Browsing by Subject "Mechanical Properties"

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    Effect of Toothbrushing on a Monolithic Dental Zirconia Submitted to an Accelerated Hydrothermal Aging
    (2022) Almajed, Norah; Sochacki, Sabrina Feitosa; Cook, Norman Blaine; Capin, Oriana Reis
    Objectives: The objectives of this study were (1) to evaluate the biaxial flexural strength of monolithic 3Y-TZP ceramic specimens and (2) to assess their surface roughness after being submitted to accelerated hydrothermal aging (simulation 1-10 years of aging); and simulated toothbrushing (simulation 1-10 years of toothbrushing). Materials/Methods: 84 discs of monolithic zirconia (Lava Plus High Translucency Zirconia, 3M ESPE) were prepared, sintered (1450°C, 2h), and randomly allocated into four experimental groups as follows: Control group (CT): no HA and no toothbrushing; 1-year group (1YR): 20 minutes of HA and 10,000 cycles of toothbrushing; 5 years group (5 YR): 100 minutes of HA and 50,000 cycles of toothbrushing; and 10 years group (10 YR): 200 minutes of HA and 100,000 cycles of toothbrushing. Specimens were submitted to autoclave hydrothermal aging at 134°C and 2.0 bar, followed by toothbrush simulation. After aging, specimens in each group were submitted to the biaxial flexural strength test (ISO 6872) using a universal testing machine, and the number of fragments was evaluated. Surface roughness was performed before and after aging using a noncontact profilometer (Ra, Rq, and Rz parameters). For the statistics, one-way analysis of variance (ANOVA) and pairwise comparison were used (α=0.05). Hypothesis: The accelerated hydrothermal aging and simulated toothbrushing will affect the results of the biaxial flexural strength and surface roughness of the zirconia specimens. Results: No significant aging effects were detected for the biaxial flexural strength (p=0.239) for groups CT (874.25±124.61 MPa), 1YR (869.56±132.60 MPa), 5YR (854.40±122.34 MPa), and 10YR (948.55±144.85 MPa). In addition, no significant aging effects were detected comparing the number of fragments, with a minimum of two and a maximum of five fragments (p=0.325). The collected data on the changes in surface roughness after hydrothermal aging and toothbrush simulation showed that for the parameters Ra and Rq, group 1YR presented significantly higher surface roughness than groups 5YR and 10YR. For the parameter Rz, group 1YR presented significantly higher surface roughness than groups 5YR and 10YR. In addition, group 5YR showed higher surface roughness than group 10YR. Conclusion: Hydrothermal aging associated with simulated toothbrushing did not significantly impact the biaxial flexural strength of monolithic 3Y-TZP zirconia. However, there was a significant initial increase in the zirconia surface roughness, which decreased after simulating five and ten years of aging.
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    Effects of combination treatment with alendronate and raloxifene on skeletal properties in a beagle dog model
    (PLOS, 2017-08-09) Allen, Matthew R.; McNerny, Erin; Aref, Mohammad; Organ, Jason M.; Newman, Christopher L.; McGowan, Brian; Jang, Tim; Burr, David B.; Brown, Drew M.; Hammond, Max; Territo, Paul R.; Lin, Chen; Persohn, Scott; Jiang, Lei; Riley, Amanda A.; McCarthy, Brian P.; Hutchins, Gary D.; Wallace, Joseph M.; Anatomy and Cell Biology, School of Medicine
    A growing number of studies have investigated combination treatment as an approach to treat bone disease. The goal of this study was to investigate the combination of alendronate and raloxifene with a particular focus on mechanical properties. To achieve this goal we utilized a large animal model, the beagle dog, used previously by our laboratory to study both alendronate and raloxifene monotherapies. Forty-eight skeletally mature female beagles (1–2 years old) received daily oral treatment: saline vehicle (VEH), alendronate (ALN), raloxifene (RAL) or both ALN and RAL. After 6 and 12 months of treatment, all animals underwent assessment of bone material properties using in vivo reference point indentation (RPI) and skeletal hydration using ultra-short echo magnetic resonance imaging (UTE-MRI). End point measures include imaging, histomorphometry, and mechanical properties. Bone formation rate was significantly lower in iliac crest trabecular bone of animals treated with ALN (-71%) and ALN+RAL (-81%) compared to VEH. In vivo assessment of properties by RPI yielded minimal differences between groups while UTE-MRI showed a RAL and RAL+ALN treatment regimens resulted in significantly higher bound water compared to VEH (+23 and +18%, respectively). There was no significant difference among groups for DXA- or CT-based measures lumbar vertebra, or femoral diaphysis. Ribs of RAL-treated animals were smaller and less dense compared to VEH and although mechanical properties were lower the material-level properties were equivalent to normal. In conclusion, we present a suite of data in a beagle dog model treated for one year with clinically-relevant doses of alendronate and raloxifene monotherapies or combination treatment with both agents. Despite the expected effects on bone remodeling, our study did not find the expected benefit of ALN to BMD or structural mechanical properties, and thus the viability of the combination therapy remains unclear.