Effect of composites on mRNA gene transcription of gingival keratinocytes

Objectives: This in vitro study evaluated the effect of three different composite materials on the mRNA gene transcription of immortalized human gingival keratinocytes (IHGKs). Methods: Three composite materials were used: Ceram X (Dentsply DeTrey) (CX), Filtek Supreme XT (3M ESPE) (FS) and Filtek Silorane (3M ESPE) (SIL). From each composite material 20 specimens (diameter: 5mm, thickness: 2mm) were prepared and polymerised according to the manufacturer's instructions. Each sample was immersed in 1ml cell culture medium. Half of the samples were stored in a dark box at room temperature for 24 h and the other half for 4 days. At the end of each storage period, the solution, in which the composite samples were immersed, was given on precultured IHGKs. One half of the IHGKs were incubated at 37 degrees for 24 hours and the other half for 4 days. For each tested time period, representative amounts of IHGK were cultivated in untreated medium as controls. After cultivation, the total RNA from the cell cultures was isolated, the integrity and total concentration of RNA was measured and a quantitative real time PCR was performed. Results: Each composite material resulted in a reduced amount of isolated total RNA compared to the control, at both time periods. After 24h, the measured amount of RNA was similar for all three composites. However, after 4 days the RNA-amount isolated from FS and SIL was almost the half of the one measured of CX. For the latter time period, qPCR revealed a significant increased gene expression of the terminal differentiations marker filaggrin and involucin for the groups of FS and SIL. Conclusions: All three tested composite materials had a negative effect on IHGK, concerning the total amount of RNA; however, only FS and SIL were shown to promote the differentiation of the IHGKs.