Combinatorial localized dissolution analysis: Application to acid-induced dissolution of dental enamel and the effect of surface treatments

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• 作者：Alexander S. Parker^a ; ¹ ; Rehab Al Botros^a ; ¹ ; Sophie L. Kinnear^a ; Michael E. Snowden^a ; Kim McKelvey^a ; Alexander T. Ashcroft^b ; Mel Carvell^b ; Andrew Joiner^b ; Massimo Peruffo^b ; Carol Philpotts^b ; Patrick R. Unwin^a ; ^{p.r.unwin@warwick.ac.uk" class="auth_mail" title="E-mail the corresponding author}
• 关键词：SECCM ; scanning electrochemical cell microscopy ; AFM ; atomic force microscopy ; FEM ; finite element method ; HAP ; calcium hydroxyapatite ; QRCE ; quasi reference counter electrode ; TEM ; transmission electron microscopy ; SEM ; scanning electron microscopy ; ppm ; parts per million ; rms ; root mean squared ; ANOVA ; analysis of variance
• 刊名：Journal of Colloid and Interface Science
• 出版年：2016
• 出版时间：15 August 2016
• 年：2016
• 卷：476
• 期：Complete
• 页码：94-102
• 全文大小：2095 K

文摘

A combination of scanning electrochemical cell microscopy (SECCM) and atomic force microscopy (AFM) is used to quantitatively study the acid-induced dissolution of dental enamel. A micron-scale liquid meniscus formed at the end of a dual barrelled pipette, which constitutes the SECCM probe, is brought into contact with the enamel surface for a defined period. Dissolution occurs at the interface of the meniscus and the enamel surface, under conditions of well-defined mass transport, creating etch pits that are then analysed via AFM. This technique is applied to bovine dental enamel, and the effect of various treatments of the enamel surface on acid dissolution (1 mM HNO₃) is studied. The treatments investigated are zinc ions, fluoride ions and the two combined. A finite element method (FEM) simulation of SECCM mass transport and interfacial reactivity, allows the intrinsic rate constant for acid-induced dissolution to be quantitatively determined. The dissolution of enamel, in terms of Ca²⁺ flux (j_Ca²⁺$j_{{\text{Ca}}^{2+}}$), is first order with respect to the interfacial proton concentration and given by the following rate law: j_Ca²⁺=k₀[H⁺]$j_{{\text{Ca}}^{2+}}=k_0[{\text{H}}^{+}]$, with k₀=0.099±0.008$k_0=0.099\pm 0.008$ cm s⁻¹. Treating the enamel with either fluoride or zinc ions slows the dissolution rate, although in this model system the partly protective barrier only extends around 10–20 nm into the enamel surface, so that after a period of a few seconds dissolution of modified surfaces tends towards that of native enamel. A combination of both treatments exhibits the greatest protection to the enamel surface, but the effect is again transient.