Instrument separation


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Instrument separation

  1. 1. Instrument Separation Introduction: • Instrument separation is classified under “Procedural Mishaps” • Instrument separation in the new terminology that is used replacing the old term instrument fracture. Types of Instruments that can cause obstruction in a canal apart form files and reamers: Gates – Glidden or Peeso drills, Lentulo spirals Thermomechanical GP compactors Tips of Hand instruments (explorers ; spreaders) Sectioned Silver Points (or) any dental material left inside the canal Common causes of Instrument separation: • Improper use (Overuse & Failure to discard when needed) • Limitation in Physical Properties • Inadequate access • Root canal anatomy • Possible manufacturing defects Factors Associated with fracture of NiTi rotary instruments. • Rotational Speed • Canal Curvature • Instrument Design and Technique of use • Torque • Manufacturing Process • Absence of a Glide Path Mechanism Associated with Instrument Blockage: Torsional Fatigue: Instrument binds to the walls of the canal and usually associated with excessive apical force applied during instrumentation
  2. 2. Bending Fatigue: Continuous stress applied to an instrument that is already weakened by metal fatigue and breakage occurs when it reaches its point of maximum flexure, when the stress is greatest and that is often seen in curved canals. Instrument fractures were present even during the use of Stainless Steel instruments, but with the introduction of NiTi into endodontics the incidence of occurrence of Instrument separation has increased. Treatment Planning: There are four basic options for treatment they are: • Nonsurgical retreatment • Surgical retreatment • Extraction of the tooth Factors Influencing Broken Instrument Removal: • Diameter, length and position of the obstruction • Canal Anatomy – Diameter, length and curvature of the canal • Thickness of the dentine • One third of the obstruction is to be exposed • Straight line position of the instrument • Positioning of the fragment in the canal • Stainless steel are easier to remove as no secondary fractures happen • NiTi can be fractured or pushed apically • Cutting direction of the fractured file • Ledge or Root perforations can cast doubt on the prognosis of the case Nonsurgical Retreatment Methods: Methods involving Nonsurgical removal of the fragment Methods involving no removal of the fragment Method Involving Non Surgical Removal of the Fragment: When the fracture of the instrument is at or above the level of Canal Orifices: • Hemostat • Steiglitz Forceps
  3. 3. • Modified Castrovicious needle holder • Perry Pliers When the fracture of the instrument is below the level of Canal Orifices: • Braiding Technique: Involves the use of several H – files. • Brasseler Endo Extractor Kit: includes a cyanoacrylate adhesive; four trephine burs and extractors. Recommended amount of overlap – 2mm, Disadvantage: the trepine burs are larger than their ISO equivalent, The bur cuts aggressively when new. • Masserann Kit : Trepine burs and extractor device, Gauge to aid in predicting the size to be used, different sizes of the burs available, Counterclockwise direction of the burs. Disadvantage: Excessive amount of radicular dentine removed. • Roydent Extractor Kit: Includes one bur and three extractors, the extractor tip contains six prongs. Disadvantages: lack of variety of instruments, potential breaking of the prongs, only to be used for the removal of small obstructions. • Wire Loop Technique: Roig – Greene first described, 0.14mm wire loop with ligature wire passed through a 25 gauge injection needle • Cancelliers: Includes an extractor tubes of four different sizes, used along with a cyanoacrylate adhesive. Designed to be used with an operating microscope. • Mounce Extractor: Its similar to a ball burnisher with slots cut into the ball, which slide onto the broken instrument. And a cyanoacrylate adhesive used. • Tube and H – files: A short stainless steel tube and a Hedstrom file. • Instrument Removal System (IRS): Include microtubes of different sizes with a side window and a 45 degree bevel and a side wedge with a taper towards its distal end.
  4. 4. • Separated Instrument Retrieval (S.I.R.): Include bonding agent, accelerator, five different sizes of tubes, assorted fulcrum props and a hemostat. • Ultrasonic Device: ProUltra ENDO tips are recommended they include ProUltra ENDO-3, 4, 5 which are stainless steel with a zirconium nitride coat; ProUltra ENDO-6, 7, 8 are made of titanium and available in thinner diameter and longer length. Staging Platform: Modified GG drill at reduced speed is directed apically in the canal until it lightly contacts the most coronal accept of the obstruction. Ultrasonic tip of suitable tip diameter, that could passively fit next to the obstruction and is activated at lower speed. Instrumentation is done under dry conditions. Water Port Technology disapproved: 1. water flow dampens the movement and decreases tip performance 2. small diameter tips are predisposed to breakage when mechanized for internal water flow 3. unrequired aerosol effect 4. moisture from water, along with dentinal dust creates mud that can cause potential iatrogenic outcome
  5. 5. Title: Removal of Separated Files from Root Canals With a New File – Removal System: Case Reports Authors: Yoshitsugu Terauchi, DDS; Le O’ Leary, DDS and Hideaki Suda, DDS, PhD Journal of Endodontics, Vol 32, No 8, August 2006 AIM: To test a new clinical technique for the removal of separated files form root canals with curvatures and with different level of breakage of the instrument. INSTURMENT REMOVAL PROCEDURE: New Technique for Instrument Removal: • This new system involves  three steps that consists of  three different techniques and  three newly designed instruments. • Each step is performed sequentially until the separated file is removed. • STEP 1 • The goal of this step is to establish straight line access to the separated file with minimal removal of the dentin to conserve the root structure. • Two types of low-speed cutting burs with 28-mm lengths were developed. • The first one is referred to as Cutting Bur A (CBA). • It has a pilot tip that follows the path already created by the separated file. • Used to enlarge the canal wall so that  second bur can be easily introduced into the canal and  brought into contact over the coronal portion of the separated file.
  6. 6. • The second bur is referred as Cutting Bur B (CBB). • Cylinder-shaped tip  cuts at the periphery of the separated file  acts as a trephine bur that slightly machines down the coronal portion of the file. • This provides a guidance space for the ultrasonic tip that is subsequently used in the second step. • The diameter of the • CBA is 0.5 mm • CBB is 0.45 mm. • The CBB is smaller than the CBA  its main objective is to machine down the separated fragment, without removing additional dentin. • Both burs can go around a curved canal as they are flexible in the shanks. • They also share a mechanical function of loosening the separated file wedged in the canal because they are used in a counter-clockwise motion in the low speed handpiece. • The counter-clockwise motion • imparts an unscrewing effect to the separated instrument that helps loosen it. • If the separated file was already comparatively loose from the canal wall or is shorter in length than the CBB, it could be accidentally removed at this stage. • If the file removal attempt is unsuccessful at this point, the clinician should proceed to Step 2. • STEP 2 • The purpose of this step is  to conservatively trim away the dentin and  expose the coronal few millimeters of the separated instrument and to loosen it.
  7. 7. • A specially designed ultrasonic instrument was developed to prepare the periphery of the file. • The length of this ultrasonic instrument is 30mm. • It was designed to reach separated file lodged in the apical third of a long canal. • The ultrasonic tip size is small, measuring 0.2 mm in diameter, to minimize the amount of dentin removal. • Direct contact of the ultrasonic tip with the separated file should be avoided to prevent a secondary fracture; • ultrasonic vibration is focused on the remaining dentin around the file or the floor of the cavity prepared by the CBB. • The process of uncovering the coronal segment of the separated file with the ultrasonic instrument may result in its early removal. • The final step should be attempted if the separated file is irretrievable after adequate exposure of at least 0.7 mm of the coronal portion of the fragment. • STEP 3 • This stage involves a device that would mechanically engage the fragment to retrieve it. • A file removal device was developed to directly grab the file out of the canal. It consists of two assemblies. • One part consists of a head connected to a disposable tube (0.45 mm in diameter) with a loop made of NiTi wire (0.08 mm) projecting from it. • The other part is a brass body equipped with a sliding handle on the side that holds the wire of the head attachment. • The main purpose of the handle is to control the wire of the loop.
  8. 8. • When the handle is moved downwards it will help fasten the loop and vice versa. • The wire protruding from the tube is used to create the loop. • The loop size can be adjusted to the size of the separated file by manipulating the handle. • The coronal portion of the file must be exposed by at least 0.7 mm for the system to be effective. • Once the fragment is sufficiently exposed, the loop is placed over the coronal portion of the separated file and then fastened to secure the fragment. • The obstruction is retrieved by pulling the apparatus out of the canal in various directions to dislodge the fragment from the canal walls . Other methods of Retreatment for the removal of separated instruments: 1. If the fragment is within the canal – Bypassed – Lubricant used – Canal preparation completed – Canal filled – The segment becomes part of the filling material 2. If the fragment cannot be bypassed – Prepare and fill the canal to the level to which the instrument can be accomplished Crump and Natkin 1970 J. Ame. Dent Asso. Fox. J. et al 1972 NY State Dent J Success following instrument separation is equal to that of teeth without such mishaps. 3. If the fragment is beyond the apex – Apical surgery – First step is to complete cleaning, shaping and filling of the canal – Surgery include removal of part of the fragment exactly beyond the apex and retrofilling is done. Prognosis of the cases of instrument separation is dependent on the stage of canal instrumentation at the time of separation of the instrument. CASE REPORT:
  9. 9. Case 1 • 37 yr old female – retreatment of mandibular left second molar • c/f: sensitive to percussion • radiographycaly: appox 5mm of the instrument in the apical third of the distal canal with 2.0mm of the segment beyond apex • GP removed with rotary NiTi, coronal portion straight-lined • Microscope is used • File removed in 7min’s • Retreatment done with GT rotary NiTi. Case 2 • 15 yr old male – retreatment of mandibular left second molar • c/f: sensitive to percussion • radiographycaly: appox 5mm n the apical third of the distal canal • GP removed from mesial roots • File removed in 5min’s • Retreatment done with GT rotary NiTi Case 3 • 42 yr old male - retreatment of mandibular left third molar • c/f: sensitive to percussion • radiographycally: appox 8mm of instrument in the apical third of mesial canal • time: 6min’s • Retreatment done with GT rotary NiTi Case 4 • 28 yr old male – Right mandibular first molar • c/f sensitive to percussion • radiographycaly: appox 4mm of the instrument in the apical third of the mesial canal with periapical radiolucencies around both mesial and distal roots. • GP removed with rotary NiTi • Time: 12min’s • Perforation repaired with MTA • GP filled using Obtura
  10. 10. DISCUSSION: Wilcox et al showed that canal enlargement of 40 to 50% of the root width increases the roots susceptibility to vertical fractures Ward et al reported that use of ultrasonic technique at times can cause portion of the separated instrument to break off and cause secondary fracture especially among NiTi Suter recommended the removal attempt to remove fractured instrument should not exceed 45 to 60 minutes. Success rate may drop with increase in treatment time, this may be because of: • Operator fatigue • Over enlargement of the canal (perforations) Hulsmann reported a success rate of 55 to 79% for the removal of separated instruments. Suter reported 87% success rate with his definition of success as the complete removal of the separated instrument from the root canal without preparations. Fracture fragment located Before the canal curvature – 100% success rate At the level of curvature – 60% Below the level of curvature – 31% CONCLUSION: The best antidote for broken instrument is prevention. By following certain factors the breakage of the instrument can be avoided. Guidelines for when to discard and replace instruments: • Flaws such as shiny area or unwinding are detected on the flutes • Excessive use has caused internal bending or crimpling. A major concern with NiTi instruments is that they tend to fracture without warning; as a result, constant monitoring of usage is critical. • Excessive bending or precurving has been necessary. • Accidental bending occurring during file usage. • The file kinks instead of curving. • Corrosion is noted on the instrument
  11. 11. • Compacting instrument have defective tips or have been excessively heated.