Evaluation of mechanical properties and marginal fit of dental ceramic materials fabricated by robocasting
Al-Bahrami, Hadi Ali
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Objectives: To determine the flexural strength, fracture toughness, load to failure and marginal fit of dental ceramic materials fabricated by robocasting in comparison to the analogous materials fabricated from pressed blocks used for conventional subtractive milling method. Materials and methods: The test groups for the flexural strength and the fracture toughness tests were composed of robocast feldspathic-porcelain using Vita Mark II powder (Vident, Brea, CA), robocast glass-infused alumina using Vita In-Ceram powder (Vident, Brea, CA), robocast glass-infused alumina using A-15 powder (Almatis, Leetsdale, PA) and robocast-spray-deposited A-15 alumina. The control groups were Vitablocs Mark II blocks (VITA Zahnfabrik, Bad Sackingen, Germany) and Vita In-Ceram Alumina blocks (VITA Zahnfabrik, Germany). The feldspathic porcelain and the glass-infused alumina groups were compared separately. The materials were cut to form bars that are 2 × 4 × 22 mm in dimension. A 3-point-bending test was used to measure the flexural strength of materials with an Instron machine at a crosshead speed of 0.5 mm/min with a lkN load cell. Fracture toughness of the same materials was obtained using Single Edge Notch Beam method (SENB) method. The test groups for the load to failure and marginal fit of copings composed of robocast-spray-deposited A-15 alumina powder, while the control groups consisted of milled Vita In-Ceram alumina. Load to failure was tested by cementing the copings to aluminum dies and placing the copings under an axial load on an Instron machine with a cross-head speed of 0.5 mm/min and a 10 kN load cell. Similar copings embedded in clear epoxy resin resin (Buehler TEM Epoxy Resin; Buehler Ltd) and sectioned longitudinally at the middle. The marginal gaps between the copings and the aluminum dies were viewed with a metallurgical microscope (Axiocron inspection microscope; Carl Zeiss, West Germany). Results: Student t-test demonstrated significant difference in flexural strength between the robocast feldspathic porcelain and the Vitablocs Mark II (P[less than]0.05), but there was no difference between the two groups in their fracture toughness values (P[more than]0.05). Analysis of variance demonstrated significant difference between the glass-infused alumina groups for both the flexural strength and the fracture toughness tests (P[less than]0.05). Tukey’s post hoc multiple comparison tests demonstrated that both In-Ceram alumina groups were significantly higher in the strength and toughness values than the two A-15 Almatis groups (P[less than]0.05), and no differences were found within the In-Ceram or the Almatis groups. Student t-tests showed that mean failure load of the robocast alumina copings was significantly lower than the milled copings (P[less than]0.05). No significant differences were found between mean marginal gaps for the robocast and the milled alumina copings (P[more than]0.05). Conclusions: The robocast feldspathic porcelain was weaker in flexural strength than the Vitablocs Mark II, but both were similar in their fracture toughness values. Robocast In-Ceram and In-Ceram blocks had significantly higher fracture toughness and flexural strength than the Almatis groups. The robocast-spray-deposited glass-infused A-15 Almatis alumina copings were less resistance to fracture than the milled In-Ceram Alumina copings. The robocast and the milled alumina copings did not differ from each other in the marginal gaps evaluations.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact firstname.lastname@example.org.Thesis (MSD)--Boston University, Goldman School of Dental Medicine, 2009 (Department of Restorative Sciences and Biomaterials).Includes bibliographical references (leaves 80-86).
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