Comparison of resistance features for complex amalgam restorations.

This study evaluated the resistance provided to complex Dispersalloy amalgam restorations by pins (Group 1), amalgapins (Group 2), and a peripheral shelf or shoulder (Group 3) or in combinations of pins plus peripheral shelf (Group 4), or amalgapins plus peripheral shelf (Group 5). The occlusal surfaces of 50 extracted maxillary molar teeth were ground to a flat surface 2 mm occlusal to the CEJ, and the roots were matched and embedded in acrylic resin 2 mm apical to the CEJ. The greatest faciolingual and mesiodistal dimensions of each tooth at the level of preparation were recorded and these two measurements were multiplied to give a product for each specimen. The teeth were then sorted by tooth sizes and equally distributed among the five groups. Each group of flattened teeth received a different resistance form configuration. Amalgam was condensed using a matrix; the bands and excess amalgam were removed 24 hours later and each amalgam "occlusal" surface was ground flat to standardize the restoration at a 4 mm occlusal height. A 1 mm 45 degrees bevel was prepared on the facio-occlusal angle of the amalgam, and each specimen was loaded in compression at 45 degrees in an Instron at a crosshead speed of 1 mm/min. The groups and their mean (SD) failure loads in Newtons were: Group 1: 1515 (274); Group 2: 1521 (244); Group 3: 578 (175); Group 4: 1199 (229); and Group 5: 1691 (298). A one-factor ANOVA and a Tukey B post-hoc analysis showed no differences between Groups 1, 2 and 5.(ABSTRACT TRUNCATED AT 250 WORDS)