ACKNOWLEDGEMENTS In the name of ALLAH, most Gracious, most Merciful, the first Who deserves all thanks and appreciation for everything and for providing me with willingness and strength to finish this work. I wish to express my sincere gratitude and admiration to my supervisor Professor Dr. Khidair Adaay Salman, for his guidance, helpful advice and suggestions that have been of great value in the accomplishment of this research. I would like to express my appreciation to Prof. Hussein A. Al-Obaidi, (The past Head of Pedodontics, Orthodontics...