EFFECT OF POLISHING PROTOCOL AND EXPOSURE TO STAINING SOLUTIONS ON THE COLOUR STABILITY OF DENTAL COMPOSITE MATERIALS Chamunorwa Marufu BDS (UZ) V/60/88169/2016 Thesis Submitted in Partial Fulfilment of the Requirements for a Masters Degree in Prosthodontics of the University of Nairobi November 2019 DECLARATION OF ORIGINALITY I, Dr. Chamunorwa Marufu, student number V60/88169/2016, of College of Health Sciences, School of Dental Sciences, Department of Conservative and Prosthetic Dentistry, declare that this thesis titled “EFFECT OF POLISHING PROTOCOL AND EXPOSURE TO STAINING SOLUTIONS ON THE COLOUR STABILITY OF DENTAL COMPOSITE MATERIALS” is my original work. Where other people’s work has been used it has been properly referenced and acknowledged according to the University of Nairobi requirements. I have not allowed and shall not allow anyone to copy my work with the intention of passing it off as her/his own work. I understand that any false claim in respect to this thesis report shall result in disciplinary action in accordance to the University of Nairobi Plagiarism policy. Signed……………………………………. Date ……………………………………. ii SUPERVISORS’ APPROVAL Dr. Bernina K. Kisumbi, BDS (Nbi), MPhil. (Manchester). FICD Department of Conservative and Prosthetic Dentistry, School of Dental Sciences, University of Nairobi Signed……………………………………. Date ……………………… Dr. Olivia Osiro, BDS (Nbi), MSc (London) Department of Conservative and Prosthetic Dentistry, School of Dental Sciences, University of Nairobi Signed……………………………………. Date ……………………… Dr. Fred Otieno, BDS (Nbi), MSc (Newcastle – Upon Tyne) Department of Conservative and Prosthetic Dentistry, School of Dental Sciences, University of Nairobi Signed……………………………………. Date ……………………… iii DEDICATION This work is dedicated to my wife, Fortunate, and our daughter, Rujeko for their love and support. iv ACKNOWLEDGEMENTS First, I thank the Almighty for the strength to complete this thesis. I would also like to thank the following people: My supervisors Dr. B.K Kisumbi, Dr. O. Osiro and Dr. F. Otieno of the University of Nairobi, School of Dental Sciences, Department of Conservative and Prosthetic Dentistry, for their guidance during all aspects of this thesis Dr E.A.O. Dimba of the University of Nairobi, School of Dental Sciences, Department of Oral Pathology, for assistance in formulating the protocol for khat plant extract and overseeing the process. The staff from the School of Pharmacy, Pharmaceutical Chemistry lab at the University of Nairobi, Mr O.K. King’ondu and Mr J Malukumbi for assistance in processing the khat plant extract. Mr. Desmond K’Owino of the School of Dental Sciences, University of Nairobi, who helped me with the data analysis. v TABLE OF CONTENT DECLARATION OF ORIGINALITY ........................................................................... ii DEDICATION.................................................................................................................. iv ACKNOWLEDGEMENTS ............................................................................................. v LIST OF FIGURES .......................................................................................................... x LIST OF TABLES .......................................................................................................... xii LIST OF ABBREVIATIONS ........................................................................................ xv DEFINITION OF TERMS........................................................................................... xvii ABSTRACT .................................................................................................................. xviii CHAPTER ONE: INTRODUCTION ............................................................................. 1 1.1 Dental resin composites ................................................................................................ 1 1.2 Importance of aesthetic dentistry .................................................................................. 1 1.3 Comparison of available aesthetic dental restorations .................................................. 2 1.4 Factors that influence colour stability of dental resin composites ................................ 2 1.5 Finishing and polishing of composite restorations ....................................................... 3 CHAPTER TWO: LITERATURE REVIEW ................................................................ 4 2.1 Introduction ................................................................................................................... 4 2.2 Dental resin composites ................................................................................................ 4 2.2.1 Macrofills .............................................................................................................. 6 2.2.2 Hybrid and microhybrid composites ...................................................................... 6 2.2.3 Microfills................................................................................................................ 6 2.2.4 Nanocomposites ..................................................................................................... 7 2.3 Colour stability of resin composites ............................................................................. 7 2.3.1 Intrinsic discolouration .......................................................................................... 7 2.3.2 Extrinsic discolouration ......................................................................................... 8 2.4 Finishing and polishing ................................................................................................. 9 2.5 Review of staining solutions for the study .................................................................. 10 2.5.1 Khat ...................................................................................................................... 10 2.5.2 Tea........................................................................................................................ 12 2.5.3 Red wine .............................................................................................................. 13 2.6 Staining technique ....................................................................................................... 13 vi 2.6.1 Immersion in staining solutions ........................................................................... 13 2.6.2 Accelerated aging................................................................................................. 14 2.7 Colour measurement ................................................................................................... 14 CHAPTER THREE: PROBLEM STATEMENT, STUDY JUSTIFICATION AND OBJECTIVES ................................................................................................................. 19 3.1 Problem statement ....................................................................................................... 19 3.2 Justification of the study ............................................................................................. 19 3.3 Objectives ................................................................................................................... 20 3.3.1 Broad objectives................................................................................................... 20 3.3.2 Specific objectives ............................................................................................... 20 3.4 Hypothesis................................................................................................................... 20 3.4.1 Null hypothesis .................................................................................................... 20 3.4.2 Alternative hypothesis ......................................................................................... 21 3.5 Variables ..................................................................................................................... 21 CHAPTER FOUR: MATERIALS AND METHODS ................................................. 22 4.1 Study design ................................................................................................................ 22 4.2 Study sample ............................................................................................................... 22 4.3 Sample size calculation ............................................................................................... 22 4.4 Preparation of resin composite specimens .................................................................. 23 4.5 Specimen fabrication .................................................................................................. 25 4.6 Polishing groups and procedures ................................................................................ 26 4.6.1 Mylar strip finish.................................................................................................. 26 4.6.2 Soflex contouring and polishing discs finish ....................................................... 27 4.6.3 White polishing stone burs finish ........................................................................ 27 4.7 Preparation of staining solutions ................................................................................. 28 4.7.1 Tea........................................................................................................................ 30 4.7.2 Khat extract .........................................................................................................