[Comparative study on fracture toughness of digital light processing three-dimensional printing zirconia and milled zirconia].

Objective: To investigate the influence of digital light processing (DLP) and computer numerical controlmilling (CNC) on the mechanical behavior of zirconia. Methods: Prepared DLP samples (experimental group, n=52) and CNC samples (control group, n=52) with 12 samples in each group were randomly selected using random number table to measure density, grain size and crystal phase composition. According to the different methods fracture toughness test, the samples were divided into indentation method group (IM) and single-edge-V-notch-beam group (SEVNB), with 30 DLP and 30 CNC samples in IM group, 10 DLP and 10 CNC samples in SEVNB group. The IM group was tested under three different loads (49.03 N, 98.07 N, 196.10 N), there were 10 samples for each load and each sample was tested at 15 points, and the load with the ratio of crack length to indentation diagonal length greater than 2.5 was selected as the indentation load to calculate its IM fracture toughness. At the same time, the SEVNB group was tested with four point bending test to record the maximum load at the time of fracture and calculate the SEVNB fracture toughness. Finally, the indentation and fracture surface were observed using optical microscope and scanning electron microscope, and the results of DLP group and CNC group were further compared to explore the difference in fracture mechanism. Results: The microstructure of DLP and CNC zirconia was basically the same, the density of DLP group was (6.020±0.021) g/cm3, the grain size was (0.603±0.033) µm; the density of CNC group was (6.038±0.012) g/cm3, the grain size was (0.591±0.033) µm. Both groups were composed of tetragonal zirconia. The load of 196.10 N was chosen as the indentation load for two groups to calculate the IM fracture toughness. In terms of fracture toughness, there was no significant difference between the two groups (P>0.05). Scanning electron microscope images of fracture surface showed the intergranular fracture was the leading fracture mode of two groups. The IM and SEVNB fracture toughness of DLP zirconia were (6.111±0.179) MPa·m1/2 and (7.221±0.809) MPa·m1/2, respectively. The IM and SEVNB fracture toughness of CNC zirconia were (6.126±0.383) MPa·m1/2 and (7.408±0.533) MPa·m1/2, respectively. Conclusions: The microstructure of DLP and CNC zirconia is almost the same, and there is little difference in the fracture toughness of zirconia between two processing technologies.

[Analysis of the clinicopathologic features as well as diagnosis and treatment of 59 patients with Castleman disease].

Objective: To investigate the clinicopathologic features, treatment, and prognosis in patients with Castleman disease (CD) . Methods: We retrospectively analyzed the clinicopathologic data of 59 patients for whom a diagnosis of Castleman disease was confirmed using pathological examination from October 2011 to October 2019 at the Henan Cancer Hospital. The patients were divided into the following two groups as per the following clinical classifications: unicentric CD (UCD, n=47) and multicentric CD (MCD, n=12) . Data on clinical manifestations, laboratory findings, treatment, and prognosis were analyzed. Results: There was no significant difference in the median age and the ratio of male to female between the UCD and MCD. UCD was characterized by asymptomatic enlargement of the single lymph node. The main pathological type was hyaline vascular histopathology (83.0%) . Of these, 44 patients chose surgical resection, and their prognosis was good. Treatment. MCD was characterized by multiple enlarged superficial and/or deep lymph nodes with B symptoms, weakness, and hepatosplenomegaly. Anemia, hypoproteinemia, and globulin level were increased on laboratory examinations. Plasmacyte histopathology was the main pathological type and was present in about 50.0% of the subjects. Only chemotherapy was performed for these MCD patients, followed by chemotherapy or chemotherapy followed by radiotherapy, and the efficient was 58.3% (7/12) . Conclusions: UCD, characterized by asymptomatic enlargement of the single lymph node, shows good postoperative prognosis. MCD has relatively complex clinical manifestations and poor prognosis, and optimal treatment is yet to be established.