Int. J. Environ. Res. Public Health 2009, 6 2507 activity can be assessed most accurately. In order to assess the activity of carious lesions with UniViSS the degree of discoloration as well as the clinical conditions from Table 2 need to be taken into account. As a general assumption, white and white-brown lesions are associated with more active caries lesions, while brown and black lesions normally indicate a slower disease progression. Apart from discolorations, plaque is another etiological factor that also provides clues to the activity of a caries lesion. Location plays a part here, too. The natural plaque stagnation areas [17], e.g., the vestibular surfaces nearby the gingival margin, the lingual surfaces of the molars in the lower jaw, or the approximal spaces, are difficult to reach with the tooth brush and therefore more likely to be caries susceptible. Whether roughness will gain significance as a valid caries predictor in the future remains to be seen [17]. Due to the meticulous classification of all possible stages of the caries process UniViSS is able to register logically the clinical appearance of all kind of carious lesions. However, by grouping the various criteria its use can be simplified significantly, e.g., for the purpose of epidemiologists. Epidemiological studies normally require a simple and practicable procedure to ensure that the several tests can be carried out efficiently under field conditions, too. The easiest way of doing this is to group all non-cavitated lesions under the same category (Scores F, E, M) apart from registering the cavitated caries lesions (Scores D, L, P = D-component of the DMF index) and to record them as one score for the respective tooth or surface. Thus, any carious processes that can at least be observed visually will be captured. Although it requires more effort, each of the three diagnostic steps mentioned above (1. severity assessment, 2. discoloration assessment, and 3. activity assessment) may also be included in the study design. In order to ensure the reproducibility of the results the teeth should be cleaned and the examiner(s) should have received a calibration training prior to the study. Each caries diagnosis has to be linked with distinct treatment strategy. Therefore the dentist has to decide whether those lesions may be treated with non-invasive/preventive or invasive/restorative measures. The classification according to the treatment strategies suggested by Pitts [25]—non-active care advised, preventive care advised and operative care advised—is therefore sufficient. Since every diagnosis should be linked to specific treatment strategies, the clinical consequences of different UniViSS results will be outlined in the following. While active treatment is not considered necessary as such for sound tooth surfaces, the intensification of preventive efforts at home remains a basic aim for caries risk patients as well as on existing caries lesions. First visible lesions as well as established lesions should be treated with professional measures, i.e., topical fluoridation and the sealing of pits and fissures, in addition to a more comprehensive home prophylaxis program, to stop caries progression. On microcavities—if the radiograph shows an involvement of the dentine which indicate a bacterial infection—an appropriate restorative treatment seems to be indicated in most of the cases [26]. Otherwise, the complete sealing of the microcavity constitutes a possible therapeutic option [27-29]. Restoration is clearly indicated for carious lesions with dentine exposure, greyish translucencies or gross cavitations. The decision between endodontic therapy or extraction after pulp exposure should be carefully weighted based on patients preferences, the individual dental health status, age as well as the need, feasibility and costs for follow-up treatments. The measures listed here represent mainly the preventive and therapeutic spectrum for industrialized countries, whereas fundamentally different