Study On The Total Root Tip Of Mandibular Premolars With Double Root

Purpose:To study the incidence of double roots morphology in mandibular premolars in full-mouth periapical films in Chinese population, especially those occur bilaterally. To provide clinical anatomical basis for the root canal treatment to the mandibular premolars.Materials and Methods:A total of2015patients who underwent dental treatment and had full mouth periapical X-ray films in the Peking University School of Stomatology from April2011to April2012were enrolled in this study. Three experienced dentists, a master of endodontology, a professor of endodontology and a professor of dental radiology reviewed those patients’ films and tried to classify the morphology of the roots of bilateral mandibular premolars. Incidence of unilateral and bilateral double roots were recorded and calculated, Including confirmed and suspected buccal-lingual roots types. For those uncertain cases, the three dentists would discuss together until reached a consensus.Results:1. Double roots morphology of mandibular first premolars.Of all the2015cases with complete root,5cases were excluded because of absence of bilateral mandibular first premolars, another48cases were excluded because of absence of unilateral mandibular first premolar. Double-root first premolars were detected in120cases with a total number of159teeth. According to the number of teeth, the overall incidence of double roots was4.03%(159/3972). According to the number of cases, the incidence was32.5%(39/120).2.Double roots morphology of mandibular second premolar.Of all the2015cases with complete root,17cases were excluded because of absence of bilateral mandibular second premolars, another116cases were excluded because of absence of unilateral mandibular second premolars. Double-root second premolars were detected in24cases with a total number of33teeth. According to the number of teeth, the overall incidence of double roots was0.85%(33/3880). According to the number of cases, the incidence was37.5%(9/24).Conclusion:According to the present study, we draw a conclusion that there are definite morphology in the root of mandibular premolars. Base on a very large sample, we observed and calculated not only the occurrence rate of bucco-lingual and mesio-distal double roots in first and second mandibular premolars, but the occurrence rate of unilateral or bilateral double roots in the same mandible. These findings could provide better information of the anatomy structure of mandibular premolars in endodontic, prothodontic and surgical procedures, improve the quality of treatment and reduce complications.