The amalgam margin angle, marginal breakdown and adjacent caries in occlusal enamel, a pilot study on extracted teeth

The object of this study was to determine for amalgam restorations the relationship between marginal breakdown and (i) over- or undercarving; (ii) the amalgam margin angle (AMA); and (iii) the incidence of carious occlusal enamel adjacent to the restoration. Fifty-two extracted human teeth with occlusal amalgam fillings from the Chicago (C) area and forty-three teeth from the Jerusalem (J) area, were examined with a probe. Employing common clinical criteria, it was found that replacement of the fillings was indicated due to extensive marginal defects, in 45% of the C teeth, and 41% of the J teeth. The occlusal amalgam margins and the incidence of caries adjacent to these margins were studied on facio-lingual sections. The incidence and the average AMA values for six margin types were measured on random sections and were found to be: all margins (100%, 67 degrees); intact flush margins (31%, 69 degrees); fractured flush margins (21%, 56 degrees); undercarved margins which fractured (22%, 74 degrees), or did not fracture (9%, 80 degrees) near the cavity margin; margins with amalgam deficiencies (12%, 62 degrees); and margins with separation between enamel and amalgam by remnants of linings (5%). Marginal breakdown was found in 42% of the margins and was associated mainly with flush carving at low AMAs, and with broken flashes resulting from undercarving. Occlusal carious enamel was detected on 19% of the J teeth and none of the C teeth. Sixty-three per cent of these lesions were associated with fractured undercarved margins.