Browsing by Subject "Surface Roughness"

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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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    Monitoring of Simulated Erosive Tooth Wear by Cross-Polarization Optical Coherence Tomography
    (2019-06) Alghilan, Maryam Abdulkareem; Hara, Anderson T.; Lippert, Frank; Platt, Jeffrey A.; González-Cabezas, Carlos; Fried, Daniel
    Erosive tooth wear (ETW) is an emerging dental condition manifested clinically as tooth surface loss, eventually impairing the teeth’s structural integrity, function, and esthetics. Both research and practice are in need of a quantitative, non-destructive method to monitor ETW. Cross-polarization optical coherence tomography (CP-OCT), an advanced imaging tool, shows great potential to fulfill this need, but its feasibility and shortcomings remain unclear. In this dissertation, I explored the capability of CP-OCT to monitor ETW in three in vitro studies, one per chapter. Chapter 2 investigated the effects of enamel surface roughness and dental erosion severity on CP-OCT dental surface loss measurements. Chapter 3 tested the effects of enamel surface roughness and dental erosion on CP-OCT enamel thickness measurements at different simulated wear levels. Chapter 4 explored the ability of CP-OCT to quantify the thickness of natural and wornout enamel surfaces and to estimate longitudinally the wear depths resulting from simulated wear. I concluded: (1) enamel surface roughness did not affect CP-OCT measurements of enamel surface loss, however, the estimated error limited the appropriate assessment of the initial stages of dental erosion surface loss using CP-OCT; (2) enamel surface roughness and dental erosion did not affect CP-OCT enamel thickness measurements, and the CP-OCT differentiated the simulated enamel wear levels; and (3) CP-OCT quantified thickness of natural enamel before, during, and after the tooth wear simulation and allowed wear depth estimation following the simulated wear.