Morphology of root canals in adult premolar teeth.

The aim of the present study was to examine the morphology of root canals in premolar teeth with completely formed root apices. The material consisted of 139 extracted premolar teeth, including 83 first premolars (59.7%) and 56 second premolars (40.3%). Maxillary teeth made up 64% of the material and mandibular teeth 36%. In order to measure the actual root canal length an endodontic instrument was inserted into the root canal (in teeth with a single root canal this was instrument no. 25 and in teeth with two or three root canals no. 20) until its tip was visible in the anatomical foramen. The silicone limit was fixed at a reference point on the dental crown, and after removal of the instrument the real length was read using an endodontic ruler. The results were presented using descriptive statistical measures (mean, maximum, minimum, median value and quartiles). In order to compare mean values of root canal lengths the z test was used. Of the first maxillary premolars, 91% had two root canals and 9% had three root canals. As far as the second upper premolars are concerned, 14.7% were teeth with single root canals while as many as 85.3% were teeth with two root canals. The majority of the first lower premolars (89.3%) had one root canal and 10.7% of these teeth had two root canals. Most of the second lower premolars (68.2%) had a single root canal, while the remaining 31.8% had two root canals. None of the mandibular premolars examined had three root canals.