JOURNAL OF PROSTHETIC DENTISTRY THE

Vol. 99 No. 5      May - 2008

ISSN: 0022-3913      UBIC: 171

RESUMEN

Statement of problem: To prevent tooth weakening or pulp irritation, there is a need for a minimally invasive method of preparing single anterior crowns. Restoration dimensions for reduced coping thicknesses or less invasive finish line preparations are required. Purpose: The purposed of this in vitro was to study investigate the fracture performance of high-strength zirconia copings, compare knife-edge margins with chamfer finish lines, and examine the effect of reducing the layer thickness from 0.5 mm to 0.3 mm. Material and methods: Y-TZP zirconia copings were manufactured on brass dies of a maxillary central incisor. Forty copings, with 2 layer thicknesses (0.5 and 0.3 mm), and 2 finish line preparations (knife edge and chamfer; n=10) were cemented using a conventional glass ionomer cement and stored in distilled water at 37°C for 24 hours. The copings were vertically loaded until fracture using a universal testing machine. Data were analyzed by 2-way ANOVA (α=.05). Fractographic examination was performed using scanning electron microscopy and confocal laser scanning microscopy. Results: A significantly higher mean failure load was measured for knife-edge (0.5 mm, 1110 ±1 75 N; 0.3 mm, 730 ±160 N) versus chamfer (0.5 mm, 697 ±126 N; 0.3 mm, 455 ±79 N) preparations (P<.001), and for 0.5-mm versus 0.3-mm thickness layers (P<.001). Conclusions: Knife-edge preparations present a promising alternative to chamfer finish lines; the fracture load required for knife-edge preparations was 38% greater than that required for chamfer preparations, regardless of coping thickness. Reducing the thickness of a single crown coping from 0.5 to 0.3 mm resulted in a 35% reduction in fracture load required for either preparation type.(J Prosthet Dent 2008;99:369-376)

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