ELECTRONIC APEX LOCATORS Flashcards
anatomical apex
- end of the root as determined from a macro perspective
radiographic apex
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
major apical contstruciton
- widest point of the foramen where is exists in the root
minro apical foramen
- narrowest point of the foramen, known as apical constriction
- usually 0.5-1mm short of the radiographic apex
CDJ
- 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!!!
methods to dertermine working lenght
- tactile feedback from instruments
- paper point technique
- radiographic determination of WL
- electronic apex locators
tactile feedback
- made complicated by sclerosis, resorption and anatomical differences
- not recommended for determining WL
paper point technique
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
radiohgraphic determination of WL
paralleling technique-
flawed as the apical constriction can be sig further away resulting in over instrumentation of the apex
electronic apex locators
modern reliable
can be used in conjunction
uses resistnace of root canal and PDL
how do electronic apex locators work
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
problems with apex locators
metaliic restorations will short cicuit locator
perforations will trigger responce
large canals can cause a misreading
endo aim
to eliminate bacteria from the tooth
steps to successful endo
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
interim restoration
- 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
temp restoration
placed in endo access cavity
likely to be cut through an interim restoration
common bacteirtal entry pathways
- caries
- cracks
- exposed dentine
- broken down restoration margins
advantages of a well restored tooth with an interim restoration
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
appropriate materaisl for interim restorations
composite
RMGIC
amalgam
not GIC or IRM
how can teeth with cracks be supported
ortho band
copper ring
ad of metal bands
1) support of weakened tooth structure esp cusp
2) prevention of progression of cracks
advantages of removing full crown prior to endo
- through assessment of underlying tooth structure
- identification of hidden pathology
- better orientation when undertaken endo treatment
- better coronal seal
temp restorations and desirable properties
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
potential temp restoration materials
- 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
requirements of temp restroation
- 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
why should you protect posteiror teeth undergoing endo therapy
- reduced tooth structure
- access cavity
- loss of marginal ridges
- axial forces can flex cusps
- non axial forces are even more damaging (excursive forces
why is canine guidance ideal
- 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
interum measures to protect posterior teeth
occlisal adjustment to reduce loading
cusp reduciton and overlay restoration
cemented ortho band
interrum crown
definitive measures to protect posterior teeth
cusp redcution
onlay
full crown
occlusal adjustment
to reduce occlusal loading
- to reduce the lateral excursive forces (which are damaging)
- reduces the risk of fracture during and after treatment
