CUSP FRACTURE OF ENDODONTICALLY TREATED POSTERIOR TEETH RESTORED WITHAMALGAM - TEETH RESTORED IN DENMARK BEFORE 1975 VERSUS AFTER 1979

The aim of the present study was to analyze the frequency and the seve rity of cuspal fracture for posterior teeth endodontically treated by 91 Danish dentists and restored with amalgam either before 1975 or aft er 1979. A database from a previous study was analyzed (1584 teeth wit h an MO, a DO, or an MOD amalgam restoration without cuspal overlays). Teeth restored before 1975 had a significantly lower frequency of cus p fracture than teeth restored after 1979. Moreover, when comparing th e frequency of subcrestal fractures, that of the second group (after 1 979) was more than twice as high as that of the first group (before 19 75). Two factors with a bearing on these findings changed in the time period 1975-1979: the high-copper amalgams took over in Denmark, and t he use of Gates-Glidden burs to achieve straight-line access to the ro ot canal was introduced. It is suggested that the weakening of the cor onal part of the root, caused by the use of Gates-Glidden burs, and th e expansion and low creep of high-copper amalgams may be two of the re asons for the increased frequency and severity of cuspal fracture foun d in the past decade in Denmark.