Restorative Dentistry - Crowns & Bridges

Information About Tooth Crowns

There are occasions when a tooth needs to have a more substantial restoration than a mere filling.  If a tooth is fractured (due to trauma, significant decay, or old silver filling) placement of filling material alone is not enough to withstand the massive amounts of pressure biting forces apply to the teeth.  If a back tooth has had a root canal, the risk of breaking the tooth and root are increased.  These teeth need to be crowned, or risk extraction.  Though a big filling can fill a hole and preserve the tooth long enough for a stronger restoration to be placed, to restore the tooth to true function and protect it for the future, a restoration stronger than a filling needs to be used.  A crown (sometimes referred to as a "cap") is strong enough to withstand the heavy load placed on teeth and restore the tooth to it's true function.

A crown works by surrounding the tooth in very strong ceramic, noble alloy, or a porcelain fused to metal combination.  By fitting the crown over the tooth, the tooth is surrounded in a single strong material that disseminates the bite forces throughout the crown protecting the underlying tooth.  This saves the tooth from wedging or splitting down the tooth which can result in fracture, need for root canal, or worse yet, extraction.  Crowns can be used on both front or back teeth, depending on the extent of the amount of tooth to be restored.  Crowns strengthen the tooth, protect the remaining tooth, and improve the appearance.  We have the ability now to place crowns made of all-ceramic material that have an extremely hard center and yet don't need the metal cores of traditional crowns.  Lack of metal under the porcelain makes for a more vital natural looking tooth and there is no dark margin seen along the gumline that some older porcelain crowns exhibit.  In addition, all ceramic crowns can be used in conjunction with porcelain laminate veneers on front teeth depending on how much tooth needs to be restored, for maximum esthetic result.

The following is a graphical illustration showing how a large defective amalgam filling is prepared and a crown then cemented over the remaining tooth, restoring the tooth to it's ideal shape and function.

Fig. 1

Information About Bridges

If a tooth is missing and the teeth next to the space could benefit from crowns (previously restored with fillings, fracture lines, previous root canals), then a bridge is an ideal option.  A bridge is effectively multiple crowns connected to one another.  The number of crowns involved is determined by how many teeth need to be replaced.  A bridge is a minimum of three teeth, but can be much longer depending on how many teeth are to be replaced. Teeth on either side are prepared for crowns, a replacement tooth (also called a pontic) connects to both and the area is stabilized.  A bridge accomplishes a number of tasks.  It provides full coverage and strength for the teeth next to the missing teeth.  It prevents the teeth from spreading out, tipping, and super-erupting from the opposing teeth by stabilizing the bridged section.  It replaces the tooth permanently without the use of a removable appliance, or denture.  In instances where a dental implant (see our section on dental implants) can't be used, but a tooth needs to be replaced, a bridge can be an ideal restorative option.  Bridges, like crowns, can be placed on both front and back teeth.  The type of material used for the bridge can be recommended to you by the dentists here at Biddeford Saco Dental Associates.

The following is a graphical illustration showing the preparation of teeth on either side of a space for a bridge and subsequent placement of the bridge, restoring the teeth to their ideal shape and function.