After washing with PBS, the gels were stored in PBS at 4°C. Before platting the cells, the gel was exposed to UV for 15 min for the sterilization and replace PBS with complete culture medium for 1 h at 37°C.

Implant materials

The bone substitutes Maxgraft® (AP) and Maxresorb® (SB) were obtained from the company Botiss (botiss dental GmbH, Berlin, Germany). Maxgraft® is a sterile, high-safety allograft product (AP), derived from human donor bone. It is processed by an audited and certified bone bank (Cells⁺ Tissue Bank Austria, Berlin, Germany). In contrast, Maxresorb® is a fully synthetic bone graft substitute (SB) with controlled resorption properties. It is a homogenous composition of 60% hydroxyapatite and 40% beta-tri-calcium phosphate. SB maintains the volume and mechanical stability over a long time period. The osteoconductivity of SB is achieved by a matrix of interconnecting pores and a very high porosity of approximately 80%, as well as pore sizes from 200 to 800 μm (www.botiss.com). Experiments with AP and SB were done with solid blocks (10 × 10 × 20 mm cancellous block). PA was produced in our lab (see above), and silicone-based implant materials were obtained from Vivomed (Downpatrick, UK) as tubes. Silicone tubes were cut in pieces with a size which is similar to that of AP and SB.

Implant materials were washed with PBS or cell culture medium before use. DFCs and dNC-PCs were seeded onto materials for indicated periods of time. For the isolation of total RNA and the estimation of vital cell numbers, implant materials with cells were transferred to a fresh well with cell culture medium. For the evaluation of apoptosis induction, cell culture eluates were produced by incubating 0.1 mL of bone substitutes or soft materials in 1-mL standard medium at 37°C for 24 h.