Evaluation of a new hydroxiapatite covered nanometric implant surface. An in vivo study in rats

Author(s)

Paula Gabriela Faciola Pessôa de Oliveira

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Odontologia de Ribeirão Preto (PCARP/BC)
• Defense date: 2018-08-24

Examining board members

Sergio Luis Scombatti de Souza; Ana Lúcia Pompéia Fraga de Almeida; Daniela Bazan Palioto Bulle; Armando Rodrigues Lopes Pereira Neto

• Advisor: Sergio Luis Scombatti de Souza

Abstract

Implant therapy has been a predictable alternative to replace partially or totally missing teeth. However, systemic disease such as diabetes mellitus (DM) may negatively influence the osseointegration. Changes in microtopography and implant surface are two strategies used to promote better bone anchorage. Thus, taking into account the development of new implant surface to improve qualitative and quantitative osseointegration, and on the other hand the impaired healing of DM, which can be used as models of subjects with impaired bone repair. The aim of this in vivo study was to evaluate the biologic response of a new implant surface, modified by the addition of nano-hydroxyapatite through three-dimensional (3D) evaluation using micro-CT: percent intersection surface (IS/TS, %), percent bone volume (BV/TV, %), bone surface/volume ratio (BS/BV, mm), trabecular separation (Tb.Sp, %) and total porosity (To.Po, %); histological analysis: bone to implant contact (BIC, %) and bone area fraction occupancy (BAFO, %); nanomechanical properties: elastic modulus (EM) and hardness (H) and gene expression analysis: runt-related transcription factor 2 (Runx2), alkaline phosphatase (Alp), osteocalcin (Oc), osteopontin (Opn), receptor activator of nuclear factorkappa B (Rank), receptor activator of nuclear factor-kappa B ligand (Rank-L) and osteoprotegerin (Opg). Mini implants (machined, double acid etched and with addition of nano-hydroxyapatite) were installed in tibias of healthy rats (n=36) and diabetic rats (n=36). The animals were euthanized at 7 and 30 days. The right tibia were removed and fixed for micro-CT, histological and nanomechanical analysis and the left for evaluation of gene expression. Data were assessed through analysis of variance + Tukey test and are presented as a function of mean and 95% confidence interval. The % IS/TS showed that NANO group presented statistically significant difference when compared to machined and DAE, regardless of time and systemic condition. BV/TV (%), BS/BV (mm) and To.Po (%) demonstrated higher values for NANO group in all evaluated time point and irrespective of systemic condition, but BS/BV 30 days (healthy rat) and 7 and 30 days (diabetic rat). The results of Tb.Sp (%) revealed statistical differences for NANO diabetic group at 7 and 30 days. From the histomorphometric analysis, NANO surface presented higher % BIC and % BAFO when compared to machined and DAE (data evaluated as a function of implant surface). Additionally, NANO surface presented higher % BIC and % BAFO than machined and DAE, with statistically significant differences (data as a function of time and implant surface). NANO surface depicted higher EM and H values when compared to machined and DAE surfaces, with statistically significant differences (data as a function of time and implant surface). Evaluating all factors (time, systemic condition and surface treatment), the relative expression of Rank showed that NANO surface presented the best results at 7 days (diabetic rats). Furthermore the levels of Runx2, Alp, Oc and Opn suggest an increase in osteoblasts proliferation, especially in early stages of osseointegration. Nano-hydroxyapatite coated implants presented promising results and can be considered an important tool to compensate impaired bone healing reported in diabetics (AU)

• FAPESP's process: 15/09879-0 - Evaluation of a new hydroxiapatite covered nanometric implant surface. An in vitro study in rats
• Grantee: Paula Gabriela Faciola Pessoa de Oliveira
• Support Opportunities: Scholarships in Brazil - Doctorate