Cervical marginal fit of proximal amalgam restorations

This study investigated the relationship between the adaptation, apical location and gap width of the cervical margin of proximal amalgam restorations. Three hundred and seventeen proximal cervical margins were studied in 243 extracted teeth. The restorations were categorized as 'flush fitting'; 'small overhang', or 'large overhang', based on examination with a Cross calculus probe. After trimming the overhangs to make the restorations flush with the tooth surface, the gap width was measured. In addition, the location of the cavity margin was measured relative to the amelocemental junction (ACJ), and the data were further grouped according to whether the restoration finished apical to the ACJ, less than 1.5 mm coronal to it, or more than 1.5 mm coronal to it. All measurements were made with a Reflex Microscope. Analysis of variance with the Scheffé multiple range test indicated that: the mean gap width of large overhanging restorations was significantly greater than that of small overhanging or flush fitting restorations (P < 0.001); the mean gap width of restorations which finished on the root surface was significantly greater than that of those restorations which finished on the enamel surface at more than 1.5 mm from the ACJ (P < 0.002); and large overhanging restorations were located further apically than small overhanging restorations which were, in turn, located further apically than flush fitting restorations (P < 0.0001). Furthermore, discriminant analysis indicated that the location of the cervical margin had more influence on gap width than the presence of an overhang (R2 = 3.6%; P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)