Thickness of the Metal Frame by Electroforming: Influence of Positioning Die in the Electroplating Solution

Purpose: In the gold electroforming system, metal frames are made in a rotating current of the electroplating solution. It is thought that the position of the die influences the thickness of the metal frame. This study evaluated the influence of the position of the die on the thickness of the metal frame. Methods: This study used the GAMMAT system and GAMMAT easy (Gramm) for the electroforming system and unit. Gypsum dies were fabricated from a master epoxy model that was prepared for a full-baked type metal-ceramic restoration of a maxillary central incisor (Shofu). Metal frames with a thickness of 200μm were fabricated following the manufacturer's instructions. Dies were set up in three different positions in a glass beaker (∅56.0mm): 1. center of the beaker (P0), 2. 11.0 mm from the center of the beaker (P1), and 3. 22.0 mm from the center of the beaker (P 2). All specimens were embedded in acrylic resin, sectioned in a labiolingual plane, and the thickness of the metal frame was measured using a laser microscope (Laser microscope 1 LM 21 W, Lasertec). There were five measurement points (a: labial central area, b: incisal edge, c: lingual central area, d: top of cingulum, e: axio lingual central area). There were five specimens in each group. The data were analyzed by the Kruskal-Wallis test and Bonferroni Correction. Results: The thickness of the metal frame was P0>P1>P2 at d and e, and P0>P1≥P2 at b. There were no significant differences at a and c. P 0 was the largest of all the measurement points, and was nearly 200μm. Conclusions: This study indicates that the position of the die influences the thickness of the metal frame, and that the thickness might be less than the value (200μm) at which the die was set up.