A bridge is a non-removable restoration that replaces one or more lost teeth. It is supported completely periodontally by at least two pillar elements, which are wholly or partially grounded for this purpose. The bridge is manufactured in the laboratory, consisting of crowns for the pillars with the element part to be replaced fixedly attached (bridge intermediate part, pontic or dummy). This dummy can sit between two pillars or can only be attached to one pillar. In the latter case we speak of a bridge with a floating pontic. Depending on the number of parts that make up a bridge, there is a three, four or five-part bridge (see figure below).
Procedure for the manufacture of a bridge
The procedure for manufacturing a bridge is roughly the same as for a crown. We suffice here to indicate the deviations in the procedure.
- An emergency bridge is made as a temporary facility and no loose emergency crowns. This is intended to prevent the pillars from shifting in the mouth during the laboratory phase, which means that the definitive bridge will not fit. The emergency bridge can be made by making an alginate impression prior to preparation and after filling it up with self-polymerizing synthetic resin, also at the place of the dummy. It is also possible to first make individual customized confection emergency crowns on the pillars and then stick a dummy with thickly made synthetic resin in between (see image below). The bridge is made, but one of the pillars (molar) has been moved. The bridge no longer fits.
- Full prints of both jaws are made and the bite is recorded. If there is a stable occlusion, this can be done with the help of a wash bite. With extensive crown and bridge work it may be important to register the articulation in addition to the occlusion. This can be done by making proal and lateral wash bites and by using a face-bow. This type of bite registration allows the plaster models to be placed in a fully adjustable articulator. An articulator is a device with which one can reproduce the movement of the lower jaw relative to the skull and thus view the chewing movements of the patient. The technician can precisely adjust the shape of the crowns to the occlusion and articulation patterns of the patient (see figure below).
- In the case of extensive bridge work, the bridge is first fitted in bisquit.
- Sometimes a bridge is placed with temporary cement. After a week of carrying in, the bridge generally has a better connection to the pillars and the underlying mucosa of the pontic section.
- The pontic part is available in various designs. It can be tight against the mucosa, or away from it. The design can determine the expected food accumulation. The risk of food accumulation should be as low as possible in connection with caries and gum disease. In addition to the design of the pontic, this also depends on the oral hygiene of the patient. To clean under the pontic part, special bridge needles have been developed that can be placed under the pontic in combination with dental floss.
A bridge cannot have too large a span, due to the resistance to the chewing forces. If the span is too large with insufficient pillars, it is better to decide on a removable prosthesis. The advantage of a bridge over a removable prosthesis is that it is a permanent feature that is often experienced by the patient as more comfortable. A disadvantage is that bridge work entails high costs.
A special type of bridge is the etching or adhesive bridge. A dummy is made of baked porcelain on a metal substructure, with a wing-shaped extension of thin metal on either side. These metal plates are fixed to the palatal or lingual surfaces of the pillar elements with a special thin-liquid composite using the etching bonding method. The inside of the 'wings' is tinned in the dental laboratory. This gives a very good retention to the composite. The adhesion to the elements is less strong than with a conventional bridge, because the contact surface is smaller. This type of bridge is therefore mainly used in the upper and lower front to replace a single lost or not installed (agenetic) element.
The conditions for the etching bridge are that the pillar elements are not too weakened and that there is sufficient healthy enamel.
The etching bridge has the following advantages over the conventional bridge:
- The treatment is easier than with a conventional bridge.
- The costs are considerably lower.
- For an etching bridge, the pillar elements do not or hardly need to be ground.
An etching bridge is a semi-permanent solution with a more limited lifespan than a conventional bridge (see image below).