Abstract/Summary

This thesis explores approaches to improving the retention of oral care formulations in the oral cavity to improve flavour and active ingredient retention whilst also developing methodologies to measure this. The addition of mucoadhesive polymers into oral care formulations and how their inclusion affects the residency time of the formulation and the flavour compounds incorporated into them will be explored in this thesis. Understanding how mucoadhesion works and the benefits of including compounds with known mucoadhesive properties into pharmaceutical formulations is key to putting this work into context. The principles and theories behind mucoadhesion are detailed in this section and a brief look at the history of toothpastes to lay the foundation of the work carried out. The work described in this thesis has been divided into three sections. Chapter 1 & 2 contains the brief Introduction and Background to the work, with Chapters 3, 4 & 5 detailing preparation, characterisation and profiling of materials produced with Chapter 6 concluding this work. Chapter 1 provides a summary of toothpaste and its history, looking at how primitive pastes and powders developed into the complex and multifunctional formulations that have become a necessity in maintaining oral health worldwide, a background on what is mucoadhesion, the theories by which it works and how its use in oral care formulations could be beneficial and improve the retention of flavour compounds and active ingredients. Chapter 2 is a literature review that looks in detail at the structure of the oral cavity, the mucosal surfaces present and how plaque bacteria grows and coats enamel surfaces. An in depth look at the components such as fluorides, binders and surfactants that make up a formulation and their roles is also looked at. The physical characteristics of oral care products such as their rheology, retention & texture are examined with future challenges faced in further developing improved oral care formulations and some strategies for overcoming issues currently faced being finally discussed. Chapter 3 describes the formulation of novel toothpastes based on various mucoadhesive polymers, their characterisation by rheology, texture analysis, fluorescent imaging and wash off test. Additionally, this chapter looks at the development of methods to measure retention of formulations in the oral cavity, allowing a more detailed view of how they behave and a look at the surfaces they adhere to. Formulation of novel toothpaste with longer retention time and improved texture analysis results than commercially available toothpaste was achieved and lead the way to sensory testing. Chapter 4 describes the sensory profiling of the novel formulations, with commercial and novel formulations tested by a trained sensory panel. The toothpastes were first profiled by the panel to ascertain the flavour and physical characteristics of each toothpaste. This was followed by a quantitative descriptive analysis study to find out what parameters were to be measured in the temporal study. Finally, in the fixed time point temporal, breath samples were analysed by GC/MS with scores from the panellist to measure the retention of volatile organic compounds found in peppermint flavouring in toothpaste. Chapter 5 describes the synthesis of silica particles with surfaces modified with monomers and chitosan. Their synthesis, characterisation and testing of their mucoadhesive properties as toothpaste formulations was conducted and formulations with the ability to retain for longer on mucosal surfaces were produced. Chapter 6 concludes this thesis and discusses future work that can be built upon from this project.