Stress distribution on dentin-cement-post interface varying root canal and glass fiber post diameters. A three-dimensional finite element analysis based on micro-CT data

Objective: The aim of the present study was to analyze the influence of root canal and glass fiber post diameters on the biomechanical behavior of the dentin/cement/post interface of a root-filled tooth using 3D finite element analysis. Material and Methods: Six models were built using micro-CT imaging data and SolidWorks 2007 software, varying the root canal (C) and the glass fiber post (P) diameters: C1P1-C=1 mm and P=1 mm; C2P1-C=2 mm and P=1 mm; C2P2-C=2 mm and P=2 mm; C3P1-C=3 mm and P=1 mm; C3P2-C=3 mm and P=2 mm; and C3P3-C=3 mm and P=3 mm. The numerical analysis was conducted with ANSYS Workbench 10.0. An oblique force (180 N at 45º) was applied to the palatal surface of the central incisor. The periodontal ligament surface was constrained on the three axes (x=y=z=0). Maximum principal stress (σmax) values were evaluated for the root dentin, cement layer, and glass fiber post. Results: The most evident stress was observed in the glass fiber post at C3P1 (323 MPa), and the maximum stress in the cement layer occurred at C1P1 (43.2 MPa). The stress on the root dentin was almost constant in all models with a peak in tension at C2P1 (64.5 MPa). CONCLUSION: The greatest discrepancy between root canal and post diameters is favorable for stress concentration at the post surface. The dentin remaining after the various root canal preparations did not increase the stress levels on the root

Cortical Bone Stress Distribution in Mandibles with Different Configurations Restored with Prefabricated Bar-Prosthesis Protocol: A Three-Dimensional Finite-Element Analysis

Purpose: To evaluate stress distribution in different horizontal mandibular arch formats restored by protocol-type prostheses using three-dimensional finite element analysis (3D-FEA).Materials and Methods: A representative model (M) of a completely edentulous mandible restored with a prefabricated bar using four interforaminal implants was created using SolidWorks 2010 software (Inovart, São Paulo, Brazil) and analyzed by Ansys Workbench 10.0 (Swanson Analysis Inc., Houston, PA) to obtain the stress fields. Three mandibular arch sizes were considered for analysis, regular (M), small (MS), and large (ML). Three unilateral posterior loads (L) (150 N) were used: perpendicular to the prefabricated bar (L1); 30 degrees oblique in a buccolingual direction (L2); 30 degrees oblique in a lingual-buccal direction (L3). The maximum and minimum principal stresses (sigma(max), sigma(min)), the equivalent von Mises (sigma(vM)), and the maximum principal strain (sigma(max)) were obtained for type I (M. I) and type II (M. II) cortical bones.Results: Tensile stress was more evident than compression stress in type I and II bone; however, type II bone showed lower stress values. The L2 condition showed highest values for all parameters (sigma(vM), sigma(max), sigma(min), epsilon(max)). The sigma(vM) was highest for the large and small mandibular arches.Conclusion: The large arch model had a higher influence on sigma(max) values than did the other formats, mainly for type I bone. Vertical and buccolingual loads showed considerable influence on both sigma(max) and sigma(min) stresses.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Insertion and follow-up of complete dentures: a literature review

Insertion and follow-up of complete dentures: a literature reviewObjective: The aim of this study was to present the importance of clinical procedures related to insertion and follow-up of complete dentures in elderly patients.Materials and Methods: The success of rehabilitation with complete dentures results from the accuracy of clinical and laboratorial procedures that makes the denture insertion an important step of treatment.Conclusion: The follow-up and professional maintenance of function and hygiene facilitates long-term efficiency

Oral rehabilitation of severely worn dentition using an overlay for immediate re-establishment of occlusal vertical dimension

The aim of this study was to describe the treatment used in an elderly patient presenting with bruxism and dental erosion, with good gingival health and bone support, but with decreased occlusal vertical dimension (OVD). The oral rehabilitation of elderly patients presenting with bruxism in association with tooth erosion has been a great challenge for dentists. The loss of OVD, the presence of occlusal instability and the absence of an effective anterior guide due excessive dental wear, can damage stomatognathic system (SS) biology, the function and the aesthetics. In the first treatment stage, an overlay removable partial denture (ORPD) was fabricated for the immediate re-establishment of function and aesthetics. After a 2-month follow up, with the patient presenting no symptoms, a second rehabilitation stage was accomplished, with fixed and removable prostheses. Oral rehabilitation with an ORPD was able to re-establish the SS biology, but a correct diagnosis and treatment plan are essential for success. The ORPD is a non-invasive and reversible restoring modality for general dentists that allow the re-establishment of the patient's immediate aesthetics and function at low cost

Mechanical behavior of ceramic veneer in zirconia-based restorations: a 3-dimensional finite element analysis using microcomputed tomography data

Statement of problem. The fracture or chipping of ceramic veneers is a common problem for zirconia-based restorations.Purpose. This study evaluated the stress distribution in the veneer of a maxillary central incisor restored with a complete crown using a zirconia core with a feldspathic ceramic veneer, simulating an incomplete bond between the veneer and zirconia substructure.Material and methods. Based on a microcomputed tomography of a maxillary central incisor, 3 finite element models (M) for a complete crown were developed: Mf, a complete crown based on feldspathic ceramic; Mlz, a zirconia-based complete crown with a complete bond at the zirconia/veneer interface; and Mnzl, similar to Mlz, but with an incomplete bond at the zirconia/veneer interface created by using a contact element with a frictional coefficient of 0.3. A distributed load of 1 N was applied to the lingual surface at 45 degrees to the long axis of the tooth.Results. The zirconia core in the Mnzl model showed peak stresses for maximum principal stress (sigma(max)) and shear stress of 9.02 and 8.81 MPa, respectively. The ceramic veneer in the Mnlz model showed peak stresses for sigma(max), minimum principal stress (compressive), and von Mises stresses of 5.4 MPa, 61.23 MPa, and 35.19 MPa, respectively.Conclusions. The incomplete bond increased the sigma(max) in the ceramic veneer in comparison to the perfect bond condition. (J Prosthet Dent 2010;105: 14-20)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Mechanics of the maxillary central incisor. Influence of the periodontal ligament represented by beam elements

This study aimed to evaluate the influence of loading on a maxillary central incisor with the periodontal ligament (PDL) represented by 2D elastic beam elements using a 2D finite element analysis. Two models (M) were built varying the PDL representation: Mh (homogeneous PDL) and Mht (heterogeneous PDL with beam3 elements). Stress and displacements were determined for three loading conditions (L): Ll, lingual face loading at 45 degrees with the tooth long axis; Li, perpendicular to the incisal edge; and Lip, on the incisal edge, parallel to the tooth long axis. Evaluation was performed on ANSYS software. Lip provided lower stress variation on the tooth and support structures when compared to Ll and Li. PDL's influence on stress values was lower for Lip. Oblique loading showed stress and displacement not observed in parallel loading condition through PDL's heterogeneous representation and it is probably incompatible with the in vivo condition.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Influence of Crown Ferrule Heights and Dowel Material Selection on the Mechanical Behavior of Root-Filled Teeth: A Finite Element Analysis

Purpose: This study used the 3D finite element (FE) method to evaluate the mechanical behavior of a maxillary central incisor with three types of dowels with variable heights of the remaining crown structure, namely 0, 1, and 2 mm. Materials and Methods: Based on computed microtomography, nine models of a maxillary central incisor restored with complete ceramic crowns were obtained, with three ferrule heights (0, 1, and 2 mm) and three types of dowels (glass fiber = GFD; nickel-chromium = NiCr; gold alloy = Au), as follows: GFD0 restored with GFD with absence (0 mm) of ferrule; GFD1 similar, with 1 mm ferrule; GFD2 glass fiber with 2 mm ferrule; NiCr0 restored with NiCr alloy dowel with absence (0 mm) of ferrule; NiCr1 similar, with 1 mm ferrule; NiCr2 similar, with 2 mm ferrule; Au0 restored with Au alloy dowel with absence (0 mm) of ferrule; Au1 similar, with 1 mm ferrule; Au2 similar, with 2 mm ferrule. A 180 N distributed load was applied to the lingual aspect of the tooth, at 45 degrees to the tooth long axis. The surface of the periodontal ligament was fixed in the three axes (x = y = z = 0). The maximum principal stress (smax), minimum principal stress (smin), equivalent von Mises (svM) stress, and shear stress (sshear) were calculated for the remaining crown dentin, root dentin, and dowels using the FE software. Results: The smax (MPa) in the crown dentin were: GFD0 = 117; NiCr0 = 30; Au0 = 64; GFD1 = 113; NiCr1 = 102; Au1 = 84; GFD2 = 102; NiCr2 = 260; Au2 = 266. The smax (MPa) in the root dentin were: GFD0 = 159; NiCr0 = 151; Au0 = 158; GFD1 = 92; NiCr1 = 60; Au1 = 67; GFD2 = 97; NiCr2 = 87; Au2 = 109. Conclusion: The maximum stress was found for the NiCr dowel, followed by the Au dowel and GFD; teeth without ferrule are more susceptible to the occurrence of fractures in the apical root third.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES