Fracture resistance of implant-supported abutments with finish line versus BOPT

Objective: The purpose of this in vitro study is to evaluate the effect of four finish line configurations and two cement types on the fracture resistance of zirconia copings. Material and Methods: Forty yttrium tetragonal zirconia polycrystals copings were manufactured on epoxy resin dies with four preparation designs: knife edge, chamfer, deep chamfer 0.5, 1 mm and shoulder 1 mm. The copings were cemented with two cement types (glass ionomer and resin cement); (n = 5). Two strain gauges were attached on each coping before they were vertically loaded till fracture with a universal testing machine. Data were analyzed by 2-way analysis of variance ANOVA (p < .05). Fractured specimens were examined for mode of failure with digital microscope. Results: Knife edge showed the highest mean fracture resistance (987.04 ± 94.18) followed by Chamfer (883.28 ± 205.42) followed by Shoulder (828.64 ± 227.79) and finally Deep chamfer finish line (767.66 ± 207.09) with no statistically significant difference. Resin cemented copings had higher mean Fracture resistance (911.76 ± 167.95) than glass ionomer cemented copings (821.55 ± 224.24) with no statistically significant difference. Knife edge had the highest strain mean values on the buccal (374.04 ± 195.43) and lingual (235.80 ± 103.46) surface. Shoulder finish line showed the lowest mean strain values on the buccal (127.47 ± 40.32) and lingual (68.35 ± 80.68) with no statistically significant difference. Resin cemented copings had higher buccal (295.05 ± 167.92) and lingual (197.38 ± 99.85) mean strain values than glass ionomer copings (149.14 ± 60.94) and (90.27 ± 55.62) with no statistically significant difference. Conclusion: Vertical knife edge finish line is a promising alternative and either adhesive or conventional cementation can be used with zirconia copings. KEYWORDS Cementation; Flexural strength; Prosthodontics; Tooth preparation; Zirconium.

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Evaluation of fracture resistance of zirconia monolithic restorations: an in vitro study

Brazilian Dental Science ◽

10.14295/bds.2021.v24i2.2326 ◽

2021 ◽

Vol 24 (2) ◽

Author(s):

Ahmed Mohamed Arafa ◽

Ahmad El-Kouedi ◽

Tamer Hamza ◽

Hisham Katamish

Keyword(s):

Stainless Steel ◽

Fracture Resistance ◽

Artificial Aging ◽

Testing Machine ◽

Control Group ◽

Hydrothermal Conditions ◽

Finish Line ◽

M Phase ◽

Group A ◽

Group B

Objective: The aim of the study was to evaluate fracture resistance of zirconia monolithic restorations after ageing procedures. Material and methods: The fracture resistance of zirconia-based restoration after ageing procedures was evaluated. Monolithic translucent zirconia 3-unit FDPs were fabricated using Cerec inLab CAD/CAM system on 2 stainless steel dies prepared from stainless steel with a uniform 120 degrees circumferential deep chamfer finish line of 1 mm width and were placed into a stainless steel holder. FDPs were divided into 2 groups, the first group (Group A) was subjected to aging procedures in an autoclave at hydrothermal conditions 134 °C /2 bars for 5 hours. The second group (Group B) was not subjected to any ageing procedures and was designed as control group. All specimens of group A (Aged TZI) and group B (non- aged TZI) were loaded compressively in a universal testing machine at cross head speed 0.5 mm/min until fracture occurred. The percentage of monoclinic (m) phase was detected by XRD device. Scanning electron microscope (SEM) was used to examine the fractured surfaces for Aged TZI (Group A) and Non-aged TZI (Group B). Student’s t-test was used to compare between fracture resistances of both groups. The significance level was set at P ? 0.05. Results: The fracture resistance mean (SD) values of non-aged TZI (Group B) was 2406.9±306.8 N which showed statistically significantly higher than that of aged group (Group A) which was 1964.5±234.5 N. The percentage of monoclinic (m) phase detected by XRD device software in non-aged TZI (Group B) was nearly 0 weight % and in aged TZI (Group A) was about 42 weight %. Conclusion: Accelerated artificial aging decreases the fracture resistance of monolithic TZI FDPs. Keywords Artificial aging; Fracture resistance; Monolithic zirconia.

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