Comparison of Marginal Gap in Three Different Finish Lines.

Marginal fit of restorations is important for longevity and periodontal health maintenance.The purpose of this study was to compare the marginal fit adaptation of metal ceramic crowns in three different finish lines, fabricated with base metal alloys. 33 metalic dies were prepared in three groups of finish line: Shoulder 1350, Shoulder and Chisel. Dies were lubricated and wax patherns formed with use of a wax bath. Wax specimens were invested and cast with base metal alloy. After placement of porcelain on surface of castings, all crowns were luted with cement under a constant load. All specimens were then embedded in acrylic resin block and sectioned. The marginal fit of the corwns were evaluated by measuring film thickness of cement in the margins. The differences between groups were evaluated with ANOVA and LSD test. Statistical difference between Shoulder and the other groups was significant (P<0.001). By considering discussed advanages of 1350 Shoulder finish line for metal-ceramic restorations, this finish line is recommended for metal ceramic restorations made from base metal alloys.