Dental Education Lecture: Crowns & Bridges

In last lecture, we discuss that we need a crown for protection when our back tooth is in bad shape (especially after root canal).  We do not routinely need to crown a front tooth after root canal.  But for cosmetic reason, we may need to place several crowns.  For example, Tetracycline teeth are difficult to fix.  In Fig.1, composite (white filling) used to cover up (veneer these discolored teeth) has been lost.  There is also a severely chipped tooth in the front.  We need to take that tooth out.  Therefore the most appropriate treatment for this case is to prepare several teeth (Fig.2) for crowns and a bridge.  The final result is quite satisfactory.

Fig.1

Fig.2

Fig.3

Fig.4

Fig.5

Fig.6

As compared to veneers, crown and bridge preparation is a little less conservative.  To prepare for crowns and bridges, we need to take off the outer layer of the teeth for 360 degrees, whereas 180 degrees for veneer preparation.  These days we have better alternatives to replace some of crowns & bridges, such as implants and orthodontics (braces).  We should avoid crowns & bridges if possible.  Let us use the following case to demonstrate the point.

A young gentleman has one missing front tooth (lateral incisor) by birth.  The canine tooth (with a sharp point, 2nd tooth from the right in Fig.4) is shifted to the front, leaving a gap behind.  He wants to close the space.  We provide to him with two options.  The first one is to use braces to push the canine backward to where it is supposed to be and create a space in the front.  Then we place an implant in the front.  The advantage of this treatment is that we are able to achieve the most cosmetic and natural restorations.  The drawback is time and finance.  For personal preference the patient chooses the second option.  That is to shape the canine and the tooth behind it (Fig.5) and to make a three-unit bridge (Fig.6).  Although he is much pleased with the final result, he has lost the most precious thing in his body (enamel).  Basically he has lost two virgin teeth.  To keep this bridge, he needs to maintenance local oral hygiene very well by using threader or superfloss. 

The advantage of crowns and bridges is that you feel everything normal when they are properly done.  Crowns and bridges are called fixed restorations, because they stay in your mouth.  In the beginning of next chapter Senior, we will discuss dentures, which are removable restorations.  You can take them in and out.  Dentures are relatively big, replacing several missing teeth, whereas bridges are small (close to normal in size), replacing one to two missing teeth.  If you want to know more about dentures, go to next chapter: Senior.

Xin Wei, DDS, PhD, MS 1st edition 02/12/2009, last revision 02/13/2009