# Examination of the Quality of Particulate and Filtered
## 4 Discussion  
In this study, cells derived from mandibular bone chips were evaluated. The isolated cells showed typical stem cell characteristics according to the minimal criteria for defining multipotent mesenchymal stem cells, as suggested by \"The International Society for Cellular Therapy\" [41]. These criteria are among others plastic adherence, spindle-shaped morphology and positive expression of the markers CD73, CD90, and CD105. The outgrowth cells displayed a strong differentiation potential towards the osteogenic lineage irrespective of the patient group. Interestingly, in contrast to ATSCs, BDSCs were found to differentiate into adipocytes only to a marginal extent (data not shown). Similar results have been reported for dental follicle-derived stem cells (DFCs) [42; 43; 44]. The limited differentiation potential indicates a lower plasticity which is correlating with a higher differentiation status towards the osteogenic lineage. Therefore, BDSCs can be expected to possess lower tumorigenicity, as well as a less undifferentiated cell population, or cell differentiating into an unwanted lineage compared to stem cells from other body parts, if differentiated towards the osteoblasts. The pre-commitment towards the osteogenic lineage poses BDSCs as an ideal tool for dental bone grafting [45]. Their differentiation state can be categorized between that of mesenchymal stem cells and osteoblasts. [PERSON] and coworkers classified cells derived from bone of the iliac crest as osteoblast-like, since they stained positive for osteoclast and alkaline phosphatase [46]. Several other research groups identified outgrowing cells of cortical or cancellous bone as osteoblasts, but none of these studies investigated the differentiation potential towards the adipogenic lineage as evidence of an undifferentiated state or for a possible lineage commitment [33; 36]. Parathyroid hormone-related protein (PTHrP) was described as a signaling molecule that affects the differentiation process of mesenchymal stem cells [47]. The differential expression levels of specific PTHrP isoforms might be considered as a molecular signature associated with the respective differentiation state of BDSCs during osteogenesis. Our results showed differences between the outgrowth time-point of cells derived from cortical bone compared to those from cortical-cancellous bone. On average BDSCs of the cortical-cancellous bone chip group showed faster outgrowth compared to the cortical bone chip group. This is supported by similar results from the literature. [PERSON] and colleagues reported outgrowth times of cortical bone-derived cells varying from 6 to 19 days, whereas cells of mixed sources were reported to grow out after 5 to 7 days [33; 36]. It must be noted that donors of the cortical bone chip group were on average younger than donors of the cortical-cancellous bone chip group in our study. This could be a possible confounding reason for the differences in outgrowth. As the material obtained here was a waste product of surgeries, indicated for medical reasons affecting different age groups: Cortical bone material is derived during wisdom teeth removal, which is typical for patients around 20 years of age. Cortical-cancellous bone chips are obtained during implantation surgery, which occurs throughout all ages. Unlike outgrowth time, outgrowth success was comparable in the cortical bone chip group compared to the cortical-cancellous bone chip group and thus, seems to be independent of by age. This is in line with our findings for mesenchymal stem cells and those of others, but in contrast to the results of [PERSON] and colleagues who showed that in vitro outgrowth of iliac crest bone-derived cells was more successful using material of young donors [35; 48; 49]. These contrary results might be explained with the different embryonic origin of the investigated bone chip sources.