Effect of Sloped Shoulder and Deep Chamfer Finish Lines on Marginal Adaptation of Zirconia Restorations
Author(s): Ezzat Allah Jalalian, Shahbaz Naser Mostofi, Amir Ali Shirian, Farin Shamshirgar, Hadi Kaseb Ghane, Maryam Naseri
Marginal adaptation of full-coverage restorations is an important factor determining their long-term success. Preparation design and finish line can significantly affect marginal adaptation. This study aimed to assess the effect of deep chamfer and sloped shoulder finish lines on marginal adaptation of zirconia restorations. In this in vitro, experimental study, a standard die measuring 7 mm in length and 5 mm in diameter received sloped shoulder finish line with 1 mm depth at one side and deep chamfer finish line with 0.8 mm depth at the other side with 10° taper. Ten impressions were made of the die and poured with epoxy resin. Ten zirconia copings (Ceramill) were fabricated and vertical gap (at one point for each finish line) before cementation and marginal gap and internal gap (at five points for each finish line) after cementation (with glass ionomer under 5 N load for 10 minutes) were measured using a scanning electron microscope (SEM). The mean values were compared using t-test. Vertical gap was 42.06±15.2 μm for deep chamfer and 25.2±10.3 μm for sloped shoulder design. Marginal gap was 98.3±7.06 μm for deep chamfer and 94.3±27.17 μm for sloped shoulder design. The internal gap was 154.75±46.94 μm for deep chamfer and 162.35±43.49 μm for the sloped shoulder design. The difference in vertical gap was significant between the two designs (P<0.01) while the difference in marginal and internal gap was not significant (P>0.05). The results showed that the preparation design had no significant effect on marginal gap of zirconia restorations but affected the vertical gap.