dental crown
In dentistry, the crown is the portion of the tooth that protrudes from the gum. This field is naturally covered by a very hard material, the tooth enamel.The term also refers to ring by extension the prosthetic crown, a dental prosthesis for protecting a tooth that is alive or not (devitalized). It covers the portion of the remaining tooth restoring the coronal part, preserving the tooth further attacks while avoiding its extraction and complete replacement.
It also happens that patients require crown lengthening to improve the aesthetics of the smile, in order to reduce a smile.
Types of crowns
It can be ceramic, chrome-cobalt, nickel-chrome or precious metal. The all-ceramic crowns (ceramic on ceramic cap) and those made of precious metal or titanium offer the best guarantees against the risk of allergies.
Nickel-chromium does not provide the same guarantees. Thus, for the restoration of teeth made of nickel-chrome, black tattoo, little aesthetic may appear on the gums in contact with the alloy. Surgery alone can overcome this problem and removing the crown will not suffice.
For anterior teeth, the dentist asks for aesthetic ceramic or metal-ceramic crowns (knowing that in time a metal border appears around the gums). For posterior teeth, aesthetic impact is less important, the dentist often ask for financial reasons metal crowns.
For anterior teeth, the dentist asks for aesthetic ceramic or metal-ceramic crowns (knowing that in time a metal border appears around the gums). For posterior teeth, aesthetic impact is less important, the dentist often ask for financial reasons metal crowns.
Reasons for the establishment of a crown
Tooth decay
Radiography and photography of a second molar restored with a large amalgam. If this tooth required a new restoration following a recovery decay or fracture, the structure of the tooth remaining after removal of amalgam and decayed tissue would not be sufficient for the installation of a new amalgam. The placement of a crown would be appropriate.
A tooth that has received endodontic treatment (root canal or) is called devitalized, that is to say, its pulp containing the nerve and vessels was removed and the formed cavity has been properly cleaned and filled to prevent invasion of bacteria thereafter.
Following this treatment, it remains generally not enough to make a dent in an amalgam filling as in the case of a simple decay. Furthermore, devitalization has made much more fragile and brittle tooth relative to its neighboring live: the risk of tooth fracture vertically sooner or later and it will certainly be necessary to extract. To avoid this, the dentist cap the tooth devitalized a prosthetic crown. The risk of fracture increases significantly devitalized teeth on posterior teeth when a crown does not protect. In fact, the average person has significant strength in these posteriors which is approximately nine times greater than that exerted on the anterior teeth. If the actual posterior contact area is 1 mm², while a pressure of more than 7109 Pa exerted on the restoration. This is why the posterior teeth (that is to say, the molars and premolars) are in almost all situations, be crowned after undergoing root canal treatment to protect the fracture.
Referance By:-
http://fr.wikipedia.org/wiki/Couronne_%28dent%29