This study observed alteration in the radiopacity and microhardness of expired resin-based materials compared to non-expired materials and the operating characteristics of the X-ray source used. Five 2 mm-thick cured specimens were prepared for each material: composite resins (P60®, Z100®), and a compomer (Dyract AP®). Radiopacity of the specimens was evaluated comparing the density of the resin-based material to an equivalent (mm) density of a 99.5% pure aluminum step wedge using a transmission densitometer. Surface microhardness measurements were carried out using a calibrated Vickers indenter on three different points of the same surface. ANOVA and Tukey tests (pre-set alpha = 0.05) revealed that expired materials showed no significant change in radiopacity. One material (Filtek P60) demonstrated lower radiopacity with lower KVp. Change in microhardness wa s statistically significant for Z100: for this material, the microhardness after expiration was significantly lower than before the expiration date
A utilização de novos materiais, especialmente aqueles metálicos, tem sido uma constante na odontologia. Graças às necessidades da indústria no desenvolvimento de produtos cada vez com maior resistência, principalmente à corrosão, a prótese tem-se beneficiado com um número elevado de ligas metálicas excelentes. Para atender a necessidade de conformar as ligas em restaurações ou aparelhos próprios à nossa profissão, devem ser desenvolvidos refratários para estas ligas. Este é o caso da proposta de usar uma lama refratária como molde para confecção da fundição. A lama proposta, além de servir aos propósitos, tem-se mostrado capaz de oferecer melhor acabamento da liga.
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