A. Zorian, PhD, Department of hospital therapeutic dentistry MSMSU
A. Hovsepyan, Director of the dental clinical educational center “Biosan TMS”, dentist V. Chilikin, associate Professor, candidate of medical Sciences, honored doctor of the Russian Federation, the Department of hospital therapeutic dentistry MSMSU
The success of endodontic treatment is largely determined by the quality of root canal filling. Today, high-quality filling means three-dimensional sealing of the entire branched root canal system, which plays the role of a reliable barrier between the tooth cavity and periodontal tissues.
Over the long history of endodontics, various methods and materials have been used for root canal filling.
Until recently, the main method of filling root canals in Russia was the method of filling with a single paste. At the same time, pastes based on zinc oxide and eugenol, as well as preparations containing resorcinol and formaldehyde, were very popular. The technique of filling the root canal with paste is quite simple and does not require significant time and material costs. However, filling channels with a single paste has a number of significant disadvantages: 1. With this method, only the main channel is filled with material, and numerous branches of the root canal system remain open. 2. very often, the paste is removed from the top of the root, since there is no adequate control of filling the root canal with material. 3. the Paste fills the root canal unevenly, leaving voids and not providing adequate sealing. 4. All the pastes shrink and dissolve upon contact with tissue fluid. 5. Most pastes have an irritating effect on the periodontium.
Given all of the above, it is not surprising that the international Dental Association and the Dental Association of America do not recommend the use of the method of root canal obturation with a single paste.
Materials for endodontics
The ideal filling material for root canals should meet the following parameters: 1. Ensure reliable sealing of the entire root canal system throughout its entire length. 2. Be non-toxic and have good biocompatibility. 3. Do not irritate the periodontium. 4. Do not allow shrinkage in the channel. It is desirable that it is slightly increased in volume when introduced into the channel or during the curing process. 5. Have a bacteriostatic effect or at least not support the growth of bacteria. 6. Easy to sterilize before use. 7. Be radiopaque. 8. Do not change the color of the tooth. 9. Easily removed from the channel if necessary. 10. Have sufficient curing time for comfortable operation. 11. Do not dissolve in tissue fluid. 12. Have good adhesion to dentin and filling material.
Such an ideal material does not exist today. However, to the greatest extent, these requirements are met by methods of filling root canals of gutta-percha with Siler. The vast majority of root canals around the world are currently sealed using gutta-percha.
Filling of root canals with warm gutta-percha
Gutta-percha is a solid, but at the same time elastic and flexible product of coagulation of latex of gutta-percha-bearing tropical plants. Gutta-percha is divided into two types – alpha and beta – which differ significantly in physical properties.
For the production of gutta-percha pins, beta-gutta-percha is traditionally used, which has greater hardness and spatial stability and less stickiness. Beta-gutta-percha requires higher temperatures for its softening. However, recently more and more popular is the more fluid and sticky alpha-gutta-percha, which provides a more homogeneous filling of the entire branched root canal system when used in a heated state.
Alpha-gutta-percha is used for techniques that involve working with thermoplasticized (heated) gutta-percha: vertical condensation and thermoplastic injection techniques. In addition, there is a special type of gutta-percha used for the production of “Thermafil”obturators. This patented type of gutta-percha is similar in chemical properties to beta-gutta-percha, but at the same time has the physical characteristics of alpha-gutta-percha.
The main production of gutta-percha pins is concentrated in South-East Asia. One of the largest suppliers of gutta-percha is Korea. However, recently gutta-percha pins have also been produced in Brazil.
Pins are divided into standard, having a taper of 2% and sizes from 10 to 140 according to ISO, and conical, having a taper of 2% to 12% and sizes from 20 to 30.
Gutta-percha pins are made either manually (“hand-rolled”) or by machine. It is believed that the manual method provides a higher accuracy of manufacturing pins. Machine-made pins often do not guarantee accurate calibration. It should be particularly noted that all the pins of the Brazilian production are made a machine method.
The commercial name “gutta-percha pins” is well established and used everywhere, although the content of gutta-percha proper in these pins is about 20%. The main component of pins (60-70%) is zinc oxide. The remaining 10% is barium sulfate, wax, dyes, and other additives.
The main advantage of gutta-percha is the predictability of root canal obturation. Also, its advantages include good biocompatibility and low toxicity, the ability to condense, providing a dense and uniform filling of the root canal, softening when heated, which allows for three-dimensional obturation of the root canal system, spatial stability (in the solidified state, it practically does not change its volume) and ease of its extraction from the root canal if necessary, repeated treatment.
Despite all the obvious advantages, gutta-percha has a number of disadvantages related to the peculiarities of its physical and chemical properties and application technology. Disadvantages of gutta percha are as follows: 1. It cannot be applied without a Siler, since it does not adhere to dentin. 2. gutta-Percha does not have a bactericidal or bacteriostatic effect. 3. Thin pins have a very high flexibility and softness, which requires high qualification and experience of the doctor, especially when filling narrow channels, and can also lead to deformation of the pins in the process of their packing. 4. Thermoplasticized gutta-percha shrinks when cooled. To compensate for this shrinkage, it is necessary to continue the condensation process until it cools.
Celery when obturation of the root canal
It should be noted that the need for a silo is a relative disadvantage, since there is currently no material that can provide predictable filling of the main channel, and at the same time is sufficiently fluid to fill all its branches.
Siler acts not only as a sealant that fills all branches of the root canal system and ensures the adhesion of gutta-percha to the walls of the canal, but also as a lubricant that ensures the free sliding of gutta-percha pins in the root canal.
The Siler must meet the following requirements: 1. After mixing the must have sticky consistency, that after curing to provide good adhesion to the channel walls. 2. Hermetically seal the canal. 3. Be radiopaque. 4. Do not shrink during the curing process. 5. Do not stain the tooth tissue. 6. Have a bacteriostatic effect or at least not support the growth of microorganisms. 7. Slowly freeze. 8. Do not dissolve in tissue fluids. 9. Do not irritate the periapical tissues. 10. to be Dissolved in standard solvents if necessary to seal the channel. 11. Do not cause immune reactions in the periapical tissues. 12. Do not have a mutagenic or carcinogenic effect.
None of the silos presented on the modern market can meet all the requirements for it. Generally, either natural root cements or polymer materials are used as silers today. Natural silers-Endomethasone (Septodont), Cortisomol (Pierre Rolland), Tubli-seal (Kerr), etc. – which are based on zinc oxide, dissolve in the tissue fluid, which can lead to a violation of the sealing of the root canal system. In addition, they have low adhesion to dentin and can cause staining of tooth tissues. At the same time, polymer silers – AH Plus (Dentsply), Adseal (META Biomed), etc. – are less soluble in tissue fluid, do not stain the tooth tissue and have better adhesion to the root dentin.
To date, the question of what level to seal the root canal remains open. There is a fierce debate whether the gutta-percha should not reach the anatomical apex by 0.5 mm or stop directly at it. To date, the only indisputable fact is that the less we expand the apical constriction, the better the quality of obturation, the more reliable the isolation of periodontal tissues. In addition, it is necessary to remember that the theory of active antiperspiratory therapy has shown its inconsistency. In modern endodontics, the removal of Siler by the root tip is not encouraged even in the presence of inflammatory processes in the periodontium, although studies have shown that when a small amount of Siler is removed to the periapical tissues, there are no serious complications after treatment.
There are various methods of filling the root canals of gutta-percha: the method of one (Central) pin, lateral condensation, thermomechanical condensation, filling the root canal with chemically softened cold gutta-percha, intra-channel hot vertical condensation, thermoplastic injection technique and the use of thermaphiles.
Root canal filling with cold gutta percha
Single pin method
This method consists in applying a Siler to the walls of the channel using a paper pin after appropriate treatment of the channel, which implies giving it a taper of 4, 6 or 8%. After that, a pre-selected pin with the appropriate taper and tip size is inserted into the channel. The pin must fit snugly against the channel walls. Some authors recommend shortening the tip of the pin by 0.5 mm. Using a heated tool, the pin is cut off at the level of the mouth and its condensation is carried out in the vertical direction.
This technique can be a good alternative for doctors who prefer to seal the channels with monopast, but it only provides filling of the lumen of the main canal, and not three-dimensional obturation of the entire root canal system.
Technique of lateral condensation of cold gutta percha
This scheme implies filling with gutta-percha pins with lateral pressing of each of the pins to the walls of the channel. For a long time, this technique was the “gold standard” with which all other techniques of canal obturation were compared.
After drying the root canal with paper pins, its walls are coated with Siler. Then a master pin of the same size is inserted into the channel, the tip of which is wetted in the same sealant. Then, using a spreader, the master pin is condensed to the channel walls, providing enough space for additional pins to be inserted. The density of the channel obturation depends on the depth of penetration and the shape of the spreader. According to Chohayeb (1993), ISO-standardized manual spreaders should be inserted into the root canal at a distance of up to 1 mm from the tip of the gutta-percha pin, which improves the homogeneity and density of the filling. After condensation of the master pin, additional pins are condensed to it and the channel walls, the tips of which are also wetted in the sealant. Each subsequent pin enters the channel at a lower depth. Lateral sealing of the pins is carried out until the channel is filled homogeneously, the criterion for which is the inability to insert the spreader into the channel. The recommended time for pinning the spreader to the channel walls according to different authors is 15-30 seconds. After that, the protruding ends of the gutta-percha pins are cut off with a heated tool, and the vertical condensation of the gutta-percha closes the mouth of the channel.
The quality of root canal obturation during lateral condensation of cold gutta-percha is influenced by many factors. First of all, this is the form of the processed channel. The root canal should have a uniform taper along its entire length and an apical ledge that prevents the material from escaping beyond the apex during condensation. Also of great importance is the ratio of gutta-percha and Siler. We recommend the following ratio: 95% gutta-percha, 5% Siler.
Long-term use of the technique of lateral condensation of gutta-percha has shown its high clinical effectiveness, ease of use and reliability. Many researchers point to a high density of root canal filling during lateral condensation. However, other authors demonstrate that when performing lateral condensation, there is a risk of longitudinal root fracture due to the effort involved, especially when the root is weakened (for example, when channels in thin roots are excessively expanded). In addition, this method does not achieve uniformity of material and filling of gutta-percha lateral and apical branches of the canal, which can lead to the development of complications from periodontal tissues – the development (or maintenance) of an inflammatory reaction, destruction of bone tissue.
It should be added that when working with cold gutta-percha for adequate sealing of the mouth of the root canal, it is desirable to use a heated tool to cut the pins 2-3 mm deeper than the mouth of the channel and fill the remaining part of the heated gutta-percha by injecting it.
In order to improve the technology of filling root canals with cold gutta-percha, various methods were proposed, which are currently of interest for the most part only from the point of view of the history of endodontics development. These methods include thermomechanical condensation and filling of chemically softened cold gutta-percha.
Thermomechanical condensation (or root canal filling with a rotating condenser)
This method is currently almost not used. In this method, the tool, which has elements of the H-file in its design (but with the reverse course of the thread) and the channel filler, is used to soften the gutta-percha and move it in the apical direction. This instrument is called a condenser or gutta-condenser. To soften the gutta-percha and condense it, the tool must rotate clockwise at a speed of at least 8000 rpm.
A standard gutta-percha pin should be 1-2 sizes larger than the last tool used for channel processing, i.e. 1-2 mm shorter than the working length. Control of the level of filling of gutta-percha is provided by the introduction of a tool, 1.5 mm short of the apical constriction.
The disadvantages of the method are the unpredictability of the level of sealing, the high risk of breaking the tool in the channel, and the probability of voids in the gutta-percha due to its adhesion to the tool. In addition, this technique also does not provide reliable obturation of the lateral branches of the channel.
Filling of root canals with chemically softened cold gutta percha
Methods of filling chemically softened cold gutta-percha are also called “immersion methods”. Historically, these methods appeared almost simultaneously with the beginning of the use of gutta-percha. When obturating gutta-percha softened with solvents (chloroform, some oils), Siler was not used. This led to micro-percolation due to shrinkage of the gutta-percha after evaporation of the solvent and curing of the root seal. Therefore, the frequency of complications when using such methods was very high. Despite the fact that later various silers were used for “submerged” methods, these techniques are now practically not used due to the inability to control the shrinkage and deformation of gutta-percha and the quality of the obturation of the channel.
Root canal filling with thermoplasticized (heated) gutta-percha
Vertical condensation
The technique of vertical condensation of heated gutta-percha was proposed in 1967 by Shilder. With this method, the gutta-percha pin (master pin) is selected individually by diameter and taper. It is installed in the channel so that its tip does not reach the apical narrowing by 0.5-1 mm.
The vertical condensation technique consists of the following steps: 1. a Preheated spreader removes excess gutta-percha from the root canal. 2. using a plugger, the heated gutta-percha condenses in the channel. 3. the Heated smaller spreader is immersed 3-4 mm in the middle part of the gutta-percha pin and after it cools down, excess gutta-percha is removed from the walls. 4. a smaller Plugger condenses the softened gutta-percha in the apical direction. 5. The preheated spreader of the smallest size is immersed in the gutta-percha, removing the next portion of the material. 6. The smallest plugger condenses the apical portion of gutta-percha, obturating all additional channels in this area. 7. then, segments of a gutta-percha pin approximately 3 mm long are inserted into the canal, which are thermally softened and compacted, gradually filling the root canal.
The advantages of this method are really three-dimensional filling of the root canal (that is, filling all additional channels and branches with the maximum amount of gutta-percha and the minimum amount of Siler) and homogeneity of the root filling.
The disadvantages include the complexity of the technique and the possibility of removing the material over the top (although the risk of this with proper processing of the channel and strict compliance with the technique is small).
Continuous wave technique
A variation of the vertical condensation technique is the “continuous wave” technique developed by Buchanan. When performing obturation using this method, the System B device (SybronEndo/ analytical) and the corresponding pluggers are used.
The method consists of two stages. At the first stage (“Downpack») using preheated to 200°From the plugger, the master pin installed in the root canal of the appropriate size and taper is cut off in the middle third of the channel and condensed in the apical direction. This ensures that the apical part of the canal is sealed.
In the second stage (“Backfill”), a gutta-percha pin of the same size is inserted into the root canal, and a system B plugger heated to 100°C is cut and condensed in the apical direction, after which the next pin is inserted into the canal. The procedure is repeated until the channel is completely filled.
This technique is easier to perform compared to the vertical condensation technique. The main concern was the introduction of a tool heated to 200° C so close to the apex. However, studies have shown that such a short time of exposure to high temperature can not have a damaging effect on the periapical tissues.
Thermoplastic injection technique involves the introduction of a root canal heated to a molten state of gutta-percha under pressure with a special syringe. The most popular such system is Obtura II (Obtura Corp.).
The method is quite simple and easy to use. However, this injection only fills the main channel, and requires additional hot condensation in the apical and lateral directions to fill the lateral branches and the apical Delta. In addition, often with this method, the root canal is filled with gutta-percha not to the top, which often requires removing the inserted gutta-percha and re-filling the canal to avoid the development of complications from the periodontal.
Combined method
Many authors have pointed out the advantages of the combined use of methods of vertical condensation and injection of gutta-percha. However, until recently, this approach required the use of two separate devices (for example, System B and Obtura II). Today, there are systems that allow combining the advantages of vertical condensation techniques and injection of heated gutta-percha using just one device (Elements Obturation Unit, SybronEndo; E&Q Plus, MetaDental, Co.). The only such system currently available on the Russian market is E&Q Plus.
E&Q Plus System
The “E & Q Plus” system consists of a control unit with a digital display of the gutta-percha heating temperature, a gutta-percha injection gun and a tip with special nozzles that warm up the gutta-percha in the channel.
Thus, “E&Q Plus” actually combines the “System B” and “Obtura II” systems, allowing the doctor to take advantage of both. At the same time, both functional systems “E&Q Plus” (tip and gun) can be used separately or together.
The method of working with the “E&Q Plus” system is as follows: 1. Select the appropriate apical master pin. It should have the same taper as the prepared root canal and run its entire length. 2. the Tip of the pin is cut off by 0.5-1 mm, so that when compacting the gutta-percha, it does not go beyond the top of the channel. 3. the Pin is stored in the root canal. 4. Are selected corresponding pluggery, and their length is fixed by silicon stoppers. 5. the “E&Q” nozzle is Selected, which does not reach the working length by 5-7 mm. The length of the nozzle entry is fixed using a stopper. 6. after drying the channel and applying the Siler, the master pin is installed. 7. At the end of “E&Q” exhibited a temperature of 250°C. The nozzle is inserted into the channel at a measured length and activated by cutting off the gutta-percha in the crown part. 8. Preheated gutta-percha is condensed using a plugger. 9. the procedure of heating and compacting the gutta-percha is repeated until adequate obturation of the apical part of the canal is achieved.
Further, the filling can be performed either using gutta-percha pins using the vertical condensation method, gradually filling the middle and crown thirds of the channel, or by portioning the heated gutta-percha with an “E&Q” gun, followed by compacting each portion with a plugger of the appropriate size.
The “E&Q Plus” system provides fast and predictable three-dimensional obturation of the root canal system. Vertical condensation of gutta-percha in the apical part allows it to be securely sealed without removing the material from the top. In addition, the doctor always has the option of choosing a filling technique for a specific clinical situation, and at the same time can use different methods of obturation, even in different channels of the same tooth.
The obturator “Thermafil” are plastic bars (carriers) are coated with gutta-percha with a patented formula. A special oven is used to heat the gutta-percha. The idea of “Thermafil” obturators belongs to W. B. Johnson.
After selecting the pin, performed with a special tool – verifier, a small amount of Siler is applied to the walls of the channel in the mouth and middle third using a paper pin. Thermafil is heated for 15 seconds in a special oven, inserted into the root canal for the required length, after which the carrier of gutta-percha is cut off with boron. In this case, gutta-percha fills all the additional channels and the apical Delta, providing three-dimensional filling of the entire root canal system.
This technique is easy to use and reliable. Its effectiveness, especially in complex branched root canal systems, is not in doubt today. The disadvantages of this method can be attributed, perhaps, only a higher probability, in comparison with other methods, of transapical removal of gutta-percha, especially in root canals with an unformed tip, a large diameter of the apical opening, or with active overhanging processes that lead to resorption of the root tip.
Conclusion
Currently, we are actively searching for new materials for obturation of the root canal system. The main focus is on composite materials, which include radiopaque components. Such materials include Resilon (Resilon Research LLC). Resilon is a thermoplastic filled polymer based on polycaprolactone used with composite double-curing silers (e.g. Epiphany, Pentron Clinical Technologies). The method of root canal obturation using the “Resilon” material is a combination of the “continuous wave” technique and injection of a heated material.
Since the method of introducing thermoplastic composites into the root canal is identical to that of working with thermoplasticized gutta-percha, it will not be difficult for a doctor who has mastered working with heated gutta-percha to switch to the use of such materials.
However, in the near future, most likely, there will not be an alternative to gutta-percha that can compete with it in terms of practicality, as well as in terms of price-quality ratio of the result obtained. Therefore, in the coming years, gutta-percha will remain a universal material for root canal obturation during endodontic treatment.
The material was provided by OOO “Medenta»