Banca de DEFESA: AGNES ANDRADE MARTINS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : AGNES ANDRADE MARTINS
DATE: 22/04/2025
TIME: 14:30
LOCAL: Auditório do Departamento de Odontologia
TITLE:

Physical and in vivo evaluation of a Hydroxyapatite-Silver composite for bone regeneration

KEY WORDS:

Biomaterial. Bone Regeneration. Hydroxyapatite. Silver. Inflammation.

PAGES: 51
BIG AREA: Ciências da Saúde
AREA: Odontologia
SUMMARY:

Introduction: Repairing large bone defects in the craniofacial region is a major challenge in the context of tissue regeneration. Inherent limitations of autogenous grafts render the use of synthetic grafts more convenient, with a special emphasis on hydroxyapatite (HAp), a calcium phosphate that is similar to natural bone. The association of HAp with other materials seeks to overcome the limited mechanical properties of HAp, which may compromise its performance in extensive lesions or those susceptible to mechanical stress. Silver (Ag) is a metal with a well-established antimicrobial activity and has been demonstrating promising osteogenic performance. Objective: To characterize the physical properties of a novel Hap-Ag composite and evaluate its biological performance in an experimental model of critical-size calvarial defect. Methodology: HAp and Hap-Ag powders were obtained and analyzed for morphology by a Scanning Electron Microscope (SEM). Cylindrical pellets obtained from the press and sintering of the powders were subjected to X-ray diffraction (XRD) evaluation to characterize the crystalline phases, the Vickers microhardness test to analyze fracture toughness, and wettability analysis to evaluate hydrophibicity. For the in vivo experiment, 36 male Wistar rats were subjected to the surgery of an 8 mm critical calvaria defect and randomly distributed into three groups (n = 12/group): Control group (CG), untreated defect; HAp group, defect filled with HAp pellet; and Hap-Ag group, defect filled with Hap-Ag pellet. After 90 days of surgery, the animals were euthanized, and calvaria samples were collected and sent for analysis by computerized microtomography (µ-CT), histological analysis including hematoxylin and eosin staining and immunohistochemistry (osteopontin and osteocalcin), quantification of proinflammatory cytokines (IL-1β, TNF-α and IL-6) and relative gene expression (BMP-2, RUNX2, Procollagen 1 and 3, TGF-β, Osterix and eNOS). Data obtained were evaluated by analysis of variance (ANOVA) followed by Tukey's post-test (normal distribution) or by the Kruskall-Wallis test followed by Dunn's post-test (non-normal distribution), with a significance level set at 5%. Results: SEM-FEG images revealed powders with irregular and agglomerated morphology, and the elemental analysis by EDS confirmed the elements of HAp formation and the presence of silver in the HAp/Ag sample. Based on XRD analysis of the pressed pellets, it was possible to observe the formation of HAp with a hexagonal crystalline structure, while for the HAp/Ag pellets there was a reduction in the intensity of the main peaks without the formation of a new phase. The incorporation of Ag into HAp provided an increase in fracture toughness (HAp: 0.66 MPa.m1/2; HAp/Ag: 0.94 MPa.m1/2) and a reduction in the contact angle (36.32° for HAp, and 10.51° for HAp/Ag). Compared to the Control group, defects filled with both biomaterials showed greater bone formation (BV/TV%). The new bone showed less porosities, and a greater number of trabeculae and less trabecular separation. Histological analysis revealed a more advanced stage of bone maturation in the animals in the Hap-Ag group compared to the GC (p<0.05). Higher levels of TNF-α were observed in the Hap-Ag group, in relation to the GC (p<0.05), and of IL-1β in relation to the other groups (p<0.05). A higher gene expression of the pro-collagen 3 (p<0.05) and eNOS (p<0.01) markers was observed in the animals treated with the Hap-Ag composite in comparison to the GC group. Conclusion: Within the limitations of the present study, it can be concluded that the incorporation of Ag into HAp provided the production of a biomaterial with better physical properties and osteoinductive biological potential.

COMMITTEE MEMBERS:
Presidente - 1958729 - RUTHINEIA DIOGENES ALVES UCHOA LINS
Externo ao Programa - 1752956 - EULER MACIEL DANTAS - UFRNExterno à Instituição - RENATA FERREIRA DE CARVALHO LEITÃO