Finite element and Weibull analyses to estimate failure risks in the ceramic endocrown and classical crown for endodontically treated maxillary premolar Chun-Li Lin 1 , Yen-Hsiang Chang 2 , Chia-Yu Chang 2 , Che-An Pai 3 , Shao-Fu Huang 3 1 Department of Mechanical Engineering, Chang Gung University, Tao-yuan, Taiwan; 2 Operative Dentistry, Chang Gung Memorial Hospital, Tao-yuan, Taiwan; 3 Graduate Institute of Medical Mechatronics, Chang Gung University, Tao-yuan, Taiwan Restoration of severely damaged coronal hard tissue associated with an endodontically treated premolar is a challenge in reconstructive dentistry as a result of having a higher risk for biomechanical failure than a vital tooth. The primary reason for the reduction in stiffness and fracture resistance of endodontically treated teeth is the loss of structural integrity associated with caries, trauma, and extensive cavity preparation, rather than dehydra- tion or physical changes in the dentin (1–5). The lon- gevity of endondontic treatment is significantly influenced by the type of restorative materials used and an appropriate restoration that conserves tooth structure (3). The quality and integrity of the remaining tooth must be preserved with caution because it provides the solid base required for tooth restoration and influences the structural strength of the restored tooth (6–8). The classical approach for restoring an endodontically trea- ted tooth would be a build-up with a post and core, which has physical properties close to those of natural dentin, utilizing adhesive procedures, and subsequent placement of a full-coverage crown with sufficient ferrule (9–11). Several studies have demonstrated convincing clinical results for post adhesion to the root canal sub- strate (12–14). However, other studies on post and core techniques have reported highly variable survival rates, showing that root fractures may occur and the prepa- ration design for a post also adds a certain degree of risk for accidental root perforation (13, 14). With the development of adhesive techniques and ceramic materials, the advantage of adhesive restorations is that a macro-retentive design is no longer a pre- requisite if there are sufficient tooth surfaces for bonding. The endocrown preparation consists of a circular shoulder margin of 1 mm width and a central retention cavity the size of the pulp chamber that allows con- struction of the crown and core as a single unit (15, 16). The foundation in this technique utilizes the surface Lin C-L, Chang Y-H, Chang C-Y, Pai C-A, Huang S-F. Finite element and Weibull analyses to estimate failure risks in the ceramic endocrown and classical crown for endodontically treated maxillary premolar. Eur J Oral Sci 2010; 118: 87–93. Ó 2010 The Authors. Journal compilation Ó 2010 Eur J Oral Sci The present study evaluated the failure risks of an endodontically treated premolar with severely damaged coronal hard tissue and restored with either a computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic endocrown or a classical crown configuration. Two, three-dimensional finite element maxillary premolar models were designed with endodontic treatment and restored with either a chairside economic reconstruction of esthetic ceramic (CEREC) ceramic endocrown or a clas- sical crown. The Weibull function was incorporated with finite element analysis to calculate the long-term failure probability relative to different load conditions. Additionally, an in vitro fatigue-load fracture experiment was performed to validate the numerical simulation results. The results indicated that the stress values on the dentin and luting cement for the endocrown restoration were lower than those for the crown configuration. Weibull analysis revealed that the individual failure probability in the endocrown dentin and luting cement diminished more than those for the crown restoration. While the overall failure probabilities for the endocrown and the classical crown were similar, fatigue fracture testing revealed that the endocrown restoration had higher fracture resistance than the classical crown configuration (1,446 vs. 1,163 MPa). This investigation implies that the endocrown can be considered as a conservative, aesthetic, and clinically feasible restorative approach for endodontically treated maxillary premolars. Yen-Hsiang Chang, DDS, MS, Department of Operative Dentistry, Chang Gung Memorial Hospital, 123, Ding-Hu Road, Kuei-Shan, Tao-Yuan 333, Taiwan Telefax: +886–3–3196200 ext. 2138 E-mail: cgucaeb@yahoo.com.tw Key words: endocrown; endodontically treated premolar; failure probability; finite element analysis; Weibull analysis Accepted for publication November 2009 Eur J Oral Sci 2010; 118: 87–93 Printed in Singapore. All rights reserved Ó 2010 The Authors. Journal compilation Ó 2010 Eur J Oral Sci European Journal of Oral Sciences