Oral cavity is a complex system which is subjected to variety of microorganisms and local irritants factors which may disrupts the homeostasis and lead to variety of diseases, thus it necessitates to formulate drugs which is effective to withstand the oral environment. Specialized drug delivery systems are developed to overcome these difficulties and thus provide effective drug dosage. This book provides the readers a glimpse about the basic understanding about the oral epithelium, mechanism of drug penetration, factors which affect the drug absorption ,deals with the various drug formulations and their commercial forms.