What Are the Causes of Dental Bridge Failure?

Dental bridges are cast metal and ceramic prosthetic devices that replace missing teeth in a more permanent fashion than partial dentures. The dentist uses the healthy dentition around the missing teeth to create a bridge, which limits tooth removal and creates a more aesthetically pleasing appearance. The majority of permanent bridges remain secure, but bridges can fail for several reasons.

Basic Bridge Information

• There are various styles of cast bridges made in dental offices today, some of which fail more easily than others. The most common bridges have three or more units, called tooth bridges, that crown the abutment or adjacent teeth and have pontics, or false teeth, soldered in between. Another bridge is a cantilever bridge. It involves one tooth being crowned with a fake tooth cantilevered, or soldered on one side, and cemented in place. Maryland bridges are conservatively constructed, removing the least amount of tooth structure. They are not made as crowns, they have little metal wings that bond to the backs of the abutment teeth with the pontic soldered in between.

Margins and Decay

• Margins are the dental term for the area where a crown and abutment, or anchor tooth, meet. When running a sharp explorer, such as a dental instrument, around the margin there should be no gaps or spaces allowing the tip of the explorer under the crown. This is necessary to prevent the spread of decay under the margins. Good oral hygiene at the margins of the bridge is vital. They are areas that collect more plaque than ordinary. Failure to maintain hygiene can cause decay to grow around the margin, compromising the bridge and eventually causing the need for removal. Brushing too hard at the gum line can also warrant removal of the bridge for aesthetic reasons. Aggressive brushing can push the gums away from the teeth, exposing the dark line of the margin. This can be both embarrassing and unsightly.

Improper Cementation or Bonding

• When cementing a bridge or bonding a Maryland bridge, the areas being worked on must remain as dry as possible. Contamination of the tooth with saliva, especially on the bonded Maryland bridge, can cause bridge failure. On the Maryland bridge, saliva contamination will prevent a strong bond and the bridge will generally come off or be knocked off within a short time. Saliva contamination of the teeth the abutment crowns get cemented to can undermine the cement, breaking it down, causing the bridge to fall off. None of these situations means the bridge must be thrown away and re-done, but they will need recementation or re-bonding.

Poor Oral Hygiene

• Poor oral hygiene is a threat to all oral restorations. Poor oral hygiene leads to decay and bone loss from gum disease. The most common cause of bridge failure is gum disease leading to the loss of teeth that support bridges. Gum disease is even more of a threat than decay because decaying areas often can be patched and filled with restorative materials. But nothing can replace a bridge falling out, tooth and all, because the gums and bone have been destroyed. The best way to prevent bridge failure is practicing good oral hygiene at all times.