Dental Materials
Volume 25, Issue 9 , Pages 1136-1141, September 2009

Bis-GMA co-polymerizations: Influence on conversion, flexural properties, fracture toughness and susceptibility to ethanol degradation of experimental composites

  • Carmem S. Pfeifer

      Affiliations

    • Biomaterials and Oral Biochemistry Department, School of Dentistry, University of São Paulo, Av. Prof. Lineu Prestes, 2227, Sao Paulo, 05508-900, SP, Brazil
    • Corresponding Author InformationCorresponding author. Tel.: +55 11 3091 7842.
    • ,
  • Laura R. Silva

      Affiliations

    • Biomaterials and Oral Biochemistry Department, School of Dentistry, University of São Paulo, Av. Prof. Lineu Prestes, 2227, Sao Paulo, 05508-900, SP, Brazil
    • ,
  • Yoshio Kawano

      Affiliations

    • Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Brazil
    • ,
  • Roberto R. Braga

      Affiliations

    • Biomaterials and Oral Biochemistry Department, School of Dentistry, University of São Paulo, Av. Prof. Lineu Prestes, 2227, Sao Paulo, 05508-900, SP, Brazil

Received 13 October 2008; received in revised form 2 March 2009; accepted 23 March 2009.

Abstract 

Objectives

The aim of this study was to evaluate the influence of monomer content on fracture toughness (KIc) before and after ethanol solution storage, flexural properties and degree of conversion (DC) of bisphenol A glycidyl methacrylate (Bis-GMA) co-polymers.

Methods

Five formulations were tested, containing Bis-GMA (B) combined with TEGDMA (T), UDMA (U) or Bis-EMA (E), as follows (in mol%): 30B:70T; 30B:35T:35U; 30B:70U; 30B:35T:35E; 30B:70E. Bimodal filler was introduced at 80wt%. Single-edge notched beams for fracture toughness (FT, 25mm×5mm×2.5mm, a/w=0.5, n=20) and 10mm×2mm×1mm beams for flexural strength (FS) and modulus (FM) determination (10mm×2mm×1mm, n=10) were built and then stored in distilled water for 24h at 37°C. All FS/FM beams and half of the FT specimens were immediately submitted to three-point bending test. The remaining FT specimens were stored in a 75%ethanol/25%water (v/v) solution for 3 months prior to testing. DC was determined with FT-Raman spectroscopy in fragments of both FT and FS/FM specimens at 24h. Data were submitted to one-way ANOVA/Tukey test (α=5%).

Results

The 30B:70T composite presented the highest KIc value (in MPam1/2) at 24h (1.3±0.4), statistically similar to 30B:35T:35U and 30B:70U, while 30B:70E presented the lowest value (0.5±0.1). After ethanol storage, reductions in KIc ranged from 33 to 72%. The 30B:70E material presented the lowest reduction in FT and 30B:70U, the highest. DC was similar among groups (69–73%), except for 30B:70U (52±4%, p<0.001). 30B:70U and 30B:35T:35U presented the highest FS (125±21 and 122±14MPa, respectively), statistically different from 30B:70T or 30B:70E (92±20 and 94±16MPa, respectively). Composites containing UDMA or Bis-EMA associated with Bis-GMA presented similar FM, statistically lower than 30B:35T:35U.

Significance

Composites formulated with Bis-GMA:TEGDMA:UDMA presented the best compromise between conversion and mechanical properties.

Keywords: Composites, Conversion, Mechanical properties, Dimethacrylates, Organic solvents

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PII: S0109-5641(09)00162-6

doi:10.1016/j.dental.2009.03.010

Dental Materials
Volume 25, Issue 9 , Pages 1136-1141, September 2009

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