Root Canal Shaping by Continuous or Reciprocating Rotation: the ProTaper System versus the Endo-Eze Tilos System
The aim of this in vitro study is to compare between two systems of canal shaping: the ProTaper® system (used in continuous rotation) and the Tilos® (used in reciprocating motion), in order to evaluate, after endodontic preparation, the increase in canal surface, the canal centring and the respect of the initial canal shape.
Materials and method
Thirty human teeth (first and second mandibular molars) with straight or slightly curved mature roots were sectioned 3mm below the neck, the access cavities established and the working length of the mesial roots measured. Each tooth was slipped into a transparent block of resin. Each block was perforated, one on the mesial and one on the distal part of the tooth; with a drill and then sectioned within 4mm of the tooth apex. A picture of each section was taken before canal preparation with a digital camera mounted on a stereo microscope. The teeth were distributed into two groups: group 1 was prepared with the ProTaper® and group 2 with the Tilos® . A second picture of the sections was taken after preparation. The images obtained were processed with the CS5 Photoshop program in order to color the preoperative and the postoperative canal surfaces. The superimposition of both images of the same root was achieved by the RealDraw Pro program. Thanks to the PhotoShop CS5, it was possible to measure the canal surfaces in pixels. The statistical analysis of the data on the progression of the canal surface for both groups was based on the unilateral test. The statistical analysis of the data on the canal centering and the modification of the canal shape was carried out with the chi-square (x2).
The unilateral test showed a p = 0.039 so that the difference between both systems is statistically significant. The chi-square test didn’t show any significant difference between both groups: P=0.5775 for the canal centring and P=0.4202 for the canal shape modification.
The ProTaper system is more efficient than the Tilos system in extending the canal surface. Both preparation systems are quite the same concerning the respect of the centring and the initial shape of the canal.
Reciprocating motion, continuous rotation, root canal shaping, root canal centring, canal surface increase.
Canal shaping should enable irrigating solutions to clean thoroughly the entire canal system. This is to eradicate bacteria and toxins and all the pulp debris likely to serve as nutriments for bacteria proliferation. It will also make it possible a three-dimensional obturation of the canal system and its airtight sealing.12, 15 The manufacturers continuously seek to facilitate the job of dentists with more reliable instruments and by making faster canal preparation possible. Canal preparation thus becomes easier, quicker and more accurate, with less debris thrown onto the periapex. The objectives to achieve also depend on the practitioner’s dexterity when using these instruments.
For fifteen years, the rotary nickel-titanium (NiTi) instruments have facilitated endodontic practice as it allows faster shaping, better canal centring and less risk of ledging and tearing the apical foramen. The instrumental fracture remains the main problem when using these instruments.4
The concept of reciprocating motion makes it possible to reduce the risk of fracture with endodontic instruments. This concept uses a clockwise – anticlockwise movement with unequal amplitude similar to the movement of the balanced forces described in the 1980s. 4,7
Mastering canal preparation and preventing incidents require from the practitioner to have an accurate knowledge of the impact of the instruments characteristics on the mechanical behaviour of the instrument.
Nowadays, many systems are available on the market to achieve the best possible biological and mechanical objectives of canal treatment: a regular conical shape, the respect of the canal trajectory as well as keeping a narrow foramen in its initial position.
The many systems available make it complicated for the practitioner to choose the best one.
The aim of this in vitro study is to compare between two systems of canal shaping: the ProTaper® system (DENTSPLY Maillefer); used in continuous rotation; and the Tilos® (Ultra dent); used in reciprocating motion; in order to evaluate:
– The increase in the canal surface
– The canal centring
– The respect of the initial canal shape.
Materials and method
1- Teeth selection
Thirty human, caries-free teeth (first and second mandibular molars) were used in this study. These teeth were stored in tap water and in a refrigerator until operating processes.
All these teeth presented an apex without any fracture and mature roots – either straight or slightly curved ones. In this study, only mesial roots were used.
2- Teeth preparation
– The teeth were cleaned using a brush and pumice stone powder mixed with water to eliminate dental plaque.
– The vestibular faces were marked by letter “V” and the lingual faces by an identification number.
– The occlusal face of each tooth was sectioned 3mm below the neck with a 0.5mm thick metallic disk.
– The access cavities were established by Endo Z and tungsten carbide bur drills mounted on a multiplying contra angle.
– The teeth were divided haphazardly into two groups. Group Nr1, from nr1 to nr15, intended for the Tilos system and group Nr2, from nr16 to nr30, intended for the ProTaper system.
– The working lengths of the mesial canals (16mm > WL < 18mm) were measured by means of a nr 0.8 K file. The value to be kept was the value measured as soon as the file tip was visible at the apex and the stop brought to the reference occlusal surface.
– On each root, a line was drawn 4mm from the apex. This line marks the future cutting line performed by the Isomet.
3- Making of a resin block
A silicon mould was made up to achieve a transparent resin block coating the roots of the selected teeth. Each tooth inserted into the block will be sectioned horizontally 4mm from its apex. Such a device will allow an exact and accurate repositioning of both block sections when taking shape.
This cube was created according to the following steps:
– A cubic shape mould is made from modelling clay in order for the tooth roots to be completely coated by resin. The location of the two tightening screws has been planned Nr. 3, 5.
– The block faces are parallel.
– On one of the block faces, a vertical indention was performed to show the location of the teeth vestibular face.
– The block obtained with modelling clay was placed into silicon. Its impression was used as a mould for the transparent resin block. A silicon mould was thus obtained.
Each tooth was slipped into a transparent resin. The vestibular face was placed opposite the indention. After the resin was set, two holes (one on the right and one on the left side of the tooth) were made with a drill equipped with an Nr4 drill bit. These holes serve to fix tightening screws Nr3.5 (Fig.1).
Each block was mounted on an Isomet BUEHLER saw and sectioned at the level of the marked line. The section was carried out with a 0.4mm thick, diamond-tipped disk (ref. 11-4244) with a 7 RPM speed. Two fragments were thus obtained, one apical and one coronary, the sample number reported on them. The apical fragment was the only one to be analyzed.
5- Stereo microscope observation and photos
Each section was photographed with a digital camera mounted on a Zeiss Stemi 2000-c stereo microscope with a 2.5 enlargement.
6- Canal root preparation
The two fragments of each tooth are repositioned and fixed with nr 3.5 screws and nuts. Group 1 was prepared with the Protaper® and group 2 with the Endo-Eze Tilos® .
a- Protaper® protocol
This system is used in continuous rotation with a constant speed between 150 and 350 RPM. Root canal preparation was performed according to the following protocol:
• Coronal thirds preparation: initial negotiation of the canal using nr10 and nr15 K hand file until work length (WL). Use of the S1 and S2 mechanical shaping files to reach progressively WL.
• Apical third preparation: using L1 and L2 mechanized finishers’ files until WL.
After each instrument change, canals were abundantly irrigated with a 2.5% NAOCI solution.
b- Endo-Eze Tilos® protocol
The Endo- Eze Tilos® system (Ultradent) is a hybrid system which combines two techniques: manual and mechanical. It is used with a reciprocal contra angle with a 30° right and left brushing movement.
Canal preparation was carried out according to the following protocol:
• Coronal thirds preparation: initial step with nr15 hand file followed by S1 (mechanized shaping file) until WL -3mm. Recapitulation with nr15 hand file followed by S2 shaping files until WL -3mm. Recapitulation with nr15 hand file followed by S3 until WL -6mm.
Recapitulation with WL nr20 hand file followed by S2 until WL.
• Apical third preparation: nr 25 Tilos® Transitional files with a 6% and 4% conic shape were used. 6% transitional files were used until WL
• After each change of instrument, all canals were irrigated abundantly with a solution of NaOCI at 2.5%.
7- Stereo microscope second observation and photographs
Each section was photographed with a digital camera mounted on a Zeiss Stemi 2000-c stereo microscope with a 2.5 enlargement.
The photos were made considering:
• The widening at the start
• The same arrangements as before the preparation
8- Image processing
The images obtained were processed with the CS5 Photoshop program in order to color the preoperative canal walls in mauve and the postoperative canal surfaces in blue. Then, with the Real Draw PRO program, both photos of the same root were superimposed. This combination was then reprocessed with the Photoshop CS5 program in order to measure the canal surface which is given in pixels.
Material Free of Monomer
1- Image analysis
The superimposition of the images, before and after preparation (Figs 2 and 3) made it possible to achieve different observations of nr2 Table.
2- Descriptive study
a- Quantitative study (Table nr1)
The mean values obtained, for canal surface increase, with the Tilos system were 195.419% and 231.443% with the Protaper system.
b- Qualitative study (Table nr2)
• Canal centring:
– The Tilos system: 68% of the canals showed a centred widening without the canal walls being damaged, 23% showed a centred widening with canal walls damaged and 9% a non-centred widening without any damage.
– The Protaper system: 90% of the canals presented a centred widening without the canal walls being damaged, 5% showed a centred widening with the canal walls being damaged and 5% a non-centred widening without the canal walls being damaged.
• Canal shape modification:
– The Tilos system: 18% of the canals kept their initial shape while 82% did not.
– The Protaper system: 29% of the canals kept their initial shape while 71% did not.
3- Statistical study
• The statistical study of the canal surface increase data of both groups was based on the unilateral test.
This test showed p=0.039, so the difference between the two systems is statistically significant. The Protaper system is more efficient than the Tilos system concerning canal surface widening.
• The statistical analysis of canal centring and canal shape modification data was done with chi-square. This test did not reveal any significant difference between the two groups:
P=0.5775 for canal centring
P=0.4202 for canal shape modification
It can be deduced that the two preparation systems are equivalent concerning the respect of canal shape.
This in vitro study compares the shaping efficiency of two endodontic instruments on the mesial canals of inferior molars.
There are numerous evaluation methods: radiography (classical, digital, cone beam), scanning electronic microscopy, computed tomography, tomodensiometry, etc…
The modified Bramante technique is among the oldest and cheapest techniques. It is a method which makes it possible to compare the canals before and after instrumentation. It makes it possible to evaluate instrument efficiency by analyzing several parameters: canal shape modification, canal centring and canal transportation.2
The major drawback of the plaster spanner being a bad adaptation between the various fragments, the endodontic block (metallic device) was chosen to overcome this difficulty.8
The teeth were put into transparent resin, into a silicon mould (instead of the endodontic block) and the fragments fixed with two screws and their nuts (before sectioning by the drill). This technique proved easier than the endodontic block and just as efficient (no loosening between the fragments and a good adaptation).
Very few studies have dealt with the Tilos® system. For this reason we are going to discuss the various parameters, with the most studied systems using the reciprocal movement, i.e. WaveOne® and Reciproc® .
Our study showed that the Protaper® makes it possible a canal widening 4mm from the apex, which is more important than the Tilos® . This can be explained by the instruments shape, in particular their conical shape. The Protaper® consists of sharp files with triangular section and varying conical shapes (increasing for shaping files, decreasing for finishing files). With this system, the larger conical shape is 9% and the apical finishing shape is 8% with a diameter at the tip of 25/100(for F2). The maximum conical shape of the Tilos system is 6% and its apical diameter 25/100 for the transitional files.
In a similar study to ours, Rosa and all11 tried to compare the Protaper® with the Tilos® . A group of 15 molars (first and second molars) were used with each system. It was shown that the rotating system provided the greatest increase in canal surface at the level of the cervical area of the canal. This difference is statistically significant but there is not any significant difference at the level of the medium third, nor at the level of the apical third in spite of the fact that the rotating system also provided a greater widening at both levels.
In the You and al 15study, comparing the Protaper® with Reciproc® system, (carried out on maxillar molars mesial and distal curved canals) it was not shown, after an evaluation by tomodensiometry, any significant difference between both systems concerning canal surface increase.
The Versiani study 13 carried out on 54 mandibular canines with a similar morphology and comparing Protaper® , WaveOne® and Reciproc® , showed that the rotating system makes it possible a more significant canal surface than the systems with reciprocating motion.
The Capar study 4, carried out on lower molars mesial canals, showed that with the Protaper and WaveOne® systems, there is a similar canal surface increase, but less than the Reciproc system with which more dentin is removed in that study and the difference is not significant.
In the study carried out on resin blocks with FlexMaster instruments, Franco found out a more important canal surface increase with continuous rotation than with reciprocating motion at the apical third. There is no significant increase between the two protocols concerning the two median and coronal thirds.
The Robinson study10, who worked on mesial roots of mandibular molars and evaluated the teeth by tomodensitometry, showed by comparison that the Protaper® leaves less debris in the canal than WaveOne® and this difference was statistically significant.
Zokkar17, in another study comparing the Revo-S® system (continuous rotation) with the Endo-Express system (reciprocating motion) following a standard radiography analysis, showed that the Endo-Express system gives a more important widening at the level of the lower molars, but there is not any statistically significant difference.
In our study, there wasn’t any significant difference between the two systems used concerning canal shape variation.
The literature review shows diverging results. This might be explained by differences in methodology, operating protocol, instrumentation used…
The Hartmann study 7 carried out on mesial canals of maxillar molars showed that the manual endodontic instruments, those used in continuous rotation and those used in reciprocating motion, canal transportation. This canal transportation is more important with mechanical systems than with manual instruments.
The Lopez study 9, carried out on the mesial root of upper molars, showed a significant difference between the K3® system and the reciprocating NSK® handpiece. K3® allows a better canal centering than the reciprocating movement.
The Berutti study 1, carried out on resin blocks, showed that with the WaveOne® system, the initial canal anatomy is better respected than with the ProTaper® system.
The Capar study 4 on curved mesial roots of lower molars and comparing 6 systems (OneShape® , ProTaper® Universal, ProTaper® next X2, Reciproc® , Twisted File Adaptive and WaveOne®) did not show any significant difference concerning canal transportation.
The Gergi study 6, devoted to centering and canal transportation (for the ProTaper® , Twisted and Hand-k files) on curved canals, showed a significant difference between the three systems. The Twisted File system generates less transportation, followed by the ProTaper® system. In this study it was observed that, for centering, there was a significant difference between these systems at the level of median and apical parts but not the cervical part.
The Twisted Files system allows a more centered canal preparation.
The Yang and all study 14, comparing two rotating systems, namely Mtwo® and Protaper® , carried out on 20 canals evaluated by tomodensitometry, showed that there is a difference in canal transportation, between both systems, at the apical level but not the cervical and medium levels and also that it generates more canal transportation.
Concerning the possibility of roots becoming more fragile, comparing the Protaper® and Mtwo® systems with the Reciproc® and WaveOne® systems, the Bürklein 3 and all study showed that dentin defects are not linked with the type of instrument used (reciprocating or rotating system). The systems with reciprocating motion generate, on the apical part, a lot more cracks compared with rotating instruments.
In our in vitro study, two endo-mechanized systems were compared, the Protaper (continuous rotation) and the Tilos (reciprocating motion), carried on the mesial root of mandibular molars sectioned 4mm from the apex. The superimposition of preoperative and postoperative images led to the following conclusions:
• The Protaper® system allows a more important canal widening than the Tilos® system.
• The two preparation systems used are equivalent concerning the respect of the initial canal shape.
These results are in keeping with some studies5,11,15 where it was noticed that rotating systems allow a more significant widening than systems with reciprocating motion whereas in other studies 4,15,16,17, it was shown that both systems allow a similar canal widening. Dealing with centring capacity and canal transportation.
some studies 1,4,3,6 showed that the various systems studied allowed a relatively good centring and a minor canal transportation even if there are differences from one system to the other. It all depends on the operating protocol, instrumentation used as well as the practitioner’s skills.
Each system has its advantages and drawbacks, but it could be suggested that the reciprocating motion, by eliminating the screwing effect, reduces the tip tightening risks, and delays plastic deformation moving to instrumentation fracture.
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3. Bürklein S, Tsotsis P, Schüafer E. Incidence of dentinal defects after root canal preparation: reciprocating versus rotary instrumentation. J Endod 2013;39:501-4.
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10. Robinson J, Lumley P, Cooper P and all. Reciprocatingroot canal technique inducesreaterdebris accumulation than a continuous rotary technique as assessed by 3-dimensional micro-computedtomography. J Endod 2013;39:1067-70.
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12. Schilder H. Cleaning and shaping the root canal. Dent Clin North Am 1974;18:269 –96.
13. Versiani MA, Leon GB, Steier L and all . Micro-computed tomography study of oval-shaped canals prepared with the self-adjusting file, Reciproc, WaveOne, and ProTaper universal systems. J Endod 2013; 39:1061-6.
14. Yang G, Yuan G, Yun X, Zhou X, Liu B, Wu H. Effects of two nickel-titanium instrument systems, Mtwo versus Protaper universal, on root canal geometry assessed by micro-computed tomography. J Endod 2011;37:1412-6.
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by Dr. Chems Belkhir, Dr. Rim Naifar, Dr. Jihed Ben Ammar, Dr. Sana Bagga, Dr. Mohammed Semir Belkhir