History of Endodontics aae/abe

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Schilder 1974 – Principles of C&S canal system; C&S most important part of RCT; Serial Preparation technique; Foramen Transportation: Zip or Apical Perf

Design Objectives:

  1. Continously tapered funnel preparation from apex to access

  2. Narrower at every point apically

  3. Maintain original canal anatomy

  4. AF should be maintained at same position

  5. AF should remain as small as possible

  1. Wiene 1975Instrumentation errors (non-serial methods/no preflare): Elbow formation, Apical Transportationcuts outer wall below curve; Zip AF

Classic Instrumentation

  1. Walton 1976 – Compared effectiveness of Filing vs. Reaming vs. Step-back Filing; Findings: Step-back filing = highest % of pulpal walls planed, Reaming/Filing = more apical transportation; White shavings ≠ Clean

  1. Caldwell 1976 – Evaluated change in FWL before and after instrumentation (step-back filing) – Largest change in canals with greatest curvature (MB canal Max Molars) – NO statistically significant changes

  1. Abou Rass 1980Anti-curvature filing – pre-curve files to instrument away from “danger zones” – inner furcation areas

  1. Holland 1980 – Apical plugging of infected dentin chips = inflammation/abscess; see Tronstad for apical plugging with non-infected dentin chips

  1. Morgan/Montgomery 1984 – Compared crown down technique (personal correspondence: Marshall/Pappin) to traditional circumferential filing – Crown down significantly better in curved canals

Canal Preparation
Serial Preparation (See also: Schilder, Walton)

  1. Coffae/Brilliant 1975serial preparations (step back + coronal flaring) were more effective than non-serial preps (filing, reaming) in removal of tissue @ all 3 levels (1, 3, 5 mm)

  1. Walton 1976 – tapering prep (step-back filing) permits better debridement of apical canal, reduces overinstrumentation of foramen and improves ability to obturate compared to filing or reaming only; canal transport,  walls planed

Clem Step back (Serial preparation)

Goerig Step down (Alternating serialization)

Torabinejad Passive step back (shaping waves w/passive instrumentation)

Abou Rass Anti-curvature filing

Marshall/Pappin Crown down pressureless (Morgan/Montgomery)

Roane Balanced force

Discuss the benefits of the balanced force technique

  1. Roane/Sabala 1985 – CW (180 or <)/CCW (120 or >) - Restoring force of file (straightening force) vs. dentinal force to allow instrumentation of curve without transportation

  1. Wu/Wesselink – balanced-force technique produced a cleaner apical portion of the canal than the other techniques

  1. Sepicless apical transportation with balanced force technique in canals exhibiting curvature of more and less than 45 degrees.

  1. McKendry – Balanced force technique extruded less debris

  1. Calhoun – Using flex-R files balanced force produced more centered and round preps.

How does tip design effect preparation?

  1. Simon – Tip modification (removing transitional angle) as in Flex-R, along with hand instrumentation, produced better control of preparation and less ledging.

  1. Roane 1985Bi-beveled transitional angle tip (Flex-R file) produced the least transportation and no ledges – minimized excessive cutting force on leading edge

  1. Moser – Tip design contributes more to cutting and efficiency than flute design.

K3: Slightly + Rake Angle, Wide Radial Lands, Variable Pitch

Why CW rotation for files?

  1. Seto/Nichols 1990Rotations to failure: CW > CCW; CW: file must unwind, compression, reverse direction of flutes, tension, fracture vs. CCW: tension, fracture

Preflaring, is it a good idea? How does it effect working length?

  1. Stabholz/Torabinejad 1995 – Coronal Preflaring (Hedstroms/gates/US files) significantly  Tactile detection of AC (75% vs. 32%)

  1. Baumgartner – When using SS files with GG burs, it is best to measure WL after coronal flaring. When using NiTi rotary instruments, little difference is noted whether WL is measured before or after flaring.

  1. Ibarrola 1999 – Pre-flaring (ProFile NiTi) allows working length files to more consistently reach FWL and  efficacy of EAL (14/16 vs. 13/16)

  1. Roland 2002– Preflaring (vs. CD only) NiTi separation (.04 Series 29)

What about using a patency file?

  1. Paris – pass files through minor contriction to prevent dentin plug

  1. Mullaney – Patency file is defined as “a small flexible file that passively moves through the apical constriction without widening it” (Buchanan) It is thought to reduce the potential of forming a plug of infected dentin/debris in the apical 1mm.

  1. GoldbergApical transportation occurred when using a patency file (61% - #25 vs 25% - #10) Therefore use small files for patency.

  1. Vera 2012 – Maintaining apical patency (size #10, 1mm beyond AF) improved irrigation penetration in the apical 2 mm

  1. Ng 2011 – Maintaining apical patency improved success of NSRCT/RETX

Glide Path

  1. Varela-Patino 2005 – Creation of glide path w/ k-files #10-20  separation of NiTi rotary files (K3, ProTaper, ProFile)

  1. PetersNo ProTaper .04 rotary file fractured following glide path creation

  1. Beruti 2009 – Glide path: NiTi Path Files > SS files – less transp./canal


  1. Walia/Brantley 19881st to study NiTi for use in endodontic files – Compared #15 SS file with #15 NiTi (Nitinol ortho wire) file, Findings:

    1. NiTi is 2-3x more flexible than SS

    2. NiTi  Range of Elastic deformation (bending at 90)

    3. NiTi  Resistance to fracture, CW &CCW torsional rotation

  1. Wm. Ben Johnson – 1st NiTi rotary file (Series 29)

Compare hand stainless steel files with hand NiTi instruments

  1. Esposito/Cunningham 1995 – NiTi files (hand/rotary) were more effective in maintaining the original canal path of curved root canals when apical preparation was enlarged beyond #30

  1. Kuhn/Walker 1997 – NiTi files (hand) remained significantly more centered and demonstrated less apical transportation than stainless steel files at size 25. When preparation continued to size 40 with step back, NSD in transportation apically or coronally

  1. Zemner 1995 – NiTi files (hand) prepared more centered and tapered preparations than conventional K-files.

  1. Eldeeb – SS files > Size #25 - cause apical transportation/zipping

Compare hand stainless steel files with rotary NiTi instruments.

  1. Short/Baumgartner 1997 – Lightspeed and Profile NiTi files were faster and stayed more centered than stainless steel hand files (more pronounced at size #40 than #30)

  1. Hata/Toda 2002 – Rotary files (ProFile/GT) were faster than hand files (Flex-R) and decreased errors such as zip, elbow or ledge.

  1. Chen/Messer – Rotary instrumentation (Profile) may produce better canal shape versus stainless steel by reducing procedural errors.

  1. Tan/Messer – Lightspeed NiTi files allowed greater apical enlargement w/ significantly cleaner canals, less apical transportation, and better canal shape than SS hand files

  1. Zemner 1996 – Profile Rotary files more centered in canal than SS or US Files, more tapered preparation

  1. Dalton 1998 – Profile Rotary files = SS k-files (stepback) in bacterial reduction

Benefits of Pro Tapers

  1. Berutti – Pro Tapers are less elastic, can operate with higher loads without stress, is stronger than Profile. Pro Taper is idea for narrow curved canals.

  1. Yared – Pro Tapers even in electric high torque control motor is safe with the experienced operator. NOTE – Inexperienced operators fractured Pro Tapers even with a low torque motor.

  1. Peters – No Pro Taper instrument fractured when a patent glide path was present.

Do rotary instruments remove bacteria?


  1. Shuping/Trope JOE 2000 Profile rotaries and 1.25% NaOCl decreased bacteria 62%. Significant decrease in bacteria from S1 to S4 with larger file sizes. 1 week + exposure to CaOH2 decreased bacteria 92.5%.

  1. Bystrom & Sundqvist 1981Mechanical instrumentation reduced the number of bacteria 100 – 1000 fold and bacteria persisted even after 4 visits

  1. Law JOE 2004 – Review of literature on CaOH2 effectiveness as Intracanal medicament. She noted that the main component of antibacterial action is associated with mechanical instrumentation and irrigation w/NaOCl + EDTA. Yet can not render canals 100% free of bacteria (DTs, ARs, LCs). CaOH2 necessary for maximal microbial reduction for successful healing

  1. Gupta 2013 – Outcome, PAI, 12 months. Canal 3 file sizes larger than FABF

Does preflaring help with rotaries?

  1. Roland Preflaring of the canal was far less likely to result in file separation.

How much surface area does instrumentation clean?


  1. Peters – While instrumentation of canals increased volume and surface area, all instrumentation techniques left 35% or more of the canals’ surface area unchanged.

  1. Paque/Peters 2010Oval shaped canals (Distal canals, Mand Molars), left 60-80% of canal surface uncleaned. Instrumention of oval canal as 2 canals to improve surface area cleaned.

NOTE: May effectively debride only 20-40% of some canal shapes w/ files!!

What are the properties of NiTi?

Shen/Haapasalo 2013 – NiTi has 2 phases: Austenite & Martensite (3-D crystal lattice structure)

2 properties: Superelasticity & Shape memory (Martensitic phase)

  1. The ability to cycle between these two phases results in properties

  2. Phase transition occurs with rapid stress on the file, therefore use at a constant speed – Stress-induced Martensite transformation

  3. Heating: Martensite  Austenite (Final Af temp)

  4. Stress on file (during clinical use): Austenite  Martensite

  5. Martensite phase = super-elasticity, fatigue resistant

  6. Traditional SE NiTi: Austenite; CM & M wire: Martensite (based on Af)

  7. M wire (Vortex, ProTaper Gold): heat-patented proccess, alteration of Af

  8. R phase (TF, K3XF): heating/cooling patented process - R phase – twisted – cooled (TF), No alteration of Af

  9. CM: thermochemical process, alteration of Af, Inc flexibility, No shape memory

Discuss File Fatigue and Fracture


  1. Files are weakest during phase transition (cyclic fatigue)

  2. Radius of curvature was found to be the most significant factor in determining the fatigue resistance of files.

  3. Radius of curvature,  mass of metal,  resistance to fatigue

  4. Cyclic fatigue is a major cause of instrument failure.

Sattapan: 2 types of file fatigue

Cyclic Fatigue: result of rotation around a curve, repeated longitudinal extension/compression of the file with metal hardening and fracture

Torsional Fatigue: tip of instrument binds while file continues to rotate, ultimate strength of file is exceeded
Lin – To decrease the incidence of instrument separation utilize appropriate rotational speeds with a continuous pecking motion.

Gambarini – Low torque motor  Cyclical Fatigue

Gabel/Hoen – Slower speeds, ProFiles at 333 rpm separate 4x more than at 167 rpm

Yared/BouDahger – Use rotary files up to 10 canals (3 Molars)

Discuss M-wire, R-phase, and Controlled Memory NiTi Files

Shen/Haapasalo JOE 2013 - REVIEW

M Wire (Dentsply – GTX, Vortex): Patented heat treatment of file  increased elasticity and resistance to fracture, alters Af

R Phase (Sybron - TF, K3XF): Gambarini 2009; NiTi wire (Austenitic)  Heat treatment  Cooling  R phase  Twisting process  Electropolish = TF w/ super-elasticity, shape memory, and resistance to fracture

Controlled Memory Files (Hyflex, Vortex Blue): Thermochemical process, Reduced shape memory for increased flexibility, Alters Af

  1. Johnson 2008 – Profile 25/.04 (M wire) vs. Profile 25/.04 (NiTi) –  Cyclic fatigue w/ M wire

  1. Gambarini 2009 - TF (twisted R phase) > GTX (M wire) = K3 - Cyc Fatigue

  1. Lopes 2013 – R phase (K3XF) > M wire (Vortex Blue) > NiTi (K3/Revo): Flexibility, Cyclic Fatigue, Torsional Fatigue

Discuss M-wire, R-phase, and Shape Memory NiTi Files

  1. Celik 2013 – Compared Twisted Files (R phase) and GTX (M-Wire) with MTwo, ProTaper, and Race files (NiTi) and Flexo kfiles – TF = GTX = NiTi files > Kfiles

  1. Ninan 2013Controlled memory files (Hyflex, CM wire) showed greater flexibility compared to conventional NiTi (K3, ProFile) and M-Wire (Vortex, GTX) files

Discuss Electropolishing

  1. Herold 2007 JOE – ProFile > EndoSequence – Microfractures/File Separations at 300 RPM. Electropolishing did not inhibit microfractures

  1. Ray 2007 JOE – K3 > EndoSequence - Cyclic Fatigue, Electropolishing did not Inc resistance to cyclic fatigue. File design more important.

Compare M-wire vs. R-phase vs. Traditional NiTi

  1. Kim 2010 – Cyclic Fatigue Resistance: R-phase (TF) > Traditional (RaCe, ProFile, Helix)

  1. Al-Hadlaq 2010 – M wire greater flexibility and resistance to cyclical fatigue than Traditional NiTi

  1. Gambarini 2009 – R phase (TF) > M wire (GTX) = K3 (Traditional NiTi) for Cyclic Fatigue

  1. Lopes 2013 – R phase (K3XF) > M wire (Vortex Blue) > NiTi (K3/Revo): Flexibility, Cyclic Fatigue, Torsional Fatigue

Cyclic Fatigue

Rotations around curve, cycles of longitudinal tension/compression

  1. Haikel 1999 - Radius of curvature = Most significant factor for cyclic fatigue. Cyclic fatigue is a major cause of instrument failure. Radius of curvature,  mass of metal,  resistance to cyclical fatigue.

Discuss Instrument Fracture

Sattapan – 2 Methods of Failure: Cyclic fatigue, Torsional fatigue

Parashos/Messer 2006 – Review of Rotary NiTi Fracture:

  1. Spilli 20053.3% overall incidence of NiTi rotary fracture; NSD in overall healing rate of separated instrument vs. no instrument cases. Only PARL affected healing rate.

  1. Pantivisai/Messer 2010 – Meta-Analysis of instrument separation (Case control studies - Crump/Natkin & Spilli + Case Series): Healing: w/o PARL 92.4%, w/ PARL 80.7%; No  in Prognosis for Retained instrument alone.

Discuss Instrument Fracture

  1. Crump/Natkin 1970 JADA – No statistical difference between cases with separated instruments (81%) and control cases w/out separated instruments (73%)

  1. Iqbal 2006 (PennEndo) – Incidence in Penn Grad Endo clinic: Hand: 0.25%, Rotary: 1.68%, 6x more likely in apical 1/3rd, Mandibular molars most common (55.5%)

  1. Spilli 3.3% Overall Incidence, NSD in overall healing with presence of file. Only PARL affected healing rate.

  1. Pantivisai/Messer 2010 – Meta-analysis of Instrumentation separation (Case control studies: Crump/Natkin & Spilli + Case Series): Healing: w/o PARL 92.4%, w/ PARL 80.7%; No  in Prognosis for Retained instrument alone

Debris Extrusion: Instrumentation + Irrigation

  1. VandeVisse/Brilliant 1975 – Instrumentation + Irrigation = Debris exrusion; size 50 hand file =  Apical debris extrusion

  2. Hinrichs 1998 – Rotary files (lightspeed, Profile, series 29) – no difference in debris extrusion (related to amount of irrigation)

  3. Reddy 1998 – K-files/flex-R files (hand files) with push-pull technique had greater debris extrusion than lightspeed/Profile Series 29 (rotary files)

Does sterilization affect NiTi instruments?


  1. Hicks – Heat sterilization of rotary NiTi files up to 10 times does not increase the likelihood of instrument fracture.

  1. Casper/Van Himel 2011 – Steam heat autoclaving cycles up to 7 times did not affect torsional fatigue properties of Vortex, TF, and CM NiTi files

Prion Disease

  1. Misfolded proteins tranferred via contaminated instruments

  2. Causes neurodegeneration (psychosis, seizures, death)

  3. Sterilization may not eliminate prions – requires protein denaturation

  4. Spongiform encephalopathies: Creutzfeldt Jakob Diesease (humans), “Mad Cow” (cows)

  5. Reuse of NiTi rotary files comes into question due to Prions

Steam Heat Sterilization


  • Time: 30 mins

  • Temp: 121 C (250 F)

  • Psi: 15 Psi

  • Eliminates: Fungi, Bacteria, Viruses, Spores, NOT Prions

How fast do you run Pro Tapers, Pro Files?

  1. Martin – Pro Tapers 350 rpm were more likely to fracture than those used at 250 or 150 rpm. A decrease in the angle of curvature of the canal also reduced the likelihood of fracture.

  1. Dietz – Profiles .04 are less likely to break at lower rotational speeds

  1. Daugherty – Profile .04 Series 29 rotary instruments should be used at 350 rpm, which nearly doubles the efficiency and halves the deformation rate when compared to 150rpm.

  1. Gabel/Hoen – ProFiles at 333 rpm separate 4x more than at 167 rpm

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