Composite polymerization stress as a function of specimen configuration assessed by crack analysis and finite element analysis

Roberto R. Braga, Christof Koplin, Takatsugu Yamamoto, Ken Tyler, Jack Ferracane, Michael V. Swain

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
Pages (from-to)1026-1033
Number of pages8
JournalDental Materials
Volume29
Issue number10
DOIs
StatePublished - Oct 2013

Fingerprint

Finite Element Analysis
Polymerization
Glass
Cracks
Finite element method
Composite materials
Esthetics
Compliance
Analysis of Variance
Geometry
Incidence
Analysis of variance (ANOVA)
Indentation
Rigidity
Restoration
Fracture toughness
Stiffness
Substrates

Keywords

  • Composite
  • Polymerization stress

ASJC Scopus subject areas

  • Dentistry(all)
  • Materials Science(all)
  • Mechanics of Materials
  • Medicine(all)

Cite this

Composite polymerization stress as a function of specimen configuration assessed by crack analysis and finite element analysis. / Braga, Roberto R.; Koplin, Christof; Yamamoto, Takatsugu; Tyler, Ken; Ferracane, Jack; Swain, Michael V.

In: Dental Materials, Vol. 29, No. 10, 10.2013, p. 1026-1033.

Research output: Contribution to journalArticle

Braga, Roberto R. ; Koplin, Christof ; Yamamoto, Takatsugu ; Tyler, Ken ; Ferracane, Jack ; Swain, Michael V. / Composite polymerization stress as a function of specimen configuration assessed by crack analysis and finite element analysis. In: Dental Materials. 2013 ; Vol. 29, No. 10. pp. 1026-1033.
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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.

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