Identify the good and bad porcelain teeth a, look at the color. Porcelain crown color soft, not the whiter the better. In order to cover the color of the metal inner crown, there must be a certain thickness of the porcelain layer, often the thicker the porcelain layer, the better the aesthetic effect. Insufficient clinical tooth preparation, it is easy to appear porcelain teeth are chalky white or dull, fat. Identify the good and bad porcelain teeth two, look at the edge. The precision of the edge of the porcelain teeth, is the identification of porcelain teeth is one of the most basic criteria for judging the merits of the precision is reflected in the seam between the porcelain crown and the tooth, the smaller the gap the better, otherwise bacteria are easy to enter, resulting in tooth decay inside, fracture, resulting in the failure of the restoration. Identify the good and bad porcelain teeth three, look at the gums. Gums should not bleed during the operation, no redness, swelling, congestion, discoloration after the operation. In the operation in the cervical preparation, if not careful to protect the gums, often resulting in bleeding gum damage, which is prone to gum redness, bleeding, atrophy after setting porcelain teeth, affecting the beauty of the front teeth, but also not conducive to high-precision mold taking. Identify the good and bad porcelain teeth four, look at the morphology. The shape of the tooth is normal, not hypertrophy, lip and tongue without foreign body feeling. At the same time to have a clear grasp of the characteristics of various porcelain crowns, performance, and make personalized dental preparation, to ensure sufficient thickness of the porcelain layer to achieve the minimum amount of abrasive tooth tissue.