This book is a compilation of new and innovative techniques for the assessment and characterization of orally important conditions such as caries, periodontal diseases and calculus. It also gives recommendations for the validation of new methods. There are discussions on optical fluorescence and direct digital radiography for the detection and quantification of caries, as well as optical coherence tomography and its application in the imaging of internal tissue microstructure. Furthermore, recent advances in the evaluation of dental calculus and the quantification of plaque and periodontal bone and attachment loss are elucidated. Moreover, an outline is given for the evaluation of three-dimensional structures using methods of coordinate metrology, and the use of biological markers in the assessment of gingival inflammation is considered. The final chapter discusses the validation criteria that need to be applied to any diagnostic method before it can be generally accepted.