Dr. Peet van der Vyver looks at enlarging the glide path with PathFile™ NiTi rotary instruments



Part one of this series discussed the rationale for the preparation of a glide path prior to the use of NiTi rotary instruments and illustrated the clinical technique when using a reciprocating handpiece (M4, Kerr) in combination with stainless-steel K-files to facilitate glide path preparation.

Recently, PathFile™ NiTi rotary instruments (Dentsply/Maillefer) were introduced to the market for glide-path enlargement. The system consists of three rotary instruments that can be used for glide-path enlargement after initial negotiation and establishment of a glide path with a No. 10 K-file (Berutti et al, 2009).


The lack of glide path establishment and glide path enlargement is often the cause of ledge formation, transportation, and blockage of root canals followed by obturation short of the apical constricture. Figure 1 shows a case where poor root canal treatments were performed on the lower right second premolar, and first and second molars. Figure 2 illustrates the same case after gutta percha removal and the location of the missed canals. Glide paths were established and enlarged with PathFiles™ in all the root canals, canal preparation was done with ProTaper® Universal (Dentsply/Maillefer), and the root canals were obturated with RealSeal™ (SybronEndo).

PathFile™ No. 1 (purple marking) has an ISO 13 tip size, PathFile™ No. 2 (white marking) has an ISO 16 tip size, and PathFile™ No. 3 (yellow marking) has an ISO 19 tip size. The taper of the nickel-titanium files is only 2%, which guarantees high flexibility and enables the files to follow complex anatomical root canal configurations during glide-path enlargement. According to the manufacturer, the files can be used at a speed of 300 rpm and a torque setting of between 3-5 N/cm.

PathFile™ clinical considerations and instrument sequence

•    Prepare an access cavity that will ensure straight-line access into all the root canals. Figure 3 depicts an access cavity that
was prepared on an upper first molar. Note the lack of straight-line access into the first mesiobuccal root canal (arrow). Figure
4 demonstrates a case where an access cavity was prepared on a lower first molar. It is evident that the preparation allows for
straight-line access into all the root canals

•    Remove any coronal interference, eliminating any obstruction or accentuated curvatures in the coronal third of the root
canal. Figure 5 shows a radiograph of a lower second molar where a coronal interference is clearly visible (arrow),
obstructing the entrance of the mesial root canal. This triangle of dentin was removed with an ultrasonic tip
(Start-X™ No. 2, Dentsply/Maillefer) (Figure 6) before the canal could be located. Figure 7 illustrates the final result after
the canals were prepared with ProTaper® Universal rotary files, irrigated with the SAF system (Redent Nova) using sodium hypochlorite and EDTA, and obturated with System B™ (SybronEndo)/Obtura® II (Obtura Spartan)

•    Negotiate the root canal up to working length (WL) (established with apex locator or radiograph), and establish patency with a
pre-curved stainless-steel K-file (size 06, 08 or 10) (Figure 8)

•    Establish an initial glide path with the K-files by using “watch-wind” or “in-and-out” movements by hand or by attaching a
reciprocating handpiece (M4, Kerr) (Figure 9), or NSK Tep-E10R (NSK) to the files and using the technique described in part one of this series (Van der Vyver, 2011)

•    Do not proceed with the PathFiles™ before an initial glide path has been established up to a size 10 K-file. To verify this, a size 10 K-file must be placed at WL, withdrawn 1.5 mm by hand from the root canal, and pushed back to WL without any difficulty. The above procedure is then repeated, but the file is respectively withdrawn up to 3 mm and 5 mm from the root canal. When the file can travel 5 mm from WL up to the established WL in the root canal, a successful glide path has been established

•    PathFile™ No. 1 (0.13 mm) (Figure 10) is introduced, into the root canal at a rotation speed of 300 rpm in a delicate in-and-
out movement until WL is reached (3-5 seconds). The instrument is then removed from the canal. It is important to
note that the PathFiles™ must not be kept rotating in a stationary position in the root canal, especially in severely
curved root canals, due to the increase in metal fatigue on the instrument

•    Irrigation after each PathFile™ is recommended to remove dislodged debris from the root canal. In canals that demonstrate accentuated curves in the apical third of the root canal system, it is also recommended by the author to recapitulate with the
size 10 K-file by hand to ensure complete patency of the root canal

•    PathFile™ No. 2 (0.16 mm) (Figure 11) is then introduced followed by PathFile™ No. 3 (0.19 mm) (Figure 12) following
the same protocol as described above

•    Start preparing the root canal with NiTi rotary instruments of choice



Clinical case reports

Case report one
Figure 13A illustrates a case where a 30-year-old woman presented with a periapical area around her nonvital, upper right central incisor. After access cavity preparation, length determination, and patency was established using an electronic apex locator (Raypex® 5, VDW) and a size 15 K-file (Figure 13B).

A glide path was established using PathFiles™ No. 2 (0.16 mm) and No. 3 (0.19 mm), and root canal preparation was done with a size 025.08 single-use WaveOne™ Primary reciprocating file (Dentsply/Maillefer) (Figure 13C) driven by a WaveOne™ electric motor (Dentsply/Maillefer) (Figure 13D) and 6:1 reducing handpiece (Sirona). The WaveOne™ Primary file was used with a progressive up-and-down motion, engaging the dentin with light force three to four times before the file was removed from the root canal. The flutes of the file were cleaned, and the root canal was irrigated with 3.5% sodium hypochlorite. Recapitulation was achieved with a size 0.10 K-file to length. This process was repeated until WL was reached with the reciprocating file. Smear layer removal was achieved with a rinse of 17% EDTA for 1 minute.

A master cone, WaveOne™ Gutta Percha Point Primary (Dentsply/Maillefer) was fitted (Figure 13E) and the cone-fit confirmed with a radiograph (Figure 13F). The root canal was obturated (Figure 13G) using AH Plus® root canal cement (Dentsply/Maillefer) and System B™ (SybronEndo) and Obtura® II (Obtura Spartan).

Case report two
A 30-year-old man presented with irreversible pulpitis on his lower left first molar. Radiographic examination revealed a large carious lesion on the occlusal surface of the tooth (Figure 14A). Note the close proximity of the apices of the roots to the inferior alveolar nerve canal. After removal of the caries and access cavity preparation, root canal patency and length determination was established (Figure 14B). A glide path was established by first using a size 10 K-file in a reciprocating handpiece followed by PathFiles™. Root canal preparation was done using ProTaper® Universal rotary instruments, and obturation was done with AH Plus® root canal cement in conjuction with F2 ProTaper® Obturators (Dentsply/Maillefer) (Figure 14C) in the mesial canals. The distal canal was obturated with an F3 ProTaper® Universal Gutta Percha Point using System B™ and Obtura® II. Note how the original canal anatomy was maintained without ledge formation or transportation of the root canals (Figures 14A, B and D courtesy of Dr. C. van der Merwe).

Case report three
Figure 15A demonstrates a case of a 50-year-old man presenting with pain and discomfort on his upper left second molar, which was one of the abutments of a four-unit bridge. A length- determination radiograph (Figure 15B) revealed a curvature in the middle third of the mesiobuccal root canal, a small curvature in the apical 2 mm of the palatal root canal, and a sharp curvature towards the distal aspect of the distobuccal root canal.

Glide-path preparation was done with a size 10 K-file in a reciprocating handpiece followed by 0.13, 0.16, and 0.19 mm PathFiles™ respectively. Root canal preparation was done with ProTaper® Universal rotary instruments, and obturation was completed with AH Plus® root canal cement and System B™ and Obtura® II. Clearly visible on the gutta percha cone-fit (Figure 15C) and postoperative radiograph (Figure 15D) is that the different curvatures in the three root canals were maintained during canal preparation (Figures 15A-D courtesy of Dr. C. van der Merwe).

Case report four
The patient, a 60-year-old woman, presented with discomfort when chewing on her lower left second molar. A preoperative radiograph (Figure 16A) revealed a previous root canal treatment. Mesiobuccal and mesiolingual canals were poorly instrumented and obturated approximately 5-7 mm short of the radiographic apices. The distal root canal was obturated short of the radiographic apex, leaving approximately 10-12 mm of visible root canal space untreated.

Figure 16B illustrates the initial negotiation of the root canals with hand files after removal of the obturation materials from the root canals with ProTaper® Universal Retreatment Files (D1, D2, and D3) (Dentsply/Maillefer) (Figure 16C), Hedstrom files, and Endosolv E (Septodont). Clearly visible on this radiograph is that the mesial canals appear sclerosed in the apical parts, and that full WL was achieved in the distal root canal. C+ Files (Dentsply/Maillefer), size 08 and 10 (Figure 16C), in conjunction with size 08 K-files, were used to negotiate the mesial root canals until the apex locator reported that apical patency was achieved in the mesial root canals.

Glide-path preparation was accomplished by first using a size 10 K-file in a reciprocating handpiece up to the predetermined WLs, ensuring initial glide paths up to a size 10 (Figure 16E). PathFile™ No. 1 (0.13 mm) (Figure 16F) was introduced into the root canals with a delicate in-and-out movement until WL was reached, ensuring not to keep the file rotating in a stationary position in the curved part of any of the root canals. All the canals were irrigated with sodium hypochlorite, and a patency file (pre-curved 08 K-file) was taken up to the WL in each root canal to ensure the absence of any debris in the root canals and to reconfirm WL.
PathFile™ No. 2 (0.16 mm) (Figure 16G) was then introduced followed by PathFile™ No. 3 (0.19 mm) (Figure 16H), following the same protocol as described above. Figure 16I depicts a radiograph with PathFiles™ placed into the root canals up to the predetermined WL. It is evident that all the canal curvatures were maintained during glide-path preparation.



Root canal preparation was done with ProTaper® Universal rotary instruments and irrigation by alternating 3.5% sodium hypochlorite and 17% EDTA. ProTaper® F2 Universal Gutta Percha Points were fitted into the prepared mesial root canals, and an F3 ProTaper® Universal Gutta Percha Point was fitted into the prepared distal root canal (Figure 16J). The root canals were obturated with Calamus® Dual 3-D Obturation System (Figure 16K). Figure 16L demonstrates the postoperative result. Note the excellent maintenance of the root canal anatomy. Visible on the radiograph is an apical lateral canal in the distal root canal as well as a midroot lateral canal branching off from the mesiolingual root canal system that was obturated with the warm vertical condensation technique.



Conclusions

Several studies advocate glide-path preparation to a minimum of 0.20 mm before the use of rotary nickel-titanium instruments (Berutti et al, 2004; Varela Patino et al, 2005). After the establishment of an initial glide path with a size 10 K-file (by hand or in a reciprocating handpiece) followed by the use of PathFiles™ for glide path enlargement, this objective is achieved. The clinician will have the following advantages when using this technique:

•    The mechanical enlargement of the glide path with rotary instruments, instead of creating it with stainless-steel files by
hand, results in less hand fatigue and saves the clinician valuable chair time

•    The high flexibility of the 2% tapered instruments enables the clinician to follow the original canal anatomy and to maintain
it during glide path enlargement without ledge formation or transportation of the root canal

•    Removes pulp tissue and debris from canals, allowing the operator to maintain WL and patency in the root canals

•    An increased flow of irrigation solutions into the middle and apical thirds of root canals (Greco, Cantatore, 2008)

•    A glide path established to a size 0.19 mm (PathFile™ No. 3) ensures a reduction in torsional stress, thereby increasing
the lifespan of the rotary instrument that will be used for canal preparation. According to Berutti et al (2004), the canal
diameter should be at least one size larger than the tip of the first rotary instrument. A size 0.20 mm glide path guarantees
this protocol if the clinician uses the S1 file of the ProTaper™ Universal system, which has a tip of 0.18 mm

•    Routine glide path establishment and enlargement with PathFiles™ can increase the lifespan of rotary instruments with a reduced risk of instrument fracture

•    Provides the clinician with more confidence to prepare more complex and challenging endodontic cases

Bio

Professor Peet van der Vyver lectures extensively on different topics in endodontics and esthetic dentistry. He is in private practice in Sandton, South Africa, and is a part-time lecturer at the School of Dentistry, University of Pretoria, South Africa.


References

Berutti EL, Cantatore G, Castellucci A, et al (2009) Use of nickel titanium rotary PathFile to create the glide path: comparison with manual preflaring in simulated root canals. J Endod 35(3):408-412.

Berutti EL, Negro AR, Lendini M, et al (2004) Influence of manual preflaring and torque on failure rate of ProTaper rotary instruments. J Endod 30(4):228-230.

Greco K, Cantatore G (2008) Evoluzione delle tecniche di irrigazione canalare. 29 Congresso Nazionale S.I.E Torino, Italy: 13-15 Nov.

Van der Vyver PJ (2011) Creating a glide path for rotary NiTi instruments: part one. Endodontic Practice US 4(4):32-34.

Varela Patino P, Biedma B, Rodriquez CL, et al (2005) The influence of manual glide path on the separation rate of NiTi rotary instruments. J Endod 31(2):114-116.