Root canal therapy, commonly known as nerve extraction, is a procedure in which the dentist opens the diseased tooth, removes the inflamed, necrotic pulp tissue from the tooth with a variety of instruments, disinfects and cleans the pulp cavity (including the pulp cavity wall), and then seals the cavity tightly with cementum and other materials. 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 the 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 very necessary for three main reasons: Reasons for doing crowns 1. Root canal treatment is to remove and sterilize as much debris and bacteria as possible from the root canal by using medication as well as instrumentation. However, if this sterilization process is to be carried out seriously, a lot of bacteria-infected teeth and tooth tissues that have to be trimmed have to be removed. Therefore, most of the teeth, once root canal treatment is performed, may not be strong enough to support the chewing force 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. 2. After root canal treatment, the tooth loses its nutrient supply from the pulp, just like a tree that loses its roots, slowly withers and becomes fragile, causing the tooth to become more brittle and prone to splitting. 3, because the need for root canal treatment of the tooth is generally caries (worm teeth), defective, although the root canal treatment is completed, but the remaining dental tissue is very fragile, very easy to break, crack, lose normal function, simply with the material has not been able to restore function. 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 nickel precipitation in the long-term use of 15% of users have a mild toxicity and allergic reactions, and in the formation of nickel metal in the gums of the user’s gums to form a collection of black gums. Affordable, cobalt-chromium alloy The representative of semi-precious metal crowns is cobalt-chromium alloy crowns, which is called “nickel-free and beryllium-free alloy”. The main ingredients are cobalt and chromium, its price is 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 bleeding gums and black gums phenomenon. And it is economical, practical and suitable for most teeth restoration, especially suitable for fixed restoration such as fixed bridge for posterior teeth. Higher strength, no stimulation, precious metal The representative of precious metal crown is gold alloy crown, according to the content of gold is divided into medium gold (56.7%), high gold (86.7%) two kinds, it is one of the most ideal restoration materials, higher strength, no stimulation, and the combination of gold and porcelain is very strong, and the compatibility with the tissues is better, and will not be green in the place of the crown and the contact of the gums. In addition, the crown can react to its own color on the surface of the gold, so that the crown of the soft color, good aesthetics, can fully meet the requirements of cosmetic restoration, it is also a very good material for dental implants. Star-like teeth, all-ceramic crowns The color of all-ceramic crowns can maintain its natural color no matter under the light and in the natural light, so it has become the current favorite of movie stars and public figures in dental aesthetics. 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. Nickel-chromium alloy crowns Cobalt-chromium alloy crowns Precious metal crowns All-ceramic crowns