The portion of our teeth that extends through the gums is called the crown of the tooth or the natural clinical crown. Often people confuse the natural crown with an artificial crown or cap. Technically, most people have 32 crowns in their mouth.
When most people talk about crowns, they mean an artificial crown. When a natural tooth is badly decayed, is broken or cracked, or has been filled and re-filled multiple times with frequent failure, your dentist may recommend a crown. In this case, the crown is an artificial covering over our natural crown. The decay is removed, and the remaining natural crown is reduced in size to make room for the new artificial crown. For most teeth a local dental anesthetic is used to make the procedure very comfortable and pain free.
Often there is too much tooth that is missing from the original decay or fracture. The new crown needs a firm, solid foundation to rest upon so your dentist may place a build up first. The build up is a restorative material that reshapes the remaining tooth for ideal contours, shape and size so the new crown can fit ideally over the remaining tooth and build up. The build up material is often composite which is bonded to the tooth.
Traditionally after the tooth as been prepared, an impression or model of the area is taken and is sent to a dental lab where the new crown in fabricated. The crown can be made of any combination of base metals (nickel), gold, palladium and porcelain. While less expensive, crown made of base metals are not recommended. One main clinical advantage of the all porcelain crown is that x-ray will go through the crown reveling any future decay. All metal or porcelain fused to metal crowns block the x-rays, often masking hidden decay.
A lab made crown can sometimes take several weeks to make. During that time a temporary plastic crown covers the prepared tooth. This is cemented in place using a temporary cement to facilitate easy removal when the permanent crown is ready. Unfortunately often the temporary crown comes off during the waiting period causing discomfort and requiring a return visit to the dentist to re-cement. This can be especially bothersome and embarrassing if it is a front tooth getting a new crown or a veneer.
New dental technology uses CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) to eliminate these inconveniences. After the tooth is prepared for the crown using traditional methods, a high quality impression is taken of the prepared tooth and the adjacent teeth in the arch. An impression of the relationship between the upper and lower teeth in that arch is also taken.
At this point the patient can return to work, home, run errands or relax in the dental chair while the new crown is made. Using lower power lasers, the details of the prepared tooth, the adjacent teeth and the opposing teeth are scanned into the specialized computer design center. Specialized proprietary software combine the digital scans with data about each tooth is shaped and sized to create a near ideal new crown. Using the mouse and specialized software tools, the new crown is made to be the perfect, ideal replacement crown for the damaged natural crown.
This data is transferred digitally to the 3D milling station where a solid block of porcelain is cut away leaving the ideal replacement crown ready to be cemented or bonded to the prepared tooth all in the same day.
Source by Bruce E Howell