essay 40 - machine-driven endodontic instruments - types, classifications, characteristics, indications, working techniques. properties and limitations of NiTi instruments. Basic rules of working technique by machine-driven NiTi instruments

classifications of machine driven endodontic instruments

• classified based on material

— steel rotary instruments e.g Gates-Glidden or Largo drills

— NiTi rotary instruments e.g ProFiles or LightSpeed

list the steel rotary instruments

• Gates glidden drills

• Largo drills/Peeso reamers

Describe Gates glidden drills - steel rotary instruments

• used to eliminate coronal interferences and enlarge the coronal 3rd

• Size Start Point - #1 0.5mm

• always used after pre flaring with hand files

• elliptical (flame shape) cutting head, Flat Cutting blades, reduced aggressiveness and screw in tendency, not active cutting tip

• working technique; passive use with a brush like circumferential withdraw motion

• Available in Short (28mm/15mm working Part), long (32mm/19mm cutting part)

• 800 rpm

• designed to fracture at start of the Shank, Tip fracture only common in size one and two

Describe Largo drills/Peeso reamers - steel rotary instruments

• cylindrical shape, long cutting blades over a wider surface - non cutting tip. radial lands blade design

• Size Start Point - #1 0.7mm

• sizes 1-6

• more aggressive than Gates

• primarily for post space (dowel space) preparation - also used in retreatment cases for rapid removal of obturation material

• very aggressive due to extended active part - high risk of root stripping if used carelessly

• used with a passive, straight in and straight out motion - not a brushing or lateral movement

• not recommended for initial canal access or coronal enlargement - despite having a non cutting tip, early use Can be dangerous in unprepared canals

List the NiTi rotary instruments

• ProFiles

• Quantec

• LightSpeed

• Rotary GT Files

• Sybron Endo K3

• Pro Taper

• WaveOne

Describe Profiles - NiTi rotary instrument

• triple U’’ cross section with three radial ends (flat cutting surfaces); non cutting round tip;

• Depth Gauges at 18, 19, 20, 22 and 24mm (machined grooves on the shank that act as visual depth reference marks)

• reduced core metal mass → fragile to torsional stress, but very flexible and safe for curved canals

• working technique; crown down technique = .02, .04, .06; used with torque controlled handpiece at 250-300 rpm

• .02 taper: ISO sizes 15-45

• .04 and .06 taper: ISO sizes 15-80

• ISO standard colour rings:

— 1 ring = .02 taper

— 2 rings = .04 taper

— 3 rings = .06 taper

• Available in 21mm 25mm and 30 mm

• Recommended Speed: 250-300 rpm

• torque: low for .02/.04 tapers, medium for .06 taper

• shaping carved canals (high flexibility reduces transportation risk) less effective in coronal flaring or removal interferences

• prone to torsional stress and fracture in long/calcified canals

Describe Quantec - NiTi rotary instrument

• quantec Sc - cutting tip (faceted, 60 degrees, no transition angle) narrow, calcified canals with strong curvatures

• quantec LX - non cutting tip (blunt, 60 degrees) wider canals or with severe apical curves

• blades are asymmetrical radial lands behind contact area

• optimised debris removal and reduced friction

• working technique; progressive use, variable helical angle and cutting edge design improve saftey

• surface grooves to channel debris coronally. prevent apical compaction (‘‘dental mud’’ buildup)

Describe LightSpeed - NiTi rotary instrument

• resembles gates glidden, flame shaped with short working part and long shaft

• ISO sizes from 20 to 100

• non active rounded tip

• Available in length 21, 25, 31. must be used from smallest to largest in a step back sequence using a pecking movement

• first the canal is manually pre enlarged with a K file up to size 15. then the master apical rotary (MAR) is selected - it's the Lightspeed file that can reach working length using 12 gentle pecking motions. After establishing MAR, a step back sequence follows: larger files are inserted progressively shorter than the working length with 4-8 pecks each. the goal is to enlarge the canal coronally and middle 3rd to a diameter at least 0.25 mm larger than MAR. recommended speed for Lightspeed instruments is 1200-2000 rpm

• designed for accurate apical preparation with minimal shaping in the coronal and middle thirds

• ideal for apical enlargement in Curved canals. reduces transportation and over preparation in the middle and coronal thirds

• requires good tactile sensitivity and strict control of working length.

• not typically used for shaping the whole canal alone

• special feature; breakage point designed at 18 mm to allow safe retrieval

Describe Rotary GT Files - NiTi rotary instrument

• non cutting tip, radial lands, clockwise blade direction (unlike hand gt)

• low lateral cutting efficiency (do NOT aggressively cut dentin on their sides (laterally)), designed to imprint shape into the canal. radial Cutting planes - flat surface on the outer edge of a rotary file (not sharp angles)

• fixed tip diameter and maximum flute diameter (MFD)

• multiple tapers, blade length inversely proportional to Taper (longer the taper, shorter the blade)

• working technique: crown-down; adjust taper/diameter according to canal anatomy. use at 250-300 rpm with torque control

• continuous clockwise rotation (no screw in effect). Crown Down technique using decreasing taper/ diameter

• Selection Gutta percha cones, paper point, and obturators based on file used

• torque Low For 0.04 tapers, medium for 0.06 tapers and high for tapers above 0.06

• tip diameters; series of GT 20, 30, 40 and accessory sizes (up to .12 taper)

Describe Sybron Endo K3 - NiTi rotary instrument

• 2 radial lands (tiers): 1. support blade, 2. reduce wall friction, 3. stabilises and centre the file. non-working tip

• lengths available = 21 mm, 25mm, 30mm

• tapers and sizes = .02 (ISO 15-45), .04 and .06 (ISO 15-60), orifice openers: .08 and .10 tapers

• core diameter: decreases coronally → maintains flexibility

• cutting angle: slightly positive → efficient cutting

• handle design: short axxess handle → better access in posterior teeth

• working technique; crown-down after hand filling to size 15. use with a torque controlled motor and auto reverse

• crown down: decreasing diameter - decreasing taper - alternating both

• work until .06 taper size 25 or 30 reaches working length

• indication; thin, curved canals; short handle for posterior access

Describe ProTaper - NiTi rotary instrument

• Design and structure

  • Progressive taper, Convex triangular cross section

  • Composed of 6 files:

  • shaping files: SX, S1, S2 - progressively increasing taper, brushing motion

  • Finishing files: F1, F2, F3 - progressively decreasing taper, pecking motion

  • convex triangular cross section for high cutting efficiency

  • Variable taper and pitch (“spacing” or “interval” between the spirals of the file) to reduce screw in effect and enhance flexibility

  • torque controlled endomotor with auto reverse is recommended

  Sequence of Use

  1. initial hand instrumentation with at least A size 15 or 20 K-file and use irrigation

  2. SX: used to flare coronal 3rd and eliminate coronal interferences

  3. S1 files: prepares middle 3rd

  4. S2: reaches apical 3rd

  5. F1, F2, F3: Finish Shaping of apical 3rd depending on the final apical size needed

  6. brushing action used for shaping files (SX, S1, S2)

  7. In-out pecking motion without applicable pressure used for finishing files (F1-F3)

  8. Rotational Speed: 250-300 rpm with torque-controlled endomotor

Describe WaveOne - NiTi rotary instrument

• motion; reciprocating

• sizes; small (.06 taper), primary (.08 taper), large (.08 taper)

• lengths; 21,25, 31 mm

• M-wire NiTi for enhanced cyclic fatigue resistance

• indications; single-patient use (pre-sterilised), simplified instrumentation

• instruments: includes matching paper points, gutta-percha points and obturators

• Advantages:

— no sterilisation needed

— minimises file breakage

— maximised cutting efficiency per patient

what are the properties of NiTi instruments?

• high flexibility, therefore they are excellent for curved canals

• resistance to cyclic fatigue

• shape memory and super elasticity

• efficient cutting in lateral brush motion

• designed for rotary or reciprocating motion

what are the limitations of NiTi instruments?

• fragile under torsional and flexural stress

• require precise torque and speed settings

• need for torque-controlled handpieces with auto-reverse

• not suitable for aggressive cutting without control

• cannot be twisted like stainless steel - must be micromachined

Basic rules of working technique by machine driven NiTi instruments

• always explore and pre flare with hand files up to size #15-#20 before rotary use

• must have a glide path established

• work in crown-down sequence (reduce taper or diameter from coronal to apical)

• use and endodontic motor with torque control and auto reverse

• maintain rotational speed (typically 250-300 rpm for rotary NiTi)

• use short and gentle pressure, especially in curved canals

• use with frequent irrigation and lubrication

• avoid excessive apical force - use brushing motions with shaping files

• do not reuse single-use instruments like WaveOne to avoid cross contamination and breakage