Dental Materials
Volume 23, Issue 3 , Pages 272-278, March 2007

3D-marginal adaptation versus setting shrinkage in light-cured microhybrid resin composites

  • Afrodite Kakaboura

      Affiliations

    • University of Athens, School of Dentistry, Greece
    • ,
  • Christos Rahiotis

      Affiliations

    • University of Athens, School of Dentistry, Greece
    • ,
  • David Watts

      Affiliations

    • University of Manchester, School of Dentistry, UK
    • ,
  • Nick Silikas

      Affiliations

    • University of Manchester, School of Dentistry, UK
    • ,
  • George Eliades

      Affiliations

    • University of Athens, School of Dentistry, Greece
    • Corresponding Author InformationCorresponding author at: Department of Biomaterials, University of Athens, School of Dentistry, 2 Thivon Str (Goudi), 115 27 Athens, Greece. Tel.: +30 210 7461100 2; fax: +30 210 7461306.

Received 22 December 2005; accepted 24 January 2006.

Abstract 

Purpose

To comparatively evaluate the 3D-marginal adaptation to dentine versus shrinkage strain of two light-cured microhybrid resin composites.

Methods

Dentine cavities (Ø: 2mm; h: 1mm; n=2×4) were prepared, filled with a single layer of EsthetX and Premise resin composites, respectively, without any adhesive cavity pre-treatment, and light-cured for 40s at 750mW/cm2. All the specimens were imaged by computerized X-ray microtomography. Sequential sections (n=11) at 8.09pixel size were taken at top, middle and bottom sites of each restoration relative to the axial wall and the interfacial micro-void volume fraction (%VF) was calculated. Shrinkage strain (%S) and strain rate (%SR) of the composites were measured by the bonded-disc method (n=4). The results of %VF per material and restoration site were subjected to statistical analysis by 2-way ANOVA and Tukey's test, whereas the results of %S and %SR were analysed by t-test (p=0.05). Regression analysis was performed to determine correlations between %PF and %S, %SR.

Results

The results of %VF at top (t), middle (m) and bottom (b) restoration sites were (%, mean±S.D.): EsthetX 0.84±0.11 (t), 0.80±0.32 (m), 6.74±5.12 (b), Premise 0.99±0.24 (t), 0.92±0.38 (m), 1.72±0.97 (b). The results of %S were (%, mean±S.D.): EsthetX 2.60±0.29, Premise 1.91±0.10 and of %SR were (%, mean±S.D.): EsthetX 1.47±0.04, Premise 1.18±0.02. %VF(b) of EsthetX showed the highest values within and between the testing groups (p<0.05). %S and %SR values of EsthetX were significantly higher from Premise (p<0.05). Strong positive correlations were documented between %VF(b)-%S (r=0.843) and %VF(b)-%SR (r=0.943).

Clinical significance

The results confirmed a positive correlation between setting shrinkage and interfacial gap volume at bottom sites of light-cured microhybrid composite restoration due to differential shrinkage. Shrinkage strain rate seems to be a more sensitive factor in determining percentage volume of interfacial porosity at bottom restoration sites.

Keywords: Shrinkage strain, Resin composites, X-ray microtomography, Polymerisation

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PII: S0109-5641(06)00031-5

doi:10.1016/j.dental.2006.01.020

Dental Materials
Volume 23, Issue 3 , Pages 272-278, March 2007

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