RESUMO
PURPOSE: Investigate and compare fracture resistance of four commercially available esthetic crowns. METHODS: Sixty-four anterior crowns were used: NuSmile Primary crowns (NuSmile, Houston, Tex. USA) (16); Preveneered Cheng Crowns, (Orthodontic Technologies Inc., Houston, TX) (16); NuSmile ZR (NuSmile, Houston, Tex. USA); and Cheng Crowns zirconia (Orthodontic Technologies Inc., Houston, TX). Crowns were mounted and cemented on a negative replica and placed under servo hydraulic mechanical universal testing machine. Force was applied at 90° with crosshead speed of 1 mm/min until they fractured. Maximum breaking loads were recorded. Data was then analyzed using software that measured the fracture resistance of the crowns. One-way Analysis of Variance (ANOVA) was used to find the differences between the groups and Scheffe post hoc test was used for intergroup comparisons. The level of significance was set as p ≤ 0.05. RESULTS: Mean maximum loads were as follows: NuSmile ZR crowns (937.36 + 131.68 N), Cheng Zirconia Crowns (751.43 + 102.103 N), NuSmile Primary crowns (482.37 + 76.92), and Preveneered Cheng Crowns (415.57 + 12.28). Zirconia crowns the had highest fracture resistance compared to preveneered crowns (p < 0.05). No significant difference between NuSmile ZR Zirconia and Cheng Crowns zirconia nor between NuSmile primary Preveenered and Preveneered Cheng Crowns. CONCLUSION: Zirconia crowns showed the highest fracture resistance with NuSmile zirconia crowns to being able to resist fracture even under intense pressure of load compared to Cheng Crowns zirconia.
