Creep and Viscoelastic Behaviour of Human Dentin

Statement of Problem: Biomechanics of the human dentition is inherently complex. The aim of this study is to investigate, in vitro, the creep and the recovery of dentin under static uniaxial compressive stress conditions. Specimens of cylindrical morphology were prepared from recently extracted non-carious lower molar teeth, such that the average tubule orientation was axial. Slides of mid- coronal dentin (parallel surfaces, height 1.8 mm) were sectioned with a slow speed diamond saw and then cut into cylindrical discs. Specimens were stored at 4ºC for 24h to restabilize water content. Creep data were then measured by LVDT axially in water for periods of 2h load + 2h recovery on 4 separate groups (n=6): at two stresses (10 & 18 MPa) and at two temperatures: 37 & 60ºC. Maximum creep strain, permanent set, strain recovery and initial compressive modulus were reported. Compliance values were also calculated and slight non-linearity found at 60ºC. Two-way ANOVA was performed on results. Dentin exhibited a linear viscoelastic response under ''clinical'' compressive stress levels, with a maximum strain ~ 1% and high recoverability: permanent set<0.3%. This established a performance standard for viscoelastic stability of restorative biomaterials, replacing human dentin.