有金属顶盖的长冠基牙制备时，单顶盖通常牙冠磨短至龈缘以上3－5mm；基牙轴面的龈殆向聚合度较金属全冠稍大；始面制备成钝圆形。双层顶盖通常与单顶盖基本相同；不同处在龈缘处的牙制备量较多，约相当于内沙十顶盖金属的厚度。
In the preparation of Long crown abutment teeth with metal crown, the single crown is usually grinded as short as 3-5mm above the gingival margin; the degree of gingival aggregation on the axial surface of abutment teeth is slightly larger than that of the metal full crown; the initial surface is made into a blunt circle. The two-layer top cover is generally the same as the single top cover, and the amount of teeth prepared at the gingival margin is more, which is about the same as the thickness of the metal of the top cover.