• Deformation of a dental ceramic following adhesive cementation.

      Isgró, G; Addison, O; Fleming, G J P; Materials Science Unit, Division of Oral Biosciences, Dublin Dental School & Hospital, Trinity College Dublin, Lincoln Place, Dublin 2, Ireland. giuseppe.isgro@dental.tcd.ie (2010-01)
      Stress-induced changes imparted in a 'dentin-bonded-crown' material during sintering, annealing, pre-cementation surface modification, and resin coating have been visualized by profilometry. The hypothesis tested was that operative techniques modify the stressing pattern throughout the material thickness. We polished the upper surfaces of 10 ceramic discs to remove surface imperfections before using a contact profilometer (40-nm resolution) to measure the 'flatness'. Discs were re-profiled after annealing and after alumina particle air-abrasion and resin-coating of the 'fit' surface. Polished surfaces were convex, with a mean deflection of 8.4 + or - 1.5 microm. Mean deflection was significantly reduced (P = 0.029) following alumina particle air-abrasion and increased (P < 0.001) on resin-coating. Polishing induced a tensile stress state, resulting in surface convexity. Alumina particle air-abrasion reduced the relative tensile stress state of the contralateral polished surface. Resin-polymerization generated compression within the resin-ceramic 'hybrid layer' and tension in the polished surface and is likely to contribute to the strengthening of ceramics by resin-based cements.
    • Seating load parameters impact on dental ceramic reinforcement conferred by cementation with resin-cements.

      Addison, Owen; Sodhi, Amandeep; Fleming, Garry J P; Biomaterials Unit, University of Birmingham School of Dentistry, St. Chad's Queensway, Birmingham B4 6NN, UK. addisono@adf.bham.ac.uk (2010-09)
      The magnitude of resin-reinforcement conferred was sensitive to the loading parameters investigated although the mechanisms underlying the variation appear complex. Similar patterns of variability can be expected clinically impacting on the clinical longevity of resin-cemented glass-ceramic restorations.