Abstract
T he conservative concept of Class II amalgam restorations suggests that the resistance and retention forms of the cavity preparation should be independent of each other. The convergence of the buccal and lingual walls toward the occlusal surface provides sufficient retention against displacement of the occlusal and proximal portions of the restoration. However, to ensure retention in the proximal portion, regardless of the occlusal dovetail, additional retention must be provided to resist proximal displacement and increase the strength of the Class II amalgam restoration.‘~s Repeated compressive stress applied to the proximal portion may cause its displacement or fracture because of the narrow isthmus of the dovetail69 7 The concept suggested by Markley” recommends eliminating the occlusal portion in the absence of occlusal caries. This view was recently supported by Almquist et al.9 Many authors agree that additional proximal retention is a basic principle toward a more conservative Class II amalgam cavity preparation.10-‘4 They also agree that the dovetail is of paramount importance. There are three designs for retention at the axiobuccal and axiolingual line angles: (1) an angular area from the axiogingivobuccal and axiogingivolingual point angles to a narrow vertex just apical to the axiopulpal line angle,“‘, 12S2o (2) a cone-shaped vertical groove which diverges toward the occlusal surface; the greater diameter is located at the level of the occlusal dentinoenamel junction, while the minor diameter is located close to the axiogingivobuccal and axiogingivolingual point angles,6’ ‘3 21-24 and (3) a cylindrical groove made with a straight fissure bur for deciduous teeth.25-28
Published Version
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