Fracture resistance of extensive amalgam restorations retained by pins, amalgapins and amalgam bonding agents

This in-vitro study compared the resistance of extensive amalgam restorations retained by either four Regular TMS Link Plus pins, four amalgapins, Amalgambond Plus, Amalgambond Plus with HPA, Scotchbond Multi-Purpose Plus, PQ Amalgam, Panavia F 2.0, All-Bond 2 or Resinomer. Ninety caries-free third molars were embedded in acrylic resin and their occlusal surfaces reduced to within 2 mm of their CEJ. Tytin amalgam alloy was hand-condensed into copper band matrices reinforced with modeling compound after placement of mechanical retention or application of the amalgam bonding agents. Modeling compound and copper bands were removed after 24 hours, and the restorations were adjusted to produce specimens 5 mm in height with a 1 mm bevel on the occlusal-axial surface. The specimens were stored in 100% humidity for one month followed by immersion in de-ionized water for 24 hours at 37 degrees C. The specimens were loaded in compression at a 45 degrees angle in an Instron Universal Testing Machine at a crosshead speed of 0.02 inches/minute. The mean failure loads and standard deviations recorded in Newtons were as follows: Amalgambond Plus with HPA 2160N (380), Scotchbond Multi-Purpose Plus 1900N (380), four Amalgapins 1770N (340), PQAmalgam 1660N (270), Panavia F 2.0 1620N (440), Amalgambond Plus 1570N (390), four Regular TMS Link Plus Pins 1325N (406), All-Bond 2 1300N (390) and Resinomer 1245N (310). A one-way ANOVA and Tukey post hoc analysis indicated all amalgam bonding agents were statistically equal to either four Regular TMS Link Plus pins orfour amalgapins.