Studies on the tensile properties of spherical amalgam.

Ever since the adoption by American Dental Association in 1929 of test specification of dental amalgam alloys as A. D. A. specification No. 1 [ 1 ], many studies have been successively carried out on the physical, chemical, mechanical and clinical properties as manipulative variable affecting clinical results of this widely used restorative material. Amalgam has come to account for nearly 75% usage among various restorative materials by the dental clinicians of today [2], attesting to its importance and ease in handling. Despite this wide usage, however, many reports are published on the failure cases of amalgam restorations by such investigators as HEALEY and PHILLIPS [3], SEINO [4], FUSAYAMA et al. [5], SAIJO [6], HABU et al. [7], and WILSON and RYGE [8]. Although it is generally accepted that most of the failures are attributed to inadequate cavity preparation and unsatisfactory amalgam manipulation, it was pointed out by NAGAI et al. [ 9 ] that the failure should be also sought in the innate characteristics of dental amalgam itself.