appointment intracanal medicament

Answer 39

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

Question 40

what is obturation and why do we do it

Answer 40

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

Question 41

pros of CBTO

Answer 41

- 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

Question 42

cons of CBTO

Answer 42

- 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

Question 43

technique of CBTO

Answer 43

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

Question 44

why use AH+ (4)

Answer 44

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

Question 45

when not to use AH+

Answer 45

if ptx is hypersensitive to amines or epoxy resins

Question 46

cold lateral compaction

Answer 46

- 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

Question 47

success rates of endo tx

Answer 47

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

Question 48

reasons for RCT failure

Answer 48

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

Question 49

options following failure of RCT (4)

Answer 49

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

Question 50

orthograde retreatment

Answer 50

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

Question 51

periradicular surgery

Answer 51

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

Question 52

indications for periradicular surgery

Answer 52

if orthograde retx has failed and/or is inappropriate

Question 53

root end fillers in periradicular surgery

Answer 53

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

Question 54

when should definitive restoration be placed

Answer 54

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

Question 55

requirements for post & core in root treated teeth

Answer 55

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)

Question 56

direct v indirect posts

Answer 56

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

Question 57

how to decide what post to use

Answer 57

- 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

Question 58

ferrule

Answer 58

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

Question 59

post space prep

Answer 59

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

Question 60

fibre v cast posts

Answer 60

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

Question 61

cautions with post crown on root treated tooth

Answer 61

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

Question 62

process of placing fibre post

Answer 62

- 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

Question 63

cast core & post

Answer 63

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

Question 64

placing cast posts

Answer 64

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

Question 65

failures of posts

Answer 65

- 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

Question 66

other causes of failure

Answer 66

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

Question 67

adv of overdenture on RR/reduced crown

Answer 67

- 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

Question 68

restoration of anterior endodontically treated tooth

Answer 68

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

Question 69

restoration of posterior endodontically restored tooth

Answer 69

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

Question 70

if post indicated for posterior tooth

Answer 70

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

Question 71

options for restoration of posterior root filled tooth

Answer 71

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

Question 72

to increase retention of crown

Answer 72

use of dentine pins & cuspal overage increases retention