Figure 2. NAC protects human dental pulp stromal cells from undergoing cell death and growth inhibition after ex vivo composite restorations. (A) Three freshly extracted human 3rd molars from the same individual were divided into 3 groups where (A) no restoration, (B) composite restoration, or (C) composite restoration with NAC was applied. Restorations were carried out as described in MATERIALS & METHODS. After 5 hrs of restoration, the teeth were fractured, and the pulp tissues were extracted and treated with trypsin-EDTA and collagenase to obtain single-cell suspensions, after which they were cultured in media with β-glycerophosphate (10 mM) and ascorbic acid (50 µg/mL). After 4 wks of culture, photographs were taken via an inverted microscope (mag. 20X). (B) Human dental pulp stromal cells were prepared as described in Fig. 2A. After 6 wks of culture, dental pulp stromal cells were trypsinized, and the cell numbers were determined in each group. The cells were counted in triplicate and presented as mean ± standard deviation. p 0.001 for differences between the composite- and ‘composite with NAC’-treated groups. (C) Human dental pulp stromal cells were prepared as described in Fig. 2A. After 6 wks of culture, supernatants were removed from the cultures, and the levels of VEGF secretion in dental pulp stromal cells (5 x 10⁵/mL) were assessed by a sensitive and specific ELISA for VEGF. p 0.001 for differences between the composite- and ‘composite with NAC’-treated groups.