Effect of different restorative crown design and materials on stress distribution in endodontically treated molars: a finite element analysis study

Abstract

Background: The purposes of this simulation study were to evaluate the stresses in the roots of endodontically treated molars with extensive coronal tissue loss which were restored by endocrowns (all-in-one core and crown) and traditional crowns with post-cores, during masticatory simulation using finite element analysis. Methods: A mesio-distal cross-section of a lower right first molar was digitized and used to create 2-dimensional models of the teeth and supporting tissue; different crown designs, viz., endocrown with 2 mm occlusal clearance, endocrown with 4 mm occlusal clearance and post-core crown; different crown materials, viz., zirconia (Zr) and lithia-disilicate reinforced glass ceramic (LDRGC), and different post and core materials, viz., glass fiber (GF), stainless steel (SS) and metal cast (MC). An axial load of 600 N was applied to the central fossa of occlusal surface. Results: The stress distributions were similar between Zr and LDRGC for periodontal ligament and alveolar bone. The root canal inner wall maximum principal stresses of SS post (70.8 MPa) and MC post (71.4 MPa) were higher than that of GF post (36.0 MPa) and endocrown (2.4 MPa). Conclusion: The endocrowns reduced stress concentration for the root canal inner wall in comparison with the conventional post-core crown. Molars restored with endocrowns are less prone to root fracture than those with posts.

Lithium Disilicate Ceramic Endocrown Biomechanical Response According to Different Pulp Chamber Extension Angles and Filling Materials

“…It was observed that the filling material with a high elastic modulus (RC, BF, AK, FRC) allowed less stress magnitude to reach the cement layer; however, it increased the stress magnitude in the tooth substrate as well as in the restoration. In addition, the literature reports that more flexible restorative materials could be a promising option for the promotion of adequate biomechanical behavior for the endocrown restorations [ 3 , 4 , 6 , 15 , 18 , 22 ]. This study complements this finding, showing that the filling material stiffness can also modify the stress concentration in the restoration.…”

“…Despite the literature reporting endocrown preparations with different central retainer angulation, ranging from 6° to 12° of divergence [ 7 , 13 , 14 , 15 , 16 ], there is no mechanical reason for the selected angle parameter. Apparently, a citation chain occurred between the previous reports and there was no assessment regarding how the preparation angle can affect the restoration load dissipation.…”

“…In the present study, the design criteria of the filling material layer were used based on previous in vitro [ 1 , 2 , 15 , 25 ] and in vivo [ 14 , 20 ] reports. Therefore, the concept is to fill the pulp chamber with the restorative material and then, to perform an adequate endocrown preparation [ 18 ].…”

“…In the literature, different angles are reported during the pulp chamber preparation prior to the endocrown manufacturing. A clinical report used a cylindrical–conical diamond bur with convergence of 7° to perform the preparation [ 14 ], while in vitro studies have reported axial walls with 8° of divergence [ 13 ], values between 6° and 8° [ 15 ], 10° [ 16 ], and even 12° of divergence [ 7 ]. However, how the pulp chamber preparation angle can affect the endocrown mechanical response has not been elucidated yet.…”

Case report: Fabrication of a dental implant guide based on tetrahedron positioning technology

“…In recent years, dental implant surgery based on cone-beam computed tomography (CBCT) and three-dimensional (3D) printing surgical guide technology has been widely used in clinical practice and plays an important role in improving the accuracy of implantation and final restoration [ 1 – 3 ]. Any virtual implant planning system using a 3D software application in combination with implant placement by means of a computer-aided design/computer-aided manufacturing (CAD/CAM)-processed surgical guide is defined as a system for static computer-assisted implant surgery (s-CAIS) [ 4 ].…”