No abstract

In Part II of this study,' it was shown that altered enamel (stained,* white spot, and brown spot) is significantly less soluble than adjacent normal enamel. This result supported clinical observations that altered enamel is more resistant to caries. No direct correlation was found between decreased C02, increased nitrogen,1 or pigmentation and the extent of altered enamel dissolution.2 However, since fluoride incorporated in enamel reduces its solubility3, 4 and since decalcified areas readily imbibe fluoride,5 6 it seemed likely that the fluoride content of naturally occurring altered enamel would be high.To examine this possibility, the fluoride content was determined on treated and untreated samples of altered and adjacent normal enamel from the previous solubility study.2 Since the calcium-to-phosphorus ratio also tends to be low in altered enamel,' it seemed of interest to correlate the fluoride with the calcium and phosphorus content. As an additional dimension for chemical evaluation of altered enamel, the sodium content of the samples was also investigated. MATERIALS AND METHODSThe ground samples of altered and adjacent normal enamel on which the rate of dissolution had been reported2 were used in this study. The altered enamels (stained, white spot, and brown spot) were selected from extracted teeth of subjects who had been lifetime residents of a low-fluoride area (<0.1 p.p.m. fluoride in the communal water supply) and were separated by the age of the subject into under-and over-thirty age groups. As previously reported," 2 the altered enamel was carefully ground out with a diamond point, and the pooled grindings were collected by means of suction. Because stained enamel lesions are shallow, decalcified areast just under the enamel surface, Received for publication November 20, 1961. * Diffusely discolored smooth surface, glossy enamel, characterized by a shallow band of low mineralization just under the enamel surface (see Refs. 1 and 2).t The penetration into the enamel of 46 stained lesions-measured on soft X-rays of sections using a Neubauer fine-line disk (see Ref. 1) and on ground-out lesions by determining the focal distance of the bottom and top of the cutting with the calibrated mechanical tube of a microscopewas from 0.08 to 0.30 mm., with a mean of 0.18 + 0.12 (standard deviation). Twenty-seven randomly selected, white-spot lesions measured 0.35 ± 0.24 mm. (range 0.20-1.60 mm.) in the center and 29 brown-spot lesions, a mean of 0.71 + 0.36 mm. (range 0.20-1.60 mm.). The probability of obtaining meais in samples of this size that differ as much as the stain, white-and brown-spot groups is less than 0.01. 784 at UCSF LIBRARY & CKM on March 22, 2015 For personal use only. No other uses without permission. jdr.sagepub.com Downloaded from ALTERED AND SOUND ENAMEL. 3. FLUORIDE AND SODIUM 785the grindings from this group, sample and normal control, comprise mostly outermost enamel. White spots penetrate deeper than stain, and brown deeper than white spots." , Thus the pooled grindings from the whit...

D'scolored enamel has been thought by many investigators to be caries-resistant.1-3 If this hypothesis is correct and if caries is a product of continuous acid attack, discolored enamel should be less soluble in acid than adjacent normal enamel. The altered enamel of stained, white-spot, and brown-spot areas has been shown to be similar in degree of decalcification, density, and organic material,4 and such varieties of enamel may also exhibit similar degrees of dissolution in acid. Since these three types of altered enamel may even vary in intensity of discoloration, it seemed of interest to compare the three types of discolored enamel with adjacent normal enamel as to their relative dissolution in acid and color intensities. MATERIALS AND METHODSMaterials.-Extracted teeth were collected from patients of known age who had been lifetime residents of the same low-fluoride area (Watertown, New York). After non-abrasive cleaning, altered enamel areas were selected, using the criteria for stained, white-spot, and brown-spot areas previously described.4 The teeth were separated by age into two major categories, under and over thirty years of age, and examined microscopically for common physical characteristics.In these microscopic and visual observations, 98 per cent of the brown spots occurred on the proximal surfaces of teeth, with 90 per cent located on or under a facet. Furthermore, 80 per cent had a crack through the lesion. White spots also appeared most often on the proximal surfaces in association with facets and cracks, although a large percentage (40 per cent) were on the buccal or lingual surfaces. Usually the latter were linear extensions from restorations, decay, or deep stain. On the proximal surfaces, white-spot lesions were often next to brown spots or, by reflected light, appeared to have a slightly darkened area beneath the external surface. Microscopically, the most intense pigmentation in stained areas appeared to be in depressions on the surface, giving it the appearance of a "chicken-wire" meshwork. Patches of chipped enamel frequently disrupted the surface continuity, exposing a chalkyappearing undersurface. Striations were characteristic of all three types of altered enamel.Sampling.-The altered enamel areas were ground out with a diamond stone, and the grindings were collected on a filter, using suction as previously described.5 Adja-