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

Abstract

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.

Cavity design and marginal degradation of the occlusal part of class-II amalgam restorations

“…It is acknowledged that this conclusion is only valid for the occlusal surface, since it is well established that unsupported enamel along the cavosurface angle on the proximal surface shows microcracking after use of the amalgam matrix (24,25). Although previous investigators suggest that the amalgam margin angle (AMA) influences the margin degradation more than the cavosurface angle (CSA), their studies show that enamel along the cavosurface angles seldom fractures (13,15,17,26). The origin of the high occlusal cavosurface angle is attributed to the original cavity designs of Black (27).…”

“…However, few clinical studies have been conducted in which the long-term performance of amalgam restorations has been correlated to the design or quality of the prepared cavities (1). These studies have focused on selective features of the cavity design, such as the width of the cavity (2-9), proximal retention grooves (10, l l ) , or the angle or quality of the cavosurface angles (12)(13)(14)(15)(16)(17). The aim of this study was to assess whether and how variations in the occlusal parts of the prepared cavities could influence the marginal degradation of the amalgam restorations.…”