Hand filing, working length, and apex locators Flashcards
6 steps of endodontic infection (etiology)
BACTERIA
- pulpal injury
- irreversible inflammation
- ischemia
- infarction
- necrosis
- periradicular extension of disease
primary etiology of endo disease and who determined it? what year?
BACTERIA
1965 by Kakehashi
two major types of infections in endodontic lesions?
- Intraradicular infection
2. Extraradicular infections
Intraradicular infection
contained within the root canal system
Extraradicular infections
typically forms in response to an intrara-dicular infection lie apical abscess in response to necrosing pulp
can be independent of intra-radicular infection and thus may persist when host defense is unable to clear infection (chronic periapical inflammation)
what is considered to be the number one failure of a root canal procedure?
coronal leakage
what causes coronal leakage?
- delay in restoration after RTC
- temporary coronal filling compromised
- fracture to canal system exposed prior to final restoration
- final restoration lacks ideal marginal integrity or deteriorates
- recurrent caries present at restoration margins
predictability of successful endodontics is compromised of what three factors?
- knowledge
- skill
- desire
primary objectives of cleaning and shaping (4)
- remove infected soft and hard tissue
- give disinfecting irrigants access to the apical canal space
- create space for the delivery of medicament’s and subsequent obturation
- retain the integrity of radicular structures
in ideal shaping you develop?
develop a CONTINUOUSLY SHAPED CONICAL FORM from apical to coronal with apical preparation AS SMALL AS PRACTICAL and in its ORIGINAL SPATIAL POSITION
- removal of a uniform layer of dentin in all dimensions and all regions of the canal is desirable
shaping facilitates?
CLEANING
minimal apical size in shaping? what does this allow for?
30/0.06
or maybe 5 and 0.04
*exchanging of irrigants is enabled when open it up
shaping criteria and requirements?
when can you be considered done shaping?
- enlargement
- taper (0.06 taper for warm vertical compaction)
shaping can be considered complete when a non-standardized medium or fine-medium gutta-percha cone can be fitted to the working length
Schilder’s 5 BIOLOGICAL objectives
- confine instrumentation to the root canal
- beware of forcing necrotic material beyond the foramen
- remove all tissue debris from the root canal system
- complete cleaning and shaping of canals in one visit
- create sufficient space during canal enlargement for intra-canal medication and for potential exudates reception
Schilder’s Five MECHANICAL objectives
- develop a continously tapering cone / canal
- decreasing cross sectional diameters at every point apically and increasing at each point as the access cavity is approached (canal more narrow apically)
- maintain the original ‘flow’ of the canal (prepare in a multitude of planes)
- do NOT transport the foramen
- keep the apical opening as small as PRACTICAL
what is the ISO?
International Standards Organization
- standardized specifications to improve instrument quality
two primary goals of root canal instrumentation
- provide a biological environment (infection control) conducive to healing
- develop a canal shape receptive to obturation (filling material)
how do files work? shape vs a reamer?
enlarge canals with reciprocal insertion and withdrawal motions
3-4 sides with more spirals
how do reamers work?
shape vs a file?
cut and enlarge with rotational movements
3 sides with less spirals
barbed broaches and rasps function?
how are they made?
used to extirpate pulp and enlarge canals
does no cut/ machine dentin
good for removing cotton pellet in chamber or canal
made by hacking a round, tapered wire with a blade to achieve projecting barbs to cut/snag tissue
k-type instruments are either?
hand files or reamers
How do k-type instruments work?
Work by compression and release destruction of dentin in surrounding canal
- reaming motion has less transportation than filing motion
penetrating and enlarging canals
which has more flutes per length unit a file or reamer?
FILE
how are k-files made?
stainless steel wire ground to tapered square or triangular cross-section and then twisted
describe how to use a reamer and what is most useful for
used in a CLOCKWISE srew-in motion followed by a withdrawl stroke from the canal
used for shaping the CORONAL AND MIDDLE THIRDS of the canal
files are used for shaping what part?
the APICAL AND MIDDLE THIRDS of the canal
ISO files aka
K files
what does ‘D0’ signify
the diameter at the TIP is measured in 1/100 of a millimeter which corresponds to the file sizr
all ISO files have how many mm of cutting flutes on them? taper?
16 mm (same LENGTH of cutting flutes) with a 0.02 mm taper
in sizes #10-#60 what is the increase in diameter of the file at the tip when go up a size? #60-140?
- 05 mm between each larger file
0. 1mm between each larger file size
standard file lengths
21
25
31
Hedstromes (H-type) files are milled how? importance of that? use?
milled from a round steel wire with spirals milled into it
- sharper edges
- circumferential filing
- used in retreival of gutta-percha and seperated instruments
spiral edges to allow CUTTING only during a PULLING stroke
- has a positive rake angle
- CUTTING NOT SCRAPING
- SO SCRAPING PUSH PULL
reamers and files have what type of rake angle?
negative
File cross sections
- triangular
- square
- diamond
- teardrops
which is smaller/ bigger? triangular or square k- file?
which is more flexible?
smaller k file is square
bigger k file is triangular
in terms of tip cross section being triangular or square —
what has more cutting sides? which is more effective?
square has more sides but less efficient at cutting because angulation and space between where it would cut is less
in terms of tip cross section being triangular or square —
what has more cutting sides? which is more effective?
square has more sides but less efficient at cutting because angulation and space between where it would cut is less
two motions for hand files?
Reaming - rotation
push-pull - up down
sizes of gates gliden 1, 2, 3, and 4?
50, 70, 90, 110
describe gates glidden drills and their use
- engine driven
- latch attachment
- flame shaped
- used for opening orifices, gaining striaght line access and shaping the coronal third of canals
- should be used by BRUSHING against walls which are AWAY FROM the furcation area
What size file of gates gliden do you need if at WL with a size 40 file?
Atleast a #3 = 90
because size 40 file is .40 +. 02 x (.16) =.72
a number 2 gates wouldnt reach the working length
composition of rotary instruments
NiTi
- nickel titanium
- 56% nicel and 44% titanium
method of use for rotary
use at rpm between 150-600
generally in a CROWN DOWN tchniue
gentle pecking motion
flutes must be cleaned of dentinal mud between each insertion
how do rotaries ‘vary’
they can be used by varying
- tip size with same taper
- taper with same tip size
- vary both simultaneously
you want irrigants to have wat type of surface tension?
LOW
types of irrigants
- NaOCl ( 5.25 or half strength at 37 degrees celcius)
- H2O2 (hydrogen peroxide)
- saline
- chloroexidine
- Chelators (EDTA or Citric Acid)
best irrigant? WHY?
CLOROX
- Sodium hypochlorite
- antibacterial and DISSOLVES ORGANIC DEBRIS
medicaments used as chemical adjuncts in canal tx?
Calcium Hydroxide
Ca(OH)2 — most common and placed when one visit RCT is not indicated
- antibacterial
- high pH
dentin softening agents?
remove metal ions
examples are 17% EDTA or 10% Citric Acid
use of lubricant in RCT?
provide less friction for passage of files
EDTA + Glycerin (Endo-gel, RC Prep)
definition of working length?
RT vs AT?
Distance from a coronal reference point to a point where canal preparation and obturation should terminate
RT - radiographic terminus vs
AT - actual terminus
- ideally we want to fill up to the AT as RT could be off
Patency definition
Openness of the apical foramen
the apex should remain unblocked using a small file throughout the procedure
Definition of Recapitulation
Re-instrumentation of the canal with the same series of instruments previously used
Crown-down technique
Instrumentation of the root canal system from the coronal aspect towards the apex
Larger instruments are used first
Describe step-back technique
Instrumentation of the root canal system starting from the apex towards the crown
smaller instruments are taken to the working length then each larger instrument is subsequently worked to a shorter distance than the previously instrument
definition of stress
the deforming force measured across a given area
Stress concentration point definition
An abrupt change in the geometric shape of a file, such as a notc, which results in a higher stress level at that point along the surface of the file where the shape is more continuous
strain definition
the amount of deformation the file undergoes
Elastic limit definition
A set value representing the maximal strain that, when applied to a file, allows the file to return to its original dimensions.
after the strain is removed, the residual internal forces return to zero
elastic deformation definition
the reversible deformation that does not exceed thee plastic limit
- basically just before the point at which it would break
definition of shape memory?
what type of instrument is this a characteristic of?
a condition that exisit when the elastic limit is substantially higher than is typical for conventional metals
- it allows an instrument to regain its original form after being deformed
- ROTARY HAVE MEMORY
Plastic deformation definition
Permanent bond displacement, which occurs when the elastic limit is exceeded,
the file DOES NOT return to its original dimensions after strain is removed
Plastic limit definition
the point at which a plastic deformed file breaks
how to tell when K-file has had permanent deformation
When flutes wound more tightly or opened more widely
- should discard immediately as they will fracture during clock-wise motion after plastic deformation
describe body shape and pre-flaring
Confirmation of coronal patency and probing for curves, obstructions, and extra canals
advantages
- volume of irrigants early on
- prevents extrusion of necrotic debris beyond the apex
- allows for better tactile sensation to detect apical constricture
describe balanced force technique with file
Insert file and engage Clockwise into the dentin 1/4th turn
with continued pressure, go counter clockwise 1/2 turn to strip the dentin away (apply pressure apically)
do this 1-3 times before removing the file
remove clockwise
describe apical shaping and its componetns
After WL and MAF have been determined
- ‘deep shape’ provides resistance form for obturation
want a ‘seat’ not stop and not too open
what is master apical file and how do you determine?
apical gauging - determining actual size of apex and want to be at atleast a #30 with .0 taper with rotary or #35 with .04 taper
LARGEST BINDING FILE AT THE CORRECT WL
keys to successful apical shaping
- recapitualtion
- copious irrigation
- maintaining patency
- Respecting the anatomical constricture
CDJ definition
The region at which the dentin and cementum are united commonly
- itsposition can range from .5-3.0 mm from the anatomical apex
apical zipping creates what shape at the apex
a tear drop shape and this is what happens when you over instrument the apical area
definition of transportation
excessive loss of dentin from outer wall of a curved canal in the apical segment
- use a precurve file to limit chance of occurring
