Int. J. Environ. Res. Public Health 2009, 6 2502 translucencies. But with white-brown discolorations UniViSS adds a new criterion that appears for many lesions in the clinical practice. Deep cavities with pulpal involvement were likewise considered since they are commonly associated with early childhood caries while also occurring with frequency in the permanent dentition of patients in developing countries, where caries remains often untreated. By matching them against our image database, which currently contains over 1,500 high-quality photographs of very different carious lesions from occlusal and/or smooth surfaces of primary and permanent teeth, the criteria were generalized and summarized. For 117 occlusal surfaces histological findings from a preliminary study were also available in addition to the photographs [18]. These data, together with the results of previously validated investigations [3,8,17-19], were the mainly influences for the systematization of our diagnostic system. 2.2. Systematization of the Diagnostic Criteria Different to existing visual systems for caries detection/diagnosis, which are essentially a sequence of criteria from ‘healthy’ to ‘severely decayed’, UniViSS uses a three-step diagnostic procedure to classify in detail the complex clinical appearance of carious lesions. These three steps are: (1) severity assessment (the severity also determines the detection level, if a caries lesion is present); (2) discoloration assessment; and (3) activity assessment. The lesion activity should be recorded as a Yes/No decision. As a whole, UniViSS can therefore be understood as a three-dimensional system of caries detection and diagnosis (Figure 1). Figure 1. Three-step procedure of UniViSS for detection and assessment of caries lesions. 2.3. Pre-Clinical Tests on Practicability The stepwise development of UniViSS happened over several years and was supported by repeated evaluations of the system to its present state. Each time, several experienced dentists assessed the system’s status in terms of its practicability, consistence and design under different conditions. The evaluations were followed by an exchange of knowledge and ideas and discussions about possible improvements. The development status of UniViSS was then updated and approved. The following tests were carried out: