If the gums appear red, swollen, bruised and black after setting porcelain teeth, the reasons are mainly the following: 1, improper mastery of indications: when making porcelain teeth, the gums should be in a healthy state. If the original inflammation of the gums, swelling is not eliminated, inflammation of the gums is more likely to be prolonged. So in the production of porcelain teeth before, should be perfect periodontal treatment, so that the gums are completely restored to health; 2, irregular operation caused damage to the gums: the production of porcelain teeth need to choose special instruments, the use of formal techniques and in strict accordance with the operating precautions. If the operation is not skilled, it is easy to hurt the gums during the operation, resulting in swollen gums; 3, porcelain teeth are poorly made, the shape is not correct resulting in adverse stimulation of the gums: this is the most common cause. The edge of the porcelain crown should be smooth, continuous and coordinated with the shape of the root, closely connected with the root. Crown edge made too thick, too thin, not smooth or porcelain crowns and gaps between the body will cause stimulation to the gums, resulting in swollen gums; 4, porcelain dental materials selected to cause gum stimulation: domestic porcelain dental metal layer is mostly made of nickel-chromium alloy (a stainless steel), nickel-chromium alloy in the nickel ion is not stable, easy to free to the gums, so that the gums are red, painful, but also make the gums are greenish gray. After the porcelain gum redness and swelling, the first should use conventional periodontal treatment to remove the gum and the neck of the tartar and plaque, and rinse with mouthwash; if there is no effect, you need to remove the porcelain teeth, replaced by a temporary crown with good edge shape to do a period of observation; if the gum swelling is still not better, you need to use gingivectomy to remove the gum part of the hyperplasia.