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Procedures

Fixed partial dentures

Procedure overview

Learn about the dental procedure, when it is generally prescribed, and other information which can increase your knowledge of the topic.

Alternate terms: Bridges; Dentures, fixed partial.

A fixed bridge, or simply "bridge" is also known as a fixed partial denture. The term "fixed" means it is cemented ("glued") to teeth, and is not intended to be removed by the patient. Fixed bridges are prescribed to replace one or more teeth, if the patient has enough remaining teeth that are strong enough to perform the functional demands of the missing teeth. Bridges can be made to look and feel very much like natural teeth.

X-ray image of three types of bridges (fixed partial dentures)

Figure 1: Three different types of bridges are shown in this panoramic radiograph. The bridge from tooth 4 to tooth 6 is a traditional three-unit bridge, supported on both ends with the pontic ("false tooth") in the center (5). Note that there are no tooth roots under 5, 10, 30 or 31. The bridge at 10-11 is called a "cantilever bridge", meaning it is only supported on one end. This avoided cutting tooth 9. There are very few places in the mouth where this can safely be done. Here, the pontic (10) is supported by a long-rooted canine tooth (11).

The patient in Figure 1 has no teeth behind tooth #11, so a bridge in that quadrant of the mouth wasn't an option. The bridge from tooth #29 to tooth #32 is a four-unit bridge with two pontics (#30 and #31). Dental implants and removable partial dentures might be treatment options for this patient for the remainder of the missing teeth, or if the existing bridgework fails at some point.
Learn more: Procedures › Dental implants
Learn more: Procedures › Removable dentures

It would also be possible to place a section of fixed bridgework from tooth #1 to tooth #4, if a T-slot has been incorporated into the retainer crown on tooth #4, with future additions to the bridge in mind (see Pier-Abutments under "Variations on Fixed Bridges" on this page).
Learn more: Glossary › Keyway

Making a bridge involves preparing the teeth that will hold the bridge ("abutment teeth") for "retainer" crowns. The path of insertion of the retainer crowns (or just "retainers") must be aligned so that the bridge can be inserted on the abutment teeth. The missing tooth or teeth (called "pontics" in dental terms) are fused to the retainer crowns, and occupy the position(s) where the missing tooth or teeth were removed from. Pontics are suspended above the gums where the missing teeth were removed. Hence the term, "bridge".
Learn more: Procedures › Crowns

Dental laboratory casts showing tooth preparations for fixed bridge abutments

Figure 2: A cast showing that tooth numbers 6 and 11 have been prepared for a fixed bridge by reducing them to tapered stubs. Tooth numbers 7 and 10 were also prepared, but were broken off of the cast in the process of fabricating the fixed bridge, accurately illustrating that those two teeth would not be strong enough to support two large pontics ("false teeth") between them. Teeth 8 and 9, the patient's two front teeth, are the missing teeth. Implants should be considered as a viable treatment alternative to a bridge in this case.

Inside view of metal free bridge, a cosmetic dentistry option for missing front teeth

Figure 3: The internal aspect of the bridge for the case above is shown in this view. Note how the retainers are merely hollowed out shells that will fit over the tapered abutment teeth. The pontics are made to gently rest on the gum tissue where the teeth have been removed. Note that they are not hollowed out. These pontics are of the "modifid ridge lap" variety (see "Questions").

An anterior bridge is one cosmetic dentistry option for missing front teeth

Figure 4: A photograph of how the fixed bridge will look when it is cemented (i.e. glued) to the abutment teeth in the patient's mouth.

Materials Options

Bridges can be fabricated from any of the following materials:

  • Your own tooth—If your tooth needs to be removed, it is sometimes possible to cut the root off of it, seal the resulting hole in the tooth with tooth colored filling material, and bond the (now rootless) tooth to the teeth on either side of it as a pontic (assuming the teeth adjacent to the missing tooth are not crowned). This can be done as a temporary measure, but long-term successes are possible with the technique, especially if the missing tooth is a front tooth.
  • Composite resin—One of the most commonly used filling materials in dentistry is composite resin. It can also be used to sculpt a fixed pontic the shade of your missing tooth, that is bonded to the natural teeth on either side of the space (again, assuming the teeth adjacent to the missing tooth are not crowned). This can be done as a temporary measure, but long-term successes are possible with the technique, especially if the missing tooth is a front tooth.
  • All-ceramic—Modern dental ceramics can be made using the same crystalline structure as tooth enamel (calcium hydroxyapatite). The result is a very esthetic fixed bridge. All-ceramic bridges, while beautiful, may not have the flexural strength to hold up in high stress areas of the mouth (e.g. back teeth).
  • Ceramic fused to metal—A good trade-off between flexural strength and esthetics can be achieved with ceramic fused to metal, especially if the metal used is zirconium. Zirconium is a white metal, and thus the porcelain that is fused to it does not have to be heavily opacified to hide the underlying metal. Opaque porcelain lacks the optical characteristics of natural tooth enamel because it does not transmit light the same. Nonetheless, for back teeth, porcelain fused to traditional metal alloys (e.g. gold) have highly acceptable esthetics, excellent strength, and may cost less than porcelain fused to zirconium.
  • Solid metal bridge alloys—Although they may not be desirable in visible areas of the mouth, metal bridges have advantages. They will not chip, and they require less tooth structure to be removed from the abutment teeth, possibly reducing the chance of an abscess. Metal alloys in common use include gold/platinum/palladium alloys (in various proportions); titanium alloys; and "base metal" alloys, having too little gold/platinum/palladium content to be considered "noble". Noble alloys form fewer corrosion byproducts in the mouth than base metal alloys. Base metal is more economical.
    Learn more: Glossary › Noble
  • Combinations—It is possible (and commonly done) to fabricate bridges in which the back retainer crown(s) is/are solid metal, and the teeth that are visible have porcelain baked onto the visible surfaces to mask the metal and provide reasonably good esthetics with excellent durability.

Variations on Fixed Bridges

1. Maryland Bridge

Dental photograph of cosmetic resin-bonded Maryland bridge to replace tooth 7

Figure 5a: Smile view of a "Maryland" bridge, also called a resin-bonded bridge. Maryland bridges are minimally invasive (tooth-sparing), economical, and can be functional and esthetically pleasing in appropriate applications.

Palatal (inside) view of resin-bonded Maryland bridge to replace tooth 7

Figure 5b: Note that the pontic ("false tooth" at arrow) is suspended between two teeth that have been very minimally prepared on their palatal sides (inside the mouth) only, to allow the retaining "wings" to be bonded to the tooth enamel where they are not visible. The retainers can be made of metal or ceramic. In this case, they were made of ceramic. This type of bridge requires a short gap between the adjacent teeth (i.e. the missing tooth is small) for greatest reliability. Like all bridges, it has the disadvantage of splinting teeth together, making access for hygiene a challenge. This can put the retainer abutment teeth at risk for decay. This patient was missing both of the upper lateral incisors from birth.

X-ray image of Maryland (resin bonded) bridge to replace tooth 7

Figure 5c: Note that the adjacent teeth have not been decayed or filled, a fact that would make cutting the teeth for a traditional bridge undesirable. Also note that there was insufficient room to place an implant between the adjacent tooth roots (see arrows) in this case. (The white circle in the lower right corner of the image is an orientation feature of the digital X-ray).

2. Cantilever Bridges

Dental (bitewing) X-ray shows cantilever bridge (fixed partial denture)

Figure 6: A cantilever bridge is shown (the pontic is obvious—no tooth root). This design prevents the tooth to the right of the space in this image (tooth #28) from having to be cut down. It also requires a very solid molar abutment (tooth #30, left of space), preferrably with large, diverging roots to prevent leverage on the pontic from breaking the abutment or dislodging the bridge. Cantilevering a pontic the other direction (so that the pontic is further back in the mouth than the abutment) is even more risky, because the chewing forces are much greater in the back of the mouth, and the teeth toward the front of the mouth have less structural ability to withstand the greater functional demands being placed by the pontic.

A general rule is that cantilevering a tooth backwards requires keeping the pontic smaller than normal. Frequently, the dentist who elects to place that type of bridge in the mouth will want to attach it to more than one forward tooth. That introduces access problems for maintaining good dental hygiene around the abutments. A dental implant may have been a nice option for the patient whose teeth are shown in this radiograph.

3. Pier-Abutments

Failing pier abutment from caries around core buildup in overloaded fixed bridge (denture)

Figure 7: A pier abutment is a tooth situated in the middle of a long span bridge (see arrow), with pontics (i.e. "false teeth") on both sides of it. In the bridge shown, there was a T-shaped slot (not visible in the X-ray) milled into the biting surface of the retainer crown on the pier abutment tooth, into which a matching T-shaped lug from the pontic behind it engages. This feature provides a hinged "stress breaker" connection between the front and back segments of the bridge, which are separate pieces.

The pier abutment in this patient failed (you can tell the tooth was badly compromised by the four pins that are evident in the radiograph), and both sections of the bridge had to be removed. When they were, the patient opted to replace the missing teeth with implants (shown in the radiograph below). This case illustrates how importance it is for a pier abutment to be a very solid tooth.

Bitewing X-ray showing dental implants and natural teeth with crowns

Figure 8: Removal of the patient's failing bridgework and replacement with implant supported crowns returned the patient to "single tooth" dentistry, meaning her teeth were no longer splinted together. This makes access for good dental hygiene much simpler, and if one tooth fails, it doesn't necessitate the replacement of any others.

Cleaning Under a Bridge

The teeth of a bridge are fused together, so you can't use floss to clean between them. There is a significant risk of developing tooth decay on the abutment teeth—on the side that faces the pontic—if you don't clean effectively under the bridge every day. These convenient hygiene aids can help you keep your bridge clean and are typically available at a drug or convenience store:

  • Floss Threader—This is a large plastic "needle" through which dental floss or dental tape is threaded. You can use the tip of the "needle" to pull the floss or tape under the bridge. Lightly buff the surfaces free of plaque.
  • Interdental Brush—These cone-shaped brushes come in different size, and can be easily adapted to make it easy to clean under your bridge. Make sure you clean the tooth/bridge interface (margins) effectively. This is where decay is most likely to occur.
  • Toothpick—Although they may not be as effective as floss threaders or interdental brushes, they are readily available, and are much better than neglecting to clean under your bridge.
  • Oral Irrigators—These are good at removing bulk food debris, but are largely ineffective at removing "biofilm", the filmy plaque that adheres to teeth and is loaded with bacteria.

If these devices are difficult to use, or if you have trouble finding them in a store, ask your dental professional for their recommendations.

Post-operative discomfort

A common misconception about teeth is that working on them, like trimming fingernails, should not lead to any complications. In reality, though, working on teeth is a surgical procedure. Teeth are very well-supplied with two different types of nerve tissue. And unlike other tissues of the body that are living, teeth can't swell, and are poorly equipped to deal with inflammation. Working on teeth very commonly produces inflammation—just as making an incision in an arm or leg would. Inflammation is a process by which your body sends immune cells and healing cells to the affected area so that they can repair the "wound". It does so by increasing blood flow to the affected region.

When the surgery is performed on soft tissue (i.e. skin, muscle), increased blood flow to the area produces swelling—enlargement of the soft tissues—which are somewhat elastic (i.e. "stretchy"). Since teeth cannot swell, inflammation causes the blood pressure inside the tooth to increase. The increased pressure on the nerves inside may produce significant discomfort. Well-maintained dental instrumentation, skilled technique, and use of desensitizing medications can minimize post-operative discomfort, but may not eliminate it.
Learn more: Diagnoses › Irreversible pulpitis
Learn more: Diagnoses › Reversible pulpitis

Anything that causes a pressure change inside an inflamed tooth can provoke more discomfort. The most common culprits are cold temperatures and chewing. Cold causes the fluid inside the tooth to contract (shrink), changing the pressure. Chewing sends small hydraulic compression waves through the extra fluid in the tooth, and these pulses are perceived as pain. Sensitivity to heat is a symptom in some cases, but generally heat sensitivity is less common. Severe sensitivity to heat is a sign that there may be gas in the tooth. This is an unfavorable situation, because the gas is usually produced by bacteria (i.e. the tooth is infected). Sometimes the only way to reduce the pressure in the tooth is to make a hole into the pulp space (i.e. perform a root canal).
Learn more: Diagnoses › Acute apical abscess

Some people are inclined to think something must have been done wrong if they experience discomfort after a dental procedure. Although this can be the case, if proper procedure is followed, it is more likely the tooth's reaction to what was done that causes the problem. Does this mean you should wait until your tooth hurts to fix a problem that has been diagnosed? Definitely not! Very often problems with teeth (i.e. cavities, etc.) don't hurt unless they are advanced. Waiting until the problem is advanced to fix it is a big mistake. The bigger the problem is, the harder it is to fix and the more likely it is to produce complications; and it will frequently have a poorer prognosis (likelihood of long-term success) if you wait too long to have a problem fixed.

If your dentist can show you the problem (e.g. on the X-ray, with a photo, etc.) in such a way that you have a clear understanding of what it is, how it can be fixed, with how much urgency it should be addressed, any options you may have for fixing it, the risks, and intended benefits of each, the likelihood of success ("prognosis") of each, and the cost of each, you will experience better treatment outcomes.