Metal Free Crowns, Ceramic, Zirconia
Shre Vinayakaa Dental Clinic
Metal Free Crowns, Ceramic, Zirconia
A crown is a type of dental restoration which completely caps or encircles a tooth or dental implant. Crowns are often needed when a large cavity threatens the ongoing health of a tooth. They are typically bonded to the tooth using a dental cement. Crowns can be made from many materials, which are usually fabricated using indirect methods. Crowns are often used to improve the strength or appearance of teeth. While inarguably beneficial to dental health, the procedure and materials can be relatively expensive. The most common method of crowning a tooth involves using a dental impression of a prepared tooth by a dentist to fabricate the crown outside of the mouth. The crown can then be inserted at a subsequent dental appointment. Using this indirect method of tooth restoration allows use of strong restorative materials requiring time consuming fabrication methods requiring intense heat, such as casting metal or firing porcelain which would not be possible to complete inside the mouth. Because of the expansion properties, the relatively similar material costs, and the aesthetic benefits, many patients choose to have their crown fabricated with gold.
As new technology and materials science has evolved, computers are increasingly becoming a part of crown and bridge fabrication, such as in CAD/CAM Dentistry.
There are additional situations in which a crown would be the restoration of choice.
Dental implants are placed into either the maxilla or mandible as an alternative to partial or complete edentulism. Once placed and properly integrated into the bone, implants may then be fitted with a number of different prostheses: crowns or bridges precision attachments for either removable partial dentures, complete dentures or a hybrid sort of prosthetic appliance.
When teeth undergo endodontic treatment, or root canal therapy, they are devitalized when the nerve and blood supply are cut off and the space which they previously filled, known as the "pulp chamber" and "root canal", are thoroughly cleansed and filled with various materials to prevent future invasion by bacteria. Although there may very well be enough tooth structure remaining after root canal therapy is provided for a particular tooth to restore the tooth with an intracoronal restoration, this is not suggested in most teeth. The vitality of a tooth is remarkable in its ability to provide the tooth with the strength and durability it needs to function in mastication. The living tooth structure is surprisingly resilient and can sustain considerable abuse without fracturing. But after root canal therapy is performed, a tooth becomes extremely brittle and is significantly weaker than its vital neighbors.
The average person can exert 150–200 lbs (70–90 kg). of muscular force on his or her posterior teeth, which is approximately nine times the amount of force that can be exerted in the anterior. If the effective posterior contact area on a restoration is 0.1 mm², over 1 million PSI of stress is placed on the restoration. Therefore, posterior teeth (i.e. molars and premolars) should in almost all situations be crowned after undergoing root canal therapy to provide for proper protection against fracture (mandibular premolars, being very similar in crown morphology to canines, may in some cases be protected with intracoronal restorations). Should an endodontically treated tooth not be properly protected, there is a chance of it succumbing to breakage from normal functional forces. This fracture may well be difficult to treat, such as a "vertical root fracture" . Anterior teeth (i.e. incisors and canines), which are exposed to significantly lower functional forces, may effectively be treated with intracoronal restorations following root canal therapy if there is enough tooth structure remaining after the procedure.