Mechanisms by which titanium tetrafluoride (TiF4) reduces enamel solubility were investigated. An association was found between solubility reduction and the formation of a glaze on the enamel surface. Also, TiF4-treated enamel had higher levels of fluoride than enamel treated with acidulated phosphate-sodium fluoride. Solubility reductions and fluoride levels decreased slightly with washing but after 48 hours the fluoride level was still 60% of the maximum, and solubility reductions ranged between 64 and 70%.In previous work,' it was shown that titanium tetrafluoride (TiF4) treatment of enamel gave greater reductions of enamel solubility and greater protection against animal caries than did comparable use of other fluorides. These indications of the potential caries-preventive value of TiF4 prompted further study of its effects on enamel. During these latter studies, we observed that TiF4-treated enamel often acquired a glazelike appearance. This raised the question of the extent to which the uniquely high solubility-reducing effect of TiF4 might be dependent on reactions associated with the "glaze" formation or on the fluoride content of TiF4-treated enamel.To obtain information on these questions, experiments were undertaken to indicate the conditions under which the TiF4 glaze formed on enamel, the fluoride content of TiF4-treated enamel, and the relationship of these to the observed reductions in enamel going into solution. Materials and MethodsIn vitro effects on enamel dissolution were measured by the previously described' 'window' technique, in which windows made on unground bovine enamel surfaces are exposed to a series of 15-minute acid decalcifixations in 20 ml 0.1 M acetic acid buffer (HAc), pH 4. The difference in amounts of phosphorus2 in the decalcifying buffer before and after treatment of the enamel with TiF4 or other agents gave a measurement of effects on enamel solubility.The glaze that appeared on the enamel, particularly after topically applied TiF4 followed by application of 0.1 M HAc, was given a visual rating of from 0 to ++++. This glaze produced seemingly whiter enamel and appeared on ground and unground human enamel, and on unground bovine enamel surfaces.To obtain information on the factors influencing glaze formation and the extent to which the glaze determined solubility reduction, glazes of different grades (0 to ++++) formed under various conditions were compared with solubility findings. For this purpose, different agents were used with TiF1 on normal bovine enamel, ethylenediamine-extracted "anorganic" enamel, and "organic-exposed" enamel. The ethylenediamine (ED)-extracted enamel was prepared by refluxing for 2.5 or 20 hours in a Soxhlet apparatus at 118 C.3 Organic-exposed enamel refers to the incompletely EDextracted enamel4 that was etched for two minutes with 0.3%l HCl, thereby exposing the underlying organic material in the partially anorganic enamel. Solubility changes were measured by the window technique.To indicate whether the high solubility reductions given by TiF4, w...

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...

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