Three-dimensional Space Research In Dowel Preparation For The Mandibular First Molar

Objectives:Measure the root anatomic topography of mandibular first molar using CBCT, calculating the three-dimensional space for dowel preparation.improve the accuracy and reduce the chance of root fracture to achieve better resultsMethod:the roots of153mandibular first molar in85patients been scaned by CBCT, then analysis the dowel preparation space according to established three dimensional images acquired from cross section、 sagittal plane、 coronal plane and conform to dowel preparation requirementsResult:three dowels can be prepared including two mesio dowels and one distal dowel.the dowel length for distal root is7.21±0.92mm, dowel diameter is0.81±0.11mm on the level of4mm above root apex. the dowel length for mesio root is6.91±1.01mm, dowel diameter is0.72±0.08mm on the lever of4mm above root apex for buccal side and0.72±0.09mm for lingual side. Dowel should be prepared cone-shaped.Conclusion:many factors contribute to dowel preparation results, three-dimensional concept must be followed individualized design is needed to obtain rational dowel preparation, CBCT can provide reliable radiographic evidence.