Root canal filling: materials and methods

A variety of modern techniques used for filling developed root canals differ significantly from each other, but are still foreseeable. For obturation of root canals, dentists are provided with a very large selection of materials, but there is no such confusion as when choosing a combination of solutions for root canal irrigation. At this stage of endodontic treatment, there are also no dangerous mutual effects between the materials used.

Gutta-percha

In fact, the most necessary material for filling root canals is undoubtedly gutta-percha, which is used in almost any filling method. This material has the elasticity of rubber and is by its nature a close relative. Gutta-percha is obtained by evaporating the milky juice of special varieties of gutta-percha tree. Gutta-percha was first used for filling root canals in 1867 by Bowman.

ISO-standardized tapered pins contain the following components:

• gutta-percha;
• zinc oxide - as a filler;
• barium sulfate - for radiopacity;
• waxes - to obtain the required consistency;
• dyes and small amounts of trace elements (Guldener, 1993; Hülsmann, 1993).

Gutta-percha points are most often used in combination with so-called sealers.

Sealers are pastes for filling root canals, which are mixed from two components and serve to fill the gap between the canal wall and the gutta-percha pin/pins. Sealers also fill small branches of the root canal and lateral tubules.

There are two options for applying paste to fill the canal:

• first, using a canal filler (lentulo), the sealer is introduced into the canal, and then a gutta-percha pin is inserted, and the sealer is pushed towards the canal walls;
• The gutta-percha point is coated with a small amount of sealer and then inserted into the canal, thereby pushing the sealer into the canal.

This is the “standard concept” of root canal filling, which has been used by dentists in everyday practice for many decades. Sealers are pastes for filling root canals, which are mixed from two components and serve to fill the gap between the canal wall and the gutta-percha pin.

In his dental clinic, the author also uses this effective and efficient method of filling root canals as part of the services covered by public health insurance: the sealer is inserted into the root canal on one (central) gutta-percha pin. The author has been using AH Plus material as a sealer for 7 years. This method of filling root canals is called the method of one (central) pin, or monopin. Currently, this method is most often used for endodontic treatment as part of services covered by public health insurance.

This method has some significant advantages: a ready-made conical gutta-percha pin, due to pressure, moves the sealer paste, previously introduced into the root canal (or introduced simultaneously with the pin), to the canal walls and distributes it over their entire surface. Most often, due to the pressure of the gutta-percha pin, the sealer paste also penetrates into the areas of the apical branches of the root canal. In many cases, at the root apex there is a branching of the main root canal, resembling a river delta.

However, in principle, as a result of mechanical treatment of the root canal, according to all the rules, only the main axial central root canal is developed. Most often, at the moment when a gutta-percha pin is inserted into the root canal, additional (lateral) tubules that are completely inaccessible for mechanical treatment are also filled with filling material, since the excess applied sealer under pressure inevitably penetrates laterally and apically (!), i.e. into in all possible directions.

However, this often leads to unwanted removal of the sealer paste beyond the physiological or even anatomical apical foramen. The question of the negative impact of this phenomenon remains controversial. For example, in Germany, the removal of filling material beyond the apical foramen is an indicator of insufficiently high-quality treatment, and American colleagues believe that it is the (insignificant) removal of filling material beyond the apical foramen that serves as a sign of a particularly successful root canal filling (puff).

As with many aspects of practical endodontics, unfortunately, there is no evidence-based medicine yet on the issue of the acceptable level of root canal filling. All conclusions are made purely empirically. A good confirmation of this is the way dentists treat the removal of filling material beyond the apical foramen.

Of course, whether negative consequences will be observed when the material is removed beyond the apical foramen depends on what material was used to fill the root canals and to what extent it was removed beyond the apex. Thus, slight removal of a biologically inert sealer beyond the apical foramen when used correctly is most likely safe. In Germany, removal of filling material beyond the apical foramen is an indicator of insufficiently high-quality treatment. But the removal in a larger volume beyond the apex of a non-resorbable filling material with supposed cytotoxic properties (for example, the previously frequently used material Diaket, Seefeld) most likely poses a danger. In this case, if there is a significant amount of material removed beyond the apex, it is subsequently necessary to perform an operation of resection of the root apex. It all depends on the situation in a particular clinical case, i.e., it should be taken into account whether the material removed beyond the apex has an irritating effect on the periapical tissues.

There are completely new methods of filling root canals, which use ONLY heated gutta-percha (without sealer). When using these methods, gutta-percha softens to such an extent that, without the additional use of a sealer, it can penetrate into all the necessary areas of the root canal. The result is a hermetic root filling with good adaptation to the walls of the root canal.

Such methods (for example, the Thermafil system) are very rational, and therefore can be used as part of “generally available endodontic treatment”. However, the questions about whether it is necessary to abandon the additional use of sealer and whether a sufficiently sealed root filling is obtained without a sealer have not yet been finally clarified. There is also no evidence-based medicine on this important issue.

When briefly listing the current methods of filling root canals using gutta-percha, it is necessary to mention the methods of lateral condensation and vertical condensation (according to Schilder). These labor-intensive methods are used, as a rule, as private medical services and mainly by dentists specializing in the field of endodontics.

The author believes that due to the large investment of time and money, these methods are difficult to use as “standard” within the framework of “generally available endodontic treatment.” However, as a compromise solution, “mixed” methods can be used.

Materials for root fillings

Prices for dental canal filling depend on the chosen procedure method and the consumables used. We, as modern dentistry, use:

• plastic material, gutta-percha, for the main filling of the tooth canal
• and special sealers and pastes to ensure maximum tightness.

Gutta-percha is the most modern material with antibacterial activity. It does not dissolve and does not lose its properties throughout the life of the tooth. The sealer we use (AH plus, Dentsply, USA) is recognized as the “gold standard” for root canal treatment all over the world.

Sealers

Pastes for filling root canals are usually self-hardening. They consist of two mixing components and have different chemical compositions.

The dental materials market offers a large number of sealers of the most varied composition from various competing manufacturers. Below the author provides a list of sealers currently used, and also mentions some materials that are no longer used.

Table No. 1. Sealers currently available on the market and their composition (in alphabetical order).

The list, for example, mentions material N 2 (, Sargenti), containing toxic formaldehyde. Currently, the material is no longer used in Germany. The list also includes the still widely popular material Endomethasone N (Septodont). Currently, the composition of the material has been slightly changed compared to the previously used original Endomethasone material. In the Endomethasone N material, the content of anti-inflammatory drug components (corticoids, diiodothymol) is significantly lower. These components in sealers have been subject to intense criticism for several decades in student textbooks and scientific papers.

Pastes for filling root canals are usually self-hardening. They consist of two mixing components and have different chemical compositions. The list of materials for filling root canals also includes hardening two-component sealers based on polymers (the polyketone-based material Diaket is no longer produced). The dentist has at his disposal various polymer-based sealer systems (AH plus, Sealapex, Apexit, etc.), as well as silicone-based systems (Roeko Seal). Such materials are highly elastic and have a relatively low final hardness. Due to this property, root fillings made from such materials are easily removed during endodontic revision (retreatment).

It is surprising that the nature of the chemical composition of sealers is completely different. There is no evidence-based medicine yet on whether calcium hydroxide (Ca(OH)2) additives are advisable in such materials.

According to the author, the “favorite” material of German dentists in clinics and dental offices is currently AH plus (Dentsply). Many scientific articles are devoted to this material. AH plus consists of two paste-like components mixed in equal parts and is very easy to use. The material replaced the previously widely used sealer AH 26 several years ago. The sealer AH 26 was developed back in 1954 (Schroeder), it released a small amount of formaldehyde (!) (Schäfer, Hickel, 2000). For this reason, the material in its original composition is no longer used.

However, this drug has its advantages and its adherents. Modern material AH 26 supposedly does not contain formaldehyde. And the currently used N2 Endodontic Cement material based on zinc oxide eugenol still (!) contains formaldehyde, but in a “reduced” concentration compared to the previously used similar material.

It is the use of formaldehyde, as well as chlorophenol-camphor-menthol (ChKM) drugs, that is the subject of debate in university circles. All eminent university teachers do not recommend the use of these drugs.

However, at present there is a time of “renaissance” for the Jodoform-Paste material, which contains the drug chlorophenol-camphor-menthol and has long been considered obsolete. According to modern publications, this material is again recommended for use in pediatric dentistry (endodontic treatment of baby teeth).

New materials based on glass ionomers and salicylates with calcium hydroxide additives, as well as MTA (mineral trioxide aggregate) cement, are currently undergoing the test of time in endodontics.

It is noteworthy that there is no single concept regarding the composition of a good “standard” sealer. Each manufacturer offers its own composition options.

There is no single concept regarding the composition of a good sealer. Each manufacturer offers its own option. Rubber-like, highly elastic preparations based on silicones are also advertised and used as materials for filling root canals. For example, the fairly commonly used material Roeko Seal has the property of expanding in volume by approximately 0.2% when cured. This property of the material should ensure a particularly good fit of the root filling to the walls of the root canal.

On the other hand, silicones have the ability to absorb moisture in small quantities. Are root fillings made from silicone-based materials really impervious to bacteria? The author still has serious doubts about this.

Thus, the variety of paste sealers offered for filling root canals is very large. And not only because they are represented on the market by a large number of competing manufacturers, but also due to the diversity of the composition of materials.

Endodontics is still a broad field of experimentation, especially in the field of root canal fillings.

Materials for filling the canals of permanent formed teeth

Modern pediatric dentistry has access to a wide selection of plastic hardening agents for final filling of dental roots, differing in composition and properties. Most often, in the treatment of periodontitis in children and the treatment of other diseases that require canal cleaning, materials based on the following components are used:

• eugenol and zinc oxide;
• polymers and resins (silicone, composite compounds, epoxy resins);
• calcium compounds (hydroxyapatite, calcium hydroxide);
• glass ionomers (cements);

Other obturation methods

A unique method of filling root canals is the so-called Russian Red, which was previously used in the countries of the Eastern Bloc, including in the former GDR. This filling material is a resin-based polymer in nature. Once cured in the channel, the material turns red and becomes incredibly hard. It is very difficult to remove from the root canal during root canal revision (only with the help of aggressive solvents). However, after filling the root canals with this material, a revision has to be carried out quite rarely, since teeth with these old root fillings are most often miraculously completely “cured” without causing complaints. The author cannot give an explanation for this phenomenon.

After Russian Red root canal filling, teeth are miraculously completely “cured.” With other exotic methods of filling root canals, completely different paste-like sealers without gutta-percha are used. Although these methods save time, such root fillings are less airtight. Therefore, such methods are generally not recommended, even within the framework of “generally available endodontic treatment.” There is still no evidence-based medicine for these methods.

At the beginning of the article, two very labor-intensive methods of root canal filling were already mentioned, which differ significantly from each other: lateral condensation (compaction) of gutta-percha using several pins and vertical condensation of heated gutta-percha. These treatment methods, as well as their various modifications/mixed variants, belong to private dental services in the field of endodontics and are outside the scope of public health insurance. Their use requires a lot of time and the purchase of expensive devices, so they can be classified as expensive private dental services, most often provided in dental offices specializing in endodontics, as well as in university clinics.

Lateral condensation (compaction)

With this method, sealer is first introduced into the root canal using an instrument, or the main (first) gutta-percha pin (Master Point) is wrapped in sealer and inserted into the root canal. Then, additional gutta-percha pins of a smaller ISO size (usually ISO size 25) are inserted next to the central main pin. To provide space for additional tapered pins, a special compaction tool (spreader) is used. The spreader is introduced into the root canal with some pressure and pushes the filling material already present in the canal to the opposite walls, and then removed from the root canal. After this, another additional gutta-percha pin is inserted into the root canal.

With this method, five, six or even more additional gutta-percha points can be inserted into the root canal. After completing the procedure for inserting the pins, before cutting off their protruding ends, such a root filling looks from the outside like a “bouquet” of flower stems without leaves.

The advantage of using this method is the ability to select pins of different sizes for the root filling consisting of several parts of the “gutta-percha core” and individually fit them in the root canal. In this way, it is possible to obtain a reliable and hermetic root filling, with a tight marginal seal, even in areas of the root canal that do not have a round cross-section.

In practice, the dentist almost never encounters the round cross-section of the canal, and the lateral condensation method is considered the “gold standard” for filling root canals. The actual clinical situation often looks very different from the idealized phantom root canal filling on plexiglass blocks that is taught in endodontic workshops. In practice, a dentist is faced with any shape of the canal cross-section, but not a round one. It is precisely because of this discrepancy between theory and practice that in some textbooks, including modern ones, the lateral condensation method is considered the “gold standard” for filling root canals, if we do not take into account another method (vertical condensation), which will be presented in the final parts of the article.

When carrying out endodontic treatment within the framework of public health insurance, a mixed method of filling root canals can be used: at least one very wide root canal or a canal with an oval cross-section is filled with several gutta-percha points using the labor-intensive lateral condensation technique, and narrower root canals with only one central pin in combination with sealer. The author has been using this “mixed” method for several decades.

Methods for filling root canals

There are several basic techniques used in the treatment of pulpitis and periodontitis:

• One-paste method
  The channel is filled with a plastic, subsequently hardening material. The method is outdated and gives a large number of complications.
• Single pin method
  First, the root canal is filled with a special paste, and then a gutta-percha pin is inserted into it. The percentage of complications is lower, but this method is also gradually being phased out.
• Filling with “thermophile”
  A more modern method, also based on the use of an initially plastic material - heated gutta-percha. The fluid state allows the material to densely fill all cavities inside the canal, which significantly reduces the risk of complications. The disadvantages of the method include high requirements for the doctor’s qualifications and relatively high cost.
• Gutta-percha condensation method
  This method ensures even more dense filling of the canal lumen with filling material. Currently, the method is one of the most common. The procedure is performed in several stages.

Vertical condensation

This very labor-intensive method of filling root canals is based on the use of hot (heated) gutta-percha. First, the apical part of the root canal is filled with heated and largely softened or almost liquid gutta-percha, and then compacted by machine (condensed).

This part of the vertically condensed gutta-percha root filling is called Downpack according to the English terminology currently used in Germany.

For compaction, heated instruments are used to keep the gutta-percha in a softened state until it is completely compacted. To condense gutta-percha, among many other systems, rotating instruments are used, which, due to the release of heat during friction, help to soften part of the Downpack root filling.

The part of a root filling made of vertically condensed gutta-percha is called a Downpack according to the English terminology currently used in Germany. The root canal filling technique, first described by Schilder in 1967, is very labor-intensive because it requires special devices for heating and condensing gutta-percha. In addition, tapered Master Points are required, which must exactly match the taper and volume of the root canal or the last instrument used to develop the root canal. Then, before inserting into the root canal, the gutta-percha pins are shortened at the apex by 0.5-1 mm so that if there is significant compaction (condensation) in the canal, the material is not removed beyond the apical opening.

In addition, according to the Schilder technique, the Master Point is first fitted into the root canal, after which a control radiograph is taken, which verifies the correct seating of the pin in the canal. Only after this is its final condensation in the root canal.

After filling the apical third, the middle and upper parts of the root canal (Backfill) are also filled with heated gutta-percha, which is injected directly into the canal using a syringe. To do this, gutta-percha is preheated in a special device (oven) to a liquid state. This labor-intensive method results in root fillings that adhere very well to the walls of the root canal.

Due to their almost perfect tightness, such seals effectively prevent the penetration of bacteria into it.

This is what the technique of vertical condensation of gutta-percha looks like in general. However, there are various modifications of Schilder's original method. Some dentists create a new “ideology” from every new little thing they come up with and do not allow the slightest deviation from “their” concept. The choice of one or another method of canal filling depends to a certain extent on the beliefs of the dentist.

Dental manufacturing companies have been very successful in making money from endless variations of the vertical condensation method, selling pluggers and ovens for preheating gutta-percha, as well as “special gutta-percha.”

How is canal filling done with paste?

Proper filling of root canals promotes a speedy recovery without any complications. To do this, it is necessary to use proven and high-quality drugs, as well as sterilized dental instruments. Only a highly qualified doctor can perform the procedure correctly, so we recommend contacting only reputable dental clinics.

Filling is performed in stages with a clear sequence of actions:

• All affected tissue is removed. In some cases, the practice is used to remove healthy tissue in order to gain unhindered access to each section of the canal.
• Pulp extraction.
• Channel length analysis. Note that the length of the canals varies; the root and its bends play a special role in this matter.
• Mechanical processing of channels. The channels are carefully processed along their entire length to create the maximum possible space. If this is neglected, the material will not be able to spread throughout the entire volume of the channel.
• Canal filling with gutta-percha. The last stage of work. Its effectiveness will directly depend on the correct measurement of the channel length, as well as on the quality of the machining.

Injection methods, Ultrafil, Thermafil

Recently, the method of introducing heated (liquid) gutta-percha using special syringe systems directly into the canal (Obtura system) has also begun to be used. In this case, gutta-percha, heated to a temperature of 160-200 ° C (!), is introduced directly into the root canal using a special injection needle (cannula) of sizes 40 and 60 according to ISO standards.

With this method of canal filling, there is no need to use a sealer. However, the high temperatures used can, in direct contact with tissues, lead to burn damage to surrounding tissues (at the root apex?).

The dentist also has some other systems at his disposal, in which only slightly heated gutta-percha is used, rather than heated to a molten state (Ultrafil, Thermafil). With this method of application, gutta-percha softens a little, after which it is very easy to apply it to those parts of the root canal of the tooth that are not round in cross section.

Thermafil and Thermafil-Plus systems are widely used. This method uses plastic pins coated with gutta-percha. Pin sizes are standardized according to ISO standards. Such a pin is heated for a short time in a small electric oven and, during a short plastic phase, the heated gutta-percha is inserted into the root canal. The protruding excess pin is cut off. But even with this method, accidental pushing of heated gutta-percha into the apical region is possible.

The method of filling root canals using the Thermafil system is quite economical, therefore, in some dental offices aimed at a certain social contingent, patients do not need to pay an additional amount: the treatment is carried out within the framework of state health insurance.

Charging additional fees for endodontic treatment as part of “cash” services from patients insured by public health insurance funds can sometimes be quite problematic. So, unfortunately, the question once again arises: are innovations like the Thermafil system applicable in everyday dental care, if this is associated with even minor additional costs?

The “Central Pin Technique” and Thermafil or Ultrafil systems are economical, effective and realistically applicable in the provision of services within the framework of public health insurance. A dental office that primarily serves patients under public health insurance is faced with a difficult dilemma. And in such a situation, it is the Thermafil system that could find its application within the framework of “generally available endodontic treatment”. However, the question of whether with this method it is necessary to additionally use sealers or whether heated gutta-percha ensures sufficient tightness of the root filling is still being discussed. Saving time does not always benefit the patient.

In dental offices, mainly serving patients under public health insurance, the most often used, described in detail at the beginning of the article, is the very economical “central pin method” in combination with two-component paste sealers.

The author came to these conclusions after numerous discussions on this issue with colleagues during numerous master classes and meetings of quality control groups.

As mentioned above, this standard method of root canal obturation, if necessary, can be easily modified by using additional gutta-percha pins of the “lateral condensation” type, for example in the distal root canals of molars that are very wide or do not have a round cross-section, as well as for filling “large caliber” root canals in incisors and canines.

The author successfully uses the central pin method, as well as the method of “partial” lateral condensation, in his practice and has obtained good treatment results when filling root canals within the framework of state health insurance services (more than 4000 root fillings).

The author uses AH Plus sealer to fill root canals. The only question that remains is which of the many described methods can be considered standard for endodontic treatment within the framework of public health insurance.

The author is convinced that such a method could be the “central pin technique” in combination with a two-component sealer (containing calcium hydroxide), as well as the use of Thermafil or Ultrafil systems. These methods are economical, effective and therefore really applicable in the provision of services within the framework of public health insurance.

This topic should be discussed in professional circles in order to resolve the question of how endodontic treatment can be included in the list of services provided under public health insurance. And it is possible that, based on methods confirmed by evidence-based medicine, such endodontic treatment can be carried out at a much higher quality level. This is certainly doable.

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.

You just have to want it

For specialists in this case, the field of activity remains endodontic treatment in particularly complex root canal anatomy, as well as in particularly complex clinical situations, and for “particularly gifted” specialists - perhaps complex cases of root canal revision.

There is enough work for everyone. In any case, this would benefit “general-profile” therapeutic dentistry.

The article was provided by the magazine of the official publication of the Association of Dentists of Lower Saxony (Germany) NZB - Niedersächsisches Zahnärzteblatt (No. 6, 2011, pp. 31-34).

Translation by Inna Bichegkueva.

Requirements for modern materials for permanent obturation

Today, mostly solid fillers (gutta-percha) and sealers are used to seal root canals in children. Various plastic compositions in the form of pastes and cements are also actively used. The following requirements apply to all materials:

• good adhesion to the canal walls;
• ease of insertion into the dental cavity;
• high level of sealing;
• spatial stability;
• no shrinkage during hardening;
• resistance to bacteria;
• insolubility in biological fluids;
• tolerance to surrounding tissues;
• hypoallergenic and minimal risk of rejection by the body;
• lack of ability to mutate;
• good contrast on the x-ray.