Experimental design in the clinical evaluation of amalgam restorations

Abstract

In a clinical evaluation of marginal deterioration, 475 amalgram restorations were equally distributed in a 6 X 4 X 2 X 3 factorial design, based on alloy, operator, tooth, and number of restored surfaces. All factors except the last had a statistically significant effect after 6, 12, and 18 months. There were no consistent two-way interactions over time.

Clinical variables affecting the marginal degradation of amalgam restorations

“…To our knowlsizes in the mandibular premolars compared edge there are no previous reports in which The clinical performance of the different alloys is in accordance with previous reports in that the marginal degradation was less for the non-gamma-2 alloys than for the conventional lathe-cut alloys (1)(2)(3)(4)(5)(6)(7)(8)20). It has been suggested that a superior material would perform better for all dentists ( 4,6). This hypothesis was strengthened by the present findings.…”

“…The obdegradation specifically in the first molars servation that DO restorations showed less than in the other teeth partially supports marginal degradation than MO or MOD resprevious observations (15) but contrasts with torations is difficult to explain. Some of the the conclusions by other authors (6,7,19). differences may be the result of a greater The quality of the occlusal cavity margins frequency of DO restorations in the mandid not differ in the various tooth categories dibular premolars than in the other teeth.…”

“…The correlation between the type of tooth and marginal degradation indicates that the mandibular premolars generally show less breakdown than the other teeth and that the molars show more breakdown than the pre- molars (6,15,19) . .…”

“…Clinical factors that may influence the marginal degradation of amalgam restorations, besides alloy and operator, are the effects of the patient (6,8,(12)(13)(14) or, more specifically, the location or type of tooth ( 6,7,(15)(16)(17)(18)(19), the type of restoration (6,19), and the morphology of the cavity (20). The correlation between the type of tooth and marginal degradation indicates that the mandibular premolars generally show less breakdown than the other teeth and that the molars show more breakdown than the pre- molars (6,15,19) .…”

“…Longitudinal clinical trials have demonstrated that the extent of marginal degradation of amalgam restorations is operatordependent (1)(2)(3)(4)(5)(6)(7)(8)(9). The mechanism of this dependence is not established, but it has been suggested that the handling properties of the alloy and the condensation techniques of the operators.…”