Impact of post printing cleaning methods on geometry, transmission, roughness parameters, and flexural strength of 3D-printed zirconia

OBJECTIVE

To analyze the impact of different post printing cleaning methods on geometry, transmission, roughness parameters, and flexural strength of additively manufactured zirconia.

METHODS

Disc-shaped specimens (N = 100) were 3D-printed from 3 mol%-yttria-stabilized zirconia (material: LithaCon 3Y 210; printer: CeraFab 7500, Lithoz) and were cleaned with five different methods (n = 20): (A) 25 s of airbrushing with the dedicated cleaning solution (LithaSol 30®, Lithoz) and 1-week storage in a drying oven (40 °C); (B) 25 s airbrushing (LithaSol 30®) without drying oven; (C) 30 s ultrasonic bath (US) filled with Lithasol30®; (D) 300 s US filled with LithaSol 30®; (E) 30 s US filled with LithaSol 30® followed by 40 s of airbrushing (LithaSol 30®). After cleaning, the samples were sintered. Geometry, transmission, roughness (Ra, Rz), characteristic strengths (σ0), and Weibull moduli (m) were analyzed. Statistical analyses were performed using Kolmogorov-Smirnov-, t-, Kruskal-Wallis-, and Mann-Whitney-U-tests (α < 0.05).

RESULTS

Short US (C) resulted in the thickest and widest samples. Highest transmission was found for US combined with airbrushing (E, p ≤ 0.004), followed by D and B (same range, p = 0.070). Roughness was lowest for US combined with airbrushing (E, p ≤ 0.039), followed by A and B (same range, p = 0.172). A (σ0 = 1030 MPa, m = 8.2), B (σ0 = 1165 MPa, m = 9.8), and E (σ0 = 1146 MPa, m = 8.3) were significantly stronger (p < 0.001) and substantially more reliable than C (σ0 = 480 MPa, m = 1.9) and D (σ0 = 486 MPa, m = 2.1).

SIGNIFICANCE

For 3D-printed zirconia, cleaning strategy selection is important. Airbrushing (B) and short US combined with airbrushing (E) were most favorable regarding transmission, roughness, and strength. Ultrasonic cleaning alone was ineffective (short duration) or detrimental (long duration). Strategy E could be particularly promising for hollow or porous structures.

[Lung cancer. Molecular pathology and personalized therapy]

Recent advances in the treatment of non-small cell lung cancer (NSCLC) are based on the identification of so-called driver mutations, resulting in a more personalized treatment setting. Currently about 15% of NSCLC patients benefit from improved treatment protocols based on the genetic background of the tumor. In the last few years cancer immunotherapy has returned to the center of attention and comprises a variety of treatment approaches incorporating adaptive, as well as innate immunity. Current strategies involve the use of monoclonal antitumor antibodies, cancer vaccines, adoptive transfer of ex vivo activated T and NK cells as well as the blockade of so-called immune checkpoints (immune inhibitory pathways). Especially the combination of current treatments with immunotherapy seems promising to achieve highly potent antitumor effects. However, a profound understanding of the dynamic and complex interaction between lung cancer and the host immune system and especially its immune checkpoints is the foundation to identify potential biomarkers for a personalized cancer immunotherapy approach.

[Frozen shoulder. Diagnosis and therapy]

The condition of shoulder stiffness is often called adhesive capsulitis or frozen shoulder. It is regarded as a distinct clinical entity showing a benign and regular course. The major clinical feature is significant reduction in both active and passive range of motion (ROM) accompanied by stage-dependent pain, allowing for a clinical diagnosis. There are primary and secondary forms, the former having an unknown etiology and increased occurrence in patients with metabolic disorders and the latter being seen with prior injury or operation. Three stages, each lasting 4-6 months, mark the clinical course. The progression of the disease is self-limiting and may occasionally resolve in partial restitution. In the first stage ("freezing"), the shoulder continuously loses passive motion and causes worsening pain. Continuing stiffness and improvements in pain and inflammation are characteristic of the second stage ("frozen"). In the third stage ("thawing"), restriction of shoulder motion decreases, and ROM increases. Treatment should be adjusted to these stages. Recommendations include analgesics and joint injections in the first stage and physiotherapy in combination with manual therapy in the second and third stages. In cases of failure, passive exercise under interscalene block, manipulation under general anesthesia, or arthroscopic arthrolysis should be considered.

Polymorphism in sodium-channel alpha 1-subunit (SCN1A) predicts response, TTP, survival, and toxicity in patients with metastatic colorectal cancer treated with 5-FU/oxaliplatin

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Background: Genetic polymorphisms in DNA repair and drug metabolism pathways have been shown to be associated with efficacy and toxicity in patients with metastatic colon cancer treated with 5-FU/oxaliplatin. Recent studies demonstrated in in vitro models that the neurotoxicity associated with oxaliplatin may be linked to an effect on neuronal voltage-gated sodium channels (VGSC). In vitro and in vivo models showed that increased VGSC alpha gene expression was associated with metastatic potential, proliferation and progression of breast and prostate cancer indicating a role in predicting toxicity and efficacy to chemotherapy. We tested the hypothesis whether VGSC gene polymorphisms may predict clinical outcome in a phase II study of combination oxaliplatin with 5-FU in patients with colorectal cancer refractory to 5-FU and/or irinotecan based chemotherapy. Methods: 173 patients were enrolled in this phase II study. 152 patients (male/female; 78/74, median age; 60), median follow up of 18.6 months, response rate of 19%, median time to tumor progression 4.2 months and median survival of 10.3 months. Grade 3/4 toxicity was seen in 60% with GI toxicity of 42% and Neurotoxicity of 11%. The dose of oxaliplatin was 130mg/m2 every 3 weeks and 5-FU was 200mg/m2/day CI for 10 weeks followed by 2 weeks rest. We tested the 12 VGSC genes polymorphisms (SCN1A, 1B, 1A1, 1A2, 1A3, 1A4, 1A5, 1A A3169G SNP, 1A C1702T Nonsense Mutation, 1A T1067A SNP, 1A C3637T SNP, SCN8A Ref SNP 303802). Genomic DNA was extracted from peripheral blood samples and polymorphisms were analyzed by PCR-based RFLP technique. Results: Patients with SCN1A T1067A SNP T/T genotype showed a significant better response rate (p=0.02, 21.9% [23/105] vs. 11.3% [5/44]), TTP (p=0.02, 4.6 months vs. 3.4 months), overall survival (p<.001, 12.3 months. vs. 8.0 months.), and frequency of grade 3/4 toxicity (p=.002) compare to patients with T/A genotype. No A/A genotype was observed. Conclusions: SCN1A gene polymorphism may be potential molecular marker for survival and toxicity in patients with colorectal cancer treated with 5-FU/oxaliplatin. In vitro studies are ongoing to identify the mechanism of resistance by SCN1A.

[Table: see text]

Osteogenic progenitor cell potency after high-dose chemotherapy (COSS-96)

BACKGROUND

Since the first trial of chemotherapy in patients with osteosarcoma the survival rate has gradually improved. For more than two decades, most osteosarcoma patients from Germany, Austria and Switzerland have been treated according to the protocols of the Cooperative Osteosarcoma Study Group (COSS). The uniform treatment concept of a high-dose polychemotherapy pre- and postoperatively improved the survival rate of these patients significantly. One severe side-effect of COSS chemotherapy is multiple osteonecrosis.

PATIENTS AND METHODS

In this study the osteogenic stem cell potency of three different tissue types was elucidated after COSS-96 chemotherapy (high-risk arm). Mononuclear cells were obtained from the periosteum, cartilage and bone marrow of a 17-year-old female with a chondroblastic osteosarcoma. The cells were cultivated for 4 weeks in standard medium and stimulated for osteogenic differentiation after the second passage with dexamethasone, glycerolphosphate and ascorbine acid. Two weeks later, the cell cultures were analysed with respect to cell morphology and immunochemical stainings.

RESULTS

All cells cultures showed an osteoblastic regeneration potential measured by osteocalcin (OC), osteopontin (OP) and alkaline phosphatase (ALP) expression. Compared to other donor tissues and localizations, the fibula periosteum showed significantly higher osteoblast rates in vitro, whereas collagen II, CD34 and CD45 were not expressed in any culture.

CONCLUSION

The results of this study demonstrate the survival of mesenchymal progenitor cells in bone marrow during COSS-96 polychemotherapy, which allows for an osteogenic regeneration in vitro and potentially in vivo.

Extensive H+ release by bone substitutes affects biocompatibilityin vitro testing

Bone substitutes are widespread in orthopedic and trauma surgery to restore critical bony defects and/or promote local bone healing. Cell culture systems have been used for many years to screen biomaterials for their toxicity and biocompatibility. This study applies a human bone marrow cell culture system to evaluate the toxic in vitro effects of soluble components of different bone substitutes, which are already in clinical use. Different specimens of tricalcium phosphates (TCP) (Vitoss, Cerasorb), nondecalcified bovine bone (Lubboc), demineralized human bone matrices (DBM) (Grafton Flex/Putty), and collagen I/III matrix (ACI-Maix) were tested in Dulbecco's modified Eagle's medium (DMEM) and MesenCult culture solution and compared with a biomaterial-free cell culture. Biocompatibility parameters were cell viability evaluated by phase-contrast microscopy and laser flow cytometry, morphology, and the local H(+) release by bone substitutes. There were significant differences (p < 0.05) between the tested biomaterials and culture solutions. Collagen I/III, non-demineralized bovine bone, and TCP materials showed advantages for cell survival over other tested biomaterials (average values of vital cells/mL MesenCult/DMEM: Collagen I/III: 1090/1083; Vitoss: 893/483; Cerasorb: 471/523; Lubboc: 815/410; Grafton Putty: 61/44; Grafton Flex: 149/57). Especially the DBM materials lead to a significant decrease of pH, which is considered to be a major factor for cell death. DMEM culture solution supports cell survival for those bone substitutes that induce an alkaline reaction, whereas MesenCult media promotes cell vitality in biomaterials, which leads to an acidification of culture solution.

[Surgical revision of the pilonidal sinus with single shot antibiosis]

For a therapy of the pilonidal sinus there are different surgical and non-surgical methods to be found in literature. In our surgical wing 140 male patients have been operated on this disease from September 1990 to July 1992. 16 cases out of these 140 were re-operations. Using a special surgical technique we applied the excision with a primary closure under single-shot antibiosis in 139 cases. By modifying this antibiosis prophylaxis we could reach a primary success healing rate of up to 96%. A retrospective study among our patients showed a recurrence rate of 5%.