Browsing by Author "Butler, A."

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    Characteristics of Methylcellulose Acid Gel Lesions Created in Human and Bovine Enamel
    (Karger, 2013-01) Lippert, Frank; Butler, A.; Lynch, R. J. M.; Department of Cariology, Operative Dentistry and Dental Public Health, School of Dentistry
    Acid gel caries lesions were created in 3,100 human and bovine enamel specimens and studied with transverse microradiography. Small, significant differences were found. Human enamel lesions were found to be less demineralized, shallower, had a higher ratio of integrated mineral loss (ΔZ) to lesion depth (L), a lower degree of surface zone mineralization (SZmax) and showed less variability than those in bovine enamel. SZmax showed the highest variability. Between tissues, L differed the most, ΔZ the least. Biological variation within bovine enamel is perhaps not only bigger than previously assumed, it may also overshadow any structural and chemical differences between tissues.
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    Effect of Fluoride, Lesion Baseline Severity and Mineral Distribution on Lesion Progression
    (Karger, 2012) Lippert, Frank; Butler, A.; Lynch, R. J. M.; Hara, Anderson T.; Department of Cariology, Operative Dentistry and Dental Public Health, School of Dentistry
    The present study investigated the effects of fluoride (F) concentration, lesion baseline severity (ΔZbase) and mineral distribution on lesion progression. Artificial caries lesions were created using three protocols [methylcellulose acid gel (MeC), hydroxyethylcellulose acid gel (HEC), carboxymethylcellulose acid solution (CMC)] and with low and high ΔZbase groups by varying demineralization times within protocols. Subsequently, lesions were immersed in a demineralizing solution for 24 h in the presence of 0, 1, 2 or 5 ppm F. Changes in mineral distribution characteristics of caries lesions were studied using transverse microradiography. At baseline, the protocols yielded lesions with three distinctly different mineral distributions. Secondary demineralization revealed differences in F response between and within lesion types. In general, lowΔZ lesions were more responsive to F than highΔZ lesions. LowΔZ MeC lesions showed the greatest range of response among all lesions, whereas highΔZ HEC lesions were almost unaffected by F. Laminations were observed in the presence of F in all but highΔZ HEC and CMC lesions. Changes in mineral distribution effected by F were most pronounced in MeC lesions, with remineralization/mineral redeposition in the original lesion body at the expense of sound enamel beyond the original lesion in a dose-response manner. Both ΔZbase and lesion mineral distribution directly impact the F response and the extent of secondary demineralization of caries lesions. Further studies – in situ and on natural white spot lesions – are required to better mimic in vivo caries under laboratory conditions.
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    Enamel demineralization and remineralization under plaque fluid-like conditions – a QLF study
    (Karger, 2011) Lippert, Frank; Butler, A.; Lynch, R. J. M.; Department of Cariology, Operative Dentistry and Dental Public Health, School of Dentistry
    The present study investigated de- and remineralization in enamel lesions under plaque fluid (PF)-like conditions using quantitative light-induced fluorescence (QLF). Preformed lesions were exposed to partially saturated lactic acid solutions, varying in pH and fluoride concentration ([F]) based on a 5 × 3 factorial study design (0/0.1/0.5/1.5/4 ppm F; pH 4.9/5.2/5.5). Average fluorescence loss (ΔF) was monitored for 11 days. Subsequently, lesions were demineralized in a partially saturated acetic acid solution for two 24-hour periods. Data were analyzed using repeated measures analysis of covariance. Lesions exposed to PF at 4 ppm F and pH 5.5 showed not only the most remineralization (ΔΔF = 28.2 ± 14.0%) for all groups after 11 days, but also the most demineralization (ΔΔF = –19.3 ± 13.5%) after subsequent acetic acid exposure. Increased [F] resulted in more remineralization, regardless of pH. Higher pH values resulted in more remineralization. No remineralization was observed in lesions exposed to F-free solutions, regardless of pH. Remineralization was noticeable under the following conditions: pH 4.9 – [F] = 4 ppm, pH 5.2 – [F] ≧ 1.5 ppm, and pH 5.5 – [F] ≧ 0.5 ppm. Overall, [F] had a stronger effect on remineralization than pH. Subsequent demineralization showed that little protection was offered by PF-like solutions, and further demineralization compared with baseline was observed on lesions not remineralized initially. [F] had a stronger effect on net mineral change than pH. The present study has shown that QLF is a valuable tool in studying lesion de- and remineralization under PF-like conditions, where [F] was shown to be more important than pH.