Browsing by Author "Nishant Kumar Singh"

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Comparison between all-on-four and all-on-six treatment concepts on stress distribution for full-mouth rehabilitation using three-dimensional finite element analysis: A biomechanical study
(Wolters Kluwer Medknow Publications, 2023) Aishwarya Pandey; Farhan Durrani; Sanjay Kumar Rai; Nishant Kumar Singh; Preeti Singh; Rati Verma; Jitendra Kumar
Purpose: The current study intended to provide a comparison of biomechanical behaviors of two different treatment concepts for full-mouth rehabilitation with dental implants placed according to the 'All-on-four' concept and 'All-on-six' concept with analysis of the stress patterns of the implant support system using three-dimensional finite element analysis (FEA). Materials and Methods: The edentulous mandible was treated with two different implant designs. 'All-on-Four' implant placement concept was used in Model 1 with two central axial implants and two distally tilted implants at 17° and in Model 2, 'All-on-Six' concept was applied with six vertically placed implants. Individual vertical and horizontal load of 100 N and oblique load of 141 N at 45° was applied to all implants. To evaluate and compare the results in terms of maximum principal stress, we used FEA. Results: All-on-six showed smaller maximum principal stress values on the cortical bone and implants. However, maximum principal stress values obtained on trabecular bone was smaller in the All-on-four design for vertical and horizontal loading conditions. Conclusions: The All-on-six approach showed more favorable biomechanical behavior. © 2023 Indian Society of Periodontology | Published by Wolters Kluwer - Medknow.
Possible vascular injury due to screw eccentricity in minimally invasive total hip arthroplasty
(Medknow Publications, 2017) Nishant Kumar Singh; Sanjay Kumar Rai; Amit Rastogi
Background: Vascular injury during minimally invasive total hip arthroplasty (THA) is uncommon, yet a well-recognized and serious issue. It emerges because of non-visibility of vascular structures proximal to the pelvic bone during reaming, drilling holes, and fixing of screws. Numerous studies have found that screw fixation during cementless THA is beneficial for the initial stability of cup; yet, no anatomical guidelines support angular eccentric screw fixation. Materials and Methods: In this study, we obtained the pelvic arterial-phase computed tomographic data of thirty eight humans and reconstructed the three-dimensional models of osseous and vessel structures. We performed the surgical simulation to fix these structures with cementless cups and screws with angular eccentricities. Results: The effect of screw eccentricities (angular eccentricities of ±17° and ±34°) on the vascular injury was determined. Measurement between screw and adjoining vessels was performed and analyzed statistically to ascertain a comparative risk study for blood vessels that are not visible during surgery. Conclusion: Authors similarly discussed the significant absence of appreciation of quadrant systems proposed by Wasielewski et al. on eccentric screws. Adjustment of quadrant systems provided by Wasielewski et al. is required for acetabular implants with eccentric holes for fixation of acetabular screws. © 2017 Indian Journal of Orthopaedics | Published by Wolters Kluwer-Medknow.