SEALING MATERIALS

From Big Medical Encyclopedia

SEALING MATERIALS — the materials intended for filling of defects of solid tissues of tooth and the channel of a fang in the course of treatment.

P. Foshar in 1728 provided the description of dental surgery materials and ways of their use; as P. of m it applied tin. In 1819 Bellom (Th. Bell) was for the first time received amalgam by mixing of silver and mercury, and in 1826 the dentist Tavo (O. of Taveau) applied mix under the name «silver paste» to sealing of teeth. In 1878 Rostaing offered zinc - phosphatic cement, in 1903 Mr. Ascher put silicate cement into practice. In 1939 Mr. G. L. Slack for the first time applied the most hardening acrylic resin to sealing of teeth and in the 50th plastic seals were widely adopted.

Items of m conditionally subdivide into the materials intended for temporary seals, for constant seals for laying and for sealing of the channel of a fang. As P. the m for temporary seals more often use artificial dentine (Fletcher's dentine) containing 65 — 70% of zinc oxide, 25% of zinc sulfate and 10% of a kaolin. For this P.'s receiving m powder of artificial dentine is mixed with water and pounded the pallet before obtaining pasty weight. During the mixing of powder of dentine with vegetable oils (sunflower, peach, apricot or clove) dentine-paste which hardens more slowly than water dentine is formed, but durability of such seal is higher, and it can remain in a pulp cavity up to several months.

The amalgams applied to constant seals, cements and plastic shall have mechanical stability, resistance to influence of oral liquid, good cosmetic properties, to be harmless to an organism, to adjoin densely to walls of a pulp cavity, to be rather plastic and to harden quickly at body temperature.

Amalgam call compound (alloy) of mercury with one or several metals. During the mixing of the mercury which is at the room temperature in liquid state with metal sawdust or powder of metals plastic quick-hardening connections are formed. This process carries the name of amalgamation. Preparation of amalgam is made manually in a mortar or an amalgamosmesitel. Distinguish copper amalgam which powder consists of copper (32 — 37%) and zinc, and silver, argentiferous (66 — 68,5%), tin, copper, zinc. Thanks to high fizikomekhanichesky properties amalgam remains to the best P. of m for filling of carious cavities I, II and V classes (see. Caries of tooth ). The item of m without mercury for receiving metal seals consists of alloy copper — tin or gallium — tin and liquids.

As cement seals apply 8 types P. of m. All of them consist of powder and liquid. Preparation of seals is made by mixing of powder and liquid on a glass plate (at 20±2 °) by means of the plastic or chrome-plated metal pallet.

Zinc-phosphatic cement consists of powder which basis is zinc oxide (80 — 85%) with addition of magnesium oxide and silicon dioxide, and also bismuth oxide, fluorides and liquids — water solution orthophosphoric to - you (38 — 44%), partially neutralized zinc oxide and aluminum hydroxide. Zinc-phosphatic cement is widely applied to fixing of different types of fixed prostheses, orthodontic devices, sealing of the channel of a fang, milk teeth, as the isolating laying under constant seals from amalgam, plastic, silicate and siliko-phosphatic cements.

Bactericidal cement is a zinc - phosphatic cement, oxidiferous copper, silver salts or other antibacterial agents. Because of coloring of solid tissues of tooth its use is limited generally to sealing of milk teeth. However it is widely used as laying.

The silicate cement prepared for sealing unlike tsiik-phosphatic possesses in the color and gloss close to natural. Powder of cement — the tonkoizmel-chenny glass consisting of aluminosilicates and fluorides is easily painted that allows to receive a wide range of shades. The hardened silicate cement consists of not dissolved particles of powder and the basis representing silica gel.

Silikofosfatny cement consists of powder which represents a combination phosphatic (5 — 40%) and silicate (95 — 60%) powders. Powders can be mixed mechanically or bake together, and then be exposed to a grinding. During the use of the powder received on the last way, cement has the best properties. On physicomechanical properties and appointment silikofosfatny cement is close to silicate.

Zinc-oxide-evgenolny cement is formed during the mixing of zinc oxide with eugenol. Thanks to the minimum irritating and certain bacteriostatic properties cement is widely applied as the medical and isolating laying under temporary seals (under plastic seals it is impossible), to temporary fixing of prostheses and sealing of the channel of a fang.

Polymeric cements on structure are similar to plastic P. to m for constant seals, are applied to fixing of tabs, orthodontic devices and fixed prostheses preferential on deiulpi-rovanny teeth.

Polycarboxylaled cement consists of powder (thermochemical the processed zinc oxide with addition of magnesium oxide) and liquids (water solution of 32 — 42% of the poly(acrylic to - you with a molecular weight apprx. 50 000). Polycarboxylaled cement in comparison with usual mineral cements has a number of the advantages caused by the fact that a part of cement instead of orthophosphoric to - you are organic the poly(acrylic to - that. In comparison with zinc - phosphatic cement polycarboxylaled cement has less expressed effect on a pulp of tooth and a periodontium, possesses a steady chemical bond in the wet environment with enamel and dentine. Besides, polycarboxylaled cement has smaller solubility, but concedes zinc - phosphatic to cement in a compressive strength. It is intended for fixing of fixed prostheses and orthodontic devices, for sealing of milk teeth as jointing. In an optimum state pasty mix has a lustrous brilliant surface.

Silica-alumina glass with addition of fluorides (powder) and aqueous solution (50%) of the poly(acrylic to - you with a molecular weight (weighing) up to 27 000 is a part of ionomeric cement (liquid). Physicomechanical properties of ionomeric cement are higher, than at polikarborksilatny and are close to those of silicate cement. However it differs from the last adgezivnostyo and smaller irritant action on a pulp. Basic purpose — sealing of carious cavities of the V class and not carious defects of cervical area of chewing teeth at children, fixing of fixed prostheses.

Plastic as P. in m have flexural strength and blow, low heat conductivity, good cosmetic properties. The improved plastic, so-called composites (composite materials) as an organic basis contain epoxyacrylate resins in various combinations and modifications. A filler most often is the kind of quartz, silica-alumina or borsili-katny glass in number of 50% and more. Between a filler and an organic basis apply surfactant to receiving strong communication — silane. Introduction of a significant amount of a filler led to increase in durability, decrease in shrinkage, water absorption and temperature expansion coefficient of composite seals in comparison with unfilled plastic. Composites are released in a complex by powder-liquid, paste — paste, paste — liquid. Time of hardening of material in an oral cavity of 2 — 3 min.

The most widespread P. of m for laying is zinc-fos-fatny cement, especially with addition of fluorine, copper, silver. For the same purposes artificial dentine, zinc-oxide-evgenolny cement, and also materials on the basis of lime hydrate can be used. The last promote adjournment of secondary dentine and remineralization of a softened dentine, are applied at treatment of deep caries.

For sealing of the channel of a fang zinc - phosphatic cement of a liquid consistence, and also various pastes is used: zinc-oxide-evgenolnaya, resorcin form ruled, the slow-setting paste prepared on the basis of epoxies — endodent.

To walls of the channel of a fang apply pins to more dense prileganiye of plastic P. of m (silver, gutta-percha) various diameter and length. Pins promote P.'s advance m to a top of a fang, facilitate and accelerate the procedure of sealing (see. Sealing of teeth ).

At bad passability of the channel of a fang apply imiregniruyushchy substances. Re-zortsin-formalin liquid, bakelite weight, etc. concern to them.



Bibliography: Gerner M. M., etc. Fundamentals of materials science on stomatology, M., 1 969; About r about in about y B. Ya. and And in and N about in V. S. Sealing materials on the basis of epoxies, M., 1973; KA ra cling to D. M. Features of a clinical use of a gallodent — M, Stomatology, No. 1, page 75, 1978; it, Technique of a clinical use of amalgam, in the same place, No. 1, page 48, 1980; To and r and l N and to D. M., etc. Results of development and a clinical use of polycarboxylaled cement, in book: Eksperim, and wedge, stomatol., under the editorship of A. I. Rybakov, etc., t. 7, p.1, page 93, M., 1977; A. I. Fishermen, Ivanov In, S. and To and r and l N and to D. M. Sealing materials, M., 1981; With t r e of l go-cinchona T. T. Dental sealing materials, L., 1969; Bowen R. L. ampere-second of 1 e e k G. W. A new series of X-ray opaque reinforsing fillers for composite materials, J. dent. Res., v. 51, p. 177, 1972; Restorative dental materials, ed. by F. A. Peyton a. R. Cx. Craig, St Louis, 1971; Skinner E. W. a. Phillips R.W. Science of dental materials, Philadelphia, 1973; W i 1 s o n A. D. a. K e n t B. E. A new translucent cement for dentistry, The glass ionomer cement, Brit. dent. J., v. 132, p. 133, 1972.


V. S. Ivanov, D. M. Karalnik.

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