The purpose of the study was to investigate the influence of 3D printing parameters on fit and internal gap of 3D printed resin dental prosthesis. The dental model was simulated and fabricated for three-unit prostheses with two implants. One hundred prostheses were 3D printed with two-layer thicknesses for five build orientations using a resin (NextDent C&B; 3D systems, Soesterberg, The Netherlands) and ten prostheses were manufactured with a milling resin as control. The prostheses were seated and scanned with micro-CT (computerized tomography). Internal gap volume (IGV) was calculated from 3D reconstructed micro-CT data. IGV, marginal fit, and lengths of internal gaps were measured, and the values were analyzed statistically. For the 3D printed prostheses, IGV was smaller at 45°, 60°, and 90° compared to other build orientations. The marginal fit evaluated by absolute marginal discrepancy was smaller than other build orientations at 45° and 60°. IGV was smaller at 50 µm layer thickness than at 100 µm layer thickness, but the marginal fit was smaller at 100 µm layer thickness than at 50 µm layer thickness. The 3D printed prosthesis had smaller internal gap than the milled prosthesis. The marginal fit of the 3D printed resin prosthesis was clinically acceptable, and build orientation of 45° and 60° would be recommended when considering fit and internal gap.

Bone marrow mesenchymal stem cells (BM MSCs) can differentiate into multi-lineage tissues. However, obtaining BM MSCs by aspiration is difficult and can be painful; therefore peripheral blood (PB) MSCs might provide an easier alternative for clinical applications. Here, we show that circulating PB MSCs proliferate as efficiently as BM MSCs in the presence of extracellular matrix (ECM) and that differentiation potential into osteoblast in vitro and in vivo . Both BM MSCs and PB MSCs developed into new bone when subcutaneously transplanted into immune-compromised mice using hydroxyapatite/tricalcium phosphate as a carrier. Furthermore, LY294002 and Wortmannin blocked mesenchymal stem cell attachment in a dose-dependent manner, suggesting a role of phosphatidylinositol 3-kinase in MSC attachment. Our data showed that the growth of PB MSCs could be regulated by interaction with the ECM and that these cells could differentiate into osteoblasts, suggesting their potential for clinical applications.

The objective of this study was to investigate the reproducibility of milled acrylic resin and zirconia models using three-dimensional analysis.Material and Methods: Zirconia discs and acrylic resin blocks were milled to make models. Each model was scanned with a model scanner. The zirconia models were superimposed with other zirconia model, and the acrylic resin models were superimposed with other acrylic resin model threedimensionally. Root-mean-square (RMS) values were obtained. Distances between two superimposed models were measured. Statistical significances were tested using the Mann-Whitney U test and t-test. Results:The RMS values of the zirconia model and the acrylic resin model were not significantly different (p≥0.05). At the premolar site, distances between the zirconia models at the upper axial and at the lower axial wall were significantly smaller than for the acrylic resin models (p<0.05). At the molar site, distance between the zirconia models at the lower axial wall was significantly smaller than for the acrylic resin models (p<0.05). Conclusion:Although there is a difference in reproducibility between the milled acrylic resin model and the zirconia model in the localized region, no significant difference was found in the whole model.