Root canal treatment is a procedure in which the dentist opens the diseased tooth, removes the inflamed and necrotic pulp tissue with various instruments, disinfects and cleans the pulp cavity (including the walls of the pulp cavity), and then seals the cavity tightly with dental cement. Generally speaking, root canal treatment is suitable for those with pulpitis, pulp necrosis, and all types of apical periodontitis, including pulpitis caused by caries, cryptic fissure, excessive consumption, pulp penetration, and pulp necrosis that cannot retain living pulp. Many patients don’t understand why, after root canal treatment, the tooth doesn’t hurt anymore, and it’s enough to fill it, why do we need to do a full crown to protect it? In fact, this step is necessary for three main reasons: Why do you need a “set”? After root canal treatment, the tooth is no longer resistant to chewing. Root canal treatment involves the use of medication and instruments to remove and sterilize as much debris and bacteria as possible from the root canal. However, if this sterilization process is to be carried out carefully, a lot of bacteria-infected teeth have to be removed, as well as the tooth tissue that has to be trimmed. Therefore, most of the teeth may not be strong enough to support the chewing force once the root canal treatment is performed and may break, and the function cannot be restored by using materials alone, and even if it can be restored, the long-term effect will not be good. After root canal treatment, the tooth loses the nutrient supply from the pulp, just like a tree that loses its roots, it slowly withers and becomes fragile, resulting in increased brittleness of the tooth and easy to split. 3, root canal treatment of the tooth after the defect is large, very fragile Because the need for root canal treatment of the tooth is generally caries (insect teeth), the defect is very large, this time although the root canal treatment is completed, but the rest of the tooth tissue is very fragile, very easy to fracture, cracked, lost normal function, purely with the material can not be restored to function. 4, do crown materials ordinary cheap – nickel-chromium alloy nickel-chromium alloy materials, cheaper, in Europe and the United States belongs to the elimination of technology, metal crowns will produce long-term use of nickel precipitation, 15% of users have a mild toxicity and allergic to the gathering of metal so that the gums black. 5, affordable – cobalt chromium alloy semi-precious metal crowns are represented by cobalt chromium alloy crowns, called “nickel-free beryllium-free alloy”. The main component is cobalt, chromium, its price between non-precious metals and precious metals, its biocompatibility is better than nickel-chromium alloy crowns, corrosion resistance, not easy to appear chipped porcelain, can avoid the phenomenon of bleeding gums and black gums. Moreover, it is economical, practical and suitable for most teeth restoration, especially suitable for fixed restoration such as fixed bridge for back teeth. 6, star like teeth – all-ceramic crowns The color of all-ceramic crowns can maintain the natural color both in the light and natural light, so it has become the favorite of movie stars and public figures in dental beauty. All-ceramic crowns have good permeability and color, excellent aesthetic effect, good biocompatibility, harmless to the human body. All-ceramic teeth according to the material is divided into two categories of aluminum oxide and zirconium dioxide, both in addition to the strength, the production process is different, have very good biocompatibility, durability is better, can be permanently preserved in the oral cavity; due to the absence of a metal substrate, all-ceramic teeth are lighter in quality, more comfortable to wear, and more conducive to the protection of dental pulp health; the reflection and scattering of light is closer to the natural teeth, and therefore have a better aesthetic effect.