Abstract
The hardest tissue in the human body is the enamel which covers the anatomical crowns of teeth. It must be resistant to mechanical stress and the chemical attack of many substances from food, drinks and products of the metabolism of bacteria present in the oral cavity. These low pH substances dissolve the mineral components of enamel, cause tooth demineralization, and lead to decay or erosion damage with the irreversible loss of dental hard tissues and the necessity of their reconstruction. The range of dental materials intended for dental tissue reconstruction is extensive. Dental amalgam can be mechanically applied into the strongly stressed lateral segments of teeth. The use of amalgam is, however, in decline, with the possible health risks attributed to it, coupled with the need to extensively prepare tooth tissue promoting a shift towards using aesthetically and biologically favourable dental ceramic and polymeric materials instead. Current developments also concentrate on these materials to reinforce this, with polymeric composite materials based on methacrylates with varying amounts of inorganic fillers at the forefront. These materials are distinguished by their good mechanical and aesthetic properties and wear resistance. However, polymerization shrinkage and a strong hydrophobic nature does not allow for their direct bonding to hard dental tissues. Risks associated with the release of residual free monomers from the structure to the environment, which may cause health complications, mainly allergic reactions in sensitive individuals, have been monitored recently. Further development in the field of composite materials aims to reduce or completely eliminate these negatives.
Highlights
Teeth are specific formations in the oral cavity which are mainly composed from hard tissues such as enamel, dentine and cementum
Enamel covers the surface of anatomical crowns and is the hardest tissue in the human body due to the high content of mineral substances
The so-called prismatic structure is typical for enamel, with closely spaced prisms bound with interprismatic substance (Fig. 1a)
Summary
Teeth are specific formations in the oral cavity which are mainly composed from hard tissues such as enamel, dentine and cementum. Enamel covers the surface of anatomical crowns and is the hardest tissue in the human body due to the high content of mineral substances. The so-called prismatic structure is typical for enamel, with closely spaced prisms bound with interprismatic substance (Fig. 1a). Enamel prisms with a diameter of 4-8 μms are formed predominantly from hydroxyapatite nanocrystals. The interprismatic mass contains proteins, except hydroxyapatite, which serve as a binder for the individual prisms. Dentine is mineralized less than enamel, is softer, and contains about 20-30 vol % of proteins and 20-30 vol % of water, and is biologically active compared to enamel. Typical structural elements are known as dentinal tubules, canals in the dentine where extensions of the odontoblasts exist alongside dentinal fluid (Fig. 1b)
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