ABSTRACT
OBJECTIVE: An analysis is made of the influence of continuous compression loading on different types of cast posts and cores and its effects on the crowns and teeth. METHOD AND MATERIALS: Thirty extracted maxillary canines were prepared and divided into three groups (n = 10) according to the type of cast posts and cores used for restoration: chrome-nickel alloy, acetalic resin, and IPS-Empress porcelain. Metallic cast crowns were luted onto the cores. The specimens were evaluated with an Instron testing machine at an angulation of 45 degrees and a forward speed of 0.5 mm/min. After testing, the specimens were sectioned along the axis and examined under x40 magnification. RESULTS: Mean load resistance of the restorations until fracture was 2,120 N, 1,491 N, and 2,139 N in the chrome-nickel, IPS-Empress ceramic, and acetalic resin groups, respectively. CONCLUSION: Significant differences in resistance were observed between metal and porcelain and between resin and porcelain. Microscopically, the apical portion was found to be most affected by fracture and compromised the teeth subjected to chrome-nickel restorations. The metal cast posts and cores exhibited different angulations, while the ceramic restorations showed cracks. The acetalic resin cast posts and cores presented no fractures.
Subject(s)
Post and Core Technique , Acetals , Aluminum Silicates , Chromium Alloys , Compressive Strength , Crowns , Cuspid , Dental Porcelain , Dental Stress Analysis , Elasticity , Humans , Materials Testing , Polymers , Resins, Synthetic , Statistics, Nonparametric , Tooth Fractures/prevention & control , Weight-BearingABSTRACT
Se presenta un estudio experimental in vitro en el que se compara la retención que ofrecen los retenedores circunferenciales tipo Ackers de resina acetálica con los de cromo-cobalto. Se realizan para ello 6 coronas de cromo-níquel, 3 con forma de canino superior y 3 con forma de primer premolar superior y cada una de ellas con un grado diferente de retención (0.25, 0.50 y 0.75 mm). Sobre cada una de ellas se confecciona un retenedor de resina acetálica y uno de cromo-cobalto, siendo testados por una máquina Instron. Los resultados confirman que los retenedores de cromo-cobalto son más retentivos, y que los acetálicos ofrecen una retención suficiente para cumplir su cometido (AU)
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