Signs of disease occur in the majority of third molars in an adult population.

The purpose of this study was to assess clinical and radiographic signs of disease in third molars within a population that is representative of the Finnish adult population aged 30 years and older. A two-stage stratified cluster sampling method was used to collect the 6005 subjects, who were examined clinically and also by panoramic radiography. The state of impaction, presence of dentinal caries and/or restorations, presence of root canal fillings, periodontal pocket depth, and additional pathological findings such as over-eruption and widened follicle were assessed. Signs of disease in the third molars were found in 47% of the adult population and in 97% of those subjects with third molars. At least one sign of disease occurred in 82% of erupted third molars compared to 74% of those impacted in soft tissue and 33% impacted in bone (P<0.001). A diseased third molar was more often located in the mandible (60%) than in the maxilla (40%) (P<0.001), and was more often found in men (57%) than in women (43%) (P<0.05). It is concluded that signs of disease in third molars in the target population are more common than has been reported previously.