Effect of setting time and artificial saliva on the strength evaluated by different methods of dental silver amalgam: A comparative study

Abstract

AbstractThe aim of this study is to evaluate the effect of setting time and artificial saliva on the strength of dental amalgam by diametral compressive strength, Hertzian failure loading testing and compressive strength test methods. Nine dental amalgam products are evaluated using three strength measurements, compressive, diametral, and Hertzian loading testing at early (1 h or 2 h), 24 h and 30 days after setting at 37 °C. The trituted amalgams are used to prepare Hertzian, tapered disc by manual condensation according to the ISO standard procedure (ISO 17988: 2014). The compressive and diametral testing specimens are obtained using the mechanical condensation by two apparatus with different specimen dimensions of height and diameter, 8.0 mm×4.0 mm and 2.0 mm×8.0 mm, respectively. The apparatus and schedule specification for preparing compressive testing specimens are according to ISO 24234: 2015 while dimensions of some parts of diametral testing apparatus were modified and the schedule was optimized to provide sound disc test‐pieces by a one‐shot procedure. The diametral and Hertzian testing specimens are also evaluated after 30 days under dry storage conditions and after aging in the artificial saliva. The artificial saliva was prepared according to ISO17988: 2014 standard specifications. The single diametral or “triple‐cleft” fracture path, and radial cracking are observed in all products for diametral and Hertzian testing methods, respectively. The discriminatory power in early strength tests is in order to Hertzian < diametral < compressive. A significant correlation between diametral and compressive strength value is observed at early setting time. It is found a correlation between diametral and Hertzian strength mean value and variance ratio in immersion test.