Surface Strain on Ce-TZP/Al2O3 Nanocomposite and Y-TZP Framework

Objectives: Clinical application of zirconium oxide framework has expanded the range of indication of all ceramic bridges in posterior region. On the other hand, distortion of ceramic bridge framework could be one of the main reasons for fracture of the layering porcelain. The aim of this study was to evaluate the difference of the surface mechanical stress between zirconium oxide and metal frameworks. Material and methods: As a master die, we used a clinical patient's working cast whose upper left second premolar and first molar were missing. Composite resin abutment teeth with roots were duplicated from the master die. Each tooth root was reproduced based on anatomical tooth form. The root of each specimen was embedded in acrylic resin with a layer of silicone as an artificial periodontal ligament. Similar-shaped four unit bridge frameworks were fabricated from Ce-TZP/Al2O3 Nanocomposite, Y-TZP and two kinds of gold-platinum alloys for porcelain veneering (DeguDent Universal and Bio Fine Bond). Five rosette strain gauges were attached to the marginal portion of the framework. Each framework was cemented to the abutment teeth with zinc phosphate cement. Result: When the centre of the pontic was loaded with 100N, the tensile strain values on the pontic side marginal surfaces of the second premolar and the second molar of the DeguDent Universal framework were 82 to 92ìå and 37 to 94ìå respectively. Those of the Bio Fine Bond framework were 28 to 205ìå and 35 to 51ìå respectively. Those of the Y-TZP framework were 16 to 87ìå and 18 to 100ìå respectively. Those of the Ce-TZP/Al2O3 Nanocomposite framework were 19 to 20ìå and 36 to 37ìå respectively. Conclusion: The strain concentration of the Y-TZP framework was less than that of the metal frameworks and the surface strain of the Ce-TZP/Al2O3 Nanocomposite framework was the lowest.