Human gingival keratinocyte response to substances eluted from silorane composite material reveal impact on cell behavior reflected by RNA levels and induction of apoptosis

Abstract

Objectives: The aim of this study was the characterization of siloran-derived composite eluates in conjunction with their putative impact on human gingival keratinocytes (HGK), i.e. levels of total RNA and induction of apoptosis compared to a methacrylate-based material.

Methods: Standardized Filtek™ Silorane specimens (n = 20) were subjected to scanning ion monitoring to detect monomer masses between 100 and 1000, after storage in human saliva, and 75% ethanol for up to 28 days. In order to evaluate the effect on cells, HGK were exposed to eluates from Filtek™ Silorane, Filtek™ Supreme XT and control medium for 1 and 4 days, prior to isolation of total RNA, and Annexin-5 fluorescence labeling indicating induction of apoptosis.

Results: Irrespective of the mode and storage time, SIM identified discrete peaks, corresponding to masses of "393" and "337". In response to both composite eluates, an effect on HGK was reflected by drastically reduced levels of isolated total RNA at each time period (after 1 day: control: 302 ng/μl; Filtek™ Silorane: 128 ng/μl, Filtek™ Supreme XT: 129 ng/μl and after 4 days: control: 528 ng/μl; Filtek™ Silorane: 162 ng/μl, Filtek™ Supreme XT: 166 ng/μl). Exposure to eluates from both composite materials yielded apoptosis induction in HGK, as demonstrated by a significant increase of cells exhibiting Annnexin-5 fluorescence.

Significance: Two distinct peaks were identified, which indicated the presence of corresponding substances. The composite-derived effects on HGK strongly suggest a negative impact on cells, as revealed by a clear reduction of total RNA levels, and significant increase in induction of apoptosis.