Cleaning and Shaping of Root Canal Systems

A concise and brief presentation on cleaning and shaping of root canals. Colorful and well pictured. Ideal for UG students and PG students to get a good understanding of BMP techniques.

1. Cleaning and Shaping of Root Canal Systems Presented by: Dr Aaron Sarwal

2. Introduction Clinical evidence demonstrates that root canal systems can be cleaned and shaped and obturated in three dimensions with a high degree of predictability, approaching 100% success. The major objective of the root canal treatment procedure is to remove the contents of the pulp space and shape the walls of the canal to receive the filling material. Elements determining the predictability of successful endodontics.

3. Brief History In 1852 Arthur used small files for root canal enlargement. Ingle and Levine (1958) listed standardization for instruments. Ingle described conventional technique/ standardized taper  technique of root canal preparation. Almost 50 years ago, Schilder introduced the concept (and the expression phrase) "cleaning and shaping." Cohen’s Pathways of the pulp 10 th edition

4. Cleaning and Shaping Cleaning refers to removal of all contents of root canal system before and during shaping that is organic subtracts, microflora , bacterial by products, food debris, caries, denticles pulpstones previous root canal filling materials and dentinal shavings. Shaping refers to specific cavity form with five design objectives. Cohen’s Pathways of the pulp 10 th edition

5. Shaping of Root Canals Shaping process of the root canal can be classified into five phases-

6. Objectives of Cleaning and Shaping The primary objectives in cleaning and shaping the root canal system are to: Remove infected soft and hard tissue Give disinfecting irrigants access to the apical canal space Create space for the delivery of medicaments and subsequent obturation Retain the integrity of radicular structures

7. Herbert Schilder's Five Mechanical Objectives Schilder H: Cleaning and shaping the root canal, Dent Clin North Am 18:269, 1974.

8. Biological objectives: To completely debride the pulp space from- Pulp tissue Bacteria / Microorganisms Dentinal debris Endotoxins

9. Weine’s Rules For Canal Preparation Preparation must enlarge the canal while maintaining the general form of the preoperative shape, but it also must develop the most desirable shape to fill.

10. Weine’s Rules For Canal Preparation Once working length is determined all instruments should be kept within the confines the canal.

11. Weine’s Rules For Canal Preparation Instruments must be used extravagantly, especially the smaller sizes.

12. Weine’s Rules For Canal Preparation Canals must be prepared in wet environment

13. Motions of Cleaning and Shaping (Cohen, 6 th ed )

14. Motions of Instrument Manipulation Several motions of manipulation are useful for generating or controlling the cutting activity of an endodontic instrument. These may be referred to as envelopes of motion, historically Filing Reaming Turn And Pull Watch Winding Balanced Force Instrumentation. Anti-curvature Filing

15. 1. Filing The term filing indicates a push-pull action with the instrument. The inward passage of a K-type file under working loads is capable of damaging the canal wall very quickly, even when the slightest curvature is encountered.

16. 1. Filing Standard K-type file is pushed into a curved canal the junctional angles gouge the wall rather than reorient to the curvature. This action can form a ledge very rapidly.

17. 1. Filing The same motion with a modified tip produces little alteration of the canal wall since most of the cutting ability has been removed .

18. Circumferential Filing Instrument is first moved toward the buccal side, then reinserted & removed slightly mesially . This continues around the preparation to the lingual aspect & then to the distal untill all dentin walls have received rasping. Enhances preparation when a flaring method is used by widening the orifice of the canal. 6th ed. Pg 166/7 Weine Reaming action Keyhole Circumferential filing

19. 2. Reaming The term ream indicates clockwise or right-hand rotation of an instrument. Rotating any endodontic hand instrument to the right may be risky, though this risk is subtle and goes unnoticed until an instrument fractures under the load.

20. 2. Reaming

21. 2. Reaming

22. 3. Turn and Pull Motion A quarter turn to the right is followed by a straight outward pull. The arrow indicates a light inward force, which engages the file before rotation.

23. 4. Watch Winding Motion Watch-winding is the back-and-forth oscillation of a file (30 to 60 degrees) right and (30 to 60 degrees) left as the instrument is pushed forward into the canal.

24. 4. Watch Winding Motion The arched arrow indicates a gentle right and left rocking motion that causes the instrument to cut while light inward pressure (straight arrow) keeps the file engaged and progressing towards the apex. The arc of rotation is indicated by the shaded region in the circle.

25. 4. Balanced Force Technique (James B. Roane 1985) When file engages, with apical pressure, 1/4 turn (clockwise for all instruments according to Buchanan its easier for right handed dentists this way!) Then again, with apical pressure, 3/4 turn counterclockwise If done properly, at this time you will hear a "click" when the instrument is cutting dentine . Repeat sequence 2 or three time. The black arrow indicates that one should alternate these two directions until the working depth is reached. The inward pressure and the rotating force should always be very light.

26. 4. Balanced Force Technique (James B. Roane 1985)

27. Anti-curvature Filing Put forward by Abou-rass , Frank, and Glick Involves filing away from the inner curve of a root to reduce the risk of a strip perforation.

28. Anti-curvature Filing

29. Recapitulation Re-instrumentation with a smaller instrument following each irrigation step. Use of a smaller instrument to remove debris produced during instrumentation. Prevents pushing debris beyond the apex and apical plug formation.

30. Standardized Preparation John Ingle(1961) Same working length definition for all instruments introduced into root canal and relies on the inherent shape of the instruments to impart the final shape to canal. Negotiation of fine canals is initiated with fine files that are then advocated to WL and worked until a next larger instrument may be used. The final shape is predicted by the last used instrument. Hourglass preparation

31. FEATURES STEP- BACK STEP DOWN HYBRID AUTHOR CLEM AND WEINE 1969-74 GOERIG 1982 CONCEPT Involves preparation of the apical third initially followed by middle and coronal third of the canal using larger instruments. Involves preparation of the coronal two thirds of the canal first followed by middle and apical third of the canal Involves combination of crown down and step back techniques SEQUENCE OF INSTRUMENTATION RECOMMENDED INSTRUMENTS Hand instruments Hand and rotary instruments Hand and rotary

32. PRINCIPLE MOTION OF INSTRUMENTATION Coronal instrumentation with reaming motion and apical instrumentation with circumferential filing Reaming motion Coronal instrumentation with reaming motion and apical instrumentation with circumferential filing ADVANTAGES Popular technique employed with 2% SS files Ability to prepare proper apical stop Shaping is easier Elimination of the bulk of micro organisms, tissue and debris from middle coronal third before shaping apical third Minimizes debris extrusion Better penetration of irrigants Optimizes the advantages of crown down and step back techniques LIMITATIONS Extrusion of debris into periapex Tendency to straighten the canal Gauging of the apical third is done as the last phase of the procedure Middle third should be carefully prepared in order to prepare a continuous tapered preparation

33. STEP BACK PREPARATION (Telescopic, Serial root canal prep) Phase I Apical preparation up to the file #25(MAF) to full WL with recapitulation using prior size files.

34. STEP BACK PREPARATION (Telescopic, Serial root canal prep) Phase II Stepping back procedure in 1 mm increments Recapitulation with no. 25 file till full working length

35. STEP BACK PREPARATION (Telescopic, Serial root canal prep) Phase II-A Refining phase Gates Glidden no 2, 3, 4 are used to create coronal and middle preparations.

36. STEP BACK PREPARATION (Telescopic, Serial root canal prep) Phase II-B Return to # 25 last file (MAF) Short of working length to smooth the step back with vertical push- pull strokes (circumferential filing) H files used. Guttmann “final prep should be exact replica of original canal configuration”

37. STEP BACK PREPARATION (Telescopic, Serial root canal prep) Final Preparation Final form with smooth taper.

38. Modifications Of Step Back Schilder Advocated canal bed enlargement, shaping consisted of placing instrument larger than MAF to a point of 1st binding and then using reaming action to enlarge coronal portion, no force applied apically, Gates glidden used coronally Allows body of canal to be prepared without procedural errors, permits natural morphology Weine precurving of files to minimize canal alteration

39. Modifications Of Step Back Passive Step- Back Developed by Torabinejad uses a combination of hand and rotary instrument to develop flared preparation. Gradual enlargement of root in apical to coronal without application of force, rotating at 1/8 to one quarter turn Advantages: Reduces risk of apical transportation, removal of debris and canal obstruction, gradual passive enlargement Also advocated for use with ultrasonic instruments

40. Modifications Of Step Back Modified Step- Back The preparation is completed in the apical area, and then the step-back procedure begins 2 to 3 mm up the canal. This gives a short, almost parallel retention form to receive the primary gutta-percha point when lateral condensation is being used to fill the canal. Ingle 5th ed. pg530

41. Apical to Coronal Preparation: Advantages and Disadvantages

42. Coronal To Apical Preparation: Advantages and Disadvantages

43. Step Down Preparation First suggested by Schilder in 1974 Goerig 1982 named and described the technique in detail Principle- coronal aspect of the root canal is prepared and cleaned before the apical part

44. Step Down Preparation

45. Step Down Preparation Prepare the coronal portion of the canal to the depth of 16-18 mm or to the beginning of the curve using Hedstroem files 15,20,and 25 in a circumferential filling motion.

46. Step Down Preparation Gates Glidden drills 1,2 &3 are then used to refine the coronal preparation, the no 3 drill extending 1-2 mm into the canal orifice. A – No. 3 GG Drill B – No. 2 GG Drill C – No. 1 GG Drill

47. Rotary Instruments that are used in crown down technique are- Profile Profile GT Quantec Light speed protaper Race Hero 642 Hyflex K3

48. Modifications Of Crown Down Technique Crown Down Pressureless Balanced Force Technique Double Flare Technique

49. CROWN DOWN PRESSURELESS Suggested by Marshall and Pappin . Basic sequence similar to step down technique Used in rotary system and hand system with greater taper Early coronal flaring GG drills is followed by an incremental removal of dentin from coronal to apical direction- hence called as ‘crown-down’ technique. Straight K files are then used in large to small sequence with a reaming motion with no apical pressure- hence called as ‘pressureless’ technique.

50. Balanced Force Technique

51. Double-Flare Technique Fava presented this technique Consisted of exploratory action with small size file, a crown- down portion with K files of descending sizes, and an apical enlargement to size #40 or similar. He recommended stepping back in 1mm increment with ascending file sizes and frequent recaptulations with MAF

52. Hybrid Technique

53. Hybrid Technique

54. Non-instrumentation Root Canal Cleansing Lussi and his associates at the University of Bern, Switzerland, introduced devices to cleanse the root canal “without the need of endodontic instrumentation.” The first device, reported in 1993, consisted of a “pump” that inserted an irrigant into the canal, creating “bubbles” and cavitation that loosened the debris.

55. Mishaps During Cleaning and Shaping Loss Of Working Length Blockage Of The Canal System Ledging Breakage Of Instruments In The Canal Zipping Stripping Or Lateral Wall Perforation Overinstrumentation Overpreparation / Underpreparation

56. 1. Loss Of Working Length CAUSES: Due to rapid increases in file size and accumulation of dentinal debris in the apical one third of the canal Malpositioned instrument stops PREVENTIVE MEASURES: Frequent irrigation with naocl Recapitulation Periodic radiographic verification of working length Proper use of instruments stops Use of directional stops in Curved canals

57. 2. Blockage Of The Canal System CAUSES: Packing of dentin chips, tissue debris, restorative materials, cotton pellets, paper points or a fractured instrument in the canal

58. 3. Ledging A ledge is an artificially created irregularity on the surface of the root canal wall that prevents the placement of instruments to the apex of an otherwise patent canal CAUSES Inadequate access cavity preparation False estimation of pulp space direction Failure to pre-curve SS instruments Failure to use instruments in a sequential manner Attempt to retrieve separated instruments Attempt to prepare calcified canals

59. 4. Breakage Of Instruments In The Canal Causes of breakage Torsional fatigue Flexural fatigue Management Bypass Retrieval Prevention Knowledge of the physical characteristics of the instrument Flaws, such as shiny areas or unwinding are detected on the flutes Instrument bending or crimping occurs due to excessive use The file kinks instead of curving Corrosion is noted on the instrument

60. Classification of Damaged Instruments Type I Bent instruments Type II Stretching or straightening of twist contour without bending Type III Peeling or tearing off of metal at the edges without bending or straightening Type IV Partial reverse twisting of instruments Type V Cracking along the file axis Type VI Fracture of the instrument T . Sotokowa classified the types of damage to instruments: Unused Blunt Distorted

61. Retrieval of Separated Instruments Ultrasonic Tips Stieglitz forceps Perry gold foil pliers Peet splinter forceps Hartment 3½ CVD mosquito forceps Forceps

62. Masserann Kit - Introduced By Masserann EXTRACTORS TREPHAN BUR MASSERANN KIT

63. Masserann Kit – Technique of Application

64. 5. Zipping Refers to transportation of the apical portion of the canal It is characterized by a normally curved canal which has been straightened, especially in the apical third CAUSES Failure to pre-curve files. Rotation of instruments in Curved canals. The use of large , stiff Instruments to bore out A curved canal. APICAL FORAMEN TENDS TO BECOME TEARDROP SHAPED OR ELLIPTICAL

65. 6. Stripping Or Lateral Wall Perforation Refers to thinning of the lateral root wall with eventual perforation CAUSES Overzealous instrumentation In the mid-root areas of certain teeth, usually molars PREVENTION Use of anti-curvature filing. Clean & shape the canals using small files extravagantly & in a sequential manner. Avoid using large-diameter instruments as well as rotary instruments

66. Diagnosis Of Perforations The key factors for repair are immediate sealing of the perforation. Diagnosis Of Perforation: Apex locators Surgical microscopes Radiographs Paper points Bleeding Pain Loss of tactile sensation

67. Perforation Repair Materials MTA - latest, attaches to cementum, long setting time Glass ionomer - good flow Composite- curing is a problem at mid root level Zinc oxide eugenol - irritates the tissues IRM- less eugenol - less irritation Super EBA- less eugenol than IRM Gutta percha - for apical perforation Amalgam- not used any more

68. 7. Over-instrumentation Violates the periodontal ligament and alveolar bone. Loss of apical constriction creates: An open apex Lack of an adequate apical seal Pain & discomfort to the patient

69. Prevention of Over-instrumentation Using good radiographic technique Accurately determining the apical constriction of the root canal Using stable instrument stops placed perpendicular to the shaft of the instrument Retaining all instruments within the confines of the canal system. Occlusal refinement or reduction prior to working length determination and instrumentation Attention to detail during all cleaning and shaping procedures and Assessing the integrity of the apical stop with stiff paper points or files.

70. 8. Under-preparation It is the failure to remove pulp tissue, dentinal debris, and micro-organisms from the root canal system. Underprepared canals are best managed by adhering to sound principles of : Proper length determination Canal cleaning & shaping Recapitulation Treatment for overpreparation / underpreparation is “retreatment”

71. Conclusion Endodontist has a wide array of instruments and techniques at its disposal. Ni-Ti Rotary instruments need the practitioners expertise and one should use them in-vitro prior to clinical use Even the best of instruments have its limitations in the hand of an inexperienced practitioner. Experienced endodontist should choose tried and tested instruments and techniques.

72. References: Grossman’s Endodontic Practice 13 th Edition Cohen’s Pathways of the Pulp, 6 th Edition Ingles' Endodontics, 6 th Edition Weine’s Endodntic Therapy, 5 th Edition Essentials of Endodontics, Vimal Sikri