POST CROWNS HAVE NO ROLE IN MODERN DENTISTRY

Post Crowns Have No Role in Modern Dentistry

Post Crowns Have No Role in Modern Dentistry

The crown of a natural tooth is that portion which is covered with enamel and is generally above the gum line. In the schematic on the right, the roots of the teeth are colored yellow, and the crowns are covered with white enamel. This is the ideal state of nature, and this shape, color and relative proportions are about what dentists aim to recreate with artificial materials whenever the natural crowns of the teeth are deficient in some way.

Looking at the same tooth in cross section, you can see that the enamel is a thick glass-like substance that covers the sensitive internal portion at the top of the tooth. This sensitive internal part is really just an extension of the root above the gum line. If the enamel is defective because of discoloration, decay, or is misshapen, the ideal solution would be to remove just the enamel and replace it with a new covering which would have a more ideal form and color. And in fact, that is what we try to do. The new covering is called (appropriately) a crown, and it is usually made of porcelain, or porcelain covering an internal metal or ceramic coping which gives the restoration extra strength. (By the way, there is no such thing as a "cap" in dentistry. This term is misused by the public to describe numerous dental services such as fillings, crowns, veneers and fixed bridges. Its lack of a fixed definition makes it a useless term in the profession of dentistry.( Azarpazhooh, 2008, 45-99)

When a tooth is reduced in size to accept a crown, the portion that will underlie the crown is called the core. The condition of the core affects the retention and stability of the crown which will be placed on it. If the core is too small due to damage caused by old decay or fillings, then the crown may not retain well and could loosen or come off and need to be re-cemented frequently. If it is too thin, then it could snap off inside the crown when the tooth suffers serious trauma. .( Azarpazhooh, 2008, 45-99)

The all-porcelain crown (pictured on the left) allows the color of the original tooth underneath to shine through. These crowns have the advantage of being truly translucent, and show no metal at the gum line. They are the closest thing to the ideal enamel replacement mentioned above that modern dentistry has yet invented. While they are not as strong as porcelain fused to metal crowns, their technology has improved over the years to the point where they are many times stronger than they used to be. The strength of modern porcelain crowns derives partly from the bonding techniques used to attach them to the core. The glass inside the crown is etched, and bonding agents are used to bond them directly to the ...