When designing a dental bridge, two important factors are involved :

• Edentulism type : only certain types of edentulism benefit from dental bridge restorations.

• General and specific criteria regarding the abutment teeth :

  • General requirements: each abutment tooth should meet them.

  • Specific criteria : each class of teeth has a different role in supporting the dental bridge.

Besides these, other important aspects should be considered.

Length of the pontic

When more teeth are missing in the same part of the mouth cavity, the "length of the pontic" (or the number of pontics) increases because more artificial teeth have to be designed. As mentioned, it is not advisable to overextend the pontic.

As a general rule, a traditional dental bridge is not indicated when more than 4 teeth are missing inside a single toothless gap.

In the picture above, we have a gap of five missing teeth. It is not desirable to restore the gap with a traditional dental bridge. See why

For this particular situation, restorations supported by dental implants or removable partial dentures are more appropriate therapeutic solutions.

What happens when 3 or 4 adjacent teeth are missing ?

When a dental bridge has many pontics, the pressures that act on the abutment teeth during mastication increase. Each individual pontic will pass the chewing forces to the abutment teeth.

In the picture above, there are 3 missing teeth : 1 molar and 2 premolars. It is indicated to design 3 abutment teeth (as marked) instead of just the 2 adjacent to the gap. This way the chewing forces will be distributed between them and the dental bridge will have a better prognosis.

Conclusions

1. When more than 4 teeth are missing inside a single toothless gap, a traditional dental bridge is not indicated as a therapeutic solution.

2. If more than 2 teeth are missing (but less than 5) inside a single gap, it is wise to include more abutment teeth.

Cantilever bridges

Sometimes, for certain aesthetic or clinical reasons, dentists are forced to manufacture bridges that have dental support on only one side of the toothless gap. These restorations are called cantilever bridges. In these cases, the pontic is located outside the abutment teeth.

cantilever bridge with 3 abutments

Dental occlusion

More technically, the dental occlusion (or the bite) is the relationship between the maxillary (upper) and mandibular (lower) teeth when they approach each other, as it occur during chewing or at rest.

Static occlusion

Static occlusion refers to contacts between teeth when the jaw is closed and stationary.

In this position, the practitioner must determine whether there is enough space to shape the artificial teeth properly. An edentulous space may reduce its vertical dimensions because of opposite teeth migration (also known as overeruption).

the vertical dimension of the toothless gap is reduced because of opposite teeth migration

Such situations call for preliminary procedures that aim to increase the height of the toothless gap and create adequate space for the dental bridge.

Dynamic occlusion

Dynamic occlusion refers to occlusal contacts made when the jaw is moving, such as when chewing.

It is significant to determine the intensity of chewing forces that will act on a dental bridge. This may depend on various factors :

• Chewing forces are greater if natural teeth are opposite to the designed bridge (especially if they are healthy and with a strong bone implantation).

• 

  complete dentures

  Chewing forces decrease if a dental restoration (crown, bridge, full denture) was previously manufactured on the opposite arch. In case of complete dentures, these forces are the lowest.

• Chewing forces are higher on the lower arch especially in the back part.

• If no teeth (and no restorations either) are present on the opposite arch, a dental restoration has to be designed for the opposite arch too. Otherwise, the chewing process will be severely affected.

• There are conditions that may lead to various occlusal problems : bruxismBruxism is the excessive grinding of the teeth and/or excessive clenching of the jaw, nervous disorders etc. The treatment of these conditions should be conducted before designing the bridge.

What is the normal conduct after examining the occlusion ?

If it is considered that additional forces will act on the bridge, the number of abutment teeth will be increased. If chewing forces will be normal or lower, the number of abutment teeth will remain the same (it will not be decreased).

The aesthetic and degree of destruction criterion

It is a simple criterion : when two teeth meet all abutment requirements, the following selection can still be made :

• The tooth with a more pronounced aesthetic position will remain unprepared (assuming that the tooth is healthy and not damaged or just minimally damaged).

• The tooth with a greater degree of damage (coronary destructions, large fillings, discoloration, enamel defects) will be prepared as abutment tooth.

Complete bridge

It is an unconventional name and refers to a bridge that reconstructs an entire dental arch. In these situations, all teeth from the arch are prepared as abutments.

complete porcelain bridge

Conceiving a reconstruction like this is an important process. Theoretically, a complete bridge can be designed using only 4 teeth as abutments, but they must be the first molars (left and right) and the two canines. However, the more prudent approach is to include more abutments.

Edentulism types that do not require dental restorations

There are situations when the absence of a tooth doesn't need a dental restoration:

• The absence of the third molar (wisdom tooth) : it has a negligible role in mastication
• The absence of the second molar : needs restoration only if the opposite second molar is present on the arch

!!! Do not confuse the necessity of replacing a tooth with the possibility of using the same tooth as abutment.

For example, if the third molar is missing, no restoration is needed. But the same tooth may be used as an abutment for dental bridges that restore other missing teeth.