Chapter 9: Shaping the RCS (Techniques)

1mm

by how much do irrigants progress farther from the needle tip if delivered passively?

zips and perforations

these preparation errors will leave parts of the RCS inaccessible for disinfection

0.3mm

this is considered a critical thickness of radicular dentin during preparation which will fracture the root

apical width

apical constriction

what are the two primary mechanical elements of cleaning and shaping the canal?

0.5-1mm for necrotic cases

1-2mm for irreversible pulpitis

what are the recommended termination points from the radiographic apex in (a) necrotic cases and (b) irreversible pulpitis

post-treatment disease

it is a term that refers to persistent or recurrent apical periodontitis due to blockage inside the apical canal areas

patency file

apical width

what are the 2 factors closely related to the preparation length?

patency file

is a small K-file passively extended through the apical foramen, and is believed to remove accumulated debris and help maintain working length

it may push contaminated debris through the foramen instead of having a cleaning effect, but this risk can be minimized if the canals are filled with NaOCl

what is a concern with patency files?

narrow apex

what kind root canal preparation has minimal risk of canal transportation and extrusion of irrigants?

narrow apex

what kind of root canal preparation has drawbacks that include:

- little removal of infected dentin

- questionable irrigation and disinfection

- not ideal for lateral compaction

wide apex

what kind of root canal preparation has better removal of infected dentin and greater access for irrigants and medications to the apical third?

wide apex

what kind of root canal preparation has drawbacks that include:

- greater risk of preparation errors and extrusion of irrigants

- not ideal for thermoplastic obturation

step-back technique

it is the traditional cleaning and shaping strategy, starting with small files and working towards larger files until a file can work to the full length

canal blockage or coronal binding

what may be the reasons why a patency file may not reach to the full working length of the tooth?

Coronal binding

is caused by overhangs at the orifice level and also occurs when the canal is less tapered than an instrument

shape of access cavity

what is the prerequisite before any canal preparation can take place?

crown-down

apical widening

step-back

hybrid techniques

CASH

what are the basic cleaning and shaping strategies for root canal preparation?

crown-down technique

this approach starts with using a large instrument followed by a series of smaller instruments to progress deeper into the canal until the terminus is reached

step-back approach

this approach includes working lengths decreasing in a stepwise manner with increasing instrument size

it prevents less flexible instruments from creating ledges in apical curves and produces a taper for ease of obturation

what is the advantage of step-back approach?

step-back technique

this technique was primarily designed to avoid preparation errors in curved canals

pre-enlargement

apical enlargement

apical finishing

what are the 3 phases of apical enlargement

10mm

what is the average length of clinical crowns

9-15mm

what is the average length of roots

danger zones

zones in radicular dentin where vertical root fractures and perforations are at greatest risk

coronal half or two-thirds the root length

what length of the root should pre-enlargement end at in a crown-down technique

standardized technique

this technique adopts the same working length for all instruments introduced into a root canal

step-down technique

this technique advocates shaping the coronal aspect of the root canal before apical instrumentation commenced, and facilitates lesser zipping near the AC

step-down technique

this technique is intended to minimize or eliminate necrotic debris that can be extended through the apical foramen, and allows apical instruments to be unimpeded through most of the length

double-flare technique

what is crown-down technique also called as?

in SDT, a stainless steel file is used to establish working length

in CDT, it relies on coronal flaring to establish working length

since both step-down technique and crown-down technique follows using larger to smaller instruments, what is the difference between the two?

balanced-force technique

this technique creates the least canal aberrations with K-files and has excellent canal-centering ability superior to other techniques with hand instruments

crown down and hybrid techniques

what techniques use both hand and rotary instruments?

step back

what technique only uses hand instruments?

coronal third: reaming

apical third: circumferential filing

what motion of instrumentation is used for step-back technique?

step-back technique

this technique is employed using 2% SS files and has the ability to prepare a proper apical stop

step-back technique

limitation of this technique is the extrusion of debris into the periapex and has a tendency to straighten the canal

reaming

what motion of instrumentation is used in a crown-down technique

crown-down technique

this technique has a tendency to gauge the apical third since it is the last phase of the procedure

crown-down technique

this technique allows easier shaping, elimination of bulk tissue and debris, minimizes debris extrusion, and better penetration of irrigants

previously used file

because the WL is the same

for crown-down technique, what file is used for recapitulation?

MAF

because the WL is different, it becomes shorter with each increasing instrument size so use MAF to recap

for step-back technique, what file is used for recapitulation?

coronal: reaming

apical: circumferential filing

what are the motion of instrumentations used for hybrid technique?

due to rapid increase in file size or accumulation of debris

malpositioned instrument stops

what causes loss of working length?

dentin chips

tissue debris

fractured instruments in the canal

what causes canal blockage?

ledging

an artificially created irregularity on the surface of the root canal wall that prevents placement of instruments to the apex of a patented canal

bypass

retrieval

what is the management for breakage of instruments in the canal?

type I

classification for bent instruments

type II

classification for instruments with stretching or straightening of twist contour without bending

type III

classification for isntruments with peeling or tearing of metal at the edges

type IV

classification for instruments with partial reverse twisting of instruments

type V

classification for instruments with cracking along the file axis

type VI

classification for a fractured instrument

zipping

transportation of the apical portion of the canal or straightening of the curved canal at the apical third

stripping

refers to the thinning of the lateral root wall with eventual perforation

Crown-down

profiles are used in what technique?