ABSTRACT
Transient and residual stresses occurring in partially fixed dental prostheses after the firing process can be calculated with elastic or elastic-plastic finite element analyses (FEA). In this study, firstly, the mechanical and thermal properties at various temperatures of the materials used in a porcelain fused metal (PFM) system were obtained by experimental and literature studies. The effects of viscoelastic and viscoplastic behaviours of the dental porcelain at the elevated temperatures were reflected onto its elastic properties. The equivalent heat transfer coefficients were determined experimentally by measuring temperatures and the results were supplied as input to the 3D finite elements analysis. It has been observed that the maximum stresses occur within a short time period after cooling begins and that stresses decrease during the cooling process and remain at a constant value at the end of cooling; these are the thermal residual stresses.
Subject(s)
Ceramics/chemistry , Computer-Aided Design , Dental Prosthesis , Dental Restoration Failure , Metals/chemistry , Computer Simulation , Dental Prosthesis Design/methods , Elastic Modulus , Equipment Failure Analysis , Finite Element Analysis , Hardness , Models, Theoretical , Stress, Mechanical , Temperature , ViscosityABSTRACT
This study evaluated the stress distribution on an endodontically treated maxillary central incisor restored with different post-and-core systems by using a three-dimensional finite element analysis model. Seven three-dimensional finite element models were created. Each model contained cortical bone, cancelous bone, periodontal ligament, 3 mm apical root canal filling, post-and-core and all-ceramic crowns. Two different pre-fabricated zirconia ceramic post systems, a glass fiber-reinforced post system and a titanium post system were modeled. As a control, an all-ceramic crown on an endodontically treated maxillary central incisor without a post-and-core was modeled. Each model received a 45 degrees oblique occlusal load at a constant intensity of 100 N. In each model, the ratio of Von Mises stress distribution was compared. The greatest stresses were observed in the coronal third of the roots on facial surfaces. The ratio of Von Mises stress distribution in dentin for the zirconia ceramic post (CosmoPost) and ceramic core (Cosmo Ingot), zirconia ceramic post (CosmoPost) and composite core (Tetric Ceram), glass fiber-reinforced post (FRC Postec) and composite core (Tetric Ceram), titanium post (Er post) and composite core (Tetric Ceram), zirconia ceramic post (Cerapost) and ceramic core (Cosmo Ingot), zirconia ceramic post (Cerapost) and composite core (Tetric Ceram) and the control group were 0.886, 0.889, 0.988, 0.924, 0.889, 0.893 and 1, respectively. The stress concentrations in dentin created by two different zirconia ceramic post systems were nearly the same. The zirconia ceramic post systems created slightly less stress concentration in dentin than the glass fiber-reinforced and titanium posts.
Subject(s)
Dentin/physiopathology , Incisor/physiopathology , Maxilla , Post and Core Technique , Bite Force , Ceramics/chemistry , Composite Resins/chemistry , Crowns , Dental Materials/chemistry , Finite Element Analysis , Glass/chemistry , Humans , Imaging, Three-Dimensional , Materials Testing , Models, Biological , Periodontal Ligament/physiopathology , Post and Core Technique/classification , Root Canal Filling Materials/chemistry , Root Canal Obturation , Stress, Mechanical , Titanium/chemistry , Tooth Root/physiopathology , Tooth, Nonvital/physiopathology , Zirconium/chemistryABSTRACT
This study investigated the designs of osseointegrated prostheses in cases of free-end partial edentulism using comparative stress interpreted with the three-dimensional finite element method. Three free-end fixed osseointegrated prostheses models with various connection designs (i.e., rigidly connected to an abutment tooth and an implant, rigidly connected to an implant and two abutment teeth, and rigidly connected to an implant and three abutment teeth) were studied. The stress values of the three models loaded with vertical, buccolingual, and linguobuccal directions at 30 degrees angled to vertical axis forces were analyzed. When the fixed partial denture was connected to the three natural abutment teeth and an implant, the lowest levels of stress in the bone were noted.
Subject(s)
Dental Implants , Dental Prosthesis, Implant-Supported , Dental Stress Analysis , Denture, Partial, Fixed , Jaw, Edentulous, Partially/physiopathology , Alveolar Process/physiology , Bite Force , Cementation , Cuspid/physiology , Dental Abutments , Dental Implantation, Endosseous , Dental Occlusion, Traumatic/etiology , Dental Prosthesis Design , Dental Prosthesis Retention , Dental Prosthesis, Implant-Supported/adverse effects , Finite Element Analysis , Humans , Incisor/physiology , Mandible , Periodontal Ligament/physiologyABSTRACT
The effects of residual stresses, which are caused by the temperature difference arising after polymerisation of bone cement, on the fracture energies of cement bone and cement-implant interfaces have been examined by using both experimental and numerical works. Only fracture loads of the test specimen having interfacial cracks have been measured in the experimental stage. The values of fracture loads and temperature difference after polymerisation have been applied to finite element models of the test specimens to calculate critical J-integral values of these both interfaces in the numerical stage. In addition, fracture energies of bone and cement, have been obtained by experimentally, using three-point bending test method The results have shown that residual stresses can produce changes in the fracture energies of these bimaterial systems, especially in cement implant interface and J(Ic) values of interfaces are considerably smaller than the experimentally determined J(Ic) values of cement and bone.
