Dental Caries is a gradual disease process, with demineralization and remineralization occurring over time. The slower progression of carious lesions has afforded the dental profession the opportunity to diagnose at the earliest. So that management approach of dental caries can be changed from initial approach of extension for prevention to more conservative approach of conservation for prevention. An ideal diagnostic method is required, which is the one with high sensitivity and specificity, so that it diagnose the caries at its incipient stage. Early detection of incipient caries and limitation of caries activity prior to significant tooth destruction are primary goals of an effective diagnosis and treatment planning. This book throws light upon reliable, quantitative diagnosis to arrest the activity of the disease, required in clinical practice.