RESUMO
Aims: The present study aimed to evaluate the stress distribution of porous tantalum implant and titanium solid implant assisted overdenture (IAO) in mandibular bone by utilizing three-dimensional (3D) finite element (FE) analysis. Materials and Methods: In this FE study, an existing cone-beam volumetric tomography scan of a patient without any maxillofacial anomaly with an available acceptable IAO for mandible was used to attain the compartments of a completely edentulous mandible. Zimmer trabecular implants and locator attachment systems were selected as the case group (Model B), and Zimmer Screw-Vent implants and locator attachment system were chosen for the control (Model A), as overdenture attachments in the present study. The mandibular overdenture was scanned and digitized as a FE model. Two 3D FE models were designed as edentulous lower jaws, each with four implants in the anterior section of the mandible. Three forms of loads were directed to the IAO in each model: Vertical loads on the left first molar vertical molar (VM). Vertical loads on the lower incisors (VI). Inclined force buccolingually applied at left first molar (IM). Results: Under all loading conditions, the maximum strain values in peri-implant bone in Model A were less than Model B. Under VI, the greatest stress value around abutments in both models was about 2-3 times higher than the other loads. Under VM and IM loads, no significant difference was observed between models. Conclusion: Using trabecular metal implants instead of solid implants reduces strain values around both cortical and trabecular bone.
RESUMO
Background. Designing a high strength all-ceramic fixed partial denture with favorable esthetics can be challenging for clinicians; this study aimed to evaluate the effect of connector size and design on the fracture resistance of monolithic zirconia fixed dental prostheses. Methods. Two groups of twenty 3-unit monolithic zirconia (Sirona inCoris TZI, Sirona Dental Systems GmbH) bridges, extending from the mandibular first premolar to the first molar with different connector sizes (9 mm2 and 12 mm2), were divided into two subgroups with different connector designs (round and sharp). The specimens were subjected to the three-point bending test to obtain the fracture-bearing load. The results were reported using descriptive statistics (mean ± standard deviation). Mann-Whitney U test was used to compare the fracture load in two types of designs for each connector size and two connector size types for each connector design. The significance level was considered at P<0.05. Results. The minimum failure load was related to the group with a 9-mm2 connector size and a sharp embrasure design (1054.4±133.89 N), and the highest mean value belonged to the group with 12-mm2 connector size and rounded embrasure design (1599.8±167.09 N). Mann-Whitney U test indicated a significant difference between the mean failure load of the rounded and sharp embrasure designs in the 9-mm2 connector size (P =0.007). However, the difference was insignificant in the 12-mm2 connector size (P =0.075). Conclusion. Sharp embrasure design is not recommended for high-stress areas with restricted occlusogingival height. A 9-mm2 connector size for 3-unit monolithic zirconia fixed dental prosthesis (FDP), which is recommended by the manufacturer, should be used more cautiously.
RESUMO
BACKGROUND: Many studies have reported that macrophages and eosinophils are involved in the pathogenesis of several diseases. To the best of our knowledge, this is the first study comparing macrophages and eosinophils in oral reactive lesions. AIMS: In this study, we aimed to determine the contribution of macrophages and eosinophils to the pathogenesis of oral reactive lesions and the relationships between these biomarkers and the diverse histopathologic features. METHODS: Seventy-five paraffin-embedded tissue samples were assessed in this study. Five categories (15 cases for each group), including peripheral ossifying fibroma, pyogenic granuloma, fibroma, inflammatory fibrous hyperplasia, and peripheral giant-cell granuloma, were considered. Anti-CD68 immunohistochemical and hematoxylin-eosin staining was carried out. RESULTS: We found that macrophages, but not eosinophils, were a significant internal component of oral reactive lesions. Macrophages were observed in high densities in all studied groups and diffusely distributed or clustered throughout these lesions. The number of macrophages was increased in peripheral giant-cell granuloma compared with other groups. CONCLUSIONS: Our findings suggest that macrophages are involved in the pathogenesis and the variation of microscopic features of oral reactive lesions. However, further clinical studies should be conducted to identify the biological process behind macrophages and the molecular interactions of these cells, with the ultimate aim of suggesting a new potential therapeutic target for these lesions. We found that eosinophils were not involved in the fibrotic process and the variation of microscopic features in oral reactive lesions. Our results showed that peripheral giant-cell granulomas highly demonstrated histiocytic characteristics.
