Biocompatibility of new nanostructural materials based on active silicate systems and hydroxyapatite: In vitro and in vivo study

Abstract

Aim: To evaluate in vitro cytotoxicity and in vivo inflammatory response to new nanostructural materials based on active calcium silicate systems (CS) and hydroxyapatite (HA-CS). Methodology: Cytotoxicity of eluates of new nanostructural noncommercial materials CS and HA-CS, and MTA (White MTA, Angelus® Soluções Odontológicas, Londrina, Brazil) as a control, were tested using the MTT assay on MRC-5 cells. Eluates of set materials were tested in 100% and 50% concentrations, 24 h, 7 days and 21 days post-elution. The pH values were determined for undiluted eluates of set materials. Polyethylene tubes containing the test materials (CS, HA-CS, MTA) were implanted in subcutaneous tissue of Wistar rats. Histopathological examinations were conducted at 7, 15, 30 and 60 days after the implantation. Data were statistically analyzed using three-way and one-way anova Tukey's post hoc test as well as Kruskall-Wallis test with Dunn's post hoc test at α = 0.05. Results: All materials significantly reduced cell viability; especially when undiluted eluates were used (P < 0.001). After 24 h elution, cell viability was 10 ± 1.8%, 49.5 ± 4.2% and 61 ± 7.4%, for MTA, and HA-CS, respectively. However, CS and HA-CS were significantly less toxic than the control material MTA (P < 0.05). Cytotoxicity could be at least partially attributed to pH kinetics over time. Dilution of eluates of all tested materials resulted in better cell survival. Histopathological examination indicated similar inflammatory reaction, vascular congestion and connective tissue integrity associated with CS, HA-CS and MTA at each observation period (P > 0.05). The only significant difference was found for capsule thickness, that is thicker capsule was associated with HA-CS compared to MTA at 60 days (P = 0.0039). HA-CS induced moderately thick capsules (median score 3, score range 2-3), whereas MTA resulted in thin capsule formation (median score 2, score range 1-3). Conclusions: Evaluation of cytotoxicity and inflammatory response indicated better biocompatibility of CS and HA-CS, in comparison with MTA (White MTA, Angelus® Soluções Odontológicas, Londrina, Brazil).