Calcium- element of the 4th period and PA group Periodic table, serial number 20. Electronic formula of the atom [ 18 Ar]4s 2, oxidation states +2 and 0. Refers to alkaline earth metals. It has low electronegativity (1.04) and exhibits metallic (basic) properties. Forms (as a cation) numerous salts and binary compounds. Many calcium salts are slightly soluble in water. In nature - sixth By chemical abundance element (third among metals), is in a bound form. A vital element for all organisms. The lack of calcium in the soil is compensated by applying lime fertilizers (CaC0 3, CaO, calcium cyanamide CaCN 2, etc.). Calcium, calcium cation and its compounds color the flame of a gas burner dark orange ( qualitative detection).
Calcium Ca
Silvery-white metal, soft, ductile. In humid air it fades and becomes covered with a film of CaO and Ca(OH) 2. Very reactive; ignites when heated in air, reacts with hydrogen, chlorine, sulfur and graphite:
Reduces other metals from their oxides (an industrially important method - calciumthermia):
Receipt calcium in industry:
Calcium is used to remove non-metal impurities from metal alloys, as a component of light and anti-friction alloys, to isolate rare metals from their oxides.
Calcium oxide CaO
Basic oxide. Technical name quicklime. White, very hygroscopic. It has ionic structure Ca 2+ O 2- . Refractory, thermally stable, volatile when ignited. Absorbs moisture and carbon dioxide from the air. Reacts vigorously with water (with high exo- effect), forms a strong alkaline solution(hydroxide precipitate is possible), the process is called lime slaking. Reacts with acids, metal and non-metal oxides. It is used for the synthesis of other calcium compounds, in the production of Ca(OH) 2, CaC 2 and mineral fertilizers, as a flux in metallurgy, a catalyst in organic synthesis, a component of binding materials in construction.
Equations of the most important reactions:
Receipt Sao in industry— limestone firing (900-1200 °C):
CaCO3 = CaO + CO2
Calcium hydroxide Ca(OH) 2
Basic hydroxide. Technical name is slaked lime. White, hygroscopic. It has an ionic structure: Ca 2+ (OH -) 2. Decomposes when heated moderately. Absorbs moisture and carbon dioxide from the air. Slightly soluble in cold water (an alkaline solution is formed), and even less soluble in boiling water. Transparent solution ( lime water) quickly becomes cloudy due to the precipitation of hydroxide sediment (the suspension is called milk of lime). A qualitative reaction to the Ca 2+ ion is the passage of carbon dioxide through lime water with the appearance of a CaCO 3 precipitate and its transition into solution. Reacts with acids and acid oxides, enters into ion exchange reactions. Used in the production of glass, bleaching lime, lime mineral fertilizers, for causticizing soda and softening fresh water, as well as for the preparation of lime mortars - dough-like mixtures (sand + slaked lime + water), serving as a binding material for stone and brickwork, finishing (plastering) walls and other construction purposes. The hardening (“setting”) of such solutions is due to the absorption of carbon dioxide from the air.
1. Calcium hydroxide (slaked lime) is a slightly soluble substance. Shake a little lime in 2 ml of water (about 2 cm in height of the test tube), let it stand for a few minutes. Most of the lime will not dissolve and will settle to the bottom.
2. Drain the solution, filter (if there is no filter, wait until it settles). A clear solution of calcium hydroxide is called lime water
. Divide into 2 test tubes. We drop phenolphthalein indicator (ph) into one, it turns crimson, which proves the main properties of lime:
Ca(OH) 2 Ca 2+ + 2OH -
3. We pass carbon dioxide into the second test tube; lime water becomes cloudy as a result of the formation of insoluble calcium carbonate (this is a qualitative reaction for detecting carbon dioxide):
Ca(OH) 2 + CO 2 = CaCO 3 ↓ + H 2 O
If you have to do these reactions in practice, carbon dioxide can be obtained in a test tube with a gas outlet tube by adding hydrochloric or nitric acid to chalk or soda.
You can pass the exhaled air several times through a cocktail or juice straw that you brought with you. You shouldn’t shock the commission by blowing into a tube from laboratory equipment—you can’t taste anything in the chemistry lab!
Ticket number 17
1. Oxides: their classification and chemical properties (interaction with water, acids and alkalis).
Oxides – complex substances, consisting of two elements, one of which is oxygen.
Oxides are divided into acidic, basic, amphoteric and non-salt-forming (indifferent).
Acidic oxides correspond to acids. Acidic properties possess most non-metal oxides and metal oxides in highest degree oxidation, for example CrO 3.
Many acidic oxides react with water to form acids. For example, sulfur (IV) oxide, or sulfur dioxide, reacts with water to form sulfuric acid:
SO 2 + H 2 O = H 2 SO 3
Acidic oxides react with alkalis to form salt and water. For example, carbon monoxide (IV), or carbon dioxide, reacts with sodium hydroxide to form sodium carbonate (soda):
CO 2 + 2NaOH = Na 2 CO 3 + H 2 O
Main Bases correspond to oxides. The main ones include alkali metal oxides ( main subgroup Group I),
magnesium and alkaline earth (main subgroup of group II, starting with calcium), metal oxides of secondary subgroups in the lowest oxidation state (+1+2).
Alkaline and alkaline earth metals react with water to form bases. So, calcium oxide reacts with water to produce calcium hydroxide:
CaO + H 2 O = Ca(OH) 2
Basic oxides react with acids to form salt and water. Calcium oxide reacts with hydrochloric acid to produce calcium chloride:
CaO + 2HCl = CaCl 2 + H 2 O
Amphoteric oxides react with both acids and alkalis. Thus, zinc oxide reacts with hydrochloric acid to produce zinc chloride:
ZnO + 2HCl = ZnCl 2 + H 2 O
Zinc oxide also reacts with sodium hydroxide to form sodium zincate:
ZnO + 2NaOH = Na 2 ZnO 2 + H 2 O
Amphoteric oxides do not interact with water. Therefore, the oxide film of zinc and aluminum protects these metals from corrosion.
— inorganic compound, calcium alkali. Its formula is Ca(OH) 2. Since this substance has been known to mankind since ancient times, it has traditional names: slaked lime, lime water, lime milk, fluff.
Fluff is a finely ground powder. Lime milk is an aqueous suspension of alkali, an opaque white liquid. Lime water is a clear aqueous solution of alkali obtained after filtering lime milk.
Slaked lime is named after its production method: quicklime (calcium oxide) is poured with water (quenched).
Properties
Fine crystalline powder, white, odorless. Very poorly soluble in water, insoluble in alcohol, easily soluble in dilute nitrogen and hydrochloric acids. Fireproof and even prevents fire. When heated, it decomposes into water and calcium oxide.
Strong alkali. It enters into neutralization reactions with acids to form salts - carbonates. When interacting with metals, explosive and flammable hydrogen is released. Reacts with carbon oxides (IV) and (II), with salts.
The reaction of producing calcium hydroxide by the “quenching” method occurs with a large release of heat, the water begins to boil, caustic solution splashes into different sides- this must be taken into account when working.
Precautionary measures
Contact of dry powder particles or drops of calcium hydroxide solution on the skin causes irritation, itching, chemical burns, ulcers, and severe pain. Damage to the eyes can cause vision loss. Ingestion of the substance causes a burn to the mucous membrane of the throat, vomiting, bloody diarrhea, a sharp decrease in pressure, damage internal organs. Inhaling dust particles can cause throat swelling that makes breathing difficult.
Before calling " Ambulance»:
- in case of poisoning, give the victim milk or water to drink;
- if the chemical gets into the eyes or skin, the damaged area must be washed big amount water for at least a quarter of an hour;
- if the reagent is accidentally inhaled, the victim must be removed from the room and provided with access to fresh air.
Work with calcium hydroxide in well-ventilated areas using protective equipment: rubber gloves, safety glasses and respirators. Chemical experiments must be carried out in a fume hood.
Application
— In the construction industry, a chemical reagent is added to binding solutions, plaster, whitewash, and gypsum solutions; based on it, sand-lime bricks and concrete are made; it is used to prepare the soil before laying road surfaces. Whitewashing wooden parts of structures and fences gives them fire-resistant properties and protects them from rotting.
— For neutralization of acid gases in metallurgy.
— For the production of solid oils and oil additives — in the oil refining industry.
- In the chemical industry - for the production of sodium and potassium alkalis, bleach (bleach), calcium stearate, organic acids.
- IN analytical chemistry lime water serves as an indicator of carbon dioxide (by absorbing it, it becomes cloudy).
— Using calcium hydroxide, waste and industrial waters are purified; neutralize the acids of the water entering the water supply systems to reduce its corrosive effects; remove carbonates from water (soften water).
— Using Ca(OH) 2, hair is removed from hides in tanning. 
— Food additive E526 in the food industry: acidity and viscosity regulator, hardener, preservative. It is used in the production of juices and drinks, confectionery and flour products, marinades, salt, and baby food. Used in sugar production.
— In dentistry, lime milk is used to disinfect root canals.
- For the treatment of acid burns - in medicine.
- IN agriculture: means for regulating soil pH; as a natural insecticide against ticks, fleas, and beetles; for the preparation of the popular fungicide “Bordeaux mixture”; for whitewashing tree trunks from pests and sunburn; as an antimicrobial and antifungal drug for storing vegetables in warehouses; as a mineral fertilizer.
— Calcium hydroxide reduces the electrical resistance of the soil, so it is used to treat the soil when installing grounding.
— The chemical reagent is used in the production of hard rubber, brake linings, and hair removal creams.
You can buy slaked lime at a good price, retail and wholesale, with delivery or pickup at the Prime Chemicals Group chemical store.
Ca(OH)2 is calcium hydroxide (from the Latin Calcium hydroxide), it is quite common chemical. It is considered a strong base by its nature. It is a fine powder yellowish color or colorless crystals. Can decompose when heated, resulting in the release of calcium oxide. It is poorly soluble in water. In this case, an aqueous solution of calcium hydroxide is an average base in its chemical properties. In the presence of metals, it can release hydrogen, which is recognized as an explosive gas.
Calcium hydroxide, when entering the body through the mouth or as a result of inhalation of an aerosol, can be absorbed into tissues and accumulate in them. At normal room temperature at 20-22 degrees this substance practically does not evaporate, but when its particles are sprayed, it can be hazardous to health. When it gets on the skin, respiratory tract or mucous membranes of the eyes, calcium hydroxide has an irritating, even corrosive effect. Prolonged contact with skin can cause dermatitis. Lung tissue may also be affected by chronic exposure to calcium hydroxide particles.
This chemical compound has many trivial names, such as (it is obtained by quenching calcium oxide with ordinary water), lime water (it is a clear aqueous solution). Other names: fluff (calcium hydroxide in the form of a dry powder) and milk of lime (a saturated aqueous suspension). Calcium oxide is often also called lime.
Calcium hydroxide, the chemical properties of which are considered aggressive towards other substances, is obtained by slaking lime, that is, as a result of the interaction (chemical reaction) of calcium oxide and water. Schematically, this reaction looks like this:
CaO + H2O = Ca(OH)2
The resulting aqueous solution is characterized by an alkaline reaction of the medium. Like all typical calcium reacts with:
1. inorganic acids with the formation of typical calcium salts
H2SO4 +Ca(OH)2 = CaSO4 + 2H2O
2. carbon dioxide, which is dissolved in water, so the aqueous solution very quickly becomes cloudy in air, and a white insoluble precipitate is formed - calcium carbonate
CO2 + Ca(OH)2 = CaCO3 + H2O
3. carbon monoxide when the temperature rises to 400 degrees Celsius
CO (t°) + Ca(OH)2 = CaCO3 + H2
4. salts, which also results in the formation of a white precipitate - calcium sulfate
Na2SO3 + Ca(OH)2 = CaSO3 + 2NaOH
The use of calcium hydroxide is very popular. Surely, everyone knows that lime is used to treat the walls of premises, tree trunks, and is also used as a component of building lime mortar. The use of calcium hydroxide in construction has been known since ancient times. And now it is included in the composition of plaster, sand-lime brick and concrete are produced from it, the compositions of which are almost the same as mortar. The main difference is in the method of preparing these very solutions.
Calcium hydroxide is used as a softening agent for making lime inorganic fertilizers, causticizing potassium and sodium carbonate. This substance is also indispensable for tanning leather in the textile industry, for obtaining various calcium compounds, as well as for neutralizing acidic solutions, among other things. Organic acids are obtained from it.
Calcium hydroxide has also found its use in Food Industry, where he is better known as food supplement E526, used as an acidity regulator, hardener and thickener. In the sugar industry it is used for desugarification of molasses.
In laboratory and demonstration experiments lime water is an indispensable indicator for the detection of carbon dioxide during chemical reactions. Lime milk is used to treat plants to combat diseases and pests.
L.A. Kazeko, I.N. Fyodorova
Calcium hydroxide: yesterday, today, tomorrow
Calcium hydroxide Ca(OH) 2 - strong foundation, slightly soluble in water. A saturated solution of calcium hydroxide is called lime water and has alkaline reaction. In air, limewater quickly becomes cloudy due to the absorption of carbon dioxide and the formation of insoluble calcium carbonate.
Calcium hydroxide (“slaked lime”) is a white, very fine powder, slightly soluble in water (1.19 g/l), solubility can be increased by glycerin and sucrose. Hydrogen index (pH) is about 12.5. Calcium hydroxide is very sensitive to contact with atmospheric carbon dioxide, which transforms it into calcium carbonate. The drug should be stored in sealed containers away from light; it may be stored in oversaturated conditions. aqueous solution(distilled water) in a sealed bottle.
The basis for the use of calcium hydroxide in endodontics was information about the etiology and pathogenesis of pulpitis and apical periodontitis. The most common cause of these diseases is microorganisms in the root canal system of the tooth. Kakehashi et al. (1965), Moller et al. (1981) showed in experiments that periapical inflammation and destructive processes around the apex of the tooth develop only with the participation of root canal microorganisms. Favorable factors for the existence of microflora are the complex anatomy of the root canals, the ability of bacteria to penetrate into the dentinal tubules to a depth of 300 microns, anaerobic development conditions, the ability to feed from living or necrotic pulp, salivary proteins, and periodontal tissue fluid. Thus, the quality of endodontic treatment is determined by the quality of disinfection of the root canal system.
Endodontic instrument breakage, root perforation, ledges, and overfilling or underfilling are considered to be the main causes of endodontic failure. However, in most cases, these errors do not affect the outcome of endodontic treatment until a concomitant infection occurs. Of course, gross errors prevent or make it impossible to complete intracanal procedures, but the chances of successful treatment increase significantly if the infectious and toxic contents of the root canals are effectively removed before filling.
Microorganisms that survive instrumentation and irrigation quickly multiply and repopulate root canals that remain empty between visits. The likelihood of reinfection depends on the quality of root canal filling and the usefulness of the coronal restoration. However, in all cases where bacteria remain in the root canal system, there is a risk further development peri-apical changes.
In untreated teeth with primary intracanal infection, one or more species of bacteria are usually present, with no apparent predominance of facultative or anaerobic forms. In case of secondary infection if treatment fails, a mixed infection is present, with gram-negative anaerobic strains dominating.
There are differing opinions regarding the necessary number of treatment steps for patients with periapical problems. Thus, some authors justify the need to treat infected root canals in several visits, using temporary intracanal dressings, which allows for the gradual and controlled destruction of microorganisms in them. Others suggest preventing the growth of remaining microorganisms by depriving them of nutrition and living space by fully debridement, disinfection, and 3D filling of the root canals during the first and only visit.
Anti-inflammatory and antibacterial activity of calcium hydroxide
Instrumental treatment of the root canal reduces the number of microorganisms by 100-1000 times, but their complete absence is observed only in 20-30% of cases. Antibacterial irrigation with 0.5% sodium hypochlorite solution increases this effect to 40-60%. It is very difficult in practice to achieve complete disinfection of infected root canals even after complete mechanical cleaning and irrigation with antiseptic solutions. It is possible to destroy bacteria remaining in the root canal by temporarily filling the root canal with antimicrobial agents until the next visit. Such drugs must have wide range antibacterial action, be non-toxic and have physical and chemical properties allowing them to diffuse through the dentinal tubules and lateral canals of the tooth root system.
Calcium hydroxide is widely used as a temporary intracanal agent in endodontics, which decomposes into calcium ions and hydroxide ions in an aqueous solution. Basic biological properties hydroxide: bactericidal activity, anti-inflammatory properties, tissue solubility, hemostatic effect, inhibition of tooth tissue resorption, stimulation of bone regeneration processes.
Calcium hydroxide has bactericidal activity due to its high alkalinity and release in aquatic environment hydroxide ions - highly active free radicals. Their effect on bacterial cells is explained by the following mechanisms:
- damage cytoplasmic membrane bacterial cell, playing important role in cell preservation. It is the cell membrane that provides selective permeability and transport of substances, oxidative phosphorylation in aerobic strains, production of enzymes and transport of molecules for the biosynthesis of DNA, cellular polymers and membrane lipids. Hydroxide ions from calcium hydroxide cause lipid oxidation, which leads to the formation of free lipid radicals and the destruction of phospholipids, which are structural components cell membranes. Lipid radicals initiate chain reaction, resulting in the loss of unsaturated fatty acid And cell membranes are damaged;
- protein denaturation due to the fact that the alkaline environment of calcium hydroxide causes destruction ionic bonds, providing the structure of proteins. IN alkaline environment polypeptide chains of enzymes are chaotically connected and transformed into disordered formations. These changes often lead to loss biological activity enzymes and disruption of cellular metabolism;
- damage to microbial DNA, with which hydroxide ions react, causing its splitting and leading to damage to genes due to disruption of DNA replication. In addition, free radicals can independently cause destructive mutations.
The bactericidal effect of calcium hydroxide depends on the concentration of hydroxide ions, which is high only in the zone direct contact with the drug. When calcium hydroxide diffuses deeper into dentin, the concentration of hydroxide ions decreases due to the action of buffer systems (bicarbonate or phosphate), acids, proteins and CO 2, the antibacterial activity of the drug may be reduced or slowed down. Neutralization of high pH calcium hydroxide can also occur as a result of coronal microleakage, leakage of tissue fluid through the root apex, the presence of necrotic masses in the canal, and the production of acidic substances by microbes. In the root canal the pH is 12-12.5, in the adjacent dentin, where there is close contact with the hydroxide, the pH varies from 8 to 11, and in the depths of the dentin the pH values are 7-9. The highest pH values were obtained in the period from 7 to 14 days after adding an aqueous suspension of calcium hydroxide to the channel.
Microorganisms differ in their resistance to pH changes; most of them reproduce at pH 6-9. Some strains can survive at pH 8-9 and are usually the cause of secondary infection. Enterococci ( E. faecalis), resistant to pH 9-11, are not normally found in root canals or are present in small quantities in untreated teeth. They play an important role in unsuccessful endodontic treatment and are often (32-38% of cases) present in teeth with apical periodontitis.
One of the important components of the effective disinfectant effect of the drug in endodontics is its ability to dissolve and penetrate into the root canal system. Alkalis (NaOH and KOH) are highly soluble and can diffuse deeper than calcium hydroxide. These substances have pronounced antibacterial activity. But high solubility and active diffusion enhance the cytotoxic effect on the cells of the body. Due to their high cytotoxicity, they are not used in endodontics. Calcium hydroxide is biocompatible, since due to its low water solubility and diffusion, a slow increase in pH occurs, which is necessary to destroy bacteria localized in dentinal tubules and other hard-to-reach anatomical formations. Because of these features, calcium hydroxide is an effective but slow-acting antiseptic.
The time required for optimal root canal disinfection with calcium hydroxide has not yet been precisely determined. Clinical researches give conflicting results. Cwikla et al. (1998) found that in 90% of cases there was no bacterial growth after 3 months of hydroxide use. In a study by Bystrom et al. (1999) calcium hydroxide effectively killed microorganisms within 4 weeks of use. Reit and Dahlen used the drug for 2 weeks - infection persisted in 26% of root canals. In an experiment by Basrani et al. After one week of using calcium hydroxide, bacteria remained in the canals in 27% of cases.
Mechanisms of resistance of microorganisms to the action of intracanal disinfectants
Factors that determine the resistance of microorganisms to the action of disinfectants and the ability to survive after the use of intracanal (temporary and permanent) filling materials:
Neutralization of the drug with buffer systems or bacterial cell products;
Insufficient exposure of the disinfectant in the root canal to destroy microorganisms;
Low antibacterial effectiveness of the drug against root canal microorganisms;
The effect of the drug on microorganisms is limited for anatomical reasons;
The ability of microorganisms to change their properties (genes) after a change environment.
An important mechanism of bacterial resistance is their existence in the form of a biofilm. Biofilm is a microbiological population (bacterial ecosystem) associated with an organic or inorganic substrate, surrounded by bacterial waste products. Various strains of microorganisms collected in a biofilm are capable of organizing associations for joint survival, have increased resistance to antimicrobial agents and defense mechanisms. Over 95% of naturally occurring bacteria are found in biofilms.
It is more difficult to destroy bacteria in biofilms than in planktonic suspensions unless the disinfectant has the ability to dissolve tissue. When re-treating infected teeth, calcium hydroxide may not be 100% effective in killing stubborn bacteria ( E. faecalis), which are able to reproduce between visits to the dentist. Of great importance is a complete preparation and cleansing of the canal from all microorganisms on the first visit (using copious rinses with sodium hypochlorite). Prevention of re-infection of the root canal is achieved by completely sealing the tooth crown using high-quality temporary fillings.
Effect of solvents on the antibacterial activity of calcium hydroxide
Substances used as a medium for calcium hydroxide have different water solubility. An optimal environment should not change the pH of calcium hydroxide. Many solvents do not have antibacterial activity, such as distilled water, saline, and glycerin. Phenol derivatives, such as paramonochlorophenol, camphor phenol, have pronounced antibacterial properties and can be used as a hydroxide medium. Calcium hydroxide with paramonochlorophenol has a long range of action and destroys bacteria in areas remote from the places where the paste is applied.
Siqueira et al. found that calcium hydroxide in saline does not destroy E. faecalis And F. nucleatum in the dentinal tubules within a week of use. And calcium hydroxide paste with paramonochlorophenol and glycerin effectively destroyed bacteria in the tubules, including E. faecalis, within 24 hours of use. That is, paramonochlorophenol enhances the antibacterial activity of calcium hydroxide.
The results of a study on the disinfection of dentinal tubules using three preparations of calcium hydroxide (Ca(OH) 2 in distilled water, Ca(OH) 2 with potassium iodide and Ca(OH) 2 with iodoform (Metapex)) showed that Ca(OH) 2 in pure form less effective at killing microbes in dentinal tubules. Growth of some microorganisms has been observed in calcium hydroxide channels ( E. faecalis, C. albicans) to a depth of 250 microns for 7 days. This is explained by the fact that Ca(OH) 2 has a low degree of permeability and its high pH (12) is partially neutralized by dentin buffer systems. Ca(OH) 2 with potassium iodide is more effective than pure hydroxide. But the Metapex paste (Ca(OH) 2 with iodoform) turned out to be the most effective: in addition E. faecalis it neutralized other microbes and penetrated into the tubules to a depth of more than 300 µm (Cwikla et al.).
Abdullah et al. (2005) studied the effectiveness of various intracanal agents (calcium hydroxide, 0.2% chlorhexidine, 17% EDTA, 10% povidone-iodine, 3% sodium hypochlorite) against strains E. faecalis, located in bacterial biofilms. As part of a biofilm E. faecalis in 100% of cases it was destroyed by 3% sodium hypochlorite after 2 minutes and 10% povidone-iodine after 30 minutes. Calcium hydroxide partially eliminated these bacteria.
Since some microorganisms, especially E. faecalis, are resistant to calcium hydroxide, its combination with other antimicrobial agents that increase its activity, for example with idoform, camphor paramonochlorophenol, is justified. Having low surface tension, fat-soluble phenols penetrate deep into the tooth tissue.
In endodontics, chlorhexidine, which is effective against many bacteria that cause endodontic infection, is recommended for widespread use as an irrigant and intracanal dressing. The chlorhexidine molecule, interacting with the phosphate groups of the bacterial cell wall, penetrates the bacterium and has intracellular effects. toxic effect.
Calcium hydroxide in combination with 2% chlorhexidine gel has increased antimicrobial activity, especially against resistant microorganisms. Chlorhexidine in gel form has the following positive properties, as low toxicity for periodontal tissues, viscosity that allows you to retain active substances in constant contact with the walls of the root canal and dentinal tubules, water solubility. The combination of chlorhexidine gel and calcium hydroxide has been found to be highly effective against E. faecalis in infected root dentin. High pH (12.8) in the first two days increases the penetration ability of the drugs.
Effective against E. faecalis after 1, 2, 7 and 15 days of use of 2% chlorhexidine gel. According to Gomes et al., 2% chlorhexidine gel has greater antibacterial activity against E. faecalis than calcium hydroxide, but this ability is lost when used for a long time. This is confirmed by other studies, even when using chlorhexidine in the form of a solution or gel at concentrations of 0.05%, 0.2% and 0.5%. The combination of chlorhexidine and calcium hydroxide inhibits growth by 100%. E. faecalis after 1-2 days of contact.
Calcium hydroxide as a physical barrier
Secondary intracanal infections are caused by microorganisms that enter the canal during treatment, between visits or after dental treatment. The main sources of secondary infection: dental plaque on teeth, caries, infected endodontic instruments. Causes of infection between visits may include microleakage through a temporary filling due to its destruction; tooth fracture; delay in replacing a temporary filling with a permanent one, when the tooth remains open for drainage. Secondary infection allows the emergence of new, virulent microorganisms that cause acute periapical inflammation.
Intracanal preparations destroy bacteria remaining after chemomechanical treatment of the canal, and are also used as a physical and chemical barrier that prevents the proliferation of microorganisms and reduces the risk of reinfection from the oral cavity. Reinfection of the canal is possible due to the fact that the drug is dissolved by saliva, saliva seeps into the space between the medication and the walls of the canal. However, if a drug has an antibacterial effect, it will first be neutralized and only then will bacterial invasion occur.
To prevent reinfection, the sealing ability of calcium hydroxide is more important than its chemical activity, since it has low water solubility, dissolves slowly in saliva, remains in the canal for a long time, delaying the movement of bacteria towards the apex. Despite the use of solvents, calcium hydroxide acts as an effective physical barrier, destroying some of the remaining bacteria and preventing their growth, limiting the space for reproduction.
It is proposed as a reliable isolating barrier for various endodontic problems (perforation of the cavity bottom, tooth root, root resorption, etc.). new class materials - mineral trioxide aggregate (ProRut MTA). The basis of MTA is calcium compounds.
The influence of calcium hydroxide on the quality of permanent root canal filling
Before permanent obturation, calcium hydroxide is removed from the root canal using sodium hypochlorite, saline and endodontic instruments.
Lambrianidis et al. (1999) investigated the possibility of removing certain calcium hydroxide preparations from root canals: Calxyl (42% calcium hydroxide) and an aqueous suspension (95% calcium hydroxide). Percentage calcium hydroxide did not affect the effectiveness of cleaning the walls of the root canal. Paste residues may affect mechanical properties sealer and worsen the apical seal. There is an opinion that it is impossible to completely remove the paste from the walls of the root canal.
Residual calcium hydroxide negatively affects the hardening of zinc oxide eugenol sealers, as it interacts with the eugenol of the paste to form calcium eugenolate. In the clinic, this may manifest itself as blocking the advancement of the gutta-percha pin along the entire working length of the canal. If calcium hydroxide residues are not completely removed, they become compacted apically or in the recesses of the canal, which mechanically interferes with effective canal filling, complicates apical sealing and can affect the outcome of endodontic treatment. It is preferable to remove the apical calcium hydroxide plug.
Calcium hydroxide is effectively removed from the canal walls with hand instruments and rinsing with sodium hypochlorite and 17% EDTA. Difficulties in cleaning root canals after temporary filling are caused by paste-forming substances and fillers, and not calcium hydroxide. Calcium hydroxide preparations water based(especially those preparing ex tempore) are absolutely devoid of these shortcomings. Moreover, calcium hydroxide-based sealers should be considered the materials of choice for permanent obturation of root canals after their temporary filling with calcium hydroxide.
Indications for temporary filling of root canals
The use of non-hardening pastes based on calcium hydroxide is indicated as a temporary intracanal agent for the treatment of acute forms of apical periodontitis, destructive forms of chronic apical periodontitis, cystogranulomas, radicular cysts, progressive root resorption, teeth with an unformed root apex in pediatric practice.
Method of using calcium hydroxide:
1) calcium hydroxide in powder form is mixed to a paste with distilled water or glycerin;
2) the paste is injected into a carefully instrumentally and medicinally treated root canal using a canal filler;
3) to ensure adherence to the root dentin, the paste is compacted with a paper pin and covered with an airtight bandage.
Features of the use of calcium hydroxide for different states apical periodontium. At acute forms of apical periodontitis temporary filling with calcium hydroxide aims to have an anti-inflammatory and antimicrobial effect. Calcium hydroxide is introduced into the root canal loosely, without compaction, first for a day, then again for 1-3-7 days, depending on the clinical picture. In case of acute periapical abscess, periostotomy is performed according to indications.
At chronic destructive processes in the apical periodontium The goal is to provide not only an anti-inflammatory and antimicrobial effect, but also to stimulate reparative processes in the bone. Calcium hydroxide is injected into the root canal with compaction to the walls for 3-8 weeks, the time of renewal of the material depends on the clinical picture. Treatment is designed for a period of 0.5 to 1 year, its duration depends on the degree of infection of the root canal, the body's resistance, the patient's age, and motivation to cooperate. Restoration of the zone of destruction of the apical periodontium continues after continuous filling of the root canal with a calcium hydroxide-based sealer for 3-5 years.
Filling teeth with apical periodontitis at the first visit does not eliminate acute inflammation. Resorption of cement and dentin persists even 9 months after filling. Moreover, in 80% of cases a chronic process is formed. If the canal after drainage was filled with calcium hydroxide for 7 days before obturation, the periapical defect was replaced with new bone tissue, although in 18.8% of cases the inflammation progressed.
Acute reactions during hermetic closure of the coronal cavity persisted in only 5% of teeth in the presence of a periapical abscess. A temporary dressing and sealed seal prevent re-infection of the canal and increase the success of conservative treatment to 61.1% (compared to 22.2% without an antibacterial dressing).
When calcium hydroxide is used as a temporary dressing, after 3 years complete bone regeneration is observed in 82% of periapical lesions even large size. In 18% of cases, bone defects remained or slightly decreased in size. The most active reduction in the size of the defect was observed in the first year of treatment. The first positive signs were detected on radiographs 12 weeks after the introduction of the Ca(OH) 2 bandage, and on digital radiographs already after 3-6 weeks.
"Yesterday" calcium hydroxide. Information materials, science articles about calcium hydroxide preparations 20-30 years ago they convinced (and convinced) us of its unique abilities: pastes based on calcium hydroxide have a highly alkaline reaction, unlimited bactericidal action, and the ability to stimulate reparative processes in bone tissue.
The use of calcium hydroxide in endodontics has expanded the indications for conservative treatment of destructive processes in the apical periodontium. It is now possible to fully preserve teeth that were previously considered hopeless. "The biocompatibility of calcium hydroxide has made it a multivalent preparation adapted to almost all clinical situations encountered in endodontics". Recommendations have appeared on the mandatory stage of temporary filling of root canals during endodontic treatment: “This is useful!”
“Today” a baggage of clinical observations has been accumulated, which confirm very high efficiency calcium hydroxide (Fig. 1-4; from the authors’ own observations). High-quality implementation of all stages of endodontic treatment in combination with temporary filling of root canals with calcium hydroxide allows us to recognize this method of treatment as organ-saving.
|
|
|
But today in the dental literature the issues of the breadth of the antibacterial action of calcium hydroxide preparations, targeted effects on the most resistant and aggressive strains of microorganisms that cause the development of periapical foci of destruction, re-infection and the development of exacerbations are discussed.
So, A.A. Antanyan writes: “Multilateral analysis scientific literature recent years(2003-2006) showed that calcium hydroxide has many disadvantages that call into question its routine and widespread use in endodontics. In modern endodontics vital importance has a complete preparation, cleansing the canal from infection during the first visit (using copious rinses with sodium hypochlorite) and preventing re-infection of the canal by fully sealing the tooth crown using high-quality temporary fillings. Therefore, in many clinical situations, additional disinfection with calcium hydroxide is not necessary.”
"Tomorrow" calcium hydroxide. Experience in the clinical use of calcium hydroxide shows that the need for its use in endodontics cannot be justified solely by its antimicrobial effectiveness, which in past years was primarily responsible for the treatment outcome. With the advent of sensitive methods of microbiological research, with the expansion of the range of highly effective means for irrigation of root canals, the possibilities and properties of calcium hydroxide as a material for temporary filling can be rethought and reevaluated. But not discounted! In difficult clinical situations involving endodontic treatment and re-treatment of teeth, thanks to calcium hydroxide preparations, it is possible to preserve the patient’s teeth and health.
LITERATURE
1. Antanyan A. A.// Endodontics today. - 2007. - No. 1. - P. 59-69.
2. Beer R., Bauman M.A. Illustrated guide to endodontology. - M., 2006. - 240 p.
3. Glinka N.L. general chemistry: Textbook. manual for universities. - 20th ed., rev. / Ed. Rabinovich V.A. - L., 1979. - P. 614-617.
4. Gutman J.L., Dumsha T.S., Lovdel P.E. Solving problems in endodontics: Prevention, diagnosis and treatment / Transl. from English - M., 2008. - 592 p.
5. Poltavsky V.P. Intracanal medicine: Modern methods. - M., 2007. - 88 p.
6. Simakova T.G., Pozharitskaya M.M., Sinitsyna V.I.// Endodontics today. - 2007. - No. 2. - P. 27-31.
7. Solovyova A.B.// Dentsplay News. - 2003. - No. 8. - P. 14-16.
8. Kholina M.A.// Dentplay News. - 2007. - No. 14. - pp. 42-45.
9. Abdullah M., Yuan-Ling N., Moles D., Spratt D.// J. Endod. - 2005. - V. 31, N 1. - P. 30-36.
10. Allais G.// New in dentistry. - 2005. - No. 1. - P. 5-15.
11. Athanassiadis B., Abbott P.V., Walsh L.J.// Austr. Dent. J. - 2007. - Mar; 52 (Suppl 1). - S. 64-82.
12. Basrani B., Santos J.M., Tjäderhane L. et al. // Oral Surg. Oral Med. Oral Pathol. Oral radiol. Endod. - 2002. - Aug; 94(2). - P. 240-245.
13. Cwikla S., Belanger M., Giguere S., Vertucci F.// J. Endod. - 2005. - V. 31, N 1. - P. 50-52.
14. Ercan E., Ozekinci T., Atakul F., Gül K.// J. Endod. - 2004. - Feb; 30(2). - P. 84-87.
15. Gomes B., Souza S., Ferraz C.//Intern. Endod. J. - 2003 - V. 36. - P. 267-275.
16. Heckendorff M., HulsmannM. // New in dentistry. - 2003. - No. 5. - P. 38-41.
17. Lambrianidis T., Margelos J., Beites P.//Intern. Endod. J. - 1999. - V. 25, N 2. - P. 85-88.
18. Regan J.D., Fleury A.A.// J. Ir. Dent. Assoc. - 2006. - Autumn; 52 (2) - P. 84-92.
19. Sathorn C., Parashos P., Messer H.//Intern. Endod. J. - 2007. - V. 40, Issue 1. - P. 2-10.
20. Siqueira J.F., Paiva S.S., Rôças I.N.// J. Endod. - 2007. - May; 33(5). - P. 541-547.
Modern dentistry. - 2009. - No. 2. - P. 4-9.
Attention!The article is addressed to medical specialists. Reprinting this article or its fragments on the Internet without a hyperlink to the source is considered a violation of copyright.