Calcium Hydroxide

Caoh2- Calcium Hydroxide

Caoh2 or Calcium hydroxide, represented by the chemical formula of Ca(oh)2,  is a compound created by mixing calcium oxide with water. The result is a crystal white power with strong alkaline properties which is traditionally called slaked lime. Its molecular weight: is 74.092 g/mol.

Ca Oh 2 has many other names including , hydrated lime, builders lime, slack lime or pickling lime.

Ca(OH)2 Production

Make Calcium Hydroxide

Obtaining calcium hydroxide is cheap and doesn’t need special equipment since Ca(OH)2 is not a toxic agent. Because of its -OH radicals the chemical is used for raising the pH of the water. It neutralizes the acids and regulates the pH. A typical characteristic for Ca oh 2 is that it doesn’t raise the pH to a very high level.

Calcium hydroxide is produced by mixing water (H2O) with lime (CaO):

CaO + H2O = Ca(OH)2

This is the cheapest and most efficient method to produce slaked lime. Another way to obtain hydrated lime is by mixing sodium hydroxide with calcium chloride. Both NaOH and CaCl2 must be in aqueous solutions:

2NaOH + CaCl2 =2NaCl + Ca(OH)2

Physical properties: It is produced as colorless crystals or a white powder with a density of 2.21 g/cm³ and melting point of 580 °C.

Chemical Properties: It is poorly soluble in water, its pH is alkaline, approximately 12.4, which allows it to be a superb bactericide, until the spores die upon contact with the element. It is commonly prepared with saline or treated water, although any presentation or trademark may be used. Its natural source are listed below.

  • Cement
  • Lime water
  • Many solvents and industrial cleaners (hundreds of thousands of construction products, floor scrapers, brick cleaners, cement hardeners and many others)
  • Lime off

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Some Characteristics

  1. Stimulates calcification, in a very clear way, activates the repair processes by osteoblastic activation; With increasing pH in dental tissues (Tronsland, 1981 ); Believes that such a change in pH is beneficial because it further inhibits osteoclast activity.
  2. Antibacterial. Kodukula in 1988, reports that high pH conditions lowers the concentration of H + ions; And the enzymatic activity of the bacteria is inhibited. It can sterilize up to 88% of root canals (Cuek, 1976 ).
  3.  Decreases Edema.
  4. Destroy the Exudate.
  5. Generates a mechanical barrier of apical healing.
  6. Balanced Toxicity when mixed with physiological solution or anesthesia

Calcium Hydroxide Uses

The calcium hydroxide has a vast array of usage. For instance, its used in the manufacture of hair products, in the dental industry, food manufacturing, in leather production etc.

Dental Antimicrobial solution

The National Institute of Health promotes Calcium Hydroxide as a commonly used ingredient in the manufacture of antimicrobial root canal sealers. Ca(OH)2 is the main substance used when preparing the protective layer known in medical terms as the Apical barrier. Apical barriers are often used in situations where endodontic surgery is difficult to perform. The calcium hydroxide disinfects the tooth by killing the bacteria. Furthermore, its used as a temporary means for reducing pain and swelling as the patient waits for endodontic surgery. Its high pH makes Ca(OH)2 a perfect choice for a temporary antibacterial root canal filler.

Application of hydrated lime in the manufacture of hair products

Some hair relaxers use calcium hydroxide as an active alkaline ingredient. These are liquids or creams used to straighten curly hair during styling. Many hair relaxers contain lye, which is a powerful caustic solution. Unfortunately, lye damages both the hair and skin, and more people are shunning hair relaxers with this compound. Instead, they are going for hair relaxers manufactured with calcium hydroxide as a substitute for lye.

Ca(OH)2 straightens curly hair just like lye. Studies conducted by Cornell Medical research show that calcium hydroxide disintegrates sidulfide bonds that hold together cysteines. Cysteines are amino acids which occur naturally in curly hair. Unless they are broken, the hair will remain in that condition. Calcium hydroxide breaks and seals off those bonds so that the physical structure of the hair is altered completely.

In leather production

Leather cannot be used with hair on it. Animal hair has to be separated from the hide before the skin can be put to effective use. A mixture of warm water and calcium hydroxide is used during this operation, where fresh hide is dipped inside and stirred frequently for 4 days. This process loosen the structure of the hair such that it can be removed by hand. When that happens, the hide is dipped in ammonium sulfate solution to counter the caustic effect of calcium hydroxide and to balance the pH as well.

In food production

It may be used in the processing of some alcoholic and soft drinks. Calcium hydroxide is one of the ingredients found in Lutefisk, a traditional dish native to Swedish people. According to Nordic Recipe Archive, this diet is comprised on stockfish soaked in cold water for several days. Once the fish is soaked, its dipped in a solution of water and lye or other caustic solutions such as Calcium hydroxide. The aim is to break down the proteins inside the fish to result in a delicate fish diet with a jelly-like consistency. Furthermore, it makes the fish taste caustic, so the fish has to be dipped in cold water for additional days before it can be eaten.

The calcium hydroxide has a number of uses in the food industry as well. It plays a key role in the separation of sugar from sugar cane. In native American cooking, its called Cal. They cook cone with cal and they call it nixtamal. This diet is considered tastier and easier to digest. So it looks like the food industry is benefiting more than any other industry.

The slack lime may be used in the sea as well. Research shows that it reduces the greenhouse effect as well as the amount of atmospheric pressure thats in the air. However, when its used this way, it has to be produced in massive quantities which is quite expensive.

Some households use it as an insecticide. Most crawling and flying insects die when they come into contact with calcium hydroxide. Insects that react to it include bees, beetles, flees, and grubs. It may offer a cost-effective measure of eliminating these insects easily.

Clinical Applications

1. Indirect coatings: in deep caries and pulp transparency induces repair by secondary dentin formation.

2. Direct Coating: in young permanent pulps with exposure from 0.5 to 1.55 mm.

3. Pulpotomies: Induces the formation of a calcium barrier by pulp amputation.

4. Duct washing: Ca (OH) 2 can be prepared in a 3 to 5% solution; Is a washing agent and entrains the necrotic material.

5. Control of Exudates: because it is little soluble, it produces an exudate, a gelatin that in the long term provokes a thrombolytic action by the absorption.

It is used in pulpotomy, has its internal perforating action and resorption, in rhizogenesis and other treatments.

Calcium hydroxide is a fine white powder, used especially in Dental Operation and Endodontics. Herman introduced it in 1920 as a paste, and from then until now its uses are multiple. In surgery it is used in indirect pulp protection or pulp coating. The calcium hydroxide acts on the microorganisms that remained in the dentine after the cavity preparation, destroying them and promoting that the pulp produces secondary dentine as a defense. It has a strongly alkaline pH, this explains why it is so bactericidal which kill the spores.

Calcium hydroxide is also very useful in protecting pulp directly or pulp wound, when the professional in its attempt to remove the last layer of dentin accidentally exposes the pulp, put in contact with it the calcium hydroxide forms a layer Of superficial necrosis that isolates the pulp and induces it to form a protective calcium barrier that at four or six weeks becomes evident in the x-ray.

The investigations of Zender and Col demonstrated the complete cure of the protected pulps with calcium hydroxide and introduced the technique in Argentina and Brazil. In fact the optimal use of calcium hydroxide for wound healing has been the subject of several investigations and is well demonstrated.

Intraductal medication

Calcium hydroxide could become the medicine of choice for temporary cure, it is used with distilled water or anesthetic liquid . The preferred carrier is distilled water regardless that other solutions exist as well. The important thing is that the hydroxide of calcium always acts in an aqueous, because in sec it does not hydrolyze.

In 1917 Tronstad and Col verified that the placement of the calcium hydroxide in the conduit has an active influence on the transformation of the acidic pH of the tissues into alkaline. A comparative study by Byston and Col. showed that the use of calcium hydroxide effectively removes all microorganisms from infected root canals when the temporary cure remains for 3 to 5 days.


Also called Cohen and Burns cervical pulpotomy, it is the partial surgical section of the dental pulp up to the entrance level of the root canal leaving alive the remaining stump to which it is coated with chemically pure calcium hydroxide and not the commercial products containing That substance.


Rhizogenesis is the process that gives rise to the root formation of a tooth when, for certain reasons, such as trauma, caries or iatrogenesis, a tooth has not completed the formation of its root. The pula is the only one capable of forming root dentin when, for any reason, total root formation has been interrupted.

In these cases, the researchers state (and also experience) that the best endodontic option is to stimulate the continuation of root development with special calcium hydroxide-containing cements such as Sealapex or a calcium hydroxide-thick paste with a carrier Biologically compatible such as distilled water or anesthetic solution to which Barium sulfate is added in a proportion of eight parts of Calcium Hydroxide to one of Barium Sulphate. This last element is the one that by its radio opacity allows us to control the advance of the treatment until its cure.

Use in Dentistry

It is another  pathology that is treated favorably with the Calcium Hydroxide, completely filling the empty space left in the duct by the process of internal dentin cement resorption and following as in all cases. For this and other reasons we can say that calcium hydroxide is an essential medicine in dentistry for both the general practitioner and the specialist.


There are many uses of the calcium hydroxide today. It manufactures your car break paddles, and paints your beautiful home as well. There is practically no industry that doesnt use it.

However, despite the vast uses of calcium hydroxide, it poses health risks to people who handle it more often. It may cause skin burns, blindness when it comes into contact with the eyes and it could also damage your lungs when inhaled.