A finite element analysis study on different angle correction designs for inclined implants in All-On-Four protocol.

BACKGROUND: The aim of this study is to investigate, through finite element analysis (FEA), the biomechanical behavior of the built-in angle corrected dental implant versus implant with angled multiunit abutment used in All-On-Four treatment protocol. METHODS: Two (3D) finite element models of a simplified edentulous mandible were constructed with two different posterior implant designs based on the All-On-Four protocol. Four implants were placed in each model, the two anterior implants were positioned vertically at the lateral incisor/canine sites. Depending on the implant fixture design in posterior area, there are two models created; Model I; the mandible was rehabilitated with four co-axis (4 mm in diameter × 15 mm in length) implants with distally built-in angle corrected implants (24-degree angle correction) .While Model II, the mandible was rehabilitated with four conventional (4 mm in diameter × 14 mm in length) implants with a distally inclined posterior implants (25 degree) and angled multiunit abutments. CAD software (Solidworks© 2017; Dassault Systems Solidworks Corp) was used to model the desired geometry. Axial and inclined Loads were applied on the two models. A Finite element analysis study was done using an efficient software ANSYS© with specified materials. The resultant equivalent Von-Misses stresses (VMS), maximum principal stresses and deformation analysis were calculated for each part (implants and prosthetic components). RESULTS: When applying axial and non-axial forces, model II (angled multiunit model) showed higher deformation on the level of Ti mesh about 13.286 µm and higher VMS 246.68 MPa than model I (angle corrected implant). Model I exhibited higher maximum stresses 107.83 MPa than Model II 94.988 MPa but the difference was not statistically significant. CONCLUSION: Within the limitation of the FEA study, although angle correcting implant design is showing higher values in maximum principle stresses compared with angled multiunit abutments, model deformation and resultant VMS increased with angled multiunit abutments. The angle correcting designs at implant level have more promising results in terms of deformation and VMS distribution than angle correction at abutment level.

Efficacy and safety of stem cell transplantation for multiple sclerosis: a systematic review and meta-analysis of randomized controlled trials.

Multiple sclerosis (MS) is a common autoimmune neurological disease affecting patients' motor, sensory, and visual performance. Stem Cell Transplantation (SCT) is a medical intervention where a patient is infused with healthy stem cells with the purpose of resetting their immune system. SCT shows remyelinating and immunomodulatory functions in MS patients, representing a potential therapeutic option. We conducted this systematic review and meta-analysis that included randomized control trials (RCTs) of SCT in MS patients to investigate its clinical efficacy and safety, excluding observational and non-English studies. After systematically searching PubMed, Web of Science, Scopus, and Cochrane Library until January 7, 2024, nine RCTs, including 422 patients, were eligible. We assessed the risk of bias (ROB) in these RCTs using Cochrane ROB Tool 1. Data were synthesized using Review Manager version 5.4 and OpenMeta Analyst software. We also conducted subgroup and sensitivity analyses. SCT significantly improved patients expanded disability status scale after 2 months (N = 39, MD = - 0.57, 95% CI [- 1.08, - 0.06], p = 0.03). SCT also reduced brain lesion volume (N = 136, MD = - 7.05, 95% CI [- 10.69, - 3.4], p = 0.0002). The effect on EDSS at 6 and 12 months, timed 25-foot walk (T25-FW), and brain lesions number was nonsignificant. Significant adverse events (AEs) included local reactions at MSCs infusion site (N = 25, RR = 2.55, 95% CI [1.08, 6.03], p = 0.034) and hematological disorders in patients received immunosuppression and autologous hematopoietic SCT (AHSCT) (N = 16, RR = 2.33, 95% CI [1.23, 4.39], p = 0.009). SCT can improve the disability of MS patients and reduce their brain lesion volume. The transplantation was generally safe and tolerated, with no mortality or significant serious AEs, except for infusion site reactions after mesenchymal SCT and hematological AEs after AHSCT. However, generalizing our results is limited by the sparse number of RCTs conducted on AHSCT. Our protocol was registered on PROSPERO with a registration number: CRD42022324141.