Rotary files and Radiographic Interpretation Flashcards
what technique of taking radiographs is ideal?
Paralleling technique
Describe Paralleling technique
Long axis and Root is perpendicular to the sensor
Describe bisecting technique
Adjust cone/ source of radiograph
SLOB rule
same lingual
opposite buccal
meaning if it moves opposite it is buccal to the other object
a buccal object moves relative to? in what direction?
a buccal object moves relative to a lingual object
it moves in the SAME DIRECTION the x-ray beam is DIRECTED
The x-ray beam can changed in what directions?
in a horizontal or a vertical direction
what root will most likely always be longer on maxillary and mandibular first molars?
PALATAL (lingual)
indications and advantages of cone shift for radiographs?
- separation and superimposed canals
- determination of working length
- determiniation of curvature
- determiniation of facial/lingual locations
- movement of superimposed structures
why does nickel titanium work the way it does? its two characteristics too
- SHAPE MEMORY
- SUPER-ELASTICITY
56% Nickel
44% titanium
Due to the transformations it goes through :
it has TWO CRYSTALINE PHASES/ STRUCTURES
1. Austensite
2. Maternsite
*goes through physical changes as we use it
never put a rotary where?
WHERE A FILE HAS NOT GONE
Stress-strain relationship
stress increases? the strain will increase as well at an exponential rate
elastic limit
- describe what is seen?
permanent deformation occurs here
difference between stainless steel and NiTi in terms of stress-strain relationship
larger range of stress you can put on it before it becomes elastic deformation
- then will also eventually get plastic deformation – then fracture
plastic deformation characteritstic?
comes after the elastic limit (permanent deformation)
Fracture limit – will break
shaping ability of rotary vs SS hand instruments?
studies have shown that in extracted human teeth, rNiTi maintains the original canal curvature better than SS hand instruments
- especially in the apical region of the root canal
- studies have shown that NiTi is significantly better than SS when the apical region was enlarged > 30
percentage of canal dentin that is untouched, regardless of instrument type?
35%
Cleaning ability of NiTi rotary?
Most CANNOT completely clean and instrument the root canal system so it reinforces the importance of antibacterial IRRIGATION for disinfection of the canal system
working time with rotary?
dependent upon the operator factors and the preparation technique rather than the instrument type
two types of fatigue that occurs?
- torsional fatigue
2. cyclic fatigue
definition of cyclic fatigue
continuous rotations around a curvature result in repeated expansion- compression cycles that lead to metal fatigue and fracture
rotation in curved canals will bend instruments once per rotation, which ultimately will lead to work hardening and brittle fracture – known as cyclic fatigue
definition of torisional fatigue failure
friction or holding the tip while the remainder continues to turn past the plastic limit
common rotary file usage problems
- too much pressure on the handpiece
- inconsistent RPM
- not doing a “crown down” technique (need to be open coronally first with these so they can work in the lower parts of the canal)
minimum file you need to use for glide path before rotary use?
20 file
first three rotary files used
color and size with taper
SX - shaper X
0.19 / .04
S1 - purple (like the 10 or 12)
0.18 / .02 taper
S2 - white (like the 15)
.20 / .04 taper
