Expansion of the root canal orifices. Reception at Dent Prestige is by appointment only. You can make an appointment by phone.

When is root canal treatment necessary?

Treatment and filling of canals are stages of endodontic treatment. The doctor opens the tooth to treat the following diseases:

deep caries - the last stage of the disease, characterized by extensive damage to dentin, accompanied by severe toothache that appears when chewing, pressing on the tooth, eating cold and hot foods and drinks;
pulpitis - inflammation of the neurovascular bundles located in the tooth cavity, most often occurs against the background of advanced caries, characterized by paroxysmal pain, which intensifies when eating hot or cold food;
periodontitis - inflammation of the apex or edge of the tooth root, develops due to damage to the connective tissue that holds the dental unit; symptoms of the disease are acute pain, swelling of the gums, swelling of the lip or cheek, as well as pathological mobility of the tooth.

The main reason for the development of these diseases is non-compliance with the rules of oral hygiene. If you brush your teeth twice a day and visit the dentist regularly, these problems can be avoided. Experts recommend undergoing a preventive examination every six months. In this case, the doctor will be able to detect caries at an early stage and promptly eliminate it, thereby preventing the development of pulpitis and other complications.

Anatomy of a dental canal

In addition to hard tissues (enamel and dentin), the structure of all teeth contains quite large cavities. They are called pulp chambers and are filled with soft connective tissues, vessels, and nerves. Smaller branches extending along the length of the root extend from the pulp cavity; they are called dental canals. Their number depends on the number of roots. In the front teeth there is only 1 canal, in the lateral teeth their number can reach up to 5.

The canal begins at the root apex, at which it opens with the apical foramen. A nerve and several vessels pass through it into the tooth. Further, the channel is a narrow tube with many branches. Thanks to the presence of these structures, the tooth receives nutrition and metabolic processes take place in it. And sensitive nerve fibers allow the body to monitor the condition of dental tissue.

Stages of treatment

Endodontic dental treatment includes the following stages.

Diagnostics. Interviewing the patient, collecting complaints, examining the oral cavity. X-ray examination may be needed to confirm the diagnosis. It will allow you to determine the degree of carious lesions and evaluate the structural features of the tooth.
Preparation of a carious cavity. All dead tissue is removed from the crown of the tooth.
Tooth depulpation. The pulp is removed from both the coronal and root parts.
Determination of channel length. It largely depends on the size of the root and its bends. To measure it, X-ray and electrometric methods are used.
Expansion of the root canal mouth. Simplifies subsequent processing. For expansion, intracanal instruments are used - small burs, endodontic files.
Mechanical restoration. All infected dentin is removed. Hard tissues are thoroughly cleaned.
Filling. The cleaned cavities are filled with filling material and the integrity of the tooth is restored.

Solving problems with very curved channels

The ultimate goal of endodontic treatment is to prevent the development of periapical lesions, as well as to create an environment conducive to their healing. To achieve such goals, it is necessary to adhere to certain classical principles of chemical disinfection and mechanical treatment of the root space. It is important to note that it is the success of the mechanical treatment of the endodontist that determines the effectiveness of all subsequent iatrogenic manipulations performed in the root canal.

For reliable obturation of the canal space with gutta-percha, it is necessary that it meet certain criteria, including:

continuous conical shape of the main root canal, resembling a tapering funnel from the mouth to the apical foramen;
narrowing of the cross-sectional diameter of the main canals in the apex area;
preservation of the original shape of the channel during its processing;
maintaining the original position of the apical foramen;
maintaining the size of the apical foramen whenever possible.

The biological purpose of mechanical treatment of the endodontic space is as follows:

restriction of the work of endodontic instruments within the boundaries of the root canal;
prevention of extrusion of necrotic tissue into the postapical region;
removal of all organic tissues from the space of the main and additional canals;
creating a space of sufficient size to ensure effective irrigation and medicinal treatment without compromising the functional state of the tooth through excessive reduction in the thickness of dentin tissue.

Achieving the above goals in straight root canals is a fairly clear and logical process, however, in cases where there are various forms of anatomical variations in the endospace, this task becomes noticeably more complicated. It is especially difficult to achieve an adequate result of mechanical treatment of the canal in those with a pronounced bend of the endospace or in the presence of furcations and additional anastomoses (photo 1). It is quite difficult to follow classical intervention algorithms in such cases, therefore, to solve such problems, special NiTi files were developed, the sequence of application of which using the TCA technique helps to optimize the results of machining.

Photo 1a-c. Complex anatomical structure of root canals.

Treatment of canals with bends

Based on canal curvature, Nagy et al classified root canals into the following four categories:

Straight or I-shaped (28% of root canals);
Apically curved or J-shaped (23% of root canals);
Curved along the entire length or C-shaped (33% of root canals);
Multiple curved or S-shaped canals (16% of root canals).

Schäfer et al found that 84% of the root canals they studied were curved, while 17.5% had a second curvature and were classified as S-shaped. Of all the root canals with curves analyzed, 75% had a curvature level of less than 27°, 10% had a curvature ranged from 27 to 35°, and 15% had a pronounced curvature of more than 35°.

Traditionally, the severity of root canal curvature is described using the Schneider angle parameter: root canals with a bend of up to 5° are classified as straight canals, with a bend of 10 to 20° as moderately curved, and canals with a curve of more than 25° as severely curved. curved. Decades later, Pruett et al reported that two curved root canals can have the same Wein angle but completely different curvature parameters. To evaluate the latter, the radius of curvature parameter was introduced, which is defined as the radius of a circle passing through the curvilinear part of the channel. When using rotary tools, the number of cycles until the tool fails is significantly reduced as the radius of curvature decreases and the angle of curvature increases. Further attempts to mathematically describe the curvature of the channel on the basis of available two-dimensional radiographs led to the introduction into the theory of such parameters as the length of the curvature and its location, determined by the height and distance of the curvature. Estrela et al described a method for determining the radius of curvature of the root canal using CBCT slice data, which the scientists analyzed in specially developed software. According to their approach, the following three categories of root canal curvature were identified: small (r=4 mm), intermediate (r=4-8 mm) and large (r=8 mm). The smaller the radius of curvature, the greater its steepness. All of these attempts to describe root canal curvature had one goal: to develop an approach to assess the risk of apical foramen transportation and unexpected instrument separation.

Transport of channels and separation of instruments

According to the Glossary of Endodontic Terms, canal transport is the removal of the root canal wall structure on the outer side of the curvature in the apical half of the canal due to the properties of the files to restore their original linear shape. For stainless steel hand files and hand and machine NiTi files, the shape recovery properties are directly related to the size and taper of the tool. The larger the size and taper of the file, the more the file tries to restore its original shape, which is associated with an increase in the mass of metal in the structure of the tool. If the files exactly repeated the morphology of the endospace, then problems with transporting the canals would not arise at all, since in such an ideal situation the file would move strictly along the trajectory of the canal. Because the shape of the channels and instruments is different, each instrument moves along its own path within the curved channel, which is determined by its ability to recover. When attempting to increase the size of the apical foramen during mechanical treatment, as a rule, the amount of reduction of dentin tissue on the outer apical part of the curvature increases. To prevent this effect, doctors try to use instruments of a larger cone, but of a smaller size, for mechanical processing of the apical space in canals with pronounced curvature. Increasing the cone with this approach leads to a reduction in the angle of the bend, a decrease in its length and an increase in the radius with a reposition of the bend more apically (photo 2).

Photo 2. Treatment of the endospace leads to changes in bending parameters.

Reducing the volume of treatment of the apical part of the canal in those with pronounced curvature is indicated with the need to achieve the following goals:

a smaller preparation diameter is associated with a smaller volume of canal wall reduction, a smaller increase in file size, and therefore with a lower risk of developing undesirable effects;
files of smaller diameter are characterized by greater elasticity and less resistance to fatigue, thus, when working with these files, the possibility of transporting the canal as the size of the apical foramen increases is reduced.

The above-mentioned approaches to instrumental treatment of root canals, although safer, are also characterized by a number of disadvantages. Firstly, an increase in the taper of the endospace in its coronal part to ensure easier patency in the apical third provokes excessive reduction of dentin tissue, which compromises the biomechanical prognosis of the tooth. In addition, processing canals with smaller files makes it difficult for irrigation solutions to penetrate to the appropriate depth of the endospace. In canals with pronounced bends, the possibility of adequate irrigation of the root canal directly depends on the possibility of sufficient instrumental expansion of the apical third. Apical preparation of the apical part of the canal in order to achieve the appropriate level of disinfection in conditions of pronounced curvature is one of the most difficult practical tasks in endodontics, especially considering the prevalence of modern principles of minimally invasive interventions. In addition, there is a high risk of separation of rotary mechanical files in canals with pronounced curvature. The causes of such complications can be two main mechanisms: cyclic fatigue and torsion fatigue. When a rotary tool is activated within a curved channel, constant tensile and compressive stresses are generated within the physical center of rotation of the curvature. If the tip of the file is blocked in the endospace structure and the motor continues to rotate, the shear moment of the tool material exceeds its limit values, which also leads to the development of maximum levels of torsional fatigue (torsional fatigue). The greater the complexity of the morphology of channel bends, the fewer cycles of operation under such conditions the instrument can withstand.

Using Shape Memory Controlled Files

NiTi alloys are softer than stainless steel, but have a lower level of elasticity (about one-fourth to one-fifth that of stainless steel). At the same time, this material is more durable, rigid and elastic, due to which NiTi files are characterized by shape memory. NiTi files used in endodontics contain approximately 56% nickel and 44% titanium. However, they can exist in the form of two different temperature-dependent crystal structures called martensite (low-temperature phase) and austenite (high-temperature phase). The lattice organization can be transformed from austenitic to martensitic state by controlling temperature and stress. During the reverse transformation, the alloy passes through an unstable intermediate crystallographic phase called the R phase. The use of files during endodontic treatment provokes the development of stress, which, in turn, causes an instantaneous martensitic transformation of the NiTi file. A change in the shape of a tool is associated with a change in the parameters of its volume density. It is this property of the file, which is the ability to withstand stress without developing permanent deformation, that is called superelasticity. Superelasticity is most pronounced at the beginning of stress development, when the tool can easily overcome up to 8% deformation. After 100 deformations, this level drops to 6%, and after 100,000 – to 4%. It is within these boundaries that the shape memory effect is observed. In addition to stress, martensitic transformation of a file can also be caused by temperature changes. When the austenitic phase of a NiTi file cools, it begins to transform into martensitic phase. The temperature at which the martensite phase is completely restored again is called the temperature of the final transformation of martensite. When the martensite phase is heated, it begins to transform into the austenite phase. The temperature at which this phenomenon begins is called the temperature at which the austenite phase begins. At the final transformation temperature of austenite and above (Af), the material completes its shape memory transformation and demonstrates its superelastic properties. Until 2011, the Af temperature for most available NiTi tools was at or below room temperature. As a result, during clinical use, conventional NiTi files were in the austenitic phase, exhibiting their shape memory and superelasticity properties. In 2011, COLTENE introduced controlled shape memory files (CSF). The production of these tools involves the implementation of a unique thermomechanical process that controls the memory of the material, providing special elasticity and durability of the files, which is not typical for all other types of NiTi analogues. The Af-transformation temperature of CPF files is clearly higher than body temperature, as a result of which these files are in the martensite stage during operation in the endospace. In this phase, the instruments remain soft, plastic, without shape memory, and can be easily deformed, but after that they restore their shape and original elastic properties when heated to temperature Af.

A hybrid martensitic microstructure, like that used in HyFlex CM (COLTENE) files, also has a higher level of strength than an austenitic microstructure. At the same stress intensity, the rate of crack propagation in the structure of the austenitic phase is much higher than in the martensitic phase. A quantitative model for studying the process of crack development in the file structure made it possible to establish that the martensitic transformation of NiTi files increases the fracture strength of the tool by 47%.

More recently, the thermomechanical processing mechanism of CM has been combined with the mechanical fabrication procedure of NiTi files. Thanks to electrical discharge machining (EDM), it was possible to increase the surface hardness of files, their cutting efficiency and achieve unique parameters of resistance to functional fatigue. In the first published paper that demonstrated the results of using these files, the surface of the instruments was described as typical after an intrinsically safe specific treatment, and the level of degradation remained quite low even after multiple endodontic procedures. The authors also found that these files have surprisingly high levels of resistance to cyclic fatigue, and have a high safety profile even when working in highly curved canals, which has been confirmed in laboratory conditions. Pedulla et al also reported higher fatigue resistance values for HyFlex EDM (COLTENE) files, even compared to reciprocating machining and M-wire files.

Unfortunately, the literature data concerning the study of flexural stiffness and fracture resistance during the development of cyclic fatigue were carried out on NiTi files at room temperature. However, room temperature is not clinically significant. The use of modern instruments takes place at body temperature, which automatically excludes the possibility of direct application of the findings of previous studies in clinical practice. It is apparent that the transformation temperature (Af) of NiTi files designed for rotary or reciprocating processing can influence their clinical behavior under normal human body temperature conditions. Hulsmann et al (2019) reported that ambient temperature has a 500% influence on the service life of endodontic instruments. If the transformation temperature approaches body temperature, this can cause tools to appear flexible and fatigue resistant, but in fact become more rigid and less fatigue resistant. The Af of HyFlex EDM files was found to be close to 52°C, which is much higher than body temperature. Temperature analysis of EDM files confirmed the presence of a monoclinic structure of B19 martensite and a rhombohedral R phase. Thus, EDM instruments are always in the rhombohedral R-phase and martensitic crystallographic state at clinically relevant temperatures during endodontic treatment. The martensitic structure at body temperature allows these files to have excellent flexibility and resistance to fracture, as well as the absence of restoring forces, making them ideal for use during the machining of curved or morphologically complex canals.

Sequence of using HyFlex EDM Max files when processing curved canals

EDM technology has made it possible to implement the principle of endodontic expansion with a single rotary file. Generally, in most clinical cases, a 25/~ HyFlex EDM OneFile can be used with short peck movements while being sure to keep the instrument edges clear of debris and provide adequate irrigation. The OneFile is characterized by a size of 25 with a taper of 0.08. In this case, the taper of 0.08 is constant in the upper apical 4 mm of the instrument, but gradually decreases to 0.04 in the coronal part of the instrument. The file is characterized by the presence of three different cross-sectional zones along the entire length of the working part (rectangular in the apical part and two different trapezoidal cross-sections in the middle and coronal parts of the instrument). Thus, the developers managed to increase the file’s resistance to destruction and its cutting efficiency. When wider apical preparation is required, the designer introduces the following three HyFlex EDM finishing files with constant taper (40/.04, 50/.03 and 60/.02). For narrowed and obliterated canals, as well as for thin, long and S-shaped canals and canals with more than a 27° bend and a radius of curvature of less than 5 mm, a single file protocol is not indicated. In such cases, it is necessary to combine tools in order to achieve the most predictable treatment result. This is why the developer has also provided the Max Curve HyFlex EDM tool sequence, which includes files 15/.03, 10/.05 and 20/.05. The use of these files allows us to minimize the process of increasing the taper of the endospace, thus ensuring the minimum possible reduction of dentin on the canal walls. The Max Curve HyFlex EDM tool sequence can be used with the tactile controlled activation technique. Once the canal is identified, the minimal carpet is recreated using a 10/.02 stainless steel hand file. The 15/.03 HyFlex EDM tool is then used to follow the path of the carpet. After this, the 10/.05 HyFlex EDM file is used to widen the middle part of the canal. The apical 3 mm of the 10/.05 file act as a guide tip (without adhesion to the canal walls, photo 3). File 20/.05 HyFlex EDM is used as a final file to achieve the final smooth shape of the canal. After expansion with a 20/.05 instrument, the canal can be obturated with a 20/.05 gutta-percha cone and GuttaFlow biothermal sealer (COLTENE). The file sequence is easy to remember and ensures efficient and safe treatment of the endospace even in the most difficult clinical situations.

Photo 3. Sequence of HyFlex EDM Max Curve files.

Tactile control activation

In order to minimize the approach of using files with increasing taper, a tactile-controlled activation technique was proposed (photo 4a). This mechanical endospace technique can be defined as activating the stationary file only after it has been completely inserted into the patent canal. Essentially, the activation of the file occurs after the tactile sensation of achieving maximum adhesion of the cutting grooves to the walls of the endospace. Passive (non-activated) application of files is also useful, especially in cases of limited oral opening and incomplete visualization of the working field. Tactile-controlled activation can be classified into that during tool movement and during tool withdrawal. After creating access to the pulp cavity and localizing the mouths of the canals, their patency is ensured by the 10/.02 instrument. After this, the 15/.03 file is installed in the tip and inserted into the endospace until maximum resistance is felt (point A, photo 4b).

The file is then activated and pushed in the apical direction until the activated file reaches the point of resistance (point B, Fig. 4c). After this, the file is removed from the channel. The cutting edges of the instrument are cleared of debris, checked for deformations, and irrigation of the endospace is provided. The second time the same file is introduced, which can now go deeper in a passive state (point B, photo 4d). Re-activating the file will allow the file to advance the required length closer to the apical foramen (point C, photo 4e–g). Work with this tool is stopped only after it reaches the working length (point D, photo 4h). After reaching the working length, begin using the second file in the Max Curve sequence according to the protocol described above.

Photo 4a-h. Tactile controlled activation.

The thin apical 2 mm of a 10/.05 file will always remain free within the canal, which guides the file along the path of the endospace anatomy without the risk of developing excessive retention and breakage. File 20/.05 will ensure the final formation of the endospace and the conditions to ensure its proper disinfection and obturation. Mechanical processing of wider apical openings is achieved by increasing the width of the instruments used in particularly complex canals, such as those shown in photos 5 and 6; The use of a 20/.05 file would be most indicated, given the need to achieve proper disinfection of the endospace and minimize the risk of instrument separation. The TKA technique aims to minimize the time it takes to expand the endospace with an activated file, using file activation only when necessary to advance the instrument. With this approach and through the use of HyFlex EDM Max Curve files in a sequential manner, most anatomical variations of root canals can be treated without compromising the safety profile of the procedure.

Photo 5a-g. Treatment of the S-shaped mesiobuccal canal of the maxillary second molar using HyFlex EDM Max Curve files using the TKA technique: a) pre-treatment radiograph; b) radiograph after treatment; c) formation of the access cavity; d) view after processing with HyFlex EDM 15/.03 file; f) processing with HyFlex EDM 20/.05 file; f) obturation with gutta-percha pins 20/.05; g) view after obturation.

Photo 6a-d. Treatment of the S-shaped mesial canal of the mandibular second molar using HyFlex EDM Max Curve files: a) visualization of deep carious lesions; b) view after processing with HyFlex EDM 15/.03 file; c) view after obturation; d) view after restoration.

conclusions

NiTi files with CM effect are extremely flexible and have excellent fatigue resistance. They can be activated within the canal and passively moved along the bending path, guided by the original anatomy of the endospace. The TKA technique allows minimizing the time of close interaction of files with root dentin. During mechanical processing of the endospace, constant feedback tactile control of the manipulation is provided. For particularly complex clinical cases, a special sequence of HyFlex EDM Max Curve files has been developed, allowing clinicians to stay in tune with constantly moving progress.

Author: Dr Antonis Chaniotis (Greece)

Canal filling methods:

The classic way to properly fill canals is to fill them with a special latex-like material called gutta-percha. There are several methods for filling canals with this material: thermofil, lateral condensation and thermogutta-percha.
Thermafil and lateral (side) condensation are used only on accessible roots. While hot thermogutta-percha (which is a moving warm mass) fills both the main channel and microchannels, which cannot be reached with instruments. When hardened, this material blocks all microcracks and pores so that microorganisms are guaranteed to no longer multiply in them. Actually, filling tooth canals with hot thermogutta-percha is the most modern and progressive method. The filling time for a three-root canal is about two hours.

The success rate of tooth canal treatment is the restoration of the functioning of its root. If the root is in order, then you can continue to work with the tooth, for example, carry out restoration.

Isn’t it easier not to bother with treatment, but to immediately pull out the tooth and install a denture? Not easier. After all, the root is the basis of the tooth, which can serve as the foundation for prosthetics. Therefore, root and root canal treatment must be taken seriously. Despite the fact that the root is a complex sector of treatment (it is difficult to even just see it, let alone intervene). In addition, the dental root canals have an individual structure, branch and form canals, so they are not easy to process. Therefore, the procedure for treating pulpitis should be carried out only in a professional clinic where well-trained dentists work.

Features of root canal treatment under a microscope

Modern dentistry cannot be imagined without the use of innovations that take root canal treatment to a new level. One of the most advanced methods of root canal treatment is the use of a dental microscope. Powerful optics allow you to increase your view by 32 times, given that the diameter of the channel is usually no more than 1 mm, it is simply impossible to process it efficiently without the help of optics.

Advantages of dental treatment under a microscope:

The endodontist sees in detail the mouths of the canals, the features of their structure, each branch, depth and direction. This is especially important if the tooth canal has a complex, convoluted shape.
The microscope makes it possible to remove only diseased and dead tissues without damaging healthy ones.
Thanks to the targeted effect on the tissue, the best result of the intervention is ensured, eliminating the likelihood of perforations, as well as other problems and complications.

The use of a dental microscope allows the dentist to successfully solve even the most complex clinical problem.

Is it painful to treat root canals?

Thanks to the use of modern anesthetics, root canal treatment has become a painless procedure. The patient may feel mild discomfort only during the injection of the anesthetic.

Therefore, there is no need to be afraid of root canal treatment; moreover, you must remember that you should never postpone the procedure due to fear of the dentist! Inflammation in a tooth that has progressed to a certain stage of development cannot be cured, which means that the diseased tooth will have to be removed and a prosthesis put in its place. In addition, more serious complications may occur.

In what cases is endodontic treatment contraindicated?

There are few contraindications to endodontic treatment, including:

Significant destruction of hard and soft tooth tissues.
Mechanical injuries of the jaw.
Individual structural features of the dental canals that do not allow for reliable cleaning.

If there are contraindications, the only option is complete tooth extraction. An untreated source of inflammation is a direct threat to the health and life of the patient, so even such radical methods are used if necessary.

Where is the tooth canal located, how is it structured

Human teeth have almost the same anatomical structure, including three main parts: crown, neck and root. Inside the tooth there is a pulp chamber, from which canals originate and extend all the way to the root. The pulp chamber contains the pulp or nerve of the tooth, which is a bundle of nerve fibers and blood vessels. Nerve fibers and vessels also pass through the entire internal space of the dental canal. The shape of the tooth canals can be either straight or curved, and their number varies depending on the type of tooth. Thus, the canines and incisors of the upper jaw have one canal, the canines and incisors of the lower jaw have two. There may be two or three canals in molars, and the maximum number of canals is observed in wisdom teeth - from three to five. The exact number of dental canals is determined using radiographic examination.

As mentioned above, the shape of the canals can have bends and turns, which complicates the process of their high-quality cleaning and treatment. Meanwhile, when treating canals, it is important to thoroughly clean their internal space - otherwise it will not be possible to stop the inflammatory process and save the diseased tooth.

Smear layer: to remove or not

When the endodontic instrument comes into contact with the root canal wall, a smear layer is formed. The smear layer consists of the remains of dentinal filings, microorganisms and their toxins. The organic part consists of proteins, microbes, cells, and pulp residues. The inorganic part consists of dentin components.

It has been studied that the smear layer is able to penetrate to varying depths into the lateral tubules, spreading the infection throughout the root canal system. At the same time, it is a physical barrier to microorganisms. It has been scientifically proven that the presence of a smear layer disrupts the adhesion of the sealer in the canal, promotes microleakage, which triggers even greater bacterial growth. Being an obstacle to the penetration of sealer and irrigant into the tubules, it significantly reduces the quality of permanent root canal filling.

The organic component is a breeding ground for bacteria and is easily removed by sodium hypochlorite. The inorganic component of the smear layer is unstable to EDTA and citric acid. The mechanism is associated with demineralization of peritubular dentin and opening of dentinal tubules.