Study On The Biocompatibility Of Nano-composite Resin Filtek^TMZ350 Towards Pulp Tissue

Objective The purpose of this study is to evaluate biocompatibility of nano-composite resin FiltekTM Z350 by comparing it with two other dental restorative materials, namely compomer Dyract-AP and composite resin TPH, through in vitro and in vivo experiments.Methods In vitro study:Pulp fibroblasts were collected and cultured from healthy human dental pulp by tissue explant method. Slices in cylinder form with diameter of 5mm and thickness of 2mm were made of three different kinds of dental restorative material (FiltekTM Z350,Dyract-AP,TPH). Maceration extracts were obtained by immersing the slices into DMEM. Diluted solutions of extracts at 50%,25%and 12.5%concentrations were prepared. Fifth generation pulp fibroblasts were cultured in medium containing different concentrations of maceration extracts(100%,50%,25%and 12.5%) accordingly. At time points of 24h,72h,120h and 168h after culture, cytotoxicity of dentin bonding agents to human pulp fibroblasts was measured with Methyl-thiazolyl-tetrazolium(MTT) method. Growth of pulp fibroblasts on surfaces of slices were observed with scanning electron microscope(SEM).In vivo study:Deep Class V cavities approximate to pulp(n=20) were prepared in buccal/labial surfaces of 20 teeth in three adult male beagle dogs. Cavities were divided into four groups at random. FiltekTM Z350 resin, Dyract AP compomer and TPH resin were used to restore cavities in three experimental groups respectively and glass ionomer cement(GIC) was used in control group. All cavities were treated with Clearfil SE BOND before filling. Intact healthy teeth were used as blank control. Animals were sacrificed after 7 days,30 days and 90 days and specimen were obtained, fixed and decalcificated subsequently. Effects of the three kinds of material on pulp tissue were observed under microscope.Results In vitro study:At 25%concentration of maceration extracts, FiltekTM Z350 nano-composite resin manifested the least cytotoxicity among three kinds of material tested (P<0.05). Under SEM, observation revealed good adherence of pulp cells to all kinds of material.7 days after restoration, mild inflammatory response of pulp tissue was observed in most animal specimens regardless of material used, whereas at 30 and 90 days after restoration, normal histological characteristics were observed in almost all specimens except TPH resin group, in which histological structure disturbance of dentin cell layer was detected in some specimens. The index of histological structure disturbance in TPH resin group rated significant higher than that in other groups (P< 0.05).Conclusion In vitro study revealed that all three dental restorative materials had satisfactory biocompatibility. FiltekTM Z350 nano-composite resin exhibited less cytotoxicity than Dyract AP compomer and TPH resin. In vivo study demonstrated that biocompatibility of FiltekTM Z350 was similar to that of AP and GIC, and, better than that of TPH.