OBJECTIVE: Verify the influence of radiant exposure (H) on composite degree of conversion (DC) and mechanical properties. METHODS: Composite was photoactivated with 3, 6, 12, 24, or 48 J/cm(2). Properties were measured after 48-h dry storage at room temperature. DC was determined on the flat surfaces of 6 mm x 2 mm disk-shaped specimens using FTIR. Flexural strength (FS) and modulus (FM) were accessed by three-point bending. Knoop microhardness number (KHN) was measured on fragments of FS specimens. Data were analyzed by one-way ANOVA/Tukey test, Student's t-test, and regression analysis. RESULTS: DC/top between 6 and 12 J/cm(2) and between 24 and 48 J/cm(2) were not statistically different. No differences between DC/top and bottom were detected. DC/bottom, FM, and KHN/top showed significant differences among all H levels. FS did not vary between 12 and 24 J/cm(2) and between 24 and 48 J/cm(2). KHN/bottom at 3 and 6 J/cm(2) was similar. KHN between top and bottom was different up to 12 J/cm(2). Regression analyses having H as independent variable showed a plateau region above 24 J/cm(2). KHN increased exponentially (top) or linearly (bottom) with DC. FS and FM increased almost linearly with DC/bottom up to 55% conversion. CONCLUSIONS: DC and mechanical properties increased with radiant exposure. Variables leveled off at high H levels. (c) 2007 Wiley Periodicals, Inc.
OBJECTIVE: Verify the influence of radiant exposure (H) on composite degree of conversion (DC) and mechanical properties. METHODS: Composite was photoactivated with 3, 6, 12, 24, or 48 J/cm(2). Properties were measured after 48-h dry storage at room temperature. DC was determined on the flat surfaces of 6 mm x 2 mm disk-shaped specimens using FTIR. Flexural strength (FS) and modulus (FM) were accessed by three-point bending. Knoop microhardness number (KHN) was measured on fragments of FS specimens. Data were analyzed by one-way ANOVA/Tukey test, Student's t-test, and regression analysis. RESULTS:DC/top between 6 and 12 J/cm(2) and between 24 and 48 J/cm(2) were not statistically different. No differences between DC/top and bottom were detected. DC/bottom, FM, and KHN/top showed significant differences among all H levels. FS did not vary between 12 and 24 J/cm(2) and between 24 and 48 J/cm(2). KHN/bottom at 3 and 6 J/cm(2) was similar. KHN between top and bottom was different up to 12 J/cm(2). Regression analyses having H as independent variable showed a plateau region above 24 J/cm(2). KHN increased exponentially (top) or linearly (bottom) with DC. FS and FM increased almost linearly with DC/bottom up to 55% conversion. CONCLUSIONS:DC and mechanical properties increased with radiant exposure. Variables leveled off at high H levels. (c) 2007 Wiley Periodicals, Inc.
Authors: Shi-qiang Gong; Li-Na Niu; Lisa K Kemp; Cynthia K Y Yiu; Heonjune Ryou; Yi-Pin Qi; John D Blizzard; Sergey Nikonov; Martha G Brackett; Regina L W Messer; Christine D Wu; Jing Mao; L Bryan Brister; Frederick A Rueggeberg; Dwayne D Arola; David H Pashley; Franklin R Tay Journal: Acta Biomater Date: 2012-05-29 Impact factor: 8.947
Authors: Naresh Kumar; Muhammad S Zafar; Waheed M Dahri; Muhammad A Khan; Zohaib Khurshid; Shariq Najeeb Journal: J Taibah Univ Med Sci Date: 2018-06-06