A comparative histological, histochemical and immunohistochemical study of the biocompatibility of three different nano-restorative materials implanted in rats’ connective tissue

This study was conducted to evaluate the subcutaneous connective tissue reaction to the newly-developed nano-restorative materials: Filtek Supreme XT, Ceram X and Ketac N100. These materials were placed in polyethylene tubes and implanted into the dorsal connective tissue of albino rats. Tissue biopsies were collected and histologically examined 1, 4 and 8 weeks after the implantation procedure. The presence of inflammation, type and location of inflammatory cells, calcification and fibrous tissue formation were recorded. Mast cells and macrophages were quantitatively assessed using toluidine blue stain and CD68 immunoexpression respectively. Microscopic analysis revealed that Ceram X and Filtek supreme XT produced an irritating effect only during the initial post implant period. Ketac N100 caused the severest irritation, producing an inflammatory reaction which ranged from moderate to intense over the entire experimental period. Comparing mast cell number and CD 68 area % between the control and the three tested materials, there was a significant difference throughout the experiment (p=0.000). The highest mast cell number was recorded in the Ketac N group after one week, while the greatest CD 68 immunoexpression was noted after 4 weeks in the same group. It can be concluded that the tested materials induce different and time dependent inflammatory reactions and that Ketac N 100 is less biocompatible compared to Filtek supreme NT and Ceram X. INTRODUCTION Biomaterials science is in the midst of the largest transition in its history in terms of refocusing and embracing new and exciting technologies (Bayne, 2005). Nanotechnology, also known as molecular nanotechnology or molecular engineering, is the production of functional materials and structures in the range of 0.1 to 100 nanometers—the nanoscale—by various physical or chemical methods (Kirk et al, 1991). In the current decade, the revolutionary development of nanotechnology has become the most highly energized discipline in science and technology (Schultz, 2000). The intense interest in using nanomaterials stems from the idea that they may be used to manipulate the structure of materials to provide dramatic improvements in electrical, chemical, mechanical and optical properties (Whitesides and Christopher, 2001). One of the most significant contributions to dentistry has been the development of resin-based composite technology. A dental composite can be defined as a three dimensional combination of at least two chemically different materials. Basically, they are composed of an organic matrix, load particles (glass, quartz, milted silica) and a bonding agent, usually an organic silane, with a dual characteristic enabling chemical bonding with the load particle and co-polymerization with the monomers of the organic matrix (Peutzfeldt , 1997). Adhesively bonded composites have the advantage of conserving sound tooth structure with the potential for tooth reinforcement, while at the same time providing a cosmetically acceptable restoration (Fortin and Vargas, 2000). In