Chapter 9: Shaping the RCS (File Systems)

histologic examination

what is the only method of proving whether a radiolucency is a cyst or not?

true cyst

this kind of cyst only heals after surgical enucleation

noncysts

this kind of cyst only heals by orthograde endodontic treatment without surgery

asymptomatic cases

is an orthograde approach of treatment beneficial for symptomatic or asymptomatic cases?

diffusion barrier

refers to the remaining dentin thickness

hard tissue deposition

stereotypical pulpal defense action to bacteria

reactionary/reparative dentinogenesis

refers to hard tissue being laid down as a response to a stimulus

secondary dentinogenesis

refers to hard-tissue deposition in response to old age

calcific metamorphosis

It is characterized by a reduction in the size of both the radicular and coronal pulp spaces

noninstrumentation technique

a minimally invasive approach to removing canal contents and accomplishing disinfection that did not involve the use of a file

pump

hose

special valve

what are used in the noninstrumentation technique?

merge

curve

recurve

dilacerate

divide

what are the 5 commonly encountered root canal paths

1mm

distance between the physiologic foramen to the anatomic apex

radiographic apex

radiographic or anatomic apex?

shaping at this apex will result in overinstrumentation past the foramen

false, vital pulp

true/false

barbed broaches are used to remove necrotic pulp tissue from the canal

batt tips

K-files with non-cutting tips

Flex-R file

a modified shape of K-files with smooth transitional edges between the tip and working parts

K-files

manufactured by twisting square or triangular metal blanks along their long axis, producing partly horizontal cutting blades

H-files

files that are milled from round, stainless steel blanks.

translational strokes

rotational strokes are discouraged

H-files are very efficient in what kind of strokes, and what strokes are discuourged?

H-file (up to #25)

can be used to relocate canal orifices and remove overhangs

GG drills

used for pre-enlargement of coronal canal areas

1. step-down sequence: start with larger-sized drills and progress to smaller size

2. step-back sequence: start with smaller-sized drills towards larger sizes

describe step-down and step-back sequences of using GG drills

750-1500 rpm

safest rpm to use GG drills

1. metal flash

2. rollover

what are superficial defects that are common in unused NiTi instruments

titanium nitride

added to improve the surface quality and cutting efficiency of NiTi instruments

1. superelasticity

2. high resistance to cyclic fatigue

what are the 2 properties of NiTi alloy that are of particular interest in endodontics, because it allows successful use in curved root canals?

group I: lightspeed

group II: ProFile

group III: ProTaper, RaCe

what are the 3 design groups of NiTi rotary instruments?

lightspeed (aka LS1)

NiTi rotary instrument design with long, thin noncutting shaft and short anterior cutting part.

Dr. Steve Senia

Dr. William Widley

who developed the LightSpeed file?

stamping

it is manufactured without a milling process

what is the manufacturing method of LSX instruments

LS1: 1500-2000 rpm

LSX: 2500 rpm

what are the recommended working speeds for LS1 and LSX?

LS1: U-shaped cross-section

LSX: flat chisel cross-section

what are the cross-section shapes of LS1 and LSX?

Dr. Ben Johnson (1994)

who introduced the ProFile system?

ProFile instruments

what instrument design of NiTi rotaries have increased tapers compared with conventional hand instruments?

29%

what is the constant proportion of diameter increments in ProFile instruments?

U-shape

what is the cross-section of a ProFile instrument?

150-300 rpm

what is the recommended working speed for ProFile instruments?

Greater Taper files (GT)

this NiTi design has decreased length of cutting flutes and increased the taper

Dr. Steve Buchanan (1994)

who introduced Greater Taper files

M Wire

what NiTi alloy type is used for GT/GTX files

#20 0.6 rotary

what GT file size is emphasized for usage?

300 rpm

what is the recommended cutting speed for GTX files

"high elasticity in rotation"

what does HERO file mean?

HERO file

these files are designed with positive rake angles allowing greater cutting efficiency, and has a cross-section similar to H-files but without radial lands

ProTaper files

a modified K-file with sharp cutting edges and no radial lands

convex triangle

what is the cross-section of a ProTaper file?

1. preparation of a glide path

2. more lateral "brushing" working stroke

what are the 2 usage characteristics of ProTaper files?

K3 files

these files have a slightly positive rake angle for greater cutting efficiency, wide radial lands, and a peripheral blade relief for reduced friction. but these files have a complicated manufacturing resulting in metal flash

Dr. McSpadden

who developed K3 files?

FlexMaster

these files have a triangular cross-section, with sharp cutting edges and no radial lands. these files also have minimal metal flash and rollover

Reamer with alternating cutting edges

what does RaCe file mean?

RaCe

these files have flutes and reverse flutes with alternating straight areas to reducing tendency of threading into the root canal

electropolishing

this process removes surface irregularities such as flash and burr marks to increase the surface quality of rotary instruments

EndoSequence

these files have a unique longitudinal design called alternating wall contact points to reduce torque requirements and keep the file centered in the canal

600 rpm

what is the recommended torque for EndoSequence

Twisted file

the first fluted NiTi file manufactured by plastic deformation

55% nickel

45% titanium

what is the composition of NiTi

2 1/2 full revolutions or 900 degrees

at what revolution will NiTi fracture?

Heat

it is speculated that this restores the molecular structure of used NiTi files resulting in increased fracture resistance

austenite

martensite

what are the 2 crystal phases of NiTi that give it its specific properties?

chloride corrosion

what causes micropitting in NiTi instruments?

torsional and flexural motion

what 2 rotary motions will break instruments?

torsional fracture

this kind of fracture occurs when the instrument tip is locked in a canal while the shank continues to rotate

flexural loading

this kind of fracture occurs when cyclic loading leads to metal fatigue

crown-down approach

this instrumentation approach is recommended to reduce torsional loads by preventing a taper lock

taper lock

occurs when a large portion of the tapered instrument engages the root dentin