Abstract
Purpose: This study evaluated the influence of different cervical margin forms onthe adaptation and the thickness of the electroformed metal coping.
Methods: Master and replicated dies were fabricated from three steel dies that were prepared for a full-baked type metal-ceramic restoration of a maxillary central incisor. Three cervical margin forms were used: shoulder, round shoulder and deep chamfer preparation (S type, RS type, DC type). Metal copings were electroformed to an identical thickness at a corresponding place in the electroplating bath. After trimming the margin, the marginal discrepancy was measured at four points (a, b, c, d) each 90 degrees from the labial center of the metal coping on the master die. All specimens were embedded in acrylic resin and sectioned. The internal gap and the thickness of metal coping were measured at six points (A: labial marginal area, B: labial line angle of chamfer or shoulder, C, D: labial, lingual axial surface 1.0 mm from the abutment margin, E: ingual line angle of chamfer or shoulder, F: lingual marginal area). A laser microscope was used for the measurement and each group had five specimens. The measured values were analyzed statistically using the Kruskal-Wallis test and Bonferroni Correction. A significance level of p<0.05 was used for all comparisons.
Results: Regarding the marginal discrepancy at all measured points, the S type exhibited significantly poor values as compared with the DC·RS type. The internal gap of the S type was significantly poorer than that at A, B or F. The thickness of the S type was significantly thinner than that at B and E. The mean thickness of the S type was 51.2μm at B, 56.3μm at E.
Conclusions: This study confirmed that the cervical margin form influenced the metal coping formation manufactured using electroforming.
