Dental caries are the major oral problems in the today's world. As today's world progressed we came to know that there are several factors that helps in the causation of dental caries. This book relates to the microbial organisms that are related in the causation of dental caries, how the dental caries progress. There are several other factors such as saliva, carbohydrate, time which helps the microganisms to grow and cause decay in the tooth. The role of bacteria in the formation of pellical which further progress into dental caries.