Enamel translucency

Glass polyalkenoate cement has a unique combination of properties. It adheres to tooth material and base metals. It releases fluoride over a long period and is a cariostat. In addition it is translucent and so can be colour-matched to enamel. New clinical techniques have been devised to exploit the unique characteristics of the material. 

A restorative material can be used for the aesthetic restoration of the front (anterior) teeth only if it is as translucent as tooth enamel. This is because colour matching depends on translucency as well as hue and chroma. 

Voelker (1916a) reported three early dental silicate cements which appeared in 1895, 1897 and 1902 all proved inadequate. The first successful material was developed by Steenbock (1903,1904) who explicitly sought and formulated a translucent cement (Voelker, 1916a,b). It was marketed by Ascher in 1904 as New Enamel Richters Harvadid cement followed in the same year. Thereafter development was rapid and eight varieties were reported by Morgenstem in 1905. However, from their chemical composition we doubt whether they were sufficiently translucent. 

Dental silicate cement is used for the aesthetic restoration of anterior (front) teeth because it is translucent and so can be made to colour-match tooth enamel. It is prepared by introducing powder into the liquid gradually in order to dissipate heat, although the exotherm is not so great... 

Zinc oxide has a wide range of uses apart from its use as an artist s pigment where it provides a more translucent white than flake white or titanium white. It is used in cosmetics, driers, quick-setting cements with syrupy phosphoric acid or zinc chloride in dental cement in the manufacture of opaque glass, enamels, car tyres, white glue, matches, white printing inks and porcelain. The photophysics of zinc oxide has been reviewed.1468 ... 

The fluoride ion can replace the hydroxide ion in a crystal without significantly altering its structure, an isomorphous ion replacement. Fluoride also affects the enzymes involved in enamel formation, causing mottled enamel, a severe example of enamel fluorosis. White opaque patches on the normally translucent enamel indicate mild fluorosis. Fluorosis is measured on a grade of 0-5 where 1 through 3 indicate an increased cover of opaque white patches on the tooth surface, and 4 and 5 indicate an increased mottling. The two worst affected teeth make up an individual s score. The community s index of fluoridation is the mean score for all individuals. As the natural or artificial fluoride concentration of the water supply increases to 1 ppm, the mean number of cavities in 10-12 year-old children decreases from 7 to 3. Above 1 ppm fluoride, caries does not decrease much more, but the index of fluorosis increases markedly. This is the reason why public water supplies are fluoridated to only 1 ppm and not more or less. 

Vitreous enamels bonded to glass surfaces are used to produce translucent colours for functional or decorative purposes. Such enamels have a low melting point and are applied by spraying, silk screening or decalcomania and are fired in a decorative lehr [1]. 

Properties Colorless translucent crystals or powd., odorless, strongly acidic tart taste very sol. in water, alcohol, and ether very si. sol. in ether m.w. 192.43 dens. 1.542 m.p. 153 C flash pt. 212 F Toxtology LD50 (oral, rat) 6730 mg/kg poison by IV mod. toxic by subcut. and IP routes poison by IV route mildly toxic by ingestion primary irritant severe eye, mod. skin irritant some allergenic props. erodes tooth enamel TSCA listed... 

Solution of gum or of natural or synthetic resins that dries to a thin, hard, usually glossy film it may be transparent, translucent, or tinted. Oil varnishes are made from hard gum or resin dissolved in oil. Spirit varnishes, e.g., shellac, are usually made of soft gums or resins dissolved in a volatile solvent. Enamel is varnish with added pigments. Lacquer may be either a synthetic or natural varnish. As a decorative or protective coating, varnish has been used for oil paintings, for string instruments, and, by the ancient Egyptians, for mummy cases. 

Basse-taille. Vitreous enamelled artware in which a pattern is first cut in low relief on the metal backing, usually silver the hollows are then filled with translucent enamel, which is subsequently fired on. Basset Process. For the simultaneous production of hydraulic cement and pig-iron by the treatment, in a rotary kiln, of... 

This development, which dates back to 1972, forms the basis for the fabrication of DICOR glass-ceramics. The properties of this material were modified to develop a biomaterial (see Section 4.4.2). For example, the translucency of the material had to be adjusted to the translucency of natural dental enamel. This objective was fulfilled by reducing the crystalUte size durii the development of DICOR MGC glass-ceramics (Grossman 1989 and Beall 1992). 

First, glass-ionomer fissure sealants release fluoride in amounts that are protective to the surrounding tooth tissue. Second, not all of a glass-ionomer sealant is actually lost. Deep within the fissures, glass-ionomer sealants are retained and not only retained, but also transformed over time. Changes which occur include increasing translucency, improvement in smoothness and in hardness, and elevation in the calcium and phosphate ion concentrations in the surface layer. These alterations take of the order of 2-3 years to develop and seem to be akin to the development of artificial enamel (Van Duinen et al. 2004). 

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