Morphological dimensions of the apical area of mandibular premolars

Objectives: The aim of this study was to investigate the dimensions and shape of the apical constriction or physiological foramen as well as the distance between the physiological foramen and radiological apex of mandibular premolars. Methods: A total of 408 mandibular premolars were investigated under a stereo-microscope (32x). The foramen with the widest area was determined to be the main one since the anatomical internal aspects of the root canal system were not yet investigated. The large and small diameters and the shape of the physiological foramen as well as the distance between the physiological foramen and radiological apex were measured. The measurements were obtained through a software-supported device and statistically analyzed. Results: 150 first and 258 second mandibular premolars were investigated. In the first premolar one foramen was found in 80.66% with a mean large diameter of 0.233mm (0.081SD). When two foramina were observed the mean large diameters of the buccal and lingual foramina were 0.196 (0.054SD) and 0.184mm (0.056SD), respectively. In the second premolar one foramen was found in 65.50% with a mean large diameter of 0.280mm (0.077D). The second premolar had two foramina in 34.50%. The buccal and lingual foramina had a mean large diameter of 0.190mm (0.066SD) and 0.184mm (0.061SD), respectively. The most common physiological foramina shape observed was oval (80.66% first and 72.59% in the second premolar), respectively followed by round (19.33% first and 24.20% second premolar, respectively). Other shapes like triangular, kidney and irregular were also observed. The mean distance between the physiological foramen and radiological apex was of 1.122mm (0.382SD) and 1.02mm (0.446SD) in the first and second premolar, respectively. Conclusion: The results of this study can be applied to judge the working length and final apical preparation size during root canal therapy.