Pr. Ghassan Yared, DDS, MSc, (F)RCDC (email@example.com)
Reciproc® blue (VDW GmbH, Munich, Germany), a thermally treated nickel-titanium instrument, is an improved version of the original Reciproc® 4. It has an increased resistance to cyclic fatigue and a greater flexibility 5.
The present article describes the use of Reciproc® blue instruments for the canal preparation without any prior instrumentation and without a glide path. Only one instrument is needed to enlarge the majority of the canals to an adequate size and taper regardless of the size of the canal, the degree of canal curvature or canal calcification.
The Reciproc® blue system includes 3 instruments, similar to the original Reciproc® series, the Reciproc® blue 25, Reciproc® blue 40 and Reciproc® blue 50, matching paper points, matching gutta-percha cones, and matching gutta-percha obturators (GuttaFusion®) (Fig. 1a-d).
The Reciproc® blue instruments have an S-shaped cross-section (Fig. 2). The three instruments have a regressive taper starting at 3 mm from the tip. The Reciproc® blue 25 has a diameter of 0.25 mm at the tip and an 8% (0.08 mm/mm) taper over the first 3 mm from the tip.
The Reciproc® blue 40 has a diameter of 0.40 mm at the tip and a 6% (0.06 mm/mm) taper over the first 3 mm from the tip. The Reciproc® blue 50 has a diameter of 0.50 mm at the tip and a 5% (0.05 mm/mm) taper over the first 3 mm from the tip.
The instruments are used in conjunction with a motor (Fig. 3a, b) at 10 cycles of reciprocation per second. The motor is programmed with the angles of reciprocation and speed for the three instruments. The values of the forward and reverse rotations are different.
When the instrument rotates in the cutting direction (forward rotation) it will advance in the canal and engage dentine to cut it. When it rotates in the opposite direction, the reverse rotation (smaller than the forward rotation) the instrument will be immediately disengaged.
The end result, related to the forward and reverse rotations, is an advancement of the instrument in the canal. The angles set on the reciprocating motor are specific to the Reciproc blue instruments. They were determined using the torsional properties of the instruments.
Recently, a reciprocating contra-angle has been introduced (Fig. 3c) 6. It has been shown to be as safe as the reciprocating endodontic motor 7. In addition, it offers a significant cost advantage. The contra-angle can be attached to either the air-driven or electrical micromotor of the dental unit.
The technique is simple. In the majority of the canals, only one Reciproc® blue instrument is used in reciprocation to complete the canal preparation without the need for initial canal negotiation with small hand files or creating a glide path.
The requirements for the access cavity and the straight-line access to the canals, and the irrigation protocols remain unchanged.
The use of drills or orifice openers is not required prior to starting the canal preparation with the Reciproc® blue instrument.
The selection of the appropriate Reciproc® blue instrument is based on an adequate radiograph (Fig. 4). If the canal is partially or completely invisible on the radiograph, the canal is considered narrow and the Reciproc® blue 25 is selected (Fig. 5a, b).
In the other cases, where the radiograph shows the canal clearly from the access cavity to the apex, the canal is considered as relatively large (Fig. 6a-c).
A size 30 hand instrument is inserted passively to the working length (verified with an apex locator) with a gentle watch winding movement but without a filing action.
If the file reaches the working length, the canal is considered large; the Reciproc® blue 50 is selected for the canal preparation. If the size 30 hand file does not reach the working length passively, a size 20 hand file is inserted passively in the canal.
If it reaches the working length, then the canal is considered medium in size and an Reciproc® blue 40 instrument is used for the canal preparation. If the hand file 20 does not reach the working length passively, the Reciproc® blue 25 is selected.
Before commencing preparation, the length of the root canal is estimated with the help of an adequately exposed and angulated pre-operative radiograph. The silicone stopper on the instrument is set at two thirds of that length. Reciproc® blue is introduced in the canal with a slow in-and-out pecking motion without pulling the instrument completely out of the canal.
The amplitude of the in- and out- movements (pecks) should not exceed 3-4 mm. With this flexible instrument, only very light pressure should be applied. The instrument will advance easily in the canal in an apical direction and should not be forced forward.
After 3 pecks, or if resistance is encountered before the 3 pecks are completed, the instrument is pulled out of the canal to clean the flutes. A #10 hand file is used to check patency to two thirds of the estimated length. The canal is copiously irrigated. The Reciproc® blue instrument is then re-used in the same manner until it reaches the two thirds of the estimated length.
The canal is irrigated and a #10 file is used to determine the working length with the aid of an apex locator and a radiograph.
After that Reciproc® blue is used as described until it reaches the working length. As soon as the working length is reached, the instrument is withdrawn from the canal to avoid an unnecessary over-enlargement. The Reciproc® blue instrument can also be used with a brushing motion against the walls of wide canals.
With continuous rotation it is necessary to create a glide path in order to minimize instrument binding and the risk of fracture (8, 9). Glide path is usually created with engine-driven instruments which presented a fracture rate as high as 26% 10, 11 (Fig. 7).
Binding is less likely to occur when an instrument is used in reciprocation with unequal forward and reverse angles and with the limited in- and out- movements as described earlier 12.
Therefore, a glide path is not required in the majority of the canals when instruments are used in this manner.
It has been shown the incidence of fracture of Reciproc blue® instruments used without a glide path is very low 13,14 in comparison to rotary instruments 15.
However, just as with any continuous rotary system, it is possible to use the Reciproc® blue instruments after creating a glide path with a new reciprocating instrument, the R-Pilot® (VDW GmbH, Munich, Germany) (Fig. 8) specifically designed for this purpose. The instrument is used with the same reciprocating motor/contra-angle and at the same settings.
The reciprocating glide path R-Pilot® performed better than rotary glide path instruments in regard to cyclic fatigue resistance 16 and centring ability 17.
A glide path should be created with the R-Pilot® prior to using the Reciproc® blue in some canals, or for example when the Reciproc® blue instrument stops advancing in the canal or if advancement becomes difficult.
In these canals, apical pressure should not be exerted on the Reciproc® blue file.
The instrument should be removed from the canal and the canal should be irrigated. Patency is established to the working length with a #8 file and the R-Pilot® instrument is used to create a glide path to the working length.
The Reciproc® blue instrument can then be used safely to the working length. The R-Pilot® instrument is used with the same reciprocating motor and settings, with a light and short pecking motion similar to the use of Reciproc® blue.
A glide path can also be created with the R-Pilot to reduce the stresses on the Reciproc® blue instruments for example in canals with difficult access or canals presenting with a curvature in their coronal third (Fig. 9a, b).
If an increased apical enlargement is required, a larger Reciproc® blue instrument, or a nickel-titanium hand or rotary instrument can be used.
The access to the orifices of some canals such as the mesio-buccal orifice of a mandibular second molar may be difficult. Due to the thermal treatment of the Reciproc® blue files, it is safe to gently pre-curve their tip in order to make the access to these orifices easier.
In summary, the use of instruments in reciprocation with unequal forward and reverse rotations and with a limited pecking motion has been shown to be very safe with a fracture rate ranging from 0 to 0.2% 13, 14, 18 compared to continuous rotation with a fracture rate ranging from 0.7 to 20% 15.
The majority of the canals can be shaped with only one Reciproc blue instrument without any prior instrumentation and without a glide path 13, 14, 18.
In contrast to canal preparation with rotary instruments, initial canal negotiation with small hand files sizes 06-15, a challenging step in narrow canals associated with a high incidence of procedural errors 19, 20 (Fig. 10 a-c), is not required in most canals prior to the use of Reciproc blue instruments.
These instruments have an increased flexibility and fatigue resistance, and are very safe for the preparation of severely curved canals 21, 22 (Fig. 11 a-c, 12 a-c)
1. Canal preparation using only one Ni-Ti rotary instrument: preliminary observations. Yared G. Int Endod J 2008 Apr;41(4):339-44.
3. The ability of the Reciproc R25 instrument to reach the full root canal working length without a glide path. De-Deus G, Arruda TE, Souza EM, Neves A, Magalhães K, Thuanne E, Fidel RA. Int Endod J 2013 Oct;46(10):993-8.
5. Blue Thermomechanical Treatment Optimizes Fatigue Resistance and Flexibility of the Reciproc Files. De-Deus G, Silva EJ, Vieira VT, Belladonna FG, Elias CN, Plotino G, Grande NM. J Endod 2017 Mar;43(3):462-466.
7. The impact of using a pneumatic contra-angle device on the lifespan of M-Wire- and Blue-treated instruments. Silva EJNL, Vieira VTL, Gabina TTG, Antunes HDS, Lopes HP, De-Deus G. Clin Oral Investig. 2019 Feb;23(2):617-621
8. In vitro study of the torsional properties of new and used ProFile nickel titanium rotary files. Yared G. J Endod 2004 Jun;30(6):410-2.
9. In vitro assessment of torque and force generated by novel ProTaper Next Instruments during simulated canal preparation. Pereira ES, Singh R, Arias A, Peters OA. J Endod 2013 Dec;39(12):1615-9.
10. Scouting Ability of 4 Pathfinding Instruments in Moderately Curved Molar Canals. De-Deus G, Belladonna FG, Souza EM, et al. J Endod. 2016 Oct;42(10):1540-4.
11. Comparative evaluation of the effectiveness and fracture rate of three pathfinding nickel-titanium rotary instruments, Mtwo, OneG, and ProGlider, in mechanically negotiating moderately curved molar canals to the full working length. Neelam U Jaiswal, Shivkumar P Mantri, Bonny Paul, et al. J Cons Dent May-Jun 2019;22(3):260-265.
12. Elastic limits in torsion of reciprocating nickel-titanium instruments. Ha JH, Kim SR, Versluis A, Cheung GS, Kim JW, Kim HC. J Endod. 2015 May;41(5):715-9.
13. Performance of Reciproc Blue R25 Instruments in Shaping the Canal Space without Glide Path. De-Deus G, Cardoso ML, Belladonna FG, Cavalcante DM, Simões-Carvalho M, Souza EM, Lopes RT, Silva EJNL. J Endod. 2019 Feb;45(2):194-198
14. Mechanical properties and metallurgical features of new and ex vivo used Reciproc Blue and Reciproc. Generali L, Puddu P, Borghi A, Brancolini S, Lusvarghi L, Bolelli G, Consolo U, Pedullà E. Int Endod J. 2020 Feb;53(2):250-264.
15. Fracture of nickel titanium rotary instrument during root canal treatment and re-treatment: a 5-year retrospective study. Alfouzan K, Jamleh A. Int Endod J. 2018 Feb;51(2):157-163.
16. Cyclic fatigue resistance of R-Pilot, WaveOne Gold Glider, and ProGlider glide path instruments. Keskin C, İnan U, Demiral M, Keleş A. Clin Oral Investig. 2018 Dec;22(9):3007-3012.
17. Microcomputed Assessment of Transportation, Centering Ratio, Canal Area, and Volume Increase after Single-file Rotary and Reciprocating Glide Path Instrumentation in Curved Root Canals: A Laboratory Study. Aydın ZU, Keskin NB, Özyürek T, Geneci F, Ocak M, Çelik HH. J Endod. 2019 Jun;45(6):791-796.
18. Comparison of the ability of Reciproc and Reciproc Blue instruments to reach the full working length with or without glide path preparation. Adıguzel M, Tufenkci P. Restor Dent Endod. 2018 Nov 1;43(4):e41
19. Ledge formation: review of a great challenge in endodontics. Jafarzadeh H, Abbott PV. J Endod. 2007 Oct;33(10):1155-62.
20. Instrument fracture in root canals – where, why, when and what? A study from a student clinic. Ungerechts C, Bårdsen A, Fristad I. Int Endod J. 2014 Feb;47(2):183-90.
21. Shaping ability of reciprocating single-file systems in severely curved canals: WaveOne and Reciproc versus WaveOne Gold and Reciproc blue. Bürklein S, Flüch S, Schäfer E. Odontology. 2019 Jan;107(1):96-102.
22. Changes in Geometry and Transportation of Root Canals with Severe Curvature Prepared by Different Heat-treated Nickel-titanium Instruments: A Micro-computed Tomographic Study. Filizola de Oliveira DJ, Leoni GB, da Silva Goulart R, Sousa-Neto MD, Silva Sousa YTC, Silva RG. J Endod. 2019 Jun;45(6):768-773.