Effect of Surface Treatments on Fracture Strength of Zirconia Core


Background The increasing of demand for all-ceramic restorations has led to the development of ceramic materials with optimized mechanical properties, such as densely sintered aluminum oxide and zirconium oxide (zirconia) ceramics. Objectives The purpose of this in vitro study was to evaluate the effect of etching with hydrofluoric acid or phosphoric acid and the effect of packable P60 composite veneer material on fracture strength of zirconia cores. Materials and Methods Twenty-four zirconium cores (Vita, Germany) with 0.7mm thickness were fabricated by CAD-CAM technology and sintered at 1450 ⁰C for 60min according to the manufacturer’s instructions. All zirconium cores were subjected to air abrasion with 50μm of Al2O3. These were randomly divided into three groups, (n=8). Group A: control group, veneered with IPS E-max Ceram porcelain; group B: etching with 37% of phosphoric acid and veneered with packable composite resin; and group C: etching with 9.5% of hydrofluoric acid and veneered with packable composite resin. All specimens were subjected to fracture strength test in an universal testing machine, a load was applied with 6mm diameter steel ball indenter at a crosshead speed of 0.5mm/min. Results One-way ANOVA test showed that there were statistically highly significant differences among all studiedgroups. LSD testwas performed to show thesource of significancy it showed a highly significant difference among all testedgroups. Conclusion A combination of surface treatment of 50μm Al2O3 and 37% concentration of phosphoric acid and adhesive agent could enhance the fracture strength of composite veneered crowns.