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Abstract
BackgroundTo evaluate the stress distribution in a maxillary central incisor with different post and cores made of six CAD/CAM materials with different elastic modulus in the absence of ferrule using the finite element analysis.Material and MethodsA three-dimensional endodontically treated maxillary central incisor restored with an all-ceramic crown was modelled in Rhinoceros (5.0 SR8, McNeel). The geometries were analyzed in ANSYS 17.2 (ANSYS Inc.) considering isotropic, homogeneous, linearly elastic materials with perfectly bonded contacts. The elastic moduli (E) of the post-and-cores defined the groups to be compared: nanoceramic resin (E=12.8GPa); composite resin (E=16GPa); hybrid ceramic (E=34.7GPa); lithium disilicate (E=95GPa); titanium (Ti-Al6-V4) (E=112GPa); and Y-TZP material (E=209.3GPa). The set was constrained in the cortical bone and loaded (45°/100 N) on the incisor palatine face. Stress distribution was analyzed by Maximum Principal Stress criteria for the crown-core cement line, Post-and-core’s cement line, Post-and-core system and Dentin.ResultsThe stress distribution at the crown-core cement line (11.4 – 13.2 MPa) was inversely proportional to the increase of the elastic modulus of the post-core approaches, while it was direct proportional on the post-and-core (4.7 – 40 MPa) and cement line (4.1 – 6.2 MPa). Stress distribution on the dentin was similar for all groups (24.7 - 25.3).ConclusionsPost-and-core made by CAD/CAM seems to be an efficient treatment alternative, since it is a conservative approach, promotes better aesthetic quality and it allows the control of the cement line thickness. Key words:Endodontically treated teeth, Post-and-core technique, Ceramic crown, Finite element analysis, Biomimetics.
Highlights
Posts are normally used to provide retention to the core in endodontically treated teeth with extensive loss of coronal and intracanal structures
A study on stress distribution to cement layer and root dentin for post and cores made of CAD/CAM materials with different elasticity modulus in the absence of ferrule
Stress distribution on the dentin was similar for all groups (24.7 - 25.3 MPa)
Summary
Maximum Principal Stress (MPS) analysis demonstrated that higher stress concentration in the cement line between crown-core when a post and core with lower elastic modulus was used (Fig. 2A). The difference between groups was only 2 MPa for the crown/ core and post/dentin cement lines. Demonstrated that the maximum tensile stress difference between the less and more rigid material was approximately 2 MPa (Table 2), and did not show a significant difference for the bond strength of the crown This stress would possibly be relevant when the individual bond strength of each material were taken into account. The results show that the maximum stress distribution exceeded the bond strength (Table 3) [10,22,23,24,25,26,27,28,29] of zirconia with surface treatment (7.9 ± 2.6 MPa) [26], and was close to the resistance of titanium (14.79 ± 2.33 MPa) [27] and the nanoceramic resin (14.35 ± 2.56) [25]
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