TYPES OF CROWNS
The Hat and the Helmet
An onlay (“Hat”) can be placed on the tooth with minimal tooth reduction, but a full coverage crown (“Helmet”) requires a tremendous amount of tooth reduction and invasion to cover the entire crown portion of the tooth. Because of today’s advanced adhesion technology, it is no longer necessary nor advisable to fully cover the entire tooth unless large portions of the natural tooth are already missing.
In these two sequences, it is easily seen how the partial coverage onlay (“hat”) requires very little tooth invasion and is difficult to detect when bonded in place. The sequence of photos showing the placement of a porcelain-fused-to-metal crown (“helmet”) depicts the invasion and tooth reduction necessary to place a full coverage crown.
Pressed Ceramic Onlays (The Hat)
Pressed ceramic onlays are minimally invasive, esthetic and permanently bonded restorations. The x-ray displays how minimal these restorations can be, how well they fit and how most of the tooth remains undisturbed.
Pressed Ceramic and Cast Gold Onlays (The Hat)
When minimally invasive onlays are placed on teeth located in high-leverage zones of the mouth (especially on strong young men) it is sometimes best to forgo esthetics in favor of long-term function. Pressed ceramic restorations sometimes fail in these areas, but cast gold does not.
Full Porcelain or Pressed Ceramic Crowns (The Helmet)
These photos display the gross invasion and reduction necessary to place full coverage porcelain crowns. Although the dentistry was accomplished with great care, all three of these full crowns will probably not last a lifetime and will most probably require future replacement.
Porcelain-Fused-to-Metal Full Crowns (The Helmet)
These photos again display the amount of tooth invasion and reduction necessary to place four full coverage crowns on these back teeth. With extreme care and caution this procedure can be successfully accomplished; however, this treatment is much like brain surgery and heart surgery: unless there is no alternative, you are better off without it.
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