A Severely Damaged Mandibular First Molar Restoration with CAD/CAM Customized Hybrid Ceramic Post and Core by Direct Intraoral Impression: A Case Report

The outcome of the teeth with coronal restoration may be unforeseeable when they need root canal therapy due to apical periodontitis, especially at the existence of a post. This case report describes a digital restoration strategy for the preservation of a serious defect tooth (left mandibular first molar). Tooth #36 with 10 years of a crown and post restoration needed root canal therapy due to apical periodontitis. After removal of the crown and cast post, the residual tooth showed fragility, and the distal root canal was seriously destroyed due to the post insertion. Selecting a suitable post was significant for the retention of the core to support the coronal restoration after the completion of the root canal therapy and apical barrier. The prefabricated fiber post and metal cast post were not good selections for the distal root canal. Therefore intraoral scanning was performed on the tooth and digitized to design a three-dimensional model of customized post-core and full crown by the Computer-Aided Design/Computer- Assisted Manufacture (CAD/CAM) technique. A 14-month follow-up showed a promising clinical and radiographic outcome. The digital CAD/CAM technique converted the concave surface of the root canal into the convex surface of the post, and fabricated an anatomical post and core using hybrid ceramic material close to the elastic modulus of natural dentin. It improved the biomechanics of this tooth #36 and reduced the occurrence of root fracture.