Wael Batbout – Post graduate student, Department of Restorative Dentistry-Endodontics, Faculty of Dental Medicine, Monastir, Tunisia
Emna Hidoussi – Assistant Professor, Department of Restorative Dentistry-Endodontics, Faculty of Dental Medicine, Monastir, Tunisia
Neila Zokkar Professor – Assistant Professor, Department of Restorative Dentistry-Endodontics, Faculty of Dental Medicine, Monastir, Tunisia
Abstract
Aim: This work describes clinical cases treated with an innovative endodontic nickel-titanium system (2Shape® system) used in continuous rotation.
Background: Nickel titanium files are commonly used for root canal treatment but they tend to break because of bending stresses and torsional stresses.
Today new instruments used on rotary have been introduced. They help the clinician to make the root canal shaping easier and safer.
Case description: We presented two clinical cases treated with 2Shape® system. It is used for complete shaping of root canal after an adequate preflaring.
Conclusion: 2Shape® seems to be helpful for the treatment of most of the root canals, with low risk of separation. The respect of clinical protocol guarantees predictable good results.
Key Words: Root canal shaping, Irrigation, Nickel-Titanium instrument
Introduction
The main aim of root canal treatment is to clean and shape properly the root canal system. This objective can be achieved only when there is a continuous tapering of the root canal which helps the irrigating solution to flow easily within the canal. This will allow a better removal of the debris and a proper placement of the obturating material 1.
Although mechanical preparation and chemical disinfection cannot be considered separately and are commonly referred to as chemomechanical or biomechanical preparation2. Considerable importance should be given not to cut excessive dentin to get adequate taper of the canal. So, the challenge for every file system is to clean and shape the root canal without cutting the excessive dentin. With the introduction of nickel titanium in endodontics, difficulties like curved canals leading to instrument fracture which were commonly encountered using stainless steel files are solved. Nickel titanium files are flexible, have good elasticity and have more resistance to fracture. They also help to maintain the original canal anatomy 3.
The property of super-elasticity and strength of the Nickel Titanium alloy have made it possible to manufacture rotary instruments with double, triple and quadruplet taper compared to the traditional standard .02 taper of the stainless steel hand instruments 4. The superelasticity of NiTi instruments allows obtaining a constant tapered root canal but in clinical practice they are always exposed to the risk of fracture 5.
Nowadays many instruments are developed by manufacturers in order to reduce this fracture risk. Therefore, knowledge of both clinical guidelines and metallurgical properties of Ni-Ti rotary instruments is critical for their successful use.
These evolutions reduced significantly file breakage that nevertheless was still haunting NiTi users and pushed forward the researches into new directions.
Thermo-mechanical treatment of endodontic wires prior, during or post machining of endodontic files enhanced the flexibility of these files.
These innovative treatment procedures opened the way for a totally new area of NiTi alloy with specific microstructural atomic composition. Combining the cumulative knowledge on file design and new heat treatment procedures. Recently, a new file system has been introduced to simplify instrumentation protocols and to reduce stresses. The 2Shape® system (Micro Mega®) is made of nickel titanium alloy and is intended for the root canal treatment till the apex.
This system consists of two instruments the TS1 and TS2 files with a tip size respectively 004 and 006 constant taper. These files are used in continuous rotary and the main characteristic is the asymmetrical cross sectional design of the working portion. The aim of this study was to report two clinical cases treated endodontically with 2Shape® system (Micro Mega®).
Case Report
Case 1
A 40 year old male referred to the Department of Conservative dentistry and Endodontics of the University Dental Clinic of Monastir with the chief complains of pain in the right mandibular region. The medical history was not contributory.
According to the clinical examination an initial diagnosis of irreversible pulpitis related to the first right mandibular molar was made and previously treated on emergency. Radiographic examination showed proximal caries approaching the distal pulp horn with no periapical radiolucency (Fig 1).
Root canal therapy was planned in single visit. Rubber dam was placed, and straight line access was obtained using round bur, Endo Z bur. Four orifices were located and cleaned. One Flare® (Micro Mega®) instrument was used to relocate canals orifices. Then glide path was achieved with manual 10, 15 K Files.
Working length determination was done with electronic
apex locator. Cleaning and shaping carried out using 2Shape® system (Micro Mega®) with copious irrigation with 2.5% sodium hypochlorite solution. Root canals were
obturated with sealer zinc oxide and gutta percha points using the lateral condensation technique (Figure 2). The coronal seal was performed by composite resin.
Case 2
A 35-year-old female patient was referred to the Department of Endodontics and conservative dentistry of the University Dental Clinic of Monastir with the chief complaint of pain and difficulty in mastication in the right mandibular region. The medical history was not contributory. During the clinical examination the first left mandibular molar revealed a painful response to percussion and a negative response to the pulp vitality test. Periodontal probing was within the normal limits. Radiographic examination revealed periapical radiolucency (Figure 3).
The clinical diagnosis was acute periapical periodontitis and an endodontic treatment was indicated. The access cavity under Rubber dam was performed using round bur and Endo Z bur. The working length was determined using an apex locator with K-files and confirmed radiographically (Figure 4).
The canal shaping was done using 2Shape® system and was prepared till the TS2 file of this system. Between filing, copious irrigation of root canal was performed with 2,5% sodium hypochlorite solution.
The canal was dried with paper points and filled with calcium hydroxide. The access cavity was sealed provisionally with a coronal filling cement ready for use (Cavit®). After 2 weeks, the patient presented to continue root canal treatment. The clinical examination revealed that the tooth was asymptomatic.
The calcium hydroxide was removed and irrigation with 2,5% sodium hypochlorite and 17% EDTA solutions was made. Canals were obturated with gutta percha cones using eugenol based sealer and then the cavity was filled with amalgam (Figure 5).
The patient was recalled after six months for follow up. He was asymptomatic and radiographically apical radiolucency showed the significant healing of the periapical lesion (Figure 6).
Discussion
Successful endodontic therapy relies on accomplishment of the objectives of endodontic therapy through the cleaning, shaping and root canal filling 10. Traditionally, the shaping of root canals was achieved by the use of stainless steel hand files. However, techniques using stainless steel hand files have several drawbacks. They require the use of numerous hand files and drills to adequately prepare the canals 11. Hand instrumentation with stainless steel files is time consuming. The stainless steel hand instrumentation techniques have an increased incidence of canal transportation 11. Nickel titanium rotary shaping files fundamentally changed everything in endodontics; conceptually, procedurally and economically as well. NiTi rotary files made root canal therapy more accessible. The 2Shape® has been introduced to prepare majority of the root canals with only two files. According to the principles of minimally invasive endodontics 12, the 2Shape® system allows preserving the tooth as much as possible. This system is simple to use. The majority of canals are shaped by two instruments, TS1 and TS2. Simplified intuitive sequence with 2 shaping instruments in continuous rotation directly at the working length. It is developed for using in continuous clock wise rotation with rotational speed at 350 rpm and torque setting at 2Ncm.
The main characteristics of these instruments are:
– An inactive tip to guide the instrument avoiding any risk of perforation 13
– A symmetrical Cross section with 3 cutting edges: the perfect compromise between cutting efficiency and debris removal. The asymmetrical cross section reduces the risk of instrument fracture.
– A progressively increasing pitch to avoid the screwing and to further improve flexibility
– 2Shape® has been heat treated using the T. Wire method, which improves the instrument flexibility (40%) and provides the practitioner with added comfort 13.
Its protocol requires an adequate preflaring before the root canal shaping. Preflaring, Canal Scouting and Glide Path are the first phases of canal instrumentation and it has also been noted that, during these phases, the clinician might more frequently encounter procedural difficulties. These problems include instrument fracture, ledge formation, canal zipping or canal straightening, strip perforation, apical perforation, elbow formation and apical blockage. All of these errors can lead to incomplete debridement of the root canal system and contribute to decreased success rates of endodontic therapy.
The minimal size of the endodontic Glide path should be a “super loose No. 10” endodontic file. The Glide path must be discovered if already present in the endodontic anatomy or prepared if it is not present 14. This can be done either with manual files 15 or with rotary files 16 such as Path files® or One G®. The advantage of a pre-shaping lies in securing the future passage of the tip of the shaping instrument.
Both instruments (TS1 and TS2) have the same Instrumental dynamics. It is a progressive movement in three waves (3 up-and-down movements) with upward circumferential filing movement. The instruments are inserted in rotation into the root canal until a resistance can be felt. At the end of each progression, we have to perform a brushing movement in order to eliminate the primary constraints. Then, the instrument is removed from the canal and cleaned. The canal is irrigated with 3% sodium hypochlorite and permeabilized with K file (15 /100). All the portions of the canal (cervical, middle and apical) are thus shaped successively according to a “crown-down” approach. Two to three cycles are usually sufficient to reach the working length.
In some cases, we require greater apical preparation, either because the canal is naturally wide or because the canal is infected and therefore the shaping and canal cleaning must be optimized 17. In these cases, one of the apical finishing instruments of the 2Shape® system is used. Either the F35 (35 / 100th tip diameter and 6% taper), or the F40 (40 / 100th tip diameter and 4% taper) for the rather curved canals. Their dynamics of use is identical to that of other 2Shape® instruments.
Conclusion
The 2Shape® system allows obtaining a good canal preparation with a sense of efficiency, security and flexibility. Also it perfectly preserves the root dentine. For these reasons the 2Shape® system seems to be helpful for the treatment of most of the root canals.
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