Enamel, tooth

Tooth decay Tooth enamel Toothp aste... 

Dental x-rays provide valuable information on the health of teeth which cannot be obtained by any other medical imaging modaUty. Dental x-ray procedures use a piece of film placed in the mouth between the tongue and the teeth. A 60 to 70 keV source of x-rays, located outside the mouth, is directed at the film. Metal fillings attenuate x-rays striking the film and therefore appear white in a projection image. Tooth decay appears dark as it attenuates x-rays less than normal tooth enamel. 

The stiffness of pure titanium can be increased slightly by alloying alloys such as Ti—6A1—4V may be specified for partial dentures requiring additional rigidity. Titanium appHances do not tarnish or corrode in the mouth, have no metallic taste, and are easy to clean because plaque and calculus do not adhere to them. The relatively low thermal conductivity of titanium (relatively close to that of tooth enamel) gives these appHances a seemingly natural feel in the mouth and minimises thermal sensitivity (175). 

Dental abrasives range in fineness from those that do not damage tooth stmcture to those that cut tooth enamel. Abrasive particles should be irregular and jagged so that they always present a sharp edge, and should be harder than the material abraded. Another property of an abrasive is its impact strength, ie, if the particle shatters on impact it is ineffective if it never fractures, the edge becomes dull. Other desirable characteristics include the abiUty to resist wear and solvation. 

Carbides and diamond [7782-40-3] are imbedded as small particles in a binder and are used to cut tooth stmcture. Diamond chips are the hardest and most effective abrasive for tooth enamel. 

Fluorides. Most woddwide reductions in dental decay can be ascribed to fluoride incorporation into drinking water, dentifrices, and mouth rinses. Numerous mechanisms have been described by which fluoride exerts a beneficial effect. Fluoride either reacts with tooth enamel to reduce its susceptibihty to dissolution in bacterial acids or interferes with the production of acid by bacterial within dental plaque. The multiple modes of action with fluoride may account for its remarkable effectiveness at concentrations far below those necessary with most therapeutic materials. Fluoride release from restorative dental materials foUow the same basic pattern. Fluoride is released in an initial short burst after placement of the material, and decreases rapidly to a low level of constant release. The constant low level release has been postulated to provide tooth protection by incorporation into tooth mineral. 

The addition of therapeutic or cosmetic agents to dentifrices has paralleled advances in knowledge about factors affecting the human dentition. Agents added to dentifrices can act directly on the host tooth stmcture or on specific oral accumulations, for example, the principal action of fluoride is on the tooth enamel. The primary action of an abrasive, however, is on an accumulated stained pellicle. Oral accumulations of interest to preventive dentistry are dental pellicles, dental plaque, dental calculus (tartar), microbial populations responsible for oral malodor, and oral debris (food residues, leukocytes, etc). Plaque is most important because of its potential to do harm. 

Xylitol is used as a sweetener in many foods, including low-calorie candies, gums, and breath mints. It prevents bacteria from adhering to cells in the mouth and gums. It also binds to calcium and aids in remineralizing tooth enamel and bones. 

Stannous fluoride is used in toothpastes and dental rinses to protect tooth enamel from attack by bacteria—cavities (also known as dental caries). It was the first fluoride used for that purpose, in the toothpaste Crest. 

Tooth enamel is a hydroxyapatite, Ca5(P04)30H. Tooth decay begins when acids attack the enamel ... 

The addition of fluoride ions to domestic water supplies (in the form of NaF) is now widespread and has resulted in a dramatic decrease in dental cavities. Fluoridated toothpastes, containing either tin(II) fluoride or sodium monofluorophos-phate (MFP, Na2FP03), are also recommended to strengthen tooth enamel. 

The 8 C values of the Preclassic humans at Cuello (Table 2.1) average -12.9 0.9%o (n = 28) in collagen, -9.8 1.0 in bone apatite (n = 16), and -8.7 2.3%o in tooth enamel apatite (n = 33) the S N values in collagen average 8.9 1.0%o (n = 23). The discrepancy in the number of specimens is due to the fact that more teeth were available than post-cranial material, while some of the specimens contained insufficient collagen to measure the nitrogen isotope ratios. Additional bone apatite analyses are in progress. 

Tykot, R.H., van der Merwe, N.J. and Hammond, N. 1996 Stable isotope analysis of bone collagen, bone apatite, and tooth enamel in the reconstruction of human diet. A case study from Cuello, Belize. In Orna, M.V., ed., Archaeological Chemistry Organic, Inorganic, and Biochemical Analysis. ACS Symposium Series 625, Washington, DC, American Chemical Society 355-365. 

Wright, L.E. and Schwarcz, HP. 1998 Stable carbon and oxygen isotopes in human tooth enamel identifying breastfeeding and weaning in prehistory. American Journal of Physical Anthropology 106 1-18. 

Hedges, R.E.M., Eee-Thorp, J.A. and Tuross , N.C. 1995 Is tooth enamel earbonate a suitable material for radiocarbon dating Radiocarbon 37 285-290. 

Figure 5.6. 5 C data for browsers and grazers from Border cave, plotted against age (vertical scale). The shaded areas represent the 5 C values of modem grazers and browsers. Filled squares and circles are tooth enamel the open square is bone. The chronology obtained from ESR measurements of faunal enamel has been used hence the sequence appears somewhat younger than outlined previously (Grun et al. 1990 Beaumont et al. 1978). The sequence is in fact longer, but no isotopic data are available beyond Stratum IGBS.LRA ( 80Ka).

Cerling, T., Harris, J.M., Ambrose, S.H., Leakey, M.G. and Solounias, N. 1998 Dietary and environmental reconstruction with stable isotope analyses of herbivore tooth enamel from the Miocene locality of Fort Tsmaa. Journal of Human Evolution 33 635-650. 

Michel, V., Ildefonse, P. and Morin, G. 1995 Chemical and structural changes in Cervus elephus tooth enamels during fossilization (Lazaret Cave) a combined IR and XRD Rietveld analysis. Applied Geochemistry 10 145-159. 

Rink, W.J. and Schwarcz, H.P. 1995 Tests for diagenesis in tooth enamel ESR dating signals and carbonate contents. Journal of Archaeological Science 22 251-255. 

Figure 6.3. 5 "0 in surface water (data from Gat 1980) compared with that in biogenic phosphates of various mammals from many world regions (data shown in squares are from conventional phosphate analyses Longinelli 1984 Luz et al. 1984 Ayliffe and Chivas 1990 D Angela and Longinelli 1990 Yoshida and Miyazaki 1991 Huertas et al. 1995). For comparison, plotted as filled circles, are 8 0 values for tooth enamel analyzed by laser fluorination (six humans, one shark, and one wolf Kohn et al. 1996). 

Bone and tooth enamel from modem animals were collected in 1984 and 1993 from skeletons exposed on the surface in Sibiloi National Park, located on the east shore of Lake Turkana in northern Kenya. In addition to its interest as the site of numerous fossil hominid discoveries, the Turkana area provides an ideal controlled situation for the present study. The park is a circumscribed area surrounded by human pastoral groups and the nondomestic fauna remain to a great extent within its confines. Water sources are limited to the lake, ephemeral streams, a limited number of waterholes, and the plants eaten by the animals. The streams last on the order of days and in dry years do not flow at all. The non-domestic animals from which the bone and enamel were collected likely obtained most of their drinking water from the lake itself Domestic animals entered the park in 1984 during a severe drought. Their drinking water sources may have varied widely. 

Tooth enamel precipitated as silver phosphate and reacted via this method gave values similar to corrected laser data from aliquots of the same tooth enamel (Table 6.1). Thus, the data from the crocodile samples are considered directly comparable with the data from the mammal tooth enamel. 

Table 6.2. Phosphate 8 0 and collagen 5 C values of tooth enamel and bone of mammals from Sibiloi National Park, East Turkana, Kenya.

Figure 6.5. 5 0 of tooth enamel phosphate versus body size (log scale) for Kenyan fauna analyzed in this study. With the exception of the dikdik, there is a general association between the two variables. In contrast to tbe body-size model (Bryant and Froelicb 1995) wbicb predicts a range of values close to l%o, however, the measured range in 8 0 values for species averages is 5%a. This and the anomalous values for the dikdik reflect physiological and behavioral adaptations by these desert adapted species. 

This equation predicts a value of 26.8%ofor the zebra at Turkana assuming an average value of 6%o for Lake Turkana water. This predicted value is l%o less than the actual value of 27.8%o. Given the variation in methods of sample preparation and analysis, variation between bone and tooth enamel (Stuart-Williams and Schwarcz 1997), and uncertainty in surface water oxygen isotopic composition, these values are extraordinarily close. Alternatively, if the equation is solved for using the actual value of the Turkana zebra. 

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