The indications for intervisit dressing of the root canal with calcium hydroxide have been considered in Part 7. 4 A calcium hydroxide cement may be applied to protect the pulp in a deep cavity as discussed later. The calcium hydroxide should be placed gently directly on to the tissue, with no debris or blood intervening. When performing pulp capping, pulpotomy or treatment to an open apex in a pulpless tooth, the exposed tissue should be cleaned thoroughly, any haemorrhage arrested by irrigation with sterile saline and the use of sterile cotton wool pledgets. The method of application of calcium hydroxide to tissue is important if the maximum benefit is to be gained. The clinical situations where calcium hydroxide may be used in endodontics are discussed below and the techniques described. Root canal sealers containing calcium hydroxide are available, and are discussed in Part 5. The advantages of using calcium hydroxide in this form are that variable consistencies may be mixed and a pH of about 12 is achieved, which is higher than that of proprietary brands. Because of the antibacterial effect of calcium hydroxide, it is not necessary to add a germicide. 1), although ordinary calcium hydroxide powder BP may be purchased from a chemist and mixed with purified water. Various proprietary brands are available, ( Fig. PresentationĬalcium hydroxide can be applied as a hard setting cement, as a paste or as a powder/liquid mixture, depending on the treatment. Finally, calcium ions are an integral part of the immunological reaction and may activate the calcium-dependent adenosine triphosphatase reaction associated with hard tissue formation. 3 It also has a bactericidal effect and will denature proteins found in the root canal, thereby making them less toxic. suggest that calcium hydroxide may have other actions these include, for example, arresting inflammatory root resorption and stimulation of healing. demonstrated that untreated teeth with pulpal necrosis had a pH of 6.0 to 7.4 in the pulp dentine and periodontal ligament, whereas, after calcium hydroxide had been placed in the canals, the teeth showed a pH range in the peripheral dentine of 7.4 to 9.6. It has been shown that the dis-association coefficient of calcium hydroxide of 0.17 permits a slow, controlled release of both calcium and hydroxyl ions which can diffuse through dentinal tubules. In external resorption, the cementum layer is lost from a portion of the root surface, which allows communication through the dentinal tubules between the root canal and the periodontal tissues. The barrier, which is composed of osteodentine, is not always complete and is porous. The calcified material which is produced appears to be the product of both odontoblasts and connective tissue cells and may be termed osteodentine. The alkaline pH induced not only neutralises lactic acid from the osteoclasts, thus preventing a dissolution of the mineral components of dentine, but could also activate alkaline phosphatases which play an important role in hard tissue formation. 2 The hydroxyl group is considered to be the most important component of calcium hydroxide as it provides an alkaline environment which encourages repair and active calcification. However, the calcium ions that form the barrier are derived entirely from the bloodstream and not from the calcium hydroxide. Beyond this layer only a mild inflammatory response is seen, and providing the operating field was kept free of bacteria when the material was placed, a hard tissue barrier may be formed. Because of the high pH of the material, up to 12.5, a superficial layer of necrosis occurs in the pulp to a depth of up to 2 mm. Mode of actionĪ calcified barrier may be induced when calcium hydroxide is used as a pulp-capping agent or placed in the root canal in contact with healthy pulpal or periodontal tissue. It also plays a major role as an intervisit dressing in the disinfection of the root canal system. It is the most commonly used dressing for treatment of the vital pulp. Calcium hydroxide was originally introduced to the field of endodontics by Herman 1 in 1930 as a pulp-capping agent, but its uses today are widespread in endodontic therapy.
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