Indiana University-Purdue University Indianapolis (IUPUI) / Purpose: The primary objective of this laboratory study was to investigate whether the ability of SDF to remineralize caries lesion is modulated by their baseline mineral distribution. The exploratory objective was to determine whether the staining caused by SDF is modulated by lesion mineral distribution. Materials and methods: This in vitro study utilized bovine permanent enamel specimens. SDF was compared to the clinical reference standard, 5% sodium fluoride varnish (FV), and deionized water (DIW) was the negative control. By utilizing three lesion creation protocols (methylcellulose [MeC], hydroxyethylcellulose [HEC], Carbopol [C907]), artificial caries lesions with different mineral distributions (n=20 per subgroup) were created in the enamel specimens Interventions were applied and the lesions remineralized using artificial saliva. Changes in mineral loss, lesion depth, mineral density of the surface zone, and lesion mineral distribution were determined using transverse microradiography. Throughout the study, color of the lesion and changes thereof were measured using a spectrophotometer. Data were analyzed by using two-way ANOVA. Pair-wise comparisons were performed using Fisher’s Protected Least Significant Differences to control the overall significance level at 5%. Results: For changes in mineral loss, DIW in MeC showed significantly greater change (more remineralization) than both SDF (p<0.01) and FV (p=0.01), which were not different from one another (p=0.13). There were no statistically significant differences between SDF and FV in the other lesions (C907 – p=0.18; HEC – p=0.56). For changes in lesion depth, there was no statistically significant interaction between study factors lesion protocol and treatments (p=0.23) as well as the individual factors lesion protocols (p=0.08) and treatments (p=0.82). For changes in surface zone mineral density, SDF showed significant change in mineral density compared to FV (p=0.02); however, SDF was not different from with DIW (p=0.25). For lesion mineral distribution, MeC exhibited the greater mineral loss in the lesion body and lowest mineral density at the surface zone. HEC lesions were the deepest but exhibited modest differences in mineral loss between the lesion body and the surface zone. C907 lesions were somewhat between MeC and HEC. SDF in MeC had the highest mineral gain in the surface zone, while DIW resulted in the highest mineral gain in the lesion body. SDF in HEC showed the highest mineral gain in the surface area compared to FV and DIW, with all treatments resulting in the largest mineral gain to a similar extent in the lesion body. In C907, SDF showed the most mineral gain in the lesion body compared to DIW and FV, while differences in the surface zone between treatments were less pronounced. For color changes post intervention, SDF showed more darkening in C907 and HEC lesions compared to MeC (p<0.01) and compared to FV and DIW. For post remineralization, SDF treated C907 lesions became significantly whiter (p<0.01) compared to SDF in MeC and HEC which continued to get darker. Conclusion: SDF did exhibit different remineralization abilities and behaviors and the modulation was based on lesion baseline mineral distribution. Staining resulting from SDF treatment varied significantly based on lesion mineral distribution.

Clays and clay mineral distribution studies are important for understanding the geological history of the Gulf of Mexico Basin, but few studies document any subsurface clay mineral distribution in the Gulf of Mexico. Shale samples from nine wells (30 samples) in the South Timbalier protraction were selected near known paleontological markers identifying the Miocene, Pliocene, and Pleistocene boundaries. Bulk mineralogy of each sample, determined by XRD, is primarily mixed-layer smectite and illite with a minor amount of kaolinite. The mixed-layer mineralogies are end-member smectite, mixed-layer smectite, mixed-layer illite, and end-member illite. These clay mineral fractions do not correlate with age. The illite mixed layer percentage correlates with depth, but the correlation decreases when depth is converted to temperature. However, the illite mixed layer fraction does not exhibit a strong correlation in this multiwell study when compared to a single well study in Ship Shoal using identical methods (Totten et al., 2002).