Classification of solid filling materials
Solid filling materials (intracanal points) are an essential part of quality endodontic treatment. Depending on their physical and mechanical properties, they are divided into two main groups:
- Non-plastic points. They have high rigidity and do not change their shape during insertion into the canal. These include:
- Metallic (made of silver or titanium).
- Plastic.
- Fiberglass.
- The specific Thermafil system, which is a rigid metal carrier pre-coated with gutta-percha under factory conditions.
- Plastic points. They are capable of adapting to root canal morphology under pressure or when heated. This group includes:
- Gutta-percha (the most common in modern practice).
- Plastic (certain elastic modifications).
- Fiber.
Visually, a dentist can easily differentiate silver, plastic, titanium, and classical gutta-percha intracanal points by their appearance and density.
Standardization and marking of points
For the convenience of the dentist and to ensure the exact match of the point size to the diameter of the prepared root canal, a strict labeling system is used.
According to the ISO standard: The size range of points includes numbers from 010 to 140. A crucial feature is that the color coding of the main gutta-percha points completely matches the marking of endodontic instruments (files, reamers, etc.). This allows the practitioner to unmistakably select a point of the same size with which the mechanical enlargement of the canal was completed.
Letter marking: Used to designate additional (non-standard) sizes of gutta-percha points that differ in taper and thickness. The following grades are distinguished:
- XXF — extra-extra-fine;
- XF — extra-fine;
- F — fine;
- M — medium;
- L — large.
Material interaction: sealer and filler
There is an immutable rule of endodontics: no point is introduced into the root canal "dry". It must always be accompanied by a paste or cement.
Within the framework of this technique, clear terminology is used:
- Sealer (from English seal) is a seal (paste or cement). Its task is to fill micro-spaces, lateral canals, and ensure reliable adhesion between the tooth wall and the solid material.
- Filler (from English fill) is the point itself (filler). It creates the macro-framework of the filling, ensures its stability and volume, preventing the paste from resorbing over time.
Root canal obturation methods
Before proceeding with obturation, the clinician is required to perform a mandatory step: carry out thorough mechanical and chemical preparation of the root canal, followed by careful drying.
Only after this is one of the obturation methods chosen:
- Obturation with a single paste or cement (e.g., silicate, silicophosphate, or polycarboxylate — historically applied method, but has a number of limitations).
- Single-cone technique (canal obturation with paste combined with only one central filler point).
- Obturation with paste and multiple points. This is the most reliable group of methods, including:
- Cold gutta-percha lateral compaction technique;
- Warm gutta-percha vertical condensation technique.
- Use of pre-heated gutta-percha. The material is heated outside the canal. This includes the Thermafil system, as well as injection systems (e.g., OBTURA II and its analogues).
- Chemical softening. Obturation with gutta-percha that has been pre-softened with special chemical solvents (in dentistry, chloroform, eucalyptol, or halothane are used for this).
Briefly: answers to topical questions
What is the chemical composition of silicate cements?
The chemical composition of silicate cements is represented by a two-component system of powder and liquid. The powder consists of finely ground aluminosilicate glass with the addition of fluoride salts:
- Silicon dioxide (SiO₂) — 29–47%
- Aluminum oxide (Al₂O₃) — 15–35%
- Calcium oxide (CaO) — 0.27–14%
- Fluorine (F) — 5–15%
- Sodium oxide (Na₂O) — 2–9%
- Sodium (Na) — 3–7.5%
- Phosphorus pentoxide (P₂O₅) — 2–7.6%
The liquid is an aqueous solution of phosphoric acid, zinc hydrate, and aluminum:
- Phosphorus pentoxide (P₂O₅) — 38–44%
- Zinc oxide (ZnO) — 2–6%
- Aluminum oxide (Al₂O₃) — 0.5–7%
- Water (H₂O) — 43–55%
What are the indications for the use of polycarboxylate cements?
Polycarboxylate cements are used for placing base liners, luting inlays, artificial crowns, fixed partial dentures up to 3 units, and orthodontic appliances, as well as for temporary delayed fillings.
Main indications:
- Base liners.
- Cementation of restorations — inlays, artificial crowns, fixed partial dentures up to 3 units, and orthodontic appliances.
- Temporary delayed restorations — placed for a period ranging from several months to 1 year.
How do silicophosphate cements differ from silicate cements in their physical and mechanical properties?
Silicophosphate cements have improved physical and mechanical characteristics compared to silicate cements.
| Property | Silicophosphate cements | Silicate cements |
|---|---|---|
| Brittleness | Lower brittleness | Pronounced brittleness and fragility |
| Adhesion | Better adhesion | Weak adhesion to tooth tissues |
| Strength | Mechanical strength | Low compressive strength |
Both materials possess mechanical strength; however, silicate cements easily fracture upon contact with antagonist teeth due to high brittleness, whereas silicophosphate cements demonstrate increased mechanical resistance.
What are the limitations and disadvantages of the root canal filling method using only a single silicate or polycarboxylate cement?
Filling a root canal with a single paste or cement has the following disadvantages:
- Uncontrolled amount of material introduced into the root canal.
- Possibility of voids in the root canal.
- Volumetric shrinkage of the material.
To remember the letter coding of gutta-percha points in ascending order, use the clothing size association: from the smallest XXF (Extra Extra Fine) to the largest L (Large).
Class and exam questions
What is a sealer and filler in endodontics?
A sealer is a sealing paste or cement that fills micro-gaps. A filler is a solid core material, i.e., the intracanal point itself.
What is the Thermafil system?
It is a non-plastic rigid filling material consisting of a carrier metal shaft pre-coated with gutta-percha.
What is used to soften gutta-percha in the chemical filling method?
Solvents are used for the chemical softening of gutta-percha points: chloroform, eucalyptol, or halothane.
What else to study on this topic
- Medication treatment of the root canal
- Root canal drying technique
- Cold lateral compaction technique of gutta-percha
- Warm vertical compaction technique of gutta-percha
- OBTURA II injection system
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