Methods of filling (obturation) of root canals

A. Zorian , Candidate of Medical Sciences, Department of Hospital Therapeutic Dentistry, Moscow State Medical University

A. Hovsepyan , director of dental clinical training, dentist V. Chilikin , associate professor, candidate of medical sciences, Honored Doctor of the Russian Federation, Department of Hospital Therapeutic Dentistry of Moscow State Medical University

The success of endodontic treatment is largely determined by the quality of root canal filling. High-quality filling today 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 techniques and materials have been used to fill the root canal.

Until recently, the main method of filling root canals in Russia was the method of filling with one 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 a root canal with paste is quite simple and does not require significant time and material costs. However, filling canals with one paste has a number of significant disadvantages: 1. With this technique, only the main canal is filled with the material, and numerous branches of the root canal system remain open. 2. Very often the paste is discharged beyond the root apex, since there is no adequate control over the filling of the root canal with material. 3. The paste fills the root canal unevenly, leaving voids and not providing adequate sealing. 4. All pastes shrink and dissolve upon contact with tissue fluid. 5. Most pastes have an irritating effect on the periodontium.

Considering all of the above, it is not surprising that the International Dental Association and the American Dental Association do not recommend the use of the root canal obturation technique with one paste.

Endodontic materials

An ideal root canal filling material must meet the following parameters: 1. Provide a reliable seal throughout the entire root canal system. 2. Be non-toxic and have good biocompatibility. 3. Do not irritate the periodontium. 4. Do not shrink in the canal. It is desirable that it expands slightly when introduced into the canal 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. If necessary, it can be easily removed from the canal. 10. Have a curing time sufficient for comfortable work. 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, these requirements are best met by the methods of filling root canals with gutta-percha and sealer. The vast majority of root canals around the world today are filled using gutta-percha.

Temporary canal filling

If indicated, the doctor can fill the canals after depulpation not with filling material, but with a medicinal agent (antibacterial, anti-inflammatory). The drug remains in the tooth cavity for a certain time, after which it is removed, and the vacated canal is sealed.

The procedure can be prescribed:

if there is a need to sanitize the canals if a deep infectious process is suspected;
if the patient has acute periodontitis;
for temporary sealing of the canal, if it is necessary to monitor the condition of the tooth cavity after removal of the inflamed pulp.

In addition, the procedure can be prescribed for tooth injuries, for example, a fracture of the crown or root.

Filling root canals with gutta-percha

Gutta-percha is a hard, but at the same time elastic and flexible coagulation product of the latex of tropical gutta-percha plants. Gutta-percha is divided into two types - alpha and beta - which differ greatly in physical properties.

For the production of gutta-percha points, beta-gutta-percha is traditionally used, which has greater hardness and spatial stability and less stickiness. Beta gutta percha requires higher temperatures to soften. However, recently, more fluid and sticky alpha gutta-percha has become increasingly popular, providing, when used in a heated state, a more homogeneous filling of the entire branched root canal system.

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 to produce 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 production of gutta-percha points is mainly concentrated in Southeast Asia. One of the largest suppliers of gutta-percha is Korea. However, recently gutta-percha points have begun to be produced in Brazil.

Pins are divided into standard pins, which have a 2% taper and ISO sizes from 10 to 140, and tapered pins, which have a 2% to 12% taper and sizes from 20 to 30.

Gutta-percha points are made either manually (“hand-rolled”) or by machine. It is believed that the manual method provides higher precision in making pins. Machine-made pins often do not guarantee accurate calibration. It should be especially noted that all pins made in Brazil are machine-made.

The commercial name “gutta-percha pins” has taken root well and is used everywhere, although the content of gutta-percha itself in these pins is about 20%. The main component of the pins (60-70%) is zinc oxide. The remaining 10% consists of barium sulfate, wax, dyes and other additives.

The main advantage of gutta-percha is the predictability of root canal obturation. Its advantages also include good biocompatibility and low toxicity, the ability to condense, ensuring 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 hardened state it practically does not change its volume) and ease of its removal from the root canal if re-treatment is necessary.

Despite all the obvious advantages, gutta-percha also has a number of disadvantages associated with the peculiarities of its physical and chemical properties and the technology of application. The disadvantages of gutta-percha are as follows: 1. It cannot be used without a sealer, since it does not have adhesion to dentin. 2. Gutta-percha does not have a bactericidal or bacteriostatic effect. 3. Thin pins have very high flexibility and softness, which requires high qualifications and experience of the doctor, especially when filling narrow canals, and can also lead to deformation of the pins during their fitting. 4. Thermoplasticized gutta-percha shrinks when cooled. To compensate for this shrinkage, it is necessary to continue the condensation process until it cools.

Types of pastes

One of the most popular drugs is a paste based on antibiotics and corticosteroids. Most often, such a paste contains about 3 antibacterial agents with a wide spectrum of action. Such drugs have a complex effect and significantly accelerate the regeneration of damaged tissues. The paste also contains a radiopaque filler. It is necessary for a visual assessment of the quality of channel filling. This paste has an extremely strong effect with a minimal duration of action. The filling is applied for a period of 3 to 7 days.

An equally popular paste is a material based on metronidazole. The peculiarity of this paste is the effective suppression of pathogenic microflora in the root canals. In addition, the unique properties of the drugs used make it possible to stop the destruction of hard and soft tissues, as well as prevent the occurrence of inflammatory processes. Most often, metronidazole paste is used in case of excessive infection of the canals.

Another type of paste is a preparation based on an antiseptic mixture with a long-lasting effect. This material has an extremely strong effect due to a number of antiseptic components. The paste does not harden, but slowly dissolves, enriching the tissue with healing elements. Most often, this material is used to diagnose pulpitis or periodontitis, as well as in case of problems with baby teeth.

The fourth variety is potassium hydroxide paste. This drug ensures the beginning of a highly alkaline reaction, during which all existing bacteria and other harmful microorganisms are destroyed inside the root canal. For severe forms of periodontitis, non-hardening forms of the material are used, which are placed in a specific canal using a special filler. This paste must be changed every 6-8 weeks. The exact frequency is determined individually by the attending physician.

Note that, regardless of the specific category of pastes, it is extremely rare to completely cure damaged tissue in one session. The patient is assigned several sessions, during which the effectiveness of the current treatment process is diagnosed, as well as the need to apply another filling.

Sealers for root canal obturation

It should be noted that the need to use a sealer is a relative disadvantage, since there is currently no material that can provide predictable filling of the main channel, and at the same time be fluid enough to fill all its branches.

The sealer acts not only as a sealant that fills all branches of the root canal system and ensures adhesion of gutta-percha to the canal walls, but also as a lubricant that ensures free sliding of gutta-percha pins in the root canal.

The sealer must meet the following requirements: 1. After mixing, it must have a sticky consistency in order to ensure good adhesion to the canal walls after curing. 2. Seal the canal hermetically. 3. Be radiopaque. 4. Do not shrink during the curing process. 5. Do not stain tooth tissue. 6. Have a bacteriostatic effect or at least not support the growth of microorganisms. 7. Harden slowly. 8. Do not dissolve in tissue fluids. 9. Do not irritate periapical tissues. 10. Dissolve in standard solvents if it is necessary to unseal the canal. 11. Do not cause immune reactions in periapical tissues. 12. Do not have a mutagenic or carcinogenic effect.

None of the sealers presented on the modern market can meet all the requirements placed on it. Basically, either natural root cements or polymeric materials are used as sealers today. Natural sealers – Endomethasone (Septodont), Cortisomol (Pierre Rolland), Tubli-seal (Kerr), etc. – which are based on zinc oxide, dissolve in tissue fluid, which can lead to disruption of the tightness of the root canal system. In addition, they have low adhesion to dentin and can cause staining of tooth tissue. At the same time, polymer sealers - AH Plus (Dentsply), Adseal (META Biomed), etc. - are less soluble in tissue fluid, do not stain tooth tissue and have better adhesion to root dentin.

Until now, the question to what level to fill the root canal remains open. There is intense debate as to whether gutta-percha should not reach the anatomical apex by 0.5 mm or stop directly at it. Today, the only indisputable fact is that the less we expand the apical narrowing, the better the quality of obturation, the more reliable the isolation of periodontal tissues. In addition, it must be remembered that the theory of active apical therapy has shown its inconsistency. In modern endodontics, removal of sealer beyond the root apex is not encouraged, even in the presence of inflammatory processes in the periodontium, although studies have shown that when a small amount of sealer is removed into the periapical tissue, no serious complications are observed after treatment.

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There are various methods for filling root canals with gutta-percha: the single (central) pin method, lateral condensation, thermomechanical condensation, filling the root canal with chemically softened cold gutta-percha, intracanal hot vertical condensation, thermoplastic injection technique and the use of thermophiles.

Injection (liquid) gutta-percha technique

In this technique, gutta-percha is used in the form of blocks, which are placed in a heating device, in which gutta-percha is heated to a temperature of 185-200°C and fed into the canal in liquid form. alloescort

The liquid gutta-percha technique, when performing the protocol, ensures the penetration of gutta-percha and sealer into both the main root canal and the dentinal tubules . The increase in temperature on the outer surface of the root is insignificant and has minimal damaging effects on the tissue.

The effective use of this technique, however, is determined by the doctor's skills, developed and honed on extracted teeth.

Filling root canals with cold gutta-percha

Single pin method

This method consists in the fact that after appropriate treatment of the canal, which means giving it a taper of 4, 6 or 8%, a sealer is applied to its walls using a paper point. After this, a pre-selected pin with an appropriate taper and tip size is inserted into the canal. The pin should fit snugly against the canal walls. Some authors recommend shortening the tip of the pin by 0.5 mm. Using a heated tool, the pin is cut 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 fill canals with monopaste, but this only ensures filling the lumen of the main canal, and not three-dimensional obturation of the entire root canal system.

Features and stages of unfilling root canals using medication

Chemical deobturation is carried out using one of two methods:

Moderate complexity - performed in one visit and indicated if you need to remove hardening pastes. The latter dissolve well with organic solvents and are easily removed using endodontic instruments. In this case, canal retreatment under a microscope is carried out in one visit to the dentist;
High complexity - indicated if the canals were filled with cement or resorcinol-formalin paste, rarely required when treating patients with old fillings. A dissolving gel is instilled into the canal, and after the filling has softened, a special tool is inserted into it, which allows it to be removed by turning it clockwise and counterclockwise. The dentist must work very carefully so as not to damage the integrity of the canal walls or break the instrument. This type of filling requires two visits to the doctor.

Stages of chemical unsealing:

Removing a surface filling with a dental bur;
Applying solvent to old material;
Careful removal of the filling material after it has softened;
Removal of tissue affected by caries, treatment of other diseases;
Re-filling of canals.

Method of lateral condensation of cold gutta-percha

This scheme involves filling with gutta-percha pins with lateral pressing of each of the pins against the canal walls. For a long time, this technique was the “gold standard” with which all other canal obturation techniques were compared.

After drying the root canal using paper points, its walls are coated with sealer. Then a master pin selected to size is inserted into the canal, the tip of which is moistened in the same sealant. A spreader is then used to condense the master pin against the canal walls, providing sufficient space for the insertion of additional pins. The density of canal obturation depends on the depth of penetration and the shape of the spreader. According to Chohayeb (1993), ISO-standardized hand spreaders should be inserted into the root canal up to 1 mm from the tip of the gutta-percha point, which improves the homogeneity and density of the filling. After the master pin condenses, 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 canal to a shallower depth. Lateral compaction of the pins is carried out until the canal is homogeneously filled, the criterion for which is the impossibility of inserting the spreader into the canal. The recommended time for pressing the pins against the canal walls with a spreader, according to various authors, is 15–30 seconds. After this, the protruding ends of the gutta-percha pins are cut off using a heated instrument, and the mouth of the canal is closed by vertical condensation of gutta-percha.

The quality of root canal obturation during lateral condensation of cold gutta-percha is influenced by many factors. First of all, this is the shape of the processed channel. The root canal must have a uniform taper along its entire length and an apical ledge that prevents material from being removed beyond the apex during condensation. The ratio of gutta-percha to sealer is also of great importance. The following ratio is recommended: 95% gutta-percha, 5% sealer.

Long-term use of the lateral condensation technique of gutta-percha has shown its high clinical effectiveness, ease of use and reliability. Many researchers point to the high filling density of the root canal when performing lateral condensation. However, other authors demonstrate that when performing lateral condensation, there is a risk of longitudinal root fracture due to the forces applied, especially when the root is weakened (for example, when the canals in thin roots are over-expanded). In addition, with this technique it is not possible to achieve homogeneity of the material and filling the lateral and apical branches of the canal with gutta-percha, 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, in order to adequately seal the mouth of the root canal, it is advisable to use a heated instrument to cut off the pins 2-3 mm deeper than the mouth of the canal and fill the remaining part with heated gutta-percha by injecting it.

In order to improve technologies for filling root canals with cold gutta-percha, various techniques have been proposed, which are currently of interest mainly only from the point of view of the history of the development of endodontics. Such techniques include thermomechanical condensation and filling with chemically softened cold gutta-percha.

Filling with chilled gutta-percha

Gutta-percha is a resinous compound obtained from the milky sap of a number of plants and is a high-molecular hydrocarbon similar in composition to natural rubber. There are several methods for sealing root passages using this material:

single pin technique (the treated root course will have a shape identical to the shape of the pin, after which the gutta-percha pin is placed in the prepared hole);
lateral condensation technique (initially the base pin is inserted into the center of the stroke, then the side ones);
sealing using a rotating capacitor;
filling with gutta-percha softened with chemicals.

Thermo-mechanical condensation (or filling root canals with a rotating condenser)

This method is currently practically not used. With this technique, a tool that has in its design elements of an H-file (but with a reverse thread) and a 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 instrument must be rotated clockwise at a speed of at least 8000 rpm.

A standard gutta-percha pin should be 1–2 sizes larger than the last instrument used to process the canal, that is, 1–2 mm shorter than the working length. Control of the level of gutta-percha filling is ensured by inserting the instrument, 1.5 mm short of the apical constriction.

The disadvantages of the method are the unpredictability of the level of filling, the high risk of breaking off the instrument in the canal, and the likelihood of voids forming in the gutta-percha due to its gluing to the instrument. In addition, this technique also does not provide reliable obturation of the lateral branches of the canal.

Preparation for the procedure

Proper preparation is the most important aspect of endodontic treatment. If you do not provide for all possible nuances, the effectiveness of the procedures may be reduced to zero. Before filling directly, it is necessary, first of all, to thoroughly clean the root canal of any plaque that has formed, and also remove all damaged tissue.

In general, all preparatory actions are quite standard. They are carried out in stages and have the following action plan:

carious lesions are eliminated, as well as dead tissue (specialized drills are used for this);
pulp is removed from open canals;
An x-ray is taken to determine the specific shape and length of the canal;
The root canal is expanded to the required size using various attachments and other tools.

Please note that strict adherence to all of the above points is the key to effective treatment. If you neglect at least one of these stages, with a high degree of probability the current situation will only worsen.

Filling root canals with chemically softened cold gutta-percha

Filling techniques using 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. For obturation of gutta-percha softened with solvents (chloroform, some oils), no sealer was used. This led to micro-seepage due to shrinkage of the gutta-percha after the solvent evaporated and the root filling hardened. Therefore, the incidence of complications when using such techniques was very high. Despite the fact that later various sealers began to be used with “immersion” methods, these techniques are currently practically not used due to the inability to control the shrinkage and deformation of gutta-percha and the quality of canal obturation.

What can pain after filling indicate?

In this case, the degree of pain plays a key role. Minor discomfort for several days after the procedure is a completely natural consequence. This happens due to irritation of the tissues and pulp, so there is nothing wrong with it. In addition, the patient may experience a feeling of some swelling inside the tooth, which is also normal.

Another thing is severe pain, which can be accompanied by hemorrhages in the oral cavity. This indicates the presence of a serious error during the filling. In this case, it is necessary to contact a dental clinic as soon as possible for an examination.

In general, to avoid unpleasant consequences, we recommend following the standard rules:

do not expose your teeth to excessively cold temperatures, especially after drinking hot drinks;
maintain oral hygiene;
regularly brush your teeth both at home and in the clinic (professional ultrasonic cleaning, etc.);
undergo routine dental checkups;
do not neglect your doctor's advice.

Following these simple recommendations will help maintain healthy teeth for a long time.