The earliest reference to tooth decay and toothache came from the ancient Sumerian text known as the "Legend of the worm". Dental caries is an infectious microbiologic disease of the teeth that results in localized dissolution and destruction of calcified tissues or it is a "microbial disease of the calcified tissues of the teeth, characterized by demineralization of the inorganic portion and destruction of the organic substance of the tooth. Progression of caries in dentin is different from progression in the overlying enamel because of the structural differences of dentin. Dentin contains much less mineral and possesses microscopic tubules that provide a pathway for the ingress of acids and egress of mineral However, one may define it, its mainly a disease that dates back to antiquity and has also occurred in populations that have never used sugar or processed foods. Such infections may lead to tooth loss resulting in diminished chewing ability, pain, suffering and cosmetic defects. Present book is a useful guide for acquiring advance knowledge related to accurate diagnosis, current preventive concepts and effective management of tooth decay.