Filling materials

Filling materials. Distinguish between temporary and permanent seal. The first is used in the treatment of the tooth to close the carious cavity in the short term. For these purposes use of so-called artificial dentin. The latter is a white powder (zinc oxide - 66%, dehydrated sulphate zinc - 24% and kaolin - 10%), knead on the water (2 hours of powder per 1 h of water). The obtained homogeneous pasty mass quickly hardens. Instead of water, powder often get mixed up in vegetable oil (sunflower, peach). Such seals differ significantly higher strength. The most common materials for permanent fillings are mercury amalgam, dental cement, plastics. Gold has lost its former significance filling material is mainly due to the improvement of other materials. It only applies for the manufacture of cast gold tabs (see Tab dental).
Amalgam - metal alloys with mercury. The most often used silver amalgam. It contains silver (60 - 65%), tin (not less than 25%), copper, and zinc - in the form of sawdust or chips, to which are added mercury. The mixture is pounded in a mortar or in the special unit (amalgamator) before reception of plastic weight. With the admixture of gold amalgam called gold. Copper amalgam only includes copper and mercury. The main properties of amalgams are mechanical strength, high degree of plasticity, easy handling and low cost; the weak side of them - the tendency to change shape and volume, which, however, is so insignificant, that did not significantly affect the quality of the seal. The opinion that amalgamated dental filling can be a source of chronic intoxication with mercury, was not confirmed.
Dental cements are made of powder and liquid; they are divided into phosphate and silicate-cements. Powder phosphate cement is composed of zinc oxide (75-90%) with a mixture of magnesium oxide and silica. The fluid is orthophosphoric acid, partially offset by zinc oxide and hydroxide of aluminum. By mixing them get dough that is solidified in a few minutes. Phosphate cement has a relatively good adhesion, but chemical resistance of its insufficient, therefore its application as a filling material is limited. It is mainly used as padding the amalgam and silicate cement for filling root canals, for fixing artificial crowns and other similar purposes.
Silicate cement differs from phosphate cement composition of powder (silicate); the fluid used is the same as for phosphate cement, but with various impurities. Silicate cement after hardening lustrous and transparency, like the enamel of the tooth. This is an important advantage, along with more than phosphate cement, hardness makes silicate cement the main material for sealing of the front teeth. In deep cavities necessary insulating strip due to irritant silicate cement on the pulp (there are cases of ossification of the pulp under silicate-concrete seal).
In some cases, for sealing the premolars and molars apply arkodent-cement is a mixture of phosphate and silicate cement in different proportions.
Used as filling material rapid hardening plastic possess sufficient mechanical strength and chemical resistance, adhesion and transparency. Disadvantages them - reduction of volume during polymerization and weak color fastness.