Tooth colour

Lloyd, C. H. Mitchell, L. (1984). The fracture toughness of tooth coloured restorative materials. Journal of Oral Rehabilitation, 11, 257-72. 

Qvist, V. (1975). Pulp reactions in human teeth to tooth coloured filling materials. Scandinavian Journal of Dental Research, 83, 54-66. 

Conventional glass-ionomers are tooth coloured, and have a degree of translucency. This gives them reasonable aesthetics, though they are less aesthetic than composite resins, mainly because they remain relatively opaque compared with the tooth itself [218],... 

This chapter is concerned with the essential classification of the materials used to repair teeth and restore their function. As far as direct restoratives are concerned, we follow the classification on Mount et al. [1] and consider that the two basic types of modem tooth-coloured materials are the composite resins and the glass-ionomer cements. They are fundamentally different, and though hybrids have been attempted, combining their advantages is not feasible for sound scientific reasons. 

As we have seen, in the classification of tooth-coloured dental restorative materials, the composite resins represent one of the major types [1,6], The other major type is the glass-ionomer cement. 

Clinical aspects of the tooth-coloured restorative materials... 

The alternative tooth-coloured material, the glass-ionomer cement, has also been widely studied, especially in terms of its bioactivity. This arises from its ability to exchange ions with its surroundings when placed in the mouth. Typical conventional glass-ionomers have been shown to release sodium, silicon and phosphorus under neutral conditions, and also calcium and aluminium under acidic conditions [48]. The non-metals are assumed to be released as sihcate, Si03 ", and phosphate, PO/, respectively. In addition, they release fluoride [49], a process that is capable of continuing for several years [50]. 

Hwang YJ et al (2005) Controlled release of retinol from silica particles prepared in OAV/0 emulsion the effects of surfactants and polymers. J Control Release 106 339-349 Jenning V et al (2000) Vitamin A loaded solid lipid nanoparticles for topical use drug release properties. J Control Release 66 115-126 Joiner A (2004) Tooth colour a review of the literature. J Dent 32 3-12 Joiner A (2006) The bleaching of teeth a review of the literature. J Dent 34 412—419 Kim DG et al (2006) Retinol-encapsulated low molecular water-soluble chitosan nanoparticles. Int JPharm 319 130-138... 

Whitening mouthwashes These are aqueous or hydroalcoholic solutions that contain the same active ingredients as toothpastes, but at a lower concentration and without abrasive agents. They include whitening agents in their formulation at different concentrations, which help to maintain the tooth colour (Camps Miro, 2006). 

Whitening is not always recommendable. Each person, given their genetic heritage, has a specific tooth colour. This cannot be changed and it is only possible to lighten the tooth shade within the same colour range. 

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. 

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... 

For certain AB cements, used in dentistry, optical properties are important for their overall acceptability as materials. The two particular properties of interest have been colour and translucency, both of which need to match natural tooth material as closely as possible if good aesthetics are to be developed (Wilson McLean, 1988). Of the AB cements currently used in dentistry, the glass-ionomer cement has the best aesthetics, since it has a... 

Evaluation of these optical properties may be done by simple observation this approach is useful clinically (Knibbs, Plant Pearson, 1986), since acceptability of the colour match to the surrounding tooth material can be readily seen without the need for instrumental measurement. On the other hand, for quantitative evaluation of optical properties, some kind of instrumental measurement is necessary, and the property usually evaluated is opacity. 

Colour and opacity have been foimd to be connected for glass-ionomer cements (Crisp et al., 1979 Asmussen, 1983), with darker shades giving increased opacity. However, this is merely a consequence of the underlying physical relationships, and is not thought to be a clinical problem (Wilson McLean, 1988), mainly because the stained tooth material for which the darker shades are necessary for colour match is itself of reduced translucency. 

In this layer a highly worn tooth differently coloured to the other bones was found its stratigraphical position is uncertain ... 

A so-called congested tongue or liver tongue (R. Pannhorst et al., 1957) is voluminous due to the accumulation of fluid and displays tooth marks at the edges. It often has a deep median vertical groove and several small furrows or fissures. Corresponding to its occurrence with (or due to) portal hypertension, it is bluish purple in colour and its undersurface displays greatly distended veins. (15)... 

Evidence for metals (e.g. iron, copper, tin, silver, etc) causing stain formation appears to be significant only for individuals exposed to metals and their salts, typically in connection with their occupation or certain medicines [140, 147], Stannous-fluoride-containing toothpastes have been reported to promote golden brown discolourations [63], The mechanism for stain formation probably involves interaction of dietary chromogens and metal ions forming coloured complexes on the tooth surfaces, as indicated by in vitro and in vivo studies [159,161]. 

Live and dead lice (about 3 mm long and greyish-white or brown in colour) and yellowish cast exoskeleton shells can be seen by combing the hair with a fine-tooth comb over a sheet of white paper, after shampooing and towelling dry. Lice faecal material (black specks) may be found on pillows and collars. 

Today, a large segment of utilisation ofzirconia as colour-adapted tooth veneers in dental restoration exists (Cales, 1998). At this point, it is appropriate to mention the ancient French dental doctor Pierre Fauchard (1678-1761) who may be considered the vanguard of modern tooth restoration. He has been credited with recognising the potential of porcelain enamels and initiating research with porcelain to imitate the natural colour of teeth and gingival tissue (Fauchard, 1728). 

Dental silicate cements were used as aesthetic repair materials for anterior teeth [7]. Though they lacked the ability to adhere to the tooth, they did have a reasonable match for the appearance of the natural tooth, both in terms of colour and translucency. Nonetheless, they were not entirely satisfactory in clinical service and in particular were susceptible to acid erosion and staining in the mouth [7]. 

Filler loadings are low by comparison with some of the better conventional composites available, and this means that there is a relatively large volumetric shrinkage on polymerization [1]. However, to an extent swelling due to moisture uptake offsets this. Despite this moisture uptake, aesthetics of these materials are reasonable though they are now generally recommended for use in children s dentistry, and are available in a variety of colours (pink, blue, green) so that aesthetics in the sense of a close visual appearance to the natural tooth is less of a concern [38]. 

Composite materials are widely used in dentistry, mainly for tooth repair, but also for bonding orthodontic brackets. The range of components that can be used is restricted by a number of considerations, including the need to match the appearance (colour and translucency) of the natural tooth, and the need to restrict the substances used to those which are non-toxic. It is also important to use materials having appropriate mechanical properties. Current materials are described in this chapter, with information on their clinical applications and performance. Some information is also included on recent developments in these materials and these may affect their clinical use in the future. 

Other initiator systems have been used, such as PPD (l-phenyl-l,2-propanedione) [14] and bis-acylphosphine oxide [15]. They have the advantage of being less intensely coloured than camphorquinone, and consequently there is a much closer colour match between the composite in its cured and uncured states. This makes choosing the correct shade of composite to match the tooth more straightforward [8]. Despite the differences in the chemistry of these substances, their essential mode of action is the same in all cases. They become excited by light of a specific wavelength, as a result of which they fragment into free radicals, and the free radicals then go on to promote polymerization of the monomers. 

In addition to their good mechanical properties, composites typically show low thermal conductivities and minimal water absorption [21]. This allows them to protect the tooth from thermal damage when hot foodstuffs or beverages are consumed. Also, colour and appearance remain stable over extended periods of time. 

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