TY - JOUR
T1 - Composite polymerization stress as a function of specimen configuration assessed by crack analysis and finite element analysis
AU - Braga, Roberto R.
AU - Koplin, Christof
AU - Yamamoto, Takatsugu
AU - Tyler, Ken
AU - Ferracane, Jack L.
AU - Swain, Michael V.
N1 - Funding Information:
This study was funded by FAPESP (São Paulo Research Foundation) , Grant no. 2009/16267-0 . The authors would like to express their gratitude to Kuraray Medical Inc. for kindly providing the materials used in specimen preparation.
PY - 2013/10
Y1 - 2013/10
N2 - Objectives To test the null hypothesis that polymerization-induced stress was not influenced by cavity dimensions and geometries. Methods Four experimental groups, with different C-factors and specimen volumes were defined using bottom-less glass disks (height: 1 or 2 mm) with a central hole 3 or 6 mm in diameter, and 3 mm wall thickness. Another four groups were created by bonding a glass plate to the bottom of the disks. Additionally, disks with 2-mm height, 3 mm in cavity diameter, and 4.5-mm thick walls were prepared. Vickers indents (9.8 N, 20 s) were made at the top surface at 600 μm from the cavity margin. The lengths of the indentation diagonal and the corner cracks parallel to the cavity margin were measured. Ten minutes after restoration (Majesty Esthetic, Kuraray), cracks were re-measured. Stresses at the indent site were calculated based on glass fracture toughness and increase in crack length. Data were subjected to ANOVA/Tukey or Kruskal-Wallis/Mann-Whitney tests (alpha: 5%, n = 8). Finite element analysis (FEA) was used to estimate stress at the interface and the effective structural rigidity of the substrate. Results Overall, for experimental and FEA results, cavities developed higher stress than bottom-less disks. Increasing wall thickness did not affect stress. When similar geometries and C-factors were compared, higher volumes developed higher stress and had greater incidence of margin cracking. Clinical significance C-factor is a suitable predictor for polymerization stress in low compliance environments, particularly due to its simplicity. However, the influence of cavity size cannot be disregarded especially for the development of marginal cracking. The interaction between size, geometry and stiffness is likely to become more complex according to the complexity of the cavity shape.
AB - Objectives To test the null hypothesis that polymerization-induced stress was not influenced by cavity dimensions and geometries. Methods Four experimental groups, with different C-factors and specimen volumes were defined using bottom-less glass disks (height: 1 or 2 mm) with a central hole 3 or 6 mm in diameter, and 3 mm wall thickness. Another four groups were created by bonding a glass plate to the bottom of the disks. Additionally, disks with 2-mm height, 3 mm in cavity diameter, and 4.5-mm thick walls were prepared. Vickers indents (9.8 N, 20 s) were made at the top surface at 600 μm from the cavity margin. The lengths of the indentation diagonal and the corner cracks parallel to the cavity margin were measured. Ten minutes after restoration (Majesty Esthetic, Kuraray), cracks were re-measured. Stresses at the indent site were calculated based on glass fracture toughness and increase in crack length. Data were subjected to ANOVA/Tukey or Kruskal-Wallis/Mann-Whitney tests (alpha: 5%, n = 8). Finite element analysis (FEA) was used to estimate stress at the interface and the effective structural rigidity of the substrate. Results Overall, for experimental and FEA results, cavities developed higher stress than bottom-less disks. Increasing wall thickness did not affect stress. When similar geometries and C-factors were compared, higher volumes developed higher stress and had greater incidence of margin cracking. Clinical significance C-factor is a suitable predictor for polymerization stress in low compliance environments, particularly due to its simplicity. However, the influence of cavity size cannot be disregarded especially for the development of marginal cracking. The interaction between size, geometry and stiffness is likely to become more complex according to the complexity of the cavity shape.
KW - Composite
KW - Polymerization stress
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U2 - 10.1016/j.dental.2013.07.012
DO - 10.1016/j.dental.2013.07.012
M3 - Article
C2 - 23937867
AN - SCOPUS:84884160849
SN - 0109-5641
VL - 29
SP - 1026
EP - 1033
JO - Dental Materials
JF - Dental Materials
IS - 10
ER -