ELECTRONIC APEX LOCATORS

Question 1

anatomical apex

Answer 1

• end of the root as determined from a macro perspective

Question 2

radiographic apex

Answer 2

determined by radiographu

• inaccurate, as foramen is often associated to one side of the radiographic apex
• cementum at the apex can cause discrepancies
• pathology, such as external resorption can changed the position foramen
• estimate

Question 3

major apical contstruciton

Answer 3

• widest point of the foramen where is exists in the root

Question 4

minro apical foramen

Answer 4

• narrowest point of the foramen, known as apical constriction
• usually 0.5-1mm short of the radiographic apex

Question 5

CDJ

Answer 5

• point where the cementum fuses with the radicular dentine
• considerate to be the point where the RC system finishes and periodontium begins
• considered to be the ideal limit of a root canal treatment

only histologicallly deteced!!!

Question 6

methods to dertermine working lenght

Answer 6

• tactile feedback from instruments
• paper point technique
• radiographic determination of WL
• electronic apex locators

Question 7

tactile feedback

Answer 7

• made complicated by sclerosis, resorption and anatomical differences
• not recommended for determining WL

Question 8

paper point technique

Answer 8

Based on the premise that the root canal system of an uninfected tooth is dry whilst the periodontium is wet (hydrated tissue)
- the wet/dry interface is therefore used as a reference point

complicated withapical exudate in infected cases

Question 9

radiohgraphic determination of WL

Answer 9

paralleling technique-

flawed as the apical constriction can be sig further away resulting in over instrumentation of the apex

Question 10

electronic apex locators

Answer 10

modern reliable
can be used in conjunction
uses resistnace of root canal and PDL

Question 11

how do electronic apex locators work

Answer 11

Electrical circuit formed
- stating at AL, running through clip on the file, through root canal, through apical constriction , out PDL and through the mucosa and to the clip on pts lip back to AL

Question 12

problems with apex locators

Answer 12

metaliic restorations will short cicuit locator
perforations will trigger responce
large canals can cause a misreading

Question 13

endo aim

Answer 13

to eliminate bacteria from the tooth

Question 14

steps to successful endo

Answer 14

diagnose and remove cause
aspetic technique
mechanically instrument RC to enlarge them
irrigate canals with one or more antibacterial sol
medicate canals with AB agent
temp restore the tooth to avoid bacterial ingress
fill RC system
restore tooth to normal funciton

Question 15

interim restoration

Answer 15

• restoration that has been placed in a tooth after the previous restoration, caries cracks tc have been removed before the commencement of endodontic treatment
• can end up being a core if indirect restoration being placed

Question 16

temp restoration

Answer 16

placed in endo access cavity

likely to be cut through an interim restoration

Question 17

common bacteirtal entry pathways

Answer 17

• caries
• cracks
• exposed dentine
• broken down restoration margins

Question 18

advantages of a well restored tooth with an interim restoration

Answer 18

structural integrity to tooth
support weakened cusps
coronal seal
rubber dam easier
ideal access cavity can be cut
no risk of leakage
temp restoration will be retained better
more conformable and functional to pt

Question 19

appropriate materaisl for interim restorations

Answer 19

composite
RMGIC
amalgam
not GIC or IRM

Question 20

how can teeth with cracks be supported

Answer 20

ortho band

copper ring

Question 21

ad of metal bands

Answer 21

1) support of weakened tooth structure esp cusp

2) prevention of progression of cracks

Question 22

advantages of removing full crown prior to endo

Answer 22

• through assessment of underlying tooth structure
• identification of hidden pathology
• better orientation when undertaken endo treatment
• better coronal seal

Question 23

temp restorations and desirable properties

Answer 23

Occupy the access cavity between appointments
Main requirement
- to provide effective and durable coronal seal
Other desirable properties include:
- ease of removal at the next appointment
- obvious difference between tooth tissue or interim restoration to allow removal without risk of removing more tooth tissue
- inexpensive

Question 24

potential temp restoration materials

Answer 24

• zinc oxide based reinforced intermediate restorative materials eg IRM (but IRM does not bond to tooth structure|)
• GIC
• RM GIC
• reinforced GID eg ketac fil, ketac silver
• composite

Question 25

requirements of temp restroation

Answer 25

• temp material must be min 3mm in depth to provide adequate seal
• cotton wool should not be used underneath the temp material as it wicks saliva and bacteria through restoration
• sponge pellets don’t do this and are compressed under temp restoration – easier removal
• Cavit/coltisol provides good double seal but more difficult to remove

Question 26

why should you protect posteiror teeth undergoing endo therapy

Answer 26

• reduced tooth structure
• access cavity
• loss of marginal ridges
• axial forces can flex cusps
• non axial forces are even more damaging (excursive forces

Question 27

why is canine guidance ideal

Answer 27

• protects posterior teeth
• group function is damaging to posterior teeth esp if they have been root treated
• pre molars are at most risk as more commonly involed in group function compared to molars
• often weakened due to comparatively more tooth tissue loss
• Other forces such as non working side interferences are also extremely damaging for toot treated teeth

Question 28

interum measures to protect posterior teeth

Answer 28

occlisal adjustment to reduce loading
cusp reduciton and overlay restoration
cemented ortho band
interrum crown

Question 29

definitive measures to protect posterior teeth

Answer 29

cusp redcution
onlay
full crown

Question 30

occlusal adjustment

Answer 30

to reduce occlusal loading

• to reduce the lateral excursive forces (which are damaging)
• reduces the risk of fracture during and after treatment