Finishing-line Curvature Affects the Marginal Gap of All-ceramic Copings

Objectives: To investigate the influence of finishing line curvature on the marginal gap of three systems of all-ceramic copings.

Methods: An ivorine maxillary central incisor was successively prepared with three types of abutment finishing line curvatures (1, 3, and 5 mm vertical distance between labial or lingual margins and proximal margins). Thirty six copings for each curvature were fabricated with Cercon, IPS e.max, and Lava™ systems and the vertical marginal gap width was measured using a stereo microscope by one investigator. Two-way ANOVA followed by one-way ANOVA tests were used to determine statistical significance between the mean marginal gap for each abutment finishing line curvature and ceramic system.

Results: The 5 mm. finishing line curvature copings (Cercon, 76.59±48.50 µm ; IPS e.max, 106.44±42.12 µm ; Lava™, 128.34±42.81 µm) showed a significantly higher mean marginal gap than the 3 mm. curvature group (Cercon, 60.18±32.49 µm ; IPS e.max, 81.79±29.08 µm ; Lava™, 99.19±28.22 µm) and the 1 mm. curvature group (Cercon, 38.3±13.36 µm ; IPS e.max, 52.22±14.87 µm ; Lava™, 69.99±51.62 µm).

Conclusions: The greater the finishing line curvature, the larger the vertical marginal gaps in the three all-ceramic systems tested. Copings fabricated with the Lava system showed the greatest marginal gaps compared to the  IPS e.max and Cercon systems.