Teeth dentine

The abrasive cleans the teeth and also contributes to ensuring the right viscosity for the toothpaste. Cleaning is done by abrasion of the stained/colored film on the surface of the teeth. Dentin, which is softer than enamel, has to be taken into account in the choice of an abrasive. The abrasive also contributes to the viscosity of the toothpaste, particularly at high concentrations (>30%). The choice of abrasive also depends on the choice of therapeutic agents, as there may be some incompatibilities, and whether the desired product is opaque or transparent. The three abrasives most frequently used are... 

Boston area children (N=158) Shed teeth dentine Pb at two levels Full scale and verbal IQ scores, WISC-R Higher tooth Pb group had full scale IQ loss of 4.5 points Needleman et al. (1979), Davis and Svendsgaard, 1987... 

But potassium nitrate is also used in toothpastes that are formulated to make teeth less sensitive to pain. As gums recede and the tooth root dentin becomes exposed, teeth can become hypersensitive to hot or cold foods. Potassium nitrate interferes with the transmission of pain signals in the nerves of the teeth. 

The 5 N enrichment in dentine collagen relative to bone collagen in species with definite tooth growth is observed in samples from Marillac, Kent s Cavern, Aldene and Mialet caves (Fig. 4.10). The highest 8 N values are measured for deciduous teeth in fossil samples (Bocherens et al. 1994 Fizet et al. 1995). No enrichment is observed between dentine and bone collagen in horses (Bocherens et al. 1995b Fizet et al. 1995). 

The properties described above have important consequences for the way in which these skeletal tissues are subsequently preserved, and hence their usefulness or otherwise as recorders of dietary signals. Several points from the discussion above are relevant here. It is useful to ask what are the most important mechanisms or routes for change in buried bones and teeth One could divide these processes into those with simple addition of new non-apatitic material (various minerals such as pyrites, silicates and simple carbonates) in pores and spaces (Hassan and Ortner 1977), and those related to change within the apatite crystals, usually in the form of recrystallization and crystal growth. The first kind of process has severe implications for alteration of bone and dentine, partly because they are porous materials with high surface area initially and because the approximately 20-30% by volume occupied by collagen is subsequently lost by hydrolysis and/or consumption by bacteria and the void filled by new minerals. Enamel is much denser and contains no pores or Haversian canals and there is very, little organic material to lose and replace with extraneous material. Cracks are the only interstices available for deposition of material. 

G. Dentine, K. Edwards, M. Jackson, D. Kantor, M. Kelley, K. Murphy, D. Valley, M. Valley, and M. Wilhite for donating or helping obtain teeth for analysis. 

Mclnroy et al. 1985). Americium radioactivity can be measured in the teeth of rats, where it accumulates in the dental pulp of developing teeth and eventually is incorporated into the mineralized dentin (Hammerstrom and Nilsson 1970). 

Teeth, the hard conical structures embedded in their jaws that vertebrate animals use to chew food, consist of two layers of compact matter surrounding a core of soft, living tissue. The inner layer is composed of dentine, also known as ivory, whose composition is similar, but not identical, to that of bone it contains less collagen and is harder than bone. The thin outer layer of the teeth, the teeth s enamel, includes even less collagen and other organic matter than dentine and is the hardest substance produced by animals (Hilson 1986a Kurten 1986b 1982). 

Ivory, or dentine, the main constituent of the teeth of mammals, is a relatively hard, cream-white material that can be carved or mechanically formed, and its surface can be polished to a high shine (O Connor et al. 1987 Wills 1968). Of particular interest is the ivory that makes up the tusks (large incisor teeth) of large mammals such as elephants, hippopotami, whales, narwhals, and... 

Bone and teeth in mammals and bony fishes all rely on calcium phosphates in the form of hydroxyapatite [Ca5(P04)30H]2, usually associated with around 5% carbonate (and referred to as carbonated apatite). The bones of the endoskeleton and the dentin and enamel of teeth have a high mineral content of carbonated apatite, and represent an extraordinary variety of structures with physical and mechanical properties exquisitely adapted to their particular function in the tissue where they are produced. We begin by discussing the formation of bone and then examine the biomineralization process leading to the hardest mineralized tissue known, the enamel of mammalian teeth. 

Dentin caries is inversely correlated with oral hygiene (Axelsson et ah, 1994 0gaard et ah, 1994) and fluoride intake (Frencken et ah, 1991). It can be expected that an improved oral status will decrease the incidence of dentin caries, but will increase root surface caries because the elderly are more dentate. A higher number of teeth retained, however, is associated with fewer root surface caries (Vehkalahti and Paunio, 1994). 

In arrested enamel lesions, increased contents of iron (Torell, 1957a) and iron phosphate crystals (Torell, 1957b) have been observed. In pigmented dentin from carious teeth, however, no increase of iron or heavy metals has been found (Malone ef al., 1966). 

Fluorescence measurements. Table 2 shows the average fluorescence values obtained for carious and sound dentin from extracted teeth at the three excitation/emission wavelengths. 

Fluorescence measured in collagenase digests of sound and carious dentin of extracted human teeth. 

Levine RS (1972) The distribution of hydroxyproline in the dentin of carious human teeth. Arch Oral Biol 17, 127-135. 

Nkhumeleni FS, Raubenheimer EJ, Dauth J, Van Heerden WFP, Smith PD and Pitout MJ (1992) Amino acid composition of dentin in permanent human teeth. Arch Oral Biol 37, 157-158. 

Rivera EM and Yamauchi M (1993) Site comparisons of dentin collagen cross-links from extracted human teeth. Arch Oral Biol 38, 541-546. 

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