Abstract:

Objective To measure the root anatomic topography of mandibular first molar using cone beam CT （CBCT）, calculate the proper space for dowel preparation. Methods The roots of 121 mandibular first molars from 71 patients were scanned by CBCT, the images from cross section, sagittal plane, and coronal plane were got respectively. The dowel preparation spaces according to established three dimensional images and dowel preparation requirements were analyzed. Results Three dowels could be prepared. The dowel length for distal-root was （7.19±0.91）mm, dowel diameter was（0.80±0.12）mm on the level of 4 mm above root apex. The dowel length for mesio-root was（6.92±1.02）mm, and dowel diameter was （0.71±0.08）mm on the lever of 4 mm above root apex for buccal side and （0.71± 0.07）mm for lingual side. Dowel should be prepared cone-shaped. Conclusion Many factors affect dowel preparation, individualized design is needed. CBCT can provide reliable radiographic evidence.

Key words: cone beam CT, mandibular first molar, dowel