Viscoelastic stability of pre-cured resin-composite CAD/CAM structures

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Objectives: To study the effect of water storage (3 months)on the creep deformation and recovery of CAD/CAM composite materials to determine their viscoelastic stability. Materials and methods: Five CAD/CAM composite blocks, with increasing filler loading, and one polymer-infiltrated ceramic network (PICN)were studied. Six specimens of each material were separated into two groups (n=3)according to their storage conditions (24 h dry storage at 23°C versus 3 months storage in 37°C distilled water). A constant static compressive stress of 20 MPa was applied on each specimen via a loading pin for 2 h followed by unloading and monitoring strain recovery for a further period of 2 h. The maximum creep-strain (%)and permanent set (%)were recorded. Data were analysed via two-way ANOVA followed by one-way ANOVA and Bonferroni post hoc tests (<0.05)for comparisons between the materials. Homogeneity of variance was calculated via Levene's statistics. Results: The maximum creep strain after 24 h dry ranged from 0.45% to 1.09% and increased after 3-month storage in distilled water to between 0.71% and 1.85%. The permanent set after 24 h dry storage ranged from 0.033% to 0.15% and increased after 3-month water storage to between 0.087% and 0.18%. The maximum creep strain also reduced with increasing filler loading. Significance: The PICN material exhibited superior dimensional stability to all of the pre-cured resin composite blocks in both storage conditions with deformation being predominantly elastic rather than viscoelastic. Notwithstanding, two of the resin-matrix composite blocks approached the PICN performance, when dry, but less so after water storage.

Original languageEnglish
JournalDental Materials
Early online date27 May 2019
Publication statusPublished - 2019


  • CAD/CAM composite blocks
  • Creep
  • Polymer-infiltrated ceramic network
  • Viscoelastic stability


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