Methods: Human gingival Keratinocytes (IHGK), immortalized with the HPV-16 E6/E7 oncogenes, were propagated under standardized cell culture conditions. Two different composite materials were tested: Ceram X (Dentsply DeTrey) (CX) und Filtek Supreme XT (3M ESPE) (FS). 18 composite samples (diameter: 5mm, thickness: 2mm) were prepared from each material and polymerised by using a halogen unit according to the manufacturer's instructions. Directly after polishing, each composite sample was covered with IHGKs at different cell densities. One half of the samples were incubated at 37 degrees for 24 hours (density of IHGK: 5x104 cells) and the other half for 4 days (density of IHGK: 1x105 cells). After incubation, the total RNA from the cell cultures was isolated and total concentration of RNA was measured. In addition, samples were used to analyse the morphology of IHGKs on the composite surface using scanning electron microscopy (SEM). Moreover, IHGKs were subjected to Annexin-5 staining procedure and documented by fluorescence microscopy.
Results: The amount of RNA measured after incubation for 24 h was similar for both materials tested (FS24h: 23,64ng/μl, CX24h: 21,93 ng/μl), while after 4 days the amount of RNA differed significantly (p≤0.05) between the two materials (FS4d: 2,29 ng/µl, CX4d: 11,48 ng/μl). The fluorescence images revealed cell apoptosis. The SEM pictures showed no cells on the surface of FS. On the surface of CX, an inhomogeneous growth of cells in some areas was observed.
Conclusions: Both tested composite materials showed severe effects on the behaviour of IHGKs. Composite materials might have a detrimental influence on cell viability.