Analysis of radiologic factors in determining premolar root canal systems

Certain tooth groups pose problems as to radiologic determination of root canal morphology. For example, the premolars may have superimposed roots that give the appearance of a single canal when 2 are actually present. This study examined the effect of X-ray tube inclination so as to visualize the complete root canal system in premolars.

One hundred extracted premolars were divided into 4 groups of 25 teeth each: 1MxP (first maxillary premolar), 2MxP (second maxillary premolar), 1MdP (first mandibular premolar), and 2MdP (second mandibular premolar). A total of 10 radiographs were made of each tooth in the horizontal and vertical planes (horizontal angles of 0, 20, and 40 degrees, then vertical angles of 0, 15, and 30 degrees). Logistic regression analysis was used for the statistical analysis of the results--the dependent variable being the number of canals visualized.

On varying the horizontal angle (20 and 40 degrees), the number of root canals observed in the case of 1MxP, 2MxP, and 1MdP coincided with the actual number of canals present. In the case of 2MdP, only the 40 degree horizontal angle correctly identified the number of canals regardless of the vertical angle (although only 4% had more than 1 canal).

Varying the horizontal angle improved the visualization of additional (superimposed) canals in premolars. Changing of the vertical angle had no statistically significant influence except for the first mandibular premolars.