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...

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By comparing phosphorus loss from enamel windows during successive exposures in acetic acid buffer, measurements were made of the effects of a number of uncommon fluoride and nonfluoride compounds on enamel dissolution. Acidulated ytterbium chloride and the tetrafluorides of titanium, zirconium, and hafnium gave much more lasting protection against the action of acid than did the fluorides commonly used for caries prophylaxis.

An epidemiologic investigation to reliably identify caries-susceptible subjects by microbiological and chemical assessment of plaque and saliva is currently in progress. As part of that study, the numerical relationships of mutans streptococci, lactobacilli and total viable microflora in plaque and saliva among 12- to 15-year-old children in a fluoridated community were determined. Paraffin-stimulated whole saliva and pooled dental plaque were collected. Each sample was suspended in reduced transport fluid, chilled on ice, and assayed. The bivariate normal distribution was found to be a suitable model for the distribution of the pairs [numbers of bacteria in plaque (log₁₀), numbers of bacteria in saliva (log₁₀)]. Statistically significant positive correlations were found between numbers of mutans streptococci in plaque and saliva, and between lactobacilli in plaque and saliva.