کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1421252 986401 2013 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Residual stresses in Y-TZP crowns due to changes in the thermal contraction coefficient of veneers
موضوعات مرتبط
مهندسی و علوم پایه مهندسی مواد بیومتریال
پیش نمایش صفحه اول مقاله
Residual stresses in Y-TZP crowns due to changes in the thermal contraction coefficient of veneers
چکیده انگلیسی

ObjectiveTo test the hypothesis that the difference in the coefficient of thermal contraction of the veneering porcelain above (αliquid) and below (αsolid) its Tg plays an important role in stress development during a fast cooling protocol of Y-TZP crowns.MethodsThree-dimensional finite element models of veneered Y-TZP crowns were developed. Heat transfer analyses were conducted with two cooling protocols: slow (group A) and fast (groups B–F). Calculated temperatures as a function of time were used to determine the thermal stresses. Porcelain αsolid was kept constant while its αliquid was varied, creating different Δα/αsolid conditions: 0, 1, 1.5, 2 and 3 (groups B–F, respectively). Maximum (σ1) and minimum (σ3) residual principal stress distributions in the porcelain layer were compared.ResultsFor the slowly cooled crown, positive σ1 were observed in the porcelain, orientated perpendicular to the core–veneer interface (“radial” orientation). Simultaneously, negative σ3 were observed within the porcelain, mostly in a hoop orientation (“hoop–arch”). For rapidly cooled crowns, stress patterns varied depending on Δα/αsolid ratios. For groups B and C, the patterns were similar to those found in group A for σ1 (“radial”) and σ3 (“hoop–arch”). For groups D–F, stress distribution changed significantly, with σ1 forming a “hoop-arch” pattern while σ3 developed a “radial” pattern.SignificanceHoop tensile stresses generated in the veneering layer during fast cooling protocols due to porcelain high Δα/αsolid ratio will facilitate flaw propagation from the surface toward the core, which negatively affects the potential clinical longevity of a crown.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Dental Materials - Volume 29, Issue 5, May 2013, Pages 594–601
نویسندگان
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