Abstract:

Objective To study the influence of different cements and margin designs on marginal microleakage in metal crowns in order to guide clinical design, operation, and to provide basis for  reducing microleakage in clinic.
Methods  45 extracted human teeth were randomly divided into 3 groups. Teeth were prepared to the different margin finish lines, respectively chamfer, shoulder and bevel, and cast metal crowns. The crowns in each group were randomly subdivided into 3 subgroups according to the cements:Rely X Unicem resin adhesive, 3M resin modified glass ionomer cement, and polycarboxylate cement. After thermocycling experiment,the teeth were dyed and developed,and the crowns were cut along the long axis of the teeth, then all specimens were evaluated under the microscope, and were graded using SPSS 17.0 software for statistical analysis on the degree of microleakage. Results With the same finish line, the resin adhesive demonstrated the least marginal microleakage,and polycarboxylate cement was associated with severe marginal microleakage(P<0.05);With the same cement, chamfer and bevel had no significant difference in microleakage(P>0.05),and they were both less than shoulder(P<0.05). Conclusion Resin adhesive luting system which is the first selection in clinic is better th
an glass ionomer cement and polycarboxylate cement;the chamfer and bevel which are the appropriate finish lines for decreasing microleakage are better than shoulder.

Key words: microleakage;finish line;cemen