Glass ionomer cements in dentistry (filling materials based on GIC)

Glass ionomer (glass-polyalkenate) cements (GIC) are modern filling materials with a heterogeneous structure, in of which the filler is aluminosilicate glass (Al2 (SiO3) 3), and the role of the polymer matrix is ​​played by the polyacrylic acid.

JRCs are widely used in dentistry as insulating liners, restorative materials and materials of choice for placement of seals in temporary teeth.

Detailed characteristics

Glass ionomer cement is a mixture of a filler represented by fluoroaluminosilicate glass and a polymer framework made of polyacrylic, polyitaconic and polymaleic acids. The liquid can also contain a catalytic system: tartaric acid, camphorquinone (initiates curing under UV rays) and hydroxyethyl methacrylate.

Powder components in various combinations determine the properties of glass-polyalkenate cements:

• quartz (SiO2) adds transparency, reduces the strength of the cured material, prolongs the working time;
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• aluminum oxide (Al2O3) reduces the time for working with the material, adds opacity, resistance in contact with acids and strength;
• calcium fluoride (CaF2) adds opacity, strength, caries-static properties to JRC;
• aluminum phosphate (AlPO3) increases the opacity, strength of the cement and serves as a stabilizer for its structure;
• barium salts and metal impurities added for radiopacity.

Curing takes place in stages:

1. Dissolution (ionization) - the reaction of polyacids with the surface of the filler particles and the formation of Ca2 + and Al3 + ions.
2. Hardening (or primary gelation) - binding of polyacid monomers to each other by means of Ca2 + and Al3 + ions. An increase in pH and the formation of a gel from chains of polymeric acids are characteristic. Duration is 3-6 minutes.
3. Final hardening - the formation of stable bonds of aluminum polyalkenoate and fluorine, which holds the longitudinal polymer chains with cross bonds. Lasts up to a day (24 hours).

An important property of GIC is their ability to chemically adhere to tooth tissues. This is possible due to the establishment of chelating bonds between the carboxyl groups of the polymer (-COO-) and ions Calcium (Ca2 +), which are part of enamel hydroxyapatite and calcium salts of dentin (CaCO3, CaF2, Ca2 (PO4) 3).

Also JRC is able to form bonds with stainless steel, alloys of gold and platinum, composite materials, materials containing Eugenol. The strength of adhesion of GIC is 2-7 MPa. Speaking about the strength of adhesion, it should be understood that it is insufficient to withstand the chewing load in full, but it provides good marginal adhesion of the filling.

Advantages and disadvantages

Advantages of glass ionomers:

1. Ease of use. Most of the JRC is introduced into the tooth cavity in 1-2 portions. Most of these cements do not require pre-pickling and bondingenamels and dentin.
2. Curing ability in a humid environment. This property allows the active use of cements for filling cervical carious cavities, wedge-shaped defects, caries below the level of the gums.
3. The presence of intermolecular bonds of cement with enamel or dentin. Allows to create fillings with good marginal adhesion, and also does not require the creation of retention areas during filling.
4. Adhesion to materials with clove oil. In such a case, JRC can be used as insulating liners, since eugenol interferes with the adhesion of composites to tissues.
5. Adhesion to metals. Contacted with them, JRCs give good results when used as luting material.
6. "Battery effect". Evidence that glass ionomers release fluoride ions into the tooth tissue for at least a year from the time of filling.
7. Low polymerization shrinkage. During hardening, cements adsorb water from the oral fluid, which leads to some an increase in its volume and compensates for the shrinkage, which in light-cured composite materials on 40% higher.
8. Inertness in relation to the pulp and the absence of irritating effect on it. GIC promote the formation of tertiary dentin, and also do not require dentin etching with phosphoric acid, and have a non-aggressive composition. All this allows them to be used as a gasket for filling. deep caries using the sandwich technique.
9. Thermal expansion coefficient is identical to tooth tissues. This ensures a strong marginal adhesion of the fillings, and also prevents chipping of the enamel and dentin margins due to thermal expansion of the filling.

Disadvantages are mainly inherent in the "classic" JRC:

1. Long maturation of the cement mass - the cement is finally cured after 24 hours, although the initial cross-linking occurs after 3-5 minutes.
2. The first day after filling, the material is sensitive to high humidity (ions are washed out) or its lack (the processes of ion formation in the cement mass are disrupted and polymerization occurs longer).
3. The structure can be disturbed by vibration. Therefore, such fillings should not be processed with burs immediately after placement.
4. Do not etch tooth tissues (phosphoric acid prolongs the maturation period of the cement mass).
5. With deep caries, the use of JRC is possible only with the use of medical pads, otherwise the material will adsorb liquid from odontoblasts into pulp.
6. Low strength to diametrical stretching, which leads to the impossibility of using cements for filling cavities on occlusal surfaces and in a situation where the chewing load is distributed over the surface of the filling in different directions.
7. Rapid abrasion of JRC fillings in comparison with fillings from composites.
8. Lack of aesthetics.

Classification of materials

The following categories of glass ionomers are distinguished:

1. "Classic" (powder / liquid system) for luting work (cementation fixed dentures).
2. Aesthetic high in silicon dioxide. It is used for filling wedge-shaped defects, caries of the roots of anterior teeth, cavities of class 3 and 5 (Black).
3. "Reinforced" contain fibers, metals, acid and moisture resistant. Used for small cavities of the 1st class, filling of milk teeth, temporary fillings, usage sandwich techniquesfilling the roots of the distal group of teeth.
4. Lining for laying under amalgam and composite.
5. Aqua cements (polycarboxylic acids are present in a lyophilized state in powder, and the liquid is distilled water).
6. Hybriddual-curing cements (contain a light polymerization activator - camphorquinone. After photoinitiation, a strong framework is formed, and the final hardening occurs after 24 hours).
7. Triple-Cure Hybrid Cements (Vitremer, VOCO). Here there is a reaction of light curing, chemical (thanks to mycocapsules with a patented catalyst system, which are destroyed when the material is mixed) and the classical polymerization reaction JRC.
8. One-component glass polyalkenates in the form of pastes, modified with resins of composite materials (BisGMA, TegGMA, etc.)

Basic principles of work

"Classic" GIC and aqua-cements are used according to the following technology:

• treat the tooth cavity with conditioner, hold it for 20 seconds, rinse, dry;
• carefully isolate the tooth from moisture while the filling is curing (up to 6 minutes);
• mix powder and liquid for 30-40 seconds to obtain a glossy homogeneous mass;
• add cement to the tooth cavity, and simulate the filling, condensing it tightly with a damp cotton ball or corkscrew with a spherical working part;
• varnish the finished filling and process with burs the next day.

Dual-curing GIC (paste-paste type):

• etch the enamel with phosphoric acid, dry and isolate the tooth from moisture, apply adhesive and polymerize it according to the instructions;
• mix two pastes from a tube according to the proportion recommended by the manufacturer;
• dry the tooth cavity, carefully isolate it from moisture;
• introduce the material into the cavity, condensing it well, in a thin layer (up to 1.5 mm) and light with a photopolymerizer for the time specified in the instructions;
• repeat the previous point 2-3 times until the required filling volume is reached;
• process the filling with burs and rubber bands.

Triple-curing JIC:

• etch the tooth tissue with phosphoric acid, rinse it off and dry the cavity;
• isolate the working area from the oral fluid;
• inflict adhesive system according to the instructions using a microbrush;
• blow through the cavity, illuminate bond;
• mix the powder and liquid, add the material into the cavity in one portion, condensing it tightly;
• to grind and polish the fillings.

One-component cements modified with composite resins:

• etch tissue with phosphoric acid for 40 seconds on enamel and 20 seconds on dentin;
• wash off the etching gel, isolate the tooth from the oral fluid, dry the cavity;
• apply a bond with a microbrush, blow through the tooth cavity, illuminate it with a photopolymerizer;
• apply the material according to the instructions for it, rubbing it tightly against the walls of the tooth;
• light up each layer for the time specified in the instructions;
• to grind and polish the fillings.

TOP 10 glass ionomers used in dentistry

TOP 10 best JRC:

1. Vitremer, VOCO Is the only cement with a triple-curing mechanism. Has high aesthetics, easy to use (does not require layer-by-layer application). It is used for fixing structures in orthopedic dentistry, restorations.
2. Ionosit Baseliner - used for sandwich technology, as an insulating gasket. Three times stronger than traditional JRC.
3. Ionoseal - light-curing material with increased strength. Binds well to composites.
4. Core Max - high-strength material, reinforced with composite resins. Used to restore the crown under pin.
5. RelyX LUTING - photopolymerizable hybrid material, used for luting work.
6. Fudji plus - composite modified cement. Provides a strong fixation of metal-ceramic, metal-free, metal structures used in orthopedic dentistry.
7. Fudji IX - "packable" glass-polyalkenate cement with high abrasion resistance. Refers to "classic" cements. Suitable for filling Class 1 cavities and restoring the crown of the tooth.
8. Fudji lining - light-curing material with low shrinkage. Used as an insulating liner.
9. Fudji l - classic SIC for luting work (fixation of orthopedic structures).
10. TimeLine - photopolymerizable glass ionomer. Used as a liner for composites in restorations.

Useful information

It should be remembered that:

• when using JRC for amalgam, the thickness of the gasket must be at least 1 mm;
• the optimal period for cementation of pins and orthopedic structures is the stage of "stretching threads", when, when the spatula is torn off, the cement forms stringy threads (like chewing gum);
• when working with "classic" JRC, it is important that the tissue moisture is optimal, for this it is dried until the dentin takes the form of wet sand ("sparkling" dentin);
• hybrid cements require tissue etching and adhesive systems;
• preparation of the cavity for the introduction of "classic" GIC - using the conditioner (solution with monomer) according to the instructions.

Glass ionomer cement - the material of choice when placing fillings in case of multiple caries, decay of deciduous teeth and with unsatisfactory oral hygienesince these materials emit fluoride, which prevents the development of the carious process.

JRC fillings are not as strong or aesthetic as composite fillings and are not abrasion resistant, so they are not suitable for restoring the occlusal surface or the incisal edge of the tooth. But they provide good marginal adhesion, almost no shrinkage, and are non-toxic.

Also, when installing glass ionomer fillings, you should not worry that the filling can crumble the thin walls of the tooth under the influence of hot food. Therefore, although composites are ahead of GIC in some characteristics, glass-polyalkenate cements confidently occupy its niche among materials for luting work, filling of deciduous teeth, caries of the roots of teeth and insulating liners.