2 - Accessing the Root Canal System: Incisors, Canines, Premolars Flashcards
a correctly sized and sited access cavity is one of the most important factors in allowing what?
- enabling efficient and effective root canal preparation and obturation
good access cavity design: what does it allow? what does it help avoid? what does it provide? why should we conserve as much tooth structure as possible?
- allows
1. removal of roof of pulp chamber and pulp horns
2. direct vision of pulpal floor and canal orifices
3. straight line access into canals - helps avoid damage to pulpal floor or perforation
- provides retention for placement of a temporary restoration between visits
- overzealous access cavities-> may render tooth unrestorable
use of rubber dam to cut access cavity while inexperienced: why is it better to cut without?
- cutting with rubber dam may risk losing orientation and perforating the tooth - especially if tooth is crowned, tilted, rotated or if pulp chamber calcified
with incisors - where is the most common perforation?
towards the labial surface
access cavity preparation - friction grip burs:
what is used to cut initial preparation?
what is used to cut through metal?
- round or fissure diamond burs
- tungsten carbide
access cavity preparation - latch grip round burs:
normal and long shanked burs are used for?
used to lift the roof of the pulp chamber and remove overhanging dentine
access cavity preparation - safe ended burs: what is good about it?
non-cutting tip - avoids damaging the floor of the pulp chamber
5 general requirements for successful endodontics?
- diagnosis and tx planning
- knowledge of tooth anatomy and canal morphology
- effective cleaning and shaping to the correct length
- obturation
- coronal seal
cleaning and shaping the root canal system:
what does cleaning hope to achieve?
- removal of organic pulp debris, microorganisms and toxins
cleaning and shaping the root canal system:
what does shaping hope to achieve?
controlled removal of dentine to produce a tapering shape that can be disinfected and sealed throughout its length with a root canal filling
biological objectives of root canal treatment?
- confine instrumentation to the root canal
- prevent extrusion of necrotic debris
- remove all tissue debris and substrate for bacterial regrowth
- create sufficient space for irrigation and intra-canal medication
- complete cleaning and shaping in one visit if possible
design objectives of root canal treatment?
- to create a continuously tapering funnel shape
- maintain apical foramen in original position
- keep apical opening as small as possible
what is the use of a “front-surface” mirror?
it is an endodontic mirror that will not give a double image and it is used for all endodontic procedures
what is the aseptic technique? what is it used for?
- aseptic technique: do not use instruments from RCT kit until tooth has been isolated by rubber dam
- it helps to exclude contamination with organisms that have greater resistance to treatment than members of the root canal’s microbia e.g. facultative anaerobes & yeasts
instrumentation:
what does it NOT do?
instrumentation DOES NOT:
- eradicate endodontic infection
- lead to healing of lesion
instrumentation:
what are the aims of it?
- mechanically removes pulp tissue, microorganisms and infected dentine
- creates space for effective irrigation and disinfection
- creates space for placement of a root canal filling
instrument fracture: what may it affect?
what might happen if you try to remove excess tissue in order to retrieve the instrument?
- it may impede disinfection of the root beyond the instrument
- may cause reduced root strength or root perforation
factors contributing to root fracture?
- operator: lack of proficiency
- instrumentation technique
- instrument design
- use of torque controlled motors
- instrument size and radius of curvature
- surface condition
- rotation rate
flexural stress (fatigue): how does it form and propagate?
- microcracks form on surface of the metal
- these cracks propagate with loading, until instrument fails
torsional stress:
- also known as?
- how does it occur?
- when does the instrument fail?
- shear failure
- occurs when the tip or other part of the instrument binds to the canal wall, whereas the handpiece keeps rotating the instrument
- file fails when the shear strength is exceeded
rotary NiTi files:
- most use speeds of?
- each file requires?
- how are they different from hand ss files?
- used with what sort of motions?
- 250-300rpm
- a specific torque setting
- files have a higher taper then hand ss files
- pecking motion, brushing motion or painting motion
what does torque refer to?
it describes the forces that act in a rotational manner
low torque control motors:
- torque values are set at which level?
- why do motors have precise values?
- values are low or high for which type of instruments?
- torque value is set at less than the value of torque at deformation, and at separation of the rotary instruments
- so that the limit of elasticity is not exceeded
- low for smaller, less tapered instruments. high for larger, more tapered instruments
ProTaper Next:
design features?
what effect does its movement have?
- bilateral symmetrical rectangular cross section with an offset from the central axis of rotation
- asymmetrical rotary motion that travels along the file
- swaggering effect
ProTaper Next:
file contacts canal wall at how many points in any given cross section?
how is this useful? what is it good for?
- file contacts canal wall at 2 points in any cross section
- minimizes engagement between file and dentine
- improved safety and cutting efficiency, less stress on the file and more efficient debris removal
ProTaper Next:
reduced engagement between instrument and dentine contributes to?
- a reduction in taper lock, screw in effect, and less stress on the file
ProTaper Next:
removes debris in what direction?
this allows for? which leads to?
- removes debris in coronal direction
- this allows for more space around the flutes, meaning that cutting efficiency is increased, as the blades stay in contact with the surrounding dentine walls
endodontic microbes:
different species dominate at different stages: this depends on?
- availability of nutrition
- oxygen level
- local pH
endodontic microbes in primary cases?
- nutrients: proteins and glycoproteins
degradation of pulpal tissue and exudate - black pigmented bacteria (prevotella, porphyromonas)
- fusobacterium nucleatum
- veillonella parvula
- eubacterium
- enterococci 5%
endodontic microbes in root filled teeth?
- enterococci 29-77%
- streptococci
- lactobacilli
- actinomyces
- candida
- eubacterium alactolyticus
- propionibacterium propionicum
- dialister pneumosintes
limitations of instrumentation:
in oval shaped canals, only how much of the walls can be contacted by instruments?
40%
root canal irrigants - ideal requirements?
- eliminate or minimise microorganisms
- inactivate endotoxin
- dissolve necrotic pulp tissue remnants
- lubricate the root canal instruments
- remove the smear layer and biofilm
- be systemically non-toxic
- be non-caustic to periodontal tissues
irrigants: examples?
- sodium hypochloride
- citric acid
- ethyldiaminetetraacetic acid EDTA
- 2% chlorhexidine
sodium hypochloride:
- what kind of antimicrobial effect? what can it eliminate? antimicrobial properties rely on?
- capable of dissolving ___?
- how much concentration?
- broad spectrum antimicrobial effect
- bacteria, fungi, spores, viruses
- rely on free chlorine
- can dissolve necrotic tissues
- 1 to 5.25%
sodium hypochloride:
how much concentration should be used?
at what volume?
for how long?
- not more than 1% wt/vol
- 20mls per canal
- rotary preparation techniques are quick however sufficient time should still be allocated to irrigation
sodium hypochloride disadvantages?
- unpleasant taste
- high toxicity
- inability to remove smear layer when used alone
complications during irrigation? how to avoid?
- damage to clothing: use plastic bibs and ensure needle correctly attached to syringe
- damage to eye: always wear safety glasses, eye should be washed with large amount of tap water/saline and patient referred to opthalmologist
injection of sodium hypochloride beyond apex: happens when?
- wide apical foramina
- apical constriction destroyed during root canal prep or by inflammatory resorption
- extreme pressure during irrigation
- binding of irrigation needle tip
symptoms of injecting NaOCl beyond apex?
- extreme pain, burning sensation
- haematoma and ecchymosis
- swelling
- profuse haemorrhage from the root canal
- 2nd infection and tissue necrosis
- parasthesia
treatment of injecting NaOCl beyond apex - should focus on?
- minimising swelling
- controlling pain
- preventing secondary infection
- reviewing the patient until symptoms resolved
treatment of injecting NaOCl beyond apex - examples of methods?
- analgesics
- external compression with cold packs, replaced with warm compresses for a few days
- antibiotics may be needed to prevent secondary infection
- refer to OS if pt requires surgical intervention
smear layer: how is it produced? contains what? what does it do? what can it prevent?
- cleaning and shaping the root canal can produce a layer that covers the instrumented walls
- inorganic and organic substances e.g. microorganisms, necrotic materials
- protects microbes in the dentinal tubules from the effects of disinfectants
- prevents complete adaptation of obturation materials to the root canal surfaces
chelating agents: 17% ethylenediaminetetraacetic acid EDTA: smear layer particles are soluble in?
they react with what in dentine to form what?
works with what to dissolve organic components?
- soluble in acids
- EDTA reacts with calcium (inorganic) ions in dentine, forms soluble calcium chelates
- works with sodium hypochloride, which dissolves the organic components
organic acids - 10% citric acid
works with?
can leave behind what?
how does it compare to EDTA?
- works with NaOCl
- precipitation crystals
- not as effective
