The aim of this study was to evaluate the effect of biologically oriented preparation technique on the stress concentration of endodontically treated upper central incisors restored with zirconia crown (yttria-stabilized zirconia polycrystalline ceramic) through finite element analysis (FEA). Four models of maxillary central incisors containing enamel, dentin, periodontal ligament, cortical and medullary bone were created in CAD. Each model received a polymeric core-build up with nanofilled dental resin composite. The evaluated models were SM—preparation in shoulder 90°; CM—chamfer preparation; BOPT—biologically oriented preparation technique and BOPTB—BOPT preparation 1 mm below the cement-enamel junction. All models received zirconia crowns (5Y-TZP), fiberglass post and 1 mm ferrule. The models were imported into the analysis software with parameters for mechanical structural testing using the maximum principal stress and the tensile strength as the analysis criteria. Then, load of 150 N was applied at the cingulum with 45° slope to the long axis of the tooth, with the fixed base for each model. The type of marginal preparation affected the stresses concentration in endodontically treated teeth and in the zirconia crown margin. Considering the stress magnitude only, BOPT is a viable option for anterior monolithic zirconia crowns; however, with the highest stress magnitude at the restoration margin.

Objective: Evaluate the effect of four preparation designs, two ceramic materials, and two occlusion contact types on the stress distribution of ceramic veneer in upper central incisor. Material and methods:  3D-models were performed in the modeling software containing enamel, dentin, pulp, periodontal ligament and a base of polyurethane resin. The designs were modeled and exported to the computer aided engineering software to perform the static structural analysis. For the mesh, a total of 155429 tetrahedron elements and 271683 nodes were used, after a 10% convergence test. Two materials, lithium disilicate and feldspathic ceramics, were simulated. A static load of 100 N on 45º was applied on the incisal and middle thirds of the palatal tooth region, guided by the occlusal plane. The base was constrained in all directions. The Maximum Principal Stress was the failure criteria chosen for the analysis. Results: The Finite Element Analysis showed that the most conservative designs presented less stress concentration on the ceramic veneer. However, the highest tensile stress concentrations were observed on lithium disilicate veneer with extend design, on the middle third. The type of occlusal contact presented different stress patterns among the preparation designs; the incisal contact showed higher stress concentration compared to middle third contact regardless the ceramic material. Conclusions: To perform a ceramic veneer in upper central incisor, the feldspathic ceramic presented promising results and should be recommended when the extended design was done. Regarding contact types, the incisal contact is more prone to failure regardless the ceramic and preparation design.   Keywords Ceramics; Dental veneers; Finite element analysis.

Dental implant-supported prosthesis are widely used in oral reconstruction of totally edentulous patients. Nonetheless, one of the most common failures in these cases is caused by overloading from improper occlusion. The aim of this work was to determine if the occlusal scheme influences the biomechanical response in implant-supported dental prostheses. Searches were conduct is several databases (PubMed/MEDLINE, The Cochrane Library, Web of Science, Scopus, LILACS, and Opengrey). We found 632 publications and 521 studies remained after removing duplicates. After applying the inclusion criteria, five studies were used in this systematic review: one clinical trial, one retrospective clinical trial, one in vitro and two in silico. The results show the lack of clinical and laboratory studies about occlusion in implant-supported prostheses. Although there are several studies regarding implant occlusion schemes, there remains a lack of scientific evidence to support that one specific occlusal scheme is superior to another, or to help define the ideal occlusal scheme that improves the clinical outcome. It can be concluded, however, that the proper distribution of loads and the absence of occlusal interferences can increase implant longevity. Thus, more clinical and laboratory studies must be carried out to obtain an occlusal scheme that favors the clinical success of implant rehabilitation.

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Objective: to analyze the stress distribution in a 3D model that simulates second molar mesialization using two different types of mini-implants. Material and Methods: a mandible bone model was obtained by recomposing a computed tomography performed by a software program. The cortical and trabecular bone, a lower second molar, periodontal ligament, orthodontic tube, resin cement and the mini-implants were designed and modeled using the Rhinoceros 4.0 software program. The characteristics of self-drilling orthodontic mini-implants were: one with 7 mm length, 1 mm transmucosal neck section and 1.6 mm diameter and another with 5 mm length and 1.5 mm diameter. A total of 235.161 and 224.505 elements were used for the mesh. These models were inserted into the bone block and then subjected to loads of 200 cN (centinewton). The results were calculated and analyzed by the Ansys 17.0 software program for qualitative verification through displacement and maximum principal stress maps. Results: it was possible to observe that the periodontal ligament presented low displacement and stress values. However, the physiological values presented are among those capable to provide orthodontic movement, with compression and tensile area visualization staggered between 0.1 and -0.1 MPa (megapascal). Conclusion: within the limitations of the study, the mini-implants tested showed similar results where the load on the tooth allowed dental displacement (molar mesialization), with a tendency to rotate it, theoretically allowing the second molar to take the location of the first molar. KEYWORDSFinite element analysis; Orthodontic anchorage procedures; Fixed orthodontic appliances; Mini dental implants; Tooth dislocation. RESUMOObjetivo: analisar a distribuição de tensões em um modelo 3D que simula a mesialização do segundo molar usando dois tipos diferentes de mini-implantes. Material e Métodos: um modelo de osso mandibular foi obtido por recomposição de uma tomografia computadorizada realizada por um software. O osso cortical e trabecular, um segundo molar inferior, ligamento periodontal, tubo ortodôntico, cimento resinoso e os mini-implantes foram projetados e modelados no software Rhinoceros 4.0. As características dos mini-implantes ortodônticos auto perfurantes foram: um com 7 mm de comprimento, 1 mm de secção transmucosa e 1,6 mm de diâmetro e outro com 5 mm de