Experimental and FE displacement and polymerization stress of bonded restorations as a function of the C-Factor, volume and substrate stiffness

Author(s)

Cidreira Boaro, Leticia Cristina ^[1] ; Brandt, William Cunha ^[1] ; Cruz Meira, Josete Barbosa ^[2] ; Rodrigues, Flavia Pires ^[3] ; Palin, William M. ^[3] ; Braga, Roberto Ruggiero ^[2]

Affiliation

^[1] Univ Santo Amaro, Dept Dent, Implantol Unit, BR-04829300 Sao Paulo - Brazil

^[2] Univ Sao Paulo, Sch Dent, Dept Dent Mat, Sao Paulo - Brazil

^[3] Univ Birmingham, Sch Dent, Biomat Unit, Birmingham, W Midlands - England

• Document type: Journal article
• Source: Journal of Dentistry; v. 42, n. 2, p. 140-148, FEB 2014.
• Web of Science Citations: 13

Abstract

Objectives: To determine the free surface displacement of resin-composite restorations as a function of the C-Factor, volume and substrate stiffness, and to compare the results with interfacial stress values evaluated by finite element analysis (FEA). Methods: Surface displacement was determined by an extensometer using restorations with 4 or 6 mm diameter and 1 or 2 mm depth, prepared in either bovine teeth or glass. The maximum displacement of the free surface was monitored for 5 min from the start of photoactivation, at an acquisition rate of 1 s(-1). Axisymmetric cavity models were performed by FEA. Structural stiffness and maximum stresses were investigated. Results: For glass, displacement showed a stronger correlation with volume (r = 0.771) than with C-Factor (r = 0.395, p < 0.001 for both). For teeth, a stronger correlation was found with C-Factor (r = 0.709; p < 0.001) than with volume (r = 0.546, p < 0.001). For similar dimensions, stress and displacement were defined by stiffness. Simultaneous increases in volume and C-Factor led to increases in stress and surface displacement. Maximum stresses were located at the cavosurface angle, internal angle (glass) and at the dentine-enamel junction (teeth). The displacement of the restoration's free surface was related to interfacial stress development. Conclusions: Structural stiffness seems to affect the shrinkage stress at the tooth/resin-composite interface in bonded restorations. Deep restorations are always problematic because they showed high shear stress, regardless of their width. FEA is the only tool capable of detecting shear stress due to polymerization as there is still no reliable experimental alternative. (C) 2013 Elsevier Ltd. All rights reserved. (AU)

• FAPESP's process: 06/00186-3 - Interfering factors in the mechanical requirement of adhesive restoration interfaces and solutions to reduce them
• Grantee: Flávia Pires Rodrigues
• Support Opportunities: Scholarships in Brazil - Doctorate