Usually, after the completion of the root canal treatment, the doctor will recommend the patient to have a “brace” to protect the affected tooth. I believe many people do not know much about “braces”, so here is a brief introduction. 1. What is “braces”? Due to caries, dental trauma, wear and tear, developmental malformation and other reasons, the hard tissues of the teeth are damaged to different degrees in shape and structure, which affects chewing, pronunciation and aesthetics, and this dental disease is called “dental defect”. In cases of severe defects or when strict aesthetic requirements are to be met, restorative treatment is often used in clinical practice. Full crown restoration is the common restoration, also known as “braces”. 2. Why do we need “braces”? Root canal treatment is to completely remove the nerve and blood vessels of the infected tooth to control the infection. In addition, during the root canal treatment, some of the decayed tissues of the tooth are worn away and the ability to resist chewing is reduced. In order to protect the remaining tooth tissues and enable the teeth to continue to function, braces need to be made on the tooth surface. 3. What are the types of “braces”? Braces are mainly classified according to the materials and techniques used to make them. The following are some of the commonly used ones in clinical practice. (1) Cast metal crowns. It is mainly used for posterior teeth, especially for teeth with severe defects and short crowns. However, patients with allergies to metal materials are not suitable; metal may have an effect on certain imaging examinations (MRI). The main materials used clinically are: gold alloy (excellent performance, good biocompatibility); cobalt-chromium alloy (high hardness, cheap). (2) porcelain fused to metal crowns. Also commonly known as “porcelain teeth”, a wide range of applications, both the strength of metal and porcelain full crown aesthetics. Compared to metal crowns, the amount of tooth removal is higher. (3) All-ceramic crowns. Have excellent aesthetic properties, and the most similar to natural teeth; compared to metal has better biocompatibility, chemical properties are more stable. However, ceramic has lower strength compared to metal, the amount of tooth abrasion is large, and the requirements for the surgeon are higher. Clinically, there are mainly: glass ceramics (good light transmission, outstanding aesthetic properties), zirconia ceramics (high strength, higher price). The above is for reference only. The choice of the type of braces is determined by the condition of the affected teeth, oral hygiene habits and dietary habits, personal wishes and other aspects.