The interest in the dental bio film has increased in recent years because of the growing evidence that specific species are etiologic agents of dental carries and periodontal diseases. Development of dental plaque, species involved and their pathogenicity was discussed. Conditions leading to the development of dental diseases, quorum sensing in bio film, regulation of gene expression in dental plaque, use of antibiotics in dentistry, antimicrobial resistance in plaque bacteria, streptococci associated with dental plaque of human beings were discussed in this book. The book also deals with the isolation of streptococci from human beings of different age groups and their diagnosis using morphological and biochemical identification of streptococci, bio film assay, antibiotic sensitivity in planktonic and bio film states are discussed in detail. The book discusses the recent advancements and experimental designs in researches carried out on dental plaque, bio film development by streptococci and antibiotic sensitivity. The book is expected to provide in depth information to dentists, medical microbiologists and bacteriologists who are involved in research dealing with dental plaque.