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Surface Dissolution and Nucleation Processes Alexander Stuart Parker

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Surface Dissolution and Nucleation Processes Alexander Stuart Parker A Thesis Submitted for the Degree of PhD at the University of Warwick Permanent WRAP URL: http://wrap.warwick.ac.uk/88282 Copyright and reuse: This thesis is made available online and is protected by original copyright. Please scroll down to view the document itself. Please refer to the repository record for this item for information to help you to cite it. Our policy information is available from the repository home page. For more information, please contact the WRAP Team at: [email protected] warwick.ac.uk/lib-publications Quantitative Crystal Investigations: Surface Dissolution and Nucleation Processes Alexander Stuart Parker Thesis submitted for the degree of Doctor of Philosophy Electrochemistry and Interfaces Group, Department of Chemistry, University of Warwick. June 2016 For my loving family i Quantitative Crystal Investigations: Surface Dissolution and Nucleation Processes Alexander Stuart Parker I. Table of Contents I. TABLE OF CONTENTS ____________________________________________ II II. LIST OF FIGURES ____________________________________________ VII III. LIST OF TABLES _____________________________________________ XIII IV. DECLARATION AND INCLUSION OF PUBLISHED WORK _____________XIV V. ACKNOWLEDGEMENTS _______________________________________XVI VI. DEFINITION OF ACRONYMS __________________________________ XVII VII. GLOSSARY OF SYMBOLS ______________________________________ XIX VIII. ABSTRACT _________________________________________________ XX 1 INTRODUCTION ________________________________________________ 2 1.1 SURFACE SCIENCE_____________________________________________ 3 1.2 ENAMEL ___________________________________________________ 4 1.2.1 Structure of the Tooth ____________________________________ 4 1.2.2 Prevalence of acid dissolution in the oral cavity ________________ 8 1.2.3 Introduction to Acid Erosion and Remineralisation _____________ 9 1.2.4 Enamel Dissolution ______________________________________ 12 1.2.5 Enamel Dissolution Inhibitors _____________________________ 16 1.2.6 Enamel summary _______________________________________ 17 1.3 CALCIUM CARBONATE CRYSTALS __________________________________ 18 ii 1.3.1 Applications of Crystal Nucleation, Growth and Dissolution _____ 22 1.3.2 Crystal Nucleation Theory ________________________________ 24 1.3.3 Polymorphism __________________________________________ 27 1.3.4 Applications to CaCO3 ___________________________________ 30 1.3.5 Confinement of crystal growth ____________________________ 32 1.3.6 Calcium Carbonate growth inhibition _______________________ 33 1.4 MASS TRANSPORT AND SURFACE REACTION KINETICS ___________________ 36 1.5 TECHNIQUES FOR SURFACE ANALYSIS _______________________________ 37 1.5.1 Optical Microscopy ______________________________________ 37 1.5.2 SPM Methods __________________________________________ 38 1.5.3 Field Emission Scanning Electron Microscopy (FE-SEM) _________ 54 1.5.4 Micro-Raman Microscopy ________________________________ 55 1.6 FINITE ELEMENT METHOD (FEM) MODELLING _________________________ 57 1.7 CHEMICALS, INSTRUMENTATION AND METHODS _______________________ 59 1.8 THESIS AIMS _______________________________________________ 60 2 COMBINATORIAL LOCALIZED DISSOLUTION ANALYSIS: APPLICATION TO ACID-INDUCED DISSOLUTION OF DENTAL ENAMEL AND THE EFFECT OF SURFACE TREATMENTS ____________________________________________________________ 64 2.1 ABSTRACT _________________________________________________ 64 2.2 INTRODUCTION _____________________________________________ 65 2.3 EXPERIMENTAL DETAILS ________________________________________ 69 2.3.1 Solutions ______________________________________________ 69 2.3.2 Enamel Sample Preparation ______________________________ 70 2.3.3 SECCM method _________________________________________ 72 2.3.4 Atomic Force Microscopy _________________________________ 76 2.4 THEORY AND SIMULATIONS _____________________________________ 76 iii 2.5 RESULTS AND DISCUSSION ______________________________________ 81 2.5.1 Etch Pit analysis ________________________________________ 81 2.5.2 Simulations ____________________________________________ 86 2.5.3 Determination of dissolution kinetics _______________________ 87 2.6 CONCLUSIONS ______________________________________________ 89 3 MEASUREMENT OF THE EFFICACY OF CALCIUM SILICATE FOR THE PROTECTION AND REPAIR OF DENTAL ENAMEL ________________________________ 92 3.1 ABSTRACT _________________________________________________ 92 3.1.1 Objectives: ____________________________________________ 92 3.1.2 Methods: _____________________________________________ 92 3.1.3 Results: _______________________________________________ 93 3.1.4 Conclusions: ___________________________________________ 93 3.1.5 Clinical Significance _____________________________________ 93 3.2 INTRODUCTION. _____________________________________________ 94 3.3 MATERIALS AND METHODS _____________________________________ 98 3.3.1 Calcium release from calcium silicate _______________________ 98 3.3.2 HAP formation from calcium silicate ________________________ 98 3.3.3 Scanning electrochemical cell microscopy (SECCM) ____________ 99 3.3.4 Deposition of calcium silicate onto sound and eroded enamel surfaces _________________________________________________ 102 3.3.5 Deposition of calcium silicate to eroded enamel pits __________ 103 3.3.6 Protection of enamel by calcium silicate and fluoride _________ 104 3.4 RESULTS _________________________________________________ 106 3.4.1 Calcium release from calcium silicate ______________________ 106 3.4.2 HAP formation from calcium silicate _______________________ 108 iv 3.4.3 Deposition of calcium silicate onto sound and eroded enamel surfaces _________________________________________________ 111 3.4.4 Deposition of calcium silicate to eroded enamel pits __________ 111 3.4.5 Protection of enamel by calcium silicate and fluoride _________ 114 3.5 DISCUSSION ______________________________________________ 117 3.6 CONCLUSIONS _____________________________________________ 120 4 CONTROLLED CRYSTALLIZATION IN A NANOPIPETTE ________________ 122 4.1 ABSTRACT ________________________________________________ 122 4.2 INTRODUCTION ____________________________________________ 123 4.3 MATERIALS AND METHODS ________________________________ 128 4.3.1 Solutions. ____________________________________________ 128 4.3.2 Nanopipettes. _________________________________________ 128 4.3.3 Pipette Characterization ________________________________ 129 4.3.4 Instrumentation. ______________________________________ 129 4.3.5 Bias Driven Crystallization Experiments. ____________________ 130 2+ 4.3.6 Variation of Ca concentration in the bath solution __________ 132 2- 4.3.7 Effect of inverting the tip and bath species whilst varying of CO3 concentration in the bath solution ____________________________ 133 4.3.8 FEM Simulations. ______________________________________ 134 4.3.9 Raman Spectroscopy. ___________________________________ 136 4.4 RESULTS AND DISCUSSION _________________________________ 137 4.4.1 Initial Experiments _____________________________________ 137 4.4.2 Growth of Calcium Carbonate in a Nanopipette ______________ 138 4.4.3 Mixing of CaCO3 in a Nanopipette _________________________ 141 4.4.4 Quantifying Growth Rates in a Nanopipette _________________ 145 4.4.5 The Effect of Applied Bias on Blocking Rates ________________ 149 v 4.4.6 Inhibitor Studies Using a Nanopipette ______________________ 151 4.5 CONCLUSIONS ___________________________________________ 154 5 CONCLUSIONS _______________________________________________ 158 6 BIBLIOGRAPHY _______________________________________________ 162 vi II. List of figures FIGURE 1 SHOWING MODEL STRUCTURE OF TOOTH AND ROD STRUCTURE. WHITE SHOWS ENAMEL, YELLOW SHOWS DENTINE AND RED SHOWS PULP AND NERVE TISSUE ......................................................... 5 FIGURE 2 SHOWING AFM IMAGE OF A. ACID ERODED AND B. HIGHLY POLISHED ENAMEL SURFACE WHICH REVEALS THE INTERLOCKING ROD STRUCTURE. DATA COLLECTED BY THE AUTHOR ............................. 7 FIGURE 3 SHOWING EFFECT OF ACID ON POLISHED ENAMEL USING INTERFEROMETRY TO SHOW THE BOUNDARY BETWEEN ACID ETCHED PART OF AN ENAMEL SAMPLE AND UNTREATED ENAMEL. CLOSE UP IMAGED PRODUCED FROM AFM ............................................................................................ 9 FIGURE 4 SHOWING THE VARIOUS STAGES OF DISSOLUTION AND THE AREAS OF KINETIC AND MASS TRANSPORT LIMITS ............................................................................................................................ 14 FIGURE 5 FREE ENERGY DIAGRAM FOR NUCLEATION ......................................................................... 25 FIGURE 6 SHOWING ENERGY CHANGE DIAGRAM OF METASTABLE AND THERMODYNAMIC CRYSTALS ........... 29 FIGURE 7 AFM EXPERIMENT SET UP ............................................................................................. 40 FIGURE 8 SHOWING A TYPICAL FORCE CURVE MEASURED USING AFM .................................................. 42 FIGURE 9 OPERATION OF TAPPING MODE AFM ............................................................................... 43 FIGURE 10 SHOWING AN AFM TIP INTERATING WITH A SHARP FEATURE WHICH WOULD CREATE A FALSE IMMAGE ......................................................................................................................... 44 FIGURE 11 SHOWING SERIES OF AFM LINE PROFILES AT VARIOUS TIMES OF AN ARRAY OF ACID ETCHED PITS ON A) POLISHED ENAMEL B) FLUORIDE TREATED POLISHED ENAMEL ...........................................
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