Glide path in endodontics

Glide Path in Endodontics

1. Glide Path in Endodontics Dr. Deepesh Mehta (Batch 2018) 1

2. Content Introduction Importance of Glide Path Methods of Preparation Hand Stainless Steel Files Reciprocating Files NiTi Rotary Files Case Report Conclusion References 2

3. Introduction The endodontic glide path is defined as a smooth, patent passage from the coronal orifice of the canal to the physiologic terminus or electronically determined portal of exit. A successful glide path is an uninterrupted passage that can be reproduced when small-size files are used in sequence in the canal. 3

4. The Glidepath can be short or long, narrow or wide, essentially straight or curved; without the endodontic Glidepath , the rationale of endodontics cannot be achieved. 4

5. The glide path can be achieved with both hand and rotary instruments. The use of hand files, however, has been shown to be more time consuming, particularly in teeth with constricted and/or severely curved canals. Over the last few years, research has repeatedly shown that NiTi glide path rotary instruments are capable of achieving a safe and predictable glide path in comparison with hand files. 5

6. Mechanical (NiTi) glide path systems have been shown to improve the glide path prior to the use of NiTi shaping instruments. Systems like the ProGlider (Dentsply Sirona , Ballaigues , Switzerland), and G-Files (Micro-Mega, Besançon , France) are said to preserve the original canal anatomy and cause fewer aberrations and modifications of canal curvature. 6

7. Importance of Glide Path Nickel-titanium (NiTi) rotary instruments were introduced to improve root canal preparation. In clinical practice these instruments are associated with an increased risk of fracture, mainly because of bending normal stresses (failure by fatigue) and torsional shear stresses (failure by torque). 7

8. Various aspects might contribute in increasing these stresses, such as excessive pressure on the handpiece , a wide area of contact between the canal walls and the cutting edge of the instrument, or if the canal section is smaller than the dimension of the non-active or non-cutting tip of the instrument, the latter case might lead to a taper lock, especially with regularly tapered instruments. 8

9. The risk of taper lock might be reduced by performing coronal enlargement and creating a glide path before using NiTi rotary instrumentation, both manual and mechanical. What the rationale of endodontics requires is the entire length of the root canal system be cleaned and shaped. Glide path is pre requisite to this mechanical objective. 9

10. The lack of glide path establishment may result in: Ledge Formation. Blockage of root canals. Transportation. Zip Formation. Perforation. A glide path helps prevent torque failure and cyclic fatigue. Initially, when rotary files were introduced there was no recommendation for glide path creation. Subsequently, instrument fracture became a significant issue until glide path creation became known as an adjunct to safe rotary use. 10

11. A glide path is now recommended by virtually all manufacturers of rotary nickel titanium files. Without a glide path, rotary files can easily screw themselves into canals by engaging more dentin than ideal and separate. The glide path assures the operator that the tip of the file will not become locked as it moves apically and that the canal is free and clear of significant debris and blockage. 11

12. Glidepath can be further described as a manual glide path created with handfiles , or a mechanical glide path created with rotary files. 12

13. 13

14. Methods of Preparation Hand stainless steel K-files: West (2006) recommended using stainless steel K-files in a vertical in and out motion with an initial amplitude of 1mm, gradually increasing as the dentine wall wears away and the file advances apically. In very narrow canals a “watch-winding” motion is recommended to remove restrictive dentine, as well as to create an “envelope of motion”. 14

15. West and Roane describe the “watch winding” motion as a back and forth oscillation of a file (30 to 60 degrees) clockwise and counter-clockwise as the instrument is pushed downward into the canal. It is a definite inward progression of the instrument in a filing motion. An “envelope of motion” occurs when a precurved file is advanced into the canal short of maximum resistance, then the file is removed while it is simultaneously rotated in a clockwise direction. 15

16. Schilder (1974) emphasises the need to use precurved hand instruments. The “envelope of motion” created by the rotation of the curved file as it is withdrawn from the canal scribes the side walls of the canal at random contact points, gradually widening and evolving the root canal shape to allow larger files to follow. This technique facilitates the suspension of debris in the irrigation solution. 16

17. Both Schilder and West emphasise the importance of following the canal rather than forcing the file apically through any obstructions. West recommends a minimum of a “super loose” size 10 K-file. This author also emphasises that if a glide path larger than size 10 K-file is required then it is advisable to use the “balanced force” motion 17

18. This involves turning the handle of the file clockwise, and then turning it counter-clockwise using slight apical pressure so that the file does not “unscrew” its way out of the canal. During the clockwise motion, the file blades engages into the dentine and during the apical counter-clockwise motion, the loose dentine is collected into the file’s flutes. This motion can be repeated several times as the file is advanced apically. 18

19. In order to confirm that a glide path is present, a size 15 or 20 K-file should slide easily to working length. Advantages of using hand files: K-files provide better tactile sensation. Less potential for separation. When a small size k-file is removed from the canal, the file often retains an impression of the canal, and in this way alerts the operator to the curvatures present in the canal. 19

20. The stiffness of stainless steel hand files aids in path-finding and in negotiating blockages and calcifications. Lower cost. No need for a dedicated hand piece. The disadvantages are: Operator fatigue. Hand fatigue. Time required in the preparation of the glide path. 20

21. Risk of the introduction of canal aberrations with larger file sizes. Greater change to original canal anatomy. Increased apical extrusion of debris. 21

22. Hand files in reciprocating hand piece: This technique involves using small size K-files mounted in a reciprocating hand piece in the preparation of the glide path. A small size K-file is used to negotiate the canal to length by hand before being attached to a reciprocating hand piece. The hand piece is then moved vertically up and down, with an amplitude of 1mm to 3mm and bursts of reciprocation for approximately 15 to 30 seconds in each root canal. 22

23. Sequentially larger size K-files (06 to 10) are inserted to just beyond the apical constriction to reduce the risk of blockage. Due to the relative stiffness of the file, Van der Vyver recommends placing a size 20 K-file one mm short of the apex during this method of glide path preparation to avoid apical transportation. 23

24. The advantages: Reduced preparation time. Reduced operator fatigue. Reduced hand fatigue, especially in canals with multi-planar curves; Reduced risk of instrument separation compared with rotary NiTi methods. 24

25. The disadvantages are: The need for a dedicated hand piece. Risk of apical transportation with files larger than a 15 K-file. Risk of excess dentine removal as a result of the clinician working the canal longer than necessary. Risk of apical extrusion of debris if hand piece is inserted apically with force. Decreased tactile sensation. 25

26. Rotary NiTi files: PathFiles (Dentsply/ Maillefer ): PathFile NiTi rotary files (Dentsply/ Maillefer ) were introduced to the market in 2009 specifically for the purpose of glide path enlargement. The system consists of three instruments which are available in 21mm, 25mm, and 31mm lengths. 26

27. They have a square cross section and a 2% taper, which makes them resistant to cyclic fatigue, ensures flexibility and improves cutting efficiency. The tip angle is 50 degrees and is non-cutting, which reduces the risk of ledge formation. PathFile No.1 (purple) has an ISO 13 tip size, PathFile No.2 (white) has an ISO 16 tip size and PathFile No.3 (yellow) has an ISO 19 tip size. 27

28. The gradual increase in tip size facilitates progression of the files. The manufacturer suggests using the PathFile No.1 only after a size 10 K-file has been used to explore the root canal to working length. 28

29. X-PLORER™ Canal Navigation NiTi Files (Clinician’s Choice Dental Products Inc., New Milford, USA): The X-PLORER™ series of rotary NiTi files for glide path preparation was introduced in 2010 and consists of three instruments. They are each available in lengths of 21mm and 25mm. 29

30. The unique design features of these instruments are their cutting surfaces, tapers and cross sections. The cutting surface is limited to the apical 10mm of the file, which decreases surface contact and torsion and increases tactile feedback. The non-cutting tip has a 75 degree tip angle. The manufacturer recommends using the X-PLORER series after a size 8 or size 10 hand file has been used to penetrate the canal to working length. 30

31. G-Files (Micro-Mega, Besancon, France): These glide path preparation instruments were introduced in 2011. The system consists of two files which are available in 21mm, 25mm and 29mm lengths. The tip sizes are ISO 12 and ISO 17 and the non-cutting tip is asymmetrical to aid in the progression of the file. 31

32. The files have a 3% taper along the length. The cross section of the file has blades on three different radii to aid in the removal of debris and to reduce torsion. The files have an electro-polished surface to improve efficiency. The manufacturer recommends their use after a size 10 hand file has been used to explore the canal to working length. 32

33. EndoWave Mechanical Glide Path (MGP) (J Morita, California, USA) The EndoWave Mechanical Glide Path kit consists of three files that can be used to enlarge the glide path. EndoWave MGP file No.1 (purple) has an ISO 10 tip size, file No.2 (white) has an ISO 15 tip size and file No.3 (yellow) has an ISO 20 tip size. 33

34. All three instruments have a constant taper of 2% and can be rotated at 800 rpm at a torque of 30gcm or 0.3N/cm. 34

35. Scout- RaCe files (FKG Dentaire, La Chaux-de-Fonds, Switzerland ): Scout- RaCe files (FKG) are 2% tapered instruments which have been electro-polished to remove any irregularities formed during grinding and have a triangular cross section. The system consists of three instruments with a RaCe flute design (alternating cutting edges) and noncutting tip. 35

36. They are available in ISO tip size 10 (purple), 15 (white) and 20 (yellow) and should be used in a sequential manner (600 rpm) after initial canal exploration with a size 06 or 08 K-file to working length. 36

37. RaCe ISO 10 (FKG Dentaire): RaCe ISO 10 is another system from FKG and consists of three files that progressively increase in taper: 2% (yellow disc), 4% (black disc) and 6% (blue disk). All have the same apical diameter of 0.1mm. 37

38. The main indications for these instruments are constricted and obliterated canals, as well as abrupt coronal curvatures. These files will scout the canal and also create coronal preflaring because of the increasing taper of the instruments. 38

39. The advantages of using NiTi rotary instruments: Reduced operating time. Reduced canal aberrations (ledges, zips and apical transportation). Better maintenance of original anatomy. Less operator fatigue. Less hand fatigue. Reduced apical extrusion of debris. Reduced post-operative pain. An easy-to-learn technique. 39

40. The disadvantages of using NiTi rotary instruments: Additional cost. Increased risk of file fracture. Decreased tactile sensation. 40

41. In 2011 Van der Vyver also described a combination method for glide path preparation: Stainless steel K-files (sizes 06 up to 10), are sequentially progressed to working length using a watch-winding technique. The files are then inserted into a reciprocating hand piece and the initial glide path prepared. This is followed by glide path enlargement with rotary NiTi. 41

42. CASE REPORT A patient, a 70-year-old male, reported with irreversible pulpitis affecting his maxillary first left molar. The tooth provided an abutment for a three-unit zirconia bridge. A periapical radiograph revealed possible curvatures in the mesiobuccal and distobuccal root canals. It was decided with the consent of the patient to take a limited field of view CBCT scan to explore the anatomy of this tooth. 42

43. The data of the limited field of view CBCT scan was exported as a DICOM files and imported into the 3D Endo Software. The 3D Endo software confirmed severe curvatures in the two mesiobuccal root canals and an apical curvature in the distobuccalroot canal. The software projects the proposed root canal instruments into the canals, allowing the operator to visualize the internal anatomy of the root canals. Note the severe midroot curvatures in the two mesiobuccal root canals and in the apical part of the distobuccal root canal. 43

44. At a following visit the tooth was anaesthetized, a rubber dam placed, and an access cavity was prepared. The canals were located under magnification. Canal negotiation and glide path preparation: The pulp chamber was filled with Glyde Root Canal Conditioner (Dentsply Sirona ) and canal negotiation was initiated with a pre-curved size 08 K-File. It was possible to negotiate the palatal and distobuccal canals to patency. 44

45. It was only possible to negotiate the mesiobuccal canal to approximately two thirds down the length of the mesiobuccal root canals before resistance was met (fig - a). It was decided to flare the coronal aspect of the canal with a WaveOne Gold Glider (fig - b). The larger coronal flare of the canals allowed a size 08 K-File to progress to patency (fig - c). 45

46. Working length measurements were obtained from an electronic apex locator and confirmed radiographically . The size 08 K-File fitted very tightly into the root canals and it was decided to prepare a reproducible glide path for each root canal system with the size 08 K-File in a M4 Reciprocating hand piece (Sybron Endo), followed by repetitive instrumentation to make a size 10 K-File super loose. Thereafter, a WaveOne Gold Glider (Dentsply Sirona ) was used in reciprocating motion to expand the glide path up to full working length. 46

47. Root Canal Preparation, Irrigation and Obturation: The two mesiobuccal and the distobuccal root canal systems were prepared with the Small Wave One Gold instrument and the palatal canal was prepared with the Primary Wave One Gold instrument. After canal preparation, the canals were flooded with 17% EDTA solution ( Ultradent ) and the solution activated for 1 minute with EDDY Endo Irrigation Tip (VDW) driven by an air scaler ( Soniflex LUX 2000L, KAVO). 47

48. Thereafter, final disinfection was achieved by activating 3.5% heated sodium hypochlorite for 3 minutes, again activated with the EDDY Endo Irrigation. The canals were dried with paper points and obturated using matching gutta-percha points, Pulp Canal Sealer (Kerr) and the Calamus Dual Obturation Unit (Dentsply Sirona ). 48

49. CONCLUSION Grossman states that “a dentist who has not separated an instrument has not done enough root canals”. This threat of instrument fracture remains in contemporary endodontics. The preparation of a glide path not only helps to reduce the risk of instrument separation but also conveys to the clinician an intimate knowledge of the tortuous anatomy of the canal from the orifice to the terminus. 49

50. The endodontic glide path is the secret to radicular rotary safety and marks the path of modern endodontics. Routine glide path establishment and enlargement with glide path files can increase the lifespan of rotary instruments with a reduced risk of instrument fracture. 50

51. While novel mechanical methods of glide path preparation serve to increase the efficiency of this essential pre-requisite of canal shaping, the role of hand instruments should not be overlooked. 51

52. References Anil Dhingra and Neetika . Glide path in endodontics. Endodontology 2014; 26(1):217-222. PJ van der Vyver , M Vorster, F Paleker and FA de Wet. Glide path preparation in Endodontics: case report and a literature review of available materials and techniques. SADJ 2019; 74(3):129-136. I Cassim and PJ van der Vyver . The importance of glide path preparation in endodontics: a consideration of instruments and literature. SADJ 2013; 68(7):322-327. 52