How many third molars remain unnoticed in a population survey without panoramic radiographs?

The aim of the study was to compare the findings of clinical examination and panoramic radiograph regarding the occurrence of third molars in a population survey to find out how many third molars remain clinically unnoticed. A two-staged stratified cluster-sampling method was used to select 8028 participants representing the adult population aged 30 years and older. Clinical oral examinations and panoramic radiographs were carried out for 5989 subjects (46% men, 54% women; mean age 52.5, SD 14.6; range 30-97 years). Clinical recordings of the presence of third molars were compared with the radiographs. Statistics included chi-squared, Fisher's, Wilcoxon's, and Kruskal-Wallis tests. In the 5989 subjects, 3742 third molars were recorded in the clinical examination, and 5912 were observed in the panoramic images, a difference of 2170 teeth. Furthermore, related to 3668 (61%) of the third molars, both clinical and radiographic recordings were attributed to the same third molar, while 2244 third molars were observed only in the panoramic image, and 74 only in the clinical examination. In every age group, the mean number of third molars per subject was larger radiographically compared with the clinical recordings (means for all 0.99 vs. 0.62; P < 0.001). Numbers of third molars, recorded in clinical examination alone, are underreported by approximately one-third compared with radiographic findings. The numbers of third molars in a population survey without a panoramic radiograph do not reflect the total number of third molars in a population.